OICC Press Anthropogenic Pollution 2588-4646 10 1 2026 06 30 Assessment of Pollution Indices and Ecological Risks of Potentially Toxic Elements in Sediments of an Ephemeral River: A Case Study of the Gharakahriz River, Central Iran 10.57647/AP.2026.1001.05 EN Maryam Sadeghi Department of Natural Resources and Environment, Ar.C., Islamic Azad University, Arak, Iran Javad Varvani Department of Natural Resources and Environment, Ar.C., Islamic Azad University, Arak, Iran; Research Centre of Applied Plant Science, Ar.C. Islamic Azad University, Arak, Iran https://orcid.org/0000-0003-2033-4713 Hamid Toranjzar Department of Natural Resources and Environment, Ar.C., Islamic Azad University, Arak, Iran Abbas Ahmadi Department of Natural Resources and Environment, Ar.C., Islamic Azad University, Arak, Iran; Food Security Research Centre, Ar.C., Islamic Azad University, Arak, Iran Amir Hossein Baghaie Department of Natural Resources and Environment, Ar.C., Islamic Azad University, Arak, Iran Journal Article 2026 06 30 Ephemeral rivers in semi-arid regions are highly vulnerable to anthropogenic contamination due to intermittent flow regimes and proximity to industrial and agricultural activities. This study evaluates the extent of pollution and associated ecological risks posed by potentially toxic elements (PTEs) in sediments of the Gharakahriz River, an ephemeral watercourse in Central Iran that traverses urban, industrial, and agricultural zones. Fifteen surface sediment samples in three land use zones (total 45 samples)were collected along a longitudinal gradient (upstream to downstream) and analyzed for Cd, Pb, Cu, Zn, Ni, and Cr using expert laboratory analysis. Sequential extraction (Tessier method) indicated that Cd and Pb exhibited the highest mobility, with 25–30% of their total concentrations residing in exchangeable and carbonate-bound fractions—phases readily released under minor environmental changes. Pollution assessment using geoaccumulation index (Igeo), enrichment factor (EF), and potential ecological risk index (PERI) revealed severe anthropogenic enrichment, particularly in midstream sites influenced by industrial discharge, where Cd concentrations exceeded local background values by up to 13-fold. Multivariate statistical analyses (PCA and cluster analysis) confirmed that industrial effluents and agrochemical runoff are the primary sources of contamination. Notably, over 85% of total PTE content was associated with non-residual (labile) fractions, indicating high bioavailability and significant ecological risk to soil, water, and biota—especially in a region where floodwaters redistribute contaminated sediments onto croplands. These findings highlight the urgent need for regulated discharge controls and sediment quality criteria in ephemeral river systems of arid and semi-arid regions.