Trace metals inputs in the Adour urban estuary: Influence and impact of human pressure

International audienceAlthough the contamination of number of estuarine environments in the European Atlantic Coast has largely been studied [1-2], the Adour urban estuary watershed (southwestern, France) is poorly known. The estuarine part is characterized by an important anthropogenic pressure close to its mouth with large urban and industrial activities of Bayonne city. An environmental assessment program was funded to evaluate and quantify the anthropogenic pressure on the ecosystem. A preliminary sampling strategy was adopted to identify 25 specific sources of contaminants, monitored more extensively under four campaigns. Data treatment allows to trace effluent source and origin resulting in a specific classification. Trace metal concentrations were determined (filtrate (<0, 45 μm) and particulate fractions) for each effluent and combined with discharge flow measurements to establish anthropogenic net fluxes. Industrial effluents presents the highest concentrations observed, followed by waste landfield drainage and sewage effluents. The large variability in terms of effluent characteristics and concentrations observed, can be explained by strong relationship between trace elements and both organic matter level (TOC) and flow rate. This study point out the dominance of upstream inputs compared to downstream localized sources, but their influence into the estuarine ecosystem during low discharge conditions (summer) lead to a maximum metal impact

Improvement of analytical performances for mercury speciation by on-line derivatization, cryofocussing and atomic fluorescence spectrometry

cited By 49International audienceA modified automated on-line hyphenated system for simultaneous inorganic ionic mercury (Hg2+) and monomethylmercury (MeHg+) analysis by hydride generation (HG) or ethylation (Eth), cryofocussing, gas chromatography (GC) separation and atomic fluorescence spectrometry (AFS) detection has been improved. Both derivatization methods are investigated with respect to the chromatographic and analytical performances. They can be both affected by interferences when the AFS detection system is used. Water vapor removal using a soda lime moisture trap improves significantly the chromatographic performances, the reproducibility and the detection limits for Hg2+ and MeHg+ analyzed with both methods. For ethylation (Eth) derivatization, a scattering interference generated from low-quality ethylation reagent has also been eliminated. For HG, improved detection limits are 0.13 ng l-1 and 0.01 ng l-1 for Hg2+ and MeHg+, respectively (0.11 water sample), and reproducibility are 5% for Hg2+ (20 ng l-1) and MeHg+ (5 ng l -1). Improved detection limits for Eth are 0.22 ng g-1 for Hg2+ and 0.02 ng g-1 for MeHg+ (1 g dry sediment sample) and the reproducibility are 5-6% for Hg2+ and MeHg+ (1-2 ng g-1). © 2003 Elsevier B.V. All rights reserved

Trace metals inputs in the Adour urban estuary: Influence and impact of human pressure

Although the contamination of number of estuarine environments in the European Atlantic Coast has largely been studied [1-2], the Adour urban estuary watershed (southwestern, France) is poorly known. The estuarine part is characterized by an important anthropogenic pressure close to its mouth with large urban and industrial activities of Bayonne city.
An environmental assessment program was funded to evatuate and quantify the anthropogenic pressure on the ecosystem. A preliminary sampling strategy approach was adopted to identify 25 specific sources of contaminants, monitored more extensively under four campaigns. Data treatment allows to trace effluent source and origin resulting in a specific classification. Trace metal concentrations were determined (filtrate ($<$0,45 $\mu$m) and particulate fractions) for each effluent and combined with discharge flow measurements to establish anthropogenic net fluxes. Industrial effluents presents the highest concentrations observed, followed by waste landfield drainage and sewage effluents. The large variability in terms of effluent characteristics and concentrations observed, can be explained by strong relationship between trace elements and both organic matter level (TOC) and flow rate.
This study point out the dominance of upstream inputs compared to downstream localized sources, but their influence into the estuarine ecosystem during low discharge conditions (summer) lead to a maximum metal impac

Application of cryofocusing hydride generation and atomic fluorescence detection for dissolved mercury species determination in natural water samples

cited By 21International audienceThe concentration levels of mercury (Hg) species in natural Water samples are usually low. Consequently, accurate analysis with low detection limits is still a major problem. In this work, a method was applied for the simultaneous direct determination of dissolved mercury species in water samples by on-line hydride generation (HG), cryogenic trapping (CT), gas chromatography (GC) and detection by atomic fluorescence spectrometry (AFS). The suitability of the method for real samples with different organic matter and chloride contents was evaluated by recovery experiments in synthetic and natural spiked water samples. The HG method was compared with other current available methods for mercury analysis with respect to the different fraction of mercury analysed, i.e. 'reactive', 'reducible' or total. HG derivatization and SnCl2 reduction (with and without previous oxidation with BrCl) were applied to synthetic and natural (spiked and non-spiked) water samples. The influence of chloride and dissolved organic matter concentrations was studied. The results suggest that the HG procedure is suitable for the simultaneous determination of Hg2+ and MeHg+ in surface water samples. Inorganic mercury analysed by HG (i.e. reducible) is close to the total inorganic mercury

