Resíduos deslocáveis de pesticidas são uma das formas de se estimar a exposição ocupacional do trabalhador rural no seu ambiente de trabalho. Este estudo avalia resíduos deslocáveis de metamidofós em folhas, frutos e solo em cultura estaqueada de tomate (Lycopersicon esculentum Mill), com o objetivo de conhecer o potencial dessa exposição. O experimento constou de quatro tratamentos: uma aplicação de metamidofós na dose simples de 0,6 g L-1 de água de i.a.; uma aplicação na dose dobrada de 1,2 g L-1 de água de i.a.; quatro aplicações na dose simples e testemunha. As amostras foram colhidas decorridos --1, 0, 1, 2, 3, 5, 7 e 14 dias. Os resíduos deslocáveis de metamidofós foram extraídos com solução aquosa de Sur-ten e quantificados por cromatografia de gás. Nas folhas, eles tiveram degradação semelhante nos tratamentos com quatro e com uma aplicação na dose dobrada (1/2 vida de 0,7 e 0,9 dia). No solo, em ambas as doses simples ela foi também semelhante (1/2 vida de 2,9 e 2,7 dias). Os resíduos no solo foram mais persistentes do que nas folhas. Nos frutos, eles foram detectados apenas aos 0 e 1 dia, o que sugere que a degradação neles é relativamente muito rápida.
The measurement of dislodgeable pesticide residues is a way of estimating occupational exposure of farmers in their working environment. This study evaluates dislodgeable methamidophos residues on leaves, fruits and soil in staked tomatoes (Lycopersicon esculentum Mill), with the objective of estimating potential exposure. The experiment consisted of four treatments: application of methamidophos in a single rate of 0.6 g a.i. L-1 water; application of a double rate of 1.2 g a.i. L-1 water ; four applications of a single rate; and control. The first spraying in the four-application treatment was made at the beginning of fruit maturation. The later applications followed a 6-day schedule. Spraying of the treatments with one application was simultaneous to the last spraying of the four-application treatment. Leaf, fruit and soil samples were taken one day before applications, and 0, 1, 2, 3, 5, 7 and 14 days after them. Dislodgeable methamidophos residues were extracted by Sur-ten aqueous solution; extracts were partitioned in a methanol-ethyl acetate mixture, and the residues were quantified by gas chromatography on a flame photometry detector. Foliar residues in the four-application treatment at the single rate and one application at the double rate had similar degradations, with half-lives of 0.7 and 0.9 day, respectively. The behavior of soil dislodgeable residues in the treatments at a single rate (one and four applications) was similar, with half-lifes of 2.9 and 2.7 days, respectively. Residues on soil were more persistent than residues on the leaves. Residues on fruits were detected only for 0 and 1-day old samples. Results show that degradation on tomatoes is relatively fast.
