U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2007-1240

Legacy Mercury in Alviso Slough, South San Francisco Bay, 

California: Concentration, Speciation and Mobility 
Cover: 

Top—Data Collection at Alviso Slough. Photo by M. Marvin-DiPasquale. 

Bottom Left—Aerial Photo with Alviso Slough emphasized in blue, modified from GoogleEarthTM image. 

Bottom Right—Sediment core sample. Photo by M. Cox. 
ii

Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and 

Mobility 

By Mark Marvin-DiPasquale and Marisa H. Cox 

Open-File Report 2007-1240 

U.S. Department of the Interior 

U.S. Geological Survey 
iii

U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod 

Telephone: 1-888-ASK-USGS 

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov 

Telephone: 1-888-ASK-USGS 

Suggested citation: 

Marvin-DiPasquale, M., Cox, M.H., 2007, Legacy Mercury in Alviso Slough, South San Francisco Bay, 

California: Concentration, Speciation and Mobility: Menlo Park, CA , U.S. Geological Survey, Open-File 

Report number 2007-1240, 98p 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government. 
iv

Contents 

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

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

Purpose and Scope ........................................................................................................................................................ 3

Methods ............................................................................................................................................................................... 4

Study Area and Sample Collection .............................................................................................................................. 4

Initial Post-Collection Sediment Core Processing .................................................................................................... 4

Multi-Sensor Core Logger ......................................................................................................................................... 4

Core Splitting ............................................................................................................................................................... 5

Core Descriptions & Database ................................................................................................................................. 5

Core Sub-Sampling ..................................................................................................................................................... 6

Core Photography and Archiving ............................................................................................................................. 7

Laboratory Analysis ........................................................................................................................................................ 7

Mercury Speciation .................................................................................................................................................... 7

Total Mercury .......................................................................................................................................................... 7

Reactive Mercury ................................................................................................................................................... 7

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

Additional Sediment Characterization .................................................................................................................... 9

Sediment pH ............................................................................................................................................................. 9

Oxidation-Reduction Potential (ORP) .................................................................................................................. 9

Bulk Density, Percent Dry Weight, Porosity and Organic Content ................................................................ 9

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

Sediment and Mercury Inventory and Mobilization Calculations ....................................................................... 10

Sediment Scour Simulation Experiment ................................................................................................................... 11

Results ................................................................................................................................................................................ 13

Sediment Core Descriptions ....................................................................................................................................... 13

Mercury Speciation and Quantification ................................................................................................................... 13

Ancillary Sediment Parameters ................................................................................................................................. 13

Sediment and Mercury Mobilization Estimates ...................................................................................................... 14

Sediment Scour Simulation Experiment ................................................................................................................... 14

Acknowledgments ............................................................................................................................................................ 15

References ......................................................................................................................................................................... 15

Figures ................................................................................................................................................................................ 18

Tables ................................................................................................................................................................................. 31

Appendix A—Sediment core descriptions, Alviso Slough, September 2006 ........................................................ 48
v

Figures 

Figure 1. Map of South San Francisco Bay, Alviso Slough and the New Almaden Mining District .................. 18

Figure 2. Map showing location of Alviso Slough sediment sampling sites .......................................................... 19

Figure 3. Illustration of slough cross section and sediment sampling design ...................................................... 20

Figure 4. Depth profiles of sediment total mercury concentration .......................................................................... 21

Figure 5. Depth profiles of sediment methylmercury concentration ....................................................................... 22

Figure 6. Depth profiles of sediment reactive inorganic mercury as a percentage of total mercury ............... 23

Figure 7. Depth profiles of sediment pH ....................................................................................................................... 24

Figure 8. Depth profiles of sediment oxidation-reduction potential ........................................................................ 25

Figure 9. Depth profiles of sediment organic content ................................................................................................ 26

Figure 10. Depth profiles of sediment grain size ......................................................................................................... 27

Figure 11. Depth profiles of sediment density ............................................................................................................. 28

Figure 12. Depth profiles of sediment magnetic susceptibility ................................................................................ 29

Figure 13. Time course plot of reactive mercury concentrations associated with the slough scour 

simulation experiment ............................................................................................................................................. 30

Tables 

Table 1. Sediment sampling locations, Alviso Slough, September 2006 ................................................................ 31

Table 2. Sediment Mercury Species Concentration .................................................................................................. 32

Table 3. Ancillary Sediment Parameters ...................................................................................................................... 39

Table 4. PWA Transects and Predicted Changes in Slough Cross Sectional Area ............................................. 46

Table 5. Sediment Mobilization Predictions by Slough Segment ............................................................................ 46

Table 6. Mercury Species Current Inventory and Mobilization Predictions by Slough Segment ..................... 47
vi

Conversion Factors 

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) 

Area 

square meter (m2) 0.0002471 acre 

square kilometer (km2) 247.1 acre 

square centimeter (cm2

) 0.001076 square foot (ft2) 

square meter (m2

) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (ft2) 

square kilometer (km2

) 0.3861 square mile (mi2) 

Volume 

cubic centimeter (cm3) 0.06102 cubic inch (in3) 

cubic meter (m3) 35.31 cubic foot (ft3) 

cubic kilometer (km3

) 0.2399 cubic mile (mi3) 

kilometer per hour (km/h) 0.6214 mile per hour (mi/h)

Mass 

gram (g) 0.03527 ounce (oz) 

kilogram (kg) 2.205 pound (lb) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: 

°F=(1.8×°C)+32 

Vertical and horizontal coordinate information is referenced to the World Geodetic System of 1984(WGS 84). 
Legacy Mercury in Alviso Slough, South San 

Francisco Bay, California: Concentration, 

Speciation and Mobility 

By Mark Marvin-DiPasquale and Marisa H. Cox 

Abstract 

Mercury (Hg) is a significant contaminant in the waters, sediment and biota of San Francisco 

Bay, largely resulting from extensive historic regional mining activities. Alviso Slough represents one 

of the most mercury contaminated waterways entering south San Francisco Bay, as it is associated with 

the drainage of the New Almaden mercury mining district. Wetland habitat restoration of former salt 

manufacturing ponds adjacent to Alviso Slough is currently being planned. One management scenario 

being considered is a levee breach between Alviso Slough and Pond A8, which will allow reconnection 

of the salt pond with the tidal slough. This action is projected to increase the tidal prism within Alviso 

Slough and result in some degree of sediment remobilization as the main channel deepens and widens. 

The focus of the current study is to assess: a) the current mercury species composition and concentration 

in sediments within the Alviso Slough main channel and its associated fringing marsh plain, b) how 

much of each mercury species will be mobilized as a result of projected channel deepening and 

widening, and c) potential changes in inorganic ‘reactive’ mercury bioavailability (for conversion to 

toxic methylmercury) associated with the mobilized sediment fraction. The current report details the 

field sampling approach and all laboratory analyses conducted, as well as provides the complete dataset 

associated with this project including a) a quantitative assessment of mercury speciation (total mercury, 

reactive mercury and methylmercury), b) estimates of the quantity of sediment and mercury mobilized 

based on 20-foot and 40-foot levee wall notch scenarios, and c) results from a sediment scour 

experiment examining the changes in the reactive mercury pool under four treatment conditions (high / 

low salinity and oxic / anoxic water). Ancillary sediment data also collected and reported herein include 

bulk density, organic content, magnetic susceptibility, percent dry weight, grain size, pH, oxidationreduction potential, core photography, and detailed lithographic descriptions. 

1
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Introduction 

Mercury (Hg) is a legacy contaminant, mined historically from the California Coast Ranges and 

transported to the Sierra Nevada for use in gold extraction during the Gold Rush era of the mid- to late 

1800’s (Alpers and others, 2005). Mercury enters San Francisco Bay (SFB) from runoff associated with 

the hundreds of abandoned mercury and gold mining sites located around the Bay watershed, as well as 

from the contemporary urban landscape (CRWQCB, 2006). One of the most prolific mercury-producing 

mining areas in North America, located in the hills south of San Jose, California, is the New Almaden 

Mining District, which generated over 3.7x107 kg of mercury between 1845 and 1975 (Cargill and 

others, 1980). The watershed draining the New Almaden Mining District includes the Guadalupe River, 

which ultimately flows into Alviso Slough and South SFB (Figure 1), all of which exhibit elevated 

levels of mercury in surface sediments along this drainage flow path (Conaway and others, 2003; 

Thomas and others, 2002). Estimates of mercury transported annually from the New Almaden region to 

South SFB can range from a few kilograms to hundreds of kilograms per year, depending largely on the 

inter-annual variation in rainfall, as most of the mercury is associated with sediments that are mobilized 

during episodic high flow events (McKee and others, 2005; Thomas and others, 2002). 

In 2003, the State of California and the U.S. Government purchased over 16,000 acres of 

corporately owned salt production ponds from the Cargill Salt Company. The majority of these ponds 

(15,000 acres) are located in South SFB, with the balance (1,400 acres) located along the Napa River in 

the North SFB (Life_Science!, 2003). With a primary goal being wetlands restoration, this represents 

the largest single land purchase of its kind in U.S. history. More information on the South Bay Salt 

Pond Restoration Project can be found at URL: http://www.southbayrestoration.org. 

Avian research throughout SFB indicates that elevated mercury levels are found in fish and 

invertebrate eating bird populations in South SFB region in general, and in populations associated with 

the South Bay salt ponds (Ackerman and others, 2007; Ackerman and others, (in press)). 

Methylmercury (MeHg) is the organic form of mercury that is largely produced in anoxic sediments 

from inorganic divalent mercury (Hg(II)) by bacteria (Compeau and Bartha, 1985). It is a known 

neurotoxin and is of environmental concern due to its propensity to bioaccumulate in aquatic food webs 

(Wiener and others, 2003). Previous research has indicated that wetland environments appear to be 

particularly efficient areas for the microbial MeHg production (Lacerda and Fitzgerald, 2001; Zillioux 

and others, 1993). A recent national study of 20 U.S. watersheds concluded that wetland spatial density 

was the leading determinant of MeHg productions within a study basin (Krabbenhoft and others, 1999), 

and that MeHg concentration in water was correlated with mercury levels in fish (Brumbaugh and 

others, 2001). These findings, coupled with the potential for substantial wetland restoration throughout 

SFB, has raised concerns that increased wetland density may lead to an increase in local MeHg 

production and bioaccumulation (Davis and others, 2003), although direct mechanistic evidence of this 

linkage is lacking. 

As part of the salt production process, and apart from specific bay water intake points, salt ponds 

are effectively isolated hydrologically from the adjacent estuary and from tidal influence. A number of 

management strategies are currently being considered with respect to the existing salt ponds, including 

1) maintaining them as managed high salinity ponds for birds, 2) converting them to fully tidal wetlands 

by removing existing levees or breaching levees, or 3) converting them to partially muted tidal wetlands 

by installing tide control structures through existing levees (i.e. a levee notch) (PWA and others, 2006). 

The long-term plan for Pond A8 is conversion to fully tidal wetlands by levee breaching or removal. 

However, the pond’s location in the heart of the Guadalupe River discharge to the Bay makes mercury 

contamination a particular concern. Therefore, controlling the degree of tidal exchange and observing 

2
Introduction 

3

the effects of the pond/slough interaction is the currently preferred course of action. Therefore, the third 

strategy is currently being considered for Pond A8, which is adjacent to Alviso Slough and part of the 

Alviso salt pond complex in South SFB. Recent hydrodynamic modeling and geomorphic analysis 

conducted by Philip Williams and Associates, Ltd. (PWA), indicates that some deepening and widening 

of the current Alviso Sough channel will occur due to the increased tidal energy associated with an 

engineered levee notch (EDAW and others, 2007). The extent of sediment scouring will increase as a 

function of the size of the levee notch. Two notch scenarios were considered, which consist of either a 

20-foot (6.1 meter) or 40-foot (12.2 meter) wide armored notch in the current levee wall separating 

Pond A8 from Alviso Slough. These modeling results, coupled with known mercury contamination in 

Alviso Slough, and concerns regarding wetland habitats being effective zones of MeHg production, 

raise a number of questions regarding the Pond A8 levee notch scenario. These questions include: How 

much mercury is in Alviso Slough and what are its dominant chemical forms? How much mercury will 

be mobilized as a function of sediment scour? Will the chemical form of mercury currently buried 

change if remobilized? Where will the remobilized sediment and mercury ultimately end up? Will 

remobilized mercury have any net effect on local or regional MeHg production and bioaccumulation? 

To begin to answer some of these questions, a multi-year investigation of mercury-cycling and 

bioaccumulation in Alviso Slough and Pond A8 was undertaken by researchers from the San Francisco 

Estuary Institute (SFEI), U.S. Geological Survey (USGS), the Santa Clara Valley Water District 

(SCVWD) and the University of California, Berkeley (UC Berkeley). The current report focuses on 

Phase I objectives of this project, which include: 

1. Determining the quantity and speciation of mercury in Alviso Slough; 

2. Quantifying mercury species mobilization based upon the 20-foot and 40-foot levee notch scenario 

proposed for Pond A8; and 

3. Conducting a sediment scour simulation experiment aimed at determining if the chemical speciation 

of currently buried mercury is affected by remobilization. 

Purpose and Scope 

This non-interpretive report provides complete tabular and graphical data associated with 15 

two-meter deep sediment core profiles collected from the Alviso Slough main channel and the adjacent 

fringing marsh plain during September 2006. Field sampling methods and laboratory analytical methods 

are described for the following sediment constituents: total mercury (THg), methylmercury (MeHg), 

reactive mercury (Hg(II)R), magnetic susceptibility, gamma and bulk sediment density, organic content, 

grain size, pH, and oxidation-reduction potential. Mercury species mobilization estimates are made 

based on the 20-foot and 40-foot levee notch scenario proposed for Pond A8. Results are given from a 

series of sediment scour simulation experiments aimed at determining if the Hg(II)R pool associated 

with currently buried sediment layers is affected by remobilization and resuspension under oxic, anoxic, 

high salinity and low salinity overlying water conditions. Photography and lithographic descriptions are 

provided for each core segment collected. 
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Methods 

Study Area and Sample Collection 

Sediment cores were collected between September 21 and 26, 2006 from 15 stations along 

Alviso Slough in South SFB (Figure 2). Five sampling transects were established (T1 to T5), along the 

slough salinity gradient, from the least saline upstream transect cluster (T1) near the town of Alviso, to 

the most saline transect cluster (T5) near the slough mouth. Three sites were sampled along each 

transect, which included one site each from the right and the left vegetated marsh plain that fringes 

either side of the slough (A and C series cores, respectively), as well as one site in the main slough 

channel (B series cores). Series B cores were collected from a portable floating work platform anchored 

in the slough channel. Sediment collection was conducted using a hand-operated 5.1 cm diameter piston 

coring device (Livingstone, 1955). Each core deployment recovered up to 100 cm of sediment. Three to 

four core segments (coded D1 to D4; total length ranging from 24 cm to 98 cm each) were required to 

reach the desired maximum depth of approximately 200 cm at a single site, with the individual segments 

slightly offset from each other to allow for overlapping depths (Figure 3). Specific sampling locations 

and core segment sampling depths are given in Table 1 and Table 2, respectively. 

