Mercury In Fish Tissue Research Articles

The effects of heavy metals exposure on reproductive systems of cyprinid fish from Kor River

The Kor River (Fars province) was divided into three parts and water and fish specimens were collected monthly and the concentrations of four heavy metals were determined using the Induction Coupled Plasma Method. As middle sampling zone was the main entrance and discharges of industries into the River, the concentrations of heavy metals in tissue of fish from this zone were significantly higher (p 0.05) were detected between the two sexes and species. Maximum concentrations of lead, mercury and cadmium in fish tissues were higher than the permissible levels for human consumption. Significant changes in the concentrations of steroid hormones were also noticed between the middle and two other sampling zones. Also in middle sampling zone, pathological changes in blood cells, liver, and kidneys of fishes were significantly higher. So heavy metals exposure can effectively decrease estrogenic and androgenic secretion in fish. The results confirmed exposure of fishes to heavy metals not only disrupts reproductive hormones’ secretion, but also induces some pathological changes.

An evaluation of mercury levels in Louisiana fish: Trends and public health issues

To characterize statewide fish tissue mercury levels in edible finfish the first comprehensive analysis of Louisiana's fish tissue mercury database was conducted. Analyses were based on fifteen years of fish tissue mercury data collected from 368 waterbodies between 1994 and 2008 (n = 14,344). The overall objectives of this study were to establish baseline fish tissue mercury levels; and evaluate species-specific temporal and spatial trends in fish tissue mercury levels. Fish tissue mercury levels ranged from 0.001 ppm (the detection limit) to 5.904 ppm for king mackerel; with an overall geometric mean of 0.218 ppm. Ninety-five percent of samples had mercury levels below the FDA's action level of 1.0 ppm for methylmercury in commercial food. Forty-four percent of all samples had mercury levels above the U.S. EPA's methylmercury fish tissue criterion of 0.3 ppm for sportfish. Species of potential concern include cobia, king mackerel, blackfin tuna, greater amberjack, spotted bass, bowfin, largemouth bass and freshwater drum. There was a significant but small decline in statewide length-adjusted largemouth bass mercury levels between 1994–1999 to 2003–2008 (p < 0.05). The highest fish mercury levels were observed in Pearl, Calcasieu, Mermentau, Ouachita, Pontchartrain and Sabine basins. Length-adjusted largemouth bass mercury levels were significantly higher in wetlands and rivers/streams vs. lakes; and in wetlands vs. estuaries (p < 0.05). Data were analyzed from a public health perspective to make recommendations for optimizing monitoring and outreach.

Does proximity to coal-fired power plants influence fish tissue mercury?

Much of the mercury contamination in aquatic biota originates from coal-fired power plants, point sources that release mercury into the atmosphere. Understanding mercury dynamics is primarily important because of the toxic threat mercury poses to wildlife and humans through the consumption of contaminated fish. In this study, we quantified the relative importance of proximity to coal-fired power plants on mercury accumulation in two fish species of different trophic positions. Fish, water and sediment were collected and analyzed from 14 lakes, seven near to (<10 km) and seven far from (>30 km) coal-fired power plants. Lower tissue mercury and higher tissue selenium concentrations were measured in fish collected near power plants. Moreover, mercury accumulation in fish was driven by biotic characteristics (e.g., trophic position, total length, age), waterbody characteristics (e.g., pH, dissolved organic carbon and sulfate) and distance from power plants. Proximity to an atmospheric point-source of mercury and selenium, such as a coal-fired power plant, affects the quantities of mercury and selenium accumulated in fish tissue. Differences in accumulation are hypothesized to be driven in part by selenium-mitigated reductions in fish tissue mercury near power plants. Although reduced fish tissue mercury in systems near power plants may decrease mercury-specific risks to human consumers, these benefits are highly localized and the relatively high selenium associated with these tissues may compromise ecological health.

A simple classical wet digestion technique for the determination of total mercury in fish tissue by cold-vapour atomic absorption spectrometry in a low technology environment

Four classical wet digestion procedures for the determination of mercury (Hg) by cold-vapour atomic absorption spectrometry in fish tissue were investigated with the aim of selecting and optimising the most convenient and inexpensive for use in a low technology environment. A mixture of H 2O, HNO 3, HClO 4 and H 2SO 4 or a mixture of HCl, HNO 3, HClO 4 and H 2SO 4 was used for the digestion in two different vessels namely thick walled long neck 50 ml volumetric flask and 50 ml 26 mm × 200 mm pyrex test tube. The effect of temperature and time on the digestion efficiency of the mixture of HCl, HNO 3, HClO 4 and H 2SO 4 using test tubes were investigated to obtain the optimum conditions. Mercury was partly lost at temperatures above 230 °C and this was pronounced when decomposition time was more than 30 min. Detection limit for the optimised procedure was 0.52 ng g −1. The optimised procedure was employed to study the level of Hg in canned fish samples. Concentration of Hg in the samples tested ranged from 0.015 to 0.139 μg g −1 wet weight.

Multiple Spiking Species-Specific Isotope Dilution Analysis by Molecular Mass Spectrometry: Simultaneous Determination of Inorganic Mercury and Methylmercury in Fish Tissues

This work demonstrates, for the first time, the applicability of multiple spiking isotope dilution analysis to molecular mass spectrometry exemplified by the speciation analysis of mercury using GC(EI)MS instrumentation. A double spike isotope dilution approach using isotopically enriched mercury isotopes has been applied for the determination of inorganic mercury Hg(II) and methylmercury (MeHg) in fish reference materials. The method is based on the application of isotope pattern deconvolution for the simultaneous determination of degradation-corrected concentrations of methylmercury and inorganic mercury. Mass isotopomer distributions are employed instead of isotope ratios to calculate the corrected concentrations of the Hg species as well as the extent of species degradation reactions. The isotope pattern deconvolution equations developed here allow the calculation of the different molar fractions directly from the GC(EI)MS mass isotopomer distribution pattern and take into account possible impurities present in the spike solutions employed. The procedure has been successfully validated with the analysis of two different certified reference materials (BCR-464 and DOLT-4) and with the comparison of the results obtained by GC(ICP)MS. For the tuna fish matrix (BCR-464), no interconversion reactions were observed at the optimized conditions of open focused microwave extraction at 70 degrees C during 8 min. However, significant demethylation was found under the same conditions in the case of the certified dogfish liver DOLT-4. Methylation and demethylation factors were confirmed by GC(ICP)MS. Transformation reactions have been found to depend on the sample matrix and on the derivatization reagent employed. Thus, it is not possible to recommend optimum extraction conditions suitable for all types of matrices demonstrating the need to apply multiple spiking methodologies for the determination of MeHg and Hg(II) in biological samples. Double spike isotope dilution analysis methodologies using widespread GC(EI)MS instrumentation are proposed here for the routine analysis of inorganic mercury and methylmercury in fish samples. The estimated method detection limits were below 10 ng g(-1) for both mercury species. Precision was evaluated for the concentrations present in the certified reference materials (CRMs) which vary from 0.1 to 5 microg g(-1), achieving values of coefficients of variation ranging from 7% to 2%. The concentrations obtained in both CRMs analyzed were in excellent agreement with the certified values, demonstrating the accuracy of the method at these concentration levels.

On-line speciation of inorganic and methyl mercury in waters and fish tissues using polyaniline micro-column and flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry (FI-CVG-ICPMS)

A simple and efficient method for the determination of ultra-trace amounts of inorganic mercury (iHg) and methylmercury (MeHg) in waters and fish tissues was developed using a micro-column filled with polyaniline (PANI) coupled online to flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry (FI-CVG-ICPMS) system. Preliminary studies indicated that inorganic and methyl mercury species could be separated on PANI column in two different speciation approaches. At pH <3, only iHg could be sorbed and almost no adsorption of MeHg was found (speciation procedure 1). If the sample solution pH is approximately 7, both MeHg and iHg species could be sorbed on the PANI column. Subsequently both the Hg species were selectively eluted with 2% HCl and a mixture of 2% HCl and 0.02% thiourea respectively (speciation procedure 2). The adsorption percentage of iHg on the PANI column was unchanged even with acidity of the sample solution increased to 6 mol L(-1). Therefore, an acidic solution (5 mol L(-1) HCl), used for ultra-sound assisted extraction of the mercury species from biological samples, was used directly to separate MeHg from iHg in the fish tissues (tuna fish ERM-CE 463, ERM-CE 464 and IAEA-350) by PANI column using speciation procedure 1. The determined values were in good agreement with certified values. Under optimal conditions, the limits of detection (LODs) were 2.52 pg and 3.24 pg for iHg and MeHg (as Hg) respectively. The developed method was applied successfully to the direct determination of iHg and MeHg in various waters (tap water, lake water, ground water and sea-water) and the recoveries for the spiked samples were in the range of 96-102% for both the Hg species.

Analytical speciation of mercury in fish tissues by reversed phase liquid chromatography–inductively coupled plasma mass spectrometry with Bi3+ as internal standard

In this work, the quantification of two mercury species (Hg2+ and CH3Hg+) in fish tissues has been revisited. The originality of our approach relies on the use of Bi3+ as internal standard (IS) and on the modification of typical extraction conditions. The IS (125μl, 1000μgl−1 Bi3+) was added to the aliquot of fresh fish tissue (400–500mg). A high-speed blender and ultrasound-assisted homogenization/extraction was carried out in the presence of perchloric acid (1.5ml, 0.6moll−1), l-cysteine (500μl, 0.75moll−1) and 500μl toluene:methanol (1:1). Perchloric acid was used for protein denaturation and precipitation, toluene helped to destroy lipid structures potentially sequestering CH3Hg+, l-cysteine was used to form water-soluble complexes with Bi3+, Hg2+ and CH3Hg+. The excess of perchloric acid was eliminated by addition of potassium hydroxide (pH 5 with acetic acid). The obtained extract, was diluted with the mobile phase (1:1) and introduced (20μl) to the reversed phase HPLC–ICP-MS system. The separation was achieved by isocratic elution (2.5mmoll−1 cysteine, 12.5mmoll−1 (NH4)2HPO4, 0.05% triethylamine, pH 7.0:methanol (96:4)) at a flow rate 0.6mlmin−1. Column effluent was on-line introduced to ICP-MS for specific detection of 202Hg, 200Hg and 209Bi. Analytical signal was defined as the ratio between 202Hg/209Bi peak areas. The detection limits evaluated for Hg2+ and CH3Hg+ were 0.8 and 0.7μgl−1. Recovery of the procedure, calculated as the sum of species concentrations found in the sample with respect to total ICP-MS-determined Hg was 91.9% for king mackerel muscle and 89.5% for red snapper liver. In the standard addition experiments, the recovery results were 98.9% for Hg2+ and 100.6% for CH3Hg+. It should be stressed that the use of Bi3+ as IS enabled to improve analytical performance by compensating for incomplete extraction and for imprecision of sample handling during relatively non-rigorous protocol.

Evaluating the spatial variation of total mercury in young-of-year yellow perch ( Perca flavescens), surface water and upland soil for watershed–lake systems within the southern Boreal Shield

