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

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-trazine-1,3,5-triazine (RDX) and 2,135 mg octahydrol-1,3,5,7-tetranitro-1,3,5,7-tetracine (HMX) kg(-1) soil. Extractable nitrