Eutrophication and sediment-water exchange of total petroleum hydrocarbons and heavy metals of Hashilan wetland, a national heritage in NW Iran.

The heavy metal(loid)s concentrations in water and sediments were analyzed in the Hashilan wetland to assess the spatial distribution, pollution status, fate, partitioning, and ecological risk and also to identify the heavy metal(loid)s sources in sediments using PMF (Positive Matrix Factorization) and APCs-MLR (absolute principal component score-multiple linear regression) receptor models. According to the pollution indices, (Ni, Cu, Cr, Mo), and (Zn, Cr, and Cu) are considered the most important pollutants in sediments and water, respectively. Ni, Cr, and Cu are the main contributors to ecological risks in sediments of some stations. The potential ecological risk assessment proposed low ecological risk in water of the study area. Higher distribution coefficient (K p ) values of Ni, Cr, Mn, Cu, Co, Pb, As, and Zn indicated the majority of these heavy metals present in the sediments; whereas, the majority of Cd concentration occurs in water. PMF and APCs-MLR results indicated the natural sources were the main factors affecting the concentrations of Ni, Cr, Zn, Al, Co, Fe, Pb, As, Cd and somewhat Cu. Mixed natural and agricultural activities are the main sources of Mo, and somewhat Cu. According to the results, there is low pollution of TPH (total petroleum hydrocarbons) in the sediment samples. Also, phosphate (PO 4 2- ) and nitrate (NO 3 - ) concentrations were below the recommended permissible limits at all sampling sites except the S8 station for NO 3 - .