Initial Post-Collection Sediment Core Processing 

Within 3 – 7 days of field collection, sediment cores were characterized and sub-sampled. Each 

core section (50 in all) went through a five-step process which included a) initial non-destructive 

imaging of whole core sediment density and magnetic susceptibility, b) core splitting, c) physical 

description of the ‘working’ half split-core lithography and entering that information into a database, d) 

sub-sampling parameters of interest, and e) photographing the ‘archive’ half split-core. 

Multi-Sensor Core Logger 

Sediment wet bulk density (via the gamma irradiation method) and magnetic susceptibility (a 

measure of magnetic mineral content) were first made using the Multi-Sensor Core Logger (MSCL) 

(Model MSCL-75), which is owned and operated by the Coastal Marine Geology unit of the USGS 

(Menlo Park, CA). By measuring and studying the variation of these two state properties, an ‘inside 

look’ of each core was obtained prior to actually splitting the core tubes. Since down-core variation in 

these parameters is often not readily apparent to the naked eye, even once the cores are split and 

inspected, the MSCL data were critical in helping to decide exactly how to space the specific sediment 

intervals to be sub-sampled. 

The MSCL-system is described in detail elsewhere (Gardner and others, 1995; Kayen and 

others, 1999). The MSCL consists of a four meter long tracking system that holds three sequential 

measurement devices: 1) a gamma ray wet bulk density sensor, 2) a primary compression-wave (Pwave) velocity and core-diameter sensor, and 3) a magnetic susceptibility sensor. A Macintosh 

computer driven by data acquisition software controls the system. Whole core sections up to 1.5 m in 

length can be logged. Core movement along the tracking system is run by a computer-controlled stepper 

motor that advances the core section at 1-cm intervals during logging. Each core section was run 

consecutively through the sensors, starting with the top of the section and progressing through to the 

bottom of the core. Core caps at each end (approximately 3 cm at the top and bottom of each core 

section) generate spurious data, which was subsequently excluded in the sediment profiles depicted in 

this report. 

4
Methods 

The sediment density sensor functions by sending a beam of gamma radiation (emitted from a 

137CsCl solid source) through the diameter (width) of the whole core. A scintillation detector coupled to 

a photomultiplier measures the attenuated radiation that passes through the core diameter. This 

attenuated gamma radiation signal is converted to sediment density (g/cm3

) by applying a two-point 

calibration curve based on the attenuated gamma radiation signal produced by a similar core tube filled 

with either pure water or a solid cylinder of aluminum (both of accurately known densities: 1.0 g/cm3

and 2.7 g/cm3

, respectively). Calibration cores containing water and aluminum were run daily to verify 

the accuracy and consistency of the instrument. 

The magnetic susceptibility sensor is set electronically by the manufacturer, based on a single 

standard of stable iron oxide. Thus, this sensor is calibrated absolutely and requires no additional 

calibration during daily operation. 

The quality of the P-Wave velocity data was inconsistent due to a combination of factors 

including: the lack of water-saturated sediment in some core sections, incomplete coupling of the 

sediment with the interior core liner wall in some core sections, and the comparatively high degree of 

flexibility of the thin-walled core liner that was used for sediment collection. Thus, P-wave velocity data 

generated by the MSCL were not used in the determination of sediment intervals to sub-sample, and are 

not presented in this report. 

Core Splitting 

After the data from the MSCL were obtained and assessed, each core section was split vertically 

into two equal halves, representing the ‘working’ and ‘archive’ split core halves. The core end-caps 

were first removed. The whole core section was then placed into an aluminum core cradle with an inner 

diameter that exactly matches the outer diameter of the core tube, and which includes a top and bottom 

half, and thus totally encases the core liner. The core cradle also has two slits running along the length 

of each half, which act as a straight-line guide for the cutting tool. A utility knife blade was inserted at 

one end of the guide-slit, cutting into the core liner. The blade was run along the guide-slit until the core 

liner was cut from the top to the bottom ends on one side. The whole cradle was rotated 180o, and the 

core liner was again cut along a line that is parallel and exactly opposite (180 o) the first. The core was 

then removed from the cradle and a very thin stainless steel wire was run longitudinally through the 

center of the core, along its full length. The two halves were then carefully pried apart and laid openfaced on the work bench. A film of plastic-wrap was gently placed over the exposed sediment of the 

‘archive’ split core to minimize drying and chemical oxidation. The archive split-core half was then 

stored in a walk-in cooler at 3o

C until it can be photographed. 

Core Descriptions & Database 

The ‘working’ half split-core was moved to the work table outfitted with bright ‘full spectrum’ 

lights. The surface of the sediment was gently smoothed with an acid-clean stainless steel spatula 

(motion perpendicular to the length of the core), removing the surface 1-2 mm of material to expose 

fresh sediment. Always measuring from the top of the core down, the following lithologic parameters 

were noted for the complete core section: sediment color (hue/chroma) using the standard Munsell® soil 

color chart , grain-size via texture to touch (e.g. sand, silt, clay), the position and nature of stratigraphic 

contacts, and sedimentary structures (e.g. plant roots, shell fragments, etc.). All of this information was 

input into a sediment profile description database created in FileMaker Pro 6.0 (FileMaker, Inc. Santa 

Clara, CA) by the Coastal Marine Geology group at USGS (Menlo Park, CA). 

5
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Core Sub-Sampling 

After fully describing an individual core section and assessing the associated MSCL density and 

magnetic susceptibility data, a decision was made as to the specific intervals to be sampled. Depth 

intervals typically ranged 10 – 30 cm in length. Priority of interval placement was given to obvious 

peaks in density and/or magnetic susceptibility, and to visible changes in sediment color and/or texture. 

Such discrete features were bracketed and typically sampled in one interval. When no such obvious 

features were noted, specific intervals were typically set to 20 or 30 cm, depending on the total number 

of intervals already identified for that whole 2 m core profile. When core sections from the same site 

overlapped (which was typically the case), sub-sampling in the next lower core section would begin at 

the sediment depth associated with the bottom of the last interval from the core section just above it. 

This allowed for collection of sub-samples representing the complete 2 meter length of the core site, 

without overlapping data. The only exception to this was profile T5A, which was the first sampled, and 

where there was some depth overlap during the sub-sampling between core sections D1, D2 and D3. 

Once all depth intervals had been determined for the whole core section, tape was placed on a 

ruler that ran along side the core to mark-off each interval. Beginning with the top interval, an acid 

cleaned 1x1x1 cm plastic U-shaped sampling channel was placed open-face down along the length of 

the desired interval (just left of center) and then pushed evenly into the sediment until the top edge was 

flush with the sediment surface. A thin acid-cleaned stainless steel wire was then run along the bottom 

edge of the sampling channel to make a clean cut between the sediment inside and outside of the 

sampling channel, which was then gently extracted from the core section. This approach ensured that no 

sediment was sub-sampled that had been in contact with the interior surface of the core liner. The 

sediment filling the channel was immediately scraped from the interior into a 4 ounce (114 cm3

) plastic 

Whirl-PakTM bag. A second channel was similarly sub-sampled (just right of center), and the extracted 

sediment was added to the same plastic bag. This resulted in 20 cm3 (for a 10 cm interval) to 60 cm3 (for 

a 30 cm interval) of sediment for each sub-sample. All sediment was squeezed to the bottom of the bag 

and all air squeezed out of the bag, which was then sealed at the top. The sediment in the bag was then 

well homogenized by hand manipulation of the bag for approximately 1 minute. 

The bag was reopened and sub-samples were taken with an acid-cleaned 3 cm3

 plastic syringe 

(with the needle-end cut off) for the following parameters: a) total mercury (THg) [3-6 cm3

, frozen 

immediately on dry ice, all intervals and sites], b) reactive mercury (Hg(II)R) [3-6 cm3, flushed with 

nitrogen gas then frozen immediately on dry ice, all intervals and sites associated with Transects 1, 3 

and 5 only], c) MeHg (MeHg) [3-6 cm3

, flushed with nitrogen gas then frozen immediately on dry ice, 

all intervals and sites associated with Transects 1, 3 and 5 only], d) combined organic content and % dry 

weight [6 cm3

, refrigerated, all intervals and sites], and e) grain size [6 cm3, refrigerated, all intervals 

and sites]. Collection vials for all THg, organic content and grain size were 10 ml glass serum bottles. 

Collection bottles for Hg(II)R and MeHg were acid cleaned pre-combusted 20 ml screw-top glass vials. 

Sub-sample duplicates were taken for all of the above constituents at a frequency of approximately 10% 

of all samples collected. 

After sub-sampling for the above parameters, the sediment remaining in the Whirl-PakTM bag 

was again squeezed back to the bottom, and sediment pH and oxidation-reduction potential 

measurements are immediately taken on this material (see procedure below). The excess sediment that 

remained in the core liner was used to fill a new Whirl-PakTM bag that was saved as an archive sample 

for that particular core section / depth interval. Sediment was squeezed to the bottom of the bag, and air 

was squeezed out, prior to sealing (as above). These archived sub-samples are stored refrigerated. The 

above sub-sampling procedure was repeated for all core sections and depth intervals. 

6
Methods 

Core Photography and Archiving 

The sediment surface of the archive half split-core was gently smoothed (perpendicular to core 

length) with an acid-clean stainless steel spatula, removing the surface 1-2 mm of material to expose 

fresh sediment. The core was returned to the MSCL-system (described above) which is equipped with 

an overhead mounted Geoscan-colorline scan digital camera (using 3x1024 pixel charge-couple device 

arrays, PentexTM k mounting lens). The system takes a digital photograph of the whole core in one 

image, while the core is mechanically moved down the MSCL track by the computer-controlled stepper 

motor. The image processing software (GeoscanTM Digital Imaging, version 5.2) creates a high 

resolution (approximately 25 Mb) JPEG file. After photographing, the exposed sediment surface of the 

archive half split-core was again covered with plastic wrap, and the core was placed into a D-tube for 

long-term storage in the USGS (Menlo Park) core refrigerator (at 3oC). A piece of wet sponge was 

added to the D-tube to maintain a high moisture atmosphere, and the end of the D-tube was sealed with 

duct-tape and appropriately labeled. 

Laboratory Analysis 

Mercury Speciation 

Total Mercury 

Sub-samples for THg were taken at every depth interval for all sites, and were frozen at the time 

of sampling and maintained frozen until analysis. The procedure used for THg analysis generally 

follows that of an approved USGS method (Olund and others, 2004). Once thawed, sediment samples 

(approximately 0.25 g wet weight) are initially digested in an aqua regia mixture (2 mL concentrated 

hydrochloric acid and 6 mL of concentrated nitric acid) for 24 hours then a 5 % bromide monochloride 

solution is added to the sediment slurry which is then heated to 50 oC in an oven overnight. After 

samples are cooled, a sub-sample is transferred into a pre-combusted glass container and held until 

further analysis. Each batch of 10 environmental samples is accompanied with analysis of the following 

Quality Assurance (QA) samples: a) 1 certified reference material, b) 1 matrix spike sample, c) 1 

analytical duplicate, and d) 1 method blank. The digestate is then analyzed on an Automated Mercury 

Analyzer (Tekran Model 2600), according to EPA Method 1631, Revision E (USEPA, 2002). This 

method is based on the reduction of Hg(II) to gaseous Hg0

 with tin chloride, trapping Hg0 on gold sand, 

thermal desorption and quantification of Hg0

 via cold vapor atomic fluorescence spectrometry. 

Calibration standards are prepared from a NIST-certified commercially obtained HgCl2 standard. The 

USGS Mercury laboratory in Menlo Park has been taking part in the QA/QC program overseen by Van 

Buuren Consulting LLC, for the CALFED/CBDA Ecosystem Restoration Program funded Mercury 

studies throughout the San Francisco Bay region. Participation in this program includes: a) standard 

operating procedure documentation review, b) conducting a mean detection limit prove-out exercise, 

and c) inter-laboratory comparison analysis of THg in sediment and water matrices (VBC, 2005; VBC 

and CDFG, 2005). 

Reactive Mercury 

Sediment “reactive” mercury (Hg(II)R) is methodologically defined as the fraction of THg in a 

sediment sample that has not been chemically altered (e.g. digested, oxidized or chemically preserved) 

and that is readily reduced to elemental Hg0

 by an excess of tin chloride (SnCl2) over a defined (short) 

exposure time. This operationally defined parameter was developed as a surrogate measure of the 

fraction of inorganic Hg(II) that is most likely available to Hg(II)-methylating bacteria responsible for 

7
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

MeHg production. While there is no standard method for this parameter, the procedure described below 

is modified from that described elsewhere (Kieu, 2004), and has been used extensively in a number of 

research studies led by USGS researchers (Marvin-DiPasquale and others, 2006). 

Recent experimental evidence suggests that the Hg(II)R assay effectively measures the fraction 

of Hg(II) that is associated with simple anions (e.g. HgSO4, HgCl2) in sediment pore water and/or 

Hg(II) that is weakly adsorbed to particle surfaces (Marvin-DiPasquale and others, 2006). Both of these 

fractions are indeed likely available to sediment microbes for Hg(II)-methylation. In a related set of 

experiments, the concentration of Hg(II)R measured in a suite of freeze-dried and homogenized 

environmental samples ranging over four-orders of magnitude in THg (1-24,000 ppm), was strongly 

correlated (r2 = 0.97) with the amount of MeHg produced when these freeze-dried samples were mixed 

(at a constant THg amendment level) with fresh sediment containing active populations of Hg(II)-

methylating bacteria (Bloom and others, 2006). These results suggest that the Hg(II)R fraction, as 

measured below, does provide a reasonable surrogate measure of the fraction of THg that is potentially 

available for Hg(II)-methylation. 

Upon thawing in an anaerobic chamber (N2 flushed), sediment sub-samples were initially 

homogenized in the original collection vial using an acid cleaned stainless steel spatula. A small amount 

of sediment (0.1-1.0 g) was then accurately weighed into 15 ml plastic centrifuge tubes, to which 10 ml 

of anoxic 0.5 % HCl solution was added. The tubes were capped and the resulting sediment slurry was 

homogenized using a vortex shaker. Samples were then removed from the anaerobic chamber and 

immediately refrozen on dry ice to minimize any oxidation reactions prior to transfer into the reaction 

bubblers. The reaction bubbler rig, the dual gold trap analytical set-up, and the cold vapor atomic 

fluorescence spectrophotometer (CVAFS) detection system employed for the remainder of the assay is 

the same as is described in EPA Method 1631 (USEPA, 2002) for the analysis of THg in an aqueous 

samples. 

