## Atmospheric Deposition and Biogeochemistry of Mercury and other Trace Contaminants in Aquatic Ecosystems
Final Project Report Part II: 

# Mercury Studies 2002-2004

Prepared for:



### Nate Gulden FCPC Tribal EPA Forest County Potawatomi Community Crandon, WI 54520

Prepared by



### K. A. Morrison and C. J. Watras Wisconsin Department of Natural Resources UW Trout Lake Station Boulder Junction, WI 54512

June 2006

## Table of Contents 1. Executive Summary........................................................................................................ 1 2. List of Tables .................................................................................................................. 6 3. Methods ........................................................................................................................... 7 3.a. Site Description ........................................................................................................ 7 3.b. Sampling and Analysis ............................................................................................ 8 3.b.1. Stream Sampling............................................................................................... 8 3.b.2. Lake Sampling .................................................................................................. 9 3.b.3. Precipitation Sampling .................................................................................... 10 3.b.4. Air Sampling ................................................................................................... 12 3.b.5. Aqueous Mercury Analysis ............................................................................. 12 3.b.6. Ancillary Solutes ............................................................................................. 13 3.b.7. QAQC Criteria for Mercury Analyses ............................................................ 14 3.b.8. Other analyses ................................................................................................. 15 3.c. Mass Balance Calculations .................................................................................... 16 4. References ..................................................................................................................... 20 5. Published works ............................................................................................................ 22 5a. Eckley C., Watras C.J., Hintelmann H ., Morrison K., Kent A., Regnell O. 2005. Mercury methylation in the hypolimnetic waters of lakes with and without connection to wetlands in northern Wisconsin. Can. J. Fish. Aquat. Sci. 62 : 400- 411. 5b. Watras C.J., Morrison K.A., Kent A., Pr ice N., Regnell O., Eckley C., Hintelmann H., Hubacher T. 2005. Sources of methylme rcury to a wetland-dom inated lake in northern Wisconsin. Environ. Sci. Tech. 39 (13): 4747-4758. 5c. Watras C.J., Morrison K.A., Regnell O., Kratz T.K. 2006. The methylmercury cycle in Little Rock Lake during expe rimental acidification and recovery. Limnol. Oceanogr. 51 (1): 257-270. 5d.i. Kent, A.D., C. J. Wa tras, C. Eckley, O. Regne ll, K. D. McMahon and H. Hintelmann. 2005. Microbial community comp osition and mercury methylation in the anoxic hypolimnia of stratified Wi sconsin lakes. ASLO Annual Summer Meeting, June 19-24, 2005, Santiago de Compostela, Spain 5d.ii. Kent, A.D., C. J. Watras, C. Ec kley, O. Regnell, K. D. McMahon and H. Hintelmann. 2005 Mercury Methylation Varies with Pelagic Microbial Community Composition in Lakes Within the Great Lakes Basin. International Association for Great Lakes Research: 48 th Annual Meeting, Ann Arbor MI, May 23-27, 2005. 5d.iii. Kent, A.D. C.J. Watras, O. Regne ll, C. Eckley and H. Hintelmann. 2005. Analysis of microbial community structur e associated with mercury methylation in northern Wisconsin lakes. Am. Soc. Limnol Oceanogr. Aquatic Sciences Meeting, Salt Lake City, February, 2005 6. Appendices A1. DL Stream Data A2. DL Lake Data A3. Precipitation Data A4. Total Gaseous Mercury Data

## 1. Executive Summary.

In 2001, the Forest County Potawatomi Community (FCPC) and the Wisconsin Department of Natural Resources (WDNR) initiated a cooperative research project entitled “Atmospheric Deposition and Biogeoc hemistry of Mercury and other Trace Contaminants in Aquatic Ecosystems.” This project involved inte nsive studies of the mercury cycle in Devils Lake and other ne arby lakes in northern Wisconsin. The broad research objective was to document similari ties and differences between hydrologically different lakes in the region, fo cusing primarily on the source s and fates of total mercury (Hg T ) and methylmercury (meHg - the chemical fo rm of mercury that accumulates in fish and poses a health risk to huma ns and piscivorous wildlife).

When the planning stage of this proj ect began in 1995, research on mercury contamination in lakes of Wisconsin, Canada and Sweden suggested that the mercury cycles in seepage lakes and drainage lakes might be sign ificantly differe nt (Rudd, 1995).
Within the scientific communit y, it was thought that this diffe rence could help to explain why fish in some lakes were more contaminated than fish in others. At that time, research by the WDNR had focused on the seepage lakes, as exemplified by the well-studied Little Rock Lake (LRL) in Vilas County. Studies of mercury in LRL began in 1984 as part of an EPA-sponsored acid rain project and they continue today (Frost et al. , 1999; Watras et al. , 2006). Results of the LRL work indicate th at the major source of Hg is direct atmospheric deposition to the lake surface, and the major source of meHg is in-lake production in anoxic regions of the water column and sediments. In contrast, studies of drainage systems in Canada and Sweden s uggested that the major sources of Hg and meHg in drainage lakes might be the terres trial watershed – especially areas of the watershed containing wetlands.

In June, 1995 the Director of Natural Re sources for the FCPC, Ms Christine Hansen, requested technical assistance on a research pr oject involving mercury studies for Devils
Lake on the reservation. Since Devils Lake is a drainage lake, closely coupled to a large wetland, it was jointly felt that this project could potentially enhance our understanding

1of the mercury cycle in many lakes and, thereby, benefit all parties involved. A cooperative agreement was formally implem ented in February, 2001 and preliminary research on the lake by WDNR began that summer. For each of the next three years, comprehensive studies on the hydrology and biogeochemistry of the Devils Lake watershed were conducted jo intly by WDNR and FCPC sta ff, along with associated scientists and engineers.

Preparation of the Final Project Report began in 2005, under a contract extension agreement signed by the Tribe on 14 September. Pursuant to that agreement, the WDNR submitted Part I of the Final Report in December 2005, summarizing the hydrologic
studies conducted in the DL watershed. This present report constitutes Part II of the Final Project Report to the Tribe. Part II summar izes the mercury studies, and it has two main objectives. The first objective is to su mmarize the findings of biogeochemical investigations conducted in the Devils Lake watershed during 2002, 2003 and 2004 and to compare them to findings for other lakes. The second objective is to compile and tabulate the large amount of mercury data that were collected so that they will be useful
to the Tribe in future studies.