The primary objective of this research is to investigate relationships between mercury in upland soil, lake water and fish tissue and explore the cause for the observed spatial variation of THg in age one yellow perch ( Perca flavescens) for ten lakes within the Superior National Forest. Spatial relationships between yellow perch THg tissue concentration and a total of 45 watershed and water chemistry parameters were evaluated for two separate years: 2005 and 2006. Results show agreement with other studies where watershed area, lake water pH, nutrient levels (specifically dissolved NO 3 −-N) and dissolved iron are important factors controlling and/or predicting fish THg level. Exceeding all was the strong dependence of yellow perch THg level on soil A-horizon THg and, in particular, soil O-horizon THg concentrations (Spearman ρ = 0.81). Soil B-horizon THg concentration was significantly correlated (Pearson r = 0.75) with lake water THg concentration. Lakes surrounded by a greater percentage of shrub wetlands (peatlands) had higher fish tissue THg levels, thus it is highly possible that these wetlands are main locations for mercury methylation. Stepwise regression was used to develop empirical models for the purpose of predicting the spatial variation in yellow perch THg over the studied region. The 2005 regression model demonstrates it is possible to obtain good prediction (up to 60% variance description) of resident yellow perch THg level using upland soil O-horizon THg as the only independent variable. The 2006 model shows even greater prediction ( r 2 = 0.73, with an overall 10 ng/g [tissue, wet weight] margin of error), using lake water dissolved iron and watershed area as the only model independent variables. The developed regression models in this study can help with interpreting THg concentrations in low trophic level fish species for untested lakes of the greater Superior National Forest and surrounding Boreal ecosystem.

Seasonal differences in mercury accumulation in Trichiurus lepturus (Cutlassfish) in relation to length and weight in a Northeast Brazilian estuary

Background, aim, and scope At tropical latitudes, and especially on the semi-arid coasts of the Brazilian Northeast, the rainfall regime governs the water quality of estuaries due to the pronounced difference between the rainy and dry seasons. These changes may be responsible for seasonal changes in bioavailability of mercury (Hg) and other pollutants to the estuarine and coastal biota. Mercury bioaccumulates along estuarine–marine food chains usually result in higher concentrations in tissues of top predators and posing a risk to both marine mammals and humans alike. The Goiana River Estuary (7.5° S) is a typical estuary of the semi-arid tropical regions and supports traditional communities with fisheries (mollusks, fish, and crustacean). It is also responsible for an important part of the biological production of the adjacent coastal waters.

Robust microwave-assisted extraction protocol for determination of total mercury and methylmercury in fish tissues

A rapid and efficient closed vessel microwave-assisted extraction (MAE) method based on acidic leaching was developed and optimized for the extraction of total mercury (Hg), inorganic mercury (Hg 2+) and methylmercury (CH 3Hg +) from fish tissues. The quantitative extraction of total Hg and mercury species from biological samples was achieved by using 5 mol L −1 HCl and 0.25 mol L −1 NaCl during 10 min at 60 °C. Total Hg content was determined using inductively coupled plasma mass spectrometry (ICP–MS). Mercury species were measured by liquid chromatography hyphenated with inductively coupled plasma mass spectrometry (LC–ICP–MS). The method was validated using biological certified reference materials ERM-CE464, DOLT-3, and NIST SRM-1946. The analytical results were in good agreement with the certified reference values of total Hg and CH 3Hg + at a 95% confidence level. Further, accuracy validation using speciated isotope-dilution mass spectrometry (SIDMS, as described in the EPA Method 6800) was carried out. SIDMS was also applied to study and correct for unwanted species transformation reactions during and/or after sample preparation steps. For the studied reference materials, no statistically significant transformation between mercury species was observed during the extraction and determination procedures. The proposed method was successfully applied to fish tissues with good agreement between SIDMS results and external calibration (EC) results. Interspecies transformations in fish tissues were slightly higher than certified reference materials due to differences in matrix composition. Depending on the type of fish tissue, up to 10.24% of Hg 2+ was methylated and up to 1.75% of CH 3Hg + was demethylated to Hg 2+.

An optimized digestion method coupled to electrochemical sensor for the determination of Cd, Cu, Pb and Hg in fish by square wave anodic stripping voltammetry

An optimized digestion method coupled to electrochemical detection to monitor lead, copper, cadmium and mercury in fish tissues was developed. Square wave anodic stripping voltammetry (SWASV) coupled to disposable screen-printed electrodes (SPEs) was employed as fast and sensitive electroanalytical method for heavy metals detection. Different approaches in digestion protocols were assessed. The study was focused on Atlantic hake fillets because of their wide diffusion in the human nutrition. Best results were obtained by digesting fish tissue with hydrogen peroxide/hydrochloric acid mixture coupled to solid phase (SP) purification of the digested material. This combined treatment allowed quantitative extraction from fish tissue (muscle) of the target analytes, with fast execution times, high sensitivity and avoiding organic residues eventually affecting electrochemical measurements. Finally, the method has been validated with reference standard materials such as dogfish muscle (DORM-2) and mussel tissues (NIST 2977).

