Μg Hg Research Articles

Membrane optode for mercury(II) determination in aqueous samples

A color changeable optode for Hg(II) was prepared by the immobilization of a dye 4-(2-pyridylazo)resorcinol (PAR) and a liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) in the tri-(2-ethylhexyl) phosphate plasticized cellulose triacetate matrix. Hg(II) and CH 3Hg + from aqueous samples could be quantitatively preconcentrated in this transparent optode producing a distinct color change ( λ max = 520 nm) within 5 min equilibration time in bicarbonate aqueous medium or 30 min in natural water. Whereas optode sample without Aliquat-336 did not change its color corresponding to Hg–PAR complex on equilibrium with the same aqueous solution containing Hg(II) ions. The uptake of Hg(II) was found to be pH dependant with a maximum (>90%) at a pH 7.5. The uptake of ions like Cu(II), Fe(II), Zn(II) and Pb(II) was negligible in the optode where as the uptake of Cd(II) and Zn(II) ions was 10–15% at pH 7.5. The optode developed in the present work was studied for its analytical application for Hg(II) in the aqueous samples by spectrophotometry, radiotracer ( 203Hg), Energy Dispersive X-ray Fluorescence (EDXRF) analyses and Instrumental Neutron Activation Analysis (INAA). The minimum amount of Hg(II) required to produce detectable response by spectrophotometry, INAA and EDXRF were found to be 5.5, 1 and 12 μg, respectively. This optode showed a linear increase in the absorbance at λ max = 520 nm over a concentration range of 0.22–1.32 μg/mL of Hg(II) ions in aqueous solution for 5 min. The preconcentration of Hg(II) from large volume of aqueous solution was used to extend the lower limit of concentration range that can be quantified by the spectrophotometry of optode. It was observed that preconcentration of 11 μg Hg(II) in 100 mL (0.11 μg/mL) in aqueous samples gives a distinct color change and absorbance above 3 σ of the blank absorbance. The optode developed in the present work was found to be reusable.

Gaseous mercury fluxes from the forest floor of the Adirondacks

The flux of gaseous elemental mercury (Hg 0) from the forest floor of the Adirondack Mountains in New York (USA) was measured numerous times throughout 2005 and 2006 using a polycarbonate dynamic flux chamber (DFC). The Hg flux ranged between −2.5 and 27.2 ng m −2 h −1 and was positively correlated with temperature and solar radiation. The measured Hg emission flux was highest in spring, and summer, and lowest in winter. During leaf-off periods, the Hg emission flux was highly dependent on solar radiation and less dependent on temperature. During leaf-on periods, the Hg emission flux was fairly constant because the forest canopy was shading the forest floor. Two empirical models were developed to estimate yearly Hg 0 emissions, one for the leaf-off period and one for the leaf-on period. Using the U.S. EPA's CASTNET meteorological data, the cumulative estimated emission flux was approx. 7.0 μg Hg 0 m −2 year −1.

Effect of dietary methylmercury and seleno-methionine on Sacramento splittail larvae

The effects of methylmercury (MeHg) and selenium (Se) contamination on food webs in the San Francisco Estuary have received considerable attention during the past decade. However, knowledge of their effects on native fishes of California is lacking. This study investigated the interactive effects of dietary MeHg and seleno-methionine (SeMet) on Sacramento splittail ( Pogonichthys macrolepidotus) larvae. Twelve diets containing increasing levels of SeMet (0.64, 8.2 and 35.0 µg Se g − 1 diet) and MeHg (0.01, 0.13, 4.7 and 11.7 µg Hg g − 1 diet) were fed to 21-day post-hatch larvae for 4 weeks in 2-L beakers at 25 °C. Fish were fed twice a day at a feeding rate of 40, 30, 25 and 20% of body weight during the 1st, 2nd, 3rd and 4th week, respectively. At the end of week 4, no significant difference ( P > 0.05) was observed among treatments for mortality, body length or weight, and condition factor. Bioaccumulation of Hg and Se responded positively and significantly ( P < 0.05) to their dietary concentrations. The molar ratio of Se/Hg in diets was linearly correlated to the ratio of Se/Hg in fish. Dietary Se inhibited Hg accumulation, which was negatively correlated to the dietary Se/Hg ratio. Histopathological examination revealed severe gill anomaly and liver glycogen depletion in fish fed the 11.7 µg Hg g − 1 diet. Liver glycogen depletion and kidney tubular dilation were found in larvae fed the 11.7 µg Hg and 11.7 µg Hg + 35 µg Se g − 1 diets. In conclusion, dietary Hg enhanced Se accumulation but dietary Se inhibited Hg accumulation in splittail. Dietary Se showed a protective effect in fish fed the high MeHg diet. This protection was related to the dietary Se/Hg ratio, which is a more reliable criterion for evaluating the interactive effect between Se and Hg in splittail.

