ASSESSMENT OF PHYSICOCHEMICAL PROPERTIES, HEAVY METALS COMPOSITION AND MICROBIAL LOAD OF SOIL AT OLOMORE DUMP SITE, ABEOKUTA, OGUN STATE

ABSTRACT Dumpsites are significant sources of environmental pollution, often leading to soil contamination with heavy metals, microbial pathogens, and altered physicochemical properties, posing risks to human health and ecosystem stability. This study aimed to evaluate the physicochemical properties, microbial loads, and heavy metal concentrations of soil from the Olomoore dumpsite to determine the extent of contamination and potential environmental risks. Soil samples were collected from five designated points within the dumpsite and analyzed for pH, electrical conductivity, organic matter, cation exchange capacity, microbial counts, and heavy metal concentrations using standard laboratory procedures. The obtained data were compared with standards to assess contamination levels. The soil pH ranged from 6.8 (Point E) to 8.6 (Point A), with electrical conductivity varying between 190 µS/cm (Point E) and 420 µS/cm (Point A), exceeding the WHO/LASEPA limit of 200 µS/cm at most points. Organic matter content decreased from 4.5% (Point D) to 2.2% (Point A), indicating a decline in soil fertility. Microbial analysis revealed high bacterial counts ranging from 2.2 × 10⁶ CFU/g (Point E) to 6.8 × 10⁶ CFU/g (Point A) and fungal counts from 7.5 × 10⁴ CFU/g (Point E) to 3.0 × 10⁵ CFU/g (Point A), suggesting significant microbial activity. Heavy metal analysis showed elevated levels of lead (130 mg/L at Point A), cadmium (4.5 mg/g at Point A), and arsenic (18 mg/L at Point A), with most values surpassing WHO permissible limits (50 mg/L for lead, 1 mg/g for cadmium, and 10 mg/L for arsenic). This study confirmed that the Olomoore dumpsite soil is highly contaminated with heavy metals and microbial pathogens, posing environmental and health hazards.