Hydrochemical evaluation and risk assessment of the Danube river, Hungary using Canadian indices, geochemical modeling, and simulation techniques

Abstract This study investigates the metals risks in the Danube River, Hungary, and identifies the natural and anthropogenic sources using geochemical modeling. In total, 76 water samples were collected from seven sites along the river during 2018. Physicochemical and heavy metals have been analyzed. Statistical tools, including Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), were applied. Water quality was assessed using the Canadian Water Quality Index (CWQI), Metal Pollution Index (MPI), Nemerow Composite Index (NCI), Hazard Quotient (HQ), Hazard Index (HI), and Carcinogenic Risk (CR). A probabilistic approach using Monte Carlo simulation was applied to evaluate uncertainty and health risks. Geochemical modeling revealed that the river is undersaturated with minerals like gypsum, anhydrite, and halite, but supersaturated with aragonite, dolomite, and calcite. The average CWQI (44.8) and Weighted Arithmetic Water Quality Index (WAWQI, 60.1) indicate that the water is unsuitable for drinking. However, Sodium Adsorption Ratio (SAR = 0.5), Sodium Percentage (Na% = 15.4), and Kelly’s Ratio (KR = 0.2), suggest favorable conditions for agricultural use. The low ecological risk index (RI = 0.5) and MPI (< 0.3) indicate minimal contamination, while the NCI (1.2) flags the right bank of Dunaföldvár as nearing a critical pollution threshold. Although non-carcinogenic health risks (HQ, HI < 1) for chromium, copper, lead, and nitrate were minimal, Monte Carlo simulation showed elevated carcinogenic risk for lead and chromium in children at the 95th percentile. These findings highlight the need for ongoing monitoring and treatment of water and offer valuable insights for sustainable water management and policy planning in Hungary.