Author(s)

Akaha C. Tse^1*, Lucky O. Odokuma²

¹Department of Geology, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Microbiology, University of Port Harcourt, Port Harcourt, Nigeria.

The vadose zone of a landfill site proposed as an integrated waste management facility was evaluated based on geohydrological, chemical and microbiological characteristics of the groundwater and underlying soil. These data were also used to assess the attenuation capacity of the zone by the use of microbial degradation test of some major constituents including fatty acids, organic nitrogen and chloride of the leachate for a 28-day period. The main soil type in vadose zone consisted of brownish clayey sand of low permeability. The depth to water table which is equal to the thickness of the vadose zone varied from 8 - 13 m. Groundwater flowed with a hydraulic gradient of approximately 4.0 × 10^-3 and a pore velocity of 1.6 × 10^-3 cm/sec. The results of the biodegradation tests showed that the major constituents of the leachate such as ammonia/organic nitrogen, phosphate and organic carbon were completely degraded within 28 days. The population of aerobic bacteria within the 6 m soil depth was sufficient to bring about over 0.05% organic carbon removal. The soil characteristics in the vadose zone are very favourable for the occurrence of natural attenuation. The potential natural attenuation capacity of the vadose zone is therefore classified as moderate to high.

Attenuation, Biodegradation, Biophysical, Landfill, Vadose Zone

Tse, A. and Odokuma, L. (2016) Biophysical Evaluation of the Vadose Zone at a Landfill Site in the Niger Delta, Nigeria. Journal of Geoscience and Environment Protection, 4, 33-42. doi: 10.4236/gep.2016.44006.