Inter-basin water transfer enhances the human health risk of heavy metals in the middle and lower Han River, China

The ecological and human health issues caused by inter-basin water transfer have drawn wide attention. To illustrate the spatial and temporal distribution of heavy metals (HMs) in the middle and lower Han River (MLHR), a 1D hydro-environmental model was developed, calibrated, and validated based on the observed data. Three simulation scenarios were conducted to analyze the human health risks resulting from heavy metal pollution. The results show that the water flow reduction after water transfer enhanced the heavy metal pollution in the MLHR. The total health risk of HMs in surface water of the MLHR basin was 4.69 x 10-5 a-1 for adults and 7.82 x 10-5 a-1 for children without the water transfer, while it increased to 4.77 x 10-5 a-1 and 7.95 x 10-5 a-1 when the South-to-North Water Transfer Project (SNWTP) was put into operation. The Yangtze to Han River Water Transfer project (YHWTP) can partially offset the adverse SNWTP influences. However, the human health risk is still higher than those without SNWTP operation. The health risks in the MLHR basin are main from carcinogens As, which should be prioritized as the main targets for water environment risk management in the Han River basin.