Concentrations of CU, ZN and MN in bed sediments in watershed with intensive swine production

Abstract

Fertilization of crops with pig slurry is a common practice all over the world. However, due to the high load of pollutants contained in the effluents, the continuous application in agricultural areas can have negative effects on soil, plant and aquatic ecosystems. In this work we quantified the concentrations of heavy metals Cu, Zn and Mn in the bed sediments of an agricultural watershed with intensive swine production of northwestern Rio Grande do Sul, well as evaluate the environmental risks that agricultural activities could be causing the aquatic ecosystem by applying sediment quality guidelines (threshold effect level/probable effect level). The sediment samples were collected along the major channel with low flow conditions. Elemental concentrations were determined by X-ray fluorescence spectrometry on pressed pellets of ground and sieved sediments at ≤ 53 µm. The results showed that the agricultural activities in the watershed are contributing to the enrichment of bed sediment with the metals Cu and Zn. This increase is worrying because these metals have potentially bioaccumulation in the tissues of biota and may affect the distribution and density of benthic organisms.