Prepared in cooperation with the U.S. Environmental Protection Agency

Characterization of Mercury Contamination 

in the Androscoggin River, Coos County, 

New Hampshire

Open-File Report 2013–1076

U.S. Department of the Interior

U.S. Geological Survey
THIS PAGE INTENTIONALLY LEFT BLANK
Characterization of Mercury Contamination 

in the Androscoggin River, Coos County, 

New Hampshire

By Ann T. Chalmers, Mark C. Marvin-DiPasquale, James R. Degnan, 

James F. Coles, Jennifer L. Agee, and Darryl Luce

Prepared in cooperation with the U.S. Environmental Protection Agency

Open-File Report 2013–1076

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation:

Chalmers, A.T., Marvin-DiPasquale, M.C., Degnan, J.R., Coles, J.F., Agee, J.L., and Luce, Darryl, 2013, Characterization 

of mercury contamination in the Androscoggin River, Coos County, New Hampshire: U.S. Geological Survey Open-File 

Report 2013–1076, 56 p., http://pubs.usgs.gov/of/2013/1076/.
iii

Acknowledgments

The authors would like to thank the many individuals that provided field and laboratory support 

for this project. Andrew Hoffman of the New Hampshire Department of Environmental Services 

(NHDES), Vivien Taylor of Dartmouth College, and Cornell Rosiu of the U.S. Environmental 

Protection Agency (USEPA) assisted with sediment collection; Chuck Dobroski of Avatar Environmental, Kenneth Munney of the U.S. Fish and Wildlife Service, and Stan Pauwels of the USEPA 

collected fish samples; David Buck of BioDiversity Research Institute collected bat samples; and 

Michael Ferrier, Erica Czerepak, and Bethany Kelley of USEPA Region 1 Environmental Services 

Assistance Team (ESAT) collected oligochaete, swallow, and toxicity samples and processed the 

surface and pore-water toxicity samples.

Thor Smith of the U.S. Geological Survey (USGS) assisted with surface-water, pore-water, and 

invertebrate sampling. Marc Zimmerman, Jon Denner, and Jamie Shanley of the USGS assisted 

with pore-water sample collection, and Evangelos Kakouros, Le Kieu, and Michelle Beyer of 

the USGS analyzed pore-water and sediment samples. Jeffrey Deacon of the USGS and Cornell 

Rosiu of the USEPA were instrumental in the study planning and design. The authors would also 

like to thank Chuck Dobroski and Jamie Shanley for their thoughtful technical reviews.
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v

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Site History and Previous Work..........................................................................................................2

Purpose and Scope ..............................................................................................................................2

Study Approach and Methods.....................................................................................................................3

Field Methods........................................................................................................................................4

Surface-Water Sampling............................................................................................................4

Sediment Pore-Water Sampling................................................................................................6

Streambed-Sediment Sampling ................................................................................................6

Toxicity Tests.................................................................................................................................6

Epifaunal Invertebrate Assemblages .......................................................................................7

Infaunal Invertebrate Tissue......................................................................................................7

White Sucker, Smallmouth Bass, and Crayfish.......................................................................7

Bats and Birds..............................................................................................................................7

Laboratory Methods.............................................................................................................................7

Total Mercury ...............................................................................................................................8

Methylmercury.............................................................................................................................8

Reactive Inorganic Mercury......................................................................................................8

Methylmercury Production Potential and Microbial Divalent-Mercury-Methylation 

Rate Constant..................................................................................................................8

Mercury Sequential Extraction .................................................................................................9

Iron Speciation.............................................................................................................................9

Total Reduced Sulfur...................................................................................................................9

Grain Size ....................................................................................................................................10

Dry Weight, Bulk Density, Porosity, and Organic Content ..................................................10

Total and Organic Carbon, Total Nitrogen, and Carbon and Nitrogen Isotopes..............10

Pore-Water Dissolved Organic Carbon..................................................................................10

Pore-Water Sulfate and Chloride............................................................................................10

Pore-Water Ferrous Iron ..........................................................................................................10

Data Analysis.......................................................................................................................................10

Results and Discussion...............................................................................................................................11

Mercury Speciation and Distribution ..............................................................................................11

Surface Water............................................................................................................................11

Sediment and Pore Water........................................................................................................11

Biota .........................................................................................................................................15

Mercury Bioavailability......................................................................................................................15

Controls on Mercury Distribution.....................................................................................................19

Controls on Divalent Mercury Availability for Methylation..........................................................23

Controls on Partitioning between Bed Sediment and Pore Water.............................................23

River-Reach Integrated Mercury Species Inventories and Methylmercury Production 

Potential Rates.......................................................................................................................25

Ecological Impact ...............................................................................................................................30

Comparison to Other Studies............................................................................................................33
vi

Summary and Conclusions.........................................................................................................................35

Selected References...................................................................................................................................35

Appendix 1. Quality Assurance and Control at the U.S. Geological Survey Laboratory in 

Menlo Park, California...................................................................................................................53

Appendix 2. Surface-Water, Pore-Water, Sediment, Invertebrate, and Biota Data......................55

Figures

1. Graph showing generalized locations of sediment and pore-water sampling sites on 

the Androscoggin River downstream from a former chloralkali facility in Berlin, 

New Hampshire ............................................................................................................................3

2. Map of study area on the Androscoggin River, Coos County, New Hampshire.................5

3. Boxplots showing concentrations of sediment A, total mercury (THg), B, methylmercury (MeHg), and C, percentage of THg as MeHg from the Androscoggin River, 

Coos County, New Hampshire..................................................................................................12

4. Boxplots showing concentrations of pore-water A, total mercury (pw.THg), B, methylmercury (pw.MeHg), and C, percentage of THg as MeHg (pw% MeHg) from the 

Androscoggin River, Coos County, New Hampshire.............................................................13

5. Boxplots showing concentrations of A, dissolved organic carbon (pw.DOC) and 

B, sediment loss on ignition (LOI) from the Androscoggin River, Coos County, 

New Hampshire ..........................................................................................................................14

6. Boxplots showing mercury partitioning coefficients from the Androscoggin River, 

Coos County, New Hampshire..................................................................................................16

7. Bar graph showing sequential extractions of surficial sediment in the Androscoggin 

River, Coos County, New Hampshire.......................................................................................17

8. Boxplots showing concentrations of total mercury (THg) in A, smallmouth bass and 

B, white sucker from the Androscoggin River, Coos County, New Hampshire................18

9. Boxplot showing concentrations of total mercury (THg) in smallmouth bass from the 

Androscoggin River....................................................................................................................19

10. Boxplots showing sediment mercury methylation potential from the Androscoggin 

River, Coos County, New Hampshire.......................................................................................20

11. Boxplots showing concentrations of A, pore-water sulfate ( pw.SO4

-2 ) and 

B, sediment total reduced sulfur (TRS) from the Androscoggin River, Coos County, 

New Hampshire ..........................................................................................................................21

12. Boxplots showing A, sediment grain size less than 63 micrometers (μm) and 

B, oxidation reduction potential (redox, Eh) from the Androscoggin River, Coos 

County, New Hampshire............................................................................................................22

13. Graphs showing predicted against measured sediment total mercury (THg) for 

A, near, B, far, and C, all stream reaches of the Androscoggin River, Coos County, 

New Hampshire ..........................................................................................................................24

14. Graph showing predicted against measured methylmercury (MeHg) from the 

Androscoggin River, Coos County, New Hampshire.............................................................25

15. Graphs showing predicted against measured sediment inorganic reactive mercury 

(Hg(II)R) for A, near, B, far, and C, all stream reaches of the Androscoggin River, 

Coos County, New Hampshire..................................................................................................26

16. Graphs showing predicted against measured mercury methylation potential (MPP) 

A, constant (kmeth) and B, rate for the Androscoggin River, Coos County, New 

Hampshire....................................................................................................................................27
vii

17. Graphs showing predicted against measured partitioning coefficient for A, total 

mercury (kd[THg]) and B, methylmercury (kd[MeHg]) for the Androscoggin River, 

Coos County, New Hampshire..................................................................................................28

18. Graph showing sediment total mercury partitioning coefficient as a function of 

dissolved organic carbon and grain size................................................................................29

19. Graph showing sediment methylmercury partitioning coefficient as a function of 

dissolved organic carbon and grain size................................................................................29

20. Bar graph showing New Hampshire Department of Environmental Services (NHDES) 

benthic index of biotic integrity (B–IBI) for the Androscoggin River, Coos County, 

New Hampshire ..........................................................................................................................32

Tables

1. Study sampling area description and dates for the Androscoggin River from 

Pontook Reservoir to Shelburne Dam, New Hampshire........................................................4

2. Summary of methods used for analysis of sediment, pore water, surface water, and 

biota from the Androscoggin River, Coos County, New Hampshire...................................42

3. Sequential extraction scheme applied to surface sediment samples from the 

Androscoggin River, Coos County, New Hampshire...............................................................9

4. Wilcoxon rank sum test comparing results upstream and downstream from a former 

chloralkali site on the Androscoggin River in Berlin, New Hampshire .............................45

5. Kruskal-Wallis rank sum test results comparing data grouped by sample distance 

from a former chloralkali site on the Androscoggin River in Berlin, New Hampshire....47

6. Sequential extraction results for surface sediment, Androscoggin River, Coos 

County, New Hampshire............................................................................................................49

7. Stream reach parameters used to calculate reach specific depth integrated 

mercury species inventories and rates ..................................................................................30

8. Depth-integrated mercury species inventories and rates, by river reach .......................31

9. Guidelines for total mercury in surface water, sediment, and fish and methylmercury 

in surface water..........................................................................................................................34

10. Comparison of mercury concentrations in the Androscoggin River, Coos County, 

New Hampshire, with National Water-Quality Assessment Program and 

Northeastern Ecosystem Research Cooperative datasets .................................................34
viii

Conversion Factors and Datum

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

meter (m) 1.094 yard (yd)

Area

square meter (m2

) 0.0002471 acre

square meter (m2

) 10.76 square foot (ft2)

square centimeter (cm2

) 0.1550 square inch (ft2)

square kilometer (km2

) 0.3861 square mile (mi2)

Mass

kilogram (kg) 2.205 pound avoirdupois (lb)

Hydraulic gradient

meter per kilometer (m/km) 5.27983 foot per mile (ft/mi)

In this report, the words right and left refer to directions that would be reported by an observer 

facing downstream.

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in water are either in milligrams per liter (mg/L), 

micrograms per liter (μg/L), nanograms per liter (ng/L), moles per liter (M), or millimoles per liter 

(mmol/L).
Characterization of Mercury Contamination in the 

Androscoggin River, Coos County, New Hampshire

By Ann T. Chalmers1, Mark C. Marvin-DiPasquale1, James R. Degnan1, James F. Coles1, Jennifer L. Agee1, and 

Darryl Luce2

Abstract

The former chloralkali facility in Berlin, New 

Hampshire, was designated a Superfund site in 2005. Historic paper mill activities resulted in the contamination of 

groundwater, surface water, and sediments with many organic 

compounds and mercury (Hg). Hg continues to seep into 

the Androscoggin River in elemental form through bedrock 

fractures. The objective of this study was to spatially characterize (1) the extent of Hg contamination in water, sediment, 

and biota; (2) Hg speciation and methylmercury (MeHg) 

production potential rates in sediment; (3) the availability of 

inorganic divalent Hg (Hg(II)) for Hg(II)-methylation (MeHg 

production); and (4) ancillary sediment geochemistry necessary to better understand Hg speciation and MeHg production 

potential rates in this system.

Concentrations of total mercury (THg) and MeHg in 

sediment, pore water, and biota in the Androscoggin River 

were elevated downstream from the former chloralkali 

facility compared with those upstream from reference 

sites. Sequential extraction of surface sediment showed a 

distinct difference in Hg speciation upstream compared with 

downstream from the contamination site. An upstream site 

was dominated by potassium hydroxide-extractable forms 

(for example, organic-Hg or particle-bound Hg(II)), whereas 

sites downstream from the point source were dominated by 

more chemically recalcitrant forms (largely concentrated 

nitric acid-extractable), indicative of elemental mercury or 

mercurous chloride. At all sites, only a minor fraction (less 

than 0.1 percent) of THg existed in chemically labile forms 

(for example, water extractable or weak acid extractable). All 

metrics indicated that a greater percentage of mercury at an 

upstream site was available for Hg(II)-methylation compared 

with sites downstream from the point source, but the absolute 

concentration of bioavailable Hg(II) was greater downstream 

from the point source. In addition, the concentration of tinreducible inorganic reactive mercury, a surrogate measure 

of bioavailable Hg(II) generally increased with distance 

downstream from the point source. Whereas concentrations 

of mercury species on a sediment-dry-weight basis generally 

reflected the relative location of the sample to the point source, 

river-reach integrated mercury-species inventories and MeHg 

production potential (MPP) rates reflected the amount of finegrained sediment in a given reach.

THg concentrations in biota were significantly higher 

downstream from the point source compared with upstream 

reference sites for smallmouth bass, white sucker, crayfish, 

oligochaetes, bat fur, nestling tree swallow blood and feathers, 

adult tree swallow blood, and tree swallow eggs. As with 

tin-reducible inorganic reactive mercury, THg in smallmouth 

bass also increased with distance downstream from the point 

source. Toxicity tests and invertebrate community assessments 

suggested that invertebrates were not impaired at the current 

(2009 and 2010) levels of mercury contamination downstream 

from the point source. Concentrations of THg and MeHg in 

most water and sediment samples from the Androscoggin 

River were below U.S. Environmental Protection Agency 

(USEPA), the Canadian Council of Ministers of the 

Environment, and probable effects level guidelines. Surfacewater and sediment samples from the Androscoggin River had 

similar THg concentrations but lower MeHg concentrations 

compared with other rivers in the region. Concentrations 

of THg in fish tissue were all above regional and U.S. 

Environmental Protection Agency guidelines. Moreover, 

median THg concentrations in smallmouth bass from the 

Androscoggin River were significantly higher than those 

reported in regional surveys of river and streams nationwide 

and in the Northeastern United States and Canada. The 

higher concentrations of mercury in smallmouth bass suggest 

conditions may be more favorable for Hg(II)-methylation and 

bioaccumulation in the Androscoggin River compared with 

many other rivers in the United States and Canada.

1

U.S. Geological Survey.

2

U.S. Environmental Protection Agency.
2 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Introduction

During operation of the chloralkali facility in Berlin, 

New Hampshire, elemental mercury (Hg0

) was spilled 

contaminating the overburden and underlying fractured 

rock on the east (left) bank of the Androscoggin River. Hg0

is relatively nontoxic; the primary pathway of Hg0

 toxicity 

in the environment begins with the oxidation to inorganic 

divalent mercury (Hg(II)) in the presence of chloride, thiol 

compounds, and oxygen. In low salinity waters such as those 

of the Androscoggin River, Hg0

 oxidation is quite slow, and 

formation of oxidation products on the surface of the liquid 

further reduces oxidation rates (Amyot and others, 2005). The 

conversion of Hg(II) to more bioavailable methylmercury 

(MeHg) is a process that is largely carried out by anaerobic 

bacteria near the sediment-water interface (Gilmour and 

others, 1992). Rates of net benthic MeHg production in 

the sediments are controlled by the activity of the Hg(II)-

methylating microbial community and by Hg(II) availability 

to microbes (Marvin-DiPasquale and others, 2009a). 

Environmental factors that affect the activity of communities 

of Hg(II)-methylating bacteria include temperature, pH, and 

presence of suitable electron acceptors and donors. Availability 

of Hg(II) to microbes is controlled by total mercury (THg) 

concentration, dissolved organic carbon (DOC), sediment 

grain size, and calcium, iron, and sulfur solid-phase mineral 

chemistry. Understanding the Hg(II) processes and the 

environments that are conducive to methylation will provide 

key information for remedial actions and decisions.

Site History and Previous Work

In September 2005, Congress added the former chloralkali facility in Berlin, N.H., to the national priorities list, 

commonly known as the Superfund list (U.S. Environmental 

Protection Agency, 2005). Investigations onsite have revealed 

elevated mercury, lead, arsenic, polycyclic aromatic hydrocarbons, organochlorine chemicals (dioxin and furans, polychlorinated biphenyls), and other toxic metals in groundwater and 

soils (Darryl Luce, U.S. Environmental Protection Agency 

(USEPA), written commun., 2008). The mercury contamination originates from two longstanding point sources across 

from one another on the Androscoggin River in Berlin, N.H. A 

chloralkali facility that produced chlorine gas for the papermaking industry using electrolytic diaphragm cells operated 

from the late 1800s through the 1960s (Margaret Bastien, New 

Hampshire Department of Environmental Services (NHDES), 

written commun., 2004). How mercury was used at the facility is uncertain. Mercury may have been used in the cells to 

separate chlorine from a brine solution. The second source of 

mercury was from a sawmill that used mercuric chloride wood 

preserving process known as kyanization. Kyanization was 

used by the sawmill from 1888 through 1930 (Weston 

Solutions, 2005). The mercuric chloride may have been 

prepared at the chloralkali facility and then transported across 

the river for use at the kyanization plant. Regardless of use, 

the main release of mercury to the environment was at the 

chloralkali facility on the left bank of the Androscoggin River, 

just downstream from Sawmill Dam (fig. 1). The total amount 

of mercury released from the facility that seeped into the overburden and into the underlying fractured bedrock is unknown 

(Degnan and others, 2005). Efforts to contain the mercury at 

the chloralkali site and eliminate seepage to the river include 

demolition of the cell houses, installation of a bentonite-soil 

slurry barrier wall on the site perimeter, and pressure grouting 

the bedrock along the riverbank (Margaret Bastien, NHDES, 

written commun., 2003). Despite earlier actions to address 

the source of contamination, mercury continues to seep into 

the Androscoggin River through fractures in the bedrock at 

the edge of the site (Darryl Luce, USEPA, written commun., 

2008). Mercury has also been found in the sediment of the 

adjacent Androscoggin River from sampling conducted by the 

former site owners and the NHDES (Darryl Luce, USEPA, 

written commun., 2008). THg concentrations (average plus 

or minus standard deviation) in sediments collected at dam 

impoundments by the NHDES (Lori Siegel, NHDES, written 

commun., 2004) were highly variable, from 75 ±177 nanograms per gram (ng/g) at Sawmill Dam (upstream from 

the facility) to 361 ±483 ng/g at Riverside Dam and 

354 ±277 ng/g at Smith Hydro Dam (both downstream from 

the facility). MeHg concentrations in sediments collected by 

the NHDES were lowest at Sawmill Dam (0.071 ±0.082 ng/g) 

and higher at Smith Hydro Dam (1.00 ±0.79 ng/g) and 

Riverside Dam (1.28 ±2.16 ng/g). Subsequently, further investigation into the extent of mercury contamination and transformation processes within the Androscoggin River was deemed 

warranted by the USEPA to determine the potential impacts on 

the environment and to provide a more comprehensive understanding of mercury dynamics in this system to guide potential 

remediation activities. To that end, the USEPA funded a study 

conducted by the U.S. Geological Survey (USGS) from 2009 

through 2012 to provide more detailed information regarding 

the extent of mercury contamination and speciation within the 

Androscoggin River. The major objectives of this study were 

to characterize the extent of mercury contamination in sediment, water, and biota of the Androscoggin River and to assess 

mercury speciation and the potential availability of in-situ 

mercury for Hg(II)-methylation. 

Purpose and Scope

This report (1) compares surface-water, pore-water, sediment, and biota THg and MeHg concentrations upstream and 

downstream from a former chloralkali facility; (2) evaluates 

the potential for Hg(II)-methylation and mercury bioaccumulation; (3) explains differences in MeHg production rates and 

bioavailable Hg(II) patterns among sites using nonparametric 

rank sum tests and best-fit linear model equations; (4) assesses 

the health of the aquatic ecosystem surrounding the former 

chloralkali facility using a variety of surface-water, sediment, 
Study Approach and Methods 3

Elevation, in meters

Distance, in kilometers

200 

220 

240 

260 

280 

300 

320 

340 

0 5 10 15 20 

AR 5

AR 7

AR 4

AR 6

AR 8

AR 9

Sawmill Dam

Riverside Dam

Smith Hydro Dam

Cross Power Dam

Cascade Dam

Brown Dam

Gorham Dam

Shelburne Dam

Former chloralkali facility

Near stream reaches Far stream reaches

Figure 1. Generalized locations of sediment and pore-water sampling sites on the 

Androscoggin River downstream from a former chloralkali facility in Berlin, New Hampshire. 

Stream reaches are signified by AR followed by number. The reference reach (AR2) is 

16 kilometers upstream from the former chloralkali facility and is not shown. Sampling 

locations are indicated by red circles, dams are indicated by black squares. Elevation and 

distance data from Google Earth, February 17, 2012.

and biological indices and guidelines; and (5) compares THg 

and MeHg concentrations in water, sediment, and biota from 

the study site to concentrations reported in other river systems 

nationally and regionally in the Northeastern United States 

and Canada. 

In addition, this report also summarizes concurrent biomonitoring data collected by BioDiversity Research Institute 

(Gorham, Maine) and Avatar Environmental (West Chester, 

Pennsylvania) contracted by the USEPA for the purposes of 

providing additional context regarding the human health and 

ecological impacts of mercury within the study area.

Study Approach and Methods

The study area encompasses a 40-kilometer (km) reach 

of the Androscoggin River from Pontook Reservoir to just 

upstream from Shelburne Dam, including the former chloralkali facility site in Berlin (table 1, fig. 2). Individual river 

reaches (coded as AR followed by the number of the reach#) 

were defined by the presence of dam structures at the upper 

and lower boundary of each reach. The precise coordinates 

for all sampling locations are listed in table 2–1. Pontook 

Reservoir (AR1) and Wheeler Bay (within the upper portion of 

AR2), both upstream from the facility, were used as reference 

sites of background (nonpoint-source) conditions. AR1 was 

used as a reference site for birds and bats, whereas AR2 was a 

reference site for sediment, pore water, surface water, epifaunal invertebrates, crayfish, and birds. Seven stream reaches, 

from the facility (within AR3) to just upstream from Shelburne 

Dam (AR9), were sampled to characterize the mercury contamination downstream from the point source.

THg and MeHg concentrations were analyzed in surface 

water, pore water, and sediment and THg in macroinvertebrates, crayfish, fish, bats, and birds (tables 1, A2–1). The 

potential for Hg(II)-methylation and MeHg bioaccumulation 

was assessed by a number of different metrics. The percentage 

of THg as MeHg (percent MeHg) in sediment was used as a 

proxy for Hg(II)-methylation efficiency. Tin-reducible reactive 

inorganic mercury (Hg(II)R) was used as a surrogate for the 

pool of inorganic Hg(II) readily available to sediment bacteria 

for Hg(II)-methylation. This methodologically defined assay 

measures simple Hg(II)-salts, such as mercury sulfate and mercury chloride, 

Hg(II) bound to low molecular weight organic 

ligands, and Hg(II) weakly adsorbed to particle surfaces 

(Marvin-DiPasquale and others, 2006; Marvin-DiPasquale, 
4 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Table 1. Study sampling area description and dates for the Androscoggin River from Pontook Reservoir to Shelburne Dam, 

New Hampshire.

