Methylmercury In Sediments Research Articles

Distillation, on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS as a new combination for the determination of methylmercury in sediments and fish tissue

Distillation as a way of sample digestion has been combined with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS (high performance liquid chromatography — ultra violet — post column oxidation — cold vapour atomic absorption spectrometry) for the determination of methylmercury at back-ground levels in sediments, soils and fish tissue. To prove the accuracy of this method, it was applied to sediment and fish tissue reference materials. The results correspond with the reference values within their error ranges. Excellent recoveries (92–95%) were obtained for the sediment samples by means of the standard addition method. The standard deviations of the sediment samples were within an acceptable range (7.2–12.5%), those of the fish samples were substantially lower (3.4–5.0%). The detection limit is 0.04 ng/g for 1 g sample weight.

GC-ECD Determination of Methylmercury in Sediment Samples Using a SPB-608 Capillary Column after Alkaline Digestion

The determination of methylmercury in sediment by gas chromatography with electron capture detector is proposed. Performance of a 0.53 μm i.d. capillary column SPB-608 has been evaluated. A procedure of extraction of methylmercury from sediment, based on an alkaline digestion (KOH/CH3OH) in ultrasonic bath followed by organic solvent extraction and cleanup step, has been optimized. Various alkaline and acid treatments as well as different digestion times have been tested. The performance of the method has been tested by participating in intercomparison and certification exercises for methylmercury in sediment organized by the Standards, Measurements, and Testing Programme of the European Union and by using an International Atomic Energy Agency certified reference sediment for methylmercury.

Determination of methylmercury in sediments using supercritical fluid extraction and gas chromatography coupled with microwave-induced plasma atomic emission spectrometry

Download options Please wait... Article information DOI https://doi.org/10.1039/AN9962100019 Article type Paper Download Citation Analyst, 1996,121, 19-29 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Determination of methylmercury in sediments using supercritical fluid extraction and gas chromatography coupled with microwave-induced plasma atomic emission spectrometry H. Emteborg, E. Björklund, F. Ödman, L. Karlsson, L. Mathiasson, W. Frech and D. C. Baxter, Analyst, 1996, 121, 19 DOI: 10.1039/AN9962100019 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Håkan Emteborg Erland Björklund Fredrik Ödman Lars Karlsson Lennart Mathiasson Wolfgang Frech Douglas C. Baxter

Measurement of mercury methylation in sediments by using enriched stable mercury isotopes combined with methylmercury determination by gas chromatography–inductively coupled plasma mass spectrometry

A novel technique for the calculation of mercury methylation rates in sediments by using enriched stable mercury isotopes is described. The method takes advantages of the ability of an inductively coupled plasma mass spectrometry (ICP-MS) instrument to measure individual isotopes. An ICP-MS instrument was used as a detector for the determination of methylmercury compounds after separation by gas chromatography (GC). CH3Hg+ was isolated from sediments by distillation, converted to methylethylmercury by sodium tetraethylborate and analysed after purge-and-trap pre-collection on a Tenax adsorber and thermodesorption onto the GC column. Detection limits were found to be ≈ 1 pg (as Hg) absolute or 0.02 ng g–1 dry sediment. The precision was ≈ 4% relative standard deviation when 250 pg of methylmercury were processed. The accuracy of the GC–ICP-MS technique was demonstrated by analysis of an International Atomic Energy Agency certified reference material (IAEA CRM 356) Harbor Sediment, giving a concentration of 5.40 ± 0.40 ng g–1, compared with the certified value of 5.46 ± 0.38 ng g–1. Mercury methylation was investigated by spiking sediments with stable enriched mercury isotopes at in situ mercury concentrations not perturbing the system. More than 3% of the mercury added to a lake sediment was methylated during a 21 d incubation period. Isotope ratios of total mercury differed significantly from isotope ratios of methylmercury at the end of the experiment, suggesting that the system was still not in equilibrium after 21 d.