Copper-Doped Silica Materials Silanized With Bis-(Triethoxy Silyl Propyl)-Tetra Sulfide for Mercury Vapor Capture

The use of Cu−S sites for Hg capture from the gas phase has been successfully applied to a silica-based platform using an S4 organic polysulfane and copper sulfate. The maximum fixed-bed equilibrium capacity achieved using these materials was 19 789 μg Hg·g −1 sorbent for a material with 2.5 wt % Cu and 6 wt % S. An optimal S level was determined to be around 3 wt % because enhancement of capacity was only 18% when increasing from this 3 to 6 wt %. The rate of adsorption in pure beds ranged from 0.6 to 1.6 μg Hg·min −1 depending on the inlet concentration. Differences in breakthrough times suggest that material deposition is not uniform. When compared to two other platforms, commercially available Darco HG-LH and previously tested Fe−Cu−S4 nanoaggregates, the Si-1 material performed the best in fixed-bed testing. During entrained-flow testing, a steady-state Hg removal of 82% was achieved using Si-1 at injection rates of both 6 × 10 −5 and 1.2 × 10 −4 g·L −1·h −1. The lack of increase in Hg removal when the injection rate is doubled suggests that pore accessibility is the rate-controlling step during dynamic Hg capture. A calculation of the approximate pore usage based on injection testing helped confirm this observation. During injection testing, the performance of Si-1 was only diminished 10% when exposed to 20 ppm SO 3. This is an encouraging result for flue-gas applications where SO 3 levels range from 1 to 40 ppm. Testing demonstrated that Si-1 is stable when exposed to leaching conditions after concrete blending and cement impregnation. This is an important aspect to consider for injection because the sale of fly ash for concrete is a key cost-recovery tool for power plants.

Genotypic variation in grain mercury accumulation of lowland rice

AbstractA pot experiment with 38 commonly cultivated rice cultivars from the Yangtze River Delta was conducted in a greenhouse to study the effect of mercury (Hg) contamination of a paddy soil (4.7 mg Hg [kg soil]–1) on crop growth and Hg accumulation in the grains. Mercury contamination differentially affected growth, grain yield, and Hg accumulation in brown rice of the tested cultivars. The average Hg concentration in the grains was significantly higher (p &lt; 0.01) when plants were grown in the Hg‐contaminated compared to the control soil. Averaged over cultivars, the Hg concentration in brown rice exceeded the maximum permissible limit of 20 μg Hg kg–1. Increasing Hg concentrations were associated with grain‐yield declines up to 70%. This yield decline was mainly due to a reduction in the number of panicles. Japonica cultivars tended to be generally less affected by Hg than indica cultivars. The two japonica cultivars Jiahua and Chunjiang 026 showed both low Hg concentrations and no Hg‐induced grain‐yield reduction. These cultivars may be preferred candidates for cultivation in Hg‐contaminated soils or for studies on possible Hg‐exclusion mechanisms.

