A combined soil-atmosphere model for evaluating the fate of surface-applied pesticides. 2. The effect of varying environmental conditions.
Simulations using the one-dimensional nonisothermal model (Reichman et al. Environ Sci. Technol. 2000, 34, 1313−1320). this issue) for pesticides that have been applied to the soil surface revealed that diurnal variation of climatic factors, soil type (silty clay and sand), initial soil-moisture distribution, and pesticide type (parathion, dieldrin, and trifluralin) potentially have major influences on pesticide volatilization rates and persistence. The diurnal variation of water evaporation, which is closely related to the diurnal variation in solar radiation, has potentially significant effect on the diurnal variation of parathion volatility and mobility (low volatility and high mobility). However, the volatilization rates of low-water-soluble pesticides (e.g., trifluralin and dieldrin) are only slightly affected by water evaporation rate. Their migration downward via vapor-phase diffusion reduces their concentration in the soil surface layer and decreases their actual volatilization rates. The limiting...