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1998

Potential denitrification and nitrification tests for evaluation of pesticide effects in soil

Pell, Mikael; Stenberg, Bo; Torstensson, Lennart

Abstract

The acute toxicity effects of 54 pesticides on denitrification and nitrification in soil were studied in the laboratory. Potential denitrification activity (PDA) was assayed with an acetylene inhibition method, during which the specific growth rate constant of denitrifiers (mu(PDA)) could also be determined. Potential ammonium oxidation activity (PAO) was assayed with the chlorate inhibition method. A first screening test of the pesticides at 100 mu g active ingredient (a.i.) g(-1) dry soil (d.s.), revealed that 23% had a significant effect on PDA, 26% on mu(PDA) and 35% on PAO. For denitrification both stimulatory (8-11% of the pesticides) and inhibitory (15%) effects were observed, while effects on nitrification were all inhibitory. In a subsequent dose-response test NOEC, EC(50) and EC(90) were determined for mancozeb (PDA and PAO) and 2,4-DB, ioxynil, maneb, zineb and nitrapyrin (PAO). The NOEC of mancozeb were 1.0 and 0.4 mu g a.i. g(-1) (d.s.) for PDA and PAO, respectively, and the corresponding EC(50) were 7.1 and 2.1 mu g a.i. g(-1) respec-tively. The methods emphasize short incubation periods with relatively short intervals between determination of product formation, thus allowing quantitative measure-ments with kinetic considerations. In addition to being rapid and sensitive, PDA, mu(PDA) and PAO reflect different parts of the bacterial biomass and hence complement each other in the interpretation of test results. Therefore, all three parameters are suitable for inclusion in a test system for assessing effects on the soil environment.

Published in

AMBIO: A Journal of the Human Environment
1998, Volume: 27, number: 1, pages: 24-28
Publisher: SPRINGER