[Effects of seed carrier-immobilized microorganisms on the growth of rapeseed and the remediation of petroleum hydrocarbon contaminated soil].

Abstract

Petroleum hydrocarbon pollutants in soil are challenging to biodegrade, negatively impacting plant growth as well as the metabolic activity and community structure of soil microorganisms. Microorganisms immobilized by seed carriers can synergistically contribute to the remediation of petroleum hydrocarbon-contaminated soil. We prepared a rape seed carrier with immobilized microorganism by seed coating (with a mixture of diatomaceous earth and bentonite as fillers) and microbial immobilization. A pot experiment was conducted with the following treatments: control (CK, neither seeds nor microorganisms added), bare rapeseed (T₁), rapeseed coated with diatomaceous earth and bentonite (T₂), free-living Pseudomonas aeruginosa added (T₃), rapeseed coated with diatomaceous earth and bentonite plus free-living P. aeruginosa (T₄), and rapeseed coated with diatomaceous earth and bentonite immobilized with P. aeruginosa (T₅). We measured rape seed growth, rhizosphere microbial community structure, and petroleum hydrocarbon removal efficiency. The results showed that 1) There were no significant difference in seed germination rate among T₁, T₂, T₄, and T₅ treatments. Compared to T₁, leaf length, root length, biomass, and soluble protein content of rape seed significantly increased in T₄ and T₅ treatments, while T₂ treatment showed no significant effect. Leaf width, stem length, chlorophyll content, and superoxide dismutase activity of rape seed in T₂, T₄, and T₅ treatments were significantly higher than T₁, while malondialdehyde content was signi-ficantly lower. 2) Compared to CK, the removal rate of petroleum hydrocarbon in the T₁, T₂, T₃, T₄, and T₅ treatments increased by 0.8, 1.6, 0.5, 1.8, and 2.2 times, respectively. The T₅ treatment achieved the highest petro-leum hydrocarbon removal rate of 54.0%. Soil dehydrogenase activity in all treatments increased significantly, with a positive correlation with the petroleum hydrocarbon removal rate (r=0.893). 3) The T₅ treatment had the highest soil microbial α diversity and the abundances of Chloroflexi and Acidobacteria. In conclusion, seed carriers with immobilized microorganisms could regulate plant growth, modify the structures of microbial communities, enhance the biological activity of soil enzymes, thereby improving petroleum hydrocarbon removal efficiency. This provides a novel environmentally friendly approach for the joint remediation of petroleum hydrocarbon-polluted soil by plants and microorganisms.