Leaching and degradation of corn and soybean pesticides in an Oxisol of the Brazilian Cerrados

Citation
V. Laabs et al., Leaching and degradation of corn and soybean pesticides in an Oxisol of the Brazilian Cerrados, CHEMOSPHERE, 41(9), 2000, pp. 1441-1449
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
CHEMOSPHERE
ISSN journal
0045-6535 → ACNP
Volume
41
Issue
9
Year of publication
2000
Pages
1441 - 1449
Database
ISI
SICI code
0045-6535(200011)41:9<1441:LADOCA>2.0.ZU;2-O
Abstract
Pesticide pollution of ground and surface water is of growing concern in tr opical countries. The objective of this pilot study was to evaluate the lea ching potential of eight pesticides in a Brazilian Oxisol. In a field exper iment near Cuiaba, Mate Grosso, atrazine, chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, metolachlor, monocrotofos, simazine, and trifluraline w ere applied onto a Typic Haplustox. Dissipation in the topsoil, mobility wi thin the soil profile and leaching of pesticides were studied for a period of 28 days after application. The dissipation half-life of pesticides in th e topsoil ranged from 0.9 to 14 d for trifluraline and metolachlor, respect ively. Dissipation curves were described by exponential functions for polar pesticides (atrazine, metolachlor, monocrotofos, simazine) and bi-exponent ial ones for apolar substances (chlorpyrifos, lambda-cyhalothrin, endosulfa ne alpha, trifluraline). Atrazine, simazine and metolachlor were moderately leached beyond 15 cm soil depth, whereas all other compounds remained with in the top 15 cm of the soil. In lysimeter percolates (at 35 cm soil depth) , 0.8-2.0% of the applied amounts of atrazine, simazine, and metolachlor we re measured within 28 days after application. Of the other compounds less t han 0.03% of the applied amounts was detected in the soil water percolates. The relative contamination potentials of pesticides, according to the lysi meter study, were ranked as follows: metolachlor > atrazine = simazine much greater than monocrotofos > endsulfane alpha > chlorpyrifos > trifluraline > lambda-cyhalothrin. This order of the pesticides was also achieved by ra nking them according to their effective sorption coefficient K-e, which is the ratio of K-oc to field-dissipation half-life. (C) 2000 Elsevier Science Ltd. All rights reserved.