Activated carbon mitigates mercury and methylmercury bioavailability in contaminated sediments

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1 Supplemental Information Activated carbon mitigates mercury and methylmercury bioavailability in contaminated sediments Cynthia C. Gilmour *, Georgia S. Riedel, Gerhardt Riedel, Seokjoon Kwon, Richard Landis, Steven S. Brown, Charles A. Menzie, and Upal Ghosh Contains: 23 pages of material, including detailed analytical methods, 15 figures, 4 tables and references. S1

2 Figure S1. Photos of microcosms. Bottom photos shows detail of Lumbriculus after several days in microcosm sediment, including live red worms burrowed into sediments, and grey worm casings on the sediment surface. S2

3 Table S1. Water chemistry of SERC stream W101, used for surface water in microcosm studies. Values are averages of weekly flow-weighted measurements for All data for 0.45 μm sampled water unless noted as particulate (P). Analytical Group (method) Parameter UNI AVG STD MERCURY (ICP- MS) FTHg ng/l FMeHg ng/l PMeHg ng/g PTHg ng/g ph ph ANIONS (IC) Br- µm Cl µm F µm NO2 µm NO3 µm SO4 µm PO4 µm CATIONS/METALS (ICP- OES) Al mg/l Ca mg/l Fe µg/l K mg/l Mg mg/l Mn µg/l Na mg/l P mg/l Si mg/l DOC (IR) DOC mg/l CDOM (uv/vis spec) acdom280 m SUVA280 L/mg/cm acdom440 m S nm S nm S nm S- R unitless NUTRIEN (colorimetric) NH4 µm NO2NO3 µm PO4 µm PC mg/l PN mg/l PP mg/l PARTICULATES (weight) SPM mg/l S3

4 Table S2. QA data for total Hg (THg) and MeHg analyses within this study. THg analyses were done by ICP-MS (worms, sediments) or CVAF (pore water). MeHg was done by isotope dilution ICP-MS, i.e. with internal stable isotope standards. RPDs are for duplicate analysis of the same prepared sample. CRMs for tissue analyses were NIST 1566b oyster tissue for THg and SRM 405 for MeHg. CRMs for sediment samples were MESS 3 for THg and SRM 405 for MeHg. CRMs were not available for every matrix. Blanks are process blanks, including filtration for pore waters. Detection limits were estimated based on 3X the standard error of blanks across samples. in this study. We evaluated the artifactual formation of MeHg during analysis using stable Hg isotope spikes to sample matrices. Very low levels of MeHg production can occur during MeHg analysis by Method 1631, a problem that is of most concern in samples with very high Hg to MeHg ratios, like these study sediments. Matrix RPD duplicates CRM recovery Spike Recovery Blanks DL Units THg Worms 1.5 ± 1.3 % 98.6 ± 5.5 % 99.9 ± 4.6 % 0.04 ± ng/gww Sediment 3.3 ± 2.3 % 102 ± 2.1 % 102 ± 5.8 % 0.08 ± ng/gdw Pore water 4.9 ± 3.7 % 97.9 ± 3.6 % 0.22 ± ng/l MeHg Worms 16.2 ± 1.3 % 88.1± 13.1 % 0.08 ± ng/gww Sediment 10.1 ± 7.0 % 91.8 ± 16.4 % 0.09 ± ng/gdw Pore water 7.9 ± 8.7 % NA 0.01 ± ng/l S4

