Cold Vapor Atomic Fluorescence Spectrometry Research Articles

Determination of trace mercury in environmental samples by cold vapor atomic fluorescence spectrometry after cloud point extraction

A sensitive method is presented for the determination of ultra-trace levels of mercury using cold vapor atomic fluorescence spectrometry along with cloud point extraction. Preconcentration is based on the complexation of Hg(II) by dithizone, followed by micelle-mediated extraction of the complex using the surfactant Triton X-114. Foaming, which is always observed when generating vapor mercury in the presence of surfactant, was strongly reduced by using SnCl2 as a reducing reagent, and a homemade gas–liquid separator. Variables that affect the assay were optimized. These included pH value, concentration of chelating reagent, concentration of Triton X-114, equilibration temperature and time. The preconcentration of a 45-mL sample gave an enhancement factor of 29. The calibration graph is linear in the range from 0.05 to 5.0 ng mL−1 with a correlation coefficient of 0.9991. The limit of detection (3δ) obtained under the optimal conditions is 5 pg mL−1. The relative standard deviation for seven replicate determinations at 0.5 ng mL−1 level is 5.2%. The method was successfully applied to the determination of Hg in real samples.

Total and inorganic mercury determination in fish tissue by flow injection cold vapour atomic fluorescence spectrometry

A simple and reliable method for Hg determination in fish samples has been developed. Lyophilised fish tissue samples were extracted in a 25% (w/v) tetramethylammonium hydroxide (TMAH) solution; the extracts were then analysed by FI-CVAFS. This method can be used to determine total and inorganic Hg, using the same FI manifold. For total Hg determination, a 0.1% (w/v) KMnO4 solution was added to the FI manifold at the sample zone, followed by the addition of a 0.5% (w/v) SnCl2 solution, whereas inorganic Hg was determined by adding a 0.1% (w/v) L-cysteine solution followed by a 1.0% (w/v) SnCl2 solution to the FI system. The organic fraction was determined as the difference between total and inorganic Hg. Sample preparation, reagent consumption and parameters that can influence the FI-CVAFS performance were also evaluated. The limit of detection for this method is 3.7 ng g−1 for total Hg and 4.3 ng g−1 for inorganic Hg. The relative standard deviation for a 1.0 µg L−1 CH3Hg standard solution (n = 20) was 1.1%, and 1.3% for a 1.0 µg L–1 Hg2+ standard solution (n = 20). Accuracy was assessed by the analysis of Certified Reference Material (dogfish: DORM-2, NRCC). Recoveries of 99.1% for total Hg and 93.9% inorganic Hg were obtained. Mercury losses were not observed when sample solutions were re-analysed after a seven day period of storage at 4°C.

The Effect of Reducing Conditions and Temperature on Mercury Release from Coal

Coals contain small quantities of mercury that have the potential to be emitted to the atmosphere during thermal processing. While significant research effort has improved knowledge of mercury emissions from direct combustion of coal in power stations to produce electricity, much less effort has been devoted to mercury behavior from coal under reducing conditions, typical for smelting and metal processing. This article discusses laboratory investigations of mercury release from coal during heating under reducing conditions. Two coals, one of Australian and one of United States origin, were subjected to thermal treatment to temperatures ranging between 100 and 800°C. The level of mercury was monitored using cold-vapor atomic fluorescence spectrometry. The largest fraction of mercury was released at temperatures of up to 500°C, however some strongly bonded mercury was retained in coal samples even at temperatures of 600°C. Reducing atmospheric conditions revealed a likely delay to higher temperatures in the release of mercury from coal. Speciation of mercury in coal was further determined with a six-stage sequential selective extraction method. Mercury reaction mechanisms occurring during the heating of coal under both reducing and oxidizing conditions relevant to direct ironmaking processes are discussed.