[Epifaunal invertebrates were collected in rock baskets]

Reach 

code Reach description Sampling dates Sample types

AR1 Above Pontook Dam 2010 Bat, bird

AR2 Pontook Dam to Wheeler Bay 2009, 2010, 2011 Sediment, pore-water, surface-water, epifaunal invertebrate, oligochaetes, crayfish, fish, bird

AR3 Sawmill Dam to Riverside Dam 2009, 2010 Surface-water, epifaunal invertebrate, crayfish, fish, bird

AR4 Riverside Dam to Smith Hydro Dam 2009, 2010 Sediment, pore-water, surface-water, epifaunal invertebrate, oligochaetes, crayfish, fish, bird

AR5 Smith Hydro Dam to Cross Power Dam 2010, 2011 Sediment, pore-water, oligochaetes, crayfish, fish

AR6 Cross Power Dam to Cascade Dam 2009, 2010, 2011 Sediment, pore-water, oligochaetes, crayfish, fish

AR7 Cascade Dam to Brown Dam 2010, 2011 Sediment, pore-water, oligochaetes, crayfish, fish

AR8 Brown Dam to Gorham Dam 2009, 2010 Sediment, pore-water, surface-water, epifaunal invertebrate, oligochaetes, crayfish, fish, bird

AR9 Gorham Dam to Shelburne Dam 2009, 2010 Sediment, pore-water, surface-water, epifaunal invertebrate, oligochaetes, crayfish, fish, bat, bird

unpub. data). Microbial MeHg production potential (MPP) 

rates were measured in sediment using 200Hg(II) stable isotope 

incubations to measure the microbial rate constant for Hg(II)-

methylation (kmeth) and calculated based on kmeth and the independently measured Hg(II)R concentration (Marvin-DiPasquale 

and others, 2008). Another approach used to assess mercury 

availability was a five-step sequential extraction (Bloom and 

others, 2003) that chemically characterizes the THg pool 

from most labile (water-extractable) to most refractory (aqua 

regia-extractable). Site-specific differences in MPP rates were 

examined in terms of a suite of environmental factors, such 

as sediment redox conditions, particle size, sulfur and iron 

chemistry, and organic content in sediment, all of which can 

affect both the activity of Hg(II)-methylating bacteria and the 

availability of Hg(II) to those bacteria.

The potential biological impact of the mercury contamination in the study area was assessed by the community 

composition of epifaunal macroinvertebrate assemblages 

and toxicity testing of surface waters, pore waters, and bulk 

sediment. Surface-water, sediment, and biological indices and 

guidelines were also used to evaluate the potential ecological 

impact of the mercury contamination within the study area.

Field Methods

Field sampling was performed during 3 years (table 1). 

Samples were collected from a wide range of media during 

August and September 2009, including surface water, 

sediment pore water, whole sediment, fish, crayfish, epifaunal 

invertebrates, and infaunal invertebrates. Surface-water, 

sediment pore-water, and whole-sediment samples were 

collected by the USGS, fish and crayfish were collected 

by Avatar Environmental, and epifaunal invertebrates and 

infaunal invertebrates were collected by USGS and USEPA 

Region 1 Environmental Services Assistance Team (ESAT). 

During August 2010, USGS field sampling focused on 

mercury speciation and Hg(II)-methylation in sediment 

and on ancillary sediment parameters associated with 

carbon, iron, and sulfur. Additional biological sampling was 

conducted during 2010 and 2011 by BioDiversity Research 

Institute, ESAT, and the USEPA and included fish, infaunal 

invertebrates, bats, and marsh birds.

Surface-Water Sampling

Surface-water samples were collected during low 

streamflow conditions (average daily flow of 1,620 cubic 

feet per second) in September 2009 using multiple sampling 

points, based on standard USGS protocols (U.S. Geological 

Survey, 2005), and were processed using trace-metal clean 

techniques (Olson and DeWild, 1999). At wadeable sections 

of the river, samples were collected with a hand-held teflon 

depth integrating sampler (DH–81). At nonwadeable sections, 

samples were collected using an isokinetic sampler (D–95; 

equipped with a teflon nozzle and a teflon bottle) that was 

lowered from bridges using a reel and cable. Specific conductance, pH, dissolved oxygen, and water temperature were 

determined during the collection of surface-water samples 

using a multiprobe sonde (YSI 600XL). Samples were filtered 

using 0.45-micrometer (μm) high-capacity capsule filters. 

Both dissolved (filter passing) and total (nonfiltered) surfacewater samples were collected during 2009; THg and MeHg 
Study Approach and Methods 5

Gorham Dam

Sawmill Dam

Cascade Dam

Shelburne Dam

Riverside Dam

Smith Hydro Dam

Twelfth Street Bridge

Pontook Reservoir Dam

Gorham Brown Dam 

Wheeler Bay

Cross Power Dam

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UV110B

UV110

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UV16

Main St

French Hill Rd

Success Rd

Cates Hill Rd

Hill Rd

Hogan Rd

York Pond Rd

dR reviR fO tsaE

Success Loop Rd

Cascade Flats Rd

East Side River Rd Stearns Brook Rd

Gorham Rd

Chandler Ledges Rd

Cates Hill Ext

£¤2

UV16

Former Chlor-Alkali Site

Moose R iver

Androscoggin River

Moose Brook

Rattle River

Pea Brook

Perkins Brook

Peabody River

Austin

Clement Brook

Peabody Broo

L

k

e admine Brook

Dr yad Brook

Gates Brook

Carlton Brook

Snyder Brook

Kidder Brook

Bumpus Brook

Andros coggin River Chickwolnepy Stream

Alder Brook

Bean Brook

Dead River

Lea vitt Stream

Hor ne Brook

Ste arns Brook

Jericho Brook

Tinker Brook

Red Brook

South Branch Stear

North Branch Stea

North Branch Horne Bro

South Branch Horne Brook

Robbi ns Brook

Cascade Alpine Brook

Pond Brook

M i l a n

B e rli n

S u c c e s s

G o r h a m

S h e l b u r n e

D u m m e r 

C a m b r i d g e

R a n d o l p h

Base map prepared by AVATAR Environmental, LLC.

EXPLANATION

Reach Designations

AR1

AR2

AR3

AR4

AR5

AR6

AR7

AR8

AR9

2,000 0 2,000 4,000 6,000 8,000

Scale in Feet

μ

Figure 2. Map of study area on the Androscoggin River, Coos County, New Hampshire. Stream reaches 

are signified by AR followed by number. Pore-water and sediment sampling sites are black squares (2009) 

and red stars (2010). Base map prepared by AVATAR Environmental LCC.
6 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

samples were preserved with hydrochloric acid to a pH of less 

than 2, total recoverable metals (antimony, arsenic, beryllium, 

cadmium, chromium, copper, lead, nickel, selenium, strontium, vanadium, and zinc) samples were preserved with nitric 

acid to a pH of less than 2, and organic carbon samples were 

preserved with sulfuric acid to a pH of less than 2. All samples 

were kept chilled in coolers with wet ice and then refrigerated 

upon return to the laboratory.

Sediment Pore-Water Sampling

Pore-water samples were collected in depositional areas 

of the stream channel, typically along the channel margins. 

Pore-water samples were obtained in-situ during low streamflow conditions during September 2009 and August 2010 

using a push-point sampler as described in Zimmerman and 

others (2005) and were processed using trace-metal clean 

techniques (Olson and DeWild, 1999). A push-point sampler 

is designed to sample pore water with minimal disturbance 

to the sediment matrix. Specific conductance was used to 

monitor chemical differences between surface water and pore 

water during sampling and to verify that surface water was not 

drawn down into the pore-water sampling zone.

Other field parameters measured with the YSI 600XL 

multiprobe sonde included pH, dissolved oxygen, oxidationreduction (redox) potential (ORP), and water temperature. 

ORP was measured with a platinum band electrode. Porewater samples were collected at depths between 7 and 

15 centimeters (cm) below the interface between the sediment 

and surface water using a peristaltic pump with teflon tubing. 

In-line filtration with 0.45-μm high-capacity capsule filters 

was used during 2009, and 0.4-μm precombusted quartz-fiber 

filters in teflon filter assemblies were used during 2010. Both 

dissolved (filter passing) and nonfiltered pore-water samples 

collected during 2009 were preserved for THg and MeHg 

(pw.THg and pw.MeHg), total recoverable metals (antimony, 

arsenic, beryllium, cadmium, chromium, copper, lead, nickel, 

selenium, strontium, vanadium, and zinc), and dissolved 

organic carbon (pw.DOC), as described above for surface 

water. All samples collected during 2010 were filtered and 

preserved immediately upon collection as follows: pw.THg 

and pw.MeHg with 6 moles per liter (M) hydrochloric acid 

(1 percent final concentration), ferrous iron (pw.Fe(II)) with 

10 percent hydrochloric acid (2 percent final concentration), 

pw.DOC with phosphoric acid to a pH less than 2, and porewater sulfate (pw.SO4

) was frozen.

Streambed-Sediment Sampling

Streambed-sediment samples were collected from 

undisturbed, continuously wetted, depositional zones in the 

stream channel that coincided with pore-water sampling 

locations (table 2–1). Samples collected during 2009 were 

composites of 5 to 10 representative subsamples over a 5- to 

10-square meter (m2

) area of relatively homogeneous sediment 

(Shelton and Capel, 1994). The upper 0- to 10-cm-depth 

interval of streambed sediment was sampled with a hand-held 

glass coring device, except at water depth greater than 1 meter 

(m) where an Eckman dredge was used. Samples collected for 

THg and MeHg were frozen onsite, whereas all other sediment 

samples were kept chilled on wet ice.

Streambed-sediment samples were collected during 2010 

from one or two sediment cores (0- to 10-cm depth) per site 

as described in Lutz and others (2008). To better document 

spatial variability, both on a small scale around each site as 

well as on a larger scale between stream reaches, two to three 

primary sites per reach were sampled (for a total of 15 primary 

sites), plus three additional field replicate sediment samples 

collected within 10 to 50 m from each primary site (for a 

total of 45 field replicate sites; table 2–1). For each sampling 

location (primary and field replicate; total of 60 sampling 

sites), sediment was composited in a ziplock bag and kept cold 

and dark on wet ice in a cooler until further processed and 

subsampled (within 8 hours of sample collection). Sediment 

sample processing included homogenizing, subsampling, and 

preserving as appropriate for each analyte. Sediment ORP 

and pH were measured by standard electrochemical probe 

techniques (Marvin-DiPasquale and Agee, 2003). Incubations 

associated with benthic MPP rates were initiated within 

8 hours of sample collection, as described below. Subsamples 

collected for organic content (as percent loss on ignition 

(percent LOI)), grain size less than 63 μm (percent fines), 

porosity, dry weight, and bulk density were stored chilled on 

wet ice. All other subsamples were frozen.

Toxicity Tests

Surface-water and pore-water toxicity tests were 

conducted by the USEPA Region 1 ESAT of North 

Chelmsford, Massachusetts. Surface water (10–12 liters 

(L)) was collected for chronic, 7-day bioassays with larval 

fathead minnow (Pimephales promelas) and the cladoceran 

(Ceriodaphnia dubia) using survival, growth, and reproductive 

criteria (U.S. Environmental Protection Agency, 2008a, b). 

At least 1 L of pore water was collected at each site, which 

was used for acute, 96-hour survival bioassays conducted 

using the freshwater amphipod (Hyalella Azteca) and the 

larval midge (Chironomus tentans), as described by the 

U.S. Environmental Protection Agency (2001a). Detailed 

methods of pore-water and surface-water toxicity testing 

are described by Environmental Services Assistance Team 

(2009a, 2009b, respectively). Whole-sediment toxicity tests 

were run by EnviroSystems, Inc., of Hampton, N.H. Sediment 

samples were collected at locations coincident with porewater samples and were used for bulk sediment toxicity tests 

with the Hyallela azteca (28-day exposure) and Chironomus 

dilutus (20-day exposure) using survival- and growth-based 

criteria as described by EnviroSystems, Inc., (2010a, 2010b, 

respectively). All surface-water, pore-water, and bulksediment samples collected for toxicity tests were kept chilled 

on wet ice or refrigerated until use in the above bioassays.
Study Approach and Methods 7

Epifaunal Invertebrate Assemblages

Epifaunal invertebrate samples were collected following 

NHDES benthic index of biotic integrity (B–IBI) protocols 

(New Hampshire Department of Environmental Services, 

2004). Rock baskets (16.5 cm × 28 cm) containing 3.8- to 

7.6-cm-diameter gravel were placed in riffle habitats upstream 

from water-chemistry sampling sites at water depths deep 

enough to maintain continuous flow over the artificial substrate. Four baskets per site were anchored to the streambed 

by sections of steel reinforcing rod (rebar) that were approximately 1.2 m long and 19 millimeters (mm) in diameter. Invertebrate samples collected from three of the four rock baskets 

were used to evaluate the aquatic ecosystem health, which is 

based on the presence of certain taxa and the abundance of 

organisms at the sampling sites. The organisms collected from 

the fourth rock basket at each site were combined in a single 

sample that was analyzed for THg. The rock baskets were 

deployed August 6–7, 2009, and retrieved 6.5 weeks later 

(September 21–22, 2009).

Rock baskets were retrieved by placing a 500-mesh 

D-frame net downstream from the rock basket and gently 

lifting and sliding the rock basket into the net. Rock baskets 

were emptied into 500-μm sieve buckets. The empty basket 

cages were gently scrubbed and rinsed into 5-gallon pails, 

and the contents were poured into the sieve bucket. Rocks in 

the sieve buckets were gently brushed and rinsed to remove 

organisms and detritus and returned to basket cage. Leaves 

and detritus in the sieve bucket were rinsed, inspected for 

organisms, and returned to the stream. The contents of the 

sieve bucket were transferred to jars and preserved with 

70-percent ethanol. Samples for tissue chemistry were 

thoroughly rinsed with site water, placed in glass jars, and 

frozen for subsequent analysis of THg using a Milestone 

direct mercury analyzer (DMA) at the USEPA laboratory in 

Chelmsford, Mass. Invertebrate assemblage samples were 

processed according to NHDES B–IBI protocols (New 

Hampshire Department of Environmental Services, 2004) with 

a 300-organism count and identified to genus and species level 

by Lotic, Inc., of Unity, Maine.

Infaunal Invertebrate Tissue

Infaunal worms (Oligochaeta spp.) were collected from 

the top 15 cm of sediment in the same locations as the porewater and sediment samples. A minimum of 5 grams (g) of 

infaunal worms were washed of external sediment and debris, 

placed in glass jars, and frozen. Tissue samples were analyzed 

for THg using a DMA at the U.S. Department of Energy 

National Renewable Energy Laboratory in North Chelmsford 

(Nobis Engineering, 2009).

White Sucker, Smallmouth Bass, and Crayfish

Fish samples were collected by Avatar Environmental 

using electroshocking during August 2009 and by the U.S. 

Fish and Wildlife Service, the USEPA, and ESAT using rod 

and reel and gill nets during August 2011 (Nobis Engineering, 

2009). Two whole-body composite samples of white sucker 

(Catostomus commersoni) were collected at three stream 

reaches during 2009 (table 1). Composite white sucker 

samples consisted of two to five fish. During 2011, individual 

whole-body samples of white sucker were collected at four 

stream reaches. Smallmouth bass (Micropterus dolomieui) of 

25- to 38-cm length were collected in 2009 and greater than 

25-cm length during 2011. Smallmouth bass samples were 

five individual skinless fillets of at least 5 g. All fish samples 

were rinsed with deionized water, wrapped in plastic wrap, 

placed in ziplock bags, and frozen. Crayfish were collected 

by trapping or electroshocking. Two composites of 5 to 10 

whole crayfish (more than 100 g wet weight) were collected 

at each site during August 2009, and 10 individual whole 

crayfish were collected at each site during August 2011 (Nobis 

Engineering, 2009). Crayfish were rinsed with deionized 

water, placed in a ziploc bag, and immediately chilled on 

wet ice.

Bats and Birds

Blood and fur from little brown bats (Myotis lucifugus) 

and big brown bats (Eptesicus fuscus) were sampled by 

BioDiversity Research Institute at the AR1 reference site 

(Pontook Reservoir) and downstream at AR9. Bats were 

collected using mist nets as described by Buck and Evers 

(2011). Tree swallows (Tachycineta bicolor) were sampled 

by ESAT at the two reference locations (Pontook Reservoir 

(AR1) and Wheeler Bay (AR2)) and four downstream stream 

reaches (AR3, AR4, AR8, and AR9). Blood, eggs, and feathers 

of adult and nestling tree swallows were collected as described 

in the Ecological Investigation Quality Assurance Project plan 

(Nobis Engineering, 2011).

Laboratory Methods

The laboratory methods detailed below were conducted 

by the USGS Branch of Regional Research, Western Region 

(USGS BRR–WR) Laboratory in Menlo Park, California, and 

were associated with the streambed-sediment and pore-water 

samples collected during 2010 only. These methods reflect the 

key parameters discussed in detail in this report. These and all 

other laboratory methods are summarized in table 2 (in back 

of report).
8 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Total Mercury

THg analysis was conducted on all 60 streambedsediment samples collected during 2010. Samples were 

stored frozen until analysis. After thawing, sediment THg 

was first extracted overnight in concentrated acid (aqua 

regia; concentrated nitric acid (HNO3

) plus hydrochloric 

acid (HCl) at a 1:3 ratio), followed by the addition of the 

oxidant bromine monochloride (BrCl) and heating overnight 

at 60 degrees Celsius (°C) to ensure all the mercury was 

in the divalent inorganic form (Hg(II)) in accordance with 

standard USGS protocol (Olund and others, 2004). THg in 

the extract was assayed by cold vapor atomic fluorescence 

spectrometry (CVAFS) using a Tekran 2006 automated total 

mercury analyzer in accordance with USEPA method 1631 

(U.S. Environmental Protection Agency, 2001b, 2002). Further 

details on the method are described in Marvin-DiPasquale 

and others (2011). Each batch of analytical samples was 

accompanied by the analysis of the following minimum 

number of quality assurance (QA) samples: one certified 

reference material, one matrix spike, one analytical duplicate, 

one field duplicate, one method blank, and calibration 

standards prepared from commercially certified mercuric 

chloride (HgCl2

) solution.

Pore-water samples collected for pw.THg analysis 

were preserved in the field with a final concentration of 

0.5-percent HCl and stored refrigerated in the dark until 

further processing. Subsequently, the samples were initially 

oxidized with BrCl and similarly analyzed by CVAFS 

using a Tekran 2600 automated total mercury analyzer 

in accordance with USEPA method (U.S. Environmental 

Protection Agency, 2001b, 2002). Each batch of analytical 

samples was accompanied by the analysis of the following 

minimum number of QA samples: one matrix spike, one 

analytical duplicate, one field duplicate, one method blank, 

and calibration standards prepared from commercially certified 

HgCl2

 solution. For sediment and pore water, the detection 

limit for the THg assay is approximately 0.5 nanogram 

per liter (ng/L) at the level of the autoanalyzer. QA results 

for sediment and pore-water THg assays are detailed in 

appendix 1.

Methylmercury

MeHg analysis was conducted on the 15 primary streambed-sediment samples collected during 2010. Samples were 

stored frozen until analysis. After thawing, sediment MeHg 

was first extracted with a solution of 25-percent potassium 

hydroxide (KOH) in methanol at 60 °C for 4 hours (Xianchao 

and others, 2005). Quantification of MeHg in the extract was 

then carried out after ethylation of the analyte using a Brooks 

Rand Labs automated MeHg analyzer (MERX). Further 

method details are described in Marvin-DiPasquale and others 

(2011). Each batch of analytical samples was accompanied by 

the analysis of the following minimum number of QA samples: one certified reference material, one matrix spike, one 

analytical duplicate, one field duplicate, one method blank, 

and calibration standards prepared from commercial crystalline methylmercury chloride (MeHgCl) and compared with a 

separate, commercially available MeHg standard solution.

Pore-water samples collected for pw.MeHg analysis 

were preserved in the field with a final concentration of 

0.5 percent HCl and stored refrigerated in the dark until 

further processing. Subsequently samples were distilled (U.S. 

Environmental Protection Agency, 2001b) and then quantified 

after ethylation of the analyte using a MERX (MarvinDiPasquale and others, 2011).The detection limit for the 

MeHg assay is approximately 0.5 picogram (pg; absolute mass 

as mercury). QA results for sediment and pore-water MeHg 

assays are detailed in appendix 1.

Reactive Inorganic Mercury

Hg(II)R analysis was conducted on all 60 streambedsediment samples collected during 2010. Sediment Hg(II)R is 

methodologically defined as the fraction of total Hg(II) that 

is readily reduced to Hg0

 by an excess of tin chloride (SnCl2) 

over an exposure time of 15 minutes. Further method details 

are described in Marvin-DiPasquale and Cox (2007). Sediment 

subsamples for Hg(II)R were stored frozen until analysis. Each 

batch of analytical samples was accompanied by the analysis of the following minimum number of QA samples: one 

analytical duplicate, one field duplicate, four bubbler blanks, 

and calibration standards prepared from a commercial HgCl2

stock solution. No commercially available certified reference 

material exists for Hg(II)R in sediment. The detection limit for 

the Hg(II)R assay is approximately 40 pg (absolute mass). QA 

results are detailed in appendix 1.

Methylmercury Production Potential and 

Microbial Divalent-Mercury-Methylation Rate 

Constant

MPP rates were assessed for the 15 primary streambedsediment samples collected during 2010. Bulk sediment 

MPP rates were quantified using a stable isotope incubation 

approach (Marvin-DiPasquale and others, 2011). Incubations 

were initiated 4 to 8 days after initial field collection of the 

sediment. Three subsamples of sediment (3.0 g wet weight) 

per site were transferred into 13-cubic centimeter (cm3

) 

sealed serum vials under anaerobic conditions (nitrogen gas 

(N2

)-flushed glove bag). An isotopically enriched solution 

(0.1 milliliter (mL)) of mercury chloride (200HgCl2

) was then 

injected through the sepum of each vial for a final amendment 

concentration of 38 nanograms (ng) of isotopic mercury 

(200Hg(II)) per gram of sediment (wet weight). The samples 

were vortexed for 1 minute each immediately following the 

isotope amendment. One sample per set was immediately 

flash frozen in a bath of dry ice and ethanol. This sample 

represented the killed control. The remaining two samples per 

set were incubated at 20 °C for 5 hours, after which they too 
Study Approach and Methods 9

were flash frozen in dry ice and ethanol and stored at -80 °C 

until further processing, which consisted of extraction with 

25-percent KOH in methanol and quantification by isotopedilution inductively coupled plasma mass spectrometry (ICP–

MS; Marvin-DiPasquale and others, 2011).

