Geophysical assessment and determination of methane concentration of an active waste dumpsite at Yenagoa. bayelsa state, Nigeria. – A. A. Aderogba
Vertical electrical sounding (VES) and Wenner profiling were carried out at a dumpsite and its adjoining areas notably Tombia, Gbarantoru and Akaibiri to assess the groundwater status and to determine the methane concentration variations with depth in the area. This dumpsite consists of inorganic and organic materials. The contribution of this dumpsite to waste disposal in Yenagoa has increased over the years and is roughly one-third at present of total waste. Surface investigation of the area was done and data was acquired using geophysical equipment ABEM SAS 1000 Terrameter set. The resistivity results of the vertical electrical sounding at the dumpsite were relatively low, which signifies that groundwater in the dumpsite area is contaminated down to a depth of about 16.1m. The resistivity results of the Wenner profiling at the dumpsite also reveals that the leachate plume contaminates groundwater up to a depth of about 18.5m. However, the resistivity results of the surrounding villages (Tombia, Gbarantoru, and Akaibiri) are relatively high, which suggest that these areas are saturated with fresh groundwater aquifers. The study of the textural parameters in the dumpsite sediments also reveals that the sediments varies from fine to very fine sand and sorting also reveals that the sediments are moderately well sorted. Hence have low percentage of porosity and permeability. Based on estimations and findings of this present work, it was concluded that the maximum methane emission from this landfill site is around 0.08 % of the global landfill methane emission. Therefore, it is reasonable to assume that since about onefourth of the landfill methane emissions in Yenagoa occur here. As the economic and social status of the people increases it is expected to see an increase in the total MSW. Thus, in future the methane emission from MSW will increase.