Use of the geophysical approaches for studying the environmental impact assessment of the human burying techniques to the soil and groundwater: A case study of Geheina cemeteries, Sohag, Egypt

Abstract

Electrical resistivity and self-potential are effective geophysical tools for monitoring the soil and groundwater pollution because they are accurate, rapid, costless and non-distractive techniques. Direct or indirect burying of the corpses into the soil is one of the main factors which pollute the soil and the groundwater after decomposition of the tissues and bones. Therefore, the main objective of this study are using these tools to evaluate the rate of soil and groundwater pollution due to burying the corpses in chipboard coffins at depths approximately 0.70–1.30 m (Christians burial method) and directly into the soil at depths about 1.5–1.8 m (Muslims burial method). Beside, assessing the contamination depths and flow paths of the groundwater investigated area. The study area was carefully chosen because of: 1- it contains two different burial methods, 2- presence of shallow groundwater aquifer, 3- the surface layer which contains the burial depth is porous and permeable, 4- the cemeteries are near enough to the population density and agricultural lands. The study area was divided to three main sites; site 1, site 2 and site 3 for Christian cemeteries, Muslims ones and control area that does not contains any cemeteries respectively. Five two-dimensional electrical resistivity tomography (ERT) profiles were surveyed and analyzed using RES2DINV software (two profiles on the site 1, two profiles on the site 2 and one profile on the site 3). 121 points of vertical electrical sounding (VES) at the same depth were collected and analyzed in 3D iso-resistivity map. Self-potential survey (SP) were performed on the same 121 points of VES stations for comparison where the data was contoured to build 3D iso-potential map. The geophysical results were correlated with the available borehole data. The results revealed presence of three resistivity zones of high resistivities (1000–3000 Ω m), moderate ones (50–1000 Ω m) and low ones (<50 Ω m). The main constituents of these three zones are clastic sedimentary rocks with different grain sizes. The rapid decreasing in the resistivity values in the site 2 than that in the site 1 is resulting from the rapid decomposition of the death bodies due to direct burying in the ground without coffins leading to more pollution rates of the soil and the groundwater than burying in coffins. Increasing of the burial depth causes increasing of the contamination rate of the shallow groundwater aquifer. Positive and negative values of potentials were recorded in 3D iso-potential contour map reflecting the flow direction from low to high potentials. The negative values were attributed to the leakage of more the putrefactive liquid resulting from decomposition of the death body. Positive potential values were caused due to the semi-fluid masses consisting of water and putrefied tissues which are mostly generated by the corpses buried in coffins with less amount of fluids and the putrefactive liquid evaporation and low humidity.