Sulfate stimulation of mercury methylation in freshwater sediments

The relationship between bacterial sulfate reduction and mercury methylation, as well as the in situ distribution of methylmercury in sediments, was studied in Quabbin Reservoir, MA. Fish methylmercury levels in Quabbin and other lakes affected by acid deposition are often elevated. However, the cause of acceleration of net methylmercury production or bioaccumulation in these lakes is poorly understood. Experimental additions of sulfate to either anoxic sediment slurries or lake water above intact sediment cores resulted in increased microbial production of methylmercury from added inorganic mercury

Mercury and methylmercury in sediments and suspended particles from the river Elbe, North Germany

Total Hg and McHg concentrations have been determined in sediments and suspended particulate matter from one of the most Hg-polluted rivers of the world, the Elbe river in Northern Germany. Results of total Hg and McHg are presented. Total Hg concentrations in suspended particulate matter (SPM) are 30 mg kg−1 in the average and up to 150 mg kg−1 as the maximum value. Total Hg-fluxes −1 calculated from measurements of an automatically operating station upstream Hamburg as about 17 ta−1 in suspended particles. A new McHg determination by HPLC chromatography and photometric detection was developed and verified. Methylmercury concentrations were up to 10% of the total Hg, i. e. 2.7 mg kg−1 (dw).

Effects of acidification on mercury methylation, demethylation, and volatilization in sediments from an acid-susceptible lake.

The effect of experimental acidification on mercury methylation, demethylation, and volatilization was examined in surficial sediment samples from a weakly buffered northern Wisconsin lake. All mercury transformations were measured with radioisotopic tracers. Acidification of sediment pH with H2SO4, HCl, or HNO3 significantly decreased 203Hg(II) methylation. Acidification of pH 6.1 (ambient) sediments to pH 4.5 with either H2SO4 or HCl inhibited methylation by over 65%. The decreased methylation was due to the increased hydrogen ion concentration because methylation was not affected by concentrations of Na2SO4 or NaCl equimolar to the amount of acid added. Inhibition of methylation was observed even after prolonged acidification of sediments to pH 5.0 for up to 74 days. Acidification of sediments to pH 5.5, 4.5, and 3.5 with HNO3 resulted in a near complete inhibition of methylation at each pH. Similarly, the addition of equimolar amounts of NaNO3 resulted in a near complete inhibition of methylation, indicating that the inhibition was due to the nitrate ion rather than to the acidity. Demethylation of methyl mercury was not affected by pHs between 8.0 and 4.4, but sharply decreased below pH 4.4. Volatilization of 203Hg(II) from surface sediments was less than 2% of methylation activity and was not significantly different from that in killed sediments. This study indicated that acidification of sediments inhibits mercury methylation and that the observed increase in the mercury burdens in fish from low pH lakes is not due to increased production of methylmercury in sediments.

Mercury distribution in a polluted marine area. Concentrations of methyl mercury in sediments and some marine organisms

Methyl mercury concentrations were measured in various parts of Kaštela Bay in the Central Adriatic, which is polluted with inorganic mercury. The values obtained, on a wet weight basis, for sediments were from 2 to 20 μg methyl mercury kg −1; for the mussel Mytilus galloprovincialis from 10 to 110 μg kg −1; and for various species of fish from 102 to 1448 μg kg −1. The methyl mercury content increases by three orders of magnitude going from sediment to fish. The distribution of methyl mercury in relation to the depth of the sediment and the different organs of the mussel is presented. On the basis of the results obtained, it may be concluded that non-migratory species of fish are more suitable for methyl mercury monitoring in the marine environment than are sediment and mussels.

Mercury distribution in a polluted marine area [central Adriatic]: concentrations of methyl mercury in sediments and some marine organisms : Mikac, Nevenka and Mladen Picer, 1985. Sci. total Environment, 43(1–2):27–39

Mercury distribution in a polluted marine area [central Adriatic]: concentrations of methyl mercury in sediments and some marine organisms : Mikac, Nevenka and Mladen Picer, 1985. Sci. total Environment, 43(1–2):27–39

The rôle of speciation in mercury methylation in sediments and water

The rate and extent of the methylation of inorganic mercury has been shown to depend markedly on the chemical speciation of the mercury and the methylating agent. The presence of mercury (II)—chlorine covalent bonding has an inhibitory effect on methylation by methyl cobalamin (CH 3CoB 12) and in natural sediments. The rôle of radical and carbonium ion methylation mechanisms has also been investigated. In a typical estuarine sediment the extent of mercury methylation is as follows: Hg(OAc) 2 ⪢ Hg(cyst) 2 > Hg(cyst) (Hcyst)Cl > Hg(meth) 2 2+ > Hg(eth) 2 2+ > Hg(Hcyst)Cl 2 > HgCl 2 > (HgCl 2) 2 pen, where OAc = acetateHcyst = cysteine, meth = methionine, eth = ethionine and pen = penicillamine. This is consistent with mercury methylation arising by attack of a methyl carbanion (CH 3 −) on inorganic mercury (II) ions derived by microbial breakdown of the original and mercury compounds added.