Impact of phytochemical-rich foods on bioaccessibility of mercury from fish

The effects of phytochemical-rich foods on bioaccessibility of mercury in fish tissue (the amount of mercury that is released from fish into gastrointestinal tract fluid following a simulated digestion) were investigated using an in vitro digestion. Total mercury in the aqueous phase following a simulated digestion of fish with added food treatments was used to measure mercury bioaccessibility. Green tea extract (31–2000 mg), black tea extract (31–2000 mg), and soy protein (50–100 mg) significantly reduced mercury bioaccessibility by 82–92%, 88–91%, and 44–87%, respectively. Grapefruit juice (0.5–10 ml) did not reduce mercury in the aqueous phase. Wheat bran (50–1000 mg) decreased mercury bioaccessibility (84%); oat bran and psyllium reduced bioaccessibility (by 59–75%, 15–31%, respectively) at amounts greater than 500 mg. We therefore suggest that co-consumption of foods containing phytochemicals at the same time as fish that contains mercury may potentially reduce mercury absorption compared to eating fish alone.

P.1.c.004 Hyperalgesic effect of escitalopram in two animal models of acute pain

The growing Hg input in aquatic environments results in high accumulation of mercury in fish tissue and their consumers, which poses a serious risk to humans and ecosystems. The aim of this study was to evaluate the effects of the inorganic mercury exposure on cardiorespiratory responses in two species of neotropical fish ecologically distinct, matrinxã (Brycon amazonicus) and traíra (Hoplias malabaricus). Matrinxãs were exposed to a nominal and sublethal concentration of 0.15 mg L−1 of HgCl2 for 96 h. Traíras were exposed to trophic doses (each 4 days, during 30 days) of inorganic Hg (0.45 mg as total Hg) using juvenile B. amazonicus as prey vehicle. The metabolic rate (V˙O2), critical oxygen tensions (PcO2), gill ventilation (V˙G), tidal volume (VT), respiratory frequency (fR), O2 extraction from the ventilatory current (EO2), and heart rate (fH) were measured under normoxia (140 mmHg) and graded hypoxia (120, 100, 80, 60, 40, 20, and 10 mmHg). Regarding matrinxã specifically, the critical point highlighted was tachypnea. In traíras, bradypnea, decreased metabolic rate and O2 extraction, severe bradycardia, and elevated tidal volume were observed in normoxia. Both acute and sub-chronic exposures increased the critical tension of O2 values in more than 100%. In addition, Hg exposures modulated hypoxia-induced responses resulting in impairment of cardio-respiratory system of both species. Thus, mercury, via food or water, decreases the plasticity of the cardiorespiratory responses reducing the survival chances of B. amazonicus and H. malabaricus under hypoxic conditions frequently observed in theirs wild habitats.

Determination of Mercury in Fish Tissue Using a Minianalyzer Based on Cold Vapor Atomic Absorption Spectrometry at the 184.9 nm Line

A sensitive method was proposed and optimized for the determination of total mercury in fish tissue by using wet digestion, followed by cold vapor atomic absorption spectrometry (CVAAS) at the main resonance line of mercury (184.9 nm). The measurements were made using a new type of a non-dispersive mercury minianalyzer. This instrument was initially designed and built for atmospheric mercury-vapor detection. For determining mercury in aqueous samples, the minianalyzer was linked with a mercury/hydride system, Perkin Elmer Model MHS-10. To check the method, the analyzed samples were spiked with a standard solution of mercury. The recoveries of mercury spiked to wet fish tissue were >90% for 0.5 - 0.8 g samples. The results showed a better sensitivity (about 2.5 times higher) when using the mercury absorption line at 184.9 nm compared with the sensitivity obtained by conventional CVAAS at 253.7 nm.

