Using Magnetic Susceptibility for Assessing Total Petroleum Hydrocarbon Biodegradation in Pseudomonas aeruginosa and Marinobacter hydrocarbonoclasticus-Inoculated Soils

Monitoring changes in total PHs (TPHs) during bioremediation is of utmost importance for researchers and landowners to remediate their soils. Monitoring changes of TPH content during bioremediation is essential and it is difficult and expensive by traditional approaches. Therefore, finding a cost-effective and easy technique to monitor the TPH content during the bioremediation is very crucial. Magnetic susceptibility as the fast and effective way in this regard was assessed. This study investigated the effectiveness of magnetic susceptibility (χ_lf) as an economical, quick, and efficient tool for monitoring total petroleum hydrocarbon (TPH) content during its biodegradation by non-native bacteria, Pseudomonas aeruginosa and Marinobacter hydrocarbonoclasticus, in an incubation experiment. Two different textual soils were contaminated with four levels of crude oil, inoculated with Pseudomonas aeruginosa and Marinobacter hydrocarbonoclasticus, and then incubated at 22ºC and 80% of field capacity moisture content for 30 and 90 days. TPH and χlf were measured in the initial and treated samples_. The results showed that soil texture did not significantly (P < 0.05) affect the biodegradation rate. TPH content decreased significantly (P < 0.01) after 30 days of incubation (> 60%), especially when inoculated with both bacterial strains. However, no significant differences were observed between the two bacterial strains in two incubation periods. Conversely, χ_lf, iron forms, and magnetite/maghemite content increased significantly (P < 0.05) following incubation, specifically in the presence of both bacteria. These changes were likely attributed to biochemical processes during hydrocarbon biodegradation. The non-linear regression equation demonstrated that χ_lf explained 86% of the variability in TPH in the studied soils. Thus, χ_lf may serve as a reliable and rapid technique for monitoring TPH changes during soil remediation practices for end-users and governing bodies.