Contamination, toxicity and risk assessment of heavy metals and metalloids in sediments of Shahid Rajaie Dam, Sefidrood and Shirinrood Rivers, Iran

In this paper, the heavy metals and metalloids (As, Cd, Co, Cr, Ni, Cu, Pb and Zn) levels were studied to investigate their contamination and ecological effects in surface sediments of Shahid Rajaie Dam Lake and two major upstream rivers. Contamination factor and modified degree of contamination values indicate a very low to considerable contamination effects for the studied sediments while pollution load index indicates no pollution (except five stations). The comparison of selected elements concentrations with sediment quality guidelines reveal that the average concentration of As, Cr and Ni in the present sediments is higher than threshold effect level. In addition, Ni shows higher concentration than probable effect level and effect range low values. These sediments based on PELQ and ERMQ calculations, for Cr, As, Cd, Zn, Cu, Ni and Pb are slightly toxic. The result of enrichment factor evaluation similarity to principal component analysis indicates that the main source of Pb, Cd, and Zn for 15.38-42.3 percentages of samples is anthropogenic. PC1 agrees with the measured enrichment factor suggesting a geogenic source for Cu, Mn, As, Cr, Al, Co, Ni and Sc in the sediment samples. Higher positive loadings of P with Ni and Co for a small number of sediment probably indicate amplified concentration due to anthropogenic sources such as application of phosphorus fertilizers in the agricultural lands. High positive loading of Pb, Zn and Cd with organic carbon (OC) and clay reveals a significant role of OC and clay in the dissolution and distribution of Pb, Zn and Cd in the dam's lake sediments. In summary, the present study has provides a practical baseline data for the long-term monitoring of heavy metals pollution in the study area.