“Agrotóxicos Urbanos”: ocorrência, partição ambiental e ecotoxicologia - Rio Ceará, Fortaleza- CE, Brasil

Abstract

The household cleaning products, also known as "urban pesticides", are chemical products for cleaning, disinfection and disinfestation in urban environments. They are used in order to control endemic diseases and economic losses caused by urban pests. These products are formulated based on active ingredients considered pesticides, known as harmful chemicals to human health and to the environment, however the legislation contemplates it distinctively. These AgU can reach and contaminate areas of high economic, social and environmental importance, such as estuaries and mangroves, leading to degradation of natural resources in these environments. This study aimed to evaluate the occurrence, spatial distribution, transport factors and possible sources of AgU, arising from the urban pest control, in the sediment and the water throughout the Ceará River, located in the metropolitan area of Fortaleza, Ceará, Brazil, which has limited water resources, due to the influence of the semiarid climate. The sedimentological characterization included the determination of particle size, organic carbon content, matter organic and humic substances. The hydrochemical properties of the Ceará River were collected in situ by multi-parameter probe. The AgU were extracted from water by liquid-liquid extraction and from sediment by solid-liquid extraction. The AgU were detected and quantified by gas chromatography-mass spectrometry. In order to evaluate the toxicological risk of malathion, acute toxicity bioassays were performed using mysids. The points located in the estuary and river area had predominance of sand and muddy sand, respectively. The sediments of the Ceará river had low levels of organic matter, ranging from 1.90 to 3.62%, and of humification degree, ranging from 0.08 to 1.77. Hydrochemistry characterization showed differences between the two areas studied, with greater contribution of tidal currents in the estuarine zone. The AgU studied (bifenthrin, cyfluthrin, cypermethrin, deltamethrin, imiprothrin, permethrin and malathion) were detected in all water and sediment samples, except bifenthrin which had values below the detection level in water. The AgU cypermethrin, permethrin and deltamethrin showed the highest concentrations in both matrices, ranging from 37.39 to 367.60; 44.49 to 226.45 ng L-1 and 60.99 to 170.56 ng L-1 in water and 270.99 to 623.99; 27.00 to 307.00 ng g-1 and 0.27 to 443.48 ng g-1 in sediment, respectively. The Mysidopsis juniae had high sensitivity to malathion in the acute toxicity bioassays, with lethal concentrations close to the maximum concentrations allowed by CONAMA. The partition study showed that all AgU have their balance shifted to the sediment phase, tending to be more concentrated in the sediment than in water. The relation of the Kd with the abiotic parameters showed that environmental conditions can affect more fate and transport of AgU than their physical and chemical properties. Statistical analysis showed dependence on abiotic parameters in the spatial distribution of AgU. The AgU pyrethroids class distribution were determined by the organic fraction of the sediment which indicates that the process of sorption is the final destination of majority of the compounds in the aquatic environment. This work aimed to support future monitoring policies of these contaminants in aquatic environments.