Pseudo-first-order rate constants for 200Hg(II)-methylation 

(kmeth, units = 1/done per day) were then calculated from the 

incubated samples as described for the radiotracer 203Hg(II)-

methylation assay in Marvin-DiPasquale and others (2008).

Daily MPP rates (in ng/g dry sediment per day) were 

calculated as:

MPP = Hg(II) Hg(II) × exp -k × R R − ( ) ( ) meth t , (1)

where

t is the time during which methylation occurred 

(for the purposes of this rate, 1 day); and

Hg(II)R is the independently measured in-situ 

concentration of inorganic reactive 

mercury, in ng/g dry weight.

QA consisted of killed controls, analytical duplicates for every 

site, and the use of internal standards (that is, isotopically 

enriched MeHg (Me199Hg)).

Mercury Sequential Extraction

THg sequential extraction analysis was conducted on 

the 15 primary streambed-sediment samples collected during 

2010. Sediment sequential extraction followed the fivefraction (F1 thru F5) scheme detailed in Bloom and others 

(2003) and Marvin-DiPasquale and others (2011) with each 

successive fraction using a stronger extraction solution (from 

deionized water to aqua regia) to dissolve mercury in the 

sediment sample. The specific extraction solutions and typical 

mercury species extracted with them are detailed in table 3. 

The starting sample mass extracted was 3 ±0.2 g wet weight 

with the exact weight (±0.001 g) noted. Each extraction step 

was conducted overnight for a minimum of 12 hours. The 

analysis of THg on each extraction fraction was conducted as 

described above for pore water. For QA, 3 of the 15 samples 

were run in duplicate, as were reagent blanks for all extractants. The relative percent difference (mean plus or minus 

standard error) for analytical duplicates associated with the 

five fractions were as follows (number of samples in each case 

equals three): F1 = 21 ±16 percent, F2 = 30 ±6 percent, F3 = 

7.5 ±3.9 percent, F4 = 22 ±14 percent, and F5 = 9.6 ±5.3 percent. No certified reference material is commercially available 

for these method-defined sequential extraction fractions.

Iron Speciation

Iron speciation analysis was conducted on the 15 primary 

streambed-sediment samples collected during 2010. Samples 

were stored frozen until analysis. Three forms of sediment 

iron were assayed: acid-extractable ferrous iron (Fe(II)AE), 

amorphous (poorly crystalline) ferric iron (Fe(III)a

), and 

crystalline ferric iron (Fe(III)c

). Method details are described 

in Marvin-DiPasquale and others (2008). The typical detection 

limit for each iron fraction is approximately 0.01 milligram 

per milliliter (mg/mL) at the level of the spectrophotometric 

analysis. Each batch of analytical samples was accompanied 

by the analysis of the following minimum number of QA 

samples: one analytical duplicate, one field duplicate, one 

matrix spike for Fe(II)AE and Fe(III)c

 fractions only, one 

method blank, and ferrous sulfate (FeSO4

) calibration 

standards prepared from analytical-grade crystalline reagents. 

No certified reference material is commercially available for 

these method-defined iron species. QA results are detailed in 

appendix 1.

Total Reduced Sulfur

Total reduced sulfur (TRS) analysis was conducted on 

the 15 primary streambed-sediment samples collected during 2010. Samples were stored frozen until analysis. After 

Table 3. Sequential extraction scheme applied to surface sediment samples from the Androscoggin River, Coos County, 

New Hampshire.

[The mercury sequential extraction sequence (Bloom and others, 2003) with each fraction number (F#) is described by the extraction solution used and the 

dominant mercury species associated with that fraction. DI, deionized; Hg, mercury; HgCl2, mercuric chloride; HgSO4, mercuric sulfate; M, moles per liter; 

HCl, hydrochloric acid; HgO, mercuric oxide; KOH, potassium hydroxide; Hg(II), inorganic divalent mercury; MeHg, methylmercury; Hg2Cl2, mercurous 

chloride; HNO3, nitric acid; Hg0, elemental mercury; HgS, cinnabar; m-HgS, metacinnabar; HgAu, mercury gold amalgam]

F# Extraction Dominant mercury species

F1 DI water Soluble, HgCl2

, HgSO4

F2 pH = 2; 0.1 M acetic acid plus 0.01 M HCl HgO, HgSO4

F3 1 M KOH Organic or particle bound Hg(II), MeHg, Hg2Cl2

F4 12 M HNO3 Elemental Hg0, Hg2Cl2

F5 Aqua regia (concentrated HNO3 and HCl at 1:3 ratio) HgS, m-HgS, HgAu
10 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

thawing, sediment TRS was extracted by a single-step hot acid 

chromium reduction approach and quantified spectrophotometrically (Marvin-DiPasquale and others, 2008). Each batch 

of analytical samples was accompanied by the analysis of the 

following minimum number of QA samples: one analytical 

duplicate, one field duplicate, one method blank, and zinc 

sulfide (ZnS) calibration standards. No certified reference 

material is commercially available for the TRS assay. The 

detection limit for this assay is approximately 0.2 micromole 

per milliliter (μmol/mL) at the level of the spectrophotometric 

analysis. QA results are detailed in appendix 1.

Grain Size

Grain-size analysis was conducted on all 60 streambedsediment samples collected during 2010. Samples were stored 

refrigerated until analysis. Sediment percent fines was assayed 

as the weight percentage of dry sediment less than 63 micrometers (less than 63 μm, the sand/silt split) and was conducted 

by wet sieving (Matthes and others, 1992). Each batch of 

analytical samples was accompanied by the analysis of the 

following minimum number of QA samples: one analytical 

duplicate and onefield duplicate. No certified reference material is commercially available for the grain size analysis. QA 

results are detailed in appendix 1.

Dry Weight, Bulk Density, Porosity, and Organic 

Content

Analysis of bulk density, dry weight, porosity, and 

organic content (as percent LOI) was conducted on all 

60 streambed-sediment samples collected during 2010. 

Samples were stored refrigerated until analysis. These four 

sediment parameters were analyzed consecutively from 

single sediment subsamples, as previously detailed (MarvinDiPasquale and others, 2008). Each batch of analytical 

samples was accompanied by the analysis of the following 

minimum number of QA samples: one analytical duplicate at 

all sites and one field duplicate. No certified reference material 

is commercially available for this suite of sediment analyses. 

QA results are detailed in appendix 1 (table 1–3).

Total and Organic Carbon, Total Nitrogen, and 

Carbon and Nitrogen Isotopes

Analysis of total carbon (TC), total organic carbon 

(TOC), and total nitrogen (TN), with associated isotopes (δ13C 

and δ15N, respectively), was conducted on all 60 streambedsediment samples collected during 2010. Samples were stored 

frozen until analysis. Analysis was conducted as described 

in Kendall and others (2001) using a Carlo Erba model 1500 

elemental analyzer connected to an Elementar Isoprime mass 

spectrometer before and after acidification (HCl acid fuming overnight to remove inorganic carbon). Each batch of 

analytical samples was accompanied by the analysis of the 

following minimum number of QA samples: one analytical 

duplicate, one field duplicate, and calibration standards prepared from ethylene-diamine-tetra-acetic acid. QA results for 

TC and TN are detailed in appendix 1.

Pore-Water Dissolved Organic Carbon

Analysis of pw.DOC was conducted on pore water 

collected from the 15 primary streambed sites sampled during 

2010. Samples were stored refrigerated and acidified (to a 

pH of less than 2) until analysis. Analysis for pw.DOC was 

conducted using high temperature combustion and infrared 

(IR) detection on a Shimadzu Scientific Instruments TOC–

VCPH total organic carbon analyzer. QA measures included 

analytical duplicates, field duplicates, calibration standards, 

method blanks, and reagent blanks. QA results are detailed in 

appendix 1.

Pore-Water Sulfate and Chloride

Analysis of pw.SO4 and pore-water chloride (pw.Cl) 

was conducted on pore water collected from the 15 primary 

streambed sites sampled during 2010. Samples were stored 

frozen until analysis and assayed by ion chromatography as 

described in Marvin-DiPasquale and others (2008). QA measures included analytical duplicates, field duplicates, calibration standards, method blanks, and reagent blanks. QA results 

are detailed in appendix 1.

Pore-Water Ferrous Iron

Analysis of pw.Fe(II) was conducted on pore water collected from the 15 primary streambed sites sampled during 

2010. Samples were stored refrigerated and acidified (to a pH 

of less than 2) until analysis and assayed by the colorimetric 

ferrozine assay as described in Marvin-DiPasquale and others 

(2008). QA measures included analytical duplicates, field 

duplicates, calibration standards, method blanks, and reagent 

blanks. QA results are detailed in appendix 1.

Data Analysis

Statistical analysis was performed using the TICBO 

Sptofire S+, version 8.1 software. Type II error probability 

(p) was set at less than 0.05 for all statistical tests, unless 

otherwise noted. We generally report median and interquartile 

range (IQR) data throughout the Results and Discussion section because the two-sided Kolmogorov-Smirnov goodnessof-fit test indicated that a majority (more than 60 percent) 

of the parameters measured in this study were not normally 

distributed. For data below the reporting limit, medians and 

IQRs were calculated using maximum likelihood estimation 

(Helsel, 2005) subroutines developed by the USGS for the 
Results and Discussion 11

S+ statistical platform. The mercury distribution in sediment, 

pore water, and biota was analyzed by comparing grouped 

medians from samples collected downstream from the former 

chloralkali facility to the reference sites using the nonparametric Wilcoxon rank sum (WRS) test. Downstream stream 

reaches were split into two spatial groupings determined by 

stream gradient: near-stream reaches (AR3 (fish only), AR4, 

AR5, and AR6), 0 to 4 km downstream from the point source 

in an area of steep stream gradients, and far-stream reaches 

(AR7, AR8, and AR9), 8 to 16 km downstream from the 

point source where stream gradients were much more gradual 

(fig. 1). Grouped medians of samples collected from reference, 

near, and far-stream reaches were compared using the nonparametric Kruskal-Wallis rank sum (KWRS) test. If KWRS 

indicated a significant difference between groupings, Tukey 

multiple-comparison test was used to determine which medians differed significantly.

Starting with multiple (four to seven) explanatory variables, best-fit linear model equations were developed using 

step-wise linear regression to describe the spatial variability in 

key mercury metrics. Prior to model development, parameters 

that were not normally distributed were log-base 10 (log10)-

transformed and used in the model. Explanatory variables 

(independent or x variables) with type II error p more than 0.1 

were removed from the regression equations; all overall model 

fits required p less than 0.05 as a testing criterion.

Results and Discussion

Samples from various matrices were collected to (1) 

define areas of mercury contamination, (2) better understand 

factors controlling MeHg production and bioaccumulation, 

and (3) assess the ecological impact of the mercury 

contamination. Tabular results of all physical parameters 

measured and chemical analysis conducted on surface water, 

pore water, sediment, invertebrates, fish, bats, and birds are 

listed in tables A2–2 through 2–22. Sediment and pore-water 

analyses included in this report are only of depositional areas, 

not the entire stream channel. The results from the statistical 

(nonparametric WRS) assessment of sediment, pore water, 

toxicity tests, and select biota data, comparing the reference 

reaches (AR1 and AR2) to all stream reaches downstream 

from the former chloralkali plant, are summarized in table 4 

(in back of report).

The results from the statistical (nonparametric KWRS) 

assessment of sediment, pore water, toxicity tests, and select 

biota data, comparing the reference reach (AR2) with near 

downstream stream reaches (AR3, AR4, AR5, and AR6) and 

with far downstream stream reaches (AR7, AR8, and AR9), 

are summarized in table 5 (in back of report). Ancillary 

parameters that showed no significant differences among the 

spatial groupings were not included in tables 4 or 5 (in back 

of report); these parameters included sediment TC, TN, carbon 

to nitrogen ratio (C:N), TOC, percent LOI, TRS, Fe(II)AE, 

Fe(III)a

, Fe(III)c, carbon 13 (13C) and nitrogen 15 (15N) 

isotopes, and pore-water parameters pw.Fe(II), pw.SO4

, and 

pw.DOC. The lack of significant spatial differences generally 

reflected the limited range of parameter concentrations in the 

study area.

Mercury Speciation and Distribution

THg and MeHg concentrations in surface water, sediment, pore water, and biota were compared downstream 

from the former chloralkali facility relative to reference sites. 

Sequential extraction of surface sediment was used to assess 

differences in mercury speciation upstream and downstream 

from the facility.

Surface Water

The number (n) of observations associated with the 2009 

surface-water samples was too small (n=5) for statistical 

evaluation of the spatial groupings used for sediment. 

However, visual inspection of the data (table 2–2) showed 

little difference among the various stream reaches sampled 

for filtered THg (range from 0.70 to 1.00 ng/L, mean of 

0.87 ng/L), nonfiltered THg (range from 0.44 to 2.17 ng/L, 

mean of 1.13 ng/L), filtered MeHg (all less than 0.1 ng/L), 

nonfiltered MeHg (all less than 0.1 ng/L), and 1M KOHextractable Hg(II) (all less than 0.08 ng/L). This observed 

limited variability between surface-water samples collected 

around a point source in a high-gradient stream is not 

surprising because of the short hydrologic residence time.

Sediment and Pore Water

Sediment THg and MeHg concentrations were 

significantly higher downstream from the point source than 

at the reference site (table 4, in back of report). The highest 

median sediment THg and MeHg concentrations were in 

stream reach AR5, 2.5 km downstream from the point source 

(figs. 3A and B). No significant difference existed between 

near- and far-stream reaches, suggesting that sediment THg 

and MeHg concentrations were not decreasing downstream 

from the point source as far as Shelburne Dam, and could 

possibly continue at elevated levels downstream from 

Shelburne Dam (table 5, in back of report). 

Whereas pw.MeHg concentrations were significantly 

higher downstream from the point source than at the reference site, pw.THg concentrations were not (table 4, in back 

of report). The highest pw.THg and pw.MeHg concentrations 

were in stream reach AR4, 2 km downstream from the point 

source (figs. 4A and B). Samples from AR4 were collected 

in a depositional area in and around a dense stand of aquatic 

emergent vegetation. The median pw.DOC concentrations at 

this location were also three times higher than other stream 

reaches (fig. 5). The elevated pw.DOC concentrations at AR4 

may facilitate the desorption of organic and inorganic mercury 
12 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire EXPLANATION 75th Median percentile 25th percentile

MaximumMinimum

[8] Number of observations

Stream reach 

AR2 AR4 AR5 AR6 AR7 AR8 AR9

Stream reach 

AR2 AR4 AR5 AR6 AR7 AR8 AR9

1.51.00.50.0

0

200400600

Percentage of THg as MeHg

2.01.51.00.50.0

MeHg , in ng/g dw 

/g dw g THg, in n

Stream reach 

AR2 AR4 AR5 AR6 AR7 AR8 AR9

[2] 

[2] 

[3] 

[2] 

[3] 

[2] 

[3] 

[8] 

[8] 

[9] [8] [9] 

[8] 

[12] 

[2] 

[2] 

[2] 

[5] 

[4] 

[7]

Reference Near reaches Far reaches Reference Near reaches Far reaches

Reference Near reaches Far reaches

A. Sediment total mercury

B. Sediment methylmercury 

C. Sediment percent methylmercury

TEL guideline

Figure 3. Concentrations of sediment 

A, total mercury (THg), 

B, methylmercury (MeHg), and 

C, percentage of THg as MeHg from the Androscoggin River, Coos County, New Hampshire. Samples were collected in 2009 and 2010. Samples from the reference reach (AR2) are from 

16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from nearstream reaches (AR4–AR6) are from 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–AR9) are from 8 to 16 km downstream from the former chloralkali facility. THg and MeHg nondetect data are excluded from the plot because of high detection levels. The dashed blue line indicates the median reference (AR2) sediment concentration, and the dashed red line indicates the threshold effects level (TEL) concentration of 180 nanograms per gram (ng/g; MacDonald and others, 2000). dw, dry weight.
Results and Discussion 13

[2]

[2] 

[2] 

[3] 

[4] 

[4] 

[2] 

[2] 

[2] [2] 

[3] 

[3] 

[4] 

[2] 

[3] 

[2] [4] 

[5] 

[7] 

[2] 

[2]

50

1510

pw.THg, in ng/L 

Stream reach

AR2 AR4 AR5 AR6 AR7 AR8 AR9

0

40302010

pw% MeHg

Stream reach

AR2 AR4 AR5 AR6 AR7 AR8 AR9

AR2 AR4 AR5 AR6 AR7 AR8 AR9

2.52.01.51.00.50.0

pw.MeHg, in ng/L 

Stream reach

Reference Near reaches Far reaches 

A. Pore-water total mercury

Reference Near reaches Far reaches

B. Pore-water methylmercury

C. Pore-water percentile methylmercury

Reference Near reaches Far reaches EXPLANATION

75th Median

percentile

25th percentile

MaximumMinimum

[2] Number of observations

Figure 4. Concentrations of pore-water A, total mercury (pw.THg), B, methylmercury 

(pw.MeHg), and C, percentage of THg as MeHg (pw% MeHg) from the Androscoggin River, Coos County, New Hampshire. Samples were collected in 2009 and 2010. Samples from the reference reach (AR2) are from 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–AR6) are from 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–AR9) are 8 to 16 km downstream from the former chloralkali facility. Total mercury nondetect data are excluded from the plot because of high detection level. The dashed blue line indicates the median reference (AR2) pore-water concentration. ng/L, nanograms per liter.
14 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire Stream reach AR2 AR4 AR5 AR6 AR7 AR8 AR9 Stream reach AR2 AR4 AR5 AR6 AR7 AR8 AR9

50

1510

 in % dw I, LO

0

5040302010

pw.DOC, in mg/L 

EXPLANATION

75th Median

percentile

25th percentile

MaximumMinimum

[8] Number of observations

[8]

[2] 

[3] 

[2] 

[5] 

[7] 

[2] 

[5] [8] 

[8] 

[8] 

[12] 

 [8] 

[8] 

B. Sediment loss on ignition

Reference Near reaches Far reaches

A. Pore-water dissolved organic carbon

Reference Near reaches Far reaches

Figure 5. Concentrations of 

A, dissolved organic carbon (pw.DOC) and 

B, sediment loss on ignition (LOI) from the Androscoggin River, Coos County, New 

Hampshire. Samples were collected in 2009 and 2010 for pw.DOC and in 2010 for LOI. Samples from the reference reach (AR2) are from 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–AR6) are from 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–AR9) are from 8 to 16 km downstream from the former chloralkali facility. Dashed blue line is median reference (AR2) porewater (DOC) and sediment (LOI) concentration. dw, dry weight; mg/L, milligrams per liter; %, percent.
Results and Discussion 15

species off particles and into the pore water dissolved phase 

(Hill and others, 2009; Dong and others, 2010). The lower 

sediment partitioning coefficients (Kd

s

) at AR4 confirmed 

that THg and MeHg partitioned into the dissolved phase to a 

greater extent in this particular reach compared with all other 

stream reaches (figs. 6A and B). 

The distribution of mercury species as identified in 

surficial-sediment sequential extractions was also significantly 

different between the reference site and downstream from the 

point source (tables 4, 6, in back of report). Concentrations 

of the three refractory fractions (F3, F4 and F5; table 3) were 

all significantly higher downstream from the point source, 

compared with the reference site. The highest concentration 

of 12M HNO3

-extractable mercury (F4 fraction typified by 

Hg0

 or mercurous chloride (Hg2Cl2)) was found at AR4, the 

first reach downstream from the point source. At all sites, only 

a minor percentage (less than 0.1 percent) of THg existed 

in chemically labile forms (fractions F1 and F2; table 3). 

The relative composition of mercury species also changed 

downstream from the point source. The reference site had 

greater than 86 percent of THg in the KOH fraction, consistent 

with organic or particle bound Hg(II) (table 3), whereas 

downstream from the point source, the percentage of the F4 

fraction increased dramatically (fig. 7). As much as 86 percent 

of the THg was found in this F4 fraction in stream reach AR4.

No significant change in mercury species distribution was 

noted between near and far-stream reaches (table 5, in back of 

report), suggesting the elevated levels of refractory mercury 

species (potentially Hg0

 or Hg2Cl2) continues at least as far as 

Shelburne Dam.

Biota

THg concentrations in smallmouth bass, white sucker, 

crayfish, oligochaetes, bat fur, nestling tree swallow blood and 

feathers, adult tree swallow blood, and tree swallow eggs were 

all significantly higher downstream from the point source than 

at the reference sites (table 4, in back of report). Far-stream 

reaches had significantly higher smallmouth bass and white 

sucker THg concentrations than near-stream reaches (fig. 8; 

table 5, in back of report). Median THg concentrations in bat 

blood and adult swallow feathers were higher downstream 

from the point source than the reference site, but the difference was not significant. The highest THg concentrations in 

epifaunal macroinvertebrates were found in the stream reach 

adjacent to the point source (AR3); however, the sample size 

(n=5) was too small to conduct a statistical spatial comparison 

(table 2–16).

Smallmouth bass THg concentrations from this study 

were also compared with smallmouth bass fillet concentrations 

collected from the Androscoggin River between Rumford 

and Lisbon, Maine, (80–180 km downstream from the study 

area) by the Maine Department of Environmental Protection 

from 2000 to 2009 as part of the Surface Water Ambient Toxic 

Monitoring Program (Maine Department of Environmental 

Protection, 2009). Grouped medians from reference, near, far, 

and Maine stream reaches were compared using nonparameteric KWRS test. Smallmouth bass THg concentrations from 

Maine were significantly higher than the New Hampshire 

reference site in Wheeler Bay (AR2) and similar to far-stream 

reaches (AR7–AR9) between Gorham and Shelburne, suggesting elevated THg levels in smallmouth bass continue downstream from the study area (fig. 9).

Mercury Bioavailability

The potential for Hg(II)-methylation was evaluated using 

a number of different metrics including the percentage of THg 

as MeHg (percent MeHg) in sediment, tin-reducible inorganic 

mercury (Hg(II)R), stable isotope200Hg(II)-methylation rate 

incubations to derive kmeth, MPP rates calculated from independently measured kmeth and Hg(II)R data, and THg sequential 

extraction. Selective sequential extractions measured how 

readily mercury was leached from sediment; more readily 

leached organic bound mercury species are presumably more 

bioavailable for Hg(II)-methylation than the more refractory 

(strong acid soluble) compounds. All metrics indicated that 

mercury was relatively more available for Hg(II)-methylation 

at the reference site than downstream from the point source. 

