Heavy metal pollution in surface sediments of Ghareh-Aghaj River, one of the longest perennial rivers in Iran

River heavy metal contamination (HM) is a serious growing concern across the globe. In Iran, particularly, rivers serve as the most important freshwater resource and underlie the majority of water-demanding activities, resulting in highly polluted rivers. In central Iran, the Ghareh-Aghaj River supports many industrial, municipal, and agricultural land-uses along its path to the Persian Gulf. Although there may be reciprocal HM effects, no study has yet provided supporting scientific evidence on the river’s sediment HM content that might affect the sensitive biodiversity of the river and the Persian Gulf. This study measured the concentrations of five HMs at 11 susceptible and accessible locations along the river as follows: Arsenic (41.83 mg/kg) > Nickel (38.08 mg/kg) > Zinc (24.46 mg/kg) > Copper (18.86 mg/kg) > Lead (4.97 mg/kg). The HM distributions were uniform due to insignificant correlations and high coefficient of variations. According to the results, the river was not polluted with Cu, Zn, and Pb, partly with Ni, and highly with As. The concentration of As exceeded natural values in the river midstream zone and the seawardmost station where the river is exposed to intense agriculture and extensive use of arsenical pesticides and herbicides. This study highlighted the Ghareh-Aghaj River as worthy of further HM investigation, particularly As and urged implementation of HM elimination and monitoring measures to ensure their health and well-functioning.