Abstract

ODUKOYA, AM; ORESANYA, O  and  ABIMBOLA, A.F. Biogeochemical and engineering characteristics of soils and groundwater around a dumpsite. Earth Sci. Res. J. [online]. 2013, vol.17, n.1, pp.53-60. ISSN 1794-6190.

An active dumpsite in Lagos south-western Nigeria was monitored to test natural attenuation efficiency in reducing contaminants by determining soil and groundwater biogeochemical and engineering properties within and around the site. From the Casagrande Plasticity Chart, the soil could be classified as clay or silt having intermediate to high plasticity; unsaturated zone thickness was 10-20m and permeability was low (1.96x10-5 to 41.8x10-5 m/s). Appropriate microorganisms, such as bacteria, viruses and fungi which are required for natural attenuation, were naturally present. Nutrients such as calcium, copper, magnesium, manganese, potassium, sodium and zinc, as well as electron donor (organic carbon) and electron acceptor (oxygen, nitrate, sulphate and iron), were also present in various amounts for effective natural attenuation. All the parameters analysed in water samples came within Environmental Protection Agency standards, except Fe, Na, Cl, NO3, Al, Ba, Ni, total bacteria and total fungi. Phenol and total viral count were not detected in the two boreholes studied, but they showed values as high as 10,000 MPN/100ml and 230 CFU/100ml, respectively, in leachate. The concentration of contaminants in the soil was very high and inversely proportional to depth.

Keywords : leachate; natural attenuation; nutrient; contaminant; electron donor.

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