Physicochemical Properties of Soil Exposed to Saw Dust and Timber Processing Activities in Port Harcourt, Rivers State, Nigeria

Studies have highlighted the modification of the microbiology of soils exposed to timber processing waste, but there is limited data on the geochemistry. This study assessed the soils at Marine Base, Mile 3, and the Iloabuchi timber markets in Port Harcourt, River State, Nigeria exposed to saw dust and timber processing activities, to evaluate for their physicochemical characteristics, polyaromatic hydrocarbon (PAH) levels and heavy metals concentrations. The soil samples were randomly taken from different depths (0-10, 1530, and 30-50 cm) at four cardinal points from the sampling locations. The pH values recorded in the control site were found to range from 3.43-4.7. The sampling sites, exhibited a wider range of pH values. Marine base had a pH range of 3.69-5.50, Mile 3 had a range of 4.49-6.22, and Iloabuchi had the highest pH range of 6.62-7.82. The conductivity values varied between the control site and the sampling sites. The control site had conductivity values ranging from 63-93 µS/cm. The highest conductivity value was observed in the Iloabuchi site, with the range 1621-1767 µS/Cm. The control recorded the highest bulk density of 2.56 g/cm³ and porosity (81.00 g/cm³) compared with the study samples. The highest values of phosphate, sulphate and nitrate in soil were obtained at Iloabuchi site (12.59 mg/kg, 488.4 mg/kg and 18.47 mg/kg respectively) in the sub and topsoil, these values are significantly (P< 0.05) higher than the corresponding values in control (0.05 mg/kg, 10.03 mg/kg and 6.4 mg/kg). The order of concentrations of the heavy metals was typically: Co > Mn > As > Ni > Cd > Zn. The order is attributed to several factors such as variations in the geological composition of the soil and industrial activities in the vicinity. The values indicate pollution in these areas. The study also revealed that 16 polyaromatic hydrocarbons (PAHs) were present in measurable, variable, and detectable quantities in the soil samples from the three sawmilling sites. The metal concentrations found in the study may not be a significant risk to human health, though there is a possibility of accumulation over time leading to potential environmental issues in the future. Therefore, continuous evaluation and monitoring of sawmill activities and their surroundings are recommended to prevent harmful effects from excessive pollutants.