Mercury deposition in the Adirondacks: A comparison between precipitation and throughfall

The volume-weighted mean (VWM) Hg concentrations and the total cumulative fluxes in deciduous throughfall (6.6 ng L −1 and 12.0 μg m −2, respectively) were statistically higher than in precipitation (4.9 ng L −1 and 11.6 μg m −2, respectively) during 2 years of sampling at the Huntington Wildlife Forest in Newcomb, NY. Seasonally, the VWM Hg concentrations and the Hg fluxes in both precipitation and throughfall were lowest in winter and highest in summer. Due to the wash-off of dry deposition and foliar leaching, concentrations in throughfall were almost 50% higher than those in precipitation during the leaf-on period, while concentrations in throughfall were slightly higher than (or similar to) those in precipitation during the leaf-off period. During the 2 years of sampling, the total deposited cumulative flux in precipitation and deciduous throughfall were very similar (11.6 μg Hg m −2 and 12.0 μg Hg m −2, respectively), because the higher concentrations in throughfall were offset by smaller throughfall depths. Meteorological analysis indicated that the precipitation events resulting in the highest Hg fluxes were associated with trajectories that passed through regions of Midwest where major Hg sources including coal/oil-fired power plants and waste incinerators are located.

Removal of mercury(II) from wastewater using camel bone charcoal

Camel bone charcoal is used as an adsorbent for the removal of Hg(II) from wastewater effluents. The equilibrium data are fitted to Langmiur isotherm rather than linear and Freundlich isotherms. The adsorption capacity Q o is 28.24 mg of Hg(II)/g of the adsorbent. The optimum removal conditions are pH 2, contact time 30 min and temperature 25 °C. A comparison of the adsorption capacity ( Q o) of camel bone charcoal with different adsorbents previously used for Hg(II) removal from wastewater effluents reveals its remarkable efficiency over many other treated and untreated natural and synthetic adsorbents. X-ray fluorescence and infrared spectrometry of camel bone charcoal after contact with mercury solutions confirm surface adsorption of Hg(II) ions. Electron microscopy reveals the formation of a spongy like structure on the adsorbent surface due to Hg(II) adsorption. Quantitative removal of mercury from hazardous effluents is demonstrated.

A regional analysis of the fate and transport of mercury in East Asia and an assessment of major uncertainties

The fate and transport of mercury in East Asia is evaluated using the Sulfur Transport and dEposition Model (STEM)-Hg 3-D model. The model calculates mercury transport, transformation and deposition in East Asia during April 2001, the period of the ACE-Asia field campaign. Model predictions of dry and wet deposition are compared with the observations from 10 sampling sites in Japan. The model results are consistent with the observations, but tend to over-predict dry deposition. Sensitivity analysis of predicted results to uncertainties in the mercury reaction rates suggests that the oxidation of Hg 0 to Hg(II) in the gas phase is the dominant pathway for atmospheric mercury removal processes. Simulation based on the most recently published reaction rate constants for gas phase oxidation of Hg 0 to Hg(II) overestimates the production of Hg(II) in the gas phase. The regional mercury budget is calculated which shows that most of the reactive gas phase mercury (RGM) and particulate mercury (Hg p) are deposited around the source region while 28.5 Mg of Hg 0 is exported out of East Asia during April 2001. The sensitivity analysis in the regional Hg budget to major uncertainties associated with Hg emission estimates and Hg chemistry are also evaluated.

Effects of dietary methylmercury on zebrafish skeletal muscle fibres

Mercury and more specifically methylmercury have been reported as hazardous environmental pollutants able to accumulate along the aquatic food chain with severe risk for animal and human health. Adult male zebrafish ( Danio rerio) were distributed in two groups: a control group (fed with uncontaminated food) and a MeHg-contaminated group (fed with food containing 13.5 μg Hg g −1 (dry wt)). Five fish per condition were removed after 7, 21 and 63 days. Bioaccumulation of mercury was determined and muscle samples from control and exposed groups were fixed for histological and ultrastructural studies. In contaminated muscles were observed a decrease of the inter-bundle surface, mitochondria with variable shapes, sizes and cristae disorganization, also decreasing the surface area and inter-bundle surfaces. Indeed, damage in the endoplasmic reticulum cisternae was observed. For statistical evaluation the damages in mitochondria was quantified by image. According to the current results, methylmercury affects the structure of fibre cells of D. rerio after trophic and low dose exposure.