The sediment percent Hg(II)R was significantly higher at 

the reference site than downstream from the point source 

(fig. 10B; table 4, in back of report). The median percent 

MeHg in sediment was highest at the reference site (fig. 3C); 

however, the difference was not significant, most likely due to 

the limited number of samples from the reference site (table 4, 

in back of report). Sequential extraction results indicated 

that a significantly higher percentage of THg was associated 

with the F3 fraction (KOH soluble, indicative of organic or 

particle bound mercury) at the reference site, whereas sites 

downstream from the point source had a significantly higher 

percentage of refractory forms (F4 and F5 fractions; fig. 7; 

table 4, in back of report).

Although the proportion of mercury readily available 

for Hg(II)-methylation appeared greater at the reference 

site compared with stream reaches downstream from the 

point source, the absolute concentration of Hg(II) readily 

available for Hg(II)-methylation and the extent of mercury 

bioaccumulation in biota was greater downstream from 

the point source. Sediment Hg(II)R concentrations were 

significantly higher downstream from the point source than at 

the reference site, as were THg concentrations in smallmouth 

bass, white sucker, crayfish, oligochaetes, bat fur, and swallow 

feathers, blood, and eggs (figs. 10A, 8A and B; table 4, in 

back of report). Sequential extractions of surficial sediment 

also indicated significantly higher concentrations of organic 

or particle bound mercury (F3 fraction) downstream from 

the point source compared with the reference site (table 4, in 

back of report). Median values for MPP and kmeth were also 

higher downstream from the point source compared with the 

reference site, but the difference was not significant most 

likely due to the small number of observations (n=2) at the 
16 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire 3.6 3.1 2.6 2.1 5.2 4.7 4.2 3.7 3.2 Stream reach AR2 AR4 AR5 AR6 AR7 AR8 AR9 Stream reach AR2 AR4 AR5 AR6 AR7 AR8 AR9

(MeHg)), in L/kg d (k 10 log

(THg)), in L/kg d (k 10 log

[2]

[2] [2] 

[2] 

[2] 

[2] 

[3] 

[2]

[2] [2] 

[2] 

[2] 

[2] 

[3] 

Reference Near reaches Far reaches

A. Log-transformed partitioning coefficient total mercury in sediment 

Reference Near reaches Far reaches

B. Log-transformed partitioning coefficient for methylmercury in sediment

EXPLANATION

MMedian

aximum

Minimum

[8] Number of observations

Figure 6.

Mercury partitioning coefficients from the Androscoggin River, Coos County, New Hampshire. Samples were collected in 2010. Samples from the 

reference reach (AR2) are from 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–AR6) are from 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–AR9) are from 8 to 16 km downstream from the former chloralkali facility. Dashed blue line is median reference (AR2) partitioning coefficient for total mercury (kd(THg)), and partitioning coefficient for 

d(MeHg)). L/kg, liters per kilogram; log10, base-10 logarithm. methylmercury (k
Results and Discussion 17

0

10

20

30

40

50

60

70

80

90

100

AR2-4

AR2-5

 AR4-1

AR4-2

 AR5-1

AR5-2

AR6-2

 AR6-3

 AR7-1

 AR7-2

AR8-4

AR8-5

 AR9-5

AR9-6

AR9-7

Fraction

F5 Aqua regia; dominant species are HgS, m-HgS, and HgAu

F2—0.1 M acetic acid; dominant species are HgO and HgSO4

F3—1 M KOH; dominant species are organic or particle-bound

 Hg(II), MeHg, and Hg Cl 2 2

F4— 3 12 M HNO ; dominant species are Hg and Hg Cl 0

2 2

F1—Water; soluble; dominant species are H gCl 2 and HgSO4

EXPLANATION

% of THg

—

Figure 7. Sequential extractions of surficial sediment in the Androscoggin River, Coos County, New 

Hampshire. The mercury sequential extraction sequence (Bloom and others, 2003) shows each fraction 

number (F#) described by both the extraction solution used and the dominant mercury species associated 

with that fraction. AR, Androscoggin River, shows reach and site number (for example, AR2–4 is reach 

2, site 4); Hg0

, elemental mercury; Hg(II), divalent inorganic mercury; HgAu, mercury and gold amalgam; 

HgCl2

, mercuric chloride; Hg2Cl2, mercurous chloride; HgO, mercuric oxide; HgS, cinnabar; HgSO4, 

mercuric sulfate; HNO3

, nitric acid; KOH, potassium hydroxide; M, moles per liter; MeHg, methylmercury; 

m-HgS, metacinnabar; % of THg, percentage of total mercury as fraction number (F#).
18 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire EXPLANATION 75th Median percentile 25th percentile

MaximumMinimum

[5] Number of observations

THg, in ng/g ww 

Stream reach 

AR2 AR3 AR4 AR5 AR6 AR7 AR8 AR9 

0 

100 200 300 400 

THg, in ng/g ww 

Stream reach 

AR2 AR3 AR4 AR5 AR6 AR7 AR8 AR9 

100 300 500 700 900

1,100

eating mammals guideline

Human health guideline

Reference Near reaches Far reaches

Human health guideline

A. Smallmouth bass total mercury B. White sucker total mercury

Reference Near reaches Far reaches

Fish

[5]

N.D. N.D. 

[5] 

[5] 

[7] 

[2] 

[2] 

[5] 

[1] 

[5] 

[5] 

[10] 

[10] 

[7] 

[5] 

Figure 8. Concentrations of total mercury (THg) in 

A, smallmouth bass and 

B, white sucker from the Androscoggin River, Coos County, New Hampshire. 

Smallmouth bass samples are skin-off fillets; white sucker samples are whole fish. Samples were collected in 2009 and 2011. Stream reaches are signified by AR followed by number. The dashed blue line is the median reference (AR2) fish tissue concentration. The dashed red line is U.S. Environmental Protection Agency (2001, 2010) human health guideline for concentration of methylmercury (MeHg; less than 95 percent of THg), which in fish is 140 nanograms per gram (ng/g). The purple dashed line is the fish-eating mammal (otter) guideline concentration of 79 ng/g (Sample and others, 1996). N.D., no data were collected from stream reach; ng/g, nanograms per gram; ww, wet weight.
Results and Discussion 19

[10] 

[21] 

[17] [14] 

Human health guideline

Reference Near reaches Far reaches Maine

EXPLANATION

Median

75th percentile

25th percentile

Maximum

Minimum

[10] Number of observations

THg, in ng/g ww 

100

300 

500 

700 

900 

1,100

1,300

B AB A A 

Stream reach

Figure 9. Concentrations of total mercury (THg) in smallmouth bass from the Androscoggin River. The 

reference reach is 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H., near-stream 

reaches are 0 to 4 km downstream from the former chloralkali facility, far-stream reaches are 8 to 16 km 

downstream from the former chloralkali facility in Gorham and Shelburne, N.H., and the Maine sampling reach 

is 80 to 180 km downstream from the former chloralkali facility (Rumford to Lisbon, Maine). Data from Maine 

were collected by the Maine Department of Environmental Protection Surface Water Ambient Toxics Monitoring 

Program from 1990 through 2009. Data for New Hampshire were collected between 2009 and 2011. The dashed 

blue line is median reference (AR2) fish tissue concentration; red dashed line is the U.S. Environmental 

Protection Agency (2001, 2009) human health guideline. Letters A, B, and AB indicate statistical significance: 

Stream reaches labeled with “A” are statistically different than stream reaches labeled with “B”, and stream 

reaches labeled “AB” are not statistically different than stream reaches labeled “A” or “B.” ng/g, nanograms 

per gram; ww, wet weight.

reference site (table 4, in back of report). The highest values 

of kmeth were observed at AR4 (fig. 10C), an observation 

that was likely driven by the high concentrations of pw.SO4

and pw.DOC fueling sulfate-reducing Hg(II)-methylating 

microbial activity and consistent with the high sediment TRS 

concentrations and low sediment oxidation reduction potential 

(also known as redox; Eh

) also observed at this site (figs. 5, 11, 

and 12B). The highest calculated MPP rates were at stream 

reaches AR4 and AR7 (fig. 10D). Interestingly, the elevated 

MPP rates at AR4 were driven by the high kmeth values, 

whereas the elevated MPP rates at AR7 were driven by high 

Hg(II)R concentrations (fig. 10A).

Not only was the absolute concentration of Hg(II)R 

greater downstream from the point source than at the reference 

site, but the concentration generally increased with distance 

downstream from the point source (fig. 10A). Far sites (8 to 

16 km downstream from the point source) had significantly 

higher Hg(II)R concentrations in whole sediment than near 

sites (table 5, in back of report). Similarly, the bioaccumulation of mercury generally increased with distance downstream 

from the point source. THg concentrations in smallmouth 

bass and white sucker were significantly higher in far-stream 

reaches than near-stream reaches (table 5, in back of report). 

Near-stream reaches are comparatively short and have a high 

gradient, whereas far-stream reaches are longer and lower in 

gradient (fig. 1). The longer, lower gradient far-stream reaches 

appear to have conditions more conducive to methylation than 

the high-gradient near-stream reaches, which may reflect a 

difference in the type and size of particles that are likely to be 

deposited in these two contrasting hydrologic settings and the 

effect that particles have on the speciation and availability of 

mercury deposited to the benthos.

Controls on Mercury Distribution

Using step-wise linear regression and beginning with 

potential explanatory variables of sediment organic carbon 

(measured as percent LOI), bulk density (BD), percent fines, 

and percent dry weight, the best single model of sediment 
20 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire [8] [8] [8] [8] [8] [8] 

[12]

[8] 

[8] 

[8] 

[8] 

[8] 

[8] 

[12] 

[2] 

[2] 

[2] 

[2] 

[2] 

[2] 

[3] 

[2] 

[2] 

[2] 

[2] 

[2] [2] 

[3] 

10 –2 10 –1 

10 0 

) II Hg( R t en rc pe , in 

AR2 AR4 AR5 AR6 AR7 AR8 AR9 

0.040.030.020.010.00

AR2 AR4 AR5 AR6 AR7 AR8 AR9 

) II Hg( R, in ng/g dw 

1.2 0.8 0.4 0.0 

AR2 AR4 AR5 AR6 AR7 AR8 AR9

k pe h met y da r 

Stream reach Stream reach

AR2 AR4 AR5 AR6 AR7 AR8 AR9

543210

t en im ed g/d dry s pg/ in , MPP

EXPLANATION

75th Median

percentile

25th percentile

MaximumMinimum

[8] Number of observations

Reference Near reaches Far reaches Reference Near reaches Far reaches

Reference Near reaches Far reaches Reference Near reaches Far reaches

D. Sediment methylmercury production potential rate C. Sediment methylmercury production rate constant

A. Sediment reactive mercury B. Sediment percent of reactive mercury

Figure 10. Sediment mercury methylation potential from the Androscoggin River, Coos County, New Hampshire. 

A, Inorganic reactive mercury (Hg(II)R). B, Sediment percentage 

of THg as Hg(II)R. C, Methylmercury production rate constant (kmeth). D, Methylmercury production potential (MPP) rate based on Hg(II)R. Samples were collected in 2010. Samples 

from the reference reach (AR2) are 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–AR6) are 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–AR9) are 8 to 16 km downstream from the former chloralkali facility. The dashed blue line is the median reference (AR2) for sediment Hg(II)R concentration (A), sediment percentage of THg as Hg(II)R (B), rate constant (C), or potential rate (D). dw, dry weight; 

ng/g, nanograms per gram; pg/g/d, picograms per gram per day.
Results and Discussion 21

EXPLANATION

75th Median

percentile

25th percentile

MaximumMinimum

[2] Number of observations

AR2 AR4 AR5 AR6 AR7 AR8 AR9 

10 0 

10 1 

10 2 

10 3 

AR2 AR4 AR5 AR6 AR7 AR8 AR9 

10 

10 

ol/g mm in , RST

, in mg/L 2–

4 pw.SO

Stream reach Stream reach

1 0 

[2] 

[3] 

[2] 

[5] 

[7] 

[2] 

[4] 

[2] 

 [2] 

[2] 

[2] 

[2] 

[3] 

 [2] 

A. Pore-water sulfate B. Sediment total reduced sulfur

Reference Near reaches Far reaches Reference Near reaches Far reaches

Figure 11. Concentrations of A, pore-water sulfate ( pw.SO-24 ) and B, sediment total reduced sulfur (TRS) from the Androscoggin River, Coos County, New 

Hampshire. Samples for pw.SO-24 were collected in 2009 and 2010, and for TRS, in 2010. Samples from the reference reach (AR2) are 16 kilometers (km) upstream 

from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–R6) are 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–R9) are 8 to 16 km downstream from the former chloralkali facility. The dashed blue line is the median reference (AR2) porewater (sulfate) or sediment (TRS) concentration. mg/L, milligrams per liter; mmol/g, micromoles per gram.
22 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire AR2 -100 -200

0

200100

Stream reach 

in mv , h E

0

80604020

rcent pe in , μm) 63 han t ss e(l s ne Fi

Stream reach 

AR4 AR5 AR6 AR7 AR8 AR9 AR2 AR4 AR5 AR6 AR7 AR9 AR8

EXPLANATION

75th Median

percentile

25th percentile

MaximumMinimum

[8] Number of observations

[8] [8] [8] 

[8] 

[8] 

[8] 

[12]

[8] 

[8] 

[8] 

[8] 

[8]

[8] 

[12] 

A. Sediment grain size

Reference Near reaches Far reaches

B. Sediment oxidation reduction potential

Reference Near reaches Far reaches

Figure 12.

A, Sediment grain size less than 63 micrometers (μm) and 

B, oxidation reduction potential (redox, Eh) from the Androscoggin River, Coos County, New 

Hampshire. Samples were collected in 2010. Samples from the reference reach (AR2) are 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches (AR4–R6) are 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches (AR7–R9) are 8 to 16 km downstream from the former chloralkali facility. The dashed blue line is the median reference (AR2) for sediment percent grain size less than 63 micrometers 

h (B). mv, millivolt. (A) or sediment E
Results and Discussion 23

THg concentration throughout the whole study area included 

only percent LOI and BD, although it had low explanatory 

power (coefficient of determination (R2

) of 0.19). However, by 

grouping the downstream study area into near (AR4, AR5, and 

AR6) and far (AR7, AR8, and AR9) stream reaches, regression models could explain 49 to 55 percent of the variability in 

THg concentration (fig. 13). In the far-stream reaches, percent 

LOI alone explained 49 percent of the variability in sediment 

THg concentration. A positive relation between THg and 

percent LOI has been observed in a number of other studies 

(Hammerschmidt and Fitzgerald, 2006; Han and others, 2007; 

Marvin-DiPasquale and others, 2009a, b). In the higher gradient near-stream reaches, sediment BD became an important 

explanatory variable in addition to percent LOI, alluding to 

the nature of the particles that are likely to be deposited in the 

high-gradient environment.

Sediment MeHg concentration across all stream reaches 

was best described as a positive function of sediment THg 

concentration and a negative function of sediment TRS 

concentration (fig. 14), when starting with THg, Hg(II)R, kmeth, 

Eh

, percent LOI, TRS, and percent fines as initial explanatory 

variables in the stepwise regression. Sediment MeHg and THg 

are often correlated at lower THg concentrations (Krabbenhoft and others, 1999; Kamman and others, 2005b; MarvinDiPasquale and others, 2009a; Scudder and others, 2009), as 

seen in this study. The negative relation between MeHg concentration and TRS concentration may reflect Hg(II) binding 

to solid-phase reduced sulfur compounds, thus reducing the 

amount of Hg(II) available for methylation (Huerta-Diaz and 

Morse, 1992; Marvin-DiPasquale and others, 2009a).

Controls on Divalent Mercury Availability for 

Methylation

Explanatory variables used in stepwise linear regression to describe controls on Hg(II)R, kmeth, and MPP included 

percent LOI, TRS, Eh

, percent fines, and THg concentration. 

The availability of sediment Hg(II) for Hg(II)-methylation, 

as assessed by the Hg(II)R assay, was best described as a 

multivariable linear function of sediment THg, percent fines, 

and Eh

. Approximately 50 percent of the variability in sediment Hg(II)R could be explained by these three variables 

across all stream reaches, but 76 percent of Hg(II)R variability 

was accounted for in near-stream reaches alone using the same 

three variables (fig. 15). One-third of the variability in sediment Hg(II)R in far-stream reaches was explained by a combination of percent fines and Eh

. Low variability in sediment 

THg concentrations appeared to make sediment THg a weak 

explanatory variable for sediment Hg(II)R in these stream 

reaches. The positive relation between sediment Hg(II)R and Eh

likely reflects the binding kinetics of inorganic Hg(II) to solidphase minerals and organics, which appear to increase under 

reducing conditions and decrease under more oxic conditions 

(Marvin-DiPasquale and Cox, 2007; Marvin-DiPasquale and 

others, 2009a, b). An increase in percent fines (a decrease in 

sediment grain size) reflects more surface area and solid-phase 

binding sites for Hg(II).

The activity of the in-situ Hg(II)-methylating microbial 

community, as assessed by kmeth, was best predicted by Eh

alone (R2

=0.59; fig. 16). The highest kmeth values were measured at the most chemically reducing site (AR4), and the 

lowest kmeth values were measured at the two most oxidized 

sites (AR8 and AR9; fig. 10). The importance of reducing conditions for microbial Hg(II)-methylation has been documented 

in Morel and others (1998).

Calculated MPP rates were best modeled as a combined 

positive function of THg concentration and negative function 

of sediment Eh

. Because MPP rates are a function of both 

microbial activity (kmeth) and in-situ Hg(II) availability, 

controls on Hg(II)R and kmeth would also apply to MPP. 

Sediment organic carbon (as percent LOI) was less of an 

explanatory variable for predicting Hg(II)-methylation in this 

study compared with other studies (Lambertsson and Nilsson, 

2006; Marvin-DiPasquale and others, 2009a), reflecting the 

limited range of organic carbon concentrations in the study 

area (fig. 5).

Controls on Partitioning between Bed Sediment 

and Pore Water

The distribution of inorganic Hg(II) and MeHg 

between sediment particles (solid-phase) and pore water 

affects the availability of inorganic Hg(II) and MeHg for 

Hg(II)-methylation and bioaccumulation, respectively. 

Grain size (Bloom and others, 1999) and organic content 

(Hammerschmidt and others, 2006; Sunderland and others, 

2006) are often key factors in partitioning between pore 

water and sediment. Typically, partitioning of both THg and 

MeHg from sediment to pore water increases with increasing 

pw.DOC and decreasing percent fines (increasing grain size; 

Marvin-DiPasquale and others, 2009a). DOC contains strong 

mercury-binding ligands that increase mercury dissolution 

into pore water by stabilizing nanoparticles of compounds 

such as cinnabar (HgS; Slowey, 2010; Gerbig and others, 

2011), whereas decreasing percent fines reduces particulate 

surface area and thus potential binding sites on sediments. The 

relation between the distribution coefficient for total mercury 

(kd

[THg]) and the ratio of pw.DOC to grain size [pw.DOC/

percent fines] was first described by Marvin-DiPasquale and 

others (2009a) for eight diverse nonpoint-source streams 

across the United States (in Florida, Wisconsin, and Oregon) 

as part of the USGS National Water Quality Assessment 

Program (NAWQA) mercury topical study. The same 

pw.DOC/percent fines ratio explained 44 and 40 percent of the 

variability in the partitioning coefficients for THg and MeHg, 

respectively, in the Androscoggin River data (fig. 17).

Plotting the Androscoggin River data along with the 

NAWQA data (as kd

[THg] against the pw.DOC/percent fines 

ratio; both log-base-10-transformed), we find that the both 

datasets fall along the same line but that the majority of the 
24 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

R2 = 0.1881 

log10(THg) predicted =1.655 × log10(%LOI)+2.216 × BD – 2.559

R2 = 0.4941 

log10(THg) predicted = 1.125 ×log10(%LOI)+1.264

R2 = 0.5539 

log10 (THg) predicted = 2.465×log10 (%LOI)+4.316 ×BD – 6.265 

1.5

2

2.5

3

icted ed (THg) pr 10 log

log10 (THg ) measured 

1

1.5

2

2.5

3

icted ed (THg) pr 10 log

1 1.5 2 2.5 3

log10 (THg) measured

1

1.5

2

2.5

3

icted ed (THg) pr 10 log

1 1.5 2 2.5 3

log10 (THg) measured

1

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

EXPLANATION

Near ReferenceFar 

Stream Reach

A. Near stream reaches B. Far stream reaches

C. All stream reaches

Figure 13. Predicted against measured sediment total mercury (THg) for 

A, near, 

B, far, 

and 

C, all stream reaches of the Androscoggin River, Coos County, New Hampshire. 

Predicted values were calculated with a stepwise linear regression; the equation and associated regression coefficient of determination (R2) show the best fit model 

using multiple starting variables. The solid linear regression lines are reflections of the regression of measured against predicted values. The 1:1 line between predicted and measured values is dashed. Samples from near-stream reaches are 2 to 4 kilometers (km) downstream from a former chloralkali facility in Berlin, N.H., and samples from farstream reaches are 8 to 16 km downstream. The stream reaches shown in 

C include the 

reference stream reach, which is 16 km upstream from the former chloralkali facility in Berlin. BD, bulk density; %LOI, percent loss on ignition.
Results and Discussion 25

EXPLANATION

Near 

Reference

Far 

Stream Reach

MeHg predicted = 0.795 ×log10 (THg) – 0.528 × log10(TRS) – 0.192 

R2 = 0.5212 

0.0 0.5 1.0 1.5 2.0

MeHg measured 

0

0.5

1

1.5

2

MeHg predicted 

Figure 14. Predicted against measured methylmercury (MeHg) from the Androscoggin 

River, Coos County, New Hampshire. Predicted values were calculated with a stepwise linear 

regression; the equation and associated regression coefficient of determination (R2

) show the 

best fit model using multiple starting variables. The solid linear regression line is a reflection 

of the regression of measured against predicted values. The 1:1 line between predicted and 

measured values is dashed. Samples from the reference stream reach are 16 kilometers (km) 

upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches are 

2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches 

are 8 to 16 km downstream from the former chloralkali facility. THg, total mercury; TRS, total 

reduced sulfur.

