Sediments as a natural archive and accumulation sink of different materials are indicators to eva‎luate the state of pollution in aquatic environments. Conventional laboratory methods used to survey sediment pollution are usually difficult and time-consuming. The measurement of magnetic susceptibility, that are quick method with less destructive effect, are used to survey pollutants in different environments in recent years. The goal of this study was to investigate vertical changes of some heavy metals and magnetic susceptibility in core sediments of Shakh-Mian and Kooh-Siah located in the delta of Zayandehroud River, at the entrance of Gavkhouni International Wetland. Two sediment cores 131 and 30 cm long, were harvested at the two stations of Shakh-Mian and Kooh-Siah stations, respectively, and the amount of magnetic susceptibility at two frequencies of 0.46 kHz and 4.6 kHz, different physical and chemical parameters (percentage of moisture, raw density, dry density, sediment particle size, organic matter, pH, EC, and Eh ) and concentration of elements (Cd, P, Al, S, Zn, Pb, Ni, Cr, Fe, V, Co, Cu, Mn, and Li) were measured in samples of both sediment cores. Indices of Enrichment Factor (EF), Geo-accumulation Index (Igeo), and Pollution Load Index (PLI) were used to eva‎luate the degree of environmental pollution of heavy metals. The results of Pearson correlation analysis in the Shakh-Mian station showed significant positive correlations between low-frequency magnetic susceptibility with nickel, lead, chromium, cobalt, copper, lithium, iron, aluminum and manganese, silt and clay, pH and organic matter, and significant negative correlations with very coarse sand and coarse sand. While only a significant positive correlation occurs between magnetic susceptibility and manganese in the Kooh-Siah station. The Pollution Load Index also has a significant positive correlation with magnetic susceptibility in the Shakh-Mian station (P˂=0.01, r=0.317). Based on the regression equation obtained between magnetic susceptibility and physical and chemical parameters and elements, the percentage of moisture and metals including lead, lithium, aluminum, and iron at the Shakh-Mian station, and Mn and Eh at the Kooh-Siah station were explained 71.9% and 57.9% of the total changes, respectively. Comparison of different environmental factors such as population changes, number of workshops, crop cultivation area of the Isfahan Province, and meteorological and hydrological drought indices of the Gavkhouni basin during the last seven decades with changes of pollution load index (PLI), element fluxes and magnetic susceptibility in studies samples showed only a direct relationship between the flux of elements with wet periods of the basin. In other words, according to the geo-accumulation index (Igeo) and enrichment factor (EF) which show the lack of sediments pollution in both sediment cores, wet periods have caused more transfer of sediments from the basin to the delta of Zayandehroud River, which is accompanied with an increase in the element flux index.

محمد نعمتي ورنوسفادراني، نوراله ميرغفاري

شمس‌الله ايوبي

محسن سليماني، رضا مدرس