Abstract:Based on analysis of physical and chemical properties of water samples from 16 sampling points in the middle and lower reaches and Doilungqu tributary of Lhasa River Basin, content and distribution of main heavy metals in Lhasa River Basin were analyzed, and preliminary pollution risk assessment was evaluated by comprehensive pollution index method. The results show that content of As, Cd, Fe, Cu, Zn and Mn in Lhasa River Basin does not exceed the standard of class I water quality in environmental quality standard for surface water (GB3838—2002). There is no significant correlation between content of these six heavy metals and pH value, among which pollution of Cd, Cu and Mn has certain homology while pollution of As, Mn, Fe, Cu is multi-source. Comprehensive indexes of heavy metals pollution in middle and lower reaches, Doilungqu tributary and whole basin of Lhasa River Basin are 0.048, 0.192, 0.072 and 0.117, respectively. The pollution degree classification of all these reaches is non-pollution. Due to more intensive human activities, heavy metal pollution index in the lower reach of Lhasa River Basin is significantly higher than that in the middle reach and Doilungqu tributary.