Androscoggin River data only occupies the upper one-third of 

the regression line (fig. 18). This suggests that, due to comparatively low pw.DOC or high percent fines (or some combination), THg in the Androscoggin River partitions to a greater 

extent onto sediment particles (larger kd

[THg] values). This 

would imply that THg (almost all as Hg(II)) in the samples 

from the Androscoggin River was comparatively less available 

for Hg(II)-methylation than more than one-half of the sites 

from the earlier NAWQA study. In contrast, MeHg partitioning coefficients (kd

[MeHg]) for the Androscoggin River fell 

along a parallel line to those from the NAWQA study but 

were generally lower for the same pw.DOC/percent fines ratio 

(fig. 19). This implies that MeHg in the Androscoggin River 

partitions to a greater extent in pore water and may be more 

available for bioaccumulation into the food web compared 

with the nonpoint source streams sampled for the NAWQA 

mercury study.

River-Reach Integrated Mercury Species 

Inventories and Methylmercury Production 

Potential Rates

Stream reach integrated inventories of sediment THg, 

Hg(II)R, and MeHg, as well as MPP rates, were calculated for 

each stream reach sampled during 2010. These calculations 

were based on stream reach-specific parameters (table 7), 

including total stream reach area, %fine substrate (percentage 

of stream reach area with grain size less than 63 micrometers), 

stream reach-specific sediment percent dry weight (median 

from all samples collected for mercury analysis), stream 

reach-specific sediment bulk density (median from all samples 

collected for mercury analysis), and depth of fine substrate, 

as assessed with ground-penetrating radar (Degnan and others, 2011) in combination with a nonparametric analysis of 

the mercury species concentration data distribution (table 8), 
26 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire log10(Hg(II)R ) predicted = 0.485 × log10(THg) + 0.855 ×log10 (%fines) + 0.002 ×Eh – 3.359 

R2 = 0.5039

R2 = 0.7576 R2 = 0.3269 

log10 (Hg(II)R ) predicted = 0.252 × log10 (THg) 

 + 0.668 × log10 (%fines) + 0.003 × Eh – 2.599 

log10 (Hg(II)R ) predicted = 0.937×log10 + 0.003 × Eh – 2.517 (%fines)

-2 -1.5 -1 -0.5 0 0.5

log10 (Hg(II)R) measured

-2 -1.5 -1 -0.5 0 0.5

log10 (Hg(II)

R) measured

-2 -1.5 -1 -0.5 0 0.5

-2

-1.5

-1

-0.5

0

0.5

icted ed ) pr ) II g( (H 10 log

-2

-1.5

-1

-0.5

0

0.5

(Hg(II) predicted 10 log

-2

-1.5

-1

-0.5

0

0.5

R R

predicted (Hg(II) 10 log R

log10 (Hg(II)R) measured

EXPLANATION

Near ReferenceFar 

Stream Reach

A. Near stream reaches B. Far stream reaches

C.

All stream reaches

Figure 15. Predicted against measured sediment inorganic reactive mercury 

(Hg(II)R) for 

A, near, 

B, far, and 

C, all stream reaches of the Androscoggin River, Coos 

County, New Hampshire. Predicted values were calculated with a stepwise linear regression; the equation and associated regression coefficient of determination (R2) 

show the best fit model using multiple starting variables. The solid linear regression lines are reflections of the regression of measured against predicted values. The 1:1 line between predicted and measured values is dashed. Samples from near-stream reaches are 2 to 4 kilometers (km) downstream from a former chloralkali facility in Berlin, N.H., and samples from far-stream reaches are 8 to 16 km downstream. The stream reaches shown in 

C are all stream reaches including the reference stream 

reach, which is 16 km upstream from the former chloralkali facility in Berlin. Eh, 

oxidation reduction potential; THg, total mercury; %fines, percent grain size less than 63 micrometers.
Results and Discussion 27

-1-2-3

icted ed ) pr h met (k 10 log

-3 -2.8 -2.6 -2.4 -2.2 -2 -1.8 -1.6 -1.4 -1.2 -1

 log (kmeth) measured 

0 1 2 3 4 5 6

MPP measured

6543210

icted ed pr PPM

10 

R2 = 0.4734 

MPP predicted =1.88 × log10 (THg) – 0.013 ×Eh – 0.441 

R2 = 0.5902 

log10(kmeth) = –0.004×Eh – 1.686 

B. Methylmercury production potential rate A. Methylmercury production rate constant

EXPLANATION

Near Reference

Far 

Stream Reach

Figure 16. Predicted against measured mercury methylation potential (MPP) A, constant (kmeth) and B, rate for the Androscoggin River, Coos County, New Hampshire. 

MPP rate based on reactive mercury. Predicted values were calculated with a stepwise linear regression; the equation and associated regression coefficient of determination (R2) show the best fit model using multiple starting variables. The solid linear regression lines are reflections of the regression of measured against 

predicted values. The 1:1 line between predicted and measured values is dashed. Samples from the reference stream reach are 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches are 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches are 8 to 16 km downstream from the former chloralkali facility. Eh, oxidation reduction potential (redox); THg, total mercury.
28 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

2 3 4

log (kd[MeHg]) measured 

3 4 5 6

log (kd [THg]) measured 

6543

icted ed (k [THg]) pr 10 log

432

icted ed (k [MeHg]) pr 10 log

10 10

d

d

log10 (kd [MeHg]) predicted = –0.515 × log10(pw.DOC/%fines) + 2.674 log10(kd[THg]) predicted = –0.763 × log10(pw.DOC/%fines) + 4.018 

R2 = 0.4421 R2 = 0.4027 

B. Log-transformed partitioning coefficient for methylmercury in sediment A. Log-transformed partitioning coefficient total mercury in sediment 

EXPLANATION

Near ReferenceFar 

Stream Reach

Figure 17. Predicted against measured partitioning coefficient for 

A, total mercury (kd[THg]) and 

B, methylmercury (kd[MeHg]) for the Androscoggin River, Coos 

County, New Hampshire. Predicted values were calculated with a stepwise linear regression; the equation and associated regression coefficient of determination (R2) show the best fit model using multiple starting variables. The solid linear regression lines are reflections of the regression of measured against predicted values. 

The 1:1 line between predicted and measured values is dashed. Samples from the reference stream reach are 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H. Samples from near-stream reaches are 2 to 4 km downstream from the former chloralkali facility, and samples from far-stream reaches are 8 to 

16 km downstream from the former chloralkali facility. pw.DOC/%fines, ratio of pore-water dissolved organic carbon to percent grain size less than 63 micrometers.
Results and Discussion 29

All Data

log10 (kd [THg]) = –0.72*log10 (pw.DOC/%fines) + 3.92 

R2

 = 0.71

NAWQA Data 

R2 = 0.70 

Androscoggin Data 

R2 = 0.44 

-2 -1 0 1 2 3

log10 [pw.DOC/%fines] 

2

3

4

5

6

log10 (kd [THg]) (L/kg ) 

Figure 18. Sediment total mercury partitioning 

coefficient as a function of dissolved organic carbon 

and grain size. Sites on the Androscoggin River 

(red circles) are compared with sites sampled for 

the U.S. Geological Survey National Water-Quality 

Assessment Program (NAWQA, grey triangles) 

across the United States (Marvin-DiPasquale and 

others, 2008, 2009a). kd

 [THg], sediment total mercury 

partitioning coefficient; L/kg, liters per kilogram; 

pw.DOC/%fines, ratio of dissolved organic carbon 

to percent grain size less than 63 micrometers; R2

, 

coefficient of determination]

Figure 19. Sediment methylmercury partitioning 

coefficient as a function of dissolved organic carbon 

and grain size. Sites on the Androscoggin River 

(red circles) are compared with sites sampled for 

the U.S. Geological Survey National Water-Quality 

Assessment Program (NAWQA, grey triangles) across 

the United States (Marvin-DiPasquale and others, 

2008, 2009a). kd

 [MeHg], sediment methylmercury 

partitioning coefficient; L/kg, liters per kilogram; 

pw.DOC/%fines, ratio of dissolved organic carbon 

to percent grain size less than 63 micrometers; R2

, 

coefficient of determination]

2

3

4

5

-2 -1 0 1 2 3

log10 (kd [MeHg]), in (L/kg)

log10 [pw.DOC/%fines]

NAWQA Data

R2 = 0.54

Androscoggin Data

R2 = 0.41

All Data

R2 = 0.40
30 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Table 7. Stream reach parameters used to calculate reach specific depth integrated mercury species inventories and rates.

[Stream reach area data are from Degnan and others (2011). Median sediment dry weight (dw) and bulk density were calculated from 2010 data only. Median 

depth of fine substrate was calculated excluding unknown (zero) observations. m2, square meters; g/cm3 ww, grams of wet weight per cubic centimeter; 

m, meters]

Reach Description Reach area, 

in m2

Fine substrate, 

in percent of area

Median sediment, 

in percent dw

Median sediment 

bulk density, 

in g/cm3

 ww

Median depth of sand, 

silt, and clay layer, 

in m

AR2 Wheeler Bay 89,108 55.6 47.2 1.37 1.18

AR4 Upstream of Smith Dam 31,129 14.4 60 1.53 0.64

AR5 Upstream of Power Dam 53,662 10 71.7 1.73 0.95

AR6 Power Dam to Cascade Dam 62,717 27.6 57.8 1.5 1.12

AR7 Cascade to Brown Dam 296,807 10.5 48.2 1.37 0.79

AR8 Brown Dam to Gorham Dam 205,155 7.6 66.8 1.63 0.97

AR9 Gorham Dam to Shelburne Dam 696,373 45.7 64.4 1.6 1.07

quartile distribution, and medians and 25 to 75 percent interquartile data. A simplifying assumption used in the calculation was that mercury species concentrations and MPP rates 

were zero for any substrate coarser than sand. Because large 

areas within each stream reach had substrate coarser than sand 

(table 7), it is likely that this simplifying assumption resulted 

in these inventories underestimating the actual amount of 

mercury species and MPP rates in each case and should be 

considered as minimum estimates. All mercury species inventories and MPP rates were first calculated for the top 10 cm 

only because that was the actual sediment sampling depth. 

A second simplifying assumption was that THg and 

Hg(II)R concentrations were constant with sediment depth. 

As such, we then calculated the stream reach-specific THg 

and Hg(II)R inventories for the full depth of the fine substrate, 

based on the median depth for the given reach (table 7).

Concentrations of mercury species and MPP rates, on 

a sediment dry weight basis, were higher in stream reaches 

downstream from the point source (figs. 3A, B, 10A and D; 

table 8). Whereas the distribution of sediment dry weight 

concentrations reflected the relative location of the sampling 

sites to the point source, stream reach-specific mercury 

inventories reflected the amount depositional environments 

with fine-grained sediment in each reach. AR9 was the 

largest stream reach sampled and had the largest percentage 

of area as fine substrate downstream from the point source 

(table 7). These geophysical conditions resulted in mercury 

inventories (total mass) being much larger in reach AR9 than 

in any other reach (table 8). In contrast, reach AR4 had the 

smallest area and the fourth smallest areal percentage of fine 

substrate (table 7), and as a consequence, typically had the 

smallest calculated mercury species inventories. For the top 

0- to 10-cm-depth interval, median mercury inventory range 

estimates for all stream reaches downstream from the point 

source were as follows: THg, 0.03 to 2.91 kilograms (kg); 

Hg(II)R, 0.03 to 4.64 grams (g); MeHg, 0.20 to 32.9 g; and 

MPP rate, 1.10 to 14.8 milligrams per day (mg/d). On the 

basis of the median depth of the fine deposits in each reach, 

the median mass inventories for THg and Hg(II)R ranged from 

0.21 to 31.0 kg and 0.19 to 49.4 g, respectively (table 8).

Ecological Impact

The health of the aquatic ecosystem that was potentially 

affected by the former chloralkali facility was evaluated using 

a variety of toxicity tests, biological indices, and guidelines. 

Results of pore-water and surface-water bioassays are detailed 

in Environmental Services Assistance Team (2009a, b, 

respectively), and bulk sediment bioassays, in EnviroSystems, 

Inc., (2010a, b). Survival and growth of Hyalella azteca and 

Chironomus dilutus in sediment and survival of Hyalella 

azteca and Chironomus tentans in pore water collected 

downstream from the former chloralkali facility were not 

significantly different from the reference site (table 5, in back 

of report). Survival and reproduction of Ceriodaphnia dubia 

and survival and growth of Pimephales promelas provided no 

evidence of toxicity of surface water collected downstream 

from the former chloralkali site (table 2–13; Environmental 

Services Assistance Team, 2009b); however, the number of 

samples (n=5) collected did not allow for statistical testing.

Sites were evaluated for biological condition based on 

scores calculated with the use of the NHDES B–IBI for invertebrate assemblages (table 2–17). The B–IBI is designed to 

provide a relative measure of stream health and is centered on 

the mean (average) value of seven indicator metrics that reflect 

the biological condition of streams and rivers in the region, 

including the Androscoggin River. The Androscoggin River 

reaches AR2 through AR9 were classified as being exclusive 

to the Hills reference sites. The 25th percentile (64.5) for 
Results and Discussion 31

Table 8. Depth-integrated mercury species inventories and rates, by river reach.[Mercury species and rates were calculated from 2010 data. Full depth inventories are based on median depth of fine substrate. ng/g dw, nanograms per gram dry weight; mg/m2, milligrams per square meter; 

cm, centimeters; kg, kilograms; g, grams; Q, quartile; <, less than; %, percent]

Reach

Quartile data by reach, 

in ng/g dw

10-cm depth integrated, 

in mg/m2

Reach integrated (top 10 cm), 

in kg

Reach integrated (full depth), 

in kg

25th% Q 50th% Q 75th% Q 25th% Q 50th% Q 75th% Q 25th% Q 50th% Q 75th% Q 25th% Q 50th% Q 75th% Q

A. Total mercury

AR2 21 26 30 1.3 1.7 1.9 0.07 0.08 0.10 0.78 0.97 1.70

AR4 61 79 106 5.6 7.2 9.7 0.03 0.03 0.04 0.16 0.21 0.39

AR5 128 190 321 15.9 23.6 39.9 0.09 0.13 0.21 0.81 1.21 2.44

AR6 81 106 197 7.0 9.2 17.1 0.12 0.16 0.30 1.36 1.78 4.38

AR7 112 134 214 7.4 8.8 14.1 0.23 0.27 0.44 1.82 2.17 4.80

AR8 117 123 137 12.8 13.4 15.0 0.20 0.21 0.23 1.92 2.02 3.53

AR9 44 88 137 4.5 9.1 14.1 1.43 2.91 4.50 15.3 31.0 78.6

B. Reactive inorganic mercury

AR2 0.09 0.11 0.13 0.0055 0.0071 0.0086 0.27 0.35 0.43 3.23 4.16 7.57

AR4 0.05 0.07 0.15 0.0043 0.0065 0.0141 0.02 0.03 0.06 0.12 0.19 0.56

AR5 0.15 0.17 0.19 0.0191 0.0211 0.0236 0.1 0.11 0.13 0.98 1.08 1.44

AR6 0.15 0.22 0.25 0.0131 0.0189 0.0218 0.23 0.33 0.38 2.54 3.67 5.6

AR7 0.34 0.37 0.41 0.0222 0.0244 0.0272 0.69 0.76 0.85 5.46 6.00 9.22

AR8 0.17 0.2 0.43 0.0184 0.0222 0.0471 0.29 0.34 0.73 2.77 3.33 11.1

AR9 0.13 0.14 0.18 0.0132 0.0146 0.0187 4.21 4.64 5.94 44.8 49.4 104

Reach

Quartile data by reach, 

in ng/g

10-cm depth integrated, 

in mg/m2

Reach integrated (top 10 cm), 

in g

25th% Q 50th% Q 75th% Q 25th% Q 50th% Q 75th% Q 25th% Q 50th% Q 75th% Q

C. Methylmercury

AR2 0.155 0.221 0.353 0.010 0.014 0.023 0.50 0.71 1.13

AR4 0.24 0.49 0.74 0.022 0.045 0.068 0.10 0.20 0.30

AR5 1.26 1.32 1.39 0.157 0.164 0.173 0.84 0.88 0.93

AR6 0.28 0.65 1.7 0.024 0.057 0.147 0.42 0.98 2.54

AR7 0.78 1.03 1.29 0.052 0.068 0.085 1.61 2.12 2.64

AR8 0.65 0.96 1 0.071 0.104 0.109 1.10 1.62 1.69

AR9 0.71 1 1.61 0.073 0.103 0.166 23.3 32.9 52.8

D. Methylmercury production potential rate

AR2 0.00064 0.00079 0.00095 0.041 0.051 0.061 2.05 2.54 3.03

AR4 0.00268 0.00414 0.00559 0.25 0.38 0.51 1.10 1.70 2.30

AR5 0.00103 0.00157 0.00211 0.13 0.20 0.26 0.69 1.05 1.41

AR6 0.00142 0.00269 0.00396 0.12 0.23 0.34 2.12 4.02 5.92

AR7 0.00368 0.00411 0.00454 0.24 0.27 0.30 7.60 8.40 9.30

AR8 <0.00050 0.00075 0.00127 <0.054 0.082 0.14 <0.85 1.27 2.15

AR9 <0.00034 0.00045 0.00298 <0.035 0.047 0.31 <11.0 14.8 98.0
32 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Hills reference sites is operationally defined as the threshold, 

and 90 percent (58) of the threshold categorizes the stream as 

unimpaired for the NHDES listing of impaired waters (Neils, 

NHDES, 2007). The B–IBI integrates the following metrics, 

which are denoted with (+) to indicate where values increase 

with improving conditions and (-) to indicate where values 

decrease with improving conditions: 

• total taxa richness (+)

• plecoptera (stoneflies) taxa (+)

• percent chironomidae (midge) taxa (-)

• percent noninsect taxa (-)

• tolerant taxa (-)

• percent intolerant (sensitive) taxa (+)

• percent clinger taxa (+) 

For (-) metrics that decrease with improving conditions, the 

inverse values were used in calculating the B–IBI score so that 

these metrics would contribute to the B–IBI increasing with 

improving condition. All replicates at all sites exceeded the 

B–IBI threshold of 58, indicating that the sites were categorized as meeting the criteria for unimpaired streams by 

NHDES standards (fig. 20; David Neils, NHDES, written 

commun., April 2011).

Jaccard’s indices were used to compare species diversity 

within and between stream reaches. The percentage of similarity within stream reaches was 51 ±9 (average plus or minus (±) 

standard deviation). This compares closely to the percentage 

of similarity among stream reaches AR2, AR3, AR8, and AR9 

(55 ±5). AR4 was the most different from other stream reaches 

with the percentage of similarity equal to 35 ±2. This section 

of the river is highly regulated, and the rock baskets were not 

in flowing water the entire 6.5 weeks they were in the river. 

Jaccard’s indices did not show differences in species diversity 

upstream and downstream from the point source; however, 

Jaccard’s indices did suggest flow characteristics were a major 

factor controlling species diversity in the study area. 

Differences in total abundance, total taxa, and 

Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa between 

invertebrate assemblages upstream and downstream from the 

point source were compared using nonparametric WRS and 

KWRS tests. The total abundance of organisms is a general 

indicator of productivity, whereas total taxa and EPT taxa are 

two indicators of taxonomic complexity in the assemblages. 

The highest total abundance occurred at AR3 adjacent to the 

former chloralkali facility (table 2–17). The higher abundance 

0

20

40

60

80

100

AR-2 AR-3 AR-4 AR-8 AR-9

B-IBI score

Stream reach

Replicate 1

Replicate 2

Replicate 3

Replicate 4

B-IBI threshold

EXPLANATION

Figure 20. New Hampshire Department of Environmental Services (NHDES) benthic index of biotic 

integrity (B–IBI) for the Androscoggin River, Coos County, New Hampshire. The reference reach (AR2) 

is 16 kilometers (km) upstream from a former chloralkali facility in Berlin, N.H., and stream reaches AR3, 

AR4, AR8, and AR9 are 0 to 16 km downstream from the former chloralkali facility. Three replicate samples 

were collected at AR2, AR3, AR8, and AR9, and four replicate samples at AR4. The NHDES B–IBI threshold 

is 58. Stream reaches that score higher than the B–IBI threshold are categorized as unimpaired.
Results and Discussion 33

at AR3 compared with other sites was mainly due to greater 

abundance of Diptera Simuliidae Simulium, which presumably 

favored the steady low-flow water conditions at this site. 

Abundance downstream from the point source was not 

significantly different from the reference site (table 4, in back 

of report). Total taxa (the total number of taxa in the sample) 

and EPT taxa (taxa in the generally more environmentally 

sensitive orders Ephemeroptera (mayflies), Plecoptera, and 

Trichoptera (caddisflies)) were both highest at AR9 (table 5, in 

back of report); however, there was no significant difference 

in either metric among the spatial grouping of far (AR8, AR9), 

near (AR3, AR4), or reference (AR2) stream reaches.

Surface-water THg and MeHg concentrations in the 

Androscoggin River were all below the Canadian guideline 

for the protection of aquatic life (table 9; Canadian Council 

of Ministers of the Environment, 1999). One surfacewater THg concentration exceeded the 30-day standard 

of 1.3 ng/L set by the USEPA for Great Lakes fish-eating 

wildlife (U.S. Environmental Protection Agency, 1995). 

Sediment THg concentrations did not exceed the 1,060 ng/g 

dry weight consensus-based probable effect concentration 

(PEC) for adverse effects to benthic organisms in any 

sample (MacDonald and others, 2000), but one-quarter of 

the sediment samples did exceed the 180 ng/g dry weight 

consensus-based threshold effects concentration (TEC) 

for adverse effects to benthic organisms (MacDonald and 

others, 2000) and the 170 ng/g Canadian interim sediment 

quality guidelines (ISQG) for the protection of aquatic life 

(Canadian Council of Ministers of the Environment, 1999). 

The Wheeler Bay reference site was the only site that had 

no sediment sample with concentrations above the TEC and 

ISQG guidelines, and only AR5 had a median sediment THg 

concentration higher than the TEC and ISQG guidelines. 

Whereas water and sediment THg were mostly below 

guidelines, smallmouth bass THg concentrations in all samples 

(table 9) were higher than guidelines set for fish-eating birds 

(13 ng/g, kingfisher; Sample and others, 1996), fish-eating 

mammals (79 ng/g, river otter; Sample and others, 1996), 

and human health (140 ng/g; U.S. Environmental Protection 

Agency, 2001c, 2009).

