TRACE ELEMENTS IN URBAN SEDIMENTS AND THEIR GUIDELINES EVALUATION

Abstract

Water resources have been severely damaged by hydrologic alterations and especially by pollutants transferred from the urban watershed. This paper presents results of total acid analysis of suspended sediments in an urban watershed and establishes comparisons with three different sets of Guidelines and local background results. The watershed studied has an area of approximately 0.83 km², and is located in the Porto Alegre metropolitan area, the largest city in southern Brazil. Suspended sediment samples were collected in the watershed outlet from 2003 to 2006. Total acid digestion analyses (HCl – HF – HClO4 – HNO3 ) were performed to obtain the total concentrations of Co, Cd and As. The results of the acid analysis of the suspended sediments and the background values demonstrated the existence of an enrichment process due to the presence of pollutants in the environment, such as the metals Co and Cd, and the variability of the Guidelines.