Water quality analysis and health risk assessment of the Lanzhou section of the Yellow River

The Yellow River flows through Lanzhou city and is the only drinking water source for 3.6 million people. However, people are not clear about the water environmental quality and safety in Lanzhou. To address this problem. Water samples were collected from different sites within this section during the high water period, normal water period and dry water period, and the environmental quality and health risk of the surface water were evaluated using the Nemerow index and health risk assessment method. The results are as follows: first, none of the pollutants exceeded the standard, except for total nitrogen; second, the highest comprehensive evaluation score was 1.04, so the water quality level was good; third, the health risk assessment showed that health risk value of water quality in the Lanzhou section of the Yellow River is on the high side, which is mainly caused by Chromium(Cr); fourth, the carcinogenic risk is five orders of magnitude higher than the non-carcinogenic risk, and the total carcinogenic risk is higher than the maximum acceptable risk level (10−5 a−1), while the total non-carcinogenic risk is lower than the acceptable health risk level (10−6 a−1). Therefore, to ensure the safety of its drinking water, Cr pollutants in the Lanzhou section of the Yellow River should be properly treated and controlled.