Speciation analysis of mercury and lead in fish samples using liquid chromatography–inductively coupled plasma mass spectrometry

A liquid chromatography–inductively coupled plasma mass spectrometric (LC–ICP-MS) method for lead and mercury speciation analysis was described. Sample containing ionic lead and mercury compounds was subjected to liquid chromatographic separation before injection into the direct injection high efficiency nebulizer (DIHEN, 170-AA). The species studied include inorganic lead (Pb(II)), trimethyl lead (trimethyl-Pb), triethyl lead (triethyl-Pb), inorganic mercury (Hg(II)), methyl mercury (methyl-Hg) and ethyl mercury (ethyl-Hg), which were well separated by reversed-phase liquid chromatography with a C18 column as the stationary phase and a pH 2.8 solution of 0.2% (v/v) 2-mercaptoethanol, 1 mg L −1 ETDA, 174.2 mg L −1 sodium 1-pentanesulfonate and 12% (v/v) methanol as the mobile phase. The lead and mercury species in biological tissues were quantitatively extracted, into 10 g L −1 EDTA and 0.2% (v/v) 2-mercaptoethanol solution taken in a closed centrifuge tube and kept on water bath, using microwaves at 65 °C for 2 min. The spike recovery of individual lead and mercury species determined by spiking the samples with suitable concentration of lead and mercury mixture standard were between 93% and 99%. The detection limits of the species studied were in the range 0.1–0.3 μg Pb L −1 and 0.2–0.3 μg Hg L −1. The procedure has been applied for the speciation analysis of two reference samples namely NRCC DOLT-3 Dogfish Liver and DORM-2 Dogfish Muscle and a swordfish sample obtained locally. The sum of the concentrations of individual species has been compared with the certified values for total lead and mercury to verify the accuracy of the method. The precision between sample replicates was better than 10% with LC–DIHEN-ICP-MS method.

Spectrophotometric determination of chloride in waters using a multisyringe flow injection system

A multisyringe flow injection system (MSFIA) with spectrophotometric detection is proposed as a fast, robust and low-reagent consumption system for the determination of chloride (Cl −) in waters. The system is based in the classic reaction of Cl − with Fe 3+ and Hg(SCN) 2, but due to the hazardous properties of this last reagent, the proposed methodology has been developed with the aim to minimize the consumption of this one, consuming less than 0.05 mg of Hg for a Cl − determination, being the system of this type with the lowest Hg consumption. The linear working range was between 1 and 40 mg L −1 Cl − and the detection limit was 0.2 mg L −1 Cl −. The repeatability (RSD) was 0.8% for a 10 mg L −1 Cl − solution, and the injection throughput was 130 h −1. The proposed system is compared with other chloride monitoring flow systems, this comparison is realized with a point of view of the equilibrium between the obtained analytical features and produced residues toxicity. The proposed system was applied to the determination of Cl − in mineral, tap and well water.

Construction and evaluation of a flow injection micro-analyser based on urethane–acrylate resin

A flow injection micro-analyser with an integrated injection device and photometric detection is described. Channels measuring 205–295 μm depth by 265–290 μm maximum width were manufactured by deep UV lithography on two layers of urethane–acrylate oligomers-based photoresist. Hypodermic syringe needles (450 μm diameter) were connected to the channels for introduction of solutions into the system. Plastic optical fibres were connected to the ends of a 5.0 mm long channel, in order to conduct the light from and to a homemade photometer. The device has a total volume of 7.0 μL and three different sample volumes (0.09, 0.22 and 0.30 μL) can be inserted into the system by choosing the appropriate loop of the hydrodynamic injection approach. The micro-analyser, designed as a single line manifold, was evaluated by determining chloride in waters (mercuric thiocyanate method), and chromium (VI) in wastewater and total chromium in metallic alloys (diphenylcarbazide method). For chloride determination two micro-pumps were employed to impel the solutions, while for chromium determination this task was performed by a conventional peristaltic pump. The results obtained in all determinations did not differ significantly from the reference methods at a confidence level of 95%. In the chloride determination, a flow rate of 50 μL min −1 was used, providing a sample frequency of 45 injection h −1, generating ca. 0.7 mg of Hg(II) after an 8-h working day (ca. 20 mL of solution). This result suggests the potential of the micro-analyser towards the reduction of waste, following the philosophy of Green Chemistry.

