Mercury In Surface Waters Research Articles

Anthropogenic and Geogenic Mercury in Surface Waters in the Mature Bathurst Mining Camp, New Brunswick, Canada

Abstract Interactions between a cyanide leach used for Au extraction and cinnabar-bearing gossan tailings at the Murray Brook mine have led to the development of an Hg-enriched contaminated groundwater plume that discharges to the nearby Gossan Creek. Naturally occurring cinnabar in the area poses a challenge in distinguishing mining-related contamination from background Hg concentrations. Surface water data from throughout the Bathurst Mining Camp was used to establish interelement relationships compared to pH and the spatial distributions of Hg, SO42−, Cl, Cu, NO3−, Zn, Pb, and Ca/HCO3− values. Statistical significance of anomalous measurements was evaluated to assess geogenic versus anthropogenic contributions of mining associated elements. Watershed analysis indicated that the Murray Brook tailings facility may sit on a basinal divide with potential for tailings leachate-impacted groundwater and surface water migration toward the northeast as well as northwest toward Gossan Creek. Elevated NO3− was detected in two streams south-west of Gossan Creek alongside greater than normal Hg concentrations. Other locations in the study area away from the Murray Brook area show little geochemical evidence for impact of mining on surface waters despite Hg concentrations as high as 0.019 µg L-1. Points with geogenic Hg concentration on the order of 0.01 µg L-1 were observed throughout the study area, particularly in the Upsalquitch River tributaries south-west of Gossan Creek and in the surface waterbodies west of the Restigouche deposit, indicating weathering of cinnabar-bearing gossan.

The role of plastic debris in the biogeochemical cycle of mercury in Lake Erie and San Francisco Bay

The accumulation of plastic debris that concentrates hydrophobic compounds and microbial communities creates the potential for altered aquatic biogeochemical cycles. This study investigated the role of plastic debris in the biogeochemical cycling of mercury in surface waters of the San Francisco Bay, Sacramento River, Lake Erie, and in coastal seawater. Total mercury and monomethylmercury were measured on plastic debris from all study sites. Plastic-bound microbial communities from Lake Erie and San Francisco Bay contained several lineages of known mercury methylating microbes, however the hgcAB gene cluster was not detected using polymerase chain reaction. These plastic-bound microbial communities also contained species that possess the mer operon, and merA genes were detected using polymerase chain reaction. In coastal seawater incubations, rapid mercury methylation percentages were greater in the presence of microplastics and demethylation percentages decreased as monomethylmercury additions adsorbed to microplastics. These findings suggest that plastic pollution has the potential to alter the biogeochemical cycling of mercury in aquatic ecosystems.

Mercury Determination Using Stannous Chloride Reductant Followed by Atomic Absorption Spectrometric Measurement: Performance Characteristics, Uncertainty Estimation, and Compliance Assessment

Indonesian government has committed to reduce and eliminate mercury. Hence, the intensity of monitoring activities of mercury levels in various matrices would be increased and supported by qualified analytical data. Key characteristic performances, i.e., the limit of detection, linear range, precision, trueness, have been successfully carried out, and the method was shown to fit the purpose. The limit detection, LoD and LoQ, were found to be 0.26 and 0.86 µg/L, respectively, which were adequate to reach the tightest regulatory limit of mercury in surface water (1 µg/L). The examined linearity range of 1-20 µg/L has been found sufficient for its application since a high mercury concentration in the typical sample is seldomly expected. Precision and trueness aspects of the method were shown to have satisfaction performance, with CV of 1,24% and recovery of 104.54%. All the possible uncertainty sources have been identified in this study. Since no reference material was available, the uncertainty of bias was evaluated through the recovery of the spiked sample. Compliance assessment to six measurement results has been performed; one result was below LoQ, four were clearly below regulatory limit, and one was questionable. Hence a decision rule was applied.