A set of four environmental samples were allowed to thaw for approximately 15 minutes prior to 

the actual analysis. The 200 ml glass gas-flushing bottles (bubbler flasks) are filled with 40 ml of anoxic 

0.5 % HCl. The sample slurry was briefly remixed and the entire contents of a single centrifuge tube 

were quickly and completely transferred to a single bubbler. A 0.5 ml aliquot of 20 % (w/v) SnCl2 was 

added to each and the system was sealed and purged with nitrogen gas for exactly 15 minutes while 

gently shaking. The evolved gaseous Hg0 is subsequently trapped on a gold-sand trap. A soda-lime trap 

is located between the bubbler and the gold trap to protect the latter from acid fumes, as detailed in EPA 

Method 1631. The Hg0

 is then thermally desorbed from the gold trap to the analytical system and 

detected using CVAFS detector (Brooks Rand Model III Mercury Analyzer). Peak integration software 

(Peak Simple, Chrom Tech, Inc. Apple Valley, MN) is used to convert the analog signal output from the 

CVAFS to an integrated peak area value. Standard curves generated from aqueous HgCl2 calibration 

standards, assayed as above, were used to calculate Hg(II)R concentrations. 

Daily analytical batches consisted of a set of 4 (minimum) calibration standards, 8-16 Hg(II)R

samples, 1-2 additional replicates of a single randomly picked Hg(II)R sample, and 4 bubbler blanks. 

Bubbler blanks consisted of 50 ml of 0.5% HCl and the SnCl2 amendment only (no sediment). 

Calibration standards are prepared by dilution of a NIST-certified commercially obtained HgCl2

standard. In addition, a precisely calculated amount of gaseous elemental Hg0 is injected into the 

analytical rig to verify the results (peak area vs. total mercury added) of the aqueous standards. 

Methylmercury 

A standard USGS approved method was used for the sediment MeHg extraction and 

quantification (DeWild and others, 2004). In summary, MeHg is first extracted from sediment (0.5 to 

8
Methods 

1.0 g) with a mixture of potassium bromide, copper sulfate, and methylene chloride. A sub-sample of 

the organic phase (methylene chloride) is added to a container of water, which is then slowly heated. 

This results in the evaporation of the organic phase and the back-extraction of the MeHg into the 

aqueous phase. The pH is adjusted to 4.9 using acetate buffer. The extractant is then ethylated using 

sodium tetraethyl borate. The volatile ethylated mercury species are purged from solution with N2 gas, 

collected on a carbon-trap, thermally desorbed, separated using a gas chromatographic (GC) column, 

reduced using a pyrolytic column, and detected using CVAFS. 

Additional Sediment Characterization 

Sediment pH 

Measurements were made with a pH electrode used in conjunction with a hand held pH/mV 

multi-meter (Model 59002-00, Cole Parmer®). The electrode was calibrated daily with fresh commercial 

pH = 7 phosphate buffer and then rinsed clean with reagent water. The probe was then fully inserted 

into the homogenized sediment, which was squeezed into a ball around the probe tip (to exclude any air 

bubbles) in the bottom of the plastic Whirl-PakTM bag. 

Oxidation-Reduction Potential (ORP) 

Measurements of sediment ORP were made with a platinum band ORP electrode (Model 

EW05990-55, Cole Parmer®) used in conjunction with a hand held pH/mV multi-meter (as above). The 

electrode’s accuracy was tested daily with freshly made buffer solutions (pH = 7 and pH = 4) saturated 

with quinhydrone, as per the manufacturer’s instructions (Cole-Parmer document #P1937). The ORP 

potential for each solution is measured and the difference between them calculated. If this value fell 

within the range of 173 ± 4 mV, the probe was determined to be functioning properly. After cleaning 

thoroughly with reagent water and drying, the probe was then fully inserted into the homogenized 

sediment, which was squeezed into a ball around the probe tip (to exclude any air bubbles) in the bottom 

of the plastic Whirl-PakTM bag. The ORP meter was allowed to equilibrate for a minimum of 10 

minutes, until a stable reading is achieved, prior to recording the milli-volt (mV) value. All 

measurements were taken while sediment was at room temperature (19-22 oC). The ORP meter values 

were converted to Eh values (a standard convention that adjusts the value assuming a normal hydrogen 

reference electrode), using the following conversion provided by the electrode manufacturer: 

Eh = ORP + ER 

ER = (-0.718 x T) + 220 

Where: ORP = the oxidation-reduction potential value directly from the meter (millivolts); ER = is the 

standard potential for a normal hydrogen reference electrode (millivolts); T = temperature (oC) 

Bulk Density, Percent Dry Weight, Porosity and Organic Content 

Sediment bulk density, dry weight, porosity and organic content were all assayed in order from a 

single sediment sample. An exact 3.0 cm3 of wet sediment was removed from the sample vial using a 

3.0 cm3 plastic syringe that has the needle end cut off of the syringe barrel. This sub-sample was 

transferred into a small crucible and weighed. Sediment bulk density (g/cm3) was then calculated as the 

weight-to-volume ratio. 

Sediment dry weight and porosity were measured using standard drying techniques (APHA, 

1981a).The crucible was then placed in an oven over-night at 105 o

C. The next day, the sample was 

placed in a dedicator to cool, and was then reweighed. The sediment percent dry weight was then 

9
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

calculated as [dry sed wt./wet sed wt. x 100]. Sediment porosity (ml porewater per cm3 of wet sediment) 

was calculated as the volume of water lost upon drying divided by the original sediment wet volume. 

Organic content was calculated via the weight Loss on Ignition (LOI) standard assay (APHA, 

1981b). The crucible was then placed in a combustion oven at 500 o

C for four hours. This completely 

burns off any organic constituents, leaving only mineral material. After recooling and reweighing, the 

weight loss was calculated, which is a measure of total organic content. 

Grain Size 

Grain size, greater or less than 63 microns (the sand/silt split), was assayed using a standard wet 

sieve method (Matthes and others, 1992). 

Sediment and Mercury Inventory and Mobilization Calculations 

A model analysis of predicted changes in Alviso Slough geometry, based upon the 20-foot and 

40-foot notch scenarios for Pond A8, was previously conducted by PWA and presented in Appendix G 

of the draft Environmental Impact Study / Report for the South Bay Salt Ponds Restoration Project 

(EDAW and others, 2007). This report includes information regarding existing channel depth, width 

and cross sectional area, as well as predicted changes in these parameters associated with the two 

different notch scenarios, at five cross channel transects along the slough length (Figure 2). Based upon 

the location of these five transect lines, four sections of Alviso Slough were defined (Sections A through 

D; including slough channel plus fringing marsh), which were bounded by the transect lines on either 

end and the existing levee walls (Figure 2). The area of each section was determined from aerial 

photographic images of the study area, using two independent approaches. The first involved map 

digitization and subsequent area calculation using ArcMap software (Environmental System Research 

Institute, Redlands, CA). The second approach involved carefully cutting out (in triplicate) the defined 

sections from printed map images, weighing them to an accuracy of ± 0.0001 g, and calibrating these to 

similarly cut and weighed squares representing an area of 1 km2

 that was derived from the map distance 

scale. The two approaches to calculating the area of each section agreed to within 2.7 ± 1.4 % The 

length of the slough channel for each section was measured from aerial photographic images using the 

perimeter tool in Adobe Acrobat® (version 7.0 Professional). 

The current inventory of each mercury species in each segment of Alviso Slough (A through D) 

was calculated as follows: (a) The concentration of each species was calculated on an aerial basis (e.g. 

mg/m2

) for each depth profile by integrating the cumulative volumetric concentrations to a common 

depth of exactly 0-200 cm. (b) Depth integrated concentrations from all sediment sampling sites that fell 

within a defined slough section were averaged to calculate a single 0-200 cm depth integrated value for 

that segment (e.g. all six sediment sampling sites associated with T2 and T3 were used to calculate a 

single 0-200 cm depth integrated THg value for slough segment C, see Figure 2). The exception to this 

grouping approach was for slough segment A, in which no sediment was sampled within its defined 

boundaries. In this case the three profiles associated with the T1 sediment sampling were used. (c) The 

average 0-200 cm depth integrated mercury species concentration (calculated in (b)) for a given slough 

section was then multiplied by the area of that section to calculate the total current inventory for that 

species in that slough segment. The resulting mercury inventory of all slough sections were added to 

calculate the complete mercury species inventory for Alviso Slough, between the uppermost PWA 

transect line (A8 Notch) and the lowermost one (Mouth). 

To calculate the volume of sediment mobilized for each slough section and for each notch 

scenario the following approach was taken: (d) the change in slough cross sectional area (m2

) of each 

was first calculated for each transect from the data provided in the PWA report, (e) the average change 

10
Methods 

in cross sectional area (m2) for each slough segment (A through D) was than calculated as the average 

(± deviation; n =2) of the upper and lower bounding transect lines for that slough segment, (f) the value 

from (e) was multiplied by the measured slough length for that segment to calculate total cubic meters 

(m3

) of sediment mobilized under each scenario. The error associated with calculation (e) was carried 

through the rest of the calculation for sediment and mercury mobilization. Based on modeling results 

and for the purposes of these calculations, the assumption is made that the predicted change in the 

slough cross sectional area for the downstream most transect line (Mouth) is zero for both notch 

scenarios (i.e. no change) (Don Danmeier, PWA, personal communication). 

To calculate the amount of each mercury species mobilized for each section and notch scenario, 

the following approach was taken: (g) the sediment volumetric mercury species concentration (e.g. 

mg/m3

) was first calculated for each discrete sample, based on the weight-based concentration (e.g. ng/g 

wet sediment) and the sediment bulk density (g/cm3

). (h) A single average (± standard error) value of 

volumetric mercury species concentration was then calculated as the average of all of the discrete 

samples that comprised the sediment profiles associated with that particular slough section (grouped as 

described in (b)). (i) To calculate the absolute mass of each mercury species mobilized for each slough 

segment (A through D), the specific volumetric mercury species concentration (calculated in (h)) was 

multiplied by the volume of sediment mobilized (calculated in (f)) for that section and notch scenario. 

The error associated with both (f) and (h) were propagated through these calculations. The mercury 

species mass mobilized in each slough segment was added to calculate the total mercury species mass 

mobilized between the uppermost PWA transect line (A8 Notch) and the lowermost one (Mouth). 

Sediment Scour Simulation Experiment 

Excess sediment from the 150-175 cm depth horizon of core AS-T2B-D3 was transferred into an 

acid cleaned glass mason jar at the time of initial sub-sampling and was stored refrigerated at 5 oC for 

109 days prior to the initiation of the scour simulation experiment.. Surface water from Alviso Slough 

was collected as part of routine sampling by the SCVWD in late January 2007. The water from two sites 

(ASW1 and ASW3) was filtered (0.45 μm) and stored refrigerated at 5 o

C for 7 days prior to the 

initiation of the scour simulation experiment. The salinity between these two sites varied more than twofold, with the upstream ASW1 site being less saline (11 ppt) than ASW3 (26.5 ppt), the latter being 

located closer to the slough mouth. These two source waters were subsequently sub-sampled such that 

1.0 liter of each was transferred into two large glass flasks equipped with a rubber stopper that had a) a 

port for a fritted glass gas purging rod that extended to the bottom of the flask, b) a gas venting tube, 

and c) a liquid sampling FEP tube that extended to the bottom of the flask and that had a stopcock above 

the stopper to close it off when not in use. The filtered slough water from both sites was purged for 24 

hours with either compressed air or inert nitrogen (N2) gas, while stirring with a magnetic stir bar. Thus, 

four treatment conditions were established with Alviso Slough water: a) low salinity / oxic, b) low 

salinity / anoxic, c) high salinity / oxic, and d) high salinity / anoxic. After establishing these initial 

conditions, two 50 ml samples of water were removed from each flask for initial aqueous Hg(II)R

concentration analysis. The AS-T2B-D3 sediment was then sub-sampled and accurately weighed in an 

anaerobic chamber, and 27 g was added to each of the four flasks, resulting in final total suspended 

sediment concentration of 14.3 g dry sediment per liter (based upon 48.0 % sediment dry weight 

initially measured). Duplicate sub-samples of sediment (approximately 2 g each) were also taken and 

frozen for subsequent whole sediment Hg(II)R concentration analysis, and triplicate sub-samples were 

take for sediment dry weight analysis. Immediately after adding sediment to all four flasks, gas purging 

and aqueous phase stirring was resumed and continued thus throughout the remainder of the experiment. 

After approximately 1 hour, an initial (Day 0) sample was taken from each flask. Sub-sampling 

11
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

12

consisted of attaching a 60 ml syringe to the liquid sampling tube, opening the stopcock and pulling 

approximately 50 ml of the suspended sediment slurry into the syringe, which was subsequently 

weighed so that the exact sediment mass sampled could be calculated. The slurry in the syringe was 

immediately assayed for Hg(II)R, as described above. Duplicate 50 ml sub-samples were taken from 

each flask during each sampling event, which was similarly repeated on days 1, 3, 5, and 7. 
References 

Results 

Sediment Core Descriptions 

Photographs, lithographic and accessory descriptions, and MSCL scans of sediment gamma 

density and magnetic susceptibility profiles are provided in Appendix A for of all 50 core segments 

collected. 

Mercury Speciation and Quantification 

Site and depth specific concentration data (dry weight) for THg, Hg(II)R and MeHg are 

summarized in Table 2, along with the quantity of Hg(II)R and MeHg expressed as a percentage of 

THg and summary statistics for the complete dataset. Concentration profiles for THg are graphically 

illustrated in Figure 4 on a whole sediment basis (μg/cm3

), with the 0-200 cm depth integrated value 

(g/m2) provided for each profile. Similarly, the whole sediment concentration profile for MeHg (ng/cm3) 

is graphically illustrated in Figure 5, with the 0-200 cm depth integrated (mg/m2

) value provided for 

each site. Site specific profiles of % Hg(II)R are presented (log10 scale) in Figure 6, along with the 0-

200 cm depth integrated Hg(II)R concentration (mg/m2

) at each site. 

