Comparison of various digestion and extraction procedures in analysis of heavy metals in sediments

Sediment analysis is very important in investigations of the heavy metal burden in the environment. In the present work various digestion and extraction procedures were evaluated in order to assess the extent of contamination with heavy metals in sediments from the Moste hydroelectric reservoir. Total acid dissolution, aqua regia digestion and acetic acid extraction procedures were applied to samples. Zn, Cd, Pb, Co, Ni, Cu and Cr were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS) under optimized measurement conditions. A comparison of total acid dissolution including hydrofluoric acid (HF) treatment and the aqua regia soluble fraction was made to estimate the applicability of aqua regia digestion in analysis of total metal concentrations in sediments. In general, good agreement of the results was observed for Co, Pb, Cu and Zn, however for Cr, Ni and Cd significantly lower results were obtained in the aqua regia soluble fraction. In addition, an extraction procedure using 25% v/v acetic acid was applied for estimation of the extent of contamination with heavy metals originating from anthropogenic activities. The results indicate that the sediments upstream of the reservoir are not contaminated, while the sediments from the hydroelectric reservoir shows a significant anthropogenic input of Ni, Zn and Pb, which corresponds well with pollution sources.