A sensitive and selective fluorescent sensor for the determination of mercury(II) based on a novel triazine-thione derivative

A sensor membrane based on the fluorescence enhancement of a novel triazine-thione derivative, 4-ethyl-5-hydroxy-5,6-di-pyridin-2-yl-4,5-dihydro-2H-[1,2,4]triazine-3-thione, was capable of determining mercury(II) with high selectivity over the range 5.0 × 10 −10 and 5.0 × 10 −5 mol L −1 with a limit of detection of 1.8 × 10 −10 mol L −1 (0.036 μg L −1). The sensor can be regenerated using 5% thiourea in 1.0 mol L −1 HCl solution. The sensor also displayed unique selectivity toward mercury(II) ion with respect to other common metal cations and was applied to the determination of mercury(II) in tap water and human hair samples. The accuracy of the results were comparable to those obtained by cold vapour atomic fluorescence spectrometry.

Assessment of the Level of Mercury Present in Soaps by the Use of Cold Vapour Atomic Fluorescence Spectrometric Analysis – A Gambian Case Study

Sixteen brands of soap were analysed for their total mercury content using cold vapour atomic fluorescence spectrometry. The aim was to find out if the soaps contained mercury and if so, what quantity. In addition, are the quantities acceptable for health purposes. Mercury was found to be present in some soaps which did not indicate it on their labels, as required by law. The amounts of mercury found in the soaps were generally low, and may not lead to any short term mercury-linked health problems. A very low limit of detection was obtained. Keywords: Mercury, The Gambia, Soaps, Indigenous industry, Fluorescence

Determination of mercury in rice by cold vapor atomic fluorescence spectrometry after microwave-assisted digestion

A cold vapor atomic fluorescence spectrometry method (CV-AFS) has been developed for the determination of Hg in rice samples at a few ng g −1 concentration level. The method is based on the previous digestion of samples in a microwave oven with HNO 3 and H 2O 2 followed by dilution with water containing KBr/KBrO 3 and hydroxylamine and reduction with SnCl 2 in HCl using external calibration. The matrix interferences and the effect of nitrogen oxide vapors have been evaluated and the method validated using a certified reference material. The limit of detection of the method was 0.9 ng g −1 with a recovery percentage of 95 ± 4% at an added concentration of 5 ng g −1. The concentration level of Hg found in 24 natural rice samples from different origin ranged between 1.3 and 7.8 ng g −1.

Aerosol trace metals, particle morphology and total gaseous mercury in the atmosphere of Oxford, UK

An investigation of atmospheric trace metals was conducted in Oxford, UK, a small city ∼60 miles northwest of London, in 2007 and 2008. Concentrations of Sr, Mo, Cd, Pb, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in aerosol were measured in bulk and size segregated samples. In addition, total gaseous mercury (TGM) concentrations were monitored semi-continuously by cold vapour-atomic fluorescence spectroscopy. Metal concentrations in Oxford were intermediate between previously reported levels of UK rural and urban areas for most metals studied and levels of Cd, Ni and Pb were within European guidelines. Metal concentrations appeared to be influenced by higher traffic volume on a timescale of hours. The influence of traffic on the aerosols was also suggested by the observation of carbonaceous particles via scanning electron microscopy (SEM). Air mass back trajectories suggest air masses arriving in Oxford from London and mainland Europe contained the highest metal concentrations. Aerosol samples collected over Bonfire Weekend, a period of intense firework use and lighting of bonfires in the UK, showed metal concentrations 6–46 times higher than at other times. Strontium, a tracer of firework release, was present at higher concentrations and showed a change in its size distribution from the coarse to fine mode over Bonfire Weekend. The presence of an abundance of spherical Sr particles was also confirmed in SEM images. The average TGM concentration in Oxford was 3.17 ng m −3 (st. dev. 1.59) with values recorded between 1.32 and 23.2 ng m −3. This is a higher average value than reported from nearby rural locations, although during periods when air was arriving from the west, similar concentrations to these rural areas were seen in Oxford. Comparison to meteorological data suggests that TGM in Oxford's air is highest when wind is arriving from the east/southeast. This may be due to emissions from London/mainland Europe with a possible contribution from emissions from a local crematorium situated 4 miles east of the sampling site. A diurnal pattern was also observed in the TGM data with a minimum concentration during the day when mercury may have been diluted by thermal mixing of the atmospheric boundary layer. Additionally, this diurnal pattern may reflect variations in a local source of TGM.

