Monitoring and risk assessment of arsenic species and metals in the Taehwa River in Ulsan, the largest industrial city in South Korea

Toxic metals, As, and As species were monitored at 18 stations along the Taehwa River in Ulsan. The concentrations of Ni (98.4 μg/L) at stations near industrial areas were relatively high and exceeded the WHO's drinking water guidelines (70 μg/L) and the US EPA's national recommended water quality criteria (52 μg/L). Principal component analysis and cluster analysis revealed that Ni and Cu were more strongly influenced by industrial activity than other elements in the Taehwa River estuary. Analysis of the hazard quotient (HQ) and cancer risk (CR) indicated that As was of the greatest non-carcinogenic and carcinogenic concern. Notably, the HQ and CR of AsIII at suburban stations exceeded 1 and 10−4, respectively, representing a significant health risk. These results indicate that As speciation testing is crucial for the development of effective management plans based on health risks because the toxicity and mobility of As depend on its chemical form. •The levels of Ni at industrial stations exceeded water quality guidelines.•Ni and Cu were strongly influenced by industrial activity in the river estuary.•AsIII was detected in stagnant water due to the algal and phytoplankton blooms.•The HQ and CR of AsIII at suburban stations exceeded 1 and 1 × 10−4, respectively.