Contaminants in organically and conventionally produced winter wheat ( Triticum aestivum ) in Belgium

A database has been compiled with the levels of important contaminants (mycotoxins, heavy metals and pesticides) measured from 2002 to 2005 in winter wheat (Triticum aestivum) grown in Belgium according to the organic and conventional farming systems. Assuming no further change in contaminant levels during cereal processing and during the preparation of foodstuffs, conservative intakes are estimated for the consumers of cereal-based products such as flour, bread, breakfast cereals, dough and pastry. The results show that for the consumer of organic foodstuffs, estimated daily intakes are 0.56 µg deoxynivalenol (DON), 0.03 µg zearalenone (ZEA), 0.19 µg Cd, 0.28 µg Pb and 0.0006 µg Hg kg−1 body weight, taking into account the average contaminant levels in unprocessed grains and the average cereal products consumptions in Belgium. For the consumers of conventional foodstuffs, the corresponding estimated daily intakes are 0.99 µg DON, 0.06 µg ZEA, 0.17 µg Cd, 0.12 µg Pb and 0.0007 µg Hg kg−1 body weight. In addition, it appears that for the consumers of conventional products, intakes of some post-harvest insecticides have to be taken into account (0.11 µg chlorpyriphos-methyl, 0.2 µg dichlorvos and 0.24 µg pirimiphos-methyl kg−1 bw). When expressed as a percentage of the tolerable/acceptable daily intake (TDI/ADI), it seems that the corresponding estimated (conservative) intakes are the highest for DON (56% for organic and 99% for conventional cereal products), ZEA (16% for organic and 32% for conventional cereal products), and Cd (19% for organic and 17% for conventional cereal products), all other estimated intakes of contaminants (including pesticides) being lower than 10% of the TDI/ADI.

Examination of Sulfur-Functionalized, Copper-Doped Iron Nanoparticles for Vapor-Phase Mercury Capture in Entrained-Flow and Fixed-Bed Systems

The use of copper-doped Fe nanoaggregates silanized with organic sulfur as bis-(triethoxy silyl propyl)-tetra sulfide has been investigated for the capture of elemental mercury (Hg0) from the vapor phase for potential power plant applications. Silanization procedures resulted in 70% deposition of the targeted sulfur level, with particles containing approximately 4 wt % S. The addition of copper was found to increase the fixed-bed (total) capacity of this type of sorbent from 170 ± 20 μg Hg·g sorbent-1 with no copper doping to 2730 ± 80 μg Hg·g sorbent-1 at 1.2 wt % Cu. When no S is deposited, the capacity of Fe/Cu nanoaggregates was only 180 μg Hg·g sorbent-1. These findings suggest that a combined Cu−S mechanism is responsible for Hg capture. Moving-bed (injection) testing of the Fe-based sorbents in a simulated flue gas stream showed that the 1.2 wt % Cu sample was able to achieve significant removal of the Hg. At a modest sorbent injection rate of 3.6 × 10-3 g·L-1·h-1, this material showed a steady-state removal capacity of 107.5 μg Hg·g sorbent-1 for an inlet concentration of 17.8 μg·m-3. On the basis of only 4% usage of the total capacity during single-pass injection, it might be beneficial to develop methods to separate and recycle these materials to reduce power plant operation costs for Hg emissions control.

Mercury contamination in the vicinity of a derelict chlor-alkali plant. Part I: Sediment and water contamination of Lake Balkyldak and the River Irtysh

A mercury-cell chlor-alkali plant operated in Pavlodar, Northern Kazakhstan, for 18 years and caused widespread contamination of the surrounding environment. Untreated wastewater from the plant was discharged to Lake Balkyldak, a shallow impounded lake without an outlet. The nearby River Irtysh was also suspected to be impacted by mercury (Hg) via the transport of contaminated groundwater. We took sediment and water samples from both aquatic systems, and also sampled soils along the shoreline of the lake and in the Irtysh flood plain. Sediments from Lake Balkyldak were found to be very heavily contaminated, with Hg concentrations in the surface layer reaching up to approximately 1500 mg kg(-1) near the wastewater outfall pipe. The contaminated lake sediments are prone to wind-driven resuspension and are acting as a strong source of Hg to the water column. Unfiltered lake water samples taken in shallow areas within 10-15 m from the shoreline contained from 0.11 microg Hg L(-1) in the less contaminated northern part of the lake to 1.39 microg L(-1) near the pollutant outfall in the south (up to 7.3 microg L(-1) on windy days). Sediments from the River Irtysh were only slightly impacted, with maximum Hg concentrations of 0.046 mg kg(-1) in the old river channel and 0.36 mg kg(-1) in floodplain oxbow lakes. In water samples from the River Irtysh, Hg was generally not detected, although trace concentrations (3 to 9 ng L(-1)) were found in some samples taken from oxbow lakes. We conclude that the river is not significantly impacted by Hg, but the highly contaminated Lake Balkyldak poses a threat and is in need of remediation. Potential remediation options for the lake are reviewed and are discussed in the context of experiences made at other Hg-contaminated sites.

