Ecological Risk Assessment of Heavy Metals in Soil in Uliastai soum, Zavkhan Province, Western Mongolia

Завхан аймгийн Улиастай сумын хөрсний хүнд металлаас экологид үзүүлэх эрсдэлийн үнэлгээ

Abstract

This study investigated the presence of heavy metals in the soils of Uliastai soum, Zavkhan province, and compared the findings with previous soil sample analyses from 2022. A total of 20 soil samples were collected and analyzed for 33 elements at an SGS-accredited laboratory. Particular attention was given to nine heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, V, Zn) known for their harmful effects on environmental and human health. The concentrations of these metals were compared against Mongolian national standards (MNS 5850:2019) and international benchmarks. Although all measured concentrations were below the permissible limits, geo-accumulation index (Igeo) and ecological risk index (Er) assessments revealed that certain elements fell within the “moderately to highly polluted” and “highly polluted” categories. Notably, elevated ecological risks were identified for arsenic (As) and lead (Pb) at specific sampling sites. Enrichment factor (EF) analysis indicated “moderate” to “more than moderate” enrichment for elements such as Cu, Zn, and Ni, suggesting anthropogenic sources of contamination. High contamination levels near a car repair shop, a boiler house, and a meat processing plant further point to insufficient environmental regulation in those areas. The lowest ecological risk value, 5.54, was observed in a sample near the car repair shop. Overall, while the current threat from heavy metals in Uliastai’s soils appears low, localized accumulation poses potential long-term risks to environmental stability.