Determination of leachate leakage around a valley type landfill and its pollution and risk on groundwater.

This paper investigates leachate leakage of a typical valley-type landfill in South China and health risk of groundwater pollution. Through geophysical detection on landfill, chemical analysis of 19 parameters such as pH, total dissolved solids (TDS), total hardness (TH), potassium permanganate index (COD), ammonia nitrogen (NH-N), sulfate (SO), chloride (Cl), fluoride (F), nitrate (NO-N), nitrite (NO-N), and heavy metals (Hg, Fe, Mn, Cu, Zn, Cr, Pb and Cd) in groundwater, and model simulation, the prediction of pollution resource and risk level is achieved. This aggregated approach aims to effectively manage and control groundwater contamination and public health risks from the source. The results of transient electromagnetic method showed that four leakage areas of impermeable layer were existed in the landfill, with an area of 336.8 m and a depth of 15-22 m. The chemical analysis and pollution assessment revealed that groundwater at ZK01 and ZK04 were heavily polluted, ZK02 and ZK03 were slightly polluted, and ZK05 was non-polluted. Water quality of points ZK01-04 exceeded the standard value of Class III water in the Groundwater Quality Standard (GB/T 14,848-2017), and the main excessive parameters are pH, NH-N, Mn and Fe. The landfill leakage, rock weathering dissolution and water-rock interaction possibly were the main sources of groundwater pollution through correlation analysis (CA) and principle component analysis (PCA). Numerical simulation based on the RBCA (Risk-based Corrective Action) model thought Mn and NO-N had adverse non-carcinogenic effects o human health risk. Assuming that no pollution control measures are taken, the average increase rate of hazard index (HI) for pollutants within the past 20 years was between 0.04 and 0.08/a, and the average expansion rates of the risk area were 341-432 m/a. The expansion rates of risk area along the groundwater runoff were 1.6-3.8 m/a, drinking water safety downstream of main pollution source runoff is the focus of protection.