MACROINVERTEBRATE PRODUCTION AND FOOD WEB ENERGETICS IN AN INDUSTRIALLY CONTAMINATED STREAM

This study examines secondary production and periphyton-invertebrate food web energetics at two sites in an industrially contaminated, nutrient-enriched stream. Secondary production data and data from the literature were used to calculate potential amounts of mercury transferred from periphyton to chironomid larvae and into terrestrial food webs with emerging adults. The nutritional quality of periphyton was characterized using energy content, chlorophyll a, protein, ash-free dry mass (AFDM), and percentage of organic matter. Chironomid larvae (Orthocladiinae: Cricotopus spp.) comprised 96% of all macroinvertebrates collected from stones at the two sites. Cricotopus production was extremely high: production was 59.5 g AFDM x m(-2) x yr(-1) at the site upstream of a 1-ha settling basin and 32.4 g AFDM x m(-2) x yr(-1) at the site below the basin. Apparent differences in annual secondary production were associated with reduced organic content (i.e., nutritional quality) of the periphyton matrix under different loading of total suspended solids. The periphyton matrix at both sites was contaminated with inorganic (Hg(II)) and methyl (MeHg) mercury. The amount of Hg(II) potentially ingested by Cricotopus was calculated to be 49 mg Hg(II) x m(-1) x yr(-1) at the upstream site and 19 mg Hg(II)x m(-2) x yr(-1) at the downstream site. Mercury ingestion by Cricotopus at the downstream site was calculated to be 2% of the estimated annual deposition of particulate-bound Hg(II) to the stream bed. Emergence of adult Cricotopus was calculated to remove 563 microg Hg(II)x m(-2) x yr(-1) from the stream at the upstream site and 117 microg Hg(II) x m(-2) x yr(-1) at the downstream site, which amounted to 4.1 g Hg(II)/yr for the 2.1-km reach of stream included in this study. The ratio of metal export in emergence production to surface area for the study stream was 10 to 10(3) times higher than ratios calculated for lakes using data from the literature. This study is the first well-documented example of extremely high aquatic insect production in an industrially contaminated, nutrient-enriched stream, and it highlights the application of production measurements to examine the role of aquatic insect production in the trophic transfer of energy and persistent contaminants in aquatic food webs and into terrestrial food webs.

Substoichiometric determination of mercury with cetyltrimethylammonium bromide

A radiometric method based on substoichiometric isotope dilution analysis has been developed for the determination of mercury using cetyltrimethylammonium bromide (CTAB) as the substoichiometric reagent. The method is based on the extraction of mercury as an ionassociation complex of tetraiodomercurate(II) ion with a substoichiometric amount of CTAB in benzene. The calibration graph was found to be linear in the range 0–10 μg Hg (II) in the aqueous phase of 10 ml volume. A detection limit of 0.06 μg·ml−1 could be achieved by the proposed method. The relative standard deviation of the method was found to be 3.0% and the method has been successfully applied to study the determination of mercury in various synthetic mixtures.

Development of a new HPLC method for the determination of inorganic and methylmercury in biological samples with ICP-MS detection

In the present work a new HPLC method for the determination of mercury species in biological samples with ICP-MS detection was developed. Separation of inorganic (Hg2+) and methylmercury (CH3Hg+) was accomplished on a Hamilton PRP-X200 polymer-based cation-exchange column with a mobile phase of 50 mmol l−1 pyridine, 0.5% w/w L-cysteine and 5% v/w MeOH, at pH 2, within 8 min. The influence of chromatographic parameters, such as pH, salt concentration, organic modifier, and ion-pair reagent on the retention behaviour was evaluated. Based on peak areas, the experimental detection limits for inorganic and methylmercury were 0.05 and 0.08 μg Hg l−1, which corresponds to an absolute detection limit of 1.0 and 1.6 pg of mercury (20 μl injection volume). The liquid chromatographic method was successfully applied to the determination of inorganic and methylmercury in the two certified reference materials DORM-2 and DOLT-3, after a rapid and simple sample preparation procedure using hydrochloric acid.

