Abstract:

The Hailar Basin is located in an arid to semi-arid region, and its water resource has received widespread attention. Studying the hydrogeochemical characteristics of the local water environment and health risk assessment is conducive to better protection and utilization of water resource. Based on field sampling data, we analyzed its hydrochemical characteristics and influence factors, used the PHREEQC software to simulate the As-U occurrence, and conducted characteristic analysis and risk assessment of As-U co-pollution phenomena. The results show that the As-U concentrations in the local water environment mostly exceed the World Health Organization (WHO) standard limits. The As concentration in the water environment in the Beier Lake Depression-Cuogang Uplift is higher, and the U concentration in the Cuogang Uplift near Hulun Lake is higher. Calculated by the US EPA health risk assessment model, the average non-carcinogenic total risk HI_total of different populations all exceed the acceptable level (HI_total <1), and the average carcinogenic risk of As also exceeds the acceptable level (1×10^-6). The total non-carcinogenic risk and carcinogenic risk: children>female adult>male adult. The PHREEQC simulation results show that As in the water environment mainly exists in the form of As(V), and most of the sampling spots are dominated by {\mathrm{HAsO}}_4^{2-} and H₂ {\mathrm{AsO}}_4^{-}. Uranium occurs mainly in the form of U(VI): UO₂(CO₃) {}_3^{4-} and UO₂(CO₃) {}_2^{2-}. The chemical valence of As is readily affec-ted by the pH and Eh values. The pH decrease and the more toxic As(III) are likely formed under relatively reducing conditions. The chemical valence of U is not strongly affected by the pH and Eh values, but changing which would also form solid deposits such as bituminous uranium ore, which may cause stones and other related diseases.

Key words: arsenic, uranium, distribution characteristics, occurrence mode, health risk, Hailar basin