Cadmium, mercury, and lead in kidney cortex of living kidney donors: Impact of different exposure sources,

Most current knowledge on kidney concentrations of nephrotoxic metals like cadmium (Cd), mercury (Hg), or lead (Pb) comes from autopsy studies. Assessment of metal concentrations in kidney biopsies from living subjects can be combined with information about exposure sources like smoking, diet, and occupation supplied by the biopsied subjects themselves. To determine kidney concentrations of Cd, Hg, and Pb in living kidney donors, and assess associations with common exposure sources and background factors. Metal concentrations were determined in 109 living kidney donors aged 24-70 years (median 51), using inductively coupled plasma-mass spectrometry (Cd and Pb) and cold vapor atomic fluorescence spectrometry (Hg). Smoking habits, occupation, dental amalgam, fish consumption, and iron stores were evaluated. The median kidney concentrations were 12.9microg/g (wet weight) for cadmium, 0.21microg/g for mercury, and 0.08microg/g for lead. Kidney Cd increased by 3.9microg/g for a 10 year increase in age, and by 3.7microg/g for an extra 10 pack-years of smoking. Levels in non-smokers were similar to those found in the 1970s. Low iron stores (low serum ferritin) in women increased kidney Cd by 4.5microg/g. Kidney Hg increased by 6% for every additional amalgam surface, but was not associated with fish consumption. Lead was unaffected by the background factors surveyed. In Sweden, kidney Cd levels have decreased due to less smoking, while the impact of diet seems unchanged. Dental amalgam is the main determinant of kidney Hg. Kidney Pb levels are very low due to decreased exposure.

Contaminant profiles in Southeast Asian immigrants consuming fish from polluted waters in northeastern Wisconsin

Recent immigrants to the USA from Southeast Asia may be at higher risk of exposure to fish-borne contaminants including polychlorinated biphenyls (PCBs), p, p'-dichlorodiphenyldichloroethene (DDE) and methylmercury (MeHg) because of their propensity to engage in subsistence fishing. Exposure to contaminants was assessed in men and women of Hmong descent living in Green Bay, Wisconsin, where the Fox River and lower Green Bay are contaminated with PCBs, and to a lesser extent with mercury. Serum samples from 142 people were analyzed for PCBs and p,p'-DDE by capillary column gas chromatography with electron capture detection (ECD). Whole blood was analyzed for total mercury by cold vapor atomic absorption spectrometry and atomic fluorescence spectroscopy. Lipid-adjusted total PCB concentrations ranged from 8.7 to 3,091ng/g (full range of the data), with a geometric mean of 183.6ng/g (estimated after eliminating one outlier). DDE ranged from 0.3 to 7,083 (full range of the data) with a geometric mean of 449.8ng/g (estimated after eliminating two outliers). Men had higher PCB and DDE concentrations than women. Serum PCB concentrations were significantly correlated with fish consumption (r=0.43, p<0.0001), whereas DDE concentrations were not (r=0.09,p=0.29). Instead, serum DDE was strongly associated with the number of years spent in a Thai refugee camp before immigrating to the USA (r=0.60;p<0.0001). PCB congeners 138, 153, 118 and 180 accounted for a smaller percentage of the total PCBs than has been reported in other fish-eating populations, and several lightly chlorinated congeners were present in relatively large amounts. Mercury exposure was low in this population. In conclusion, Hmong immigrants in northeastern Wisconsin are at risk of elevated PCB exposure from consumption of locally caught fish. The pattern of exposure is somewhat different than patterns in other fish-eating populations, possibly due to use of Aroclor 1242 by the paper industry in this region.