National action plan for the reduction and abolishment of mercury use: regulation implementation in 2019-2020

As a continuation of the enactment of Law No 11 of 2017 concerning Ratification of the Minamata Convention on Mercury, the Government of Indonesia issued Presidential Regulation No. 21 of 2019 concerning the National Action Plan (NAP) for the Reduction and Abolishment of Mercury (RAM). This regulation contains strategies, activities, and targets for mercury reduction and elimination in the period 2018 to 2030, with priorities in manufacturing, energy, small-scale gold mining, and health. This study aims to analyze the success indicators of the NAP-RAM in 4 priority areas based on the regulations implemented in 2019-2020. The analysis results show that not all regulations that are targeted in 2019 and 2020 have been formed. On the other hand, some existing regulations still require adjustments and improvements. Mercury was found in surface water in several provinces in Indonesia due to artisanal and small-scale gold mining (ASGM) existence. The maximum value of mercury in surface waters was still below the quality threshold standard proposed by Government Act No. 82/2001 but exceeded the WHO’s quality threshold standard. The mercury waste threshold in the Indonesian regulation is higher than those in international regulation such as USEPA (the United States Environmental Protection Agency) or WHO (World Health Organization). Therefore, the government should issue a stricter regulation closer to international regulation regarding the mercury waste threshold in water.

Determination of Mercury Content in Surface Waters Using an Environmentally Non-Toxic Terminating Electrolyte

The paper presents results of the research on the dynamics of changes in the concentration of mercury in surface waters. The importance of mercury as an environmental pollutant results from specific properties of this metal, many sources of contamination, volatility, mobility, stability and high toxicity of its specific chemical forms. Samples of surface water collected from three rivers: the Bug, the Liwiec and the Muchawka were analysed. The Muchawka River flows into the Liwiec River, which in turn is a tributary of the Bug River. The technique of isotachophoresis was employed, using a solution of a biodegradable and environmentally non-toxic derivative of electrostatically stabilised silanates as the terminating electrolyte. The highest average mercury concentration of 0.89 μg/dm3 was determined in water samples collected from the Bug River in January, whereas the lowest concentration of 0.42 μg/dm3 was recorded in water collected from the Muchawka River in September.

Mercury bioaccumulation in stream fish from an agriculturally-dominated watershed

Bioaccumulation of mercury in freshwater fish is a complex process driven by environmental and biological factors. In this study, we assessed mercury in fish from four tributaries to the Red Deer River, Alberta, Canada, which are characterized by high surface water mercury concentrations. We used carbon (δ13C) and nitrogen (δ15N) stable isotopes to examine relationships between fish total mercury (THg) concentrations, food web dynamics and patterns in unfiltered THg and methylmercury (MeHg) concentrations. We found that THg concentrations exceeded the tissue residue quality guideline for the protection of wildlife consumers in 99.7% of fish sampled. However, while the surface water THg concentration was highest in Michichi Creek and the MeHg concentration was consistent across streams, patterns of fish THg concentrations varied depending on species. Furthermore, body size and trophic level were only correlated with THg concentrations in white sucker (Catostomus commersoni) and Prussian carp (Carrasius gibelio). The results of this study suggest that mercury poses a risk to the health of piscivorous wildlife in the Red Deer River watershed. Despite high THg concentrations in these streams, mercury bioaccumulation is not driven by environmental inorganic mercury concentrations. Additionally, commonly cited factors associated with mercury concentrations in fish, such as body size and trophic level, may not strongly influence bioaccumulation in these stream ecosystems.

High-resolution measurements of elemental mercury in surface water for an improved quantitative understanding of the Baltic Sea as a source of atmospheric mercury

