Avaliação espaço/temporal e influência da composição sedimentar na distribuição dos agrotóxicos mais utilizados na mesorregião do Rio Jaguaribe - Ceará

Abstract

The Jaguaribe River estuary is located on the semi-arid coast of the Brazilian Northeast. Due to the presence of the river and the irrigated perimeters implanted in the region, the conditions are favorable to agricultural practices and with this, agrochemicals have become a source of pollution in this region. The sediment quality was evaluated by means of 15 surface points and two sedimentary records distributed along the river. The sediments were included in the concentration of 14 pesticides (ametrine, atrazine, bifenthrin, carbofuran, cyfluthrin, cypermethrin, chlorothalonil, chlorpyrifos, deltamethrin, malathion, metolachlor, methyl parathion, permethrin and propanil), granulometry, organic matter, acids fat (pH and salinity, only non - surface sedimentation) and in the evaluation of hydrogeochemical indexes, beingthe quantitative data integrated through Spearman's non-linear regression and mass inventory. In the case of sedimentation, sediment fractions were dated. The method of extraction and the validation of the chromatographic method were effective for the study, presenting linearity, repeatability and recovery. The sediment of the region presented its sandy granulometry and the contents of organic materials, PJ9, PJ12 and P14 were characterized as different by silt-clayey granulometry and the largest by organic matter. An evaluation of hydrogeochemical indexes pointed out a balance relation of the hydrochemical and geochemical parameters with the compounds. The results evidenced the alteration of the quality of the sediments along the river, which are degraded by the presence of 12 different pesticides. As the highest concentrations of pesticides were the pyrethroids with the highest sum in the points PJ9 and PJ14 (365,23 and 387,88 ng.g-1, respectively). The concentrations of pesticides in the fluvial zone were 216, 91 ng.g-1 and in the estuarine zone of 325, 44 ng.g-1, characterizing the estuarine zone, which were characterized as hydrochemistry of the environment, as an environment conducive to accumulation of pollutants. Regarding the dates, in the majority of the classes of pesticides analyzed, the first concentration data followed historical facts of use, that is, during the 1950s the first records of the presence of these contaminants were detected, and from the year of 1970 there was an increase in concentration. During this period, the perimeter of the crop tray was implanted that provided a new agricultural production. However, in the most recent layer there was a decrease in concentration, with a shortage of water as an agricultural conservation state in the region. A geochemical evaluation resulted in different results between the two sedimentary records. The mass inventory indicated values of the total mass of the pesticide sum total were 6.44 to 90.5 t in the surface sediment, from 2.41 to 307.3 t in the core 1 and from 21.02 to 137.4 t in the core 2. The calculated values suggested that fluvial and estuarine systems are affected by the contamination of compounds from agriculture.