The Application of Geophysical Techniques in Tracking Leachate Plumes Migration in a Typical Cemetery within the Sandy formation in Benin City, Nigeria

摘要

The survey aim is to track leachate plumes within the sandy formation which is below the surface laterite layer.It investigates the presence and migration of leachate plumes in the sandy region in a typical cemetery(Third Cemetery),in Benin City,Nigeria.The research engaged Vertical Electrical Sounding(VES),2-Dimensional computation of migration in both the vertical and horizontal directions.The electrical resistivity data collected in parallel equidistant lines was processed to obtain geoelectric models using Res2dinv.The leachate plumes in the cemetery migrate vertically and horizontally at different rates.The maximum and minimum rates of vertical migration are 4.1 and 0.2 cm/day respectively,while the maximum and minimum rates of horizontal migration are 32.8 and 1.7 cm/day respectively.Volumetric analysis of the plume zones indicates that of the 75,231m3 of the subsurface imaged,6,322 m3 is the zone contaminated by leachate plume,that is,8.4%of the earth volume investigated contained leachate plume.The research also showed that repeated ERT surveys can track movement of leachate plume emanating from decomposed dead bodies over time in active cemetery.The average travel time for a leachate plume to transverse a vertical distance of 6.6 m in coarse sand is 366.7 days at constant migration speed of 1.8 cm/day.