5 Detailed analytical methods Sediment geochemical properties included: acid-volatile sulfur (AVS), chromium-reducible sulfur (CRS), 0.5 M HCl-extractable Fe(II) and Fe(III), organic matter content, moisture content/porosity, and bulk density. AVS and CRS were analyzed using methods described above for dissimilatory sulfate reduction. Extractable Fe(II) and Fe(III) were measured by light digestion of soil samples in 0.5 M HCl, centrifugation, and analysis of aliquots using ferrozine-hepes and UV spectrophotometry at 562 nm (Stookey 1970; Lovley and Phillips 1986). Extractable Fe(III) was determined as the difference between extractable total Fe and extractable Fe(II). Total extractable iron was obtained by reducing all Fe(III) using hydroxylamine (NH2OH) HCl prior to colorimetric analysis. Extractable Fe(III) samples below the detection limit were given values of 1/2 of the detection limit (3 mg g -1 ). Soil moisture content/porosity and bulk density were determined using standard gravimetric methods. Organic matter content was determined by loss-on-ignition (%LOI) of dried soil samples in a muffle furnace at 550 o C for 4 h. Major cations, P and Si were measured by ICP-OES after open-pan digestion with nitric, hydrochloric and hydrofluoric acids (Van Loon 1985). Acid volatile sulfide was analyzed by the cold 6N HCl + SnCl2 method of Cornwell and Morse (1987) and total reduced sulfur was analyzed by the hot CrCl 2 method of Canfield et al. (1986). Porewater chemistry. Anions in filtered microcosm surface and pore waters were measured using ion chromatography (AnionPac AS18 column, ICS-2000, Dionex Corp). Pore water concentrations of iron, manganese, sodium, calcium, magnesium, potassium and phosphorus were measured by ICP optical emission spectroscopy on a Perkin-Elmer Optima 3000DV ICP-OES. DOC concentrations were measured by high temperature combustion on a Shimadzu TOC-V total organic carbon analyzer. Ammonium, hardness and alkalinity were estimated in microcosm surface waters during the incubations using Hach kits. Sulfide samples were preserved in fresh sulfide antioxidant buffer and analyzed using an ion-selective electrode calibrated via lead titration of a saturated sulfide standard. Nutrients. Ammonia, nitrate+nitrite and phosphate were measured at in the Nutrient Analytical Services Laboratory at the University of Maryland Chesapeake Biological Laboratory. Ammonium was measured using the phenol/hypochlorite method (Solorzano 1969; USEPA Method 350.1), and phosphate was analyzed using the molybdate/ascorbic acid method (USEPA Method 365.1), both using an AquaKem 250 Discrete Analyzer. Nitrite+nitrate concentrations were measured using cadmium reduction on an AutoAnalyzer II system (USEPA Method 352.3). The average RPD of duplicate analyses was 9.2% for NO 3 +NO 2, 14.8% for PO 4 and 0.4% for NH 4. Digest blanks averaged <1 ng/l, yielding DLs for sediments averaging 0.2 ng/gdw. Detection limits, based on three times the standard deviation of blanks, was 1.1 μm for NO 3 +NO 2, 0.06 μm for PO 4 and 0.9 μm for NH 4. S5

6 Characteristics of Study Sediments. The sediments tested were all fine-grained mineral sediments with moderate organic matter content (8-15% LOI) and dry bulk densities all <1 g/cm 3 (Table S3). With the exception of the South River sediments, all were enriched in P relative to Al (relative to crustal abundance), suggesting a history of nutrientenriched conditions. All of the sediments were reducing, with measurable acid-volatile sulfide (AVS) and little or no extractable Fe(III). Based on the degree of sulfurization of reactive Fe, both estuarine sediments had an excess of available reduced S available for FeS formation, while FeS formation was Fe limited in the freshwater sediments. Table S3. Characteristics of study sediments. All parameters given per gram dry weight sediment unless noted. Metal and cation data are total concentrations in digested sediments unless noted. DOP is the degree of pyritization and DOS is the degree of sulfurization of reactive Fe (Berner 1970; Boesen and Postma 1988). Parameter Units South River Lake Canal Creek Berry's Creek Avg. Std. Dev. Avg. Std. Dev. Avg. Std. Dev. Avg. Std. Dev. HgT µg/g MeHg ng/g % MeHg % <0.01 Porosity ml/cm LOI % Dry Bulk Density g/cc Al mg/g Ca mg/g Fe mg/g K mg/g Mg mg/g Mn mg/g Na mg/g P mg/g AVS µmoles/g CRS µmoles/g HCl- reactive Fe (II) µmoles/g HCl- reactive Fe (III) µmoles/g DOP fraction DOS fraction S6

7 10 8 DO, mg/l MRM AC 0 12/1 12/6 12/11 12/16 12/ ph 7 6 MRM AC 5 12/1 12/6 12/11 12/16 12/21 NH4, mg/l MRM AC /1 12/6 12/11 12/16 12/21 Figure S2. Surface water chemistry over time in South River microcosms. Worms were added 12/8. Airlines and air stones added 12/12. Lines show the average plus standard deviation of 5 replicate microcosms in each treatment. S7

