Christophe Mouvet

Laboratory accumulation and depuration of copper and cadmium in the freshwater mussel Dreissena polymorpha and the aquatic moss Rhynchostegium riparioides

This work assessed the potentialities of the zebra mussel Dreissena polymorpha and the aquatic moss Rhynchostegium riparioides as indicators of freshwater heavy metal contamination. Simultaneous exposure of the two species was performed in the same experimental system developed to fulfill the food requirements of the mussels. The exposure to Cu (4.5, 9, 21 and 50 μg L−1) and Cd (0.3, 6, 15 and 44 μg L−1) over a 27-day period was followed by a 14-day post-exposure phase. Accumulation of both metals was rapid in the mosses and reached a plateau after 18 days for Cu and 6 days for Cd; it was slower for the mussels and no steady state was observed, except for the lowest Cu treatment (9 μg L−1). The filtration rate of the bivalves and consequently bioaccumulation was reduced at the highest Cu concentration and in the absence of food. At the end of the depuration phase, the mosses had lost 50 ± 4 % of Cu and 88 ± 1 % of Cd, while the mussels had eliminated 18 ± 11 % of Cu and 5 ± 7 % of Cd. Highly significant linear relationships were observed at the end of both the accumulation and depuration phases (i) between the average aqueous Cu and Cd concentrations and the metal levels in the two organisms, and (ii) between the metal concentrations in the mussels and those in the mosses.

A review of the attenuation of trichloroethylene in soils and aquifers

Abstract The transport, transformation, sorption and volatilization of trichloroethylene (TCE) as a non-aqueous phase liquid (NAPL) and as a dissolved aqueous constituent, under both laboratory and field conditions, are reviewed. NAPL-TCE is expected to migrate quite rapidly in soils and other water-unsaturated conditions, leaving droplets of organic liquid in the pore spaces. At the water table level, TCE may stop its downward movement and diffuse laterally, together with a slow migration downwards. From there on NAPL-TCE will slowly dissolve in groundwater. However, some specific hydraulic characteristics may induce rapid transport downwards away from the water table. TCE may appear in soils and aquifers as a result of its wide industrial use and also, possibly, as a degradation by-product of other chlorinated hydrocarbon solvents. TCE can undergo abiotic and (mostly) biotic, aerobic and (mostly) anaerobic transformations leading to less chlorinated ethenes. A half-life of 300 days was observed under field conditions. Batch and column experiments show that TCE is weakly sorbed on soil and aquifer solids with linear partition coefficients. Retardation factors in the range of l to 9 are reported from laboratory and field investigations. The adsorption is almost fully reversible. Gaseous TCE is more adsorbed than aqueous TCE, the extent of uptake being greatly influenced by the moisture content of the solid. Soil gas surveys appear as a promising technique for the study of soil and groundwater contamination by TCE. NAPL-TCE contamination should be quite effectively removed by steam injection. Because of its low adsorption and weak degradation under aerobic conditions, the diffuse contamination of aquifers by dissolved TCE can be extensive. In the case of localized and more severe pollution, approaches for the restoration of aquifers based on pumping followed by treatment at the surface may be effective but they usually are not economical. In situ treatment by stimulating the biotrans-formation is considered as a favourable alternative.

Migration of chlorinated hydrocarbon solvents through Coventry sandstone rock columns

The migration in the Coventry sandstone aquifer system of aqueous solutions of various chlorinated hydrocarbon solvents (CHSs) (1,1,1-trichloroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (TeCE)) was studied by means of percolation experiments with undisturbed rock cores. The retardation factor (Rf) was very low (always less than 2 for TCA, less than 3 for TCE and less than 5 for TeCE). The Rf varied slightly according to the nature of the solid sample but could not be related to the solid organic carbon content. The solvent adsorption was always almost completely reversible and little affected by the percolation flow rate (0.08–0.56 m day−1). The CHS breakthrough curves were typical of non-equilibrium processes (caused by sorption by the solids and possibly by diffusion between mobile and immobile water). The Rf values obtained experimentally were much lower than those calculated from batch adsorption studies, showing that percolation experiments are necessary to evaluate the filtering properties of consolidated rocks. These results indicate that in the Coventry sandstone aquifer (relatively high vertical and, especially, lateral hydraulic conductivities), two-carbon CHS aqueous solutes should migrate readily with water with very little retardation.

Adsorption isotherms of tri- and tetrachloroethylene by various natural solids

Abstract Laboratory experiments were conducted to study the adsorption of tri- and tetrachloroethylene on a variety of natural solids, from aquifer sandstone and marls to upper horizons of various soils. The organic carbon content (foc) of the nine sorbents studied ranged from 0.13 to 1.20% and initial TCE and TeCE aqueous concentration from 1 to 1000 μg l−1. Sorption isotherms are linear and strongly, but not systematically, related to the foc of the solids. The observed partition coefficients are used to calculate retardation factors as a function of aquifer porosity and organic carbon content.

