Heavy metal distribution in recent sediments along the Tietê River basin (São Pauro, Brazil)

Copyright © 2012 by The Geochemical Society of Japan. Variations in the aquatic environmental conditions can produce a release of heavy metals from the sediment to the water resulting in an increase of their bioavailability and consequent toxicity (Young et al., 1987; Wen and Allen, 1999). This aspect can be further investigated when the samples are analyzed in recent sediments, allowing a detailed study of heavy metals in association with the bioavailable and residual fractions, involving materials of different origins. The distribution and quantification of heavy metals in river sediments are usually based on concentrations obtained from extraction procedures and compared with the natural background levels (Salomons and Förstner, 1984). The Tietê River, with 900 km of extension, is the longest river of the southeast part of Brazil. Its drainage basin, with a population of nearly 25 million people, is important for food and energy production, with more than ten hydroelectric power plants along the main channel of the river and tributaries. Over the years, with the increased population and consequent development of industry and agriculture, the river water and sediment quality deteriorated. In recent years, attention has been focused to the problem of river pollution related to the presence of heavy metals in dissolved and particulate loads (Mortatti and Probst, 2010). This paper aims to characterize the heavy metal distribution in the recent sediments along the Tietê River (from headwater to the mouth) and evaluate the degree of pollution in the river basin, considering a regional background level. Heavy metal distribution in recent sediments along the Tietê River basin (São Pauro, Brazil)