Heavy metals contamination of a watershed in caetes by the use of agrochemicals
Sommaire de l'article
To evaluate heavy metals contamination of soil, sediments, water and plants of the Caetes watershed, in Paty do Alferes, RJ, Brazil, by the use of agrochemicals, samples from two areas with different declivities (25% and 45%) were analysed, in 1996, for total contents of Cd, Co, Cu, Mn, Ni, ph and Zn. The results for the soils under pasture (lately horticulture) showed higher heavy metals contents in comparison to the brushwood area. However, these contents didn’t reach the critical levels for soils, and these elements were present in chemical forms of low disponibility for plant absorption, as it was seen in the very low levels of heavy metals in the samples of tomato (Lyropersicum esculentum L.), green pepper (Capsicum annuum L.), cabbage (Brassica oleracea L.) and cucumber (Cucumis sativus L.). The behaviour of the heavy metals in the sediment samples were the same of the soil samples, being these elements distributed, in higher percentages, in the residual, bonded to Mn and Fe oxides and bonded to organic matter fractions. The water samples from the stream and dam showed higher levels than the international standards for Cd, Pb and Mn.