Jean-Francois Chiffoleau

Geochemistry of trace metals in the Gironde estuary

Abstract Using clean techniques, we measured the dissolved, particulate, and (by cross-flow filtration) colloidal fractions of Cd, Ni, Zn, Cu, Pb, Mn, and Fe in the Gironde, an estuary in southwestern France. The fractions of the particulate riverine metals that are apparently mobilized in the estuary vary from >90% for Cd to less than 2% for Pb. Observed mid-salinity maxima for Cd, Ni, and Zn are well reproduced by a simple steady-state conservation model which accounts for the inorganic complexation of the metals by seawater anions. The concentration profiles of other metals, except Fe, can also be modeled by choosing an appropriate desorbable fraction and maintaining equilibrium between particles and solution. While colloidal iron decreases rapidly at low salinities, the colloidal concentrations of the other metals are quasi-conservative in the estuary. It appears that the colloidal fraction contains both iron oxide particles that separate from the rest by coagulation and organic macromolecules which bind most of the other metals and remain in solution.

Trace metal distribution, partition and fluxes in the Seine estuary (France) in low discharge regime

Samples collected in surface waters of the Seine estuary (France) during a low discharge period were analyzed for dissolved and particulate trace metals (Cd, Co, Cu, Mn, Ni, Pb and Zn). The studies showed that these trace elements are reactive in the estuary: an addition to the dissolved phase is observed for Cd, Co, Cu, Mn, Ni and Zn and a removal for Pb. Cd, Cu, Ni and Zn are released from seaward fluxing riverine particles or estuarine sediments directly in the water column, while the dissolved Co-salinity distribution, similar to Mn distribution suggests a preliminary release in the sediment pore water. Rapid adsorption onto the suspended load plays a major role in Pb removal from the dissolved phase. Partition coefficients for the dissolved and particulate phase (KD) decrease in the order: Pb > Co > Cu, Zn > Ni > Cd, i.e. a sequence similar to those reported from others European areas. Gross riverine inputs to the estuary and net efflux of dissolved trace metals to the English Channel are estimated. Values show that the Seine river and its estuary constitute a significant source of trace metals for the North Sea.

Tributyltin along the coasts of Corsica (Western Mediterranean): a persistent problem.

Despite optimistic forecasts by various scientists after regulatory measures were taken in the 1980s, coastal tributyltin (TBT) contamination is still a major problem. The present study concerning Corsica (Western Mediterranean) shows that contamination is not limited to harbour areas, but extends along the coast, involving protected nature reserves. The concentrations measured in harbours, which can reach 200 ng TBT l(-1), tend to incriminate both pleasure craft and ferries providing regular service between the island and the continent. Contamination as high as 7 ng TBT l(-1) has been measured in waters of the Scandola nature reserve, which is quite excessive given the no effect concentrations (NOEC) for marine fauna are around 1-2 ng TBT l(-1). The inadequacy of current regulations and their application are a major factor in this situation.

Influence of the Gironde estuary outputs on cadmium concentrations in the waters: consequences on the Marennes-Oléron bay (France)

The Gironde, an estuary in Southwestern France, has been highly contaminated by cadmium for many years, and the results of the French mussel watch suggest that this contamination is not restricted to the estuary, but could be responsible for relatively high levels of Cd in the oysters from the Marennes-Oleron bay located nearby. This hypothesis has been evaluated through three cruises carried out in the Gironde estuary and plume, the Marennes-Oleron bay, and the Charente estuary, a river of minor importance that influences directly this bay. The field results from the Pertuis cruise (May 1991) and two others conducted in January and December of the same year show that the Gironde is an important source of dissolved cadmium for the bordering continental shelf (11 t year–1), while the Charente inputs are far lower (60 kg year–1). Dissolved Cd concentrations on the shelf vary according to the salinity, ranging from 0.76 nmol L–1 close to the Gironde to 0.15 nmol L–1 far from the shore. The field data as well as simulations from a 3D hydrodynamic model show that the Gironde plume reaches the Antioche Straits north of the Marennes-Oleron bay, and that the Charente plume is diluted in the bay by marine waters strongly influenced by the Gironde. This study confirms that the Gironde estuary is an important source of cadmium for the Marennes-Oleron bay.

