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Biomonitoring of anthropogenic pollutants in coastal areas

Final Report Summary - BIOPACA (Biomonitoring of anthropogenic pollutants in coastal areas)

he study area, located in North-Western Mediterranean, has been chosen to monitor water quality over a period of 3 years (2007-2010), especially by considering the chemical pollution. In this area, a strong anthropogenic pressure is causing release of various contaminants, mainly heavy metals from harbour activities, and organic contaminants from the rivers and from Golfe-Juan city sewage. Following the commissioning of a new wastewater treatment plant with secondary (biological) treatment, 11 stations were selected in the bay in order to follow over a period of 3 years the evolution of concentrations of heavy metals and eight isomers of anionic LAS (linear alkylbenzene of Sulphonate) in sediments, in water (dissolved fraction) and in the Mediterranean mussel (Mytilus galloprovincialis). This work was carried out in collaboration with the Lyonnaise des eaux, that is responsible for wastewater treatment of Golfe-Juan city, and the Agence de l'eau Rh?ne Mediterran?e Corse that is the regional agency responsible for water quality.

The evolution of the condition index observed in mussels from the West to the East stations indicates an enrichment of the particle concentration in seawater. It is therefore likely that the Western stations were exposed to seawater entering the bay, mainly the Ligurian-Proven?al current. Stations located further east inside the bay are gradually under the influence of contaminated water, coming from rivers, plus locally specific particle sources from urban effluents or discharges of port activities.

The overall results obtained in this work clearly indicate a singularity of the station located at the west part of the bay of Golfe-Juan (in the channel between Golfe-Juan bay and Cannes Bay) and seems rather exposed to water masses coming from the Bay of Cannes. This station present a chemical signature different from the neighboring stations located in the bay of Golfe-Juan, which suggests that the transfer of water by the channel connecting the two bays is generally limited. However, it has been observed an important water transfer from the Bay of Cannes in November 2009. After such an event, chemical signature in these stations are similar. The contaminants inputs from Cannes Bay waters should not be underestimated when studying water quality in Golfe-Juan Bay.

Golfe-Juan Bay, can be discribed as a typical urbanised bay. Two souces of pollution have been investigated: urban and industrial activities, the latter being caused mainly from harbour activities. Both types of pollution can be described as low level of impact and were limited in time and space.

Considering heavy metals, 2 areas in the bay (South-West and North of the bay) have been identified to be impacted by harbour activities (mainly from boat maintenance). High concentrations of Pb, Cu and As were detected in mussel tissue and water. Stations located east of the bay do not present similar contamination, illustrating the localy limited impact of heavy metal sources.

Considering LAS (anionic surfactant coming from detergent), it has been observed a low level but global contamination of sediments, water and exposed mussels. Some differences were observed localy, especially in sediments around the waste water discharge. LAS concentrations measured in mussels and passive samplers was decreasing over time in this area, showing a good efficiency of effluent treatment, probably due to the biological treatment implemented in the wastewater treatment plant. But LAS concentration in sediments remain constant, reflecting the long-term accumulation of these compounds and low degradation process. It would be interesting to study the sediment remediation for longer periods.

The rivers seem to be a LAS source in the bay because of the urban effluents discharge from upstream cities. An overview of the effectiveness of treatment and measurement of contamination levels of the water along these rivers would help to estimate the importance of this LAS source in the global contamination of the bay.

The presence of a high proportion of long-chain isomers in sediments and in mussels confirm the high degree of affinity of these molecules for the organic matter. This is due to the hydrophobic characteristics of the carbon chain. These compounds have a higher toxicity than the conventionally observed mixture in the environment and can therefore participate in the overall toxicity of the environment.

This work has allowed us to characterise the areas exposed to different sources of pollution. If levels remain low, it is interesting to observe global contamination of the bay. The three types of samples (passive samplers, mussels and sediments) can provide additional information and should be considered simultaneously. This work should be extended to the French Riviera coast, which undergoes a strong anthropogenic impact and should be used as a monitoring program in order to evaluate the ecological status of coastal area, that is asked in the MSFD, and particularly in descriptor 8 focused on contaminants.

It would be interesting to study the atmospheric transport of contaminants, including the formation of marine aerosols that settle on the coast. It would also be interesting to model the global cycle of these contaminants taking into account sediment transport and exchange between the particles and the water column to measure the flow of these chemicals.

Knowing that we have observed urban contamination in the bay, it would be interesting to measure the level of other contaminants from human activities, including emerging chemicals, yet little studied, such as drugs and personal care products, used in their active ingredients. Very little information exists on these substances and the study of their level of contamination on the coast would take into account their impact and consider for inclusion in the list of substances to be monitored in the context of good ecological status.