MERCURY ANALYSIS AND CONCENTRATION IN SEAWATER OF SOUTHERN SUMBAWA

Abstract. Current concerns over the negative impacts of Hg in the environment have led to the rapid progress of studies in this area. This progress has been directed to obtain analysis techniques that are able to accurately quantify Mercury (Hg) at extremely low concentration in which it frequently occurs. As part of a study on the environmental aspects of deep-sea submarine tailing placement at the Batu Hijau Mine, Sumbawa, this paper discusses recent progress in Hg analytical techniques, followed by the application of several techniques to investigate Hg concentration in seawater in the vicinity of the tailing discharge location. Using cold vapour atomic fluorescence spectrometry, dissolved Hg was found to be at sub-ng/l (ppt) levels. No dissolved Hg signal associated with the tailing discharge was found with concentrations being similar to adjacent coastal waters. Key words: tailing, STP system, Hg, analysis, and marine water

Mercury wet deposition and coal-fired power station contributions: An Australian study

Regions that have large coal-fired power station regions may be prone to elevated mercury (Hg) deposition fluxes. Total mercury (THg) in daily rainfall samples at a near-field sampling site (Hunter Valley) and a far-field station (Sydney) has been monitored in this study employing ultra-clean sampling techniques and Cold Vapour Atomic Fluorescence Spectrometry (CVAFS) analysis. Measurements of THg range from 0.9 to 16.5 and from 1.2 to 18.9 ng/L for the far-field and near-field sites respectively. Average daily THg wet deposition fluxes were 49.9 and 79.8 ng/m 2 for the far and near-field sites respectively. A two-sample t-test reveals the near-field site to have higher rainfall mercury (significant at the 95% level) and deposition fluxes. At the far-field site, lower Hg deposition occurs during the cooler months, while the Hunter Valley site has higher winter deposition. It is believed that the higher winter values near-field may be due to the combined impact of prevailing wind direction and high pollutant build up brought on by lower mixing height. Based on this study, the first in the Southern Hemisphere, we conclude that rainfall THg concentrations and Hg wet deposition fluxes at the two sites are comparable to rural sites in North America.

Determination of Trace Inorganic Mercury in Mineral Water by Flow Injection On-line Sorption Preconcentration-Cold Vapor Atomic Fluorescence Spectrometry

Abstract Flow injection on-line sorption preconcentration and separation in a knotted reactor (KR) was coupled to cold vapor atomic fluorescence spectrometry for the determination of trace mercury in mineral water. Mercury was preconcentrated by on-line formation of mercury diethyldithiocarbamate complex (Hg-DDTC) and absorption of the resulting neutral complex on the inner walls of a knotted reactor. A 20% (v/v) HNO 3 solution heated by Electromagnetic induction heating technique was used as eluent to remove the absorbed Hg-DDTC from the KR, and then the vapor mercury generated by mixing the resulting solution and KBH 4 was determined on-line by cold vapor atomic fluorescence spectrometry. The 20% HNO 3 was used as both the efficient eluent and the required acidic medium for subsequent mercury vapor generation. Using 20% HNO 3 instead of conventional organic solvent as eluent, the proposed method is simple, easy operational and environmental friendly. Under the optimal experimental conditions, the sample throughput was approximately 30 per hour with the enhancement factor of 35. The detection limit of mercury was 2.0 ng l −1 . The precision (RSD, n = 11) was 2.2% at the 0.1 μg l −1 Hg 2+ level.

Preconcentration techniques for the determination of mercury species in natural waters

Monitoring mercury (Hg) species in the hydrosphere is very important due to their impact on environmental and human health and their extremely high bioaccumulation factors (up to 10 6) in the marine food chain. In natural waters, Hg concentrations are typically in the low-ng/L range, which makes their reliable determination a major analytical challenge. Sophisticated detection techniques, such as cold vapor-atomic fluorescence spectrometry can provide the necessary limits of detection (LODs) with reasonable precision but accurate determinations also require robust procedures for sampling and sample storage. Contaminants from stabilizing reagents, storage vessels and the ambient environment are likely due to the ubiquity of Hg, and analyte loss can occur due to high volatility and adsorption of Hg to surfaces. One strategy to overcome problems with sample stability is to use in situ solid-phase preconcentration methods to decrease LODs and stabilize samples at the point of collection (e.g., on board ship) and during transport and storage. This article discusses the various solid-phase pre-concentration strategies available for Hg species from natural waters and makes recommendations for the most appropriate in situ methods.