Quality assurance metrics for mercury species concentrations were as follows: The average 

percentage difference for THg samples run in duplicate was (mean ± std. dev.) 6.1 ± 5.1 % (N = 23). A 

5 ng/L daily quality check standard (QCS), prepared from a different stock HgCl2 solution than for the 

normal daily standard curve, was 97.4 ± 5.7 % of the theoretical value (N = 11). Recoveries of certified 

reference material (IAEA-405, estuarine sediment, THg certified value = 0.81 μg/g dry weight) were 

103 ± 6 % (N =7) of the certified value. Matrix spike recoveries for THg were 103 ± 29 % (N = 6) of 

the calculated amount of Hg(II) added. The average percentage difference for Hg(II)R samples run in 

duplicate was 12.9 ± 9.5 % (N = 6). There is no certified reference material for Hg(II)R and matrix 

spikes do not provide reliable results due to the rapid binding of some fraction of the added Hg(II) spike 

to dissolved and solid organic phases. The average percentage difference for MeHg samples run in 

duplicate was 11.6 ± 9.1 % (N = 13). Recoveries of certified reference material (IAEA-405, estuarine 

sediment, MeHg certified value = 5.49 ng/g dry weight) were 83 ± 24 % (N = 16) of the certified value. 

Matrix spike recoveries for MeHg were 66 ± 45 % (N = 20) of the calculated amount of MeHg added. 

Ancillary Sediment Parameters 

Site and depth specific data for sediment pH, oxidation-reduction potential (Eh), dry weight, 

organic content (as % LOI), bulk density, porosity and grain size are summarized in Table 3, along with 

summary statistics for the individual profiles and the complete dataset. The following ancillary sediment 

parameter data are also given graphically: pH (Figure 7), Eh (Figure 8), LOI (Figure 9), and grain size 

(Figure 10). MSCL scan data are graphically depicted for sediment density via gamma irradiation 

(Figure 11) and magnetic susceptibility (Figure 12). In addition, discrete interval measurements of 

sediment bulk density, as directly measured via sub-sample weights and volumes, are superimposed on 

MSCL profiles of gamma density (Figure 11). The average percentage difference for samples run in 

duplicate was as follows (mean ± std. dev.): dry weight, 0.5 ± 0.7 % (N = 26); LOI, 2.6 ± 3.1 % (N = 

25); bulk density, 1.5 ± 1.5 % (N = 26); porosity, 1.5 ± 1.6 % (N = 26); and grain size 1.4 ± 1.0 % (N = 

8). Due to time constraints and equipment limitations during initial sample processing only one 

measurement was made for pH and Eh for each individual sample. 

13
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

14

Sediment and Mercury Mobilization Estimates 

Previously reported (EDAW and others, 2007) Alviso Slough current cross sectional areas, and 

those predicted for the 20-foot and 40-foot Pond A8 notch scenarios, are given in Table 4 along with 

the calculated change in cross sectional area associated with both notch scenarios. The area and channel 

length measurements for the defined slough sections A-D (Figure 2) are given in Table 5, along with 

the volume of sediment mobilized as calculated for both notch scenarios. 

Sediment Scour Simulation Experiment 

The experimental mixing of deeply buried (150-175 cm depth interval) Alviso Slough main 

channel sediment with overlying slough water was conducted to simulate the scenario under which 

increased tidal energy in Alviso slough leads to the deepening of the slough channel, thus mobilizing 

sediment and currently buried mercury. The specific question addressed by this experiment is whether 

or not the operationally defined Hg(II)R fraction in buried (and chemically reducing) sediment changes 

(increases or decreases) as a result of being exposed to oxygenated overlying water of either high or low 

salinity. The anoxic treatments serve as a type of control, as the oxic treatments are more reflective of 

typical field conditions since the overlying slough water is tidally mixed and anoxic water conditions 

have not been observed in any of the five sampling events that have been conducted as part of the larger 

study between November 2006 and July 2007 (dissolved oxygen = 5.3 ± 0.8; n = 30 [5 sampling events 

x 3 sites along the salinity gradient x 2 depth (surface and deep)]). 

The initial wet sediment Hg(II)R concentration was 0.14 ± 0.01 ng/g (0.30 ± 0.03 ng/g on a dry 

weight basis; n = 2). Initial aqueous Hg(II)R concentrations in the four treatment flasks, sampled 

immediately prior to the addition of sediment, ranged from 0.30 – 0.84 ng/L. Based on these 

measurements and the exact initial volumes used, the theoretical Hg(II)R concentration in the 

sediment/water slurry would be approximately 4.4 – 5.0 ng/L, assuming homogeneous mixing and no 

changes in the pool of Hg(II)R due to oxidation or reduction reactions. Within 1-2 hours of adding 

sediment to the flasks (Day 0), the actual Hg(II)R concentration measured for the individual slurry 

solutions ranged from 1.5 ng/L (high salinity / anoxic) to 4.0 ng/L (low salinity / anoxic). However, 

within 24 hours (Day 1) concentrations began to increase, and ranged from 25 ng/L (high salinity / 

anoxic) to 179 ng/L (high salinity / oxic). Over the next six days, the concentrations in both anoxic 

slurries remained in the comparatively narrow and low range of 17-29 ng/L, while the oxic treatments 

either remained elevated or continued to increase, ending at concentrations of 169 ng/L (high salinity / 

oxic) and 265 ng/L (low salinity / oxic) by Day 7 (Figure 13). Relative to the theoretical slurry Hg(II)R

concentrations of 4.4 – 5.0 ng/L, based solely on the mixing of Alviso Slough sediment and water at 

initial concentrations, the approximate factor increase by the end of the experiment for each of the four 

treatments was as follows: 4X (low salinity / anoxic), 6X (high salinity / anoxic), 53X (low salinity / 

oxic), 35X (high salinity / oxic) Thus, these results indicate that the mixing of chemically reducing 

buried sediment with oxygenated overlying slough water significantly increases the fraction of Hg(II)R. 

This experiment does not address how long these conditions are maintained beyond 7 days or the 

ultimate fate of this Hg(II)R pool. 
References 

Acknowledgments 

The authors gratefully acknowledge the following individuals and organizations: J.L. Agee, E. 

Kakouros, S.L. Wren, J. Kanerva, K. Akstin (USGS, Menlo Park, CA) and C.N. Alpers (USGS, 

Sacramento, CA) for laboratory analytical support; J. Collins, L. Grenier, J. Hunt, S. Bezalel (SFEI, 

Oakland, CA) for collaborative, field and logistical support; D. Drury and B. Calhoun (SCVWD, San 

Jose, CA) for field logistical support; B. Watson and L. Reidy (UC Berkeley, CA) for sediment core 

collection and laboratory assistance; B. Edwards and B. Carkin (USGS, Menlo Park, CA) for use of the 

Multi-sensor core logger; D. Danmeier (PWA, San Francisco, CA) for assistance with sediment scour 

estimates, and S. Ritchie (California Coastal Conservancy, Oakland, CA) and M. Singer (USGS, Menlo 

Park, CA) for providing constructive reviews of this report. The work described herein was funded by 

the California Coastal Conservancy under Interagency Agreement #06-004. 

References 

Ackerman, J., Eagles-Smith, C., Heinz, G., Wainwright-De La Cruz, S., Takekawa, J., Adelsbach, T., Miles, A., 

Hoffman, D.J., Schwarzbach, S.E., Suchanek, T.H., and Maurer, T.C., 2007, Mercury in birds of the San 

Francisco Bay-Delta: trophic pathways, bioaccumulation and ecotoxicological risk to avian reproduction. 2006 

Annual Administrative Report to CALFED: U.S. Geological Survey, Western Ecological Research Center, and 

U.S. Fish and Wildlife Service, Environmental Contaminants Division, 41 p. 

Ackerman, J.T., Eagles-Smith, C.A., Takekawa, J.Y., Demers, S.A., Adelsbach, T.L., Bluso, J.D., Miles, A.K., 

Warnock, N., Suchanek, T.H., and Schwarzbach, S.E., (in press), Mercury concentrations and space use of prebreeding American avocets and black-necked stilts in San Francisco Bay: Science of The Total Environment. 

Alpers, C.N., Hunerlach, M.P., May, J.T., and Hothem, R.L., 2005, Mercury contamination from historical gold 

mining in California: US Geological Survey, Fact Sheet 2005-3014, 6 p. On-line: 

http://pubs.usgs.gov/fs/2005/3014/

APHA, 1981a, Section 209 C: Total Nonfiltrable Residue Dried at 103-105 o

C, in Franson, M.A.H., ed., Standard 

Methods for the Examination of Water and Wastewater, 15th Edition: Washington, D.C., Amer. Public Health 

Association, Amer. Water Works Assoc., Water Pollut. Control Fed., p. 94-95. 

---, 1981b, Section 209 G: Volatile and Fixed Matter in Nonfilterable Residue and in Solid and Semisolid Samples, in

Franson, M.A.H., ed., Standard Methods for the Examination of Water and Wastewater, 15th Edition: 

Washington, D.C., Amer. Public Health Association, Amer. Water Works Assoc., Water Pollut. Control Fed., p. 

97-99. 

Bloom, N., Bollen, A., Briscoe, M., Hall, G., Horvat, M., Kim, C., Lasorsa, B., Marvin-Dipasquale, M., and Parker, J., 

2006, International Solid Phase Mercury Speciation Exercise (ISPMSE): Introduction and Preliminary Results, in

Mercury 2006 Abstracts Book: Eighth International Conference on Mercury as a Global Pollutant, Madison, 

Wisconsin August 6-11, 2006. 

Brumbaugh, W.G., Krabbenhoft, D.P., Helsel, D.R., Wiener, J.G., and Echols, K.R., 2001, A national pilot study of 

mercury contamination of aquatic ecosystems along multiple gradients: Bioaccumulation in fish: U.S. 

Geological Survey, USGS/BRD/BSR-2001-0009, 26 p. 

15
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Cargill, S.M., Root, D.H., and Bailey, E.H., 1980, Resource estimation from historical data: mercury, a test case: 

Statistics and Earth Sciences, no. 12, p. 489–522. 

Compeau, G.C., and Bartha, R., 1985, Sulfate-reducing bacteria: Principal methylators of mercury in anoxic estuarine 

sediment: Applied and Environmental Microbiology, v. 50, no. 2, p. 498-502. 

Conaway, C.H., S., S., Mason, R.P., and Flegal, A.R., 2003, Mercury speciation in the San Francisco Bay estuary: 

Marine Chemistry, v. 80, p. 199-225. 

CRWQCB, 2006, Mercury in San Francisco Bay: Proposed Basin Plan Amendment and Staff Report for Revised Total 

Maximum Daily Load (TMDL) and Proposed Mercury Water Quality Objectives: California Regional Water 

Quality Control Board - San Francisco Bay Region, 116 p. On-line: 

http://www.waterboards.ca.gov/sanfranciscobay/TMDL/sfbaymercurytmdl.htm

Davis, J.A., Yee, D., Collins, J.N., Schwarzbach, S.E., and Luoma, S.N., 2003, Potential for Increased Mercury 

Accumulation in the Estuary Food Web: San Francisco Estuary and Watershed Science, v. 1, no. 1/ article 4, p. 

1-36. 

DeWild, J.F., Olund, S.D., Olson, M.L., and Tate, M.T., 2004, Methods for the preparation and analysis of solids and 

suspended solids for methylmercury. Chapter 7 of Book 5, Laboratory Analysis; Section A, Water Analysis: U.S. 

Geological Survey, USGS Techniques and Methods Report 5 A 7p. 

EDAW, Philip Williams and Associates Ltd., H.T. Harvey and Associates, Brown and Caldwell, and Geomatrix, 2007, 

South Bay Salt Pond Restoration Project, Environmental Impact Statement / Report. Appendix G - Hydrology, 

Flood Management and Infrastructure Impact Analysis Support: Prepared for U.S. Army Corp of Engineers, U.S. 

Fish and Wildlife Service, and California Dept. of Fish and Game, DRAFT March 2007, 141 p. On-line: 

http://www.southbayrestoration.org/EIR/downloads.html

Gardner, J.V., Edwards, B.D., Dean, W.E., and Wilson, J., 1995, P-wave velocity, wet bulk density, magnetic 

susceptibility, acoustic impedance, and visual core descriptions of sediment recovered during Research Cruise 

EW9504: Data, techniques, and procedures: U.S. Geological Survey Open File Report 95-533, 288 p. 

Kayen, R.E., Edwards, B.D., and Lee, H.J., 1999, Nondestructive laboratory measurements of geotechnical and 

geoacoustic properties through intact core-liner, in Marr, W.A., and Fairhurst, C.E., eds., Nondestructive and 

Automated Testing for Soil and Rock Properties, ASTMSTP 1350, American Society for Testing and Materials, 

p. 83-94. 

Kieu, L.H., 2004, The Seasonal Influence of Saltmarsh Plants (Salicornia virginica and Scirpus robustus) on 

Methylmercury Production and Degradation Over Small Spatial Scales in South San Francisco Bay: San 

Francisco, San Francisco State University, Master's Thesis, 72 p. 

Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., Olson, J.F., 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 - 

Toxic Substance Hydrology Program., 99-4018B, 145-146 p. 

Lacerda, L.D., and Fitzgerald, W.F., 2001, Biogeochemistry of mercury in wetlands: Wetlands Ecol. Manag., v. 9, p. 

291-293. 

Life_Science!, 2003, South Bay Salt Ponds Initial Stewardship Plan: Prepared by Life Science! Inc. in cooperation 

with California Dept. of Fish and Game, and U.S. Fish and Wildlife Service, 251 p. On-line: 

http://www.southbayrestoration.org/ISPNews.html

16
References 

17

Livingstone, D.A., 1955, A Lightweight Piston Sampler for Lake Deposits: Ecology, v. 36, no. 1, p. 137-139. 

Marvin-DiPasquale, M., Hall, B.D., Flanders, J.R., Ladizinski, N., Agee, J.L., Kieu, L.H., and Windham-Myer, L., 2006, 

Ecosystem Investigations of Benthic Methylmercury Production: A Tin-Reduction Approach for Assessing the 

Inorganic Mercury Pool Available for Methylation, in Mercury 2006 Abstracts Book: Eighth International 

Conference on Mercury as a Global Pollutant, Madison, Wisconsin August 6-11, 2006. 

Matthes, W.J.J., 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. 

McKee, L., Leatherbarrow, J., and Oram, J., 2005, Concentrations and loads of mercury, PCBs, and OC pesticides in 

the lower Guadalupe River, San Jose, California: Water Years 2003 and 2004. A Technical Report of the 

Regional Watershed Program: San Francisco Estuary Institute, SFEI Contribution 409, 72 p. 

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. Chapter 8 of Book 5, Laboratory Analysis; Section A, Water Analysis: U.S. 

Geological Survey, USGS Techniques and Methods Report 5 A 8p. 

PWA, H.T. Harvey & Associates, EDAW, and Brown and Caldwell, 2006, South Bay Salt Ponds Restoration Project: 

Final Alternatives Report: Prepared for: California State Coastal Conservancy, U.S. Fish and Wildlife Service, 

California Department of Fish and Game., 47 p. On-line: 

http://www.southbayrestoration.org/Alternatives.html

Thomas, M.A., Conaway, C.H., Steding, D.J., Marvin-DiPasquale, M., Abu-Saba, K.E., and Flegal, A.R., 2002, 

Mercury contamination from historic mining in water and sediment, Guadalupe River and San Francisco Bay, 

California: Geochemistry: Exploration, Environment, Analysis, v. 2, p. 211-217. 

