Influence of Pseudomonas aeruginosa-based biopolymer on mitigating soil erosion and heavy metal dispersion

Extreme weather phenomena caused by climate change have exacerbated soil erosion and the subsequent dispersion of pollutants. Pseudomonas aeruginosa is known to contribute to the remediation of polluted water and reduce the geochemical mobility of heavy metals in contaminated soil. However, studies on the influence of biopolymers produced by soil microbes and P. aeruginosa on physical soil properties and soil erosion are limited. We aimed to investigate the influence of soil microbes on the mitigation of soil erosion and geochemical dispersion of heavy metals using a naturally occurring microbial substance, P. aeruginosa-based biopolymer (PBB). The PBB comprised carboxyl, hydroxyl, and amine surface functional groups; consequently, the biopolymer effectively sequestered Cd (maximum sorption capacity q_m = 45.7 mg/g), Cu (q_m = 26.7 mg/g), Pb (q_m = 64.9 mg/g), and Zn (q_m = 26.1 mg/g) in the solution. The PBB amendment of the soil improved the physical properties associated with soil erosion, increasing soil aggregation stability and shear strength by 41.6% and 36.8%, respectively. The extraction of heavy metals from soil via synthetic precipitate leaching decreased by 54.2% following the PBB amendment, and a negative correlation was observed between soil aggregate stability and heavy metal extraction, indicating that this microbial substance could immobilize pollutants by adsorbing cationic metal ions and inhibiting water-induced disaggregation. In the soil erosion experiments, soil loss and heavy metal extraction decreased by 70.9% and 43.8%, respectively, following the PBB amendment. These aggregation and sorption effects of the PBB underscore the potential of soil microbes to mitigate soil erosion and immobilize the geochemical dispersion of heavy metals, thereby contributing to the conservation of soil and water quality in areas surrounding contaminated slopes and heavy metal-contaminated areas, such as cut slopes, agricultural fields, mine dumps, and dams.