Devils Lake is a small (11.7 ha), dystrophic drainage lake in Forest County, Wisconsin (45 o 33 ’ N, 88o 50 ’ W) that supports a warm water fish ery of perch and bass. The lake is situated in a relatively pristine, forested watershed and it is fed by a small tributary stream that flows seasonally from spring to fall. The tributary stream emanates from a headwater wetland, which accounts for the dystrophi c status of the lake (dark, tea-stained water). The lake is drained by a single dist ributary stream and by seepage to groundwater.

Intensive hydrological investiga tions of the Devils Lake catchment were conducted in conjunction with the mercury study. These investigations invol ved measuring or estimating the sources of water to the lake (precipitation, tributary stream flow, nonchannelized runoff and groundwater discha rge), losses of water from the lake (distributary stream flow, gr oundwater recharge and evaporation) and the change in the volume of water in the lake (change in wa ter storage) over time. The hydrologic data

2were used to construct water budgets for th e lake during each year of study. In this second part of the Final Report, the hydrologic data are coup led with chemical data to construct budgets for mercury in the lake . Based on these budgets, the importance of
various sources and sinks in the watershed can be assessed.

Annual budgets for total Hg (Hg T ) and seasonal budgets for me Hg are shown on Table 1
and Table 2 for each of the three studies years. Annual budgets were computed for calendar years, January 1 – December 31. The seasonal budgets were computed for the time period when meHg accumulates in the wate r column of the lake, generally from the beginning of spring melt to late summer strati fication (e.g. April to late August). The annual budgets are useful in assessing the major sources and sinks for waterborne Hg T, while the seasonal budgets are needed to identify the major sources of meHg – the chemical form that accumulates in fish. MeHg is produced in anoxic regions of the lake and in anoxic wetland porewaters. A major goal of this research project was to quantify the relative importance of these two sources.

Table 1 . Annual Budgets for waterb orne total mercury (Hg T ) in Devils Lake, 2002 – 04

-------------Inputs-------------- ----------------------Outputs---------------- Change in Storage

( Δ S)

Year Precip (P) Surface Runoff

(RO) Stream Flow (Q in ) Sedimentation & Evasion (S+E) Stream Flow (Q out ) Lake Seepage

(GO) 2002 1.50 0.19 3.27 3.62 0.91 0.11 0.33 2003 1.01 0.05 0.91 1.85 0.62 0.04 -0.52 2004 0.99 0.07 1.18 1.47 0.53 0.06 0.18

mean 1.17 0.11 1.79 2.31 0.69 0.07 0.00

SD 0.29 0.08 1.29 1.15 0.20 0.04 0.46

3Table 2 . Seasonal Budgets for waterborne methylmercury (meHg) in Devils Lake, 2002- 04

Year Precip (P) Surface Runoff

(RO) Stream Flow (Q in ) Net methyl.

(M) Sedimentation (S) Stream Flow (Q out ) Lake Seepage

(GO) Change in Storage

( Δ S) 2002 0.012 0.002 0.056 0.408 0.026 0.066 0.004 0.382 2003 0.007 0.001 0.027 0.132 0.009 0.078 0.002 0.078 2004 0.007 0.001 0.023 0.081 0.012 0.048 0.002 0.049

mean 0.009 0.001 0.035 0.207 0.016 0.064 0.003 0.170

SD 0.003 0.000 0.018 0.176 0.009 0.015 0.001 0.184

The mass balances for Hg T indicate that the tributary str eam was an important external source to the lake, contribu ting 50% to 70% of the Hg T that entered the lake each year. Hg T in the tributary stream-water is ultimately attributable to atmospheric Hg deposition onto the watershed as a whole. Given the size of the tributary catchment and the rate of atmospheric Hg deposition, it is clear the te rrestrial watershed is a net sink for Hg T . In other words, most of the atmospherically-deposited Hg T is either sequestered in soils or evades back into the atmosphere, and only a small fraction bleeds out into stream-water
and enters the lake.

The mass balances for meHg indicate that the tributary stream contri butes more meHg to the lake than does direct precipitation. As suc h, the tributary stream constitutes the largest external source of meHg to the lake. However, in contrast to Hg T , internal sources of meHg are larger than external sources in each year. In other words, more meHg is produced within the lake itself than is derived from the watershed and the airshed combined. Parallel investigations indicate 1) that meHg production rates in Devils Lake are greater than those in Wisc onsin lakes that are not connect ed to wetland; and 2) that the meHg is produced by bacteria that inha bit the anoxic hypolimnion of the lake during

summer.

In a comparative study of mercury methyla tion in the dark-water, wetland-dominated Devils Lake and the clear-water, precipita tion-dominated Pallette Lake in neighboring Vilas County, Eckley et al . (2005) showed that methylation rates in Devils lake were up

4to two-fold greater than those in Pallette Lake – potentially accounting for the higher concentrations of waterborne meHg in Devils Lake. In both lakes, in-lake methylation was sufficient to account for all the meHg that accumulated during summer.

In a companion study, Kent et al (2005a, b, c) showed that si milar microbial communities were associated with meHg production in thre e regional lakes (Devils Lake, Pallette Lake and Little Rock Lake). This finding suggests that environmental fact ors which affect the activity of the resident microbial communities may partly explain the differences in meHg production observed among these lakes. In Devils Lake, the influx of runoff from the headwater wetland may supply nutrient su pplements and additional Hg substrate – both of which could result in higher rate s of meHg production in this lake.

In conclusion, investigations of the aquatic mercury cycle in Devils Lake indicate that wetland runoff may have both dire ct and indirect effects that increase the potential for mercury methylation relative to lakes without hydrological connectio n to wetland. These effects may interact synergisti cally – producing a larger effect together than either would have separately ( sensu Watras et al. , 2006). Since meHg is the chemical form of mercury that accumulates in fish and poses the majo r risk to humans and piscivorous wildlife, these findings are directly relevant to the poten tial for fish contamination in Devils Lake.

