Assessment of Metals (Co, Ni, and Zn) Content in the Sediments of Mighan Wetland Using Geo-Accumulation Index

Sediments are inseparable fractions of wetland ecosystems that work as a his-torical archive in the process of recording heavy metal aggregation changes. This study was carried out for assessing Co, Ni, and Zn in sediment samples of Mighan Wetland using geo-accumulation index in 2013. The sediment samples were taken from 11 stations. The samples were subjected to bulk digestion and chemical partitioning and Co, Ni, and Zn concentrations of the sediments were determined by ICP-OES. Geo-accumulation index (I-geo) was used to evaluate the magnitude of contaminants in the sediment profile. The results showed that Co, Ni, and Zn concentrations in the sediment samples were 10.0±0.65-60.0±3.79, 21.0±1.71-42.0±2.80, and 64.0±6.97-263.0±26.13 µg g-1, respectively. Moreover, according to the I-geo values, the sediments’ qualities fell into the unpolluted category. Although at present, sediments of Mighan Wetland are not polluted with heavy metals, disposal of urban and industrial wastewaters into the wetland as well as the settlement of Iran Mineral Salt Company and the establishment of Arak Refinery in the vicinity of the wet-land, can discharge different pollutants especially heavy metals to the wetland and cause irreparable damages in the long run.