Abstract. Marginal seas are directly subjected to anthropogenic and natural influences from land in addition to receiving inputs from the atmosphere and open ocean. Together these lead to pronounced gradients and strong dynamic changes. However, in the case of mercury emissions from these seas, estimates often fail to adequately account for the spatial and temporal variability of the elemental mercury concentration in surface water (Hg0wat). In this study, a method to measure Hg0wat at high resolution was devised and subsequently validated. The better-resolved Hg0wat dataset, consisting of about one measurement per nautical mile, yielded insight into the sea's small-scale variability and thus improved the quantification of the sea's Hg0 emission. This is important because global marine Hg0 emissions constitute a major source of atmospheric mercury. Research campaigns in the Baltic Sea were carried out between 2011 and 2015 during which Hg0 both in surface water and in ambient air were measured. For the former, two types of equilibrators were used. A membrane equilibrator enabled continuous equilibration and a bottle equilibrator assured that equilibrium was reached for validation. The measurements were combined with data obtained in the Baltic Sea in 2006 from a bottle equilibrator only. The Hg0 sea–air flux was newly calculated with the combined dataset based on current knowledge of the Hg0 Schmidt number, Henry's law constant, and a widely used gas exchange transfer velocity parameterization. By using a newly developed pump–CTD with increased pumping capability in the Hg0 equilibrator measurements, Hg0wat could also be characterized in deeper water layers. A process study carried out near the Swedish island Øland in August 2015 showed that the upwelling of Hg0-depleted water contributed to Hg0 emissions of the Baltic Sea. However, a delay of a few days after contact between the upwelled water and light was apparently necessary before the biotic and abiotic transformations of ionic to volatile Hg0 produced a distinct sea–air Hg0 concentration gradient. This study clearly showed spatial, seasonal, and interannual variability in the Hg0 sea–air flux of the Baltic Sea. The average annual Hg0 emission was 0.90 ± 0.18 Mg for the Baltic proper and extrapolated to 1.73 ± 0.32 Mg for the entire Baltic Sea, which is about half the amount entrained by atmospheric deposition. A comparison of our results with the Hg0 sea–air fluxes determined in the Mediterranean Sea and in marginal seas in East Asia were to some extent similar but they partly differed in terms of the deviations in the amount and seasonality of the flux.

Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

AbstractWe construct a rice paddy biogeochemical cycle model to investigate processes governing rice mercury sources and to understand factors influencing spatiotemporal variability in Chinese rice mercury concentrations. The rice paddy model takes atmospheric mercury deposition, simulated from a global atmospheric chemistry transport model (GEOS‐Chem), and soil and irrigable surface water mercury concentrations obtained from literature and calculates rice inorganic (IHg) and methylmercury (MeHg) concentrations. We use ranges of GEOS‐Chem‐simulated future atmospheric mercury deposition—no policy and strict policy to regulate mercury emissions from Chinese coal‐fired power plants under the Minamata Convention on Mercury—to simulate future rice IHg and MeHg concentrations. Sensitivity analyses suggest that rice IHg and MeHg concentrations are more sensitive to the process of soil desorption than infiltration of recently introduced mercury (atmospheric and irrigation source). The rate of internal methylation via microbial activity has the largest modeled influence on rice MeHg concentration. We find that soil mercury, rather than atmospheric deposition, explains observed spatial variability in rice IHg and MeHg concentrations and captures locations of rice mercury hot spots (>20 ng/g; China National Standard Limit). Under our future scenarios, the Chinese median rice IHg and MeHg concentration increases by 13% and decrease by 18% under no policy and strict policy, respectively. Regions with the largest percentage decline in rice IHg and MeHg concentrations under strict policy are in central China, which have high rice mercury concentrations, rice production, and consumption. Our study suggests that addressing Chinese rice mercury contamination requires attention to contaminated soil and regulation of anthropogenic mercury emissions.

Directly-thiolated graphene based organic solvent-free cloud point extraction-like method for enrichment and speciation of mercury by HPLC-ICP-MS

Directly-thiolated graphene (G-SH) was prepared by substitution of the epoxy and hydroxyl groups with mercapto on the bulk and edge of the graphene oxide. Cloud point extraction-like method (CPEL) was established for enrichment of divalent mercury (IHg) and monomethylmercury (MMHg) in the water samples, based on the prepared G-SH, with good hydrophilicity, strong affinity towards mercury species and huge surface area. The large amount of active adsorption sites, thiol groups, on the bulk and edge of the surface of the G-SH play a key role in extraction of mercury species. Under the optimal conditions, the enrichment factors were 78 and 77 based on only 40mL samples, the detection limits (3δ) by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) were 3.8 and 1.3ngL−1 for IHg and MMHg with good recoveries, respectively. The proposed CPEL-HPLC-ICP-MS method was successfully applied for speciation of mercury in surface water, underground water, domestic sewage and even sea water; moreover, the results suggested that it is a simple, sensitive and environment-friendly technique for speciation of mercury at trace levels.

Is Mercury in a Remote Forested Watershed of the Adirondack Mountains Responding to Recent Decreases in Emissions?

