Aspectos da interação do homem com pesticidas no ambiente: focando a cotonicultura e com ênfase às bordas do Alto Pantanal, Mato Grosso, Brasil

Abstract

The interaction man-pesticide-environment (M-P-E), in cotton areas was characterized and, a laboratorial study on mobility of the pesticide parathion methyl (PM) into soil columns was developed. Antropic impacts and risk indicators of environmental contamination by pesticides and risks to human health were identified (RCDPEH). This study was carried on in two cotton communities (Facão - C1 and Barra Nova - C2), municipality of Cáceres, at the High Pantanal borders, Mato Grosso state (MT), Brazil, during six harvest periods (1992-97). For the characterization of the MP- E interaction, data were collected with support of the service of assistance to the cotton farmers of MT, as well as through perceptions in situ. Assays on mobilization of pesticide residues were carried on in laboratory using columns filled with top soil from three topographical positions (Pi=1,2,3) with three depths (Ei=1,2,3) collected in cotton farms (Gossypium hirsutum L.) of two communities (Ci=1,2). PM was applied at the top of soil columns and leaching was induced in three time intervals (ti=0,1,2). The percolate was collected to analyze PM residues, using gas chromatography with termoionic detector N/P (CG 500) and an integrator processor (CG 300). Results showed that the characteristics related to the M-P-E factors and their interactions can also consist in risk indicators (RCDPEH). These indicators expressed in terms of greater (r1) and lesser risk (r2) showed that the two communities were similar in the factor pesticide (P: r1 = 40,5 %), but distinct in the factors man (M: C1, r1 = 48,2 % > C2, r1 = 33,2 %), environment (E: C1, r1 = 49.1 % < C2, r1 = 59,0 %) and in the interactions of these three factors (M-P-E: C1, r1 = 45,6 % < C2, r1 = 53,9 %). The communities (C1, r1 = 44,57 % < C2, r1 = 47,2 %) as well as the six considered harvest periods (1995 harvest, r1 = 34,7 % < 1992-94 and 1996-97 harvest periods, r1: ranging from 37,6 % to 41,5 %) behaved differently in relation to the factors as a whole and to their interactions. The laboratory assays indicated that PM residues can leach in soils columns, but small amounts reached depths higher than 3 cm. Soil with higher organic matter (OM) content showed reduced leaching of PM residues. Different amounts of residues of PM mobilized through soils columns, as a function of factors Ci, Pi, Ei and ti, can be due to soil characteristics affected by OM. Therefore, well managed soils, even if sandy, but with adequate OM contents, present low risk of groundwater contamination with PM residues, except if the water table depth is low. The variations in the risk indicators (RCDPEH) resulted from the dynamics of the M-P-E interaction. Therefore, the risks are likely to being minimized through the adequate technical training of the people who work with pesticides. In this context governmental, non-governmental structures and the specialized technologies can reach the agriculturist through training, assistance, monitoring and inspection of the practical routine; thus protecting the Pantanal ecosystems.