A Comprehensive Study of Heavy Metals in Centralized Drinking Water Sources of the Yangtze River Basin: Levels, Sources, and Probabilistic Health Risk

The water quality of centralized drinking water sources (CDWSs) in the Yangtze River Basin (YRB) has received widespread public attention. Regrettably, due to the lack of large-scale and high-frequency monitoring data, the trends, sources, and risks of heavy metals (HMs) in the water of CDWSs in the YRB are still unclear. In addition, the correlation between HMs and water quality parameters in natural water has not been established, which greatly affects the efficiency of water management. Herein, we collected data for eight HMs and twelve water quality physical–chemical parameters from 114 CDWSs in 71 prefecture-level cities in the YRB region. An unprecedented spatial distribution map of HMs in the YRB region was drawn, and the response of HMs to water quality and nutrient levels was studied. Overall, the level of HM pollution was low, but the threat of chloride, nitrogen, and phosphorus still exists. The detection rates of the eight HMs ranged from 60.00% (Ti) to 99.82% (Fe), and the mean concentrations were ranked as follows: Fe (36.576 ± 36.784 μg/L) > Mn (7.362 ± 7.347 μg/L) > Ti (3.832 ± 6.344 μg/L) > Co (2.283 ± 3.423 μg/L) > Se (0.247 ± 0.116 μg/L) > Cd (0.089 ± 0.286 μg/L) > Be (0.054 ± 0.067 μg/L) > Tl (0.015 ± 0.012 μg/L). In the large geographic area, the total concentrations of the eight HMs exhibited a fluctuating decay trend over time from 2018 to 2022. Geographically, industrial and agricultural production and geological coupling factors led to significant spatial heterogeneity in HM concentrations in the following order: midstream > downstream > upstream. Importantly, this study proved that Cl−, SO42−, nitrogen, and phosphorus may drive the absorption and transfer of HMs in natural water. Fortunately, exposure to the eight HMs does not cause adverse health effects in humans.