Heavy metal concentrations and enrichment of sediment cores: Correlation between geochemistry and geoaccumulation index

摘要

The municipality of Viam?o is located in the metropolitan region of Porto Alegre, state of Rio Grande do Sul. The M?e d'água dam was built in 1962, in order to attend the demand from the Federal University of Rio Grande do Sul, more precisely the Institute of Hydraulic Research. However, due to a lack of urban planning over the past forty years, the dam has caused several environmental liabilities, such as organic contaminants and/or inorganic contaminants. This manuscript addresses an evaluation of the concentrations of the metals zinc and nickel and Geoac-cumulation Index (I_(ge)o), at different depths sampled in sediment cores produced in the watershed that comprises M?e d'água. Four sediment core distributed in the dam were collected in June 2014, by "Piston Core" core sampler. Sediments whose fraction were lower than 63 μm were subjected to chemical analyses regarding the presence and concentration of nickel (Ni) and zinc (Zn). The acid digestion methodology employed was EPA 3050, adopted by the US Environment Protection Agency. The analyses were performed in replicates and two USGS (US Geological Survey) reference materials, namely: SGR-lb and SCO-1 were used for the quality control. Geoaccumulation index (I_(geo)) was developed by Müller (1977) and had widely been used in trace metal studies of sediments and soils (Amin et al., 2009; V.K. Singh et al., 2005). The I_(ge)o was calculated according to the equation (Ig_(eo)= log2* Ca/1.5*Cp) and table 1, aiming to quantify the degree of heavy metal pollution on the M?e d'água sediments.