Application of geoaccumulation index and enrichment factor for assessing metal contamination in the sediments of Hara Biosphere Reserve, Iran

Surface sediments from the Hara Biosphere Reserve of the Persian Gulf were collected to evaluate the contamination of metals including Pb, Cd, Ni and Fe. The sediment samples were subjected to a total digestion technique and analysed by atomic absorption spectrometer for metals including Pb, Cd, Ni and Fe. The concentration of heavy metals in the surface sediments was determined in grain size fractions, 2–1, 1–0.25, 0.25–0.063 and <0.063 mm. The highest mean concentration of heavy metals was observed in the <0.063 mm fraction and decreased with increasing size fraction, also metal concentrations in the 0.063 mm fraction represented the next decreasing order Fe>Ni>Pb>Cd. Cd had a higher enrichment factor than the other metals, and the Igeo value for Cd in the most stations was classified as uncontaminated to moderately contaminated and moderately to strongly contaminated. This, combined with the average of Igeo of Cd as 1.36 ± 0.22, suggested that surface sediments of Hara Biosphere Reserve were moderately polluted by this metal. The results also showed that industrial activities around Hara Biosphere Reserve were the most important agents for releasing heavy metals in the area under study. Pearson correlation indicated that there were significant positive associations between Cd–Pb (r=0.523, P< 0.01) in the <0.063 mm fraction.