Methylmercury production in the marine water column

Although the biosynthesis of methylmercury in sediments is well established1, this is not necessarily the exclusive natural source of methylmercury entering the marine food chain, particularly commercial fish and shellfish species for human consumption. An examination of mercury levels in freshwater fish2, collected from a lake with a history of industrial mercury contamination, suggested that levels in fish are controlled in part by mercury in suspension and it followed that methylation should occur in the water column. Although methylmercury is present in seawater in coastal areas receiving discharges of waste containing either inorganic mercury3 or methylmercury4 there is no evidence that methylmercury is actually formed in the water column. We now present data which demonstrate that inorganic mercury can be methylated in the water column and we compare this production with that known to occur in marine sediments.

Mercury Circulation in Aquatic Environment. Part 3: Mercury Transformations in Sediments

Two types of sediments, one of them highly polluted by the pulp and chemical industry and the other one polluted by the urban type of sewage, have been analysed for their content of methylmercury and inorganic mercury. The rate of the formation of methylmercury in sediment from inorganic mercury (II) and the decomposition of methylmercury and phenylmercury have been investigated using 203mercury compounds. It has been found that the rates of both processes depend on the experimental conditions. The quickest formation of methylmercury has been observed under the Procedure C which simulates the natural conditions. The lower the rate of demethylation of methylmercury the higher the equilibrium concentration of methylmercury which has been found in sediments.

Equilibrium concentrations of methylmercury in Ottawa River sediments

MOST of the mercury (up to 97%) found in aquatic systems is associated with bed sediments1. Fish, invertebrates and plants contain only 0.02% of the total, though they contain a high proportion of organic mercury. Field surveys show that the proportion of organic mercury in the sediments range from 0.1 to 2.1%2–6. Jacobs and Keeney placed river sediments mixed with inorganic mercury in the Wisconsin and Fox Rivers7. After 12 weeks exposure to the natural environment the concentration of methylmercury in the sediments was only 3%. This concentration of methylmercury was attained within 4 weeks after sediments were placed in the bottom of the rivers. This indicated that the processes of methylation and demethylation of mercury were in equilibrium in these environmental conditions within 4 weeks. But no experiments were conducted to show the degradation of methylmercury in sediments. After the methylation study by Jensen and Jernelov8, many investigations into methylmercury production by microorganisms in bed sediments have been carried out. Little attention, however, has been paid to the ratio of methyl-mercury to the total mercury existing in the sediments. Spangler et al. observed degradation of methylmercury in mixed cultures from sediments9. The degradation reached 50% within 5 d, they also found methylmercury degradation in sediments. But detailed information about the sediments was not available and results fluctuated wildly. We do not know the total amount of methylmercury existing in all components of the systems, including fish, invertebrates and plants as well as various types of bed sediments. Here we use methylmercury equilibrium concentration levels in the Ottawa River sediments to estimate the amount of methylmercury in various types of bed sediment where detailed information of total mercury concentrations (total mercury estimation 31 kg) and types of sediment is available. Two ways (methylmercury production and degradation) of reaching equilibrium were observed during 50 d in identical environmental conditions.

Education for planning (progress in planning, volume 1, part 1) : edited by D.R. Diamond and J.B. McLoughlin Pergamon Press, Inc. (Maxwell House, Fairview Park, Elmsford, New York 10523), 1973, 108 pp., paperback—$5.25

Thousands of hectares of wetlands are created annually because wetlands provide beneficial ecosystem services. Wetlands are also key sites for production of the bioaccumulative neurotoxin methylmercury (MeHg), but little is known about MeHg production in created systems. Here, we studied methylmercury in sediment, water, and invertebrates in created wetlands of various ages. Sediment MeHg reached 8 ng g−1 in the newest wetland, which was significantly greater than in natural, control wetlands. This trend was mirrored in several invertebrate taxa, whose concentrations reached as high as 1.6 μg g−1 in the newest wetland, above levels thought to affect reproduction in birds. The MeHg concentrations in created wetland invertebrate taxa generally decreased with increasing wetland age, possibly due to a combination of deeper anoxia and less organic matter accumulation in younger wetlands. A short-term management intervention and/or improved engineering design may be necessary to reduce the mercury-associated risk in newly created wetlands.