Abstract: In the aim of investigating the pollution status of heavy metals in the middle and lower reaches of Hanjiang River, we collected water samples from 20 points in June 2019 (wet season) and January 2020 (dry season), respectively, and measured the concentrations of eight heavy metals (Cu, Zn, Pb, Fe, Mn, As, Se and Cd) in the waters. We further analyzed the spatio-temporal distribution characteristics of heavy metal pollution, and evaluated the pollution status of heavy metal. Our findings manifested that Fe and Mn were dominant heavy metals in the water body of the middle and lower reaches of Hanjiang River, while the concentrations of other six heavy metals met the surface water class-Ⅱ standard. The concentrations of Fe and Mn fluctuated greatly along the middle and lower reaches of the Hanjiang River, and their change rules were basically consistent. The maximum concentrations of Fe and Mn were detected at Zhupi River (a tributary), exceeding the limit of surface water environmental quality standard by 4.63 times and 0.13 times, respectively. In addition, the concentration of Fe in section S17 (Hanchuan City) exceeded the standard by 3.89 times. In association with historical data analysis, we found that heavy metal concentration of water body in the middle and lower reaches of Hanjiang River is on the rise in general in recent years. The evaluation results indicate that the water quality in the middle and lower reaches of Hanjiang River is generally good. Zhongxiang City and Hanchuan City are two cities with heavy metal pollution problems. The heavy metal pollution in the tributary Zhupi River should arouse more attention.

Key words: middle and lower reaches of Hanjiang River, heavy metals, spatio-temporal distribution, correlation analysis, pollution assessment