Abstract:

The identification of groundwater pollution risk under ecological replenishment conditions is of great significance for groundwater safety replenishment. Although extensive research has been carried out on groundwater pollution risk at present, the evolution of groundwater pollution risk under ecological replenishment conditions is rarely involved. Therefore, this paper takes the Yongding River recharge area as the research object, starts with the dynamic changes of industrial pollution source pattern and groundwater level before and after the recharge(2002-2022), and constructs a groundwater pollution risk assessment system with coupled pollution load input-vadose zone restrain-aquifer transport, discusses the evolution law of groundwater pollution risk driven by pollution load and water level fluctuation, and provides support for the prevention and control of groundwater pollution risk. The results show that the overall number and load of industrial pollution sources show a downward trend from 2002 to 2022, and the main reason is the closure and relocation of smelting and processing industry represented by Shougang Industrial Park. By 2022, the high and medium risk load areas decrease to 0 and 14% respectively. In contrast, groundwater vulnerability showed a trend of decreasing first and then increasing. Before 2014, overmining in successive years led to a continuous decline in water level. Subsequently, reduced mining initiated at the end of 2014 and external water ecological restoration starting in 2019 led to a rapid rise in water level, and the dynamic change of water level directly affected groundwater vulnerability. The comprehensive risk of groundwater pollution in the study area showed an evolution law of decreasing first and then increasing, and 2014 was the turning point. Prior to 2014, the risk was mainly affected by the dual factors of surface pollution load and water level fluctuation. The change of industrial pattern led to the reduction of pollution load, and the decrease of water level led to the reduction of groundwater vulnerability, so the comprehensive risk continued to decline. With the commencement of reduced mining at the end of 2014 and the external water ecological restoration in 2019, the rapid rise of water level led to increased groundwater vulnerability. However, as the pattern of surface pollution load did not change significantly, the comprehensive risk increased, and water level fluctuation became the main factor at this stage.Enterprises with medium risk or above were mainly distributed in Hedong and Fengtai. The proportion of such enterprises classified as medium or high risk increased from 3% in 2014 to 15% in 2022.

Key words: groundwater pollution risk, pollution load, water level fluctuation, ecological water recharge, Yongding River