Mercury In Seawater Research Articles

Observation-Based Mercury Export from Rivers to Coastal Oceans in East Asia.

Globally, the consumption of coastal fish is the predominant source of human exposure to methylmercury, a potent neurotoxicant that poses health risks to humans. However, the relative importance of riverine inputs and atmospheric deposition of mercury into coastal oceans remains uncertain owing to a lack of riverine mercury observations. Here, we present comprehensive seasonal observations of riverine mercury and methylmercury loads, including dissolved and particulate phases, to East Asia's coastal oceans, which supply nearly half of the world's seafood products. We found that East Asia's rivers annually exported 95 ± 29 megagrams of mercury to adjacent seas, 3-fold greater than the corresponding atmospheric deposition. Three rivers alone accounted for 71% of East Asia's riverine mercury exports, namely: Yangtze, Yellow, and Pearl rivers. We further conducted a metadata analysis to discuss the mercury burden on seawater and found that riverine export, combined with atmospheric deposition and terrestrial nutrients, quantitatively elevated the levels of total, methylated, and dissolved gaseous mercury in seawater by an order of magnitude. Our observations support that massive amounts of riverine mercury are exported to coastal oceans on a continental scale, intensifying their spread from coastal seawater to the atmosphere, marine sediments, and open oceans. We suggest that the impact of mercury transport along the land-ocean aquatic continuum should be considered in human exposure risk assessments.

Field determination of inorganic mercury in seawaters by a portable dual-channel and purge-and-trap system with atomic fluorescence spectrometry

ABSTRACT An on-line flow injection mercury analyser (FIMA) for inorganic mercury (Hg) analysis in environmental waters is presented. The FIMA is a portable dual-channel and purge-and-trap system combining aqueous reduction with stannous chloride (SnCl2), two-stage gold (Au) amalgamation, thermal desorption of Hg0 and final detection with cold vapour atomic fluorescence spectrometry (CVAFS). Simultaneous on-line operations of sample loading and analysis make analytical throughput and accuracy improved and contamination eliminated. Results of system optimisation and reliability regarding the determination of inorganic Hg2+ are described. Analytical performances of both channels were the same in terms of data reliability. Low procedural blanks were obtained from laboratory and field trip (≤5 pg, n = 30). Excellent calibrations (r2 > 0.99) with a high precision and good stability (RSD <5%, n = 30) were obtained. Detection limits and reproducibility of the methods have been estimated as ≤0.05 ng L−1 and <5% (0.5 ng L−1, n = 30). The system was finally validated by measurements comparison of the two channels (r2 > 0.98), and analysis of a certified reference material (coastal seawater BCR-579, recoveries 101 ± 4%, n = 10). Overall, a sample throughput of ~10 samples per hour with two-channel detections of FIMA can be achieved. The onboard analysis of inorganic Hg species (e.g. elemental, reactive, and total Hg) in surface seawaters of the East China Sea (ECS) are also successfully achieved. The portable FIMA is fast, easy, and robust for reliable monitoring of Hg in natural seawaters.

Distribution and Transformation of Mercury in Subtropical Wild-Caught Seafood from the Southern Taiwan Strait.