Analysis of Bio‐Obtainable Endocrine Disrupting Metals in River Water and Sediment, Sewage Influent/Effluent, Sludge, Leachate, and Concentrated Leachate, in the Irish Midlands Shannon Catchment

The application of an acid digestion and subsequent solid-phase extraction (SPE) procedure were implemented as preliminary treatments prior to quantifying the levels of potentially endocrine disrupting metals (EDMs) in a variety of solid and liquid matrices. These included (solid) river sediment, leachate sediment and sewage sludge and also (liquid) river water, landfill leachate, concentrated leachate, sewage influent, and sewage effluent, sampled in the Irish Midlands. The total concentrations of cobalt (Co), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and manganese (Mn), after extraction and preconcentration, were determined by atomic absorption spectroscopy (AAS). Mercury (Hg) in sediment and sludge was determined using cold-vapour atomic fluorescence spectroscopy (AFS). For sewage sludge maximum values (mg/kgdw) of 4700 Ni, 1642 Mn, 100.0 Cd, 3400 Zn, 36.70 Co, 750.0 Pb, 485.8 Cr, and 1003 Cu were determined whilst in leachate sediment, maximum values (mg/kgdw) of 32.10 Ni, 815.0 Mn, 32.78 Cd, 230.3 Zn, 26.73 Co, 3525 Pb, 124.9 Cr, and 50.13 Cu were found. Over several months, the data showed elevated levels in sewage influents, effluents, and sludges compared to a battery of adjacent river water samples and corresponding sediments. There was a definite trend for target values for sediments to be exceeded, while intervention values were only exceeded for cadmium. Overall the pattern in terms of concentration was sewage > leachate > river matrices. A nonparametric assessment of the effect of sewage treatment method on median metal levels in sludge revealed statistically significant differences at the 95% level of confidence for Co, Cr, and Hg and at the 90% level of confidence for Cd.

Effects of mercury on soil microbial communities in tropical soils of French Guyana

In gold mining regions, the risk of soil pollution by mercury is a major environmental hazard, especially in tropical areas where soil microflora plays a major part in soil functioning, major bio-geochemical cycles and carbon turn-over. The impact of mercury pollution on soil microflora should thus be carefully assessed in such environments while taking into consideration the specificities of tropical soils. The aim of this study was to compare the effects of mercury (0, 1 and 20 μg of inorganic mercury per gram of soil) on the functional diversity and genetic structure of microbial communities in a tropical soil. We investigated the effects of mercury on tropical soil microflora using soil microcosms spiked with mercury and incubated at 28 °C for 1 month. Microcosm flora, its biomass and its activity, as well as its functional and genetic structure, were followed by cultural methods, measures of respiration, ECOLOG plates, and DGGE (denaturing gel gradient electrophoresis), respectively. Fate of total and bioavailable mercury was estimated by CVAFS (cold vapor atomic fluorescence spectrometry). Results obtained for the microcosms enriched with only 1 μg g −1 mercury were indistinguishable from controls. Conversely, in the presence of high mercury contents (20 μg g (1), an immediate effect was measured on soil respiration, functional diversity (ECOLOG plates) and genetic structure (DGGE), although no significant effect was observed on plate counts or microbial biomass. In addition, whereas microbial activities (respiration and functional diversity) rapidly regained control values, a lasting effect of the high mercury concentration was observed on the genetic structure of the soil microbial community. These modifications took place during the first week of incubation when total mercury concentration was declining and bioavailable mercury was at its highest. This multiple approach study is one of the first attempts at investigating the effects of mercury on soil microbial communities in tropical soils. Our results demonstrate that in the tropical soil under study, mercury affects the soil microbial communities in a different manner than was previously reported in temperate soils. Furthermore, mercury toxicity on soil microbes may be modulated by typical tropical soil characteristics.