5

## 2. List of Tables

Table 1 . Annual Budgets for waterb orne total mercury (Hg T ) in Devils Lake, 2002 – 04...................................................................3

Table 2 . Seasonal Budgets for waterbor ne methylmercury (meHg) in Devils Lake, 2002-04..................................................................4

Table 3. Comparison of atmospheric merc ury data collected at DL study site with other sites in regi on over 117 weeks of parallel
collection...................................................................................11

Table 4. Annual and seasonal VWA Hg T concentrations (ng/L) in precipitation from three NADP/ MDN sites (WI36, WI32 and WI10) in the Devils Lake region...................................................12

Table 5. Annual Hydrologic Budgets for Devils Lake, 2002-2004..........................18

Table 6. Seasonal Hydrologic Budgets for Devils Lake, 2002-2004.........................18

Table 7. Hg T concentrations (ng/L) used to construct annual budgets for waterborne Hg T in Devils Lake, 2002 – 2004.........................19

Table 8. MeHg concentrations (ng/L) used to construct seasonal budgets for waterborne meHg in Devils Lake, 2002 – 2004......................19

6

## 3. Methods 3.a. Site Description

Devil’s Lake (N 45 o 32.954 ’ , W 88 o 50.040 ’ ) is a dark-water drainage lake in Forest County, Wisconsin, with a surface ar ea of 11.7 h, a volume of 3.5 × 10 5 m 3 , a maximum depth of 7.6 m, a mean depth of 3.0 m and a water residence time of roughly 1 year. The terrestrial watershed comprises a headwater wetland approximately twice the size of the lake encircled by gently sloping, forested uplands that surround the headwater wetland
and the lake itself. A small stream emanates from the headwater wetland and it flows directly to the northeast end of the lake th rough a narrow valley. Water leaves the lakevia a small out-flowing stream to the southwest. A small wetland fringes the downgradient end of the lake at the mouth of the outlet. A narrow, unimproved, gravel road circumscribes the remaining lake shore, r oughly defining a near-s hore watershed of 12.3 ha. Further details on the hydrologic setti ng can be found in Horsley and Witten (2003).

The lake and its forested watershed are situated in thick, unconsolidated glacial till (Simpkins, McCartney and Mi ckelson, 1987). Groundwater flow directions within the unconfined glacial deposits of the region often follow the land-surface topography, moving from upland to lowland areas and disc harging in some lakes, streams, and land depressions. Saturated thickness of the aqui fer ranges from 18 m to 49 m in general (Lidwin and Krohelski, 1993). The moderate to low permeability of the glacial tillderived soils that comprise the Devil’s Lake surface watershed contributes to a “perched” hydrologic system where surface water eleva tions sit well above the local groundwater table. The perched nature of the entire Devil’s Lake hydrologic system has been demonstrated by surface water levels signi ficantly higher than groundwater levels throughout the system and by a consistent loss of flow volume from upstream to
downstream locations in the inlet stream (Horsley & Witten, 2003). This hydrologic setting simplifies construction of water budgets and mercury mass balances since groundwater inputs may be considered negligible.

7

### 3.b. Sampling and Analysis 3.b.1. Stream Sampling

Surface water monitoring was conducted from 1996 through 2001 to roughly characterize the spatial and temporal variability of solu tes within the watershed. Stream monitoring was performed routinely at three locations: the Upstream and Inlet sites on the tributary stream and the Outlet (Roadside) site on the distributary stream.

Intensive monitoring of the chemistry and discharge volumes of the tributary and distributary streams was in itiated in 2002 and continue d through 2004. Stream water samples for chemical analysis were collected weekly beginning at the onset of melt each year. Sampling and analytical protocols were similar to those used during the background monitoring years. Grab samples were obtaine d at the inlet and outlet sampling sites on the same day that manual hydrologic flow measurements were made (DL Hydrology Report). The stream water samples were shippe d on ice in dark coolers. Mercury samples were hermetically sealed in double plastic bags.

At regular intervals (generally each week), stage was determined visually by reading the
level of the water surface at each monitori ng site on a staff gauge. Concurrently, discharge was estimated using mini (pygmy) Pr ice “AA” flow meters with top-set wading rods. Flow measurement began at the onset of spring melt and contin ued until the stream stopped flowing in fall. This information was used to compute the stage-discharge rating curves for each site (DL Hydrology Report).

Stream stage was also reco rded continuously at 15-mi nute intervals using barocompensated, data-logging pressu re transducers during the unf rozen portion of the year (early April through November). The logger da ta were converted to discharge units by applying the rating curves described above. The resultant 15-minute estimates of water discharge were integrated over appropriate time intervals to calculate daily, weekly and annual flow volumes (DL Hydrology Report).

8

### 3.b.2. Lake Sampling

Lake sampling was conducted at a single mid-la ke station, in part because background monitoring had indicated no si gnificant differences between sites L1 and L2 during the period 1996-2001. To obtain vertical concentration profiles, sampling depths were selected after establishing the physical structure of the wate r column using a SeaBird-19 plus CTD. Prior to profiling, the non-metallic sampling boat was tethered fore and aft to buoys that were permanently an chored to mark the northerly and southerly bounds of the 7 m depth contour. The tether ing line thus spanned the lake surface overlying the hypolimnion. The CTD was lowered through the wate r column at a descen t rate of 1 to 2

cm s -1 at a station located about 3 to 5 m fr om the southernmost buoy. Data from the sensors were logged at a rate of 4 Hz and graphically displa yed in real-time with an onboard laptop computer. In addition to conductivity, temperature and depth, the Seabird
unit also measured in situ chlorophyll fluorescence, tr ansmissometer beam attenuation, pH and dissolved oxygen so that thermal stru cture, redox conditions and particle layers could all be used to target the collection of water sample s during the second deployment. After obtaining a first Seabird profile, the boat was moved along the tether line toward the northernmost buoy to a second station and anacrylic outrigger was attached to the SeaBird profiler. A submersible, non-metallic pump was fixed to the end of the outrigger so that water could be pumped to the surface through acid-washed C-Flex tubing and collected on deck as described by Watras et al. (1998). The collection of water samples began when the unit reached the first target depth. Generally 5 to 7 depths were sampled in the 7 m water column. On every samp ling date, the two SeaBird profiles were compared to ensure that the physical, chem ical and biological structure of the water column was horizontally uniform across the deep pelagic region of the lake. The single sampling profile was then considered representative of the entire water column. The lake water samples were hermetically sealed in double plastic bags and transported on ice in
dark coolers to the UW Tr out Lake Clean Laboratory.