Although there has been a decline in U.S. mercury emissions, the effects of this change on remote ecosystems are not well understood. We examine decadal (2004-2015) responses of atmospheric mercury deposition, along with total mercury (THg) and methylmercury (MeHg) concentrations and fluxes, to decrease in mercury emissions at Arbutus Lake-watershed in the remote forested Adirondack region of New York, a biological mercury hotspot. Although wet mercury deposition remains constant, THg deposition has decreased through decreases in litter mercury inputs (17.9 to 10.8 μg/m2-yr) apparently driven by decreases in atmospheric concentrations of gaseous elemental mercury (Hgo). While the lake is a net sink for THg and MeHg, concentrations and fluxes of THg and MeHg have decreased in the inlet stream and lake water apparently in response to decreases in Hgo deposition. Decreases in surface water mercury have occurred despite decadal increases in concentrations of dissolved organic carbon. Moreover, the fraction of THg as MeHg at the inlet has not changed despite decadal decreases in atmospheric sulfate deposition and surface water concentrations of sulfate. Our results indicate that recent decreases in U.S. mercury emissions have resulted in decreases in litter mercury deposition, and stream and lake THg and MeHg concentrations and fluxes, suggesting the first steps toward ecosystem recovery.

Mercury Distribution in the Deûle River (Northern France) Measured by the Diffusive Gradients in Thin Films Technique and Conventional Methods.

The distribution of mercury in surface water and in sediment from Deûle River in Northern France was studied by application of conventional sampling methods and by diffusive gradients in thin films technique (DGT). Concentration of total dissolved mercury in surface water was 20.8 ± 0.8 ng l(-1). The particulate mercury concentration was 6.2 ± 0.6 µg g(-1). The particulate mercury was accumulated in sediment (9.9 ± 2.3 mg kg(-1)), and it was transformed by methylating bacteria to methylmercury, mainly in the first 2-cm layer of the sediment. Total dissolved concentration of mercury in sediment pore water obtained by application of centrifugation extraction was 17.6 ± 4.1 ng l(-1), and it was comparable with total dissolved pore water mercury concentration measured by DGT probe containing Duolite GT-73 resin gel (18.2 ± 4.3 ng l(-1)), taking the sediment heterogeneity and different principles of the applied methods into account. By application of two DGT probes with different resin gels specific for mercury, it was found that approximately 30% of total dissolved mercury in sediment pore water was present in labile forms easy available for biota. The resolution of mercury DGT depth profiles was 0.5 cm, which allows, unlike conventional techniques, to study the connection of the geochemical cycle of mercury with geochemical cycles of iron and manganese.

Biogeochemical factors affecting the distribution, speciation, and transport of Hg species in the Deûle and Lys Rivers (Northern France).

The Deûle River is a highly polluted River by heavy metals caused by the historical discharges of ore minerals from the former ore smelter "Metaleurop." The potential mercury (Hg) pollution in the Deûle River implicates the importance of Hg distribution study in the river. As well as to configure the different biogeochemical factors that control the distribution and the potential transport of Hg to distant places. Four different sites were studied as follows: D-A (Deûle River, a site located upstream the river), D-B (Deûle River, a site located near a Zn, Pb, Cu, and Ni smelter that closed in 2003), L-C (Lys River, a site located upstream the confluence of the Deûle River with Lys River), and L-D (downstream the rivers confluence). Different Hg analyses were performed including total mercury in sediment (HgTS), methylmercury (MeHg) in sediment, total mercury in pore water (HgTPW), total mercury in surface water (HgTD), and total suspended particulate Hg in water (HgTP). HgTS decreases downstream from the Deûle River sites with a mean value of 11 ± 0.34 mg/kg to Lys River site (L-D) with a mean value of 0.53 ± 0.02 mg/kg at the confluence. The unaffected side of the Lys River, localized before the confluence (L-C), is characterized by low HgTS of an average value of 0.042 ± 0.003 mg/kg and high % MeHg reaching 4.2 %. Whereas, the highly contaminated Deûle sites are designated by low % MeHg with an average value of 0.053 %. Low pristine environments like that found in L-C site with more favorable biogeochemical conditions of lower concentrations of HgTS, sulfides, and Corg host more active biotic methylation than that of the highly polluted Deûle sites with high concentrations of HgTS and sulfides concentrations. Methylation in D-B (the closet site to Metaleurop smelter) is an old and recent methylation activity that has contributed to MeHg accumulation in the sediments as opposed to the exclusive recent events of methylation in Lys sites. MeHg in all sites is produced in situ rather than exported from other potential sources confirmed by significant relations of % MeHg with %Corg and AVS. Hg pollution is transported from the Deûle River to the Lys River (L-C and L-D) through suspended particles leached or remobilized from the River catchment. The dominance of reducing conditions in the Deûle River attributed to higher sulfide concentration has contributed to higher HgTPW than the Lys sites. Diffusive fluxes of HgT from sediment to water column for the Deûle and Lys River sites (L-C and L-D) were estimated to be 224, 53, and 2 ng/cm(2) year, respectively.