Gaseous Mercury Release during Steam Curing of Aerated Concretes That Contain Fly Ash and Activated Carbon Sorbent

Gaseous mercury released from aerated concrete during both presteam curing at 25 °C and steam curing at 80 °C was measured in controlled laboratory experiments. Mercury release originated from two major components in the concrete mixture: (1) class F coal fly ash and (2) a mixture of the fly ash and powdered activated carbon onto which elemental mercury was adsorbed. Mercury emitted during each curing cycle was collected on iodated carbon traps in a purge-and-trap arrangement and subsequently measured by cold-vapor atomic fluorescence spectrometry. Through 3 h of presteam curing, the release of mercury from the freshly prepared mixture was less than 0.03 ng/kg of concrete. Releases of total mercury over the 21 h steam curing process ranged from 0.4 to 5.8 ng of mercury/kg of concrete and depended upon mercury concentrations in the concrete. The steam-cured concrete had a higher mercury release rate (ng kg−1 h−1) compared to air-cured concrete containing fly ash, but the shorter curing interval resulted in less total release of mercury from the steam-cured concrete. The mercury flux from exposed concrete surfaces to mercury-free air ranged from 0.77 to 11.1 ng m−2 h−1, which was similar to mercury fluxes for natural soils to ambient air of 4.2 ng m−2 h−1 reported by others. Less than 0.022% of the total quantity of mercury present from all mercury sources in the concrete was released during the curing process, and therefore, nearly all of the mercury was retained in the concrete.

A preliminary study of the Hg flux from selected Ohio watersheds to Lake Erie

Abstract New measurements of riverine dissolved and particulate Hg fluxes into Lake Erie from 12 northern Ohio watersheds have been determined from samples collected in April 2002 and analyzed using ultra-clean techniques with cold-vapor atomic fluorescence spectrometry. Total Hg concentrations ranged through 2.5–18.5 ng L −1 , with a mean of 10.4 ng L −1 with most Hg in particulate form. Dissolved Hg concentrations ranged through 0.8–4.3 ng L −1 , with a mean of 2.5 ng L −1 . Highest total Hg concentrations were observed in western rivers with primarily agricultural land use and eastern rivers with mixed land use in their watersheds. Total suspended solid concentrations ranged through 10–180 mg L −1 with particulate Hg concentrations ranging through 47–170 ng g −1 , with a mean of 99 ng g −1 . Particulate Hg was similar to published data for central Lake Erie bottom sediments but much lower than for bottom sediments in western Lake Erie. Total Hg concentrations were positively correlated with suspended sediment concentrations and negatively with dissolved N O 3 - concentrations. The total estimated annual Hg fluxes from these rivers into Lake Erie is estimated to be 85 kg, but because only one event was sampled during high flow conditions, this may be an overestimate. This is much lower than previous published estimates of riverine Hg input into Lake Erie.

High-Fish Consumption and Risk Prevention: Assessment of Exposure to Methylmercury in Portugal

The aim of this study was to evaluate the exposure to methylmercury (MeHg) of potential populations at risk living in Portugal. To ascertain youth exposure, a questionnaire was distributed to 300 students of a middle secondary school in Sesimbra and to 429 students studying in Caneças, selected as the control population. The average number of fish meals consumed by person was 4.1 and 3 per week in Sesimbra and Caneças, respectively. The subpopulations of high intake (PHI) corresponding to those ingesting 7 or more fish meals per week were also analyzed separately, with 17% of the students belonging to the PHI of Sesimbra versus 6.1% in Caneças. Socioeconomic aspects such as relative's professional involvement with fisheries correlated with the higher intakes in Sesimbra. Fish samples were collected in the dock of Sesimbra and total mercury (Hg) was determined by flow injection cold vapor atomic fluorescence spectroscopy (FI-CV-AFS). The mean value found for nonpredators was 0.035 μg/g. Dogfish specimens surpassed the legislated limit for predator species and increased the predators mean to 1 μg/g. The cross-sectional data were integrated with the fish analysis results to estimate the population exposure to MeHg. The indices of risk calculated for youth reached values of 4.5, demonstrating the existence of risk to a part of the population exceeding the provisional tolerable weekly intake (PTWI) level mandated by WHO (1.6 μg/kg bw). The results indicate that monitoring of Hg levels in fish is mandatory and counseling should be provided to populations at risk, encouraging them to prevent the risk.

