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5B a - RA: Ranking and Chemical Specific (TU6/9) Mixtures of pesticides: development of a gis-based methodology to asses the ecotoxicological risk for surface water at a river basin scale. Sala, Serenella1, Verro, Roberto 1, Finizio, Antonio 1, Vighi, Marco 1, Auteri, Domenica2, 1 Environment and Landscape Departement - University of Milan Bicocca, Milano, Milano2 International Centre for Pesticide Safety, Busto Garolfo, Milano, Italy ABSTRACT- Ecosystems are seldom exposed to individual chemicals. Usually, they are subject to emissions of several potentially dangerous substances in combination, e.g. this occurs for pesticides in agricultural areas. A procedure has been developed to asses the site-specific risk from mixtures of pesticides used on a given crop, for aquatic ecosystems at a river basin scale. Models to predict environmental exposure as well as spatial and relational databases were integrated into GIS to map spatial distribution of results, taking into account the territorial variability of significant parameters. To evaluate surface water pollution, two main processes were taken into account: drift, occurring during pesticide application, and runoff, linked to a rain event after the application. Input data for drift and runoff models were substituted with geographical layers of parameters to take into account their spatial variability for calculating and mapping PECs (Predicted Environmental Concentration) for each pesticide . Using acute toxicity data for organisms, representative of the aquatic ecosystem (algae, Dapnia and fish), ETRs (exposure/toxicity ratios = PEC/EC50) were calculated for individual chemicals. ETRs were then used to calculate a risk index for the mixture, by means of a suitable algorithm. In the further step of the procedure an ecological characterization of the exposed ecosystem is performed and organized into geographical layers. The characterization is based on: A. estimation of the naturalistic vocation of water bodies based on their attitude to be a potential habitat for species with different sensitivity; B. assessment of the ecological status of water bodies derived from biological monitoring (EBI: Extended Biotic Index). The comparison between potential vocation, actual ecological status and potential risk maps, will provide a site-specific risk map for the pesticide mixture. This result is particularly important to develop guidelines at a suitable scale for decision making authorities, e.g. at watershed level. Key words: surface water risk assessment, mixtures of pesticides, GIS, river basin scale |
