Sedimentation rate determination and heavy metal pollution assessment in Zariwar Lake, Iran

Metal contents and enrichment factors of ten major trace metals, along with total organic matter, were studied using a 50-cm-long sediment core from Zariwar Lake in Iran. The source of elements (Fe, V, Co, Cd, Al, Cu, Zn, Ni, Cr and Mn) was investigated by chemical partitioning technique as well as cluster analysis. Results of partitioning revealed the anthropogenic portion of metals (%) to be: Zn > Cu > V > Ni > Mn > Cd > Co > Cr. Cluster analysis classified all elements into clusters A and B. The presence of Fe and Al as earth indices in both clusters indicated that all investigated elements likely originate from the lithogenic sources to some extent. Results obtained from the geochemical accumulation index, pollution index, enrichment factor and Hakanson index showed that the sediments were not contaminated and did not exhibit ecological risk. Negligible levels of pollution were seen in terms of Ni and Mn contents. Average sedimentation rate was about 5.6 mm/year according to 210Pb activity through the depth of the core, which is about 5.5 times greater than the ones reported in other freshwater lakes. Considering the lake being small, this increasing trend in sedimentation rate may create short phases of lake sedimentation and degrade the aesthetic quality of this aquatic environment.