Wild-caught seafood contains significant amounts of mercury. Investigating the mercury accumulation levels in wild-caught seafood and analyzing its migration and transformation are of great value for assessing the health risks of mercury intake and for the tracking of mercury sources. We determined the concentrations and stable mercury isotopic compositions (δ202Hg, Δ199Hg, Δ200Hg, and Δ201Hg) of 104 muscle samples collected from 38 species of seafood typically harvested from the Taiwan Shallow Fishing Ground (TSFG), Southern Taiwan Strait. Overall, the concentrations of total mercury (THg) and methylmercury (MeHg) ranged from 11 to 479 ng/g (dry weight, dw) and 10 to 363 ng/g (dw), respectively, and were below the threshold value established by the USEPA and the Chinese government. Demersal and near-benthic species accumulated more mercury than pelagic or mesopelagic species. The characteristics of mercury isotopes in wild-caught marine species differed in terms of vertical and horizontal distribution. Considering the known peripheral land sources of mercury (Δ199Hg ≈ 0), the mercury in seafood from the TSFG (Δ199Hg > 0) did not originate from anthropogenic emissions. The ratio of Δ199Hg and Δ201Hg (1.18 ± 0.03) suggested that the photoreduction of Hg (II) and the photo-degradation of MeHg equally contributed to mass-independent fractionation. Based on the values of Δ199Hg/δ202Hg (1.18 ± 0.03), about 67% of the mercury in seawater had undergone microbial demethylation prior to methylation and entering the seafood. Additionally, the vertical distribution of Δ200Hg in seafood from different water depths implies that mercury input was in part caused by atmospheric deposition. Our results provide detailed information on the sources of mercury and its transfer in the food web in offshore fishing grounds.

Assessment of chromium, lead and mercury in seawater and some fish species from the Gulf of Urabá, Colombian Caribbean: a baseline study.

The coastline of the department of Antioquia, in Colombia, exhibits a wide variety of aquatic and land ecosystems rich in both diversity and abundance. However, it is exposed to a variety of human activities, including industry, tourism, and mining. Banana cultivation is the main activity carried out in this region, which offers large economic benefits. In addition, there are diverse fishery resources that are main basis of the economy and nutrition for the population. Over the years, the Gulf of Urabá has been affected by serious pollution problems due to elevated contents toxic compounds that deteriorate the aquatic ecosystem, even our laboratory has conducted previous studies in heavy metals in fish from this same area. The aim of this study was to evaluate the contents of chromium (Cr), lead (Pb), and mercury (Hg) in seawater and fish muscle in three fish species from the Gulf of Urabá that are commercialized and consumed by the population of the municipality of Turbo, using microwave-induced plasma optical emission spectrometry (MIP OES). The occurrence of toxic metals in seawater in this area has not been reported, and to the best of our knowledge, this is the first study. Cr and Pb concentrations in seawater from several sampling points were detected ranged from 0.025 to 0.369 mg/L and 0.012-0.165 mg/L, respectively, while Hg levels were below detection limit. Regarding fish samples, Pb and Hg levels range 0.64-1.91 mg/kg and 0.11-1.09 mg/kg, respectively. Sea catfish species exhibited the highest content of metals, followed by stone head catfish and anchovy, it which showed the lowest contamination by metals. In this study, levels that exceed the limits in Colombian regulations regarding metal contents in discharge points to surface water and fishery products for human consumption were found.

Multicolor Aptasensor Based on DNA-Induced Au-Ag Nanorods for Simultaneous and Visual Detection of Inorganic and Organic Mercury.

Compared to inorganic mercury (Hg2+), methyl-mercury (CH3Hg+) and ethyl-mercury (C2H5Hg+) (organic mercury) not only have a much stronger toxicity but also are more easily accumulated by marine organisms to produce bioamplification. Therefore, the simultaneously onsite detection of Hg2+ and organic mercury is of great significance to ensure the safety of seafood, and it is also a hard challenge. We designed a T-rich aptamer, HT7, for specifically recognizing Hg2+ and organic mercury and developed a multicolor aptasensor for simultaneous discrimination and detection of Hg2+ and organic mercury with only bare-eye observation using HT7 as a recognition probe and gold nanorods (AuNRs) as a signal. In the presence of Hg2+ and Ag+, Hg2+ preferentially and specifically bind with HT7 immobilized on AuNRs surface and induce the formation of a monolayer Ag/Hg amalgam on the AuNRs surface after reduction, resulting in a change in color from orange to faint purple and a corresponding shift in the absorption peak from 820 to 730 nm in the solution. However, in the presence of CH3Hg+ or C2H5Hg+ and Ag+, CH3Hg+ or C2H5Hg+ preferentially bind with HT7 immobilized on the AuNRs surface and induce the formation of a monolayer Ag0 on the AuNRs surface after reduction, which results in the change in color from orange to atrovirens and the corresponding shift in the absorption peak shift from 820 to 670 nm in the solution. Thus, the inorganic and organic mercury (total of CH3Hg+ and C2H5Hg+) can be specifically discriminated and detected by only bare-eye observation. The method can be used to simultaneously detect inorganic and organic mercury in seawater by the bare-eye observation with a visual detection limit of 2.0 ppm for Hg2+ and 10.0 ppm for organic mercury. The success of this study is a useful enlightenment to develop an instrument-free method for an onsite detection of trace inorganic and organic mercury in environment by a bare-eye observation, although the sensitivity of the method is relatively low.