8 9 8 DO, mg/l /10 2/15 2/20 2/25 3/2 8 MRM 7 ph NH4, mg/l 6 5 2/10 2/15 2/20 2/25 3/ MRM MRM 0.0 2/10 2/15 2/20 2/25 3/2 Figure S3. Surface water chemistry over time in Lake microcosms. Worms were added 2/17. Lines show the average plus standard deviation of 5 replicate microcosms in each treatment. S8

9 DO,$mg/L$ 10" 9" 8" 7" 6" 5" 4" Low" Med" High" 3" 2/4" 2/9" 2/14" 2/19" 2/24" 8.5" 8.0" ph$ 7.5" Low" Med" High" 7.0" 2/4" 2/9" 2/14" 2/19" 2/24" 1.0" NH4+,$mg/L$ 0.5" Low" Med" High" 0.0" 2/4" 2/9" 2/14" 2/19" 2/24" Figure S4. Surface water chemistry over time in Canal Creek microcosms. Worms were added 2/10. Lines show the average of 5 replicate microcosms in each treatment. Standard deviations on each average were less than the differences among treatments. S9

10 DO, mg/l GT74 4 3/11 3/15 3/19 3/23 3/27 3/ ph 6 CONTROL GT74 4 3/11 3/15 3/19 3/23 3/27 3/31 NH4, mg/l CONTROL GT /11 3/15 3/19 3/23 3/27 3/31 Figure S5. Surface water chemistry over time in Berry s Creek microcosms. Worms were added 3/18. Lines show the average of 5 replicate microcosms in each treatment plus standard deviation of 5 replicate microcosms in each treatment. S10

11 MeHg, ng/gdw % MeHg THg, µg/gdw THg, µg/gdw Figure S6. Across the four study sites, MeHg concentrations are not strongly related to total Hg concentrations. Relationships between total Hg in sediments and sediment MeHg (left) or MeHg as a percentage of THg (right) for the four study sites. S11

12 1E+08& 1E+08& 1E+07& 1E+07& K D& 1E+06& K D& 1E+06& 1E+05& 1E+05& 1E+04& 0& 5& 10& 15& 20& 1E+04& 0.50& 0.70& 0.90& LOI,&% & Porosity,&ml/cc & 1E+08& 1E+08& 1E+07& 1E+07& K D& 1E+06& K D& 1E+06& 1E+05& 1E+05& 1E+04& 0& 200& 400& 600& 800& 1000& 1200& 1E+04& 0& 1& 2& 3& 4& CRS,&µmoles/g& conducovity,&ms& 1E+08& 1E+08& 1E+07& 1E+07& K D& 1E+06& K D& 1E+06& 1E+05& 1E+05& 1E+04& 0& 5& 10& 15& 1E+04& 0& 50& 100& 150& pw&sulfide,&μm& pw&fe,&μm& Figure S7. Relationships between sediment water partition coefficients (K D ) for total Hg (blue) and MeHg (red) and some key physical and chemical variables in sediments, for the four study sites. S12

13 Figure S8. Sediment:water Hg i (blue) and MeHg (red) partitioning predicts bioaccumulation among a set of untreated contaminated sediments. Plots show the relationships between Hg and MeHg concentrations in worms and pore water (top), and between sediment:water partition coefficients and sediment bioaccumulation factors (bottom). Each data point is the average ± standard deviation for the five control microcosms for each of four study sites, after 14-day incubation. Both relationships are significant at p < 0.001, based on linear regression of log-transformed data. S13

14 THg MeHg Worm Hg, ng/gww Sediment Hg (µg/gdw) or MeHg (ng/gdw) Figure S9. Log-log relationships between sediment Hg and MeHg concentrations and uptake of each by Lumbriculus, in unamended control microcosms. S14