Comparison to Other Studies

Data from the Androscoggin River were compared 

with datasets from the Northeastern Ecosystems Research 

Cooperative (NERC) and the USGS NAWQA (Kamman and 

others, 2005a, b; Shanley and others, 2005; Bauch and others, 

2009). The NERC dataset is a compilation of regional stream 

data from New England, New York, Quebec, Ontario, and the 

Atlantic provinces of Canada, whereas the NAWQA dataset 

includes stream data from across the United States. Grouped 

medians from the Androscoggin River, the NERC, and the 

NAWQA datasets were compared using a KWRS test. For 

purposes of comparison, Androscoggin River smallmouth bass 

THg data from the NERC dataset were combined with data 

from the study of this report. Androscoggin River sediment 

THg concentrations were not significantly different than 

concentrations in the regional or national surveys. Sediment 

from the Androscoggin River had significantly lower MeHg 

concentrations than other streams in the Northeastern region 

but similar MeHg concentrations to streams across the country 

(table 10). However, comparisons between the surficial 

sediment from the Androscoggin River study and from other 

studies may have some bias because the sediment in the 

Androscoggin River study was sampled to 10 cm, whereas 

sediments in the NERC and NAWQA studies were generally 

sampled to 2 cm and never deeper than 5 cm. The greater 

sampling depth of the Androscoggin sediments could have 

a diluting effect, lowering THg and MeHg concentrations 

relative to the other surveys. Smallmouth bass THg 

concentrations from the Androscoggin River downstream from 

the point source were significantly higher than smallmouth 

bass from across the country, but only smallmouth bass 

from the furthest downstream stream reaches (AR7–AR9) 

were significantly higher than smallmouth bass from the 

Northeastern region studies (table 10). Surface-water THg 

and MeHg concentrations from the Androscoggin River study 

were similar to those from regional and national studies that 

focused on uncontaminated or nonpoint source lotic systems; 

however, the number of observations was too small (n=1–2) 

for statistical evaluation.
34 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Table 9. Guidelines for total mercury in surface water, sediment, and fish and methylmercury in surface water.

[Guidelines are listed with the percentage of samples from the Androscoggin River that exceeded the guideline shown in brackets. Methylmercury (MeHg) 

guidelines are used for fish-eating wildlife and human health because more than 95 percent of mercury in smallmouth bass is MeHg. ng/L, nanograms per liter; 

dw, dry weight; THg, total mercury; ng/g, nanograms per gram; ww, wet weight; --, no data]

Guideline

Unfiltered surface water, 

in ng/L THg surfical sediment, 

in ng/g dw

THg smallmouth bass fillet, 

in ng/g ww THg MeHg

Fish-eating wildlife1 1.3 [20] -- -- --

Aquatic life2 26 [0] 4 [0] 170 [25] --

Threshold effects level3 -- -- 180 [23] --

Probable effects level3 -- -- 1,060 [0] --

Fish-eating mammal4 -- -- -- 79 [100]

Human health5 -- -- -- 140 [100]

1

U.S. Environmental Protection Agency, 1995a.

2

Canadian Council of Ministers of the Environment, 1999.

3

MacDonald and others, 2000.

4

Sample and others, 1996.

5

U.S. Environmental Protection Agency, 2001c, 2009.

Table 10. Comparison of mercury concentrations in the Androscoggin River, Coos County, New Hampshire, with National WaterQuality Assessment Program and Northeastern Ecosystem Research Cooperative datasets.

[Mercury concentrations are median values; values in bold are statistically different. Letters A, B, and C, indicate which medians are different: A medians are 

statistically different than B medians, AB medians are not statistically different than A or B but are different from C, and ABC indicates medians are not statistically different than A, B, or C. The nonparametric Kruskal-Wallis rank sum test was run only for sites with at least five samples. Data are from streams only. 

Numbers in brackets are the number of samples from each site. Data for the Northeastern Ecosystem Research Cooperative (NERC) study were collected from 

1983 through 2002; data for the National Water-Quality Assessment Program study were collected from 1998 through 2005; data for the Androscoggin River 

study were collected from 2009 through 2011. Surficial sediments are from the top 10 centimeters (cm) in the Androscoggin study and the top 2 or 5 cm in other 

studies. For purposes of comparison, all smallmouth bass lengths were restricted to 25 to 38 cm, and data for smallmouth bass from the NERC dataset have 

been combined with the Androscoggin River study data. All smallmouth bass samples are fillets. THg, total mercury; MeHg, methylmercury; dw, dry weight; 

ng/g, nanograms per gram; ng/L, nanograms per liter; ww, wet weight]

Site location

THg unfiltered 

surface water, 

in ng/L

MeHg unfiltered 

surface water, 

in ng/L

THg surfical 

sediment, 

in ng/g dw

MeHg surfical 

sediment, 

in ng/g dw

THg smallmouth 

bass fillet, 

in ng/g ww

Androscoggin River data

Upstream of point source 1.00 [1] 0.05 [1] 30 [11] AB 0.23 [5] B 418 [10] ABC

Downstream near point source 1.02 [2] 0.05 [2] 117 [25] AB 0.74 [7] B 528 [26] AB

Downstream far from point source 1.30 [2] .06 [2] 111 [35] AB 0.98 [14] B 599 [28] A

Other datasets

Northeastern North America1,2,3 2.20 [388] A 0.20 [101] A 160 [182] A 2.70 [69] A 410 [179] B

United States4 2.06 [287] B 0.09 [288] B 25.4 [296] B 0.40 [295] B 273 [46] C

1

Shanley and others, 2005.

2

Kamman and others, 2005b.

3

Kamman and others, 2005a.

4

Bauch and others, 2009.
Selected References 35

Summary and Conclusions

During operation of the chloralkali facility in Berlin, 

New Hampshire, elemental mercury (Hg0

) was spilled into the 

Androscoggin River, contaminating the overburden and 

underlying fractured rock on the east (left) bank of the 

Androscoggin River. In September 2005, Congress added 

the former chloralkali facility in Berlin to the national priorities list, commonly known as the Superfund list. Mercury 

contamination from historical paper and saw mill activities 

represents a significant potential risk to human health and the 

environment.

Total mercury (THg) and methylmercury (MeHg) 

concentrations in Androscoggin River sediment, pore water, 

and biota were elevated downstream from the former chloralkali facility relative to reference sites. Sequential extraction 

of surface sediment showed a distinct difference in mercury 

speciation upstream compared with downstream from the former chloralkali facility. The reference site was dominated by 

potassium hydroxide-extractable THg consistent with organic 

mercury or particle-bound divalent mercury (Hg(II)), whereas 

sites downstream from the point source were dominated by 

concentrated nitric acid-extractable THg, indicative of Hg0

 or 

mercurous chloride. Mercury metrics from the study indicated 

Hg(II) at the reference site was more available for Hg(II)-

methylation compared with sites downstream from the point 

source, but the absolute concentrations of whole sediment 

Hg(II)R and THg in biota were greater downstream from the 

point source. In addition, whole sediment Hg(II)R and smallmouth bass THg concentrations appeared to increase further 

downstream from the point source. The furthest downstream 

reach (AR9 from Gorham Dam to Shelburne Dam) had larger 

mass of fine sediment and larger estimated mass inventory of 

mercury species than any other stream reach by an order of 

magnitude for both masses.

Sediment organic carbon and bulk density were the 

dominant influences on sediment THg distribution. The 

availability of Hg(II) for methylation was best described as a 

positive function of sediment THg, percent fines, and sediment oxidation reduction potential (redox; Eh

). The microbial 

activity associated with Hg(II)-methylation (as measured by 

the mercury methylation potential (MPP) constant (kmeth)) was 

best described by Eh

 alone. MPP was primarily a function of 

sediment THg concentration and Eh

.

Toxicity tests and invertebrate community assessment 

suggest that impairment of invertebrates is not occurring at 

the current (2009 and 2010) levels of mercury contamination downstream from the point source. Concentrations of 

THg and MeHg in most water and sediment samples from the 

Androscoggin River were below Federal and consensus-based 

guidelines, whereas smallmouth bass mercury concentrations were above U.S. Environmental Protection Agency and 

regional guidelines in all samples. Smallmouth bass THg 

concentrations from the Androscoggin River downstream from 

the point source were significantly higher than those reported 

in a national survey, but only smallmouth bass mercury 

concentrations from the furthest downstream stream reaches 

(Cascade Dam to Shelburne Dam) were significantly higher 

than those in Northeastern region studies. 

The apparent greater potential for Hg(II)-methylation and 

mercury bioaccumulation in the lower gradient stream reaches 

of the Androscoggin River may reflect changes in the type and 

size of particles deposited to the benthos and the speciation 

and availability of mercury for Hg(II)-methylation associated with those particles. These findings suggest that an even 

greater potential for Hg(II)-methylation and mercury bioaccumulation may exist as the river gradient continues to flatten 

downstream from Shelburne Dam.

Selected References

Ainsworth, C.C., Cullinan, V.I., Crecelius, E.A., Wagnon, 

K.B., and Nielwolny, L.A., 2005, Sample holding time 

reevaluation: U.S. Environmental Protection Agency 

EPA/600/R–05/124, 329 p., at http://www.epa.gov/esd/cmb/

research/bs_033cmb06.pdf.

Amyot, Marc, Morel, F.M.M., and Ariya, P.A., 2005, Dark 

oxidation of dissolved and liquid elemental mercury 

in aquatic environments: Environmental Science and 

Technology, v. 39, no. 1, p. 110–114.

Avatar Environmental, 2009, Standard operating procedure for 

fish collection and processing, appendix A of Androscoggin 

River investigation, chloralkali superfund site, Berlin, N.H.: 

Avatar Environmental [variously paged].

Bauch, N.J., Chasar, L.C., Scudder, B.C., Moran, P.W., 

Hitt, K.J., Brigham, M.E., Lutz, M.A., and Wentz, D.A., 

2009, Data on mercury in water, bed sediment, and fish 

from streams across the United States, 1998–2005: U.S. 

Geological Survey Data Series 307, 33 p., accessed 

January 8, 2013, at http://pubs.usgs.gov/ds/307/.

Blocksom, Karen, 2004, Development of the New Hampshire 

Benthic Index of Biotic Integrity, in Neils, David, 2007, 

NH benthic index of biotic integrity (B–IBI) for wadeable 

streams—2006 threshold modification to account for natural 

variation: New Hampshire Department of Environmental 

Services, 39 p., accessed January 8, 2013, at 

http://des.nh.gov/organization/divisions/water/wmb/

swqa/2006/documents/appendix33.pdf.

Bloom, N.S., Gill, G.A., Cappellino, Steven, Dobbs, Charles, 

McShea, Larry, Driscoll, Charles, Mason, Robert, and 

Rudd, John, 1999, Speciation and cycling of mercury in 

Lavaca Bay, Texas, sediments: Environmental Science and 

Technology, v. 33, no. 1, p. 7–13.
36 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Bloom, N.S., Preus, Eve, Katon, Jodie, and Hiltner, Misti, 

2003, Selective extractions to assess the biogeochemically 

relevant fractionation of inorganic mercury in sediments 

and soils: Analytica Chimica Acta, v. 479, p. 233–248.

Buck, David, and Evers, David, 2011, Standard operating 

procedure for bird and mammal tissue for contaminant 

analysis, former chloralkali facility, Berlin, N.H., RFP 

80013–040 of Nobis Engineering, quality assurance project 

plan, ecological investigation, chloralkali facility (former) 

superfund site, Berlin, New Hampshire: U.S. Environmental 

Protection Agency Task Order 0013–RI–CO–01BQ, Remedial Action Contract EP–S1–06–03 [variously paged].

Canadian Council of Ministers of the Environment, 1999, 

Canadian environmental quality guidelines: Canadian 

Council of Ministers of the Environment, accessed April 16, 

2013, at http://st-ts.ccme.ca/.

Degnan, J.R., Clark, S.F., Harte, P.T., and Mack, T.J., 2005, 

Geology and preliminary hydrogeological characterization 

of the Cell-House site, Berlin, New Hampshire, 2003–04: 

U.S. Geological Survey Scientific Investigations Report 

2004–5282, 55 p., 1 pl. (Also available at http://pubs.usgs.

gov/sir/2004/5282/.)

Degnan, J.R., Teeple, A.P., Johnston, C.M., MarvinDiPasquale, M.C., and Luce, Darryl, 2011, Geophysical bed 

sediment characterization of the Androscoggin River from 

the former chloralkali facility superfund site, Berlin, New 

Hampshire, to the state border with Maine, August 2009: 

U.S. Geological Survey Scientific Investigations Report 

2011–5158, 27 p. (Also available at http://pubs.usgs.gov/

sir/2011/5158/.)

Dennis, I.F., Clair, T.A., Driscoll, C.T., Kamman, Neil, 

Chalmers, Ann, Shanley, Jamie, Norton, S.A., and Kahl, 

Steve, 2005, Distribution patterns of mercury in lakes and 

rivers of northeastern North America: Ecotoxicology, v. 14, 

p. 113–123.

Dong, Wenming, Liang, Liyuan, Brooks, Scott, Southworth, 

George, and Gu, Baohua, 2010, Roles of dissolved organic 

matter in the speciation of mercury and methylmercury in a 

contaminated ecosystem in Oak Ridge, Tennessee: Environmental Chemistry, v. 7, no. 1, p. 94.

Environmental Services Assistance Team, 2009a, Two species, 96-hour, acute toxicity testing results using pore water 

samples collected from the Androscoggin River in areas 

associated with former chloralkali facility in Berlin, N.H.: 

U.S. Environmental Protection Agency Task Order 26–04, 

TDF No. 1501, Project Numbers 09090027 and 09090039, 

57 p.

Environmental Services Assistance Team, 2009b, Two species, 

chronic toxicity testing results using surface water samples 

collected from the Androscoggin River in areas associated 

with former chloralkali facility in Berlin, N.H.: U.S. 

Environmental Protection Agency Task Order 26–04, TDF 

No. 1501, Project Number 09090023, 46 p.

EnviroSystems, 2010a, 20-day Hyalella azteca survival and 

growth sediment toxicity test, in Nobis Engineering, Inc. 

Project 80013 DAS–RAC2–030, Toxicity evaluation of 

freshwater sediment samples: U.S. Environmental Protection Agency Task Order 10–NH–80013–045–TO–01, p. 14.

EnviroSystems, 2010b, 20-day Chironomus dilutes survival 

and growth sediment toxicity test, in Nobis Engineering, 

Inc. Project 80013 DAS–RAC2–030, Toxicity evaluation of 

freshwater sediment samples: U.S. Environmental Protection Agency Task Order 10–NH–80013–045–TO–01, p. 13.

Gerbig, C.A., Kim, C.S., Stegemeier, J.P., Ryan, J.N., and 

Aiken, G.R., 2011, Formation of nanocolloidal metacinnabar in mercury-DOM-sulfide systems: Environmental 

Science and Technology, v. 45, no. 21, p. 9180–9187.

Gilmour, C.C., Henry, E.A., and Mitchell, R., 1992, Sulfate 

stimulation of mercury methylation in freshwater sediments: 

Environmental Science and Technology, v. 26, p. 2281–

2287. 

Hammerschmidt, C.R., and Fitzgerald, W.F., 2006, Methylmercury cycling in sediments on the continental shelf of 

southern New England: Geochimica et Cosmochimica Acta, 

v. 70, no. 4, p. 918–930.

Han, S., Obraztsova, A., Pretto, P., Choe, K.Y., Gieskes, 

J., Deheyn, D.D., and Tebo, B.M., 2007, Biogeochemical factors affecting mercury methylation in sediments of 

the Venice Lagoon, Italy: Environmental Toxicology and 

Chemistry, v. 26, no. 4, p. 655–663.

Helsel, D.R., 2005, Nondetects and data analysis—Statistics 

for censored environmental data: New York, John Wiley & 

Sons, Inc., 250 p.

Hill, J.R., O’Driscoll, N.J., and Lean, D.R.S., 2009, Size distribution of methylmercury associated with particulate and 

dissolved organic matter in freshwaters: Science of the Total 

Environment, v. 408, no. 2, p. 408–414.

Horvat, Milena, Liang, Lian, and Bloom, N.S., 1993, Comparison of distillation with other current isolation methods 

for the determination of methyl mercury compounds in 

low level environment samples—Part II. Water: Analytica 

Chimica Acta, v. 282, p. 153–168.

Huerta-Diaz, M.A., and Morse, J.W., 1992, Pyritization of 

trace metals in anoxic marine sediments: Geochimica et 

Cosmochimica Acta, v. 56, p. 2681–2702.
Selected References 37

Kamman, N.C., Burgess, N.M., Driscoll, C.T., Simonin, 

H.A., Goodale, Wing, Linehan, Janice, Estabrook, Robert, 

Hutcheson, Michael, Major, Andrew, Scheuhanmer, A.M., 

and Scruton, D.A., 2005a, Mercury in freshwater fish of 

northeast North America—A geographic perspective based 

on fish tissue monitoring databases: Ecotoxicology, v. 14, 

nos. 1–2, p. 163–180.

Kamman, N.C., Chalmers, Ann, Clair, T.A., Major, Andrew, 

Moore, R.B., Norton, S.A., and Shanley, J.B., 2005b, Factors influencing mercury in freshwater surface sediments of 

northeast North America: Ecotoxicology, v. 14, nos. 1–2, 

p. 101–111.

Kendall, Carol, Silva, S.R., and Kelly, V.J., 2001, Carbon and 

nitrogen isotopic compositions of particulate organic matter 

in four large river systems across the United States: Hydrological Processes, v. 15, no. 7, p. 1301–1346.

Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., Olson, 

M.L., DeWild, J.F., and Sabin, T.J., 1999, A national pilot 

study of mercury contamination of aquatic ecosystems 

along multiple gradients: U.S. Geological Survey WaterResources Investigations Report 99–4018B [not paged]. 

(Also available at http://toxics.usgs.gov/pubs/wri99-4018/

Volume2/sectionB/2301_Krabbenhoft/index.html.)

Lambertsson, Lars, and Nilsson, Mats, 2006, Organic material—The primary control on mercury methylation and 

ambient methyl mercury concentrations in estuarine sediments: Environmental Science and Technology, v. 40, no. 6, 

p. 1822–1829.

Lutz, M.A., Brigham, M.E., and Marvin-DiPasquale, Mark, 

2008, Procedures for collecting and processing streambed 

sediment and pore water for analysis of mercury as part of 

the National Water-Quality Assessment Program: U.S. Geological Survey Open-File Report 2008–1279, 68 p. (Also 

available at http://pubs.usgs.gov/of/2008/1279/.)

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology, v. 39, no. 1, 

p. 20–31.

Maine Department of Environmental Protection, 2009, 

Surface Water Ambient Toxics Monitoring Program—2009 

final report: Augusta, Maine, Maine Department of 

Environmental Protection, 168 p., accessed January 14, 

2013, at http://www.maine.gov/dep/water/monitoring/

toxics/swat/2009/2009_SWAT_report_final.pdf.

Marvin-DiPasquale, M.C., and Agee, J.L., 2003, Microbial 

mercury cycling in sediments of the San Francisco BayDelta: Estuaries, v. 26, p. 1517–1528.

Marvin-DiPasquale, M.C., Agee, J.L., Kakouros, Evangelos, 

Kieu, L.H., Fleck, J.A., and Alpers, C.N., 2011, The effects 

of sediment and mercury mobilization in the South Yuba 

River and Humbug Creek confluence area, Nevada County, 

California—Concentrations, speciation and environmental 

fate—Part 2. Laboratory experiments: U.S. Geological 

Survey Open-File Report 2010−1325B, 53 p., accessed 

January 14, 2013, at http://pubs.usgs.gov/of/2010/1325B.

Marvin-DiPasquale, M.C., Alpers, C.N., and Fleck, J.A., 

2009b, Mercury, methylmercury, and other constituents in 

sediment and water from seasonal and permanent wetlands 

in the Cache Creek Settling basin and Yolo bypass, Yolo 

County, California, 2005−06: U.S. Geological Survey 

Open-File Report 2009–1182, 69 p., accessed January 14, 

2013, at http://pubs.usgs.gov/of/2009/1182/.

Marvin-DiPasquale, M.C., and Cox, M.H., 2007, Legacy 

mercury in Alviso Slough, south San Francisco Bay, 

California—Concentration, speciation and mobility: U.S. 

Geological Survey Open-File Report 2007–1240, 98 p. 

(Also available at http://pubs.usgs.gov/of/2007/1240/.)

Marvin-DiPasquale, M.C., Hall, B.D., Flanders, J.R., 

Ladizinski, N., Agee, J.L., Kieu, L.H., and WindhamMyer, Lisamarie, 2006, Ecosystem investigations of 

benthic methylmercury production—A tin-reduction 

approach for assessing the inorganic mercury pool available 

for methylation: Mercury 2006—Eighth International 

Conference on Mercury as a Global Pollutant, Madison, 

Wisc., August 6–11, 2006 [abstract].

Marvin-DiPasquale, M.C., Lutz, M.A., Brigham, M.E., 

Krabbenhoft, D.P., Aiken, G.R., Orem, W.H., and Hall, 

B.D., 2009a, Mercury cycling in stream ecosystems—2. 

Benthic methylmercury production and bed sediment-pore 

water partitioning: Environmental Science and Technology, 

v. 43, no. 8, p. 2726–2732.

Marvin-DiPasquale, M.C., Lutz, M.A., Krabbenhoft, D.P., 

Aiken, G.R., Orem, W.H., Hall, B.D., DeWild, J.F., and 

Brigham, M.E., 2008, Total mercury, methylmercury, 

methylmercury production potential, and ancillary 

streambed-sediment and pore water data for selected 

streams in Oregon, Wisconsin, and Florida, 2003–04: U.S. 

Geological Survey Data Series 375, 25 p. (Also available at 

http://pubs.usgs.gov/ds/375/.)

Matthes, W.J., Jr., Sholar, C.J., and George, J.R., 1992, Quality-assurance plan for the analysis of fluvial sediment by 

laboratories of the U.S. Geological Survey: U.S. Geological 

Survey Open-File Report 91–467, 37 p. (Also available at 

http://pubs.usgs.gov/of/1991/0467/report.pdf.)

Morel, F.M.M., Kraepiel, A.M.L., and Amyot, Marc, 1998, 

The chemical cycle and bioaccumulation of mercury: 

Annual Review of Ecology and Systematics, v. 29, p. 543–

566.
38 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Neils, David, 2007, NH benthic index of biotic integrity (B–

IBI) for wadeable streams—2006 threshold modification to 

account for natural variation: New Hampshire Department 

of Environmental Services, 39 p., accessed January 8, 2013, 

at http://des.nh.gov/organization/divisions/water/wmb/

swqa/2006/documents/appendix33.pdf.

New Hampshire Department of Environmental Services, 

2004, Biomonitoring program protocols: New Hampshire 

Department of Environmental Services, accessed January 

8, 2013, at http://des.nh.gov/organization/divisions/water/

wmb/biomonitoring/documents/protocols.pdf.

Nobis Engineering, 2009, Appendix B—Fish sampling plan 

and biological sampling plan, in Quality assurance project 

plan, ecological investigation, chloralkali facility (former) 

superfund site, Berlin, New Hampshire: U.S. Environmental 

Protection Agency Task Order 0013–RI–CO–01BQ, Remedial Action Contract EP–S1–06–03 [variously paged].