Inorganic mercury and methylmercury in surface sediments and mussel tissues from a microtidal lagoon (Bizerte, Tunisia)

cited By 18International audienceThe aim of this study was to investigate the distribution of mercury compounds in marine sediments and mussel tissues collected in the lagoon of Bizerte, Tunisia, during two seasons (summer and winter). Inorganic mercury (Hg2+) concentrations in sediments were found to be highly variable, ranging from 0.04 nmol.g-1 to 3.22 nmol.g-1 (dry weight) with a mean value of 0.52 nmol.g-1. Anthropogenic sources of Hg2+, most probably metallurgy or tire production industries, have been evidenced. The mean concentration of monomethylmercury (MeHg+) in the surface sediments is 2.32 pmol g-1 ranging from below the detection limit (0.45 pmol.g-1) to 14.6 pmol.g-1. No significant variation was observed between winter and summer seasons for both mercury species concentration in the sediments. The Hg2+ concentrations in mussel tissues are also variable, ranging from 0.007 to 1.347 nmol.g-1 (dry weight). The mean concentration is 0.70 nmol.g-1. In these tissues, Hg2+ is generally the major compound, making up ca. 88% of total mercury concentrations. However, methylmercury concentrations are significant and homogeneous, ranging from 62 to 121 pmol.g-1 (mean 96 pmol.g-1 . The results suggest that a fraction of the inorganic mercury load in the sediments of the lagoon undergoes methylation pathways. MeHg+ produced is assimilated in the mussels more readily than Hg2+

Speciation analysis of mercury in aquatic environment

cited By 44International audienceThis review considers methods for mercury speciation with low limits of detection that can be applied to real aquatic environmental samples (waters, sediments, biological tissues). Special attention is given to the necessity of clean sampling procedures and the proper storage of the samples. In this review, different extraction techniques for sediments and biological tissues are considered. The performance of different separation techniques, like liquid chromatography and off-line and on-line gas chromatography, are compared for their environmental applications

Multiple regression analysis to assess the spatial distribution and speciation of mercury in surface sediments of a contaminated lagoon

International audienceThe concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in surface sediments from the contaminated Aveiro Lagoon (Portugal) were determined by species-specific isotope dilution analysis. Different behaviour of IHg and MeHg was observed based upon multiple regression analysis, including geochemical characteristics of the surface sediments (fine fraction, concentrations of organic matter and metals) and non-Euclidean distances between sampling points. This data treatment method was valid over the entire concentration range of IHg and MeHg, allowing robust quantitative evaluation with respect to extrapolation. For IHg, there was statistical separation of the dispersion away from the contamination source and of Al concentration in the sediments. The MeHg concentrations followed those of IHg at high concentrations. The geochemical variables, such as concentrations of Ca (marine influence proxy), Mn and organic matter, were necessary to describe the behaviour of MeHg across the whole concentration range. The models for MeHg demonstrated that, close to the mouth of the lagoon, net production of MeHg was higher. In future, multiple regression analysis could be applied to separate and to evaluate quantitatively the effects of geochemistry and dispersion away from the contamination source in sediments contaminated with other substances

Micro-scale preparation and characterization of isotopically enriched monomethylmercury

cited By 34International audienceA synthesis method for the micro-scale laboratory preparation of isotopically enriched monomethylmercury (MMHg) has been successfully established. This compound is an important standard for species-specific isotope dilution analysis. The isotopically enriched MMHg has been synthesized from commercially available mercury oxide (201HgO) using methylcobalamin coenzyme as methylating agent. The time required is less than 2 h and the final yield is about 90%. The proposed method is faster than those previously reported in the literature. It allows work on a micro scale to control the use of expensive enriched isotope standard. It also allows control of unintentional formation of dimethylmercury. The enriched mercury-containing reaction products were analyzed by capillary gas chromatography coupled to an inductively coupled plasma mass spectrometer after derivatization with sodium tetraethylborate. The isotopic composition, concentration, purity and stability of the synthesized, enriched MMHg have been investigated in order to establish standard protocols for MMHg isotope dilution analysis or isotope labeling incubation experiments. Copyright © 2002 John Wiley &amp; Sons, Ltd

Mercury in surface waters of a macrotidal urban estuary (River Adour, south-west France)

cited By 10International audienceSurface waters were collected in the River Adour estuary (south-western France) during different sampling periods from 1998 to 2001 in order to investigate the phase distribution and speciation of methylmercury (MeHg+). Although a high variability is observed, significant higher average concentrations of total MeHg+ (dissolved and particulate) are measured during the warm seasons, at 4.40 ± 8.18 pM and 3.90 ± 1.87 pM for July 1998 and September 1999, compared with the winter seasons, with concentrations at 0.99 ± 2.85 pM and 1.00 ± 1.75 pM for February 1998 and February 2001, respectively (one-tailed t-test, P = 0.01). The seasonal variations are explained with enhanced bacterial activity during summer and sedimentation/resuspension phenomena. Additionally, signi-ficant longitudinal variations of the MeHg+ concentrations are observed. The highest levels in both dissolved and particulate fractions are found within the downstream urban estuarine area. This can be explained by the high methylation potential of the sediments, but direct anthropogenic inputs of MeHg+ from specific discharge points cannot be neglected. Biogeochemical factors like phytoplankton biomass and salinity also show a relationship with MeHg+ partitioning in the surface waters of the Adour estuary