9

### 3.b.3. Precipitation Sampling

Bulk precipitation was sampled continuously and collected weekly from 2002 through 2004 using modified IVL-type coll ectors (as described by Morrison et al. 1995) at two
sites. One site was the US NADP/MDN site WI 36 located at Trout Lake in neighboring Vilas County (roughly 80 km from Devils La ke) where the deposition of mercury has been monitored continuously since 1995, alo ng with total precipitation amount and ancillary precipitation chemistry ( http://nadp.sws.uiuc.edu/mdn ). A second site was
established on the Potawatomi Reservation le ss than 2 km from Devils Lake. The IVL sampler at this site was maintained by FC PC personnel and operated continuously from May 28, 2002 to August 25, 2004. D uplicate IVL-collectors were operated from May 28, 2002 to September 4, 2002. All IVL samples were stored in the dark and transported to the Trout Lake Clean Laboratory for Hg T analysis. The mercury data for the IVL samples
collected at the FCPC and Trout Lake air monitoring sites (2002-2004) are presented in Appendix A3

.

A continuous record of precipitation was not available for the FCPC site for the entire study period. For the purposes of this study, we assumed that mercury concentrations in precipitation were regionally coherent whereas precipita tion amount could demonstrate significant local variability. Therefore, we estimated precipitation amount using data from the site with a complete record located nearest to the study site and we estimated Hg T concentrations in precipitation from regional means.

The nearest site to the Devils Lake study site with a comp lete record of precipitation amount for the entire study period was th e Laona 6 SW weathe r station (ID# 474582; Wisconsin State Climatology Office, http://www.aos.wisc.edu/~sco/ ) approximately 13
km due west of DL. Data from this site wa s used to estimate preci pitation amounts for the annual hydrologic budgets reported in the DL Hydrology Report. The use of Laona 6 SW data was validated by comparison with the data collected weekly from the FCPC site for the period May 2002 through August 2004. The sim ilarity of the two records indicated

10that the Laona site is a reasonable surr ogate for FCPC precip itation (DL Hydrology Report).

Table 3. Comparison of atmospheric me rcury data collected at DL study site with other sites in region over 117 weeks of parallel collection

FCPC IVL TRL IVL WI36 MDN WI09 MDN WI32 MDN

Hg T deposition (μg/m 2 ) 19.9 17.5 19.5 16.6 19.5 VWA Hg T (ng/L) 10.7 9.7 10.9 10.5 12.2
# weeks missing precip data 0 0 0 0 7 # weeks w/o Hg data 0 7 15 23 11 Precip (cm) w/o Hg data 0 0.03 4.2 5.1 5.0

Annual and seasonal Hg T concentrations at the DL study site were estimated as the mean of the volume-weighted average (VWA) Hg T concentrations from three US NADP/MDN sites. These sites were i) th e Trout Lake site (WI36) desc ribed above, ii) the Popple River site in Fence, Florence County, WI 50 km northeast of DL (WI32) and the Middle Village site in Shawano County, WI 75 km south of DL (WI09) ( http://nadp.sws.uiuc.edu ). Comparison between the IVL collector at Devils Lake and the
mean of the three MDN sites showed that the VWA concentration of Hg T differed by roughly 5% during the 117 weeks of para llel sampling in 2002-2004 (10.7 ng/L vs. 11.2 ng/L, respectively), indicating locally cohere nt Hg depositional regimes (Table 3). The
annual and seasonal mean VWA concentratio ns used to construct the mercury mass balances are shown in Table 4. The mean concentrations were multiplied by the precipitation amounts from Laona 6 SW to estimate Hg T deposition at the study site. The atmospheric deposition of meHg to the surface of Devils Lake was estimated to be 1.2% of the atmospheric Hg T deposition, based on NADP/MDN da ta for the Trout Lake site (WI36). During 2002, 2003, and 2004 meHg constituted 0.5%, 1.9% and 1.5%, respectively, of the annual Hg T deposition at this site ( http://nadp.sws.uiuc.edu/mdn ). These data agree well with earlier estimates of 1.5% base d on measurements at nearby Little Rock Lake (Watras et al. 1994, Fitzgerald et al. 1991).

11Table 4. Annual and seasonal VWA Hg T concentrations (ng/L) in precipitation from three NADP/ MDN sites (WI36, WI32 and WI10). Values are mean ± SD

. Year Annual Seasonal

2002 12.1 ± 0.9 14.0 ±0.7
2003 11.2 ± 1.9 12.2 ± 1.8
2004 9.1 ± 0.4 12.4 ± 0.8



### 3.b.4. Air Sampling

A Tekran Model 2537A Mercury Vapor Anal yzer was operated at NADP/MDN site WI36 (Trout Lake) from October 3, 2002 until January20, 2004 taking continuous 5- minute integrated samples. The sampling inle t was connected to a Teflon manifold which
also served ozone and sulfur dioxide analyzers maintained by the WDNR Bureau of Air Management. The manifold was connected by 1⁄2- inch plastic tubing to an inverted funnel atop a tower which extended above treetops. Airflow was maintained by a vacuum pump
and monitored with a flow meter. The Te kran 2537A was equipped with an internal mercury vapor permeation source which was us ed to perform automatic calibrations at regular intervals. Manual injections of satu rated mercury vapor were also occasionally performed.

Daily means of the 5-minute continuous TGM concentrations are complied in Appendix
A4.1 . Hourly means of TGM and all of the original TEK files are in Appendices A4.2
and A4.3 (CD only).



