Compostos organoclorados e organofosforados no sedimento do Rio Parnaíba

Abstract

The use of pesticides is due to the search for greater agricultural productivity; however, it generates problems of contamination and significant implications for public health. The aquatic sediments work as environmental archive and can be used for the evaluation of anthropic contamination, since they have a large adsorptive capacity. The Parnaíba River Basin emerges in the new agricultural frontier of Brazil, which comprises the states of Maranhão, Tocantins, Piauí, and Bahia, named Matopiba. Thus, this research aimed to evaluate the quality of the Parnaíba river sediment considering the concentrations of organochlorine and organophosphorus compounds, as well as to determine its ecological risk. Four collections were carried out over a year in 11 different points of the river with the aid of a Peterson dredger. The QuEChERS methodology was employed to the extraction and the quantification of the compounds, and the reading was performed on a gas chromatograph attached to a mass spectrometer. Regarding the organochlorine compounds, the compound p,p'-DDE obtained the highest representativeness, with 38.6% of contaminated samples, but the pesticide p,p'-DDD reached the highest concentration, at the P5 point, with 2.035 ppb. For the organophosphates, the Disulfoton is worth mentioning, since it presented a 40.9% representativeness of the contaminated samples; however, the compound Azinphos methyl obtained the highest concentrations, varying from 2.858 to 2.861 ppb. Regarding the ecological risk, out of the organochlorine compounds, the pesticide p,p'- DDD showed a sample with a concentration above TEL, 2.03 ppb, indicating that adverse effects might occasionally occur. For the selected organophosphates, Disulfoton presented a risk factor with significant potential for adverse effects on biota. Therefore, it is necessary to monitor the use and application of pesticides in the environment along the Parnaíba river basin, in order to protect natural resources and environmental quality.