Are pesticides only a problem from rural areas? The case of a highly urbanised tropical mangrove (Fortaleza, CE, Brazil)

Abstract

ABSTRACT The aim of the present study was to evaluate the occurrence and environmental partition of urban pesticides and the dependence of these compounds on the physicochemical properties of the sediment and water of the Ceará River (fluvial and mangrove regions) located on the tropical coast of northeast Brazil. Surface sediment and water were collected from each site. Dissolved oxygen, pH, temperature, conductivity, depth, turbidity, and salinity were measured in situ. Bifenthrin, deltamethrin, permethrin, imiprothrin, and malathion were analysed in both environmental matrices. An ecological risk assessment was performed using the risk quotient (RQ) calculated from responses of aquatic organisms to the target compounds compiled in the United States Environmental Protection Agency ECOTOXicology knowledgebase (ECOTOX). The highest concentrations were found for the urban pesticides cypermethrin, permethrin, and deltamethrin, 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 in dry weight, respectively. Malathion, cypermethrin, cyfluthrin, and deltamethrin are related to chemical control performed for combatting vectors of diseases. The main sources of permethrin and imiprothrin are household insecticides. Bifenthrin may be related to its use by specialised pest control services. The study of toxic effects and the ecological risk assessment revealed cyfluthrin to be extremely toxic to marine and estuarine organisms, followed by deltamethrin, bifenthrin, cypermethrin, and permethrin, whereas imiprothrin and malathion were classified as toxic and non-toxic, respectively. The urban pesticides investigated in this study were on the same level of magnitude as those found in agricultural areas, except for malathion and imiprothrin, the levels of which were higher due to the fact that these compounds are commonly used in urban pest control.