Cadmium in the gironde fluvioestuarine system: Behaviour and flow

Abstract Major cadmium contamination of molluscs was discovered in the Gironde estuary. Studies were then undertaken on biota and on particulate and dissolved phases. Biota was studied by monitoring populations of oysters and mussels transplanted from uncontaminated areas into the Gironde. Studies on particulate and dissolved phases were carried out within the estuary, on the inner shelf, in Marennes-Oleron Bay, and in the drainage basin of the Gironde. It appears that: (i) the estuarine particulate stock, with its long residence time, plays a part in particulate-dissolved transformation, and thus has an effect on chemical conditions in the lower estuary and the coastal zone; (ii) the dissolved cadmium concentrations downstream can explain the concentrations measured in the oysters; (iii) the contamination is recent, and originates from the drainage basin; (iv) a geochemical cadmium budget in the Gironde has been formulated and is discussed.

Spatiotemporal changes in cadmium contamination in the Seine estuary (France)

Cadmium (Cd) is among the major contaminants in the Seine estuary. In the biota, the RNO (Réseau National d’Observation, the French Mussel-Watch) has shown that Cd concentrations in mussels living at the mouth of the estuary are related to changes in inputs to this area of phosphogypsum, a calcium sulphate that is a by-product of the phosphoric acid naturally enriched with Cd. In the water column, Cd concentrations at several key estuary sites show a very marked trend toward decreased contamination in the particles as well as in the dissolved phase. The behavior of Cd in the estuary has been studied between 1991 and 1998 in the framework of the scientific program Seine-Aval. This program has highlighted punctual Cd inputs in the estuarine water column. The partition of Cd between the dissolved and the particulate phase, previously described in various estuaries, is characterized by an intense phenomenon of solubilization in the mixing zone freshwater-seawater, but the colloidal Cd fraction remains low along the whole salinity gradient, about 5% to 10% of the apparent dissolved fraction. Although the decrease of inputs induced a fall of Cd concentrations in the water column, laboratory experiments show that the estuarine particles are far from being exhausted in Cd. Despite continuous efforts to reduce the urban and industrial inputs into the estuarine and coastal waters, the Seine estuary still remains very contaminated by Cd.

Trace metal concentrations in the North-western Mediterranean atmospheric aerosol between 1986 and 2008: Seasonal patterns and decadal trends

Climatic and anthropogenic changes are able to engender modifications in the aerosol composition at different geographical and temporal scales. The present study addresses this question for the trace metal concentrations (TM=Al, Fe, Mn, Co, Ni, Cu, Pb, Cd and Zn) of aerosol from the North-western Mediterranean coast of France (Cap Ferrat, nearby Nice) between 1986 and 2008. From seasonal variations (2006-08) and decadal trends (1986-2008) of TM concentrations, three groups of elements can be distinguished. They consist of different aerosol sources: crustal-derived elements (Al, Fe, Mn and Co), trace metals of anthropogenic origin (Pb, Cd and Zn) and a third, intermediate, group of trace metals that presented both anthropogenic and natural/crustal influences (Ni and Cu). Reproducible seasonal patterns were observed for crustal and intermediate elements with highest concentrations between May and November, while anthropogenic trace metals did not show a pronounced seasonal cycle. Nevertheless, highest concentrations of anthropogenic trace metals occurred mostly in autumn/winter. Aerosol concentrations of anthropogenic TMs decreased remarkably over the last two decades, while crustal trace metals did not show any evolution. Nickel and copper aerosol concentrations remained constant, as well. Lead concentrations decreased from 1986 (29.34 ng m(-3)) to 2008 (3.33 ng m(-3)), overall by 90%. Cadmium and zinc aerosol concentrations decreased by 66 and 54%, respectively, between 1998 and 2006-08, from 0.27 to 0.09 ng m(-3) and from 23.9 to 10.9 ng m(-3), respectively. These findings demonstrate the response of the atmospheric environment to the implementation of antipollution policies. Possible changes of trace metal emissions sources and local influences are discussed.

