Simulation study on the migration of F^- in soil around Chagan Lake, China

Chagan Lake is located in the high-fluorine area of western Jilin, with high fluoride content in surface water, soil, and groundwater around it. Due to its unique topography and hydrogeological conditions, Chagan Lake collects surrounding water and is closely connected with groundwater. The complex surrounding water not only affects the groundwater quality through Chagan Lake, but also affects groundwater through the infiltration of vadose zone. In order to further study the characteristics of the migration of F^- in the soil around Chagan Lake along with water flow in the vadose zone and its impact on groundwater, soil column experiments were carried out using soil collected in the field, combined with HYDRUS-1D to simulate the migration characteristics of F^-. The model was verified by measured data, the sensitivity of each parameter was analyzed by the single-factor disturbance method, and the effect of F^- on groundwater was simulated and predicted. The results showed that (1) the soil column experiment was carried out using transport solutions of different pH value. The time required for F^- to penetrate the soil column under alkaline conditions was shorter, and the HYDRUS model used has a high degree of fitting. (2) The single-factor disturbance method is used to analyze the sensitivity of the parameters. The parameters that have a greater impact on the migration of fluoride ions in the soil are saturated hydraulic conductivity, adsorption coefficient, and soil bulk density. (3) In the prediction scenario, due to the adsorption and interception of the vadose zone, as the depth increases, the time it takes for F^- to accumulate is also longer. The groundwater around Chagan Lake is relatively shallow, and surface F^- in alkaline environment reaches the underground aquifer within 2 days. The F^- concentration in the groundwater reaches its maximum before the end of the irrigation period. In neutral environment, the F^- concentration in groundwater did not reach the maximum before the end of the irrigation period.