METAL POLLUTION AND MICROBIAL QUALITY ASSESSMENT OF SCRAPYARD SOIL IN PARTS OF BENIN CITY, NIGERIA.

Abstract

The proliferation of scrapyards is an environmental threat and constitutes a possible health hazard to nearby residents. This study is aimed at assessing some physicochemical properties, metal pollution, and microbial quality of scrapyard soil in Oluku, University of Benin Botanical Garden (reference) and Upper Iwehen Street, Benin City. Soil samples were gathered from three points between January to March 2024 to a depth range of 0-15cm using hand dug auger. Physicochemical and microbial analyses were conducted using established analytical techniques. The results indicated that all physicochemical parameters at the points fall within the acceptable limits except for conductivity (1107 μs/cm) in scrapyard point 3, which slightly exceeds the stipulated guideline. Metal analysis revealed that Cr, Fe, and Pb levels were within permissible limits, with Zn (300.1) exceeding limits at scrapyard point 1, and Cd (3.1) and Cu (106.8) surpassing permissible limits in scrapyard points. Also, four metals discriminated between the reference point and the scrapyard points (P<0.05). The contamination degree result reveals that the scrapyard points 1 and 3 (9.64 and 8.48) are moderately contaminated while the reference point (2.84) is slightly contaminated. The pollution load index indicated that the scrapyard points 1 and 3 (1.10 and 1.08) are polluted, while the reference point (0.94) is unpolluted. The geo-accumulation index (I_geo) results for Cd, Cu, and Zn distinguish between the scrapyards and reference points while Cr, Fe, and Pb did not. Cadmium in scrapyard points 1 and 3 (2.90 and 2.61) indicated moderately to heavily contaminated, contrasting with the slightly polluted in the reference point (0.90). Total bacteria count ranged from (3×10³- 6×10³) cfu/g in scrapyard points and (0×10³-1×10³) cfu/g at the reference point. The results reveal that scrapyard points 1 and 3 are contaminated when compared with the reference point.