THEMATIC MAPS FOR REGIONAL ECOTOXICOLOGICAL RISK ASSESSMENT - PESTICIDES

Frequently, decisions and/or recommendations on various regional scale s on the application of pesticides have to be made by authorities, ins titutions and individual persons. Therefore, it is advisable to identi fy and rank the ecotoxicological risk of a pesticide under special con sideration of the respective regional conditions. As a result thematic maps can be designed identifying and ranking different vulnerable reg ions with respect to groundwater contamination, permeable soils and ar eas at high risk for terrestrial and aquatic organisms. Also, differen t pesticides can be ranked with respect to their ecological risk for a specific area under consideration. Such a 'regionalization' of the ec ological risk can be approached as follows: (1) Small-scale scenarios being representative for the regions under consideration have to be se lected and characterized. The characterization has to comprise: soils (types, genesis, thickness, permeability to subsoils), topology (e.g., slope), climatic conditions, surface water (occurrence of ditches, po nds and creeks), portion of the drained area, portion of land under ag ricultural use, typical cultures and types of pesticides, application rates and frequency. (2) The representativity of the selected scenario s for the region under consideration has to be determined. (3) For the various regions predicted environmental concentrations (PEG) are asse ssed for the different paths of entry (mainly spraydrift and runoff), the different ecological systems, the different durations of the impac t (fate consideration). If appropriate, sensible average values (e.g., for an average distance of the aquatic system from the target area) h ave to be agreed upon. (4) Determination of concentrations of no envir onmental concern (NEC). (5) Formation of risk quotients (PEC(i)/NEC(j) ) for the each path of entry, ecological system and duration of the im pact and subsequent aggregation of the quotients on a previously defin ed scale. The result is not an absolute risk, but the ranking of the r egions as stated above can easily be performed.