イラン、Qorveh-Dehgolan平野におけるヒ素汚染の深刻度、水理化学的プロセス、発生源特定、健康リスクの統合評価

Contaminated groundwater is a major pathway of human exposure to geogenic pollutants. This study investigates the occurrence and spatial distribution of arsenic and other trace elements in groundwater of the Qorveh-Dehgolan plain. Despite the high arsenic levels previously reported in this region, the hydrogeochemical processes controlling its enrichment remain poorly understood. To address this gap, groundwater hydrochemistry and quality were evaluated using an integrated approach that combines multivariate statistical analysis with Self-Organizing Maps (SOM), supported by Piper and Gibbs diagrams and cation-exchange indices. SOM analysis produced thirty neurons that grouped into three clusters, revealing distinct hydrochemical patterns across the study area. The dominant hydrochemical facies are Ca-Mg-HCO₃ (Cluster I), Ca-SO₄ (Cluster II), and mixed types (Clusters I and III), and groundwater chemistry is mainly governed by silicate and carbonate dissolution. Arsenic concentrations vary widely from 0.01 to 183.64 µg/L, with approximately 71% of the samples surpassing the WHO recommended limit of 10 µg/L for drinking water. Carcinogenic Risk (CR) calculations show that more than 70% of sampling locations exceed acceptable limits, with arsenic being the primary driver of both carcinogenic and non-carcinogenic health risks. The results suggest that arsenic is predominantly of geogenic origin, mainly linked to geothermal activity and the alteration of young acidic rocks, while localized mining activities likely enhance arsenic levels in the northern sector of the plain.