Spatial distribution of mercury in seawater, sediment, and seafood from the Hardangerfjord ecosystem, Norway

Hardangerfjord is one of the longest fjords in the world and has historical mercury (Hg) contamination from a zinc plant in its inner sector. In order to investigate the extent of Hg transferred to abiotic and biotic ecosystem compartments, Hg and monomethylmercury (MeHg) concentrations were measured in seawater, sediment, and seafood commonly consumed by humans. Although total mercury in seawater has been described previously, this investigation reports novel MeHg data for seawater from Norwegian fjords. Total Hg and MeHg concentrations in seawater, sediment, and biota increased towards the point source of pollution (PSP) and multiple lines of evidence show a clear PSP effect in seawater and sediment concentrations. In fish, however, similar high concentrations were found in the inner part of another branch adjacent to the PSP. We postulate that, in addition to PSP, atmospheric Hg, terrestrial run-off and hydroelectric power stations are also important sources of Hg in this fjord ecosystem. Hg contamination gradually increased towards the inner part of the fjord for most fish species and crustaceans. Since the PSP and the atmospheric Hg pools were greater towards the inner part of the fjord, it is not entirely possible to discriminate the full extent of the PSP and the atmospheric Hg contribution to the fjord food web. The European Union (EU) Hg maximum level for consumption was exceeded in demersal fish species including tusk (Brosme brosme), blue ling (Molva dypterygia) and common ling (Molva molva) from the inner fjord (1.08 to 1.89 mg kg−1 ww) and from the outer fjord (0.49 to 1.07 mg kg−1 ww). Crustaceans were less contaminated and only European lobster (Homarus gammarus) from inner fjord exceeded the EU limit (0.62 mg kg−1 ww). Selenium (Se) concentrations were also measured in seafood species and Se-Hg co-exposure dynamics are also discussed.

Bioaccumulation of methylmercury within the marine food web of the outer Bay of Fundy, Gulf of Maine.

Mercury and methylmercury were measured in seawater and biota collected from the outer Bay of Fundy to better document mercury bioaccumulation in a temperate marine food web. The size of an organism, together with δ13 C and δ15 N isotopes, were measured to interpret mercury levels in biota ranging in size from microplankton (25μm) to swordfish, dolphins and whales. Levels of mercury in seawater were no different with depth and not elevated relative to upstream sources. The δ13 C values of primary producers were found to be inadequate to specify the original energy source of various faunas, however, there was no reason to separate the food web into benthic, demersal and pelagic food chains because phytoplankton has been documented to almost exclusively fuel the ecosystem. The apparent abrupt increase in mercury content from “seawater” to phytoplankton, on a wet weight basis, can be explained from an environmental volume basis by the exponential increase in surface area of smaller particles included in “seawater” determinations. This physical sorption process may be important up to the macroplankton size category dominated by copepods according to the calculated biomagnification factors (BMF). The rapid increase in methylmercury concentration, relative to the total mercury, between the predominantly phytoplankton (<125μm) and the zooplankton categories is likely augmented by gut microbe methylation. Further up the food chain, trophic transfer of methylmercury dominates resulting in biomagnification factors greater than 10 in swordfish, Atlantic bluefin tuna, harbour porpoise, Atlantic white-sided dolphin and common thresher shark. The biomagnification power of the northern Gulf of Maine ecosystem is remarkably similar to that measured in tropical, subtropical, other temperate and arctic oceanic ecozones.

Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery

Methylmercury (MeHg) is a potent neurotoxin that is biomagnified approximately 1-10 million-fold in aquatic carnivores such as the Northern elephant seal (Mirounga angustirostris), whose excreta and molted pelage, in turn, constitute a source of environmental MeHg contamination at the base of marine food chains. The potential for this top-down contamination is greatest in coastal areas with productive marine ecosystems that provide ideal habitats for large marine mammal colonies that can number in the thousands. This recycling of MeHg was evidenced by comparing total mercury (HgT) and MeHg concentrations in seawater, and HgT in molted pelage of M. angustirostris, at the Año Nuevo State Reserve pinniped rookery with concentrations at neighboring coastal sites in Central California. Seawater MeHg concentrations around the rookery (average = 2.5 pM) were markedly higher than those at the comparison coastal sites (average = 0.30 pM), and were as high as 9.5 pM during the M. angustirostris molting season. As a consequence, excreta and molts from this marine mammal colony, and presumably other marine predator populations, constitute a major source of MeHg at the base of the local marine food chain.

Development and validation of a method for mercury determination in seawater for the process control of a candidate certified reference material.

A simple, robust and reliable method for mercury determination in seawater matrices based on the combination of cold vapour generation and inductively coupled plasma mass spectrometry (CV-ICP-MS) and its complete in-house validation are described. The method validation covers parameters such as linearity, limit of detection (LOD), limit of quantification (LOQ), trueness, repeatability, intermediate precision and robustness. A calibration curve covering the whole working range was achieved with coefficients of determination typically higher than 0.9992. The repeatability of the method (RSDrep) was 0.5 %, and the intermediate precision was 2.3 % at the target mass fraction of 20 ng/kg. Moreover, the method was robust with respect to the salinity of the seawater. The limit of quantification was 2.7 ng/kg, which corresponds to 13.5 % of the target mass fraction in the future certified reference material (20 ng/kg). An uncertainty budget for the measurement of mercury in seawater has been established. The relative expanded (k = 2) combined uncertainty is 6 %. The performance of the validated method was demonstrated by generating results for process control and a homogeneity study for the production of a candidate certified reference material.

Development of a deep-sea mercury sensor using &lt;i&gt;in situ&lt;/i&gt; anodic stripping voltammetry

Copyright © 2015 by The Geochemical Society of Japan. mercury in seawater can be an indicator of widespread underwater mineral deposits (Marumo et al., 2008; Tomiyasu et al., 2007). Therefore, deep-sea mercury monitoring is very important to both the caution of environmental pollution and the exploration of underwater mineral deposits. Due to their high sensitivity, cold vapor atomic absorption spectrometry (CV-AAS) (Chakraborty et al., 2014a, c), cold vapor atomic fluorescence spectrometry (CV-AFS) (Fernandez-Martinez et al., 2015), and inductively coupled plasma mass spectrometry (ICP-MS) (Baya et al., 2015) have been the most commonly used for the measurement of total mercury. All of these techniques require expensive and sophisticated instrumentation combined with complicated sample preparation processes (Chakraborty et al., 2015; Ferreira et al., 2015; Giacomino et al., 2008). Sample collection needs certain spatial and temporal resolutions of the target fields, and there is a risk of contamination and/or loss of mercury during the sampling and transfer of water from depth to the surface Development of a deep-sea mercury sensor using in situ anodic stripping voltammetry

Isotopic composition analysis of dissolved mercury in seawater with purge and trap preconcentration and a modified Hg introduction device for MC-ICP-MS

A modified introduction device and a preconcentration method were developed to enhance the sensitivity of the Hg isotopic analysis method.