Nobis Engineering, 2011, Appendix A—Ecological investigation QAPP sampling SOP reference S–3, Standard operating 

procedure tree swallow sampling and tissue processing, in

Quality assurance project plan, ecological investigation, 

chloralkali facility (former) superfund site, Berlin, New 

Hampshire: U.S. Environmental Protection Agency Task 

Order 0013–RI–CO–01BQ, Remedial Action Contract EP–

S1–06–03 [variously paged].

Olson, M.L., and DeWild, J.F., 1999, Techniques for the 

collection and species-specific analysis of low levels of 

mercury in water, sediment, and biota, in U.S. Geological 

Survey Toxic Substances Hydrology Program—Proceedings 

of the technical meeting, Charleston, South Carolina, 

March 8–12, 1999: U.S. Geological Survey WaterResources Investigations Report 99–4018B, p. 191–200. 

(Also available at http://toxics.usgs.gov/pubs/wri99-4018/

Volume2/sectionB/2305_Olson/.)

Olund, S.D., DeWild, J.F., Olson, M.L., and Tate, M.T., 2004, 

Methods for the preparation and analysis of solids and 

suspended solids for total mercury: U.S. Geological Survey 

Techniques and Methods, book 5, chap. A8, 23 p. (Also 

available at http://pubs.usgs.gov/tm/2005/tm5A8/.)

Parker, J.L., and Bloom, N.S., 2005, Preservation and storage 

techniques for low-level aqueous mercury speciation: Science of the Total Environment, v. 337, nos. 1–3, p. 253–263.

Sample, B.E., Opresko, D.M., and Suter, G.W., 1996, Toxicological benchmarks for wildlife, 1996: Oak Ridge, Tenn., 

Oak Ridge National Laboratory, Publication ES/ER/TM–86/

R3, 43 p.

Scudder, B.C., Chasar, L.C., Wentz, D.A., Bauch, N.J., 

Brigham, M.E., Moran, P.W., and Krabbenhoft, D.P., 2009, 

Mercury in fish, bed sediment, water from streams across 

the United States, 1998–2005: U.S. Geological Survey 

Scientific Investigations Report 2009–5109, 74 p. (Also 

available at http://pubs.usgs.gov/sir/2009/5109/.)

Shanley, J.B., Kamman, N.C., Clair, T.A., and Chalmers, 

A.T., 2005, Physical controls on total and methylmercury 

concentrations in streams and lakes of northeastern USA: 

Ecotoxicology, v. 14, p. 125–134.

Shelton, L.R., and Capel, P.D., 1994, Guidelines for collecting 

and processing samples of stream bed sediment for analysis 

of trace elements and organic contaminants for the National 

Water-Quality Assessment Program: U.S. Geological 

Survey Open-File Report 94–458, 20 p. (Also available at 

http://water.usgs.gov/nawqa/pnsp/pubs/ofr94-458/.)

Slowey, A.J., 2010, Rate of formation and dissolution of 

mercury sulfide nanoparticles—The dual role of natural 

organic matter: Geochimica et Cosmochimica Acta, v. 74, 

p. 4693–4708.

Sunderland, E.M., Gobas, F.A.P.C., Branfireun, B.A., and 

Heyes, Andrew, 2006, Environmental controls on the 

speciation and distribution of mercury in coastal sediments: 

Marine Chemistry, v. 102, p. 111–123.

U.S. Environmental Protection Agency, 1995, Great Lakes 

water quality initiative technical support document for 

wildlife criteria: U.S. Environmental Protection Agency 

820–B95–009, 53 p.

U.S. Environmental Protection Agency, 2000, Methods for 

measuring the toxicity and bioaccumulation of sedimentassociated contaminants with freshwater invertebrates 

(2d ed.): U.S. Environmental Protection Agency EPA/600–

R–99/064, 192 p.

U.S. Environmental Protection Agency, 2001a, Acute (96-

hour) reference toxicity test methods for Hyalella azteca

and Chironomous tentans: U.S. Environmental Protection 

Agency, Biology Section, Standard Operating Procedure 

[variously paged].

U.S. Environmental Protection Agency, 2001b, Appendix to 

method 1631—Total mercury in tissue, sludge, sediment, 

and soil by acid digestion and BrCl oxidation: U.S. Environmental Protection Agency EPA–821–R–01–013, 13 p. 

(Also available at http://www.tekran.com/files/EPA_1631_

Appendix_for_Solids.pdf.)

U.S. Environmental Protection Agency, 2001c, Water quality 

criterion for protection of human health—Methylmercury: 

U.S. Environmental Protection Agency Technical Report 

EPA/823/R–01/001 [variously paged].
Selected References 39

U.S. Environmental Protection Agency, 2002, Method 1631, 

revision E—Mercury in water by oxidation, purge and trap, 

and cold vapor atomic fluorescence spectrometry: U.S. 

Environmental Protection Agency EPA–821–R–02–019, 

38 p. (Also available at http://water.epa.gov/scitech/

methods/cwa/metals/mercury/index.cfm.)

U.S. Environmental Protection Agency, 2005, National priorities list for uncontrolled hazardous waste sites: Federal Register, v. 70, no. 177, September 14, 2005, p. 54286–54293, 

accessed January 10, 2013, at http://www.gpo.gov/fdsys/

pkg/FR-2005-09-14/pdf/05-18235.pdf.

U.S. Environmental Protection Agency, 2008a, Chronic 

toxicity method for Ceriodaphnia dubia (revision 5.0): 

U.S. Environmental Protection Agency, Biology Section 

Standard Operating Procedure, Office of Environmental 

Measurements and Evaluation, U.S. Environmental Protection Agency, Region 1.

U.S. Environmental Protection Agency, 2008b, Chronic 

toxicity method for Pimephales promelas (revision 6.0): 

U.S. Environmental Protection Agency, Biology Section 

Standard Operating Procedure, Office of Environmental 

Measurements and Evaluation, U.S. Environmental Protection Agency, Region 1.

U.S. Environmental Protection Agency, 2010, Guidance for 

implementing the January 2001 methylmercury water 

quality criterion: Washington D.C., Office of Water, EPA–

823–R–10–001, 209 p., accessed February 4, 2013, at 

http://water.epa.gov/scitech/swguidance/standards/criteria/

aqlife/methylmercury/upload/mercury2010.pdf.

U.S. Geological Survey, 2005, National field manual for the 

collection of water-quality data: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

46 p.

Weston Solutions, Inc., 2005, Site Investigation Report—

Former Chlor Alkali Facility below Saw Mill Dam: Berlin, 

N.H., February 10, 2004, 203 p.

Wilde, F.D., 2008, Field measurements: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6, accessed January 15, 2013, at 

http://pubs.water.usgs.gov/twri9A6/.

Xianchao, Y., Chandrasekhar, T.M., and Tate, K., 2005, 

Analysis of methylmercury in sediment and tissue by 

KOH/CH3OH digestion followed by aqueous phase ethylation: Florida Department of Environmental Protection 

HG–003–2.2.

Yeardley, R.B., Jr., Lazorchak, J.M., and Paulsen, S.G., 1998, 

Elemental fish tissue contamination in northeastern U.S. 

lakes—Evaluation of an approach to regional assessment: 

Environmental Toxicology and Chemistry, v. 17, no. 9, 

p. 1875–1884.

Zimmerman, M.J., Massey, A.J., and Campo, K.W., 2005, 

Pushpoint sampling for defining spatial and temporal 

variations in contaminant concentrations in sediment 

pore water near the ground-water/surface water interface: 

U.S. Geological Survey Scientific Investigations Report 

2005–5036, 70 p. (Also available at http://pubs.usgs.gov/

sir/2005/5036/.)
THIS PAGE INTENTIONALLY LEFT BLANK
Tables 2, 4, 5, and 6
42 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire Table 2. Summary of methods used for analysis of sediment, pore water, surface water, and biota from the Androscoggin River, Coos County, New Hampshire.—Continued [USGS, U.S. Geological Survey; NRP, National Research Program; USEPA, U.S. Environmental Protection Agency; NERL, New England Regional Laboratory] Notation Type of data Collection period Source of data Method and (or) method citation Sediment mercury parameters THg Total mercury 2009 Als Laboratory Group, Salt Lake City, Utah ILM05.4, USEPA (2006). 2010 USGS NRP Laboratory, Menlo Park, Calif. Marvin-DiPasquale and others (2011). MeHg Methylmercury 2009 Columbia Analytical Services, Kelso, Wash. 1630, USEPA (1998). 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011). Hg(II)R Inorganic reactive mercury 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011). Hg(II)KOH 1M potassium hydroxide (KOH)-extractable mercury 2009 Columbia Analytical Services Bloom and others (2003). THg, F1 thru F5 Sequential extraction 2010 USGS NRP Laboratory Bloom and others (2003).

kmeth MeHg production potential rate constant 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011).MPP MeHg production potential rate (calculated) 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011).

Sediment nonmercury parameters

TAL metals Target analyte list metals 2009 Als Laboratory Group ILM05.4, USEPA (2006).

SEM metals Simultaneously extractable metals 2009 Columbia Analytical Services SW6010, USEPA (1991).AVS Acid volatile sulfur 2009 Columbia Analytical Services Draft 1991, USEPA (1991).Dioxin/furans Dioxin and furans 2009 SGS Environmental, Wilmington, N.C. SW8290, USEPA (2005).PCB Polychlorinated biphenyl 2009 SGS Environmental CBC0.10, USEPA (2007).Pesticides Pesticides 2009 Columbia Analytical Services SW8081, USEPA (2007).SVOCs Semivolital organic compounds 2009 Columbia Analytical Services SW8270, USEPA (2007).H. azteca toxicity Hyalella azteca survival and biomass 2009, 2010 EnviroSystems, Inc., Hampton, N.H. 100.4 and 100.5, USEPA (2000).

C. dilutus toxicity Chironomus dilutus survival and biomass 2009, 2010 EnviroSystems, Inc. 100.4 and 100.5, USEPA (2000).TRS Total reduced sulfur 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).Fe(II)AE Acid extractable ferrous iron (Fe(II)) 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

Fe(III)a Amorphous (poorly crystalline) ferric iron (Fe(III)) 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).Fe(III)c Crystalline ferric iron (Fe(III)) 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).%LOI Percentage of weight loss on ignition 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).TC Total carbon 2010 USGS NRP Laboratory Kendall and others (2001).

TN Total nitrogen 2010 USGS NRP Laboratory Kendall and others (2001).

TOC Total organic carbon 2009 Columbia Analytical Services SW9060, USEPA (2007).

2010 USGS NRP Laboratory Kendall and others (2001).

δ13C Carbon 13 (13C) isotope 2010 USGS NRP Laboratory Kendall and others (2001).

δ15N Nitrogen 15 (15N) isotope 2010 USGS NRP Laboratory Kendall and others (2001).
Table 2 43

Table 2. Summary of methods used for analysis of sediment, pore water, surface water, and biota from the Androscoggin River, Coos County, New Hampshire.—Continued[USGS, U.S. Geological Survey; NRP, National Research Program; USEPA, U.S. Environmental Protection Agency; NERL, New England Regional Laboratory]

Notation Type of data Collection period Source of data Method and (or) method citation

Sediment nonmercury parameters—Continued

BD Bulk density 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

%dry wt Percent dry weight 2009 Columbia Analytical Services APHA-AWWA-WPCF (1992).

2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

%fines Percent grain size (< 74 micrometers (μm)) 2009 Columbia Analytical Services ASTM D422, Plumb (1981), USEPA 

(1996).

Percent grain size (< 63 μm) 2010 USGS NRP Laboratory Matthes and others (1992).

Eh Oxidation-reduction potential 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

pH pH 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

Pore-water mercury parameters

pw.THg Total mercury 2009 Columbia Analytical Services E1631, USEPA (2001, 2002).

2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011).

pw.MeHg Methylmercury 2009 Columbia Analytical Services 1630, USEPA (1998).

2010 USGS NRP Laboratory Marvin-DiPasquale and others (2011).

pw.Hg(II)KOH 1M KOH extractable mercury 2009 Columbia Analytical Services Bloom (2009).

Pore-water nonmercury parameters

TAL metals Target analyte list metals 2009 Als Laboratory Group ILM05.4, USEPA (2006).pw.SO4 Sulfate 2009 Columbia Analytical Services E300.0, USEPA (1982).

2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).

pw.Fe(II) Ferrous iron 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).pw.Cl Chloride 2010 USGS NRP Laboratory Marvin-DiPasquale and others (2008).C. tentans toxicity Chironomus tentans survival 2009, 2010 USEPA NERL, Chelmsford, Mass. Acute 96-hour bioassay, USEPA (2001).H. azteca toxicity Hyalella azteca survival 2009, 2010 USEPA NERL Acute 96-hour bioassay, USEPA (2001).

pw.DOC Dissolved organic carbon 2009 Columbia Analytical Services SW9060, USEPA (2007).

2010 USGS NRP Laboratory

pw.Eh Oxidation-reduction potential 2009, 2010 USGS field parameter Wilde (2008).

pw.pH pH 2009, 2010 USGS field parameter Wilde (2008).
44 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire Table 2. Summary of methods used for analysis of sediment, pore water, surface water, and biota from the Androscoggin River, Coos County, New Hampshire.—Continued [USGS, U.S. Geological Survey; NRP, National Research Program; USEPA, U.S. Environmental Protection Agency; NERL, New England Regional Laboratory] Notation Type of data Collection period Source of data Method and (or) method citation Surface-water mercury parameters THg Total mercury 2009 Columbia Analytical Services E1631, USEPA (2001, 2002). MeHg Methylmercury 2009 Columbia Analytical Services 1630, USEPA (1998). Hg(II)KOH 1M KOH-extractable mercury 2009 Columbia Analytical Services Bloom (2009). Surface-water nonmercury parameters TAL metals Target analyte list metals 2009 Als Laboratory Group ILM05.4, USEPA (2006). SO4 Sulfate 2009 Columbia Analytical Services E300.0, USEPA (1982). C. dubia toxicity Ceriodaphnia dubia survival & reproduction 2009 USEPA NERL Chronic 7-day bioassay, USEPA (2008a,b). P. promelas toxicity Pimephales promelas survival & biomass 2009 USEPA NERL Chronic 7-day bioassay, USEPA (2008a,b). TOC Total organic carbon 2009 Columbia Analytical Services SW9060, USEPA (2007).

Eh Oxidation-reduction potential 2010 USGS field parameter Wilde and others (2005).pH pH 2009, 2010 USGS field parameter Wilde and others (2005).

Biota mercury parameters

THg Total mercury 2009 Columbia Analytical Services E1631, USEPA (2001, 2002).

2010, 2011 USEPA NERL Milestone Inc. Direct Mercury Analyzer 

operation manual (2008).

Biota nonmercury parameters

Invertebrate assemblages 2009 Lotic Inc., Unity, Maine Neils (2007); New Hampshire Department 

of Environmental Services (2004).
Table 4 45

Table 4. Wilcoxon rank sum test comparing results upstream and downstream from a former chloralkali site on the Androscoggin River in Berlin, New Hampshire.—Continued[The nonparametric Wilcoxon rank sum (WRS) test comparison of medians grouped either upstream (reference, AR1 and (or) AR2) or downstream from a former chloralkali site (AR3 to AR9). The first quartile (25th percentile (%)), median (50th %), and third quartile (75th %) are shown, along with results from all mercury metric comparisons. Only significant results for sediment and pore-water nonmercury metrics are shown. Parameter notations are listed in table 2. dw, dry weight; EPT, Ephemeroptera, Plecoptera, Trichoptera; g/cm3, grams per cubic centimeter; L/kg, liters per kilogram; μm, micrometer; mg, 

milligrams; mg/g, milligrams per gram; mg/kg, milligrams per kilogram; mL/cm3, milliliters per cubic centimeter; N, (number of observations); ng/g, nanograms per gram; ng/L, nanograms per liter; NS, nonsignificant differences between groupings at a probability level of p less than 0.05; pg/g/d, picograms per gram per day; ww, wet weight; <, less than; †, significant differences between groupings at a probability 

level of p less than 0.05]

Media Reference stream reach Downstream stream reaches

WRS

Parameter Units of measurement Years 25th % Median 75th % N 25th % Median 75th % N

Sediment mercury parameters

THg ng/g dw 2009, 2010 22 30 69 (11) 89 114 184 -60 †

Hg(II)R ng/g dw 2010 0.09 0.11 0.13 (8) 0.14 0.18 0.27 -52 †

%Hg(II)R % of THg 2010 0.37 0.46 0.53 (8) 0.08 0.15 0.23 -52 †MeHg ng/g dw 2009, 2010 0.21 0.23 0.47 (5) 0.65 0.96 1.26 -21 †

%MeHg % of THg 2009, 2010 1.26 1.4 1.54 (2) 0.47 0.6 0.97 -15 NS

kmeth per day 2010 0.0083 0.0087 0.009 (2) 0.0056 0.0095 0.0149 -13 NS

MPP pg/g/d dw 2010 0.64 0.79 0.95 (2) 1.03 2.11 3.68 -13 NS

Kd[THg] L/kg 2010 4.47 4.61 4.75 (2) 4.53 4.88 5.07 -13 NS

Kd[MeHg] L/kg 2010 3.26 3.3 3.33 (2) 3.01 3.24 3.5 -13 NS

Pore-water mercury parameters

pw.THg ng/L 2009, 2010 0.26 0.7 1.35 (5) 1.15 1.72 5.93 -20 NS

pw.MeHg ng/L 2009, 2010 0.06 0.1 0.1 (5) 0.09 0.3 0.59 -20 †

pw%MeHg % of THg 2009, 2010 10.83 21.07 29.36 (3) 12.02 23.98 38.44 -15 NS

Biota total mercury

Oligochaete ng/g ww 2009 18 20 22 (5) 25 31 40 -19 †

Crayfish ng/g ww 2009, 2011 50 59 64 (12) 72 89 110 -39 †

WS ng/g ww 2009, 2011 119 132 135 (7) 136 208 278 -19 †

SMB ng/g ww 2009, 2011 390 418 421 (10) 511 587 638 -38 †

Bat fur ng/g ww 2010 4,369 5,062 6,372 (11) 11,920 56,830 118,400 -27 †

Bat blood ng/g ww 2010 166 233 312 (4) 318 428 566 -12 NS

Swallow feather-adult ng/g ww 2010 996 1,128 1,324 (14) 997 1,417 1,644 -20 NS

Swallow feather-nestling ng/g ww 2010 1,059 1,309 1,447 (13) 1,644 1,647 2,118 -9 †

Swallow blood-adult ng/g ww 2010 288 306 343 (11) 433 520 585 -14 †

Swallow blood-nestling ng/g ww 2010 30 40 40 (13) 42 53 73 -9 †

Swallow egg ng/g ww 2010 495 527 568 (13) 607 773 803 -15 †

Sediment sequential extractions

F1: water ng/g dw 2010 0.03 0.03 0.04 (2) 0.02 0.05 0.07 -13 NS

% of THg 2010 0.09 0.1 0.11 (2) 0.01 0.02 0.03 -13 NS
46 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire Table 4. Wilcoxon rank sum test comparing results upstream and downstream from a former chloralkali site on the Androscoggin River in Berlin, New Hampshire.—Continued [The nonparametric Wilcoxon rank sum (WRS) test comparison of medians grouped either upstream (reference, AR1 and (or) AR2) or downstream from a former chloralkali site (AR3 to AR9). The first quartile (25th percentile (%)), median (50th %), and third quartile (75th %) are shown, along with results from all mercury metric comparisons. Only significant results for sediment and pore-water nonmercury metrics are shown. Parameter notations are listed in table 2. dw, dry weight; EPT, Ephemeroptera, Plecoptera, Trichoptera; g/cm3, grams per cubic centimeter; L/kg, liters per kilogram; μm, micrometer; mg, milligrams; mg/g, milligrams per gram; mg/kg, milligrams per kilogram; mL/cm3, milliliters per cubic centimeter; N, (number of observations); ng/g, nanograms per gram; ng/L, nanograms per liter; NS, non- significant differences between groupings at a probability level of p less than 0.05; pg/g/d, picograms per gram per day; ww, wet weight; <, less than; †, significant differences between groupings at a probability level of p less than 0.05] Media Reference stream reach Downstream stream reaches WRS Parameter Units of measurement Years 25th % Median 75th %

N 25th % Median 75th %

N

Sediment sequential extractions—Continued

F2: 0.1 M acetic acid ng/g dw 2010 0.02 0.02 0.03 (2) 0.02 0.02 0.03 -13 NS

% of THg 2010 0.07 0.08 0.09 (2) 0.01 0.02 0.02 -13 †

F3: 1.0 M KOH ng/g dw 2010 23.4 27.3 31.3 (2) 56.3 70.9 111 -13 †

% of THg 2010 87.2 87.6 88.1 (2) 38.2 45 58.9 -13 †

F4: 12 M HNO3 ng/g dw 2010 2.69 2.98 3.26 (2) 43.9 71.3 87.2 -13 †

% of THg 2010 9.36 9.83 10.3 (2) 39.3 49.9 55.8 -13 †

F5: Aqua Regia ng/g dw 2010 0.62 0.74 0.86 (2) 3.1 3.9 7.2 -13 †

% of THg 2010 2.29 2.35 2.4 (2) 2.18 2.65 5.77 -13 NS

Sediment nonmercury parameters

Fe(II)AE mg/g dw 2010 3.92 4.39 4.86 (2) 1.66 2.29 3.07 -13 †

AVS mg/kg dw 2009 17.8 17.8 25.7 (3) 2.07 2.41 3 -8 †

Bulk density g/cm3 ww 2010 1.32 1.37 1.46 (8) 1.47 1.55 1.67 -52 †

% fines % <74 μm 2009 55 56.3 60 (3) 25.5 32.2 42.1 -8 †

% <63 μm 2010 63.1 72.1 75.3 (8) 27.9 44.8 56.4 -52 †

Porosity mL/cm3 ww 2010 0.64 0.72 0.74 (8) 0.53 0.59 0.64 -52 †

pct.DW % of ww 2009, 2010 43 46 56 (11) 56 61 68 -60 †

Sediment toxicity

Hyalella.azteca.survival

% 2009, 2010 78 80 80 (5) 74 79 85 -21 NS

Hyalella.azteca.biomass mg dw 2009, 2010 0.38 0.39 0.4 (5) 0.34 0.43 0.5 -21 NS

Chironomus.dilutus.survival

% 2009, 2010 70 76 83 (5) 61 75 80 -21 NS

Chironomus.dilutus.biomass mg dw 2009, 2010 0.44 0.5 1.25 (5) 0.3 1.15 1.29 -21 NS

Pore-water toxicity

Chironomus.tentans.survival

% 2009, 2010 80 90 100 (5) 80 90 100 -21 NS

Hyalella.azteca.survival

% 2009, 2010 70 80 80 (5) 90 100 100 -21 †

Invertebrate metrics

Abundance 2009 288 316 486 (3) 148 604 1,020 -12 NS

Total taxa 2009 14 14 15 (3) 9.9 12 13 -12 NS

EPT taxa 2009 16 16 16 (3) 13 15 17 -12 NS
Table 5 47

Table 5. Kruskal-Wallis rank sum test results comparing data grouped by sample distance from a former chloralkali site on the Androscoggin River in Berlin, New Hampshire.

