Ecotoxicological risk assessment of chemicals by measurements of nitrification combined with a computer simulation model of the N‐cycle

Abstract

AbstractThe N‐cycle of an Aldicarb‐contaminated [2.5 g · m−2 (a.i.)] soil cover of a newly graded rubble dump was investigated in order to judge the alterations of microbial nitrogen transformations at the ecosystem level. The pesticide reduced the kinetic parameters of nitrification (maximum activity and division rate) markedly, indicating severe damage to the nitrifying population of the soil during the first 16 weeks after its application. The degree of nitrification varied depending on the incubation conditions. Incubations in the field and under laboratory conditions without substrate addition showed negligible effects, whereas incubation with the addition of (NH4)2SO4 led to an intolerable reduction in nitrification.The consequences of these experimental results on the NO3 ‐N and NH4+‐N content of the soil solution were analyzed by simulating the N‐cycle using different sets of parameters (climatic factors, initial conditions). The results indicate that combining field and laboratory studies of microbial populations with a computer simulation model of the N‐cycle improves ecotoxicological risk assessment.