### 3.b.5. Aqueous Mercury Analysis

Samples for mercury analysis collected for background monitoring from 1995 to 2001 were analyzed using purge-trap/CVAFS for Hg T (Bloom & Fitzgerald 1988) and ethylation/GC/CVAFS for me Hg (Bloom 1989, Liang et al. 1994) at Frontier

12Geosciences, Inc. (Seattle, WA). Stream samp les for mercury analysis collected in 2002 were also analyzed by Frontier Geosciences. La ke samples for mercury analysis collected for intensive monitoring from 2002 through 2004 were analyzed at UW Trout Lake Clean Laboratory where they were analyzed following protocols similar to those used at Frontier Geosciences, i.e. EPA Methods 1630 & 1631 (US EPA 2001, 2002). Intercalibration between these two analytical facilities has shown good agreement for both Hg T and meHg analysis in freshwater samples (Bloom et al. 1995). Stream samples
collected in 2003 were also sent to UW Tr out Lake. All UW Trout Lake samples were analyzed in duplicate for Hg T and meHg. In 2004, stream samp les were analyzed at State Laboratory of Hygiene (Madison, WI).

Mercury data for the tributary and distributary streams are in Appendix A1 . Data for
Devils Lake are found in Appendix A2

.



### 3.b.6. Ancillary Solutes

Conductivity and pH were monitored in the field using hand-held meters throughout the study period. Samples for ancillary solutes an alyses collected for background monitoring from 1995 to 2001 and stream samples collecte d in 2002 were sent to ERA Labs, Inc., Duluth, MN. These samples were analyzed for alkalinity, dissolv ed organic carbon (DOC), total Kjeldahl nitrogen (TKN), tota l phosphorus (TP) and chlorophyll-a (Chl-a). Results of these analyses are reported in Appendices A1.1 (stream data) and A2.1 (lake data).

Lake water samples collected during inte nsive monitoring 2002 – 2004 and stream samples collected in 2003 were analyzed for pH, DOC, SO 4 2- , total sulfide, methane, suspended particulate matter (SPM), majo r cations, anions and metals. SPM, chl a , pH,
methane and sulfide determinations were performed at Trout Lake lab by WDNR personnel. DOC determinations were perfor med by UW-Madison personnel at the Center for Limnology. Cations, anions an d metals were sent to the State Laboratory of Hygiene

13(SLH), Madison, WI. Methods are described by Watras et al. (2006) (see Section 5c ). Results are reported in Appendices A1.2 (stream data) and A2.2 (lake data).

All ancillary solute analyses on stream samples collected in 2004 were performed by SLH. Results are in Appendix A1.3

.



### 3.b.7. QAQC Criteria for Mercury Analyses

Quality control and quality assurance criteria for UW-Trout Lake clean laboratory mercury analyses, 1997 – 2005 with DL site sp ecific values where applicable are as follows: 

### Hg T 

### analysis following EPA Method 1631

General Criteria 1. On-going precision (mean ± SD ) 99.7% ± 6.2%, n=735 2. Quality control samples (mean ± SD ) 97.6% ± 5.9%, n=158 3. Bubbler blanks (mean ± SD ) 3.7 pg ± 3.5 pg, n=1628
Aqueous Hg T 1. Reagent blank (mean ± SD ) 15.3 pg ± 6.5 pg, n =228 2. Daily detection limit (3·sd reagent blanks) (mean, range) 0.05 ng/L, 0.01 – 0.18 ng/L 3. Method detection limit (pooled variance of reagen t blanks): 0.05 ng/L 4. Method blanks (mean ± SD ) 16.8 pg ± 4.6 pg, n =28 5. Method detection limit (pooled variance of method blanks): 0.04 ng/L 6. Lab duplicate RPD (mean ± SD ) Lake and stream samples 4.8% ± 4.4%, n=171 DL Lake and stream samples 5.0% ± 4.6%, n=99 Rain samples 10.3% ± 9.7%, n=107 7. Field duplicate RPD (mean ± SD ) Lake and stream samples 4.8% ± 9.1%, n=36 DL Lake and stream samples 7.0% ± 7.2%, n=32 DL “A” and “B” rain samples 15% ± 15%, n=12

8. Matrix spike recovery (mean ± SD ) Lake and stream samples 94.8% ± 6.7%, n=111 DL Lake and stream samples 92.7% ± 7.2%, n=37 Rain samples 103.8% ± 18.4%, n=98 9. Matrix spike duplicate RPD (mean ± SD ) Lake and stream samples 4.3% ± 5.0%, n=52 DL Lake and stream samples 6.6% ± 5.9%, n=22 Rain samples 7.2% ± 10.3%, n=128

14Particulate Hg T 1. Method blanks (mean ± SD ) 22.3 pg ± 9.2 pg, n =44 2. Reagent blanks (mean ± SD ) 18.2 pg ± 4.1 pg, n =24 3. Filter blanks (mean ± SD ) 42 pg ± 32 pg, n =38 4. Yield CRM (DOLT-2) (mean ± SD ) 100.6% ± 7.0%, n =18 5. Duplicate RPD (mean ± SD ) 27% ± 30%, n =128 

### MeHg analysis following EPA Method 1630

General Criteria 1. On-going precision (mean ± SD ) 100.4% ± 10.5%, n=609 2. Quality control samples (mean ± SD ) 105.7% ± 11.5%, n=78

