Reshaping the microenvironment and bacterial community of TNT- and RDX-contaminated soil by combined remediation with vetiver grass (Vetiveria ziznioides) and effective microorganism (EM) flora

Explosive pollutants remaining in global soils are serious threats to human health and ecological safety. Soils contaminated by trinitrotoluene (TNT) and cyclotrimethylene trinitramine (RDX) are simulated in this study and remediated using vetiver grass and effective microorganism (EM) flora to determine the efficacy of combined remediation in reshaping the microenvironment and bacterial community of soils contaminated by explosives. The degradation rates of TNT and RDX after 60 days of combined remediation were 95.66% and 84.37%, respectively. Soil microbial activity and enzyme activities related to the nitrogen cycle were upregulated. The content of soil elements in the remediation group changed significantly. Vetiver remediation increased the diversity and significantly changed the structure of the microbial community. Notably, bacteria, such as Sphingomonadaceae and Actinobacteriota, which can degrade explosives, occupied the soil niche, and the Proteobacteria and Bacteroidota, which are involved in sugar metabolism, showed particularly increased abundance. The metabolism of soil carbohydrates, fatty acids, and amino acids was upregulated in the vetiver, EM flora, and combined vetiver+EM flora remediation groups, and the most significantly upregulated pathway was galactose metabolism. The combined vetiver and EM flora treatment of soil contaminated by explosives greatly improved the ecology of the soil microenvironment.