The source and fate of sediment and mercury in Hunza River basin, Northern Areas, Pakistan

This article presents results of mercury in surface waters from Hunza River basin, Northern Areas, Pakistan. Small-scale gold mining activities along the Hunza and Gilgit rivers are long known to be discharging mercury in the amalgamation and roasting processes. Previous studies reported high mercury concentrations in soils close to mining operations as well as serious health problems for miners. However, none of the studies have focused on the level of contamination in aqueous environments. This is the first study on the investigation of source and fate of sediment and river-borne mercury in the Hunza River. The samples collected near gold panning sites showed higher mercury concentrations than critical levels established by the U.S. Environmental Protection Agency. The observed dissolved mercury concentrations ranged from 5.10 to 25.25 ng/l, whereas particulate-bound mercury ranged from 4.85 to 154.62 ng/l. Particulate-phase mercury corresponded to more than 75% of the total observed mercury concentrations for all of the sampled rivers. Thus, suspended sediments represented the major pathway of the riverine mercury transport. A mass balance calculation suggested an annual mercury flux of 48.6 g/km2 into the Hunza River basin. The samples collected from the most affected river, the Shimsal River, averaged to have 108 ng/l total mercury. This amount was close to the average soil mercury data of 151 ng/l as reported by the Pakistan Mineral Development Corporation in 2001. The dominant source of contamination was shown to be the leaching of large quantities of mercury from the mercury-rich sediment and flood plain soil into the rivers, rather than the direct release from mining activities. Significant decrease in both dissolved and particulate-bound mercury concentration downstream of Attabad Lake suggested that mercury is being accumulated or consumed in the lake. Although minimization or elimination of mercury loses from the mining process seems important for the well-being of the miners, preventing the remobilization of accumulated mercury is equally important in mercury control in this region. Copyright © 2014 John Wiley & Sons, Ltd.

Submicron silica spheres decorated with silver nanoparticles as a new effective sorbent for inorganic mercury in surface waters

An analytical method using silica supported silver nanoparticles as a novel sorbent for the enrichment and determination of inorganic mercury (iHg) in surface water samples has been developed. Silver nanoparticles (AgNPs) were synthesized by a completely green procedure and were deposited onto the amine functionalized surface of silica submicrospheres (SiO2-NH2). The prepared nanocomposite material (SiO2/AgNPs) was characterized by transmission electron microscopy, UV-vis spectroscopy, X-ray diffraction and atomic force microscopy. The sorption and desorption characteristics of the nanosorbent SiO2/AgNPs toward Hg species were investigated by a batch method. An excellent separation of iHg and methylHg was achieved in 20 minutes at pH 2. The high selectivity of the SiO2/AgNPs toward iHg was explained by Hg(ii) reduction and subsequent silver-mercury amalgam formation. The analytical procedure for the enrichment and determination of inorganic mercury in surface waters was developed based on solid phase extraction and ICP-MS measurements. The total Hg content was determined after water sample mineralization. The recoveries reached for iHg in different surface waters e.g. river and Black sea water samples varied from 96-101%. The limits of quantification are 0.002 μg L(-1) and 0.004 μg L(-1) for iHg and total Hg, respectively; the relative standard deviations varied in the ranges of 5-9% and 6-11% for iHg and total Hg, respectively, for Hg content from 0.005 to 0.2 μg L(-1). The accuracy of the procedure developed for total Hg determination was confirmed by a comparative analysis of surface river (ICP-MS) and sea (CV AFS) waters.