USEPA, 2002, Method 1631, Revision E: Mercury in water by oxidation, purge and trap, and cold vapor atomic 

fluorescence spectrometry: U.S. Environmental Protection Agency, Office of Water, EPA-821-R-02-019, 36 p. 

VBC, 2005, The California Bay-Delta Authority Mercury Studies Quality Assurance Program. Kick-Off Meeting. May 

19, 2005. Information Packet: Van Burren Consulting, LLCp. On-line: www.vanbuurenconsulting.com

VBC, and CDFG, 2005, Programmatic Quality Assurance and Quality Control for California Bay-Delta Authority 

(CBDA) Mercury Research and Monitoring Projects: Van Buuren Consulting, LLC and the California Department 

of Fish and Game, Annual Report for the California Bay-Delta Authority Projectp. On-line: 

http://www.calwater.ca.gov/content/erp_calfed_mercury_2005_project_annual_reports_content.asp

Wiener, J.G., Krabbenhoft, D.P., Heinz, G.H., and Scheuhammer, A.M., 2003, Ecotoxicology of mercury, Chapt. 16, in

Hoffman, D.J., Rattner, B.A., Burton, G.A., Jr., and Cairns, J., Jr., eds., Handbook of Ecotoxicology, 2nd edition: 

Boca Raton, CRC Press, p. 409-463. 

Zillioux, E.J., Porcella, D.B., and Benoit., J.M., 1993, Mercury cycling and effects in freshwater wetland ecosystems: 

Environ. Toxicol. Chem., v. 12, p. 2245-2264. 
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Figures 

New Almaden

Mining District

Alviso Slough

(study area)

Figure 1. Map of South San Francisco Bay, Alviso Slough and the New Almaden Mining 

District 

18
Figures 

Site Map – Biota, water and sediment sampling

T1

T5

T4 T3

T2

Alviso Slough Deep Core 

Sediment Sampling Sites Mouth

Mid-slough

A8 Bulge

d/s Marina

A8 Notch

D

C

B

A

Figure 2. Map showing location of Alviso Slough sediment sampling sites 

Sediment samples were collected between September 21 and 26, 2006, and included five transect 

groupings (T1 – T5). Each T# series consisted of three sampling locations, one in the primary slough 

channel (blue circle; B-series sites on Figures 3-12), one each on the right and left fringing marsh plains 

(green circles; A and C-series sites, respectively, on Figures 3-12). Also depicted are the PWA cross 

channel transect locations (orange lines) where slough geometry was previously determined, along with 

the transect line names (orange text boxes). The four slough segments (A – D, yellow text boxes) are 

bounded by the upper and lower cross channel transect lines and the existing levee wall, and include the 

slough channel plus the fringing marsh plain. 

19
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

20

Core Sampling Schematic

(looking downstream)

T#-C

(left marsh)

T#-A

(right marsh)

T#-B

(channel)

2 meters

2 meters

2 meters

D1

D2 D3

D1

D2 D3

D1

D2 D3

Figure 3. Illustration of slough cross section and sediment sampling design 

The slough cross section illustration is orientated facing downstream and depicts the sediment sampling 

design associated with a generic sediment Transect (T#), including A (right marsh), B (slough channel), 

and C (left marsh) series sites. In the vertical, multiple cores were taken to a total depth of 

approximately 200 cm, from discrete depth intervals (D1-D3) that were slightly offset to allow for 

interval overlap. Also depicted is the theoretical slough scour (not to scale) associated with the two 

proposed Pond A8 levee notch scenarios (e.g. 20-foot and 40-foot wide notches).
0

50

100150200250

0

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

0

50

100150200250

0123

T5-C

T5-B

T4-C

T4-B

T4-A

T3-CT3-BT3-A

T2-C

T2-B

T2-A

0

50

100150200250

0123

0

50

100150200250

0

0

50

100150200250

0

Total Mercury (μg/cm3)

T5-A T1

T1

T1

Depth Inte[0-200 cm] 

1.05

1.27

0.92

1.17

1.77

1.08

1.25

1.87

1.32

0.88

1.12

0.88

Sediment depth (cm)

Figure 4. Depth profiles of sediment total mercury concentration Alviso Slough total mercury (THg) concentration as a function of sediment dep th, where the symbol identifies thdepth interval sampled and the associated vertical bars indicate the total interval vertical width. The aerial 0-200 THg concentration (in g/m2) is also given for each profile. Panel layout parallels the approximate orientation of t

depicted in Figure 2, and individual background colors (blue or green) reflect marsh or slough channel sites, resp

21
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

0

50

100150200250

01234

0

50

100150200250

01234

0

50

100150200250

01234

0

50

100150200250

01234

0

50

100150200250

01234

0

50

100150200250

01234

0

50

100150200250

0

0

50

100150200250

0

0

50

100150200250

0

T

Methylmercury (ng/cm

3

)

T5-A

T5-B

T5-C

T

T

T3-AT3-BT3-C

De

[0-20

1.06 

1.41

1.18 0.81

0.96

0.83

Figure 5. Depth profiles of sediment methylmercury concentration Alviso Slough methylmercury (MeHg) concentration as a function of sediment depth, where the symbol identifieeach depth interval sampled and the associated vertical bars indicate the total interval width. The aerial 0-200 cm 

MeHg concentration (in mg/m2) is also given for each profile. Panel layout parallels the approximate orientation 

as depicted in Figure 2, and individual background colors (blue or green) reflect marsh or slough channel sites, r

22
050100150200250

0 0.1 1 10

T5-C

050100150200250

0 0.1 1 10

T5-B

050100150200250

0 0.1 1 10

T5-A

% Reactive Mercury (Hg(II)R)

0 

0.0 

T1-

T1-

0 

T1-

050100150200250

0 0.1 1 10

050100150200250

0 0.1 1 10

T3-C

T3-B

T3-A

Dept[0-20

1.08

0.35

0.30

1.05

0.53

0.85

050100150200250

0.0 0.01 0.1 1 10

Figure 6. Depth profiles of sediment reactive inorganic mercury as a percentage of total mercury 

Alviso Slough reactive inorganic mercury (Hg(II)R) concentration as a percentage (%) of total mercury and as a f

depth, where the symbol identifies the mid-point of each depth interval sampled and the associated vertical bars i

interval width. The aerial 0-200 cm depth integrated Hg(II)R concentration (in mg/m2) is also given for each profparallels the approximate orientation of the individual sites as depicted in Figure 2, and individual background creflect marsh or slough channel sites, respectively. 

23
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6.5 7.0 7.5 8.0

T2-B

0

50

100150200250

6.5 7.0 7.5 8.0

0

50

100150200250

6

0

50

100150200250

6

0

50

100150200250

6

Alviso Slough Deep Cores (September 2006) - 

T5-A

T5-B

T5-C

T2-A

T2-C

T3-A

T3-B

T3-C

T4-A

T4-B

T4-C

Sediment depth (cm)

Figure 7. Depth profiles of sediment pH Alviso Slough pH as a function of sediment depth, where the symbol identifies the mid-point of each depth intervassociated vertical bars indicate the total interval width. Panel layout parallels the approximate orientation of the depicted in Figure 2, and individual background colors (blue or green) reflect marsh or slough channel sites, resp

24
050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100

150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

050100150200250

-200 0 200

-200 

-200 

-200 

Oxidation-Reduction Potential: Eh (mV)

T5-A

T5-B

T5-C

T2-A

T2-B

T2-C

T3-A

T3-B

T3-C

T4-A

T4-B

T4-C

Figure 8. Depth profiles of sediment oxidation-reduction potential Alviso Slough oxidation-reduction measurement (expressed as Eh) as a function of sediment depth, where the sym

mid-point of each depth interval sampled and the associated vertical bars indicate the total interval width. Panel l

approximate orientation of the individual sites as depicted in Figure 2, and individual background colors (blue o

or slough channel sites, respectively. 

25
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

0

50

100150200250

0 510

Organic Content (%LOI)

T5-A

T5-B

T5-C

T2-A

T2-B

T2-C

T3-A

T3-B

T3-C

T4-A

T4-BT4-C

Sediment depth (cm)

Figure 9. Depth profiles of sediment organic content Alviso Slough sediment organic content (expressed as percent weight loss on ignition (% LOI)) as a function of sthe symbol identifies the mid-point of each depth interval sampled and the associated vertical bars indicate the toPanel layout parallels the approximate orientation of the individual sites as depicted in Figure 2, and individual b(blue or green) reflect marsh or slough channel sites, respectively. 

26
0

50

100150200

250

0 20 40 60 80 100

0

50

100

150

200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

0

50

100150200250

0 20 40 60 80 100

Grain Size (% < 63 μm)

T5-A

T5-B

T5-C

T2-A

T2-B

T2-C

T3-AT3-BT3-C

T4-A

T4-B

T4-C

Sediment depth (cm)

Figure 10. Depth profiles of sediment grain size Alviso Slough sediment grain size (expressed as weight percent less than 63 micrometers (% < 63 μm)) as a func

depth, where the symbol identifies the mid-point of each depth interval sampled and the associated vertical bars i

interval width. Panel layout parallels the approximate orientation of the individual sites as depicted in Figure 2, abackground colors (blue or green) reflect marsh or slough channel sites, respectively. 

27
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Sediment Gamma Density & Bulk Density (g/cm

0

50

100150200

1 1.5 2

0

50

100150200

1 1.5 2

0

50

100150200

1 1.5 2

T5-A

T5-BT5-C

0

50

101520

0

50

100150200

0

50

100150200

0

50

100150200

1 1.5 2

0

50

100

150

200

1 1.5 2

0

50

100150200

1 1.5 2

T2-A

T2-B

T2-C

0

50

100150200

1 1.5 2

0

50

100150200

1 1.5 2

0

50

100150200

1 1.5 2

T3-A

T3-BT3-C

0

50

100150200

1 1.5 2

0

50

100150200

1 1.5 2

T4-A

T4-B

T4-C

0

50

100150200

1 1.5 2

Sediment depth (cm)

Figure 11. Depth profiles of sediment density Alviso Slough sediment density as a function of sediment depth. Two approaches are depicted: a) Multi-Sensor cnon-invasive scans conducted with gamma irradiation, where the various colors represent data from individual codensity measured as the ratio of directly measured sediment weight to volume for discrete depth intervals, where the mid-point of each depth interval sampled and the associated vertical bars indicate the total interval width. Panapproximate orientation of the individual sites as depicted in Figure 2, and individual background colors (blue oor slough channel sites, respectively. 

28
Magnetic Susceptibility (cm/g/s) x 10-6

0

50

100150200

0 20 40 60

0

50

100150

200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

0

50

100150200

0 20 40 60

050100150

200

0 20 40 60

T5-A

T5-B

T5-C

T2-A

T2-B

T2-C

T3-A

T3-B

T3-C

T4-A

T4-B

T4-C

Figure 12. Depth profiles of sediment magnetic susceptibility Alviso Slough sediment magnetic susceptibility scans as a function of sediment depth, as measured with the nonSensor core logger (MSCL), where the various colors represent data from individual cores. Panel layout parallels orientation of the individual sites as depicted in Figure 2, and individual background colors (blue or green) reflechannel sites, respectively. 

29
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

30

0

50

100150200250300

0123456

Days

Slurry Hg(II)R concentration (ng/L)

low salinity / anoxic

high salinity / anoxic

low salinity / oxic

high salinity / oxic

Changes in reactive inorganic mercury (Hg(II)

R) concentrations in sediment / overlying slough water slurries rep

7 days, under four treatment conditions (see inset legend). Error bars reflect the relative difference of n=2 sub-sa

and time point. When not shown, error bars were smaller than the treatment symbol. Figure 13. Time course plot of reactive mercury concentrations associated with the slough scour simu
Tables 

Tables 

Table 1. Sediment sampling locations, Alviso Slough, September 2006 

Site Name Site Description1 Latitude2Longitude2

AS-T1A Right Marsh 37o 25’ 57.0” 121o 59’ 19.1” 

AS-T1B Slough Channel 37o

 25’ 54.7” 121o 59’ 18.8” 

AS-T1C Left Marsh 37o

 25’ 53.9” 121o 59’ 19.9” 

AS-T2A Right Marsh 37o

 26’ 21.3” 121o 59’ 35.1” 

AS-T2B Slough Channel 37o

 25’ 54.7” 121o 59’ 18.8” 

AS-T2C Left Marsh 37o

 26’ 15.7” 121o 59’ 36.3” 

AS-T3A Right Marsh 37o

 26’ 28.9” 122o 00’ 07.3” 

AS-T3B Slough Channel 37o

 26’ 24.5” 122o 00’ 04.7” 

AS-T3C Left Marsh 37o

 26’ 23.2” 122o 00’ 05.5” 

AS-T4A Right Marsh 34o

 26’ 39.3” 122o 00’ 18.1” 

AS-T4B Slough Channel 37o

 26’ 37.7” 122o 00’ 20.3” 

AS-T4C Left Marsh 37o

 26’ 36.5” 122o 00’ 23.0” 

AS-T5A Right Marsh 37o

 26’ 51.6” 122o 01’ 05.6” 

AS-T5B Slough Channel 37o

 26’ 49.3” 122o 01’ 08.2” 

AS-T5C Left Marsh 37o

 26’ 48.1” 122o 01’ 09.1” 

1 Site orientation looking downstream 

2 Datum, WGS 84

31
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Table 2. Sediment Mercury Species Concentration The deviation of n = 2 samples, when assayed, is given in parentheses ( ), and the type of replication is indicated by the cell coindicate analytical duplicates from the same sub-sample vial and green cell indicate sub-sample duplicates from the original cor

at the time of initial core processing. Profile averages (mean ± standard deviation) of mercury species concentrations are given weighted by depth interval width. Summary statistics for the complete data set are given at the bottom of the Table. [THg, total reactive mercury; MeHg, methylmercury; cm, centimeters; μg/g, micrograms per gram sediment (dry weight); ng/g, nanograms weight); <, less than given detection limit; %, percentage of total mercury; NS, no sample collected]. 