Long-term records of cadmium and silver contamination in sediments and oysters from the Gironde fluvial-estuarine continuum - Evidence of changing silver sources

The Gironde fluvial estuarine system is impacted by historic metal pollution (e.g. Cd, Zn, Hg) and oysters (Crassostrea gigas) from the estuary mouth have shown extremely high Cd concentrations for decades. Based on recent work (Chiffoleau et al., 2005) revealing anomalously high Ag concentrations (up to 65 mg kg(-1); dry weight) in Gironde oysters, we compared long-term (~1955-2001) records of Ag and Cd concentrations in reservoir sediment with the respective concentrations in oysters collected between 1979 and 2010 to identify the origin and historical trend of the recently discovered Ag anomaly. Sediment cores from two reservoirs upstream and downstream from the main metal pollution source provided information on (i) geochemical background (upstream; Ag: ~0.3 mg kg(-1); Cd: ~0.8 mg kg(-1)) and (ii) historical trends in Ag and Cd pollution. The results showed parallel concentration-depth profiles of Ag and Cd supporting a common source and transport. Decreasing concentrations since 1986 (Cd: from 300 to 11 mg kg(-1); Ag: from 6.7 to 0.43 mg kg(-1)) reflected the termination of Zn ore treatment in the Decazeville basin followed by remediation actions. Accordingly, Cd concentrations in oysters decreased after 1988 (from 109 to 26 mg kg(-1), dry weight (dw)), while Ag bioaccumulation increased from 38 up to 116 mg kg(-1), dw after 1993. Based on the Cd/Ag ratio (Cd/Ag~2) in oysters sampled before the termination of zinc ore treatment (1981-1985) and assuming that nearly all Cd in oysters originated from the metal point source, we estimated the respective contribution of Ag from this source to Ag concentrations in oysters. The evolution over the past 30 years clearly suggested that the recent, unexplained Ag concentrations in oysters are due to increasing contributions (>70% after 1999) by other sources, such as photography, electronics and emerging Ag applications/materials.

Imposex and butyltin concentrations in snails from the lagoon of Bizerta (Northern Tunisia)

Abstract Imposex and butyltin concentrations were assessed in Hexaplex trunculus, Conus mediterraneus, Cyclope neritea and Nassarius mutabilis from Menzel Jemil, and H. trunculus and Stramonita haemastoma from the Bizerta channel. All females of the five species exhibited the characteristic development of male sex organs (penis and/or vas deferens). In Menzel Jemil, H. trunculus and C. mediterraneus exhibit similar imposex levels and were most affected (VDS reading 3–4). The development of a bud penis or a vas deferens sequence behind the right ocular tentacle was reported in Cyclope neritea and N. mutabilis (VDS 1). The concentration of tributyltin (TBT) was similar for the four species. The monobutyltin (MBT) was only detected in C. mediterraneus while the dibutyltin (DBT) was found in all gastropods at similar proportions as TBT. In the Bizerta channel, imposex levels were similar in both H. trunculus and S. haemastoma but imposex degree was higher in H. trunculus. This finding was confirmed by higher TBT concentration recorded in female of H. trunculus. These results suggested that H. trunculus is the more suitable bioindicator for monitoring TBT pollution.

Estimation of the abundance of the cadmium resistance gene cadA in microbial communities in polluted estuary water

We describe herein a molecular method for estimating the abundance of the cadA gene, which encodes a Cd2+/ATPase protein transporter, in bacterial DNA extracted from samples of environmental water. Competitive polymerase chain reaction (cPCR) may be the most appropriate technique for assessing the prevalence of the cadA gene in microbial communities in highly heterogeneous and polluted environments, such as the Seine estuary (France). We describe the development of this method: (i) the choice of two specific primers, based on the sequences encoding the cadmium binding site and the ion channel domains; (ii) the construction of a competitor sequence and assessment of its amplification efficiency; and (iii) the estimation of the copy number of the cadA gene. The cadA content in the bacterial community is expressed as the number of gene copies per ng of total DNA extracted, which is independent of the DNA extraction yield. This molecular procedure was improved to analyze cadA levels in bacterial DNA extracted from estuary water accidentally contaminated with cadmium. Results revealed a subsequent increase in the copy number of the cadA gene in the microbial community.