Friday, April 25, 2008

Mapping pesticide contamination risk

A new computerised tool helps regulators identify water sources at risk of pesticide contamination. The tool can be used to produce maps indicating water bodies at risk of contamination by taking into account: adjacent land-use, the concentration of pesticides in the environment and biological indicators of contamination. Protection of water resources is a key priority for the EU and water bodies located near land used for crop production are at particular risk of contamination from pesticides. The Water Framework directive (WFD)1 sets the objectives for water protection and requires the development of site-specific tools to assess pollution risks and enable best management practices that protect the environment. The new tool, developed as part of the ALARM project2, aims to do just that.

The ALARM (Assessing LArge-scale environmental Risks with tested Methods) Project aims to develop and test methods for the assessment of large-scale environmental risks. Within this project researchers have developed a tool to assess the risk to water from pesticide contamination. Pesticides (a collective term for insecticides, herbicides and fungicides) can enter surface- and ground-water as a result of runoff from crops or due to spray drift during pesticide applications. In a case study, using a Geographic Information System (GIS)-approach, researchers investigated the risk of water contamination and of four different herbicides and one insecticide in Italy's Lombardia region. GIS is a computerised system that analyses data and displays it in map form.

Risk maps were produced by calculating predicted environmental concentrations (PEC) of pesticides, due to runoff or drift, and quantifying risk by assigning values to the effects of exposing a variety of aquatic organisms to the pesticides. Values varied depending on the ability of each species to recover from exposure.

A measure of aquatic 'ecological quality' was estimated using the Extended Biotic Index (EBI). Specifically designed for organic pollution and oxygen depletion, the EBI gives an indication of ecological quality by examining the variety and numbers of insects, crustaceans, molluscs and worms, living at the lowest level of a water body (the 'Benthic zone').

These data were integrated in the GIS, along with land-use information, geographical distribution of pesticides (via runoff or drift) and hydrology3 data. This produced maps that used colours to indicate which water bodies in the region were at most risk from contamination. Areas at risk changed depending on the chemical and ecotoxicological properties of each pesticide.

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