Assessment of some enzymes in top soils from metallic material dumpsites in Benin City, Nigeria

Abstract

Open scrap metallic material dumpsites or makeshift scrapyards are used in the management of collected disused metallic materials in Benin city, Edo State, Nigeria. Six topsoil samples were collected in duplicates from six open disused metallic material dumpsites located in six areas within Benin city which included; Aduwawa, Saint Saviour, Water Board, second Ibiwe, first Ibiwe and Uwelu respectively. The control soil samples were collected from the vicinity of the Faculty of Life Sciences, University of Benin. The pH and electrical conductivity (EC) of the soil samples were determined using calibrated meters. Enzyme profiling of the soil samples was conducted using standard analytical procedures which included titrimetry and colourimetric techniques. One-way analysis of variance (ANOVA) of the respective mean enzyme activities of the soil samples was conducted (α=0.05). The mean pH and EC values of the topsoil samples obtained from the dumpsites varied from 6.3 ± 0.2 to 7.8 ± 0.2 and 22.2 ± 0.5 to 107.7 ± 2.2 μ mhos/cm respectively. The mean dehydrogenase readings for topsoil from the dumpsite varied from 4.5 ± 0.4 to 8.9± 0.2 μg TPF/g soil respectively, while the control soil had a dehydrogenase activity mean reading of 1.7 ± 0.2 μg TPF/g soil The observed differences between the mean enzyme activities were significant (F = 167.062, p<0.05). It is likely that there was a link between anthropogenic land usage pattern and the edaphic enzyme profiles of the examined soil samples. It is recommended that further studies focusing on the specific nature of the soil enzymes and the microbial diversity of these contaminated topsoil niches should be conducted.