Aqueous meHg 1. Reagent blank (mean ± SD ) 0.4 pg ± 1.1 pg, n =268 2. Method detection limit (pooled variance of reagen t blanks): 0.05 ng/L 3. Distillation blanks (mean ± SD ) 0.3 pg ± 0.8 pg, n =123 4. Method detection limit (pooled variance of dis tillation blanks): 0.03 ng/L 5. Lab duplicate RPD (mean ± SD ) Lake and stream samples 10.9% ± 9.0%, n=195 DL Lake and stream samples 8.4% ± 7.1%, n=88 6. Field duplicate RPD (mean ± SD ) Lake and stream samples 7.8% ± 7.7%, n=36 DL Lake and stream samples 7.9% ± 7.7%, n=29 7. Matrix spike recovery (mean ± SD ) Lake and stream samples 96% ± 11%, n=118 DL Lake and stream samples 93% ± 9%, n=41 8. Matrix spike duplicate RPD (mean ± SD ) Lake and stream samples 5.4% ± 5.7%, n=39 DL Lake and stream samples 5.3% ± 4.9%, n=19
Particulate meHg 9. Reagent blanks (mean ± SD ) 1.1 pg ± 2.4 pg, n =49 10. Filter blanks (mean ± SD ) 1.6 pg ± 2.7 pg, n =69 11. Matrix spike recovery (mean ± SD ) 104.3% ± 0.1% pg, n =5 12. Yield CRM (DOLT-2) (mean ± SD ) 101.1% ± 0.2%, n =14 13. Duplicate RPD (mean ± SD ) 28.2% ± 0.5%, n =92



### 3.b.8. Other analyses

In addition to sampling Devils Lake for mercury species and ancillary chemical analytes, water samples were also collected to characterize the microbial community and

15to estimate methylation and demethylation ra te constants at specifi c depths during peak
stratification in 2002. Microbi al community composition was characterized with molecular genetic techniques (ARISA and clone libraries). Details of methods and results
can be found in Kent et al. (2005a, b, c) in Section 5.d ). Rates of mercury methylation and demethylation were measured using stable isotopes of mercury. Methods described in detail and results presented in Eckley et al. (2005) in Section 5.a

.



### 3.c. Mass Balance Calculations

Annual budgets for waterborne Hg T in Devils Lake were constructed for years 2002 – 2004. Annual budgets were computed for calendar years, January 1 to December 31. A seasonal mass balance for waterborne meHg for the time period when mercury
accumulates in the water column also was compiled for each year. This seasonal period began with the onset of stream flow in spring and continued until peak summer stratification (mid-August). Th e governing expression was:

Δ S Hg = (P Hg + Q in-Hg + RO Hg ) – (Q out-Hg + G out-Hg + E Hg + S Hg ) + M net

where Δ S Hg is the change in waterbor ne mercury mass (storage); P Hg is the mass deposited atmospherically directly on the lake; Q in-Hg is the mass delivered from the upstream wetland via the tributary stream; RO Hg is the mass of mercury in nonchannelized runoff in the nearshore zone; Q out-Hg is the mass lost to the distributary stream; G out-Hg is the mass lost to groundwater; E Hg is the mass lost by evasion across the air/water interface; S Hg is the mass lost to sediments; and M net is the mass of meHg in the
water column attributable to ne t in-lake methylation. For the Hg T budget, M net is zero.

Change in storage ( Δ S Hg ) was estimated as the difference in waterborne mass at the beginning and end of the season or water year. The total mass of mercury in the water
column was determined as the sum of ma sses over all depths sampled, according to
Σ c i ·v i , for i = 1 to n, where c i and v i represent the concentration and volume for a given depth stratum (i). Midpoints between successive sampling depths were used to bound (i);

16and the lake volume was adjusted for cha nges in stage. Atmospheric deposition (P Hg ) was the product of the volume-weighted average mercury concentration times the amount of precipitation falling directly on the lake (Sec 3.b.3 and Table 4). Stream in-flow (Q in-Hg )
was estimated as Σ c t ·v t , for t = 1 to n, where c t and v t represent the mercury concentration and water discharge volume for a given time interval. Stream samp ling dates were used as mid-points between successive time intervals. Non-channelized runoff (RO Hg ) was calculated as the product of the runoff co efficient from the hydrologic budget (0.1), precipitation volume and the volume-weighted concentration of mercury in tributary stream water ( i.e. assuming the same mercury con centration in channelized and nonchannelized overland flow ). Stream out-flow (Q out-Hg ) was estimated as the product of distributary stream discharge vo lume and the mean epilimnetic concentration of lake over the appropriate time period. Groundwater output (G out-Hg ) was the product of groundwater outflow volume times the mean concentration of mercury in the epilimnion (assuming no profundal recharge). Groundwater recharge was seasonally pro-rated from the annual hydrologic budget for the meHg budgets. Evasion and sedimentation were estimated as a pooled residual loss term: (E + S) Hg = (P Hg + Q in-Hg + RO Hg ) – (Q out-Hg + G out-Hg + Δ S Hg ). For meHg, this term was appr oximated as 1% of (E + S) HgT since meHg constitutes roughly 1% of the Hg T in sediments but it does not evade across the air-water interface to a significant degree (Watras et al. 1996, Ullrich et al. 2001, Watras et al. 1998, Hudson et al. 1994). Note that (E + S) MeHg is probably a lower limit since demethylation in the sediment is not considered. Net methylation (M net ) was calculated according to: M net = Δ S MeHg + (Q out-MeHg + G out-MeHg + (E + S) MeHg ) – (P MeHg + RO MeHg + Q in-MeHg ). M net is a
conservative estimate for the mass in the wate r column attributable to in-lake production (regardless whether the site of production is in sediments or the water column) if (E + S) MeHg underestimates the gross flux to sediments. By definition, M net includes demethylation in the water column.

The annual mass balances for waterborne Hg T in Devils Lake, 2002 – 2004, are shown in
Table 1 ; the seasonal mass balances for waterborne, meHg are presented in Table 2 . The annual and seasonal hydrologi c budgets upon which the me rcury budgets are based are

17given in Tables 5 & 6 . The annual Hg T concentrations assigned to hydrologic fluxes are
in Table 7 ; seasonal VWA meHg concentrations are in Table 8

.