Distribution and production of reactive mercury and dissolved gaseous mercury in surface waters and water/air mercury flux in reservoirs on Wujiang River, Southwest China

Transformation and distribution of mercury (Hg) species play an important role in the biogeochemical cycling of mercury in aquatic systems. Measurements of water/air exchange fluxes of Hg, reactive mercury (RHg), and dissolved gaseous mercury (DGM) concentrations were conducted at 14 sites in five reservoirs on the Wujiang River, Guizhou, Southwest China. Clear spatial and temporal variations in Hg fluxes, RHg, and DGM concentrations were observed in the study area. Hg fluxes and RHg concentrations exhibited a consistent diurnal variation in the study area, with maximum fluxes and concentrations during daytime. A typical diurnal trend of DGM with elevated concentration at night was observed in a eutrophic reservoir with elevated bacteria abundance, suggesting a bacteria‐induced production of DGM in this reservoir. For other reservoirs, a combination of sunlight‐stimulated production and loss via photo‐induced oxidation and evaporation regulated the diurnal trends of DGM. Seasonal variations with elevated Hg fluxes and RHg concentrations in warm season were noticeable in the study area, which highlighted the combined effect of interrelationships between Hg species in water and environmental parameters. Hg fluxes exhibited much more significant correlations with RHg and THg concentrations and air temperature compared to DGM concentrations and solar radiation. The measured fluxes were significantly higher than those simulated using the water/air thin film Hg0 gradient model. Aside from the potential limitations of dynamic flux chamber method, this may also suggest the thin film gas exchange model is not capable of predicting water/air Hg flux under low wind speed conditions. Additionally, it is speculated that DGM concentrations might vary significantly in surface waters with depth, and measurements of DGM at a depth of 2–4 cm below the water surface probably underestimated the DGM concentration that should be taken into account in simulations of water/air flux using the thin film gas exchange model. An empirical model of water/air Hg flux was developed, and the simulated fluxes were compared well with measurements. The model yields a mean annual Hg emission of 3.2 ± 1.0 kg in the study area.

Simultaneous preconcentration of copper and mercury in water samples by cloud point extraction and their determination by inductively coupled plasma atomic emission spectrometry

A cloud-point extraction process coupled to ICP-OES by using 3-nitro benzaldehyde thiosemicarbazone (3-NBT) as complexing agent was developed for the simultaneous preconcentration and determination of copper and mercury in water samples. The variables affecting the complexation and extraction steps were optimized. Under the optimum conditions (i.e. 1.5×10−5molL−1 ligand, 0.3% (v/v) Triton X-114, 55°C equilibrium temperature, incubation time of 30min) the calibration graphs were linear in the range of 5–120 and 10–100ngmL−1 with enhancement factor of 82.7 and 51.3 for Cu2+ and Hg2+, respectively. The preconcentration factors were 28.6 in both cases and detection limits were obtained 0.48 for Cu and 1.1ngmL−1 for Hg. The precisions (R.S.D.%) for five replicate determinations at 50ngmL−1 of copper and mercury were better than 1.8% and 3.2%, respectively. The accuracy of the proposed method is validated by analyzing a certified reference material of water (RTC-QCI-049) with satisfactory results. Finally, the proposed method was utilized successfully for the determination of copper and mercury in surface water (river), tap water and bottled mineral water samples.

Spatial distribution and speciation of mercury and methyl mercury in the surface water of East River (Dongjiang) tributary of Pearl River Delta, South China