The determination of methylmercury in biological samples by HPLC coupled to ICP‐MS detection

AbstractThe use of high‐performance liquid chromatography (HPLC) coupled to inductively coupled plasma mass spectrometry (ICP‐MS) for the determination of methylmercury (MeHg+) in fish tissue and hair samples is described. Analysis of these sample types is required when carrying out biomonitoring studies to determine human dietary exposure to this toxic mercurial compound. The developed method used a mobile phase containing an organic modifier and a sulfydryl compound (1:1 v/v methanol:water containing 0.01% v/v 2‐mercaptoethanol) to limit peak tailing and aid separation. The chromatographic separation was coupled to the ICP‐MS detector via a short piece of PEEK tubing, attached to the nebulizer. A cooled spraychamber and oxygen addition post‐nebulization were required to limit the solvent loading on the plasma and reduce carbon build‐up on the cones, respectively. The sample preparation procedure employed a drying step followed by digestion of the sample using tetramethylammonium hydroxide (TMAH) and heating in an open vessel microwave system. Two fish tissue certified reference materials (CRM), tuna fish CRM 463 and 464 (BCR, Brussels), a tuna fish proficiency test sample, IMEP‐20 (IRMM, Geel, Belgium) and a hair CRM NIES no. 13 (National Institute of Environmental Science, Japan), were used to evaluate the method. The recovery of MeHg+ for these four materials was between 83 and 100%, with precisions better than 6% for three separate extractions of the different materials. The limit of quantitation for MeHg+ using the developed protocol was 0.5 µg Hg g−1. The stability of MeHg+ in the fish sample extracts was also assessed and losses of 14–16% were observed after storage of the extracts in a refrigerator at 5 °C, in high‐density polypropylene tubes, for 6 months. The developed protocol has been used previously with atmospheric pressure ionization mass spectrometry (API‐MS) to provide structural characterization and also with calibration via isotope dilution (IDMS) to provide high accuracy quantitation. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Use of constructed wetlands with four different experimental designs to assess the potential for methyl and total Hg outputs

This study used 10 parallel, smallscale constructed wetlands to investigate the potential for methylmercury (MeHg) production and water quality improvement using water and sediment from a creek that is a significant source of non-point nutrient, sediment and Hg pollution to a pristine river. The 4 replicated experimental designs utilized: (1) creek or Hg-contaminated water (25–320 ng Hg L −1) and creek or Hg-contaminated sediment (0.86 ± 0.52 μg Hg g −1) (MW-MS), (2) Hg contaminated water and clean sediment (0.09 ± 0.03 μg Hg g −1) (MW-CS), (3) clean water (effluent from a wastewater treatment plant; 4–16 ng Hg L −1) and Hg contaminated sediment (CW-MS), and (4) clean water and clean sediment (CW-CS). All designs functioned as sinks for N, P, sediment, and total Hg (THg). However, designs receiving clean water as the influent exhibited the least removal. Seasonal variations in net MeHg output were observed for designs with MW-MS and CW-MS, with concentrations peaking during warmer months. Designs with CS did not exhibit clear seasonal trends. Wetlands with CW and MS were the greatest MeHg sources. This was probably due to the fact that the treated wastewater had greater SO 4 2 - and total organic C (TOC) concentrations, lower pH, and, in general, higher temperatures than the creek water, and to the greater pool of Hg available in the Hg contaminated sediment, all of which could lead to enhanced Hg methylation. Temperature and SO 4 2 - correlated best with MeHg output in all designs. Although data from these small systems cannot be scaled up to predict the response in larger wetlands, results indicated that the benefits of a wetland, such as nutrient, suspended solids and THg removal, should be considered together with the risk of MeHg production.