Pesticide volatilization and exposure of terrestrial ecosystems

Field experiments in cereals were carried out by herbicide and fungicide post emergence application in spring and by insecticide and fungicide treatment of barely before ripeness in summer. The pesticide concentrations in plants and soil of the target area and in the air above the field and concentrations in different distances to the treated field in front of and behind the hedge situated downwind were determined. After treatment in spring fenpropimorph occurred in the air in concentrations up to 1.3 mug/m3; parathion-ethyl reached concentrations up to 3.3 mug/m3 in the air after application in summer. The pesticide discharge in the main wind direction could be estimated assuming a pesticide transport with the average downwind wind speed and an average pesticide concentration at the field edge. While the total amounts of herbicide and fungicide discharges were low during the treatment in spring, the downwind discharge of the insecticide parathion-ethyl was 16-17 per cent of the applied amount in summer 1995. To assess the exposure of terrestrial ecosystems the pesticide uptake by standardized grass cultures and of leaves of the natural hedge situated downwind was determined. It was demonstrated that both, fenpropimorph uptake by plants after application in spring and chlorothalonil uptake by plants after application in summer resulted in high concentrations in non target plants. Here, the climatic parameters play an important role. However a significant accumulation of fenpropimorph and chlorothalonil did not take place in the grass cultures. As fenpropimorph concentrations in the target plants were low and decreased rapidly, 6-10 h after application no significant differences between the fenpropimorph concentrations in the target plants and in the grass cultures were determined.