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Heavy Metal Pollution in Water and Sediment of the Cherat River affected Zirab Coal Cleaning Plant, Mazandaran province, Iran

Ali Esmaeili*

Concentration, origin and fractionation of heavy metals in water and sediment around the Zirab Coal Cleaning Plant (ZCCP) have been investigated in this study. For this purpose, eleven water and sediment samples were collected from the Sheshrudbar (as background) Cherat and Talar Rivers as well as the ZCCP and drainages. Generally, the predominate water type in ZCCP was Ca2+-SO42-; while, in the Cherat and Talar Rivers, and also the ZCCP drainages were Ca2+-HCO3-, Ca2+- SO42-(HCO3-) and Ca2+-HCO3-(SO42-), respectively. Water samples in the ZCCP and its direct drainages tested with a high metal load; whereas samples taken prior to the ZCCP classified as low metal water. The highest metal enrichment was detected for Cd, Cu and As in around the ZCCP and drainages that were categorized in moderate (for Cu and As) and extreme (for Cd) contamination. According to modified contamination degree, the river’s sediments were classified with a very low degree of contamination, whereas the ZCCP and drainages fall into a moderate to high degree of contamination. The sequential extraction analysis results revealed that most metals before and after the ZCCP were bimodal and mainly occur in silicate and sulfide bounds as residual fraction. Whereas, the metals in the ZCCP sample included three modes with an increase of organic bound fraction. The metal mobility factor in the ZCCP sample demonstrate that the Cd, As and Cu were high mobility with high percent of occurrences in water soluble and exchangeable fraction.