Table 5. Annual Hydrologic Budgets for Dev ils Lake, 2002-2004 (from DL Hydrology Report)

-------------Inputs--------- ------------Outputs------------

Year Precip (P) (m 3 ) Surface Runoff

(RO) (m 3 ) Tributary Flow (Q in ) (m 3 ) Evap (E) (m 3 ) Distributary Flow (Q out ) (m 3 ) Lake Seepage

(GO) (m 3 ) Change in Lake Storage

( Δ S) (m 3 )

2002 124,007 16,917 287,331 65,988 318,986 38,474 4,808
2003 90,442 7,589 128,889 65,988 175,704 10,520 -25,293
2004 108,208 7,595 128,990 65,988 163,389 17,167 -1,751

mean 107,552 10,700 181,737 65,988 219,360 22,053 -7,4121

SD 16,792 5,384 91,448 6,243 a 86,498 14,604 15,829

Table 6. Seasonal Hydrologic Budgets for Devils Lake, 2002-2004

-------------Inputs--------- ------------Outputs------------

Year Precip (P) (m 3 ) Surface Runoff

(RO) (m 3 ) Stream Flow (Q in ) (m 3 ) Evap (E) (m 3 ) Stream Flow (Q out ) (m 3 ) Lake Seepage

(GO) (m 3 ) Calc. Change in Lake Storage

( Δ S) (m 3 ) Obs. Change in Lake Storage

( Δ S) (m 3 ) Residu al (m 3 )
2002 71394 7482 231360 39593 231182 13914 25547 25547 42373 2003 48858 5121 128888 39593 175704 4208 -36638 -34811 -1827 2004 47427 4971 128990 39593 163389 6679 -28273 -36633 8360

mean 55893 5858 163079 39593 190092 8267 -13121 -29423 16302

SD 13443 1409 59132 - 36114 5044 33748 10947 23146 P calculated from seasonal Laona 6SWp recipitation amount and lake area RO estimated from seasonal precipitation, run-off coefficient = 0.10, and near-shore area = 12.3 ha Q in estimated as seasonal Inlet discharge (DL Hydrology Report) E 60% annual evaporation Q out estimated as seasonal Outlet discharge (DL Hydrology Report) GO prorated from GO in annual hydrologic budgets Calc.. Δ S calculated by difference Obs. Δ S calculated from staff gauge r eadings and hypsometric curve Residual Calc Δ S – Obs Δ S

18Table 7. Hg T concentrations (ng/L) used to construct annual budgets for waterborne Hg T in Devils Lake, 2002 - 2004

Year Precip (P) Tributary Stream (Q in ) and Surface Runoff

(RO) Distributary Stream (Q out ) and Lake Seepage

(GO) 2002 12.1 11.4 2.9 2003 11.2 7.1 3.5 2004 9.1 9.1 3.2

mean 10.8 9.2 3.2

SD 1.5 2.2 0.3

Table 8. MeHg concentrations (ng/L) used to construct seasonal budgets for waterborne meHg in Devils Lake, 2002 - 2004

Year Precip (P) Tributary Stream (Q in ) and Surface Runoff

(RO) Distributary Stream (Q out ) and Lake Seepage

(GO) 2002 0.17 0.24 0.28 2003 0.15 0.21 0.44 2004 0.15 0.18 0.30

mean 0.15 0.21 0.34

SD 0.01 0.03 0.09

19

## 4. References

Citations of DL Hydrology Report refer to: Atmospheric Deposition and Biogeochemistry of Mercury an d other Trace Contaminants in Aquatic Ecosystems, Final Project Report Part 1: Devils Lake Watershed Hydrology 2002 – 2004, prepared by Morrison KA and Watras CJ, December 2005.

The following references are completely cited in Section 5 . Complete copies of the published papers and abstracts of th e oral presentations are included. Eckley et al. 2005
Watras et al. 2005
Watras et al. 2006
Kent et al. 2005a, b, c

Other works cited:
Frost 1995

Frost T.M., Montz P.K., Kratz T.K., Badillo T., Brezonik P.L., Gonzalez M.J., Rada R.G., Watras C.J., Webster K.E., Wiener J.G., Williamson C.E., Morris D.P. 1999. Multiple stresses from a single agent: diverse responses to the experimental acidification of Little Rock Lake, Wisconsin. Limnol. Oceanogr. 44 (3, part 2): 784- 794. Bloom N.S., Watras C.J. 1989. Observati ons of methylmercury in precipitation. Sci. Tot. Environ. 87/88 : 199-207. Bloom N.S., Fitzgerald W.F. 1988. Determination of vola tile mercury species at the picogram level by low temperature gas chromatography with cold vapor atomic fluorescence detection. Anal. Chim. Acta 208 : 151-161. Bloom N.S., Horvat M., Watras C.J. 1995. Resu lts of the international aqueous mercury speciation intercomparison exercise. Water Air Soil Pollut. 80 : 1257-1268. Fitzgerald W.F., Mason R.P., Vandal G.M. 1991. Atmospheric cycling and air-water exchange of mercury over mid-c ontinental lacustrine regions. Water Air Soil Pollut. 56 : 745-768. Horsley & Witten Inc. 2003. Devil's Lake Summary Report: Water Years 1996 to 2002. Horsley & Witten Inc., 90 Route 6A, Sandwich, MA 02563, 57 p. Hudson R.J.M., Gherini S.A., Watras C. J., Porcella D.B. 1994 Modeling the biogeochemical cycling of mercury in lake s: the Mercury Cyc ling Model (MCM) and its application to the MTL study lakes. In: Watras C.J. and Huckabee J.W., eds. Mercury Pollution: Integration and Synthesis , Lewis Publishers. p. 473-526.

