Abstract: To identify the potential ecological risks of heavy metals in groundwater in inner river basin, we collected 67 groundwater samples from the Yanqi Basin and analyzed the concentrations of six heavy metals. The potential ecological risks of heavy metals were quantitatively assessed using the potential ecological risk index (RI) and the ecological risk warning index (IER). Results showed that the average concentrations of Cd and Ni in groundwater were equal to 1.4 times and 1.15 times of the Class III thresholds of the “Standard for Groundwater Quality (GB/T 14848-2017)”, respectively. The average values of the single potential ecological risk index (E_i) of heavy metals in groundwater were ranked Cd>Ni>Mn>Cr>Cu>Zn, being at a slight ecological risk. The average RI value of heavy metals in groundwater was 23.89, indicating a slight ecological risk level. The average value of the single ecological risk warning index (IER_i) of heavy metals in groundwater was ranked Cd=Mn>Ni>Cr>Zn>Cu, indicating a no warning level for all the analyzed heavy metals. The average IER value of heavy metals in groundwater was -3.87, indicating a no warning level. The E_i and IER_i index of each heavy metal in groundwater in the Yanqi Basin showed different spatial distribution patterns. Overall, Cd is the potential heavy metal with the highest ecological risk in the groundwater in the Yanqi Basin, which deserves attention.

Key words: groundwater, heavy metal, ecological risk, early warning, Yanqi Basin