Landfarming Process Effects on Biochemical Properties of Petroleum-Contaminated Soils

Abstract

The presence of petroleum contaminants in soil may be toxic to humans, plants, and soil microorganisms. Therefore, remediation of these compounds from the environment is vital. In this study, bioremediation of two petroleum-contaminated soils (S1 and S2) using a landfarming technique was evaluated. Investigation of the effect of this technique on biological and chemical properties of contaminated soil was also part of the goal. The results showed that about 50 and 57% of hydrocarbon contents were eliminated from soils S1 and S2 at the end of the experiment, respectively. Landfarming processes enhanced microbial respiration rate in both soils S1 and S2. Microbial biomass-nitrogen values in the landfarming plots were significantly (P < 0.05) higher than in the control plots (without landfarming operations). Urease activity increased by 21, 45, 26, and 23% in the landfarming plots as compared to the control plots for soil S2 at the end of first to the 4th month of the experiment, respectively. There was also significant difference (P < 0.05) in soil pH values between the landfarming treatment and control. Soil electrical conductivity in the landfarming plots was lower than in the controls. Total organic matter and total nitrogen contents in the landfarming plots were significantly lower in comparison to the control plots. It appears that improving soil aeration and exposing new layers of soil to sunlight and air as a result of landfarming operations facilitated the degradation of petroleum hydrocarbons.