Site ID and 

Core1

Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T1 A-D1 0-20 0-20 1.17 0.75 2.34 

AS T1 A-D1 20-46 20-46 0.54 0.28 1.80 

AS T1 A-D2 50-69 0-19 1.03 (0.02) 0.56 1.33 AS T1 A-D2 69-88 19-38 0.80 0.25 0.50 

AS T1 A-D2 88-107 38-57 0.65 0.25 0.61 

AS T1 A-D2 107-126 57-76 0.68 0.18 0.99 

AS T1 A-D3 126-145 1-20 1.32 0.22 < 0.35 

AS T1 A-D3 145-165 20-40 0.99 0.18 0.68 

AS T1 A-D3 165-185 40-60 1.39 0.16 0.57 

AS T1 A-D3 185-203 60-77.5 1.34 0.22 0.94 

AS T1 A MEAN 

± (std. dev.) 0.98 (0.31) 0.31 (0.19) 1.04 (0.66) 

AS T1 B-D1 0-20 0-20 0.56 0.29 1.24 

AS T1 B-D1 20-40 20-40 0.47 0.46 1.39 

AS T1 B-D1 40-60 40-60 0.54 0.52 0.89 

AS T1 B-D1 60-83 60-83 0.61 (0.06) 0.47 (0.10) 0.90 (0.05) 

AS T1 B-D2 83-100 33-50 0.51 (0.04) 0.62 0.68 AS T1 B-D2 100-117 50-67 0.66 0.33 0.89 

AS T1 B-D2 117-135 67-84.5 0.80 0.58 0.83 

AS T1 B-D3 135-152 5-22 0.96 0.43 2.21 

32
Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)

Site ID and 

Core1 R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T1 B-D3 152-180 22-50 0.84 (0.06) 0.11 1.10 AS T1 B-D3 180-209 50-78.5 1.13 0.17 0.62 

AS T1 B MEAN ± (std. dev.) 0.73 (0.22) 0.37 (0.16) 1.05 (0.45) 

AS T1 C-D1 0-18 0-18 1.37 (0.11) 11.73 0.97 AS T1 C-D1 18-40 18-40 0.64 0.26 6.10 

AS T1 C-D1 40-60 40-60 1.36 0.35 1.33 

AS T1 C-D2 60-80 10-30 0.79 (0.10) 0.17 (0.01) 1.22 (0.16) 

AS T1 C-D2 80-98 30-48 0.91 (0.21) 0.23 0.85 AS T1 C-D2 98-116 48-66 1.22 (0.02) 0.21 0.50 AS T1 C-D3 116-135 1-20 1.12 (0.01) 0.17 0.55 AS T1 C-D3 135-155 20-40 0.60 0.16 0.56 

AS T1 C-D3 155-175 40-60 0.75 0.15 0.59 

AS T1 C-D3 175-196 60-81 1.04 0.30 2.34 (0.04) 

AS T1 C MEAN ± (std. dev.) 0.97 (0.28) 1.28 (3.39) 1.58 (1.80) 

AS T2 A-D1 2-12 2-12 0.52 NS NS AS T2 A-D1 12-23 12-23 0.67 NS NS AS T2 A-D2 23-40 3-20 0.84 NS NS 

AS T2 A-D2 40-70 20-50 0.73 (0.01) NS NS AS T2 A-D2 70-88 50-68 0.60 NS NS 

AS T2 A-D3 88-113 3-28 1.08 NS NS 

AS T2 A-D3 113-134 28-49 0.90 NS NS 

AS T2 A-D3 134-165 49-80 1.00 (0.12) NS NS AS T2 A-D4 165-194 25-54 1.02 NS NS 

AS T2 A-D4 194-212 54-72 2.83 NS NS 

AS T2 A MEAN ± (std. dev.) 1.03 (0.67) 

AS T2 B-D1 0-16 0-16 0.67 NS NS 

AS T2 B-D1 16-37 16-37 0.91 NS NS 

33
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)

Site ID and 

Core1

R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T2 B-D1 37-54 37-54 1.17 NS NS 

AS T2 B-D1 54-93 54-73 0.91 (0.15) NS NS AS T2 B-D2 97-124 12-39 0.87 NS NS 

AS T2 B-D2 124-144 39-59 0.53 NS NS 

AS T2 B-D2 144-175 59-90 0.99 NS NS 

AS T2 B-D3 175-201 25-51 1.81 (0.01) NS NS AS T2 B-D3 201-231 51-81 2.47 NS NS 

AS T2 B MEAN 

± (std. dev.) 1.19 (0.64) 

AS T2 C-D1 0-12 0-12 0.60 NS NS 

AS T2 C-D1 12-24 12-24 0.65 NS NS AS T2 C-D1" 24-37 4-17 0.62 NS NS AS T2 C-D1" 37-50 17-30 0.51 NS NS AS T2 C-D2 50-75 0-25 0.75 NS NS 

AS T2 C-D2 75-103 25-53 0.73 (0.05) NS NS AS T2 C-D2 103-129 53-79 0.77 NS NS 

AS T2 C-D3 129-147 4-22 0.61 NS NS 

AS T2 C-D3 147-183 22-58 0.79 NS NS 

AS T2 C-D3 183-204 58-79 1.42 (0.19) NS NS 

AS T2 C MEAN 

± (std. dev.) 0.78 (0.26) 

AS T3 A-D1 0-15 0-15 0.57 6.90 2.14 

AS T3 A-D1 15-46 15-46 0.68 0.36 3.04 

AS T3 A-D2 46-72 1-27 0.72 (0.03) 0.34 0.72 AS T3 A-D2 72-98 27-53 0.83 0.35 < 0.33 

AS T3 A-D2 98-124 53-79 0.99 0.27 0.43 

AS T3 A-D3 127-157 2-32 0.78 0.35 0.52 

AS T3 A-D3 157-189 32-64 1.85 0.52 1.17 

AS T3 A-D3 189-209 64-83 1.34 0.57 1.87 

AS T3 A MEAN 

± (std. dev.) 0.99 (0.44) 0.87 (1.65) 1.24 (0.95) 

34
Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)

Site ID and 

Core1 R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T3 B-D1 0-8 0-8 0.31 0.09 0.47 

AS T3 B-D1 8-40 8-40 1.16 (0.15) 0.24 (0.01) 1.66 (0.11) 

AS T3 B-D1 40-70 40-70 1.75 (0.08) 0.30 0.85 

AS T3 B-D2 70-108 10-48 0.75 0.21 0.64 (0.08) AS T3 B-D2 108-133 48-73 1.07 0.24 0.42 

AS T3 B-D2 133-143 73-83 0.54 0.27 0.27 

AS T3 B-D3 143-172 13-42 0.89 0.30 < 0.21 

AS T3 B-D3 172-212 42-82 0.85 (0.47) 0.52 (0.04) < 0.28 (0.00) 

AS T3 B MEAN ± (std. dev.) 1.00 (0.47) 0.29 (0.12) 0.65 (0.52) 

AS T3 C-D1 0-12 0-12 0.55 8.17 1.07 (0.02) AS T3 C-D1 12-45 12-45 0.67 0.32 1.55 AS T3 C-D2 45-64 0-19 0.62 0.18 0.87 AS T3 C-D2 64-91 19-46 0.86 0.18 0.45 

AS T3 C-D2 91-127 46-82 0.97 (0.01) 0.14 0.43 AS T3 C-D3 127-181 2-56 1.31 0.33 0.53 

AS T3 C-D3 181-199 56-74 0.94 0.02 < 0.30 

AS T3 C MEAN ± (std. dev.) 0.94 (0.29) 0.70 (1.59) 0.71 (0.43) 

AS T4 A-D1 0-19.5 0-19.5 0.54 NS NS 

AS T4 A-D1 19.5-31 19.5-31 0.72 NS NS 

AS T4 A-D2 31-50 1-20 0.62 NS NS 

AS T4 A-D2 50-70 20-40 0.57 NS NS 

AS T4 A-D2 70-100 40-70 0.83 NS NS 

AS T4 A-D3 100-115 10-25 1.49 NS NS 

AS T4 A-D3 115-150 25-60 0.59 NS NS 

AS T4 A-D3 150-174 60-84 1.75 NS NS 

AS T4 A-D4 174-200 44-70 1.45 NS NS 

AS T4 A MEAN ± (std. dev.) 0.95 (0.47) 

35
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)

Site ID and 

Core1

R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T4 B-D1 0-7.5 0-7.5 0.49 NS NS 

AS T4 B-D1 7.5-20 7.5-20 0.20 NS NS 

AS T4 B-D1 20-56 20-56 0.84 (0.00) NS NS 

AS T4 B-D1 56-93 56-93 1.52 NS NS 

AS T4 B-D2 93-106 13-26 1.81 NS NS 

AS T4 B-D2 106-109 26-29 1.51 NS NS 

AS T4 B-D2 109-123 29-42.5 2.37 NS NS 

AS T4 B-D2 123-133 42.5-52.5 1.12 NS NS 

AS T4 B-D2 133-144 52.5-63.5 1.40 NS NS 

AS T4 B-D2 144-156 63.5-76 0.08 NS NS 

AS T4 B-D3 156-183 16-43 0.69 NS NS 

AS T4 B-D3 183-196 43-56 0.91 NS NS 

AS T4 B MEAN 

± (std. dev.) 1.08 (0.68) 

AS T4 C-D1 0-17 0-17 0.48 NS NS 

AS T4 C-D1 17-40 17-40 0.65 (0.02) NS NS 

AS T4 C-D1 40-64 40-64 1.26 NS NS 

AS T4 C-D2 64-100 14-50 0.80 NS NS 

AS T4 C-D2 100-131 50-81 1.97 NS NS 

AS T4 C-D3 131-151 1-21 0.91 NS NS 

AS T4 C-D3 151-174 21-44 1.01 NS NS 

AS T4 C-D3 174-199 44-68.5 0.83 NS NS 

AS T4 C MEAN 

± (std. dev.) 1.03 (0.48) 

AS T5 A-D1 0-12.5 0-12.5 0.54 4.17 0.79 

AS T5 A-D1 12.5-27.3 12.5-27.3 0.73 0.41 1.14 

AS T5 A-D2 20-30 0-10 0.50 10.02 < 0.30 

AS T5 A-D2 30-40 10-20 0.49 (0.01) 0.25 1.38 AS T5 A-D2 40-70 20-50 0.59 0.33 < 0.33 

AS T5 A-D2 70-101 50-81 0.67 (0.00) 0.24 0.46 (0.01) 

36
Site ID and 

Core1

Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

AS T5 A-D3 85-101 0-20 0.94 0.21 0.66 (0.04) 

AS T5 A-D3 105-125 20-40 0.53 0.22 < 0.32 

AS T5 A-D3 125-157 40-71 0.52 0.20 0.59 

AS T5 A-D4 145-185 0-40 0.51 (0.02) 0.16 (0.01) 0.63 (0.02) 

AS T5 A-D4 185-200 40-55 1.43 (0.00) 0.21 0.76 

AS T5 A-D4 200-228 55-82 1.41 0.17 < 0.32 

AS T5 A MEAN ± (std. dev.) 0.73 (0.34) 0.80 (1.70) 0.58 (0.31) 

AS T5 B-D1 0-20 0-20 0.36 0.18 0.97 (0.02) 

AS T5 B-D1 20-50 20-50 0.59 0.12 0.51 AS T5 B-D1 50-79 50-79 1.01 0.32 < 0.31 

AS T5 B-D2 79-94 9-24 1.16 0.23 0.87 

AS T5 B-D2 94-130 24-60 0.82 (0.04) 0.21 0.70 

AS T5 B-D2 130-166 60-96 0.88 0.34 0.72 

AS T5 B-D3 167-202 17-52 0.90 (0.00) 0.34 (0.10) 0.83 (0.02) 

AS T5 B-D3 202-212 52-62 0.54 0.21 0.38 

AS T5 B MEAN ± (std. dev.) 0.80 (0.27) 0.25 (0.08) 0.67 (0.24) 

AS T5 C-D1 0-15 0-15 0.41 0.45 5.82 

AS T5 C-D1 15-30 15-30 0.50 0.13 1.18 (0.05) 

AS T5 C-D1 30-49 30-49 0.64 0.06 < 0.37 AS T5 C-D2 50-81 0-31 0.68 0.37 0.67 

AS T5 C-D2 81-112 31-62 0.78 0.12 < 0.35 

AS T5 C-D2" 112-130 40-58 0.68 0.11 < 0.35 AS T5 C-D3 130-150 10-30 1.75 0.44 0.56 

AS T5 C-D3 150-175 30-55 0.66 0.16 0.53 

AS T5 C-D3 175-198 55-78 0.99 0.49 0.78 

AS T5 C MEAN ± (std. dev.) 0.80 (0.40) 0.26 (0.17) 0.98 (1.46) 

ALL DATA MEAN 0.93 0.35 0.56 

37
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Site ID and 

Core1

Field: Depth 

interval2

Core: Depth 

Interval3 THg Hg(II)R MeHg Hg

(cm) (cm) (μg/g) (ng/g) (ng/g) (%

ALL DATA STD. DEV. 0.45 0.91 0.56 

ALL DATA STD. ERR. 0.04 0.10 0.06 

ALL DATA MEDIAN 0.80 0.25 0.69 

ALL DATA MINIMUM 0.08 0.02 < 0.21 ALL DATA MAXIMUM 2.83 11.73 6.10 

ALL DATA TOTAL N 140 82 82 

1 Core coding: AS T# [A, B or C]-D#; where AS = Alviso Slough; T# = Transect number (1 thru 5); [A, B or C] = Site descript

marsh, right marsh or slough channel, respectively); D# = depth specific core segment 

2 Field depth interval measured from the sediment / water interface 3 Core depth interval measured from the top of the individual core liner 

38
Table 3. Ancillary Sediment Parameters Profile averages (mean ± standard deviation) for each parameter are given in bold, with data weighted by depth interval width. the complete data set are given at the bottom of the Table. [pH in standard units; Eh, oxidation-reduction potential corrected for 

reference half-reaction; LOI, loss on ignition, a measure of sediment organic content; cm, centimeters; mV, millivolts; %, perce

wet sediment per cubic centimeter; ml/cm3, milliliters of pore water per cubic centimeter of wet sediment; % <63 μm; percenta

weight) less than 63 micrometers, representing the sand/silt size fraction cut-off]. 