20Liang L., Horvat M., Bloom N.S. 1994. An improved speciation method for mercury by GC/CVAFS after aqueous pha se ethylation and room temperature precollection. Talanta 41 (3): 371-379. Lidwin R.A., Krohelski J.T. 1993. Hydrology and Water Quality of the Forest County Potawatomi Indian Reservation, Wisconsin. USGS, 91-4136. Morrison K.A., Kuhn E.S., Watras C.J. 1995. Co mparison of three methods of estimating atmospheric mercury deposition. Environ. Sci. Tech. 29 (3): 571-576. Rudd J.W.M. 1995. Sources of methylmercur y to aquatic ecosystems: a review. Water Air Soil Pollut. 80 : 697-713. Simpkins W.W., McCartney M. C., Mickelson D.M. 1987. Plei stocene Geology of Forest County, Wisconsin. Wisconsin Geological a nd Natural History Survey, Circular 61. Ullrich S.M., Tanton T.W., Abdrashitova S.A. 2001. Mercury in the aquatic environment: A review of factors affecting methylation. Critical Reviews in Environmental Science and Technology 31 (3): 241-293. US EPA. 2001. Method 1630: Methyl mercury in water by distillation, aqueous ethylation, purge and tra p, and CVAFS (EPA-821-R01- 020). Office of Water, Engineering and Analysis Division, O ffice of Science and Technology, EPA-821- R01-020. Washington, DC US EPA. 2002. Method 1631, Revision E: Merc ury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluores cence Spectrometry (E PA 821-R-02-019). Office of Water, Engineering and Anal ysis Division, Offi ce of Science and Technology, EPA 821-R-02-019. Washington DC. Watras C.J., Bloom N.S., Hudson R.J.M., Gh erini S., Munson R., Claas S.A., Morrison K.A., Hurley J., Wiener J.G., Fitzgerald W.F., Mason R., Vandal G., Powell D., Rada R., Rislov L., Winfrey M., Elder J., Kra bbenhoft D., Andren A.W., Babiarz C., Porcella D.B., Huckabee J.W. 1994 Sources and fates of mercury and methylmercury in Wisconsin lakes. In: Watras C.J. and Huckabee J.W., eds. Mercury Pollution: Integration and Synthesis , Lewis Publishers. p. 153-177. Watras C.J., Morrison K.A., Back R.C. 1996 Mass balance studies of mercury and methylmercury in small, temperate/boreal lakes of the northern hemisphere. In: Baeyens W., Ebinghaus R. and Vasiliev O., eds. Global and Regional Mercury Cycles: Sources, Fluxes and Mass Balances. , NATO Advanced Science Institute Series 2: Environment, Kluwer Academic Publishers. p. 329-358. Watras C.J., Back R.C., Halvorsen S., H udson R.J.M., Morrison K.A., Wente S.P. 1998. Bioaccumulation of mercury in pelagic freshwater food webs. Sci. Tot. Environ. 219 : 183-208.

21

## 5. Published works

To date, results of the cooperative FCPC/W DNR project have been published in three peer-reviewed technical papers and three oral papers that were pres ented at international scientific meetings in the US and Europe . The peer-reviewed technical papers were published in three highly-regard ed international journals: 1) The Canadian Journal of Fisheries and Aquatic Sciences, 2) Envi ronmental Science and Technology and 3) Limnology and Oceanography. Those citations , in order of publication are:

Eckley C., Watras C.J., Hintelmann H., Mo rrison K., Kent A., Regnell O. 2005. Mercury methylation in the hypolimnetic waters of lakes with and w ithout connection to
wetlands in northern Wisconsin. Can. J. Fish. Aquat. Sci. 62 : 400-411.

Watras C.J., Morrison K.A., Kent A., Price N., Regnell O., Eckley C., Hintelmann H., Hubacher T. 2005. Sources of methylmercury to a wetland-dominated lake in
northern Wisconsin. Environ. Sci. Tech. 39 (13): 4747-4758.

Watras C.J., Morrison K.A., Regnell O., Kr atz T.K. 2006. The methylmercury cycle in Little Rock Lake during experime ntal acidification and recovery. Limnol. Oceanogr. 51 (1): 257-270.

Citations for the oral papers are:

Kent, A.D., C. J. Watras, C. Eckley, O. Regnell, K. D. McMahon and H. Hintelmann. 2005. Microbial community composition and mercury methylation in the anoxic hypolimnia of stratified Wisconsin lake s. ASLO Annual Summer Meeting, June 19-24, 2005, Santiago de Compostela, Spain

Kent, A.D., C. J. Watras, C. Eckley, O. Regnell, K. D. McMahon and H. Hintelmann. 2005 Mercury Methylation Varies w ith Pelagic Microbial Community

22Composition in Lakes Within the Great La kes Basin. International Association for
Great Lakes Research: 48 th Annual Meeting, Ann Arbor MI, May 23-27, 2005.

Kent, A.D. C.J. Watras, O. Regnell, C. Ec kley and H. Hintelmann. 2005. Analysis of microbial community structure associated with mercury methylation in northern
Wisconsin lakes. Am. Soc. Limnol O ceanogr. Aquatic Sciences Meeting, Salt Lake City, February, 2005

Complete copies of the technical papers and published abstracts of the oral papers follow.

23

## 6. Appendices
Appendix A1. DL Stream Data A1.1. H&W data: 1995 - 2002 A1.1.1. Tributary Stream (Upstream site) A1.1.2. Tributary Stream (Inlet site) A1.1.3. Distributary Stream (Outlet site) 

### A1.2. TRL data: 2003 A1.2.1. Tributary Stream (Inlet site) Summary A1.2.2. Tributary Stream (Inlet site) Total mercury data A1.2.3. Tributary Stream (Inlet site) Methylmercury data A1.2.4. Tributary Stream (Inlet site) pH, SPM and Chl a data A1.2.5. Distributary Stream (Outlet site) Summary A1.2.6. Distributary Stream (Outlet site) Total mercury data A1.2.7. Distributary Stream (Ou tlet site) Methylmercury data A1.2.8. Distributary Stream (O utlet site) pH, SPM and Chl a data 

### A1.3. FCPC data: 2004 A1.3.1. Tributary Stream (Upstream site) A1.3.2. Tributary Stream (Inlet site) A1.3.3. Distributary Stream (Outlet site) 

### Appendix A2. DL Lake Data A2.1. H&W data: 1995-2002 A2.1.1. Lake1 site A2.1.2. Lake2 site 

### A2.2. TRL data: 2002-4 A2.2.1. Data summary A2.2.2. Total mercury data A2.2.3. Methylmercury data A2.2.4. pH, SPM and Chl a data 

### A2.3. FCPC data: 2004 Appendix A3. Precipitation Data: 2002-2004 A3.1. FCPC site A3.1.1. FCPC summary A3.1.2. FCPC duplicate IVL data 

### A3.2. Trout Lake site Appendix A4. Total Gaseous Mercury Data A4.1. Mean Daily TGM at Trout Lake site A4.2. Mean Hourly TGM at Trout Lake (CD only) A4.3. TEK files (CD only)