The impact of mining on the ecosystem of central Iran's Wetland: A probabilistic approach to assessing ecological risk

Abstract

Wetlands are essential for sustaining ecological stability and ecosystem equilibrium. This study investigated soil pollution and ecological risks in Iran's Meighan wetland, focusing on the impact of nearby sodium sulfate mining. The enrichment factor, geo-accumulation index, and potential ecological risk index of elements were evaluated using both deterministic and probabilistic approaches. The findings revealed some potentially toxic elements levels in ore waste exceeded those in raw materials, and the wetland acted as a receptor for toxic elements. Additionally, rare earth elements such as yttrium, ytterbium, cerium, scandium, and lanthanum were detected in wetland samples. Analysis revealed that cobalt (in some waste ore samples), selenium (downstream), and vanadium (in some wetland samples) exceeded permissible limits. Deterministic risk assessments showed extremely high pollution indices for vanadium (enrichment factor = 85.77, Geo-accumulation Index, Igeo= 11.37) and titanium (EF= 5.39), indicating significant anthropogenic impacts. Monte Carlo simulations suggested that the Igeo values revealed a significant rise in contamination levels, with arsenic (52.83 %) and barium (31.59 %) indicating moderately to heavy polluted. Meanwhile, vanadium (97.21 %), aluminum (96.91 %), lead (84.69 %), chromium (25.33 %), nickel (25.17 %), cobalt (23.32 %), and manganese (13.36 %) were classified as extremely polluted. The aluminum, lead, and titanium exhibited very high enrichment, with levels at 0.3 %, 0.4 %, and 0.2 %, respectively. The potential ecological risk index classified 63.53 % of samples as 'Very High' risk, with nickel and chromium being the most significant contributors. Hence, this mine posed a substantial ecological risk to Meighan Wetland, requiring rehabilitation efforts to address anthropogenic and geogenic factors.