Field: Depth 

interval2

Core: Depth 

Interval3 pH Eh

Dry 

weight LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1

) m (ml/c 3 (cm) (cm) (mV) (%) (%) (g/cm ) (% < 63 

3

AS T1 A-D1 0-20 0-20 7.25 65 49.2 7.78 1.33 0.68 AS T1 A-D1 20-46 20-46 7.21 -40 46.9 7.17 1.33 0.71 

AS T1 A-D2 50-69 0-19 7.33 -2 44.5 6.42 1.28 0.71 

AS T1 A-D2 69-88 19-38 7.41 -46 43.9 5.71 1.35 0.76 

AS T1 A-D2 88-107 38-57 7.48 -55 43.6 5.72 1.28 0.72 

AS T1 A-D2 107-126 57-76 7.53 -108 43.7 6.25 1.23 0.69 

AS T1 A-D3 126-145 1-20 7.59 -68 45.7 6.72 1.21 0.66 AS T1 A-D3 145-165 20-40 7.64 -91 48.2 5.34 1.30 0.67 

AS T1 A-D3 165-185 40-60 7.62 -48 47.0 6.27 1.33 0.71 

AS T1 A-D3 185-203 60-77.5 7.61 -101 49.9 5.46 1.35 0.67 

AS T1 A MEAN 7.46 -48 46.3 6.32 1.30 0.70 

Std. Dev. 0.16 50 2.4 0.78 0.05 0.03 

AS T1 B-D1 0-20 0-20 7.09 -20 44.1 6.04 1.28 0.71 AS T1 B-D1 20-40 20-40 7.32 -28 43.3 6.15 1.29 0.73 

AS T1 B-D1 40-60 40-60 7.3 -26 42.4 6.04 1.28 0.74 AS T1 B-D1 60-83 60-83 7.36 -29 44.6 4.65 1.30 0.72 AS T1 B-D2 83-100 33-50 7.29 -11 42.5 6.04 1.30 0.74 

AS T1 B-D2 100-117 50-67 7.39 -32 43.7 5.90 1.32 0.74 

AS T1 B-D2 117-135 67-84.5 7.34 -34 44.0 5.18 1.32 0.74 

AS T1 B-D3 135-152 5-22 7.34 -25 50.7 5.26 1.39 0.69 

AS T1 B-D3 152-180 22-50 7.55 -71 46.2 5.15 1.29 0.70 AS T1 B-D3 180-209 50-78.5 7.58 -58 46.1 5.61 1.34 0.72 

39
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Field: Depth 

interval2

Core: Depth 

Interval3 H Eh

Dry 

weigh LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1

p t

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T1 B MEAN 7.37 -36 44.8 5.57 1.31 0.72 

Std. Dev. 0.14 19 2.5 0.51 0.03 0.02 

AS T1 C-D1 0-18 0-18 7.19 259 48.9 7.95 1.30 0.67 AS T1 C-D1 18-40 18-40 7.17 -28 45.0 4.97 1.29 0.71 AS T1 C-D1 40-60 40-60 7.56 -53 43.5 4.57 1.33 0.75 

AS T1 C-D2 60-80 10-30 7.61 -55 46.0 5.26 1.35 0.73 AS T1 C-D2 80-98 30-48 7.6 -30 44.2 5.13 1.33 0.74 

AS T1 C-D2 98-116 48-66 7.6 -57 46.0 4.45 1.38 0.75 

AS T1 C-D3 116-135 1-20 7.57 -5 46.1 4.82 1.32 0.71 

AS T1 C-D3 135-155 20-40 7.76 -86 44.1 3.78 1.29 0.72 

AS T1 C-D3 155-175 40-60 7.61 -97 45.3 4.05 1.32 0.72 

AS T1 C-D3 175-196 60-81 7.49 -55 46.3 4.34 1.34 0.72 

AS T1 C MEAN 7.51 -24 45.5 4.90 1.33 0.72 

Std. Dev. 0.19 115 1.5 1.15 0.03 0.02 

AS T2 A-D1 2-12 2-12 7.06 104 44.4 8.80 1.29 0.72 

AS T2 A-D1 12-23 12-23 7.1 -25 45.5 6.97 1.28 0.70 AS T2 A-D2 23-40 3-20 7.36 -60 44.5 6.50 1.31 0.72 AS T2 A-D2 40-70 20-50 7.42 -79 43.2 6.49 1.30 0.74 AS T2 A-D2 70-88 50-68 7.53 -91 41.3 5.98 1.28 0.75 AS T2 A-D3 88-113 3-28 7.65 -19 43.7 5.88 1.34 0.75 AS T2 A-D3 113-134 28-49 7.55 -53 43.7 5.66 1.31 0.74 

AS T2 A-D3 134-165 49-80 7.53 -112 45.1 6.38 1.29 0.71 

AS T2 A-D4 165-194 25-54 7.57 -52 43.5 5.27 1.30 0.73 

AS T2 A-D4 194-212 54-72 7.43 -73 44.0 6.48 1.34 0.75 

AS T2 A MEAN 7.47 -58 43.8 6.24 1.30 0.73 

Std. Dev. 0.20 75 1.2 0.93 0.02 0.02 

AS T2 B-D1 0-16 0-16 7.58 3 45.7 5.35 1.33 0.72 AS T2 B-D1 16-37 16-37 7.46 -25 46.0 5.66 1.37 0.74 

40
Field: Depth 

interval2

Core: Depth 

Interval3 H Eh

Dry 

weigh LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1 p t

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T2 B-D1 37-54 37-54 7.62 -91 46.0 5.46 1.34 0.72 AS T2 B-D1 54-93 54-73 7.68 -100 45.1 5.32 1.36 0.74 AS T2 B-D2 97-124 12-39 7.53 -63 45.5 5.27 1.35 0.73 AS T2 B-D2 124-144 39-59 7.58 -79 44.2 4.76 1.34 0.75 

AS T2 B-D2 144-175 59-90 7.38 -74 46.1 4.79 1.37 0.74 

AS T2 B-D3 175-201 25-51 7.42 -50 49.3 4.83 1.43 0.73 

AS T2 B-D3 201-231 51-81 7.47 -104 49.6 5.44 1.40 0.71 

AS T2 B MEAN 7.52 -70 46.5 5.20 1.37 0.73 

Std. Dev. 0.10 39 1.8 0.33 0.03 0.01 

AS T2 C-D1 0-12 0-12 6.69 213 48.9 7.26 1.39 0.71 AS T2 C-D1 12-24 12-24 7.15 72 45.4 7.03 1.35 0.74 

AS T2 C-D1" 24-37 4-17 7.09 242 46.3 7.32 1.33 0.72 AS T2 C-D1" 37-50 17-30 7.29 32 43.1 7.27 1.31 0.75 

AS T2 C-D2 50-75 0-25 7.4 28 43.3 5.98 1.33 0.76 

AS T2 C-D2 75-103 25-53 7.51 -50 45.5 4.31 1.35 0.74 AS T2 C-D2 103-129 53-79 7.56 -54 44.4 4.44 1.36 0.75 

AS T2 C-D3 129-147 4-22 7.59 -49 43.0 5.37 1.32 0.75 AS T2 C-D3 147-183 22-58 7.62 -83 43.7 5.93 1.33 0.75 

AS T2 C-D3 183-204 58-79 7.48 -91 46.0 4.81 1.36 0.74 

AS T2 C MEAN 7.42 -4 44.7 5.68 1.34 0.74 

Std. Dev. 0.29 21 1.8 1.15 0.02 0.02 

AS T3 A-D1 0-15 0-15 7.27 252 45.4 8.21 1.34 0.73 

AS T3 A-D1 15-46 15-46 7.47 -49 42.9 6.69 1.32 0.75 

AS T3 A-D2 46-72 1-27 7.43 -9 42.5 5.59 1.32 0.76 

AS T3 A-D2 72-98 27-53 7.56 -43 45.4 5.37 1.36 0.74 AS T3 A-D2 98-124 53-79 7.64 -39 46.9 5.51 1.38 0.73 

AS T3 A-D3 127-157 2-32 7.53 5 43.8 6.06 1.33 0.75 

AS T3 A-D3 157-189 32-64 7.56 -6 44.6 6.38 1.32 0.73 

AS T3 A-D3 189-209 64-83 7.6 -61 46.5 6.72 1.35 0.72 

41
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Field: Depth 

interval2

Core: Depth 

Interval3 H Eh

Dry 

weigh LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1

p t

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T3 A MEAN 7.52 -7 44.6 6.21 1.34 0.74 

Std. Dev. 0.12 110 1.6 0.91 0.02 0.01 

AS T3 B-D1 0-8 0-8 7.5 5 69.4 3.15 1.73 0.53 AS T3 B-D1 8-40 8-40 7.65 -98 49.8 4.81 1.39 0.70 AS T3 B-D1 40-70 40-70 7.65 -161 47.4 5.33 1.38 0.72 AS T3 B-D2 70-108 10-48 7.56 -102 48.4 5.79 1.39 0.72 AS T3 B-D2 108-133 48-73 7.62 -107 70.1 2.91 1.76 0.53 AS T3 B-D2 133-143 73-83 7.75 -81 78.3 2.63 1.88 0.41 

AS T3 B-D3 143-172 13-42 7.55 -89 69.5 3.37 1.70 0.52 

AS T3 B-D3 172-212 42-82 7.53 -2 61.3 3.61 1.57 0.61 

AS T3 B MEAN 7.59 -85 58.5 4.25 1.54 0.62 

Std. Dev. 0.08 59 11.3 1.28 0.19 0.12 

AS T3 C-D1 0-12 0-12 6.91 223 46.8 8.94 1.34 0.71 AS T3 C-D1 12-45 12-45 7.16 -134 42.9 7.33 1.31 0.75 AS T3 C-D2 45-64 0-19 7.14 -5 40.3 6.95 1.28 0.76 AS T3 C-D2 64-91 19-46 7.23 -30 41.7 7.09 1.32 0.77 AS T3 C-D2 91-127 46-82 7.39 -82 43.4 6.18 1.33 0.75 AS T3 C-D3 127-181 2-56 7.47 -40 42.9 5.80 1.33 0.76 

AS T3 C-D3 181-199 56-74 7.67 -143 49.0 6.73 1.39 0.71 

AS T3 C MEAN 7.32 -52 43.4 6.68 1.33 0.75 

Std. Dev. 0.25 213 3.0 0.96 0.03 0.02 

AS T4 A-D1 0-19.5 0-19.5 7.38 212 54.6 8.20 1.42 0.64 AS T4 A-D1 19.5-31 19.5-31 7.43 68 54.1 6.43 1.45 0.67 AS T4 A-D2 31-50 1-20 7.35 25 50.7 6.74 1.39 0.69 AS T4 A-D2 50-70 20-40 7.43 -112 48.8 7.02 1.36 0.70 

AS T4 A-D2 70-100 40-70 7.53 -138 48.6 5.27 1.38 0.71 

AS T4 A-D3 100-115 10-25 7.46 -130 47.6 5.48 1.37 0.72 

AS T4 A-D3 115-150 25-60 7.46 -76 46.2 4.89 1.35 0.73 

42
Field: Depth 

interval2

Core: Depth 

Interval3 H Eh

Dry 

weigh LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1 p t

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T4 A-D3 150-174 60-84 7.43 -100 47.0 5.45 1.37 0.73 

AS T4 A-D4 174-200 44-70 7.39 -65 45.8 5.86 1.33 0.72 

AS T4 A MEAN 7.43 -48 48.7 5.98 1.37 0.70 

Std. Dev. 0.05 160 3.2 1.02 0.04 0.03 

AS T4 B-D1 0-7.5 0-7.5 7.29 -130 44.5 5.61 1.34 0.75 

AS T4 B-D1 7.5-20 7.5-20 7.78 100 80.3 1.38 1.82 0.36 

AS T4 B-D1 20-56 20-56 7.63 -113 51.5 4.24 1.41 0.68 AS T4 B-D1 56-93 56-93 7.48 -162 46.2 5.12 1.33 0.72 AS T4 B-D2 93-106 13-26 7.44 -8 59.0 4.91 1.52 0.63 AS T4 B-D2 106-109 26-29 7.55 -58 79.2 2.75 1.49 0.31 

AS T4 B-D2 109-123 29-42.5 7.36 -88 68.3 4.58 1.60 0.51 

AS T4 B-D2 123-133 42.5-52.5 7.48 -81 71.6 2.74 1.72 0.49 AS T4 B-D2 133-144 52.5-63.5 7.41 -69 59.9 5.54 1.57 0.63 AS T4 B-D2 144-156 63.5-76 7.5 -82 50.9 5.26 1.41 0.69 

AS T4 B-D3 156-183 16-43 7.64 -107 49.9 4.17 1.43 0.71 

AS T4 B-D3 183-196 43-56 7.83 -38 74.6 3.52 1.72 0.44 

AS T4 B MEAN 7.55 -88 57.0 4.32 1.49 0.62 

Std. Dev. 0.16 85 12.1 1.37 0.15 0.16 

AS T4 C-D1 0-17 0-17 6.72 178 45.7 9.54 1.32 0.72 AS T4 C-D1 17-40 17-40 7.25 -34 45.6 6.73 1.29 0.70 AS T4 C-D1 40-64 40-64 7.48 -49 46.3 5.43 1.34 0.72 AS T4 C-D2 64-100 14-50 7.54 24 45.1 5.27 1.34 0.73 

AS T4 C-D2 100-131 50-81 7.52 -109 45.2 5.92 1.32 0.73 AS T4 C-D3 131-151 1-21 7.59 -45 46.9 5.53 1.31 0.70 

AS T4 C-D3 151-174 21-44 7.33 -79 53.3 6.05 1.42 0.66 

AS T4 C-D3 174-199 44-68.5 7.18 -72 54.1 5.66 1.45 0.67 

AS T4 C MEAN 7.36 -30 47.6 6.09 1.35 0.70 

Std. Dev. 0.29 116 3.7 1.36 0.06 0.03 

43
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Field: Depth 

interval2

Core: Depth 

Interval3 H Eh

Dry 

weigh LOI

Bulk 

Density Porosity Grain 

Site ID and 

Core Section1

p t

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T5 A-D1 0-12.5 0-12.5 6.46 229 50.1 6.03 1.37 0.69 

AS T5 A-D1 12.5-27.3 12.5-27.3 7.26 134 45.6 6.37 1.33 0.72 

AS T5 A-D2 20-30 0-10 6.5 278 49.3 6.47 1.40 0.71 AS T5 A-D2 30-40 10-20 6.88 88 45.8 7.51 1.34 0.72 

AS T5 A-D2 40-70 20-50 7.49 33 46.1 5.86 1.34 0.72 

AS T5 A-D2 70-101 50-81 7.56 13 45.7 4.55 1.33 0.72 

AS T5 A-D3 85-101 0-20 7.58 29 39.7 5.89 1.28 0.77 

AS T5 A-D3 105-125 20-40 7.89 23 46.7 3.92 1.33 0.71 

AS T5 A-D3 125-157 40-71 7.35 13 48.3 4.96 1.39 0.72 

AS T5 A-D4 145-185 0-40 7.47 -5 51.1 5.25 1.40 0.69 

AS T5 A-D4 185-200 40-55 7.47 8 52.7 5.63 1.43 0.68 AS T5 A-D4 200-228 55-82 7.41 12 46.6 6.08 1.30 0.70 

AS T5 A MEAN 7.38 45 47.5 5.48 1.35 0.71 

Std. Dev. 0.45 59 3.4 0.91 0.04 0.03 

AS T5 B-D1 0-20 0-20 7.42 39 57.0 5.67 1.48 0.64 AS T5 B-D1 20-50 20-50 7.53 12 53.7 6.76 1.43 0.66 

AS T5 B-D1 50-79 50-79 7.36 -13 48.5 6.24 1.36 0.70 AS T5 B-D2 79-94 9-24 7.63 12 49.3 6.58 1.38 0.70 

AS T5 B-D2 94-130 24-60 7.52 4 50.9 6.58 1.42 0.70 AS T5 B-D2 130-166 60-96 7.7 8 47.9 6.45 1.34 0.70 AS T5 B-D3 167-202 17-52 7.69 8 47.7 6.51 1.35 0.71 AS T5 B-D3 202-212 52-62 7.52 11 74.6 4.18 1.66 0.42 

