Estudo do comportamento de metais pesados nas frações < 2 μm e < 63 μm nos sedimentos de fundo do rio Arienga – Barcarena – Pará.

Abstract

The bodies of surface water in large urban centers and industrial have been under increasingly the impact of human action. What cause other environmental problems among the input content of heavy metals that accumulate in bottom sediments, causing serious damage to the aquatic system. In order to study the level of contamination of bottom sediments of the river Arienga important river city Barcarena – PA, and evaluate possible contamination by toxic wastes from the steel industry the industrial hub of the city were analyzed for textural, mineralogical and chemical in nine samples collected along the river and one at the mouth of the creek Bacabal. The results of the sediment grain size showed the predominance of silt over the others (sand and clay). Only the first three points collected by virtue of proximity to the mouth, was the predominant sand fraction. O mineralogical study of samples revealed an essentially quartzose fraction < 63 μm and the presence of kaolinite, smectite and illite in the fraction < 2 μm. The organic matter analysis showed an average of 5.90±1.87 mg.Kg-1. Analyses for determination of trace elements was carried out both in the fraction < 63 μm and in the fraction < 2 μm. It was observed that there was a considerable enrichment of heavy metals in the finer fraction of sediment (< 2 μm): Ni increased from an average of 11.10 ± 1.89 mg.Kg-1 in the fraction < 63 μm for a average of 37.94±1.94 mg.Kg-1 in the fraction < 2 μm; Pb increased its average 14.61±2.37 mg.Kg-1 to 46.02±2.49 mg.Kg-1, the Zn concentration increased from an average of 41.60±6.33 mg.Kg-1 to 107.40±7.78 mg.Kg-1, the Cu concentration increased an average of 12.38±2.28 mg.Kg-1 to 30.37±5.70 mg.Kg-1, for V, Co and Ba increase in the average concentration was respectively of 92.10±9.35 mg.Kg-1, 9.08±1.45 mg.Kg-1 and 344.70±46.76 mg.Kg-1 to respectively 140.80±7.19 mg.Kg-1, 16.82±1.58 mg.Kg-1 and 428.50±36.81 mg.Kg-1. Getting a clear affinity for all metals analyzed with the clay. The determination of the Index of Geoaccumulation (IGeo) showed that the river Arienga, although situated in an area of risk, isn’t contaminated to the metals studied, and therefore the values found were probably due to local geology.