Determination of dissolved gaseous mercury in seawater of Minamata Bay and estimation for mercury exchange across air–sea interface

Dissolved gaseous Hg (DGM) in seawater and atmospheric gaseous Hg were measured at six sites in Minamata Bay to investigate mercury (Hg) evasion flux from the sea surface. Minamata Bay was severely polluted with mono-methyl Hg (MMHg). Total Hg and MMHg, seawater characteristics such as water temperature and salinity, and meteorological parameters were also observed to estimate the air–sea exchange of Hg. The mean concentration of DGM was 116±76pgL−1 (N=75), ranging from 19 to 442pgL−1, and the concentrations were higher in summer than in other seasons. DGM concentration showed a significantly positive correlation with solar radiation, and air and water temperatures. Inversely, DGM showed a significantly negative correlation with salinity and redox potential (ORP). Hg evasion fluxes from the sea surface of the bay were calculated using a two-layer gas exchange model and ranged between 0.11 and 33ngm−2h−1 (mean, 5.4±6.3ngm−2h−1). The estimated flux was slightly higher in the spring and fall when wind speed increased because the gas exchange coefficient used for estimating Hg evasion flux strongly depends on wind speed. The annual evasion flux of Hg from the sea surface of Minamata Bay was estimated to be 47±56μgm−2, which was on the same order of magnitude as the direct atmospheric deposition flux of Hg (24μgm−2) during the observation period. Therefore, Hg evasion from the sea surface likely plays an important role in the Hg cycle of Minamata Bay.

Rapid speciation analysis of mercury in seawater and marine fish by cation exchange chromatography hyphenated with inductively coupled plasma mass spectrometry

In this work, a hybrid method for the rapid speciation of mercury compounds by cation exchange chromatographic separation and inductively coupled plasma mass spectrometry (ICP-MS) detection is reported. Effective separation of inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) within 2–2.5min was achieved on two consecutive 12.5-mm strong cation exchange guard columns with 2.0mM l-cysteine or thiourea (pH 2.0) as the mobile phase. This separation met the requirements of green analytical chemistry such as the prevention of toxic waste, safer HPLC mobile phases, and short separation times to reduce operating costs. The detection limits for Hg2+, MeHg, EtHg and PhHg were 0.019, 0.027, 0.031 and 0.022μgL−1, each, and the repeatabilities of peak height and peak area (5.0μgL−1 for each Hg species) were all lower than 3%. Contents of Hg species and total mercury in certified reference materials of seawater (GBW(E) 080042) and fish tissue (GBW 10029) were in good accordance with the certified values, and satisfactory recoveries (96–102% for GBW(E) 080042 and 94–101% for GBW 10029) validated the developed method. The developed method was applied for the speciation of mercury in five seawater sample and five marine fish samples. The concentrations of mercury species in all analyzed fish samples did not exceed the permissible levels of the National Standard of China.

The distribution and sea–air transfer of volatile mercury in waste post-desulfurization seawater discharged from a coal-fired power plant

The waste seawater discharged in coastal areas from coal-fired power plants equipped with a seawater desulfurization system might carry pollutants such as mercury from the flue gas into the adjacent seas. However, only very limited impact studies have been carried out. Taking a typical plant in Xiamen as an example, the present study targeted the distribution and sea-air transfer flux of volatile mercury in seawater, in order to trace the fate of the discharged mercury other than into the sediments. Samples from 28 sampling sites were collected in the sea area around two discharge outlets of the plant, daily and seasonally. Total mercury, dissolved gaseous mercury and dissolved total mercury in the seawater, as well as gaseous elemental mercury above the sea surface, were investigated. Mean concentrations of dissolved gaseous mercury and gaseous elemental mercury in the area were 183 and 4.48ngm(-3) in summer and 116 and 3.92ngm(-3) in winter, which were significantly higher than those at a reference site. Based on the flux calculation, the transfer of volatile mercury was from the sea surface into the atmosphere, and more than 4.4kg mercury, accounting for at least 2.2% of the total discharge amount of the coal-fired power plant in the sampling area (1km(2)), was emitted to the air annually. This study strongly suggested that besides being deposited into the sediment and diluted with seawater, emission into the atmosphere was an important fate for the mercury from the waste seawater from coal-fired power plants.

