Particle Size Effect of Locally Pyrolyzed Biochar on the Remediation of Some Heavy Metals in Crude Oil Contaminated Soils

Tate Joseph O., Teknikio Jemimah B., Abhunu Owilliba E.

Abstract: Two particle sized biochar from locally pyrolyzed Rhizophora racemose in earthen kiln were assessed on the fate of aluminum (Al), lead (Pb), and zinc (Zn), and the effect on soil organic matter (SOM), organic carbon (SOC) and total nitrogen (TN). Soil samples contaminated with known concentration of crude oil were amended with < 2 mm (B1) and 2-4 mm (B2) biochars incorporated at five different rates (1, 2, 3, 4 and 6 Mg ha-1) in the Teaching and Research Farm, Faculty of Agriculture, Niger Delta University, Bayelsa State. Results obtained shows that exchangeable Pb concentration significantly increased from 0.84-6.09 mg kg-1; with Al from 0.03-0.32 mgkg-1 at increasing rate of crude oil and B1 biochar amendment. Conversely, B2 biochar significantly decreased exchangeable Zn concentration from 12.24-3.57 mg kg-1. Using the wet oxidation and van Bemmelen’s approach, the incorporation of biochar was observed to significantly influence nutrient availability with SOC, SOM and TN reduced from 2.90-0.87, 5.00-1.50 and 0.13 to 0.4% respectively with B1 incorporation while B2 recorded slight increases on same parameters. Concentration of the heavy metals was found to be associated with pH levels as Pb and Al were strongly adsorbed to colloidal surfaces due to greater surface area of B1 and therefore, were not at hazardous to plants. It is concluded that application of locally pyrolyzed biochar for in situ metal immobilization can be feasible provided surface area of the amendment is increased.

Keywords: Amendment; Biochar; Contamination; Heavy metals; Incorporation

Date published: 2020-05-14