Simulation of groundwater contaminant transport from cemeteries: a case study in the Tra Vinh Province, Vietnam

ABSTRACT This study uses a groundwater modelling system (GMS) to simulate the change in groundwater levels and the transport of pollutants (NH4+) from a cemetery in Tra Vinh city, Vietnam. The model consisted of 13 hydrogeological layers, including seven aquifers and six impermeable layers, constructed from data collected at 250 boreholes and 59 pumping tests. The results show a significant decline in groundwater levels from 1994 to 2018. The qp3 and qp2-3 aquifers, especially n22, are heavily exploited, causing notable groundwater declines. The Holocene aquifer shows the most severe depletion, and the contaminant plume extends up to 1.2 km to the north and west. The NH4+ concentration at the observed point located 200 m from the cemetery reached 15.2 mg·L−1 after one year, decreasing to 10.5 mg·L−1 after five years. The upper Pleistocene aquifers (qp3 and qp2-3) have a maximum NH4+ concentration of 5.0 mg·L−1, while the deeper layers are less affected. The study recommends that a safe distance from groundwater wells to cemeteries of 200 m or more will ensure water quality safety. This study provides an initial understanding for managers regarding the pollutant dispersion process from cemeteries to surrounding water resources, and provides plans for sustainable water resource management.