Assessment Of Vadose Zone Characteristics For Environmental Impact Audit Of Selected Cemeteries Around Osun State, South-Western Part Of Nigeria

Cemeteries have been identified as a possible source of groundwater and environmental pollution. This may be due to wrong siting of cemeteries, poor soil selection and very thin vadose zone. Over the years, most communities around Osun State experience a number of communicable diseases like dysentery, diarrhea and typhoid, especially after episodes of flash floods. Therefore, this study was carried out to audit the impact of burial practices on the immediate environment viz-a-viz their interaction with both surface and groundwater which forms the main source of potable water for the communities. Method of approach include; assessing possible water contamination, studying the vadose hydrological characteristics as well as studying the geotechnical properties of soils within the vadose zone. Water samples from the vicinity of both cemeteries shows probable contamination with an average pH of 6.19 for Ede and 6.57 for Iragbiji, EC with an average 480μS for Ede and 1210μS for Iragbiji. Biological constituents found within the area include; enterobacteriaceae (salmonella spp., serratia spp., proteus spp., shigella spp.), suggesting likely contamination of both surface and groundwater around the vicinity of the cemeteries. Most cations and anions analysed for (Mg2+, NO3-, SO42-, and PO43-) comply with the WHO standards based on their maximum permissible limits (MPL). Geotechnical investigations revealed that soils within the study areas are largely unsuitable for a standard cemetery due to their high moisture content, poor grading characteristics, low compaction value, poor hydraulic characteristics and shallow water level. The study concluded that cemeteries from both towns have a negative impact on their immediate environment due to poor selection of soil materials (porous and permeable sandy soil) as reflected in the quality of surface and groundwater.