Mercury Concentration in Frozen Whole-Fish Homogenates Is Insensitive to Holding Time

Current recommended holding times for the analysis of total mercury (Hg) in fish tissue ranges from 28 to 180 days. In 2006, we evaluated the effect of an extended holding time on Hg concentrations by reanalyzing whole-fish wet homogenates that were analyzed originally in 2002 and had been stored frozen at -20 degrees C since that time. Seven species, 13-15 samples each, were reanalyzed. Comparisons of concentration differences between 2006 and 2002 indicated that no statistically significant changes in Hg concentrations occurred in any of the seven fish species. These results indicate that wet fish tissue homogenates can be held frozen for at least four years without affecting analytical results, thus extending holding times far beyond those currently recommended.

Determination of Organic Mercury in Biota, Plants and Contaminated Sediments Using a Thermal Atomic Absorption Spectrometry Technique

A simple, rapid procedure for the determination of organic mercury in sediments, plants and fish tissues has been developed and validated. Extraction and separation of organic mercury compounds from the sample matrix was achieved by an established procedure based on an acid leaching of the sample (H2SO4/KBr/CuSO4), followed by extraction of the organic mercury halide with toluene and back-extraction with an aqueous solution of thiosulphate. Detection and quantification of mercury, in the liquid extracts, was made by atomic absorption spectrometry (AAS), following thermal decomposition of the sample. The method was evaluated using Certified Reference Material (CRM) BCR 463 (tuna fish), BCR 580 (estuarine sediment), IAEA-140TM (sea plant homogenate) and NRCC TORT-2 (lobster hepathopancreas). The recovery factors for organic mercury in all tested CRM were between 81–107%. The precision of the method has relative standard deviations of less than 10% for sediments and fish tissues and of less than 16% for plant material. The method was successfully applied to natural samples of sediments, plants, macroalgae and fish tissues collected from an estuarine ecosystem and could, therefore, be used for routine analyses.

An Evaluation of a Reagentless Method for the Determination of Total Mercury in Aquatic Life

Multiple treatment (i.e., drying, chemical digestion, and oxidation) steps are often required during preparation of biological matrices for quantitative analysis of mercury; these multiple steps could potentially lead to systematic errors and poor recovery of the analyte. In this study, the Direct Mercury Analyzer (Milestone Inc., Monroe, CT) was utilized to measure total mercury in fish tissue by integrating steps of drying, sample combustion and gold sequestration with successive identification using atomic absorption spectrometry. We also evaluated the differences between the mercury concentrations found in samples that were homogenized and samples with no preparation. These results were confirmed with cold vapor atomic absorbance and fluorescence spectrometric methods of analysis. Finally, total mercury in wild captured largemouth bass (n = 20) were assessed using the Direct Mercury Analyzer to examine internal variability between mercury concentrations in muscle, liver and brain organs. Direct analysis of total mercury measured in muscle tissue was strongly correlated with muscle tissue that was homogenized before analysis (r = 0.81, p < 0.0001). Additionally, results using this integrated method compared favorably (p < 0.05) with conventional cold vapor spectrometry with atomic absorbance and fluorescence detection methods. Mercury concentrations in brain were significantly lower than concentrations in muscle (p < 0.001) and liver (p < 0.05) tissues. This integrated method can measure a wide range of mercury concentrations (0–500 μg) using small sample sizes. Total mercury measurements in this study are comparative to the methods (cold vapor) commonly used for total mercury analysis and are devoid of laborious sample preparation and expensive hazardous waste.

