Long-Term Explosive Contamination in Soil: Effects on Soil Microbial Community and Bioremediation

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Abstract
Explosive contamination in soil is a great concern for environmental health. Following 50 years of munitions manufacturing and loading, soils from two different sites contained ≥ 6,435 mg 2,4,6-trinitrotoluene (TNT), 2,933 mg hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,135 mg octahydrol-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) kg− 1 soil. Extractable nitrate-N was as high as 315 and ammonium-N reached 150 mg N kg− 1 soil. Water leachates in the highly contaminated soils showed near saturation levels of TNT and RDX, suggesting great risk to water quality. The long-term contamination resulted in undetectable fungal populations and as low as 180 bacterial colony forming units (CFU) g–1 soil. In the most severely contaminated soil, dehydrogenase activity was undetectable and microbial biomass carbon was very low (< 3.4 mg C mic kg–1 soil). The diminished biological activity was a consequence of long-term contamination because short-term (14 d) contamination of TNT at up to 5000 mg TNT kg–1 soil did not cause a decline in the culturable bacterial population. Natural attenuation may not be a feasible remediation strategy in soils with long-term contamination by high concentrations of explosives.

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