—Continued

[The nonparametric Kruskal-Wallis rank sum (KWRS) test comparison of medians grouped by distance from a former chloralkali site. The reference reach (AR2) is 16 kilometers (km) upstream from the former chloralkali site; near-stream reaches (AR3–AR6) are 0 to 4 km downstream from the former chloralkali site; far-stream reaches (AR7–AR9) are 8 to 16 km downstream from the former chloralkali site. The first quartile (25th percentile (%)), median (50th %), and third quartile (75th %) are shown, along with results from all mercury metric comparisons. Only significant results for nonmercury metrics are shown. Tukey multiple-comparison test was used to determine rankings on data KWRS indicated as significant. Letters A and B, indicate which medians are different: A medians are statistically different than B medians, and AB medians are not statistically different than A or B. Parameter notation definitions are listed in table 2. dw, dry weight; EPT, Ephemeroptera, Plecoptera, Trichoptera; g/cm3, grams per cubic centimeter; L/kg, liters 

per kilogram; mg, milligrams; mL/cm3, milliliters per cubic centimeter; μm, micrometers; mv, millivolts; N, (number of observations); ng/g, nanograms per gram; ng/L, nanograms per liter; NS, nonsignificant 

differences between groupings at a probability level of p less than 0.05; pg/g/d, picograms per gram per day; THg, total mercury; ww, wet weight; <, less than; †, significant differences between groupings at a probability level of p less than 0.05]

Media Reference stream reach Near stream reaches Far stream reaches

KWRS

Parameter

Units of 

measurement Year 25th % Median 75th % N 25th % Median 75th % N 25th % Median 75th % N

Sediment mercury parameters

THg ng/g dw 2009, 2010 21 26 B 30 (11) 84 117 A 240 (25) 82 111 AB 160 (35) †

Hg(II)R ng/g dw 2010 0.09 0.11 B 0.13 (8) 0.12 0.16 B 0.22 (24) 0.14 0.21 A 0.36 (28) †

%Hg(II)R % of THg 2010 0.37 0.46 AB 0.53 (8) 0.07 0.12 B 0.18 (24) 0.13 0.17 A 0.32 (28) †MeHg ng/g dw 2009, 2010 0.16 0.22 B 0.35 (5) 0.28 0.74 AB 1.39 (7) 0.71 0.98 A 1.23 (14) †

%MeHg % of THg 2009, 2010 1.26 1.40 1.54 (2) 0.31 0.53 0.94 (7) 0.51 0.69 0.99 (8) NS

kmeth per day 2010 0.01 0.01 0.01 (2) 0.01 0.01 0.02 (6) 0.00 0.01 0.01 (7) NS

MPP pg/g/d dw 2010 0.64 0.79 0.95 (2) 1.42 2.39 3.96 (6) 0.34 1.27 3.68 (7) NS

Kd[THg] L/kg 2010 4.47 4.61 4.75 (2) 4.50 4.71 4.93 (6) 4.77 4.88 5.08 (7) NS

Kd[MeHg] L/kg 2010 3.26 3.30 3.33 (2) 2.92 3.20 3.37 (6) 3.04 3.24 3.65 (7) NS

Pore-water mercury parameters

pw.THg ng/L 2009, 2010 0.26 0.70 1.35 (5) 1.15 1.32 8.68 (7) 0.94 1.72 2.30 (13) NS

pw.MeHg ng/L 2009, 2010 0.06 0.10 B 0.10 (5) 0.19 0.52 A 1.90 (7) 0.07 0.29 AB 0.55 (13) †

pw%MeHg % of THg 2009, 2010 10.8 21.1 29.4 (3) 17.7 30.2 38.7 (6) 7.97 24.0 27.3 (9) NS

Biota total mercury

Oligochaete ng/g ww 2009 18.3 19.5 B 21.6 (5) 24.7 32.2 AB 40.6 (8) 27.1 31.3 A 38.7 (11) †

Crayfish ng/g ww 2009, 2011 50.0 59.3 B 64.3 (12) 76.5 95.0 A 111 (25) 69.2 74.1 AB 105 (14) †

White sucker ng/g ww 2009, 2011 119 132 B 134 (7) 99.2 153 B 211 (10) 182 251 A 343 (9) †

Smallmouth bass ng/g ww 2009, 2011 390 418 B 421 (10) 393 528 B 604 (21) 583 629 A 639 (17) †

Sediment sequential extractions

F1: water ng/g dw 2010 0.03 0.03 0.04 (2) 0.02 0.04 0.44 (6) 0.03 0.05 0.06 (7) NS

% of THg 2010 0.09 0.10 0.11 (2) 0.01 0.02 0.09 (6) 0.02 0.02 0.03 (7) NS

F2: 0.1 M acetic acid ng/g dw 2010 0.02 0.02 0.03 (2) 0.02 0.04 0.05 (6) 0.02 0.02 0.02 (7) NS

% of THg 2010 0.07 0.08 0.09 (2) 0.01 0.02 0.03 (6) 0.01 0.01 0.02 (7) NS

F3: 1.0 M KOH ng/g dw 2010 23.4 27.3 31.3 (2) 63.5 82.6 106 (6) 55.7 67.7 92.2 (7) NS

% of THg 2010 87.2 87.6 88.1 (2) 33.8 47.4 67.7 (6) 41.2 45.0 54.6 (7) NS
48 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire Table 5. Kruskal-Wallis rank sum test results comparing data grouped by sample distance from a former chloralkali site on the Androscoggin River in Berlin, New Hampshire. —Continued [The nonparametric Kruskal-Wallis rank sum (KWRS) test comparison of medians grouped by distance from a former chloralkali site. The reference reach (AR2) is 16 kilometers (km) upstream from the former chloralkali site; near-stream reaches (AR3–AR6) are 0 to 4 km downstream from the former chloralkali site; far-stream reaches (AR7–AR9) are 8 to 16 km downstream from the former chloralkali site. The first quartile (25th percentile (%)), median (50th %), and third quartile (75th %) are shown, along with results from all mercury metric comparisons. Only significant results for nonmercury metrics are shown. Tukey multiple-comparison test was used to determine rankings on data KWRS indicated as significant. Letters 

A and B, indicate which medians are different: A medians are statistically different than B medians, and AB 

medians are not statistically different than A or B. Parameter notation definitions are listed in table 2. dw, dry weight; EPT, Ephemeroptera, Plecoptera, Trichoptera; g/cm3, grams per cubic centimeter; L/kg, liters 

per kilogram; mg, milligrams; mL/cm3, milliliters per cubic centimeter; μm, micrometers; mv, millivolts; N, (number of observations); ng/g, nanograms per gram; ng/L, nanograms per liter; NS, nonsignificant 

differences between groupings at a probability level of p less than 0.05; pg/g/d, picograms per gram per day; THg, total mercury; ww, wet weight; <, less than; †, significant differences between groupings at a probability level of p less than 0.05]

Media Reference stream reach Near stream reaches Far stream reaches

KWRS

Parameter

Units of 

measurement Year 25th % Median 75th % N 25th % Median 75th % N 25th % Median 75th % N

Sediment sequential extractions—Continued

F4: 12 M HNO3 ng/g dw 2010 2.69 2.98 3.26 (2) 48.0 78.1 145 (6) 53.1 66.6 82.5 (7) NS

% of THg 2010 9.36 9.83 10.3 (2) 30.3 46.4 61.3 (6) 43.3 50.0 53.7 (7) NS

F5: aqua regia ng/g dw 2010 0.62 0.74 0.86 (2) 3.15 3.36 26.6 (6) 3.49 5.02 6.53 (7) NS

% of THg 2010 2.29 2.35 2.40 (2) 2.05 2.40 5.13 (6) 2.42 3.33 4.68 (7) NS

Sediment nonmercury parameters

Sediment Eh mv 2010 86 104 AB 108 (2) 22 85

B 121 (24) 91 136

A 175 (28) †

Bulk density g/cm3 ww 2010 1.32 1.37

B 1.46 (8) 1.48 1.55

A 1.69 (24) 1.44 1.54 AB 1.66 (28) †

% fines % <63 μm 2010 63 72

A 75 (8) 26 47

B 56 (24) 29 42 

B 57 (28) †

Porosity mL/cm3 ww 2010 0.64 0.72

A 0.74 (8) 0.52 0.59

B 0.64 (24) 0.53 0.59 

B 0.65 (28) †

pct.DW % of wet wt 2009, 2010 43 46

B 56 (11) 56 61

A 70 (25) 56 61 

A 67 (35) †

Sediment toxicity

H.azteca survival

% 2009, 2010 78 80 80 (5) 77 79 86 (7) 72 80 84 (14) NS

H.azteca biomass mg dw 2009, 2010 0.38 0.39 0.40 (5) 0.43 0.43 0.49 (7) 0.33 0.42 0.50 (14) NS

C.dilutus survival

% 2009, 2010 70 76 83 (5) 66 80 88 (7) 60 73 76 (14) NS

C.dilutus biomass mg dw 2009, 2010 0.44 0.50 1.25 (5) 1.25 1.29 1.48 (7) 0.30 0.67 1.19 (14) NS

Pore-water toxicity

C.tentans survival

% 2009, 2010 80 90 100 (5) 48 85 95 (7) 83 90 99 (14) NS

H.azteca survival

% 2009, 2010 70 80 80 (5) 95 100 100 (7) 90 95 100 (14) NS

Invertebrate metrics

Abundance 2009 288 316 486 (3) 69.5 587 1,510 (6) 322 604 890 (6) NS

Total taxa 2009 14 14 15 (3) 9.4 11 13 (6) 11 13 13 (6) NSEPT taxa 2009 16 16 16 (3) 13 14 15 (6) 13 17 19 (6) NS
Table 6 49

Table 6. Sequential extraction results for surface sediment, Androscoggin River, Coos County, New Hampshire.

—Continued

[Surface sediment encompasses 0- to 10-centimeter (cm) interval. See table 3 for details on the specific fraction number (F#) and associated dominant mercury species extracted. THg, total mercury; ng/g, nanograms per gram; --, no data]

F#

THg, 

in ng/g dry weight THg, average, 

in percent Replicate 1 Replicate 2 Average

AR2–4

F1 0.02 0.07 0.05 0.12

F2 0.03 0.02 0.03 0.07

F3 34.2 36.2 35.2 88.6

F4 3.79 3.29 3.54 8.9

F5 0.96 1 0.98 2.46

Total 39 40.5 39.8 100

AR2–5

F1 0.02 -- 0.02 0.08

F2 0.02 -- 0.02 0.09

F3 19.4 -- 19.4 86.8

F4 2.41 -- 2.41 10.8

F5 0.5 -- 0.5 2.24

Total 22.4 -- 22.4 100

AR4–1

F1 0.83 0.96 0.89 0.11

F2 0.03 0.07 0.05 0.01

F3 62.8 57.6 60.2 7.64

F4 338 1,020 680 86.3

F5 37.8 56.4 47.1 5.97

Total 439 1,140 788 100

AR4–2

F1 0.56 0.59 0.58 0.44

F2 0.02 0.02 0.02 0.02

F3 35.2 47.9 41.6 31.9

F4 78.5 91.4 84.9 65.1

F5 3.66 3.17 3.41 2.62

Total 118 143 130 100

AR5–1

F1 0.02 -- 0.02 0.01

F2 0.03 -- 0.03 0.02

F3 111 -- 111 71.9

F4 40.2 -- 40.2 26.1

F5 3.1 -- 3.1 2.01

Total 154 -- 154 100

AR5–2

F1 0.05 -- 0.05 0.01

F2 0.1 -- 0.1 0.03

F3 131 -- 131 39.7

F4 165 -- 165 49.9

F5 34.3 -- 34.3 10.4

Total 331 -- 331 100
50 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Table 6. Sequential extraction results for surface sediment, Androscoggin River, Coos County, New Hampshire.

—Continued

[Surface sediment encompasses 0- to 10-centimeter (cm) interval. See table 3 for details on the specific fraction number (F#) and associated dominant mercury species extracted. THg, total mercury; ng/g, nanograms per gram; --, no data]

F#

THg, 

in ng/g dry weight THg, average, 

in percent Replicate 1 Replicate 2 Average

AR6–2

F1 0.03 -- 0.03 0.03

F2 0.04 -- 0.04 0.05

F3 73.5 -- 73.5 77.6

F4 19.1 -- 19.1 20.2

F5 2.06 -- 2.06 2.18

Total 94.7 -- 94.7 100

AR6–3

F1 0.01 -- 0.01 0.01

F2 0.01 -- 0.01 0.01

F3 91.8 -- 91.8 55.2

F4 71.3 -- 71.3 42.8

F5 3.3 -- 3.3 1.98

Total 166 -- 166 100

AR7–1

F1 0.07 -- 0.07 0.05

F2 0.02 -- 0.02 0.01

F3 56.3 -- 56.3 38.2

F4 87.2 -- 87.2 59.1

F5 3.9 -- 3.9 2.65

Total 147 -- 147 100

AR7–2

F1 0.05 -- 0.05 0.03

F2 0.02 -- 0.02 0.01

F3 114 -- 113.5 69.5

F4 43.8 -- 43.8 26.8

F5 5.85 -- 5.85 3.58

Total 163 -- 163 100

AR8–4

F1 0.02 -- 0.02 0.01

F2 0.03 -- 0.03 0.02

F3 70.9 -- 70.9 50.4

F4 66.6 -- 66.6 47.4

F5 3.08 -- 3.08 2.19

Total 141 -- 141 100

AR8–5

F1 0.03 -- 0.03 0.02

F2 0.02 -- 0.02 0.02

F3 55.1 -- 55.1 44.1

F4 62.4 -- 62.4 50

F5 7.2 -- 7.2 5.77

Total 125 -- 125 100
Table 6 51

Table 6. Sequential extraction results for surface sediment, Androscoggin River, Coos County, New Hampshire.

—Continued

[Surface sediment encompasses 0- to 10-centimeter (cm) interval. See table 3 for details on the specific fraction number (F#) and associated dominant mercury species extracted. THg, total mercury; ng/g, nanograms per gram; --, no data]

F#

THg, 

in ng/g dry weight THg, average, 

in percent Replicate 1 Replicate 2 Average

AR9–5

F1 0.01 -- 0.01 0.02

F2 0.02 -- 0.02 0.05

F3 28.7 -- 28.7 58.9

F4 19.2 -- 19.2 39.3

F5 0.86 -- 0.86 1.77

Total 48.8 -- 48.8 100

AR9–6

F1 0.05 -- 0.05 0.03

F2 0.02 -- 0.02 0.01

F3 67.7 -- 67.7 45

F4 77.8 -- 77.8 51.7

F5 5.02 -- 5.02 3.33

Total 151 -- 151 100

AR9–7

F1 0.1 -- 0.1 0.02

F2 0.02 -- 0.02 0

F3 120 -- 119.8 24.2

F4 276 -- 276 55.8

F5 98.7 -- 98.7 20

Total 494 -- 494 100
THIS PAGE INTENTIONALLY LEFT BLANK
Appendix 1 53

Appendix 1. Quality Assurance and Control at

the U.S. Geological Survey Laboratory in 

Menlo Park, California

Tables

1–1. Holding times and preservation used for sediment samples collected from the 

Androscoggin River, Coos County, New Hampshire, August 23–27, 2010

1–2. Method blanks and method detection limits used for the study of the Androscoggin 

River, Coos County, New Hampshire

1–3. Laboratory analytical replicate results for sediment and pore-water samples from the 

Androscoggin River, Coos County, New Hampshire, collected August 23–27, 2010

1–4. Matrix spike results for sediment and pore-water samples collected from the 

Androscoggin River, Coos County, New Hampshire, August 23–27, 2010

1–5. Certified reference material recovery results for the study of the Androscoggin River, 

Coos County, New Hampshire
54 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

Appendix 1. Quality Assurance and Control at the U.S. Geological Survey 

Laboratory in Menlo Park, California

Quality assurance (QA) and quality control (QC) results 

for all parameters assayed by the U.S. Geological Survey 

(USGS) Western Region Research Laboratory in Menlo Park, 

Calif., are listed below.

Holding Times

All assays were conducted within the prescribed holding 

times, as established by either the U.S. Environmental 

Protection Agency (USEPA), the U.S. Geological Survey 

(USGS), or peer-reviewed studies from the literature (Horvat 

and others, 1993; Parker and Bloom, 2005; table 1–1). In the 

case of studies published in the literature, the USGS laboratory 

takes a conservative prescribed holding time approach by 

setting sample holding limits lower than the published 

study results.

Blanks

Method blanks were run to assess contamination introduced in the laboratory. In most cases, values from the method 

blanks were below our method detection limit (table 1–2), 

indicating that the methods and equipment used were free of 

(or did not introduce) contamination. The exceptions were for 

pore-water dissolved organic carbon (pw.DOC) and chloride 

(pw.Cl) where small amounts of the analyte were detected.

Laboratory Replicates

Laboratory analytical replicates represent multiple 

samples taken from the same container of site-specific sediment as a measure of both sample homogeneity and laboratory 

reproducibility. At least one analytical replicate was analyzed 

for each sediment and pore-water parameter; the results are 

listed in table 1–3.

Matrix Spike Samples

Matrix spike percent recoveries were evaluated to 

determine acceptable accuracy based on method-specific 

percent recoveries, which are generally set to be 75- to 

125-percent recovery for the laboratory’s control limit 

(table 1–4). Typically when spikes are reported below this 

accepted range, they indicate a low bias, and when reported 

above this range, they indicate a high bias. However, if the 

spike concentration was low compared with the sample 

concentration, a poor recovery is not in itself indicative 

of a QC problem. Further, not all sediment parameters are 

amenable to matrix spikes. For example, the addition of 

mercuric chloride to sediment quickly partitions itself between 

tin-reducible and nonreducible pools and thus cannot be used 

as a reliable matrix spike for the reactive divalent mercury 

(Hg(II)R) assay. Similarly, there is no commercially available 

material that can mimic the operationally defined amorphous 

ferric iron (Fe(III)a

) sediment pool, and thus the Fe(III)a assay 

is not subject to a matrix spike assay.

Certified Reference Material

Certified reference material (CRM) is available for only 

a limited number of the analytes assayed in the study of the 

Androscoggin River, specifically for sediment total mercury 

(THg) and methylmercury (MeHg). Like matrix spikes, 

CRM recoveries were evaluated to determine acceptable 

accuracy based on method-specific percent recoveries, which 

are generally set to be 75 to 125 percent for the laboratory’s 

control limit. CRM recovery results for THg and MeHg are 

listed in table 1–5.
Appendix 2 55

Appendix 2. Surface-Water, Pore-Water, 

Sediment, Invertebrate, and Biota Data

Data in the following tables are for whole (unsieved) streambed-sediment, filtered porewater, and filtered and unfiltered surface-water samples. Pore-water samples were collected 

directly from the streambed using a push-point sampler and peristaltic pump.

Tables

2–1. Sampling dates, and site descriptions for sediment, water, and benthic invertebrate 

samples from the Androscoggin River, Coos County, New Hampshire

2–2. Parameters used in the analysis of surface-water samples from the Androscoggin 

River, Coos County, New Hampshire

2–3. Concentrations of metals in streambed-sediment samples from the Androscoggin 

River, Coos County, New Hampshire

2–4. Parameters used in the analysis of pore-water samples from the Androscoggin River, 

Coos County, New Hampshire

2–5. Concentrations of metals in filtered and unfiltered pore-water samples from the 

Androscoggin River, Coos County, New Hampshire

2–6. Parameters used in the analysis of streambed-sediment samples from the 

Androscoggin River, Coos County, New Hampshire

2–7. Concentrations of metals in streambed-sediment samples from the Androscoggin 

River, Coos County, New Hampshire

2–8. Concentrations of acid volatile sulfide and simultaneously extractable metals in 

streambed-sediment samples from the Androscoggin River, Coos County, New 

Hampshire

2–9. Concentrations of pesticides in streambed-sediment samples from the Androscoggin 

River, Coos County, New Hampshire

2–10. Concentrations of semivolatile organic compounds in streambed-sediment samples 

from the Androscoggin River, Coos County, New Hampshire

2–11. Concentrations of polychlorinated biphenyl compounds in streambed-sediment 

samples from the Androscoggin River, Coos County, New Hampshire

2–12. Concentrations of dioxin and furan compounds in streambed-sediment samples from 

the Androscoggin River, Coos County, New Hampshire

2–13. Results of 7-day toxicity tests for cladoceran and fathead minnow exposed to surface 

water from the Androscoggin River, Coos County, New Hampshire

2–14. Survival rate from 96-hour toxicity tests for amphipod Hyalella azteca and midge 

Chironomus tentans exposed to pore-water from the Androscoggin River, Coos County, 

New Hampshire

2–15. Results of 28-day toxicity tests for amphipod Hyalella azteca and 20-day toxicity tests 

for midge Chironomus dilutus exposed to sediments from the Androscoggin River, 

Coos County, New Hampshire

2–16. Concentrations of total mercury in biota in the Androscoggin River, Coos County, 

New Hampshire

2–17. New Hampshire Department of Environmental Services benthic index of biotic integrity 

for the Androscoggin River, Coos County, New Hampshire
56 Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire

2–18. Benthic invertebrates from the Androscoggin River downstream from Pontook Dam, 

Coos County, New Hampshire

2–19. Benthic invertebrates from the Androscoggin River downstream from Sawmill Dam, 

Coos County, New Hampshire

2–20. Benthic invertebrates from the Androscoggin River downstream from Riverside Dam, 

Coos County, New Hampshire

2–21. Benthic invertebrates from the Androscoggin River downstream from Brown Dam, 

Coos County, New Hampshire

2–22. Benthic invertebrates from the Androscoggin River downstream from Gorham Dam, 

Coos County, New Hampshire
Prepared by the Pembroke, Columbus, and West Trenton 

Publishing Service Centers.

For more information concerning this report, contact:

Office Chief

U.S. Geological Survey

New England Water Science Center

New Hampshire-Vermont Office

331 Commerce Way, Suite 2

Pembroke, NH 03275

dc_nh@usgs.gov

or visit our Web site at:

http://nh.water.usgs.gov
Chalmers and others—Characterization of Mercury Contamination in the Androscoggin River, Coos County, New Hampshire—Open-File Report 2013–1076