Sediment from hydraulic mining detained by Englebright and small dams in the Yuba basin

Recent initiatives to find ways to reintroduce anadromous fish to the Central Valley of California have identified the Yuba River as one of the best potential watersheds for expanding spawning habitat of spring-run chinook salmon and steelhead trout. Salmon spawning in the Yuba River would require substantial modifications or removal of Englebright Dam, a large dam (86 million m 3 capacity) built by the U.S. Army Corps of Engineers in 1941. An extensive on-going feasibility study by local, state, and federal organizations, therefore, is examining aspects of various dam-treatment scenarios that range from no action to complete dam removal. This paper examines the extraordinary history of the watershed and resulting conditions pertinent to the feasibility of altering Englebright Dam. It seeks to accomplish four goals. First, historical geomorphic changes in the watershed are outlined that influence the physical context of the feasibility study. The Yuba watershed is centered in the hydraulic gold-mining region made famous by G.K. Gilbert ( Gilbert, G.K., 1917. Hydraulic-mining débris in the Sierra Nevada. U.S. Geol. Survey Prof. Paper 105 154 pp.), and Englebright Dam was built as a débris dam to control the sediment from hydraulic mining. Second, recent findings of high concentrations of mercury in sediment and fish tissues in the watershed are briefly reviewed. Much mercury was applied during the 20th century. Third, historic data on 20th century hydraulic mining are presented that document numerous small dams built in the Yuba basin to detain mining sediment. Finally, field measurements of the texture and lithology of modern bed materials in the Yuba River basin are presented that demonstrate reworked sediment from mining is an important component of the modern sediment load and fine spawning gravels. The complex anthropogenic geomorphic changes in the Yuba basin present a challenge with regards to responsible treatment of Englebright Dam. If toxic sediment is being reworked in the upper watershed, Englebright Reservoir may play an important role in protecting fish populations below in the Sacramento Valley. Where large volumes of mining sediment are stored behind small detention structures in the upper basin, they should be mapped and assayed for mercury. Stabilization or restoration options for these deposits should consider the potential role that they could play in supplying fine spawning gravel to the main channel.

Analysis of Mercury in Sportfish Tissue by Thermal Decomposition, Amalgamation/Atomic Absorption Spectrophotometry

Sportfish samples (n = 133) that originated from Indiana waters were analyzed for total mercury using inductively coupled plasma/mass spectrometry (ICP/MS) and thermal decomposition, amalgamation/atomic absorption spectrophotometry (TDA/AAS). Total mercury concentrations obtained by the two methods were not significantly different (P > 0.05). The correlation coefficient for total mercury obtained for the two methods was 0.94. The limit of detection using TDA/AAS was 0.1 ppm. TDA/AAS is a preferred technique for the analysis of total mercury in fish tissue because it is rapid (6 min per sample) and easy to use and requires little sample preparation.

Mercury Levels and Relationships in Water, Sediment, and Fish Tissue in the Willamette Basin, Oregon

In Oregon's Willamette River Basin (the Basin), health advisories currently limit consumption of fish that have accumulated methylmercury (MeHg) to levels posing a significant human health risk. These advisories created the requirement for a mercury total maximum daily load for the Basin, which required a greater understanding of the behavior, distribution, and levels of mercury and MeHg in the Basin. In 2002, the Oregon Department of Environmental Quality initiated a study to measure (using ultraclean techniques) mercury and MeHg levels in water, sediment, and fish samples collected throughout the Basin. Results from the Middle Fork (nominal background) suggested that naturally occurring surface-water concentrations of mercury and MeHg would on an annual average basis be expected in the range of 0.5 to 1.0 and 0.04 to 0.06 ng L(-1), respectively. Concentrations in the Coast Fork (Cottage Grove), which were markedly higher, are likely the result of historical mining discharges. The possibility exists that wetlands alone could contribute the dissolved MeHg levels (approximately 0.04 ng L(-1)) observed in the Main Stem. Mercury levels in sediment were similar, and near background, in the Main Stem, Coast Fork (Row River), and Middle Fork but significantly increased in the Coast Fork (Cottage Grove). Fish tissue mercury levels were typically highest in piscivorous and lowest in invertivorous species but highest in the Coast Fork (Cottage Grove). In the Coast Fork and Cottage Grove Reservoir, discharges from historical mercury mining activities appear to have significantly impacted water, sediment, and fish tissue levels; however these impacts do not appear to extend into the Main Stem. Basinwide mercury data are at present too spottily distributed to determine whether significant mercury point sources exist along the Main Stem.