A Heterogeneous Complexation Model of the Adsorption of Trace Metals on Natural Particulate Matter

Trace metals are present in, and transported through, aquatic systems both in dissolved and particulate forms. This duality of phase contributes to the complexity in the understanding of their environmental geochemistry. Turekian (1977) stressed the significance of solid particles which, from soils to marine sediments, via rivers and winds, are the vectors of trace metals during the course of their geological migration. The relative mobility of a trace metal depends on its physical form (dissolved versus particulate). Similarily, the physical form, more than the distribution of the dissolved species might be responsible for its toxic or beneficial effect on biota (e.g., filter feeders and seizers will respond predominantly to particulate species).

Distinct bacterial community structure of 3 tropical volcanic soils from banana plantations contaminated with chlordecone in Guadeloupe (French West Indies)

In the French West Indies (FWI), the soil, andosols, ferralsols and nitisols, is highly polluted by chlordecone, although this organochlorine insecticide extensively applied to banana crops has been banned for 20years. This contamination has led to a major human health concern inducing the need for remediation of the contaminated soils. Work was conducted to help to evaluate the impact of remediation processes on the microbial communities from these soils. Microbial biomass was estimated after direct DNA extraction from three chlordecone-contaminated soils (an andosol, a ferralsol and a nitisol) and the bacterial community analyzed using t-RFLP. The FWI volcanic andosol was particularly recalcitrant to usual direct DNA extraction protocols hampering analysis of soil microbial communities until now, in contrast with the 2 other soils. For the first time, DNA was directly extracted from a FWI andosol based on yeast RNA addition at the lysis step. Differences in microbial biomass were thus observed between the 3 FWI soils. Moreover, the bacterial community structure was significantly distinct from each others and related to soil physico-chemical characteristics. Interestingly, differences in bacterial diversity could not be exclusively attributed to the level of chlordecone contamination.

Postscript: summary of the Coventry Groundwater Investigation and implications for the future

Abstract The broader implications of the Coventry Groundwater Investigation are discussed in this postscript. The complex interbedded sandstone and mudstone sequence under Coventry is seriously polluted by chlorinated hydrocarbon solvents. Investigations in such terrain will require much greater expenditure than was available for this project if they are to describe the distribution and movement of pollutants in enough detail to evaluate, quantitatively, options for aquifer clean-up. It is not realistic to consider clean-up of Coventrys groundwater at the present time because of the lack of detailed knowledge. It is probable, at least for the present, that clean-up is not feasible, because of hydrogeological constraints arising from the extreme variability of permeability in the system and an absence of operational techniques for clean-up. Stronger, more pro-active protection of groundwater is needed. A major recommendation for future investigations is a procedure to avoid open boreholes, which can allow pollution to penetrate deeper into the aquifer, and may confuse the results of sampling.

Two dechlorinated chlordecone derivatives formed by in situ chemical reduction are devoid of genotoxicity and mutagenicity and have lower proangiogenic properties compared to the parent compound

Chlordecone (CLD) is a chlorinated hydrocarbon insecticide, now classified as a persistent organic pollutant. Several studies have previously reported that chronic exposure to CLD leads to hepatotoxicity, neurotoxicity, raises early child development and pregnancy complications, and increases the risk of liver and prostate cancer. In situ chemical reduction (ISCR) has been identified as a possible way for the remediation of soils contaminated by CLD. In the present study, the objectives were (i) to evaluate the genotoxicity and the mutagenicity of two CLD metabolites formed by ISCR, CLD-5a-hydro, or CLD-5-hydro (5a- or 5- according to CAS nomenclature; CLD-1Cl) and tri-hydroCLD (CLD-3Cl), and (ii) to explore the angiogenic properties of these molecules. Mutagenicity and genotoxicity were investigated using the Ames’s technique on Salmonella typhimurium and the in vitro micronucleus micromethod with TK6 human lymphoblastoid cells. The proangiogenic properties were evaluated on the in vitro capillary network formation of human primary endothelial cells. Like CLD, the dechlorinated derivatives of CLD studied were devoid of genotoxic and mutagenic activity. In the assay targeting angiogenic properties, significantly lower microvessel lengths formed by endothelial cells were observed for the CLD-3Cl-treated cells compared to the CLD-treated cells for two of the three tested concentrations. These results suggest that dechlorinated CLD derivatives are devoid of mutagenicity and genotoxicity and have lower proangiogenic properties than CLD.