An automatic Flow System of Rapid on-Line Digestion and Pre-Concentration for In-Field Determination of Trace Total Mercury in Seawater

An automatic flow system of rapid on-line sampling, digestion, and pre-concentration for in-field determination of total mercury in seawater has been developed. In this system, both UV radiator and bromine monochloride (1%, v/v) were used to make the sample digestion rapid and reliable. And, the active gold columns were used for the effective preconcentration of mercury. Double loops connected to an 8-way valve were adopted to quantitate the volume of samples and reductant, respectively. With the hyphenation of the flow system and cold vapor atomic fluorescence spectrometry (CVAFS), the detection limit for total mercury was as low as 0.04 ng/L. The manifold parameters, including the carrier gas flow, digestion time, purging time, and reagent flow rates, were optimized. The calibration curve (p = 0.0566C+0.0174, n = 8, R 2 = 0.9994) was obtained within the range of 0.18-200 ng/L. The relative standard deviation (RSD) was 1.9% (n = 12), evaluated from 12 successive measurements of a real seawater sample at 5.2 ng/L mercury level. The recovery ranged from 99.4% to 109%. The analysis speed of the system was 6.5 min per sample. Furthermore, the proposed method was applied to in-field analysis of sixteen real seawater samples for total mercury. The samples were also analyzed with US EPA method (EPA, 1631) in the laboratory. The correlation coefficient between the results obtained with the two methods was 0.9762.

An intercomparison of procedures for the determination of total mercury in seawater and recommendations regarding mercury speciation during GEOTRACES cruises

We conducted a laboratory intercomparison of total mercury (Hg) determination in seawater collected during U.S. GEOTRACES Intercalibration cruises in 2008 and 2009 to the NW Atlantic and NE Pacific Oceans. Results indicated substantial disagreement between the participating laboratories, which appeared to be affected most strongly by bottle cleanliness and preservation procedures. In addition, we examined the effectiveness of various collection and sample preparation procedures that may be used on future GEOTRACES cruises. The type of sampling system and filtration medium appeared to make little difference to results. Finally, and in light of results from experiments that considered sample bottle material effect and the development of new methods for CH3Hg+ extraction from seawater, we propose a recommended procedure for determining all four of the major Hg species in seawater (elemental, dimethyl‐, monomethyl‐, and total Hg).

Fast speciation of mercury in seawater by short-column high-performance liquid chromatography hyphenated to inductively coupled plasma spectrometry after on-line cation exchange column preconcentration

A simple and fast method for trace speciation analysis of mercury (Hg2+), methylmercury (MeHg+) and ethylmercury (EtHg+) in seawater has been developed by short-column high-performance liquid chromatography hyphenated to inductively coupled plasma spectrometry (HPLC–ICP-MS) after on-line cation-exchange column (CEC) preconcentration. The analytes were firstly adsorbed on the CEC without any extraneous reagent, and then were eluted rapidly (within seconds) and completely with a very low concentration of l-cysteine solution, which provides the conveniency for the on-line coupling of the preconcentration method and detection technique. To our best knowledge, it is for the first time to employ the CEC preconcentration technique to trap all of the three mercury species simultaneously at their positive charged status for the purpose of speciation analysis. Under the optimized conditions, a very high preconcentration factor up to 1250 has been obtained with 30mL sample solution, which leads to the very low detection limits of 0.042ngL−1 for Hg2+, 0.016ngL−1 for MeHg+ and 0.008ngL−1 for EtHg+ (as Hg), respectively. With the established method, three seawater samples were also analyzed, and all the three mercury species have been found in each sample, albeit at a very low concentration.