Automated Simultaneous Analysis of Monomethyl and Mercuric Hg in Biotic Samples by Hg-Thiourea Complex Liquid Chromatography Following Acidic Thiourea Leaching

A simple leaching procedure has been validated for quantitative isolation of both monomethyl (CH3Hg+) and inorganic (Hg(II)) mercuryfrom fresh or dried biotic tissue for simultaneous analysis via separation and quantification with Hg-thiourea complex liquid chromatography cold vapor atomic fluorescence spectrometry (HgTU/LC-CVAFS). The leaching solution comprises thiourea, hydrochloric acid, and glacial acetic acid and works by protonating thiol binding sites and forming water-soluble cationic CH3HgS=C(NH2)2+ and Hg[S=C(NH2)2]2(2+) complexes, which are easily separated from the solid matrix. The isolated complexes are preconcentrated online by either thiol resin trapping or a new iodide-complex polydivinylbenzene resin trapping (I-PDVB). The I-PDVB trapping involves only one reagent addition, requires no pH adjustments, and is quantitative over a large range of volumes and flow rates. The chromatography system can use either ion chromatography or a new ion-pairing reversed phase separation coupled to cold vapor generation and atomic fluorescence detection. The system allows quantitative sample introduction and yields absolute detection limits of 0.4 pg and 0.7 pg, for CH3Hg+ and Hg(II) respectively, enabling relative detection limits as low as 4 and 7 pg g(-1) with 100 mg samples, and yields % CV routinely less than 5% with well homogenized samples. Accuracy for both forms of mercury has been validated with multiple biotic reference materials and by comparison of the sum of CH3Hg+ and Hg(II) with total Hg on a variety of different biotic sample types (n = 49). The system can be calibrated with either aqueous standards or leached reference materials.

Distribution and wet deposition fluxes of total and methyl mercury in Wujiang River Basin, Guizhou, China

Guizhou is one of the most seriously contaminated regions with mercury in China, but mercury deposition fluxes in this region have not been well studied. Concentrations and wet deposition fluxes of total mercury (THg) and methyl mercury (MeHg) were measured from January to December 2006 at 5 sites in Wujiang River Basin, Guizhou, China. Monthly-integrated samples were collected using bulk precipitation samplers. Samples were treated rigorously according to our trace metal protocol, and THg was analyzed by cold vapor atomic fluorescence spectrometry (CVAFS) and MeHg by aqueous phase ethylation, GC separation, and CVAFS detection. The annual volume-weighted mean concentration and wet deposition fluxes of THg and MeHg for 5 sites were 36.0 ng L −1 and 34.7 μg m −2 yr −1, and 0.19 ng L −1 and 0.18 μg m −2 yr −1 in 2006, respectively. The proportion of MeHg to THg ranged from 0.2% to 2.3%, with the mean value of 0.7%. The results also showed that each site had a similar seasonal trend for mercury concentration and wet deposition flux. The largest wet deposition fluxes of THg and MeHg occurred during the rainy season (May–October) when the rainfall was greater, whereas the highest concentrations of THg and MeHg appeared during winter months (December–February). The monthly concentrations of THg and MeHg negatively correlated well with the monthly precipitation depth ( r 2 = 0.17 and 0.12), suggesting that scavenging of particle-bound mercury from the atmospheric is an important mechanism contribution to mercury in rain.