Groundwater Vulnerability Assessment to Cemeteries Pollution through GIS-Based DRASTIC Index

Abstract

Deposition of corpses in the ground is the most common burial practice, which can allow interactions between polluting compounds and the soil, groundwater, and surface water, which may afterwards lead to negative environmental impacts and risks to public health. The risk of cemeteries contaminating groundwater is related to their location, the quantity of clothes, metals and adornments buried, and geographical, geological, hydrogeological, and climatic factors. Using the DRASTIC index and geographical information system (GIS) tools, the potential for groundwater contamination was investigated in eight cemeteries located in the Figueira da Foz region (Portugal), which are the main anthropogenic pollution sources in the area. Aquifer vulnerability was assessed through the development of thirteen site characteristic maps, seven thematic maps, and a DRASTIC index vulnerability map, using GIS operation tools. No studies were found on the development of vulnerability maps with this method and digital tools. Cemeteries UC2, UC4, UC5, UC6, UC7, and UC8 are located within the zones susceptible to recharge, with an average recharge rate of 254 mm/year. Cemeteries UC5, UC7, and UC8 are expected to develop a greater water-holding capacity. The water table depth is more vulnerable at UC6, varying between 9.1 m and 15.2 m. However, results show only a high vulnerability associated with the UC4 cemetery with the contributions T,C > R,S > I > A > D, which should be under an environmental monitoring program. The area surrounding UC4 is characterized by a water table depth ranging between 15.2 m to 22.9 m, mainly fine-grained sands in both the vadose zone and the aquifer media, Gleyic Solonchaks at the topsoil, very unfavorable slope (0–2%), and high hydraulic conductivity (>81.5 m/day). The sensitivity analysis shows that the topography, soil media, and aquifer media weights were the most effective in the vulnerability assessment. However, the highest contributions to index variation were made by hydraulic conductivity, net recharge, and soil media. This type of approach not only makes it possible to assess the vulnerability of groundwater to contamination from cemeteries but also allows the definition of environmental monitoring plans as well as provides the entities responsible for its management and surveillance with a methodology and tools for its continuous monitoring.