Storage bottle material and cleaning for determination of total mercury in seawater

Accurate determinations of trace levels of mercury (Hg) in water require scrupulously clean sampling equipment and storage bottles. To avoid Hg contamination during storage, it has been presumed that water samples must be stored in either glass or Teflon bottles cleaned with a rigorous method, such as submersion in hot acid. These cleaning procedures are hazardous, and use of Teflon bottles can be cost prohibitive for major oceanographic programs. We investigated the suitability of alternative cleaning procedures and bottle materials for storage of seawater containing sub‐picomolar levels of Hg. We found that a simple technique with detergent, dilute acid, and bromine monochloride removes Hg from all bottle materials tested, which included FEP Teflon, glass, polycarbonate (PC), low‐density polyethylene (LDPE), and fluorinated polyethylene (FLPE). The technique is effective for bottles that are either new or used previously for trace‐level oceanographic samples (total Hg &lt; 10 pM). Stability of seawater Hg levels differed dramatically among storage bottle materials during a 74‐ week test. Hg in seawater stored in LDPE, FLPE, and FEP bottles increased within 15 weeks of storage at room temperature. In contrast, Hg levels in seawater stored in PC bottles were increased modestly only after 74 weeks of storage and those in glass bottles were unchanged throughout the test. We recommend future use of this new cleaning method and encourage greater use of glass and PC bottles for storage of waters containing low levels of Hg.

Imaging Time-Resolved Electrothermal Atomization Laser-Excited Atomic Fluorescence Spectrometry for Determination of Mercury in Seawater

In this study, direct determination of mercury at the nanogram per liter level in the complex seawater matrix by imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry (ITR-ETA-LEAFS) is described. In the case of mercury, the use of a nonresonant line for fluorescence detection with only one laser excitation is not possible. For measurements at the 253.652 nm resonant line, scattering phenomena have been minimized by eliminating the simultaneous vaporization of salts and by using temporal resolution and the imaging mode of the camera. Electrothermal conditions (0.1 M oxalic acid as matrix modifier, low atomization temperature) have been optimized in order to suppress chemical interferences and to obtain a good separation of specific signal and seawater background signal. For ETA-LEAFS, a specific response has been obtained for Hg with the use of time resolution. Moreover, an important improvement of the detection limit has been obtained by selecting, from the furnace image, pixels collecting the lowest number of scattered photons. Using optimal experimental conditions, a detection limit of 10 ng L(-1) for 10 μL of sample, close to the lowest concentration level of total Hg in the open ocean, has been obtained.

Mercury Species in Seawater and Sediment of Xiamen Western Sea Area Adjacent to a Coal‐fired Power Plant

The purpose of this study was to investigate the concentrations and spatial distributions of mercury (Hg) species in seawater (including dissolved, particle, and total Hg) and sediment (including total and methyl Hg) of the Xiamen western sea area adjacent to a coal-fired power plant. The influence of the wastewater discharged from the seawater desulphurization (De-SO2) system of the power plant is discussed. Concentration of the three species of mercury in seawater from 18 sampling sites varied: dissolved ranged from 0.70 to 4.65 ng/L (mean 1.47 ng/L; median 1.12 ng/L); particulate ranged from not detected to 90.52 ng/L (mean 10.47 ng/L; median 1.26 ng/L); and total was 1.51 to 92.88 ng/L (mean 11.94 ng/L; median 2.84 ng/L). High concentrations of total Hg and particulate Hg, more than 70 ng/L, were observed in the area adjacent to the outfalls of the power plant. The Hg from the waste seawater of the power plant might be re-emitted to the atmosphere because it exists in seawater mainly in particulate attached form. The sediment total Hg concentrations ranged from 0.055 to 0.201 microg/g, with a mean of 0.126 microg/g and a median of 0.125 microg/g. Low methyl Hg concentrations in the sediment were observed in the study area, ranging from 0.017 to 0.256 ng/g as Hg, with a mean of 0.087 ng/g and a median of 0.081 ng/g. The ratios of methyl Hg to total Hg in the sediment were low, with a mean and median of 0.069%. Both total and methyl Hg were significantly linked to the sediment organic carbon (SOC).