AS T5 B MEAN 7.56 9 51.5 6.32 1.40 0.68 

Std. Dev. 0.12 12 8.7 0.88 0.10 0.10 

AS T5 C-D1 0-15 0-15 6.82 72 48.7 8.65 1.36 0.70 AS T5 C-D1 15-30 15-30 7.33 20 43.6 6.71 1.31 0.74 

AS T5 C-D1 30-49 30-49 7.46 39 40.6 6.53 1.26 0.75 

AS T5 C-D2 50-81 0-31 7.35 5 40.4 7.22 1.23 0.73 AS T5 C-D2 81-112 31-62 7.41 29 42.5 5.98 1.24 0.71 

44
45

Field: Depth 

interval2

Core: Depth 

Interval3

Site ID and 

Core Section1 pH Eh

Dry 

weight LOI

Bulk 

Density Porosity Grain 

(cm) (cm) (mV) (%) (%) (g/cm3) (ml/cm3) (% < 63 

AS T5 C-D2" 112-130 40-58 7.51 192 43.1 5.24 1.27 0.72 

AS T5 C-D3 130-150 10-30 7.51 191 38.8 7.70 1.26 0.77 

AS T5 C-D3 150-175 30-55 7.59 26 46.0 6.38 1.31 0.71 

AS T5 C-D3 175-198 55-78 7.46 31 48.8 7.35 1.37 0.70 

AS T5 C MEAN 7.40 60 43.4 6.81 1.28 0.73 

Std. Dev. 0.23 65 3.6 0.99 0.05 0.03 

ALL DATA MEAN 7.46 -28 47.6 5.7 1.4 0.71 

ALL DATA STD. DEV. 0.23 148 7.8 1.3 0.1 0.08 ALL DATA STD. ERROR 0.02 12 0.7 0.1 0.0 0.01 ALL DATA MEDIAN 7.48 -36 46.0 5.7 1.3 0.72 

ALL DATA MINIMUM 6.46 -162 38.8 1.4 1.2 0.31 ALL DATA MAXIMUM 7.89 278 80.3 9.5 1.9 0.77 ALL DATA TOTAL N 140 140 140 140 140 140 

1 Core coding: AS T# [A, B or C]-D#; where AS = Alviso Slough; T# = Transect number (1 thru 5); [A, B or C] = Site descript

marsh, right marsh or slough channel, respectively); D# = depth specific core segment 

2 Field depth interval measured from the sediment / water interface 3 Core depth interval measured from the top of the individual core liner 
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Table 4. PWA Transects and Predicted Changes in Slough Cross Sectional Area 

Data for current channel cross sectional areas and predicted cross sectional areas for the 20-foot (20’) and 40-foot (40’) levee notch 

scenarios proposed for Pond A8, as reported by Philip Williams and Associates (PWA)1

, have been converted from feet to meters. 

[XS, cross sectional; m2

, meters squared; ND, not determined] 

Current 

Channel 

XS Area 

20’ Notch 

Channel XS 

Area

40’ Notch 

Channel XS 

Area

20’Notch XS 

Area CHANGE

40' Notch XS 

Transect Area CHANGE 1

(m2

) (m2) (m2) (m2) (m2) 

I. A8 Notch 112.4 162.9 204.9 50.5 92.5 

II. d/s Marina 100.9 143.9 179.8 43.0 79.0 

III. A8 Bulge 126.9 154.0 178.7 27.1 51.8 

IV. Mid-Slough 177.0 188.9 200.7 12.0 23.7 

V. Mouth2 N.D. N.D. N.D. 0.0 0.0 

1 EDAW and others, 2007 

2 Model assumption is that there is no cross sectional area change for the Mouth transect 

Table 5. Sediment Mobilization Predictions by Slough Segment 

Slough channel length and slough segment areas, as measured from digital aerial photographs. The change in channel cross sectional 

(XS) area for each segment was based on the average of the two transect lines in Table 4 that bound that defined slough segment. 

Sediment mobilized for the 20-foot (20’) and 40-foot (40’) Pond A8 notch scenarios were calculated as the product of the XS area 

change and the slough channel length for each segment. Propagated error for all calculations are given in parentheses ( ). [m,

meters; m2

, meters squared; m3, meters cubed] 

Alviso 

Slough 

Segment 

Slough 

Channel 

Length 

Segment 

Area 

20' Notch 

Channel XS Area 

CHANGE

40' Notch Channel 

XS Area CHANGE

20' Notch Sediment 

mobilized 

40' Notch Sediment 

mobilized 

(m) (m2

) (m2) (m2) (m3) (m3)

A 777 155,772 46.8 (3.8) 85.7 (6.8) 36,342 (2923) 66,621 (5269) 

B 1020 166,342 35.1 (7.9) 65.4 (13.6) 35,769 (8101) 66,705 (13834) 

C 1134 279,833 19.6 (7.6) 37.8 (14.1) 22,174 (8585) 42,821 (15959) 

D 3419 794,437 6.0 (6.0) 11.8 (11.8) 20,485 (20485) 40,495 (40495)

TOTAL 6350 1,396,384 114,771 (23,823) 216,642 (45,974) 

46
Tables 

Table 6. Mercury Species Current Inventory and Mobilization Predictions by Slough Segment 

Propagated error for all calculations is given in parentheses ( ). [THg, total mercury; MeHg, methylmercury; Hg(II)R, reactive 

mercury; g/m2

, grams per meter squared; g/m3, grams per meter cubed; kg, kilograms] 

A. Total Mercury 

Sediment 

Core Data 

Used 

0-200 cm Depth 

Integrated THg 

CURRENT 

INVENTORY 0-200 

cm Depth 

Integrated THg 

Average Sediment 

HgT Concentration 

by volume 

20' Notch THg 

mobilized 

40' Notch THg 

mobilized

Slough 

Segment 

(g/m2

) (kg) (g/m3) (kg) (kg)

A T1 1.07 (0.19) 166 (30) 0.54 (0.04) 19.6 (2.1) 36.0 (3.7) 

B T1 1.07 (0.19) 177 (32) 0.54 (0.04) 19.3 (4.6) 36.0 (7.9) 

C T2 & T3 1.21 (0.30) 339 (83) 0.62 (0.05) 13.7 (5.4) 26.4 (10.0) 

D T4 & T5 1.22 (0.37) 969 (292) 0.65 (0.06) 13.3 (13.3) 26.2 (26.3) 

TOTAL 1651 (307) 65.9 (15.2) 124.6 (29.5) 

B. Reactive Inorganic Mercury 

Sediment 

Core Data 

Used 

0-200 cm Depth 

Integrated Hg(II)R

CURRENT 

INVENTORY 0-200 

cm Depth 

Integrated Hg(II)R

Average Sediment 

Hg(II)R

Concentration by 

volume 

20' Notch Hg(II)R

mobilized 

40' Notch Hg(II)R

mobilized

Slough 

Segment 

(mg/m2

) (kg) (mg/m3) (kg) (kg)

A T1 0.80 (0.68) 0.13 (0.11) 0.43 (0.24) 0.016 (0.009) 0.029 (0.016) 

B T1 0.80 (0.68) 0.13 (0.11) 0.43 (0.24) 0.015 (0.009) 0.029 (0.017) 

C T3 0.81 (0.26) 0.23 (0.07) 0.60 (0.27) 0.013 (0.008) 0.026 (0.015) 

D T5 0.58 (0.44) 0.46 (0.35) 0.49 (0.25) 0.010 (0.011) 0.020 (0.022) 

TOTAL 0.94 (0.39) 0.054 0.019 0.102 0.036 

C. Methylmercury 

Sediment 

Core Data 

Used 

0-200 cm Depth 

Integrated MeHg 

CURRENT 

INVENTORY 0-200 

cm Depth 

Integrated MeHg

Average Sediment 

MeHg 

Concentration by 

volume 

20' Notch MeHg 

mobilized 

40' Notch MeHg 

mobilized

Slough 

Segment 

(mg/m2

) (kg) (mg/m3) (kg) (kg)

A T1 1.49 (0.36) 0.23 (0.06) 0.72 (0.12) 0.026 (0.005) 0.048 (0.009) 

B T1 1.49 (0.36) 0.25 (0.06) 0.72 (0.12) 0.026 (0.007) 0.048 (0.013) 

C T3 1.09 (0.30) 0.31 (0.08) 0.57 (0.09) 0.013 (0.005) 0.025 (0.010) 

D T5 0.99 (0.18) 0.79 (0.14) 0.53 (0.12) 0.011 (0.011) 0.022 (0.022) 

TOTAL 1.57 (0.18) 0.076 (0.015) 0.142 (0.029) 

47
Legacy Mercury in Alviso Slough, South San Francisco Bay, California: Concentration, Speciation and Mobility 

Appendix A—Sediment core descriptions, Alviso Slough, 

September 2006 

Each page describes a single sediment core section, with the following information 

depicted (from left to right): whole core section photograph, dominant lithology, accessories, 

magnetic susceptibility and sediment density profiles. Refer to the Symbol Legend on page 49 for 

keys to lithology and accessories. The vertical length of the sediment depth interval that 

encompasses a noted accessory is depicted by the thin vertical black line immediately to the left 

of the accessory symbol. The approximate percentage of the depth interval occupied by that 

accessory is given in parentheses ( ) immediately below the accessory symbol. Both magnetic 

susceptibility and sediment density profiles were obtained from whole core scans using the 

multi-sensor core logger. The specific core identification code is given in the upper left corner 

of each page according to the format: T# [A, B or C] D#; where T# = Transect number (1 thru 

5); [A, B or C] = Site description as per Table 1 (left marsh, right marsh or slough channel, 

respectively); D# = depth specific core segment. The specific core depth interval, measured in 

centimeters below the sediment/water interface is given in parentheses ( ) immediately 

following the core identification code. The sediment depth scale depicted on the photograph 

(black ruler) and the Y-axis associated with the plots of magnetic susceptibility and sediment 

density are precisely aligned.1

 

 

1

 This paragraph serves as the alternative text for all of the graphics in this appendix as the description for each is 

identical. 

48
Clay

Clayey Silt

Clayey Sand

Silty Clay

Silty Clay with Sand

Silty Clay Sand

Sand

Sandy Silt

ooo

υυυ

Fe

Wd

Mottles, oxidized

Mottles, reduced

Plant remains, undifferentiated

Rootlets

Iron Stain, ferruginous

Shell fragments

Molluscs, undifferentiated

Wood fragments

οοο Pebbles/Granules

SYMBOL LEGEND

Lithology Accessories

Sandy Silt Clay

49
(30-50%)

T1A D1 (0-46 cm)

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

Fe

(<5%)

(> 50%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

(10-30%)

ooo

(<5%)

(10-30%)

ooo

ooo

ooo

Sediment depth (cm)

50
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

ooo

(< 5%)

(10-30%)

Wd

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

51
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

52
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

ooo

(5-10%)

(5-10%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

53
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

54
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

υυυ (< 5%)

ooo

(< 5%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

55
(> 50%)

(5-10%)

()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

ooo

(< 5%)

ooo

(5-10%)

ooo

(10-30%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

56
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(5-10%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

57
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

No accessories

observed

58
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(30-50%)

ooo

(10-30%)

(< 5%)

(> 50%)

(30-50%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

59
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(5-10%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

60
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(> 50%)

ooo

(< 5%)

ooo

(5-10%)

(< 5%)

(< 5%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

61
()

0 0.5 1 1.5 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50

ooo

(10-30%)

ooo

(30-50%)

(10-30%)

υυυ

(10-30 %)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

62
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(10-30%)

ooo

(5-10%)

( < 5%)

( < 5%)

( < 5%)

( < 5%)

οοο

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

63
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

64
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(> 50%)

(10-30%)

ooo

(30-50%)

(5-10%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

65
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(5-10%)

(10-30%)

Fe

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

66
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(10-30%)

Fe

(5-10%)

ooo

(< 5%)

ooo

(10-30%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

(10-30%)

(10-30%)

67
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(10-30%)

ooo

(5-10%)

ooo

(30-50%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

68
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

υυυ

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

69
Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(5-10%)

ooo

(10-30%)

Sediment depth (cm)

(5-10%)

(5-10%)

70
Sediment Gamma Density 

(g/cm3)

Magnetic Susceptibility 

(cm/g/s) x 10-6

()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(5-10%) (> 5%)

Sediment depth (cm)

71
Magnetic Susceptibility 

(cm/g/s) x 10-6

()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%)

(> 5%)

(10-30%)

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

72
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

73
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

υυυ

(10-30%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

74
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

υυυ

(5-10%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

75
()

0 0.5 1 1.5 

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50

ooo

(< 5%)

(> 50%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

76
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(30-50%)

ooo

(< 5%) (5-10%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

77
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(30-50%)

(> 50%)

(30-50%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

78
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(10-30 %)

(10-30%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

79
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

ooo

(5-10%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

80
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%)

ooo

(< 5%)

ooo

(5-10%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

81
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(< 5%) (< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

82
()

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 0 0.5 1 1.5 2 

υυυ

(10-30%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

83
()

0

10

20

30

40

50

60

70

80

90

100

0 10 2

0

30 40 50 0 0.5 1 1.5 

υυυ

(< 5%)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

84
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

85
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

(5-10%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

86
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

87
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

ooo

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

88
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(5-10%)

ooo

(5-10 %)

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

89
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

(5-10%)

υυυ

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

90
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

υυυ

(< 5%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

91
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

No accessories

observed

92
Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

ooo

(5-10%)

Sediment depth (cm)

93
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

No accessories

observed

94
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(30-50%)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

Sediment depth (cm)

95
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

(5-10%)

Sediment depth (cm)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

96
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

Sediment depth (cm)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

97
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(5-10%)

(< 5%)

(5-10%)

(< 5%)

(10-30%)

(< 5%)

Sediment depth (cm)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

98
()

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 0 0.5 1 1.5 

(< 5%)

(< 5%)

ooo

(5-10%)

Sediment depth (cm)

Magnetic Susceptibility 

(cm/g/s) x 10-6

Sediment Gamma Density 

(g/cm3)

99