Risk Assessment of Heavy Metal Hotspots in Surface Water Bodies: A Case Study of Zanjan Province, Iran

Agricultural and industrial activities are primary risk sources of heavy metal (HM) pollution in the water environment. Indices are well-known approaches for assessing HM contamination in the aquatic environment.

Water samples were collected in polyethylene bottles and transported to the laboratory for further analysis. Samples were examined during the winter and spring. The inductively coupled plasma was used to determine HMs concentrations collected from 48 stations. The Wilcox signed-rank test was applied to examine the HMs values in two different months. In addition, Spearman's correlation coefficient was used to examine the relationship between HMs.

Based on the findings of the present study, the HM contents in the analyzed samples showed no high values, except for lead and nickel (15% of samples) in spring. The potential ecological risk indices revealed that about 25% and 41% of samples demonstrated high and significantly high pollution levels in spring, respectively, while these values declined to 37% and 8% in winter. Only one sampling point showed risk characterization ratio ≥ 1 for zinc in winter. Moreover, the ecological risk of the surface water potentially decreased in the order of water bodies > dry farming > agricultural lands > barren lands areas.

According to the obtained results, the presence of lead and nickel indicated the main anthropogenic sources of HMs in the studied area, especially in the west and south of Zanjan. Anthropogenic inputs of HMs could be related to mining, agricultural, and industrial activities