The distribution and speciation of mercury in surface water of East River, Guangdong province, China were investigated. All told 63 water samples were collected during a bi-weekly sampling campaign from July 15th to 26th, 2009. Total mercury (THg) concentrations in water samples ranged from 11 to 49 ng/L. Maximum levels of THg were measured in the lower reaches of East River, where it passes through a major industrial area adjacent to Dongguang city. Higher ratios of dissolved mercury (THg (aq)) in proportion to THg were restricted to the downstream section of East River. Concentrations of the minor constituent methyl mercury varied in the range from 0.08 to 0.21 ng/L. On average, methyl mercury made up 0.8% and 0.56% of THg (aq) and THg, respectively. Dissolved species dominated the speciation of methyl mercury in proportions up to 81%, which may imply that methyl mercury is largely produced in situ within the river water. Environmental factors (such as water temperature, dissolved oxygen, etc.) are regarded to play an important role in Hg methylation processes were monitored and assessed. In an international perspective, East River must be classified as a polluted river with considerably sources within its industrial areas. The THg (aq) and particle mercury fluxes to the Pearl River Estuary by East River run-off were estimated to be 0.31 ± 0.11 and 0.17 ± 0.13 t/year, respectively. Hence, in total nearly 0.5 t Hg is annually released to the sea from the East River tributary.

Adsorption of Hg (II) in Biological and Environmental Samples onto Dithizone-Anchored Organobentonite

A new method for the determination of traces of mercury in environmental and biological samples is described. The present methodology combines determined using a hydride generation-atomic absorption spectrometry (HG-AAS) with pre-concentration/separation of the analyte on dithizone-anchored organobentonite (D-O-bentonite). Optimal experimental conditions for the adsorption of the Hg, including pH, contact time, eluent concentration and volume and co-existing ions have been studied. The result showed that the mercury could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 5.0, the adsorption time was 15 min, and capacity of adsorption was 23.2 mg·g-1. The mercury adsorbed on the sorbent could be completely eluated by using 3 mol·L-1 HCl. The adsorption agent has been applied to the pre-concentration/separation of mercury in surface water and human hair samples with satisfied results.

Photoreactions of Mercury in Surface Ocean Water: Gross Reaction Kinetics and Possible Pathways

We present pseudofirst order rate constants for gross photoreduction and gross photooxidation of mercury in surface water from the open Atlantic Ocean, determined under controlled laboratory conditions. Experiments using both unfiltered and filtered ocean water were carried out to characterize the importance of microbes and colloids on reaction kinetics. Results indicate that reduction and oxidation of mercury in ocean water does not follow a simple two-species reversible reaction pathway. We suggest two possible redox pathways that reproduce the pattern of dissolved gaseous mercury (DGM) concentrations observed in our laboratory experiments, and evaluate them using a controlled outdoor experiment. In both proposed pathways Hg(0), the major constituent of DGM, is converted to an unidentified oxidized species that is different from the reducible form present initially. This reaction step plays a major role in the net formation of DGM in our experiments. Our results represent new quantitative information about the gross reaction kinetics for both reduction and oxidation of mercury in open ocean surface water. Pseudofirst order rate constants for reduction reactions that form DGM were determined to be in the range of 0.15-0.93 h(-1) and pseudofirst order rate constants for oxidation of Hg(0) to be in the range of 0.4-1.9 h(-1). Microbes and colloids did not appreciably influence the reduction and oxidation kinetics.

Mercury emission from a temperate lake during autumn turnover

Lakes in temperate regions stratify during summer and winter months, creating distinct layers of water differentiated by their physical and chemical characteristics. When lakes mix in autumn and spring, mercury cycling may be affected by the chemical changes that occur during mixing. Sampling was conducted in Lake Lacawac, Eastern Pennsylvania, USA, throughout the autumn of 2007 to characterize changes in emission of gaseous elemental mercury (Hg 0) from the lake surface and dissolved mercury profiles in the water column during mixing. Water chemistry and weather parameters were also measured, including dissolved organic carbon (DOC), iron, and solar radiation which have been shown to interact with mercury species. Results indicate that emission of Hg 0 from the lake to the atmosphere during turnover was controlled both by solar radiation and by surface water mercury concentration. As autumn turnover progressed through the months of October and November, higher mercury concentration water from the hypolimnion mixed with epilimnetic water, increasing mercury concentration in epilimnetic waters. Dissolved absorbance was significantly correlated with mercury concentrations and with iron, but DOC concentrations were essentially constant throughout the study period and did not exhibit a relationship with either dissolved mercury concentrations or emission rates. Positive correlations between dissolved mercury and iron and manganese also suggest a role for these elements in mercury transport within the lake, but iron and manganese did not demonstrate a relationship with emission rates. This research indicates that consideration of seasonal processes in lakes is important when evaluating mercury cycling in aquatic systems.