15 Table S4. Percent reductions in Hg and MeHg uptake by Lumbriculus variegatus in 14- day microcosm experiments, relative to unamended control microcosms. AC MRM GT-74 Hg South River 84 ± 4% 76 ± 6% 41 ± 10% Lake 49 ± 27% 44 ± 13% 12 ± 13% Canal Creek - 50 ± 20% Berry's Creek - 36 ± 54% -6.0 ± 56% 1 ± 20% MeHg South River 90 ± 2% 96 ± 1% 71 ± 6% Lake 53 ± 3% 60 ± 3% -53 ± 9% Canal Creek 63 ± 6% Berry's Creek 29 ± 12% 32 ± 19% 54 ± 7% S15

16 MeHg uptake (fraction reduction) MeHg uptake (fraction reduction) THg sediments, ug/g porewater Hgi, ng/l 1.5 MeHg uptake (fraction reduction) % 10% 20% 30% % MeHg in sediments MeHg uptake (fraction reduction) AC MRM GT porewater MeHg, ng/l Figure S10. The effectiveness of amendments in reducing MeHg uptake by worms is not related to the total Hg content or pore water Hg concentration in untreated sediments (top), but is weakly related to the percentage of Hg as MeHg in untreated site sediments, and to the MeHg concentration in pore water. The plots show the relationships between bulk sediment THg (top left), pore water Hgi (top right), %MeHg in bulk sediments (bottom left) and pore water MeHg (bottom right) for untreated sediments; and the reduction in MeHg uptake by Lumbriculus achieved for each amendment. MeHg uptake is expressed as the fraction of uptake in unamended sediments. Each data point is the average value for the five microcosms in each (sediment X amendment) treatment after 14 days incubation. S16

17 Impact of Amendments on sediment, pore water and surface water chemistry in the microcosms At the end of the 14-day experiment, sediment and pore water chemistry were examined. None of the amendments had large effects on ph or dissolved oxygen (DO) in microcosm surface waters (Figure S7). Activated carbon and amendments had generally minor impacts on the concentrations of divalent cations (Ca, K, Mg, Mn and Na) in microcosm surface waters (data not shown). and AC often decreased surface water ammonium and nitrate levels (Figure S8). The amendments had small effects on surface water sulfate; but some amendments increased pore water sulfate in some sediments (Figure S9). One of the most consistent effects of amendments was the impact of AC amendment on pore water DOC (Figure S10). The organoclay amendment (MRM) led to significant increases in conductivity, sulfate, nitrate and iron in the microcosms (Figures S8, S9, S11), suggesting that this material released salts to the amended sediments. This amendment, used only in the experiments with freshwater sediments, was the least effective of the tested materials. In one of these sediments (Lake), MRM additions resulted in increased MeHg concentrations in pore water and increased MeHg uptake by worms (Figure 2). All of the microcosms contained detectable sulfide in pore waters (Figure S11). AC tended to decrease pore water sulfide levels, but not dramatically. AC amendment also resulted in a large increase in pore water Fe, and to a lesser extent Mn concentrations in two of the sediments. Thus AC amendments may result in alterations in sediment redox chemistry. Taken together, decreases in surface water NH 4, increases in pore water sulfate and iron, and decreases in pore water sulfide suggest that AC may reduce microbial ammonification and sulfate reduction, and perhaps overall microbial activity, in sediments. and MRM had similar effects, but they were less pronounced. Direct measurements of microbial activities would be needed to understand the mechanisms leading to these changes. Microcosm surface water was monitored from the time the microcosms were set up through the 14-day Lumbriculus uptake study. In microcosm surface waters, O 2, NH 4 + and ph were measured every few days. Time course data for each microcosm study is shown in Figures S S17

18 8.0$ 7.5$ ph$ 7.0$ 6.5$ 6.0$ $ $ MRM$ $ $ $ MRM$ $ $ $Low$ $Med$ $High$ $ $ GT74$ $ South$River$ Lake$ Canal$Creek$ Berry's$Creek$ 10" 9" 8" DO,"mg/L" 7" 6" 5" " MRM" " MRM" Low" Med" High" " GT74" South"River" Lake" Canal"Creek" Berry's"Creek" Figure S11. Impact of amendments on microcosm surface water ph and oxygen. Each bar represents the average value for 5 replicate microcosms on day 14. Treatments significantly different than control (ANOVA P <0.05) are labeled with stars. S18

19 1.5# NH 4,#mg/L# 1.0# 0.5# 0.0# # # MRM# # # # MRM# # # #Low# #Med# #High# # # GT74# # South#River# Lake# Canal#Creek# Berry's#Creek# 1.2# 1.0# NO 3,,#µM# 0.8# 0.6# 0.4# 0.2# 0.0# # # MRM# # # # MRM# # # #Low# #Med# #High# # # GT74# # South#River# Lake# Canal#Creek# Berry's#Creek# Figure S12. Impact of amendments on microcosm surface water ammonium (top) and nitrate (bottom). Each bar represents the average value for 5 replicate microcosms on day 14. Treatments significantly different than control (ANOVA P <0.05) are labeled with stars. S19

20 7" 6" SO 4,"mM" 5" 4" 3" 2" 1" 0" " MRM" " MRM" Low" Med" High" " GT74" South"River" Lake" Canal"Creek" Berry's"Creek" 5" 4" SO 4,"mM" 3" 2" 1" 0" " MRM" " MRM" Low" Med" High" " GT74" South"River" Lake" Canal"Creek" Berry's"Creek" Figure S13. Impact of amendments on sulfate in microcosm surface water (top) and pore water (bottom). Each bar represents the average value for 5 replicate microcosms on day 14. Treatments significantly different than control (ANOVA P <0.05) are labeled with stars. S20

21 ph MRM MRM Low Med High GT74 South River Lake Canal Creek Berry's Creek DOC, mg/l MRM MRM Low Med High GT74 South River Lake Canal Creek Berry's Creek Figure S14. Impact of amendments on sediment pore water chemistry. Each bar represents the average value for 5 replicate microcosms on day 14. Treatments significantly different than control (ANOVA P <0.05) are labeled with stars. S21

22 40" Sulfide,"uM" 20" 0" " MRM" " MRM" Low" Med" High" " GT74" South"River" Lake" Canal"Creek" Berry's"Creek" 14" 12" Fe,"mg/L" 10" 8" 6" 4" 2" 0" " MRM" " MRM" Low" Med" High" " GT74" South"River" Lake" Canal"Creek" Berry's"Creek" Figure S15. Impact of amendments on sediment pore water chemistry. Each bar represents the average value for 5 replicate microcosms on day 14. Treatments significantly different than control (ANOVA P <0.05) are labeled with stars. S22

23 References for Supporting Material Berner, R. A. Sedimentary pyrite formation. Am. J. Sci. 1970, 268, Boesen, C.; Postma, D. Pyrite formation in anoxic environments of the Baltic. Am. J. Sci. 1988, 288, Canfield, D. E.; Raiswell, R.; Westrich, J. T.; Reaves, C. M.; Berner, R. A. The use of chromium reduction in the analysis of reduced inorganic sulfur in sediments and shales. Chem. Geol. 1986, 54, Cornwell, J. C.; Morse, J. W. The characterization of iron sulfide minerals in anoxic marine-sediments. Mar. Chem. 1987, 22, Lovley, D. R.; Phillips, E. J. P. Organic-matter mineralization with reduction of ferric iron in anaerobic sediments. App. Environ. Microb. 1986, 51, Solorzano, L. Determination of ammonia in natural waters by the phenolhypochlorite method. Limnol. Oceanogr. 1969, 14, (5), Stookey, L. L. Ferrozine - a new spectrophotometric reagent for iron. Anal. Chem. 1970, 42, U.S. EPA. Method No in Methods for chemical analysis of water and wastes. United States Environmental Protection Agency, Office of Research and Development. Cincinnati, Ohio. Report No. EPA-600/ March pp. U.S. EPA. Method No Nitrogen, Nitrate-Nitrite (Colorimetric, Automated, Cadmium Reduction) in Methods for Chemical Analysis of Water and Wastes. United States Environmental Protection Agency, Office of Research and Development. Cincinnati, Ohio. Report No. EPA-600/ March pp. U.S. EPA Method Rev Determination of phosphorus by semi-automated colorimetry pp. U. S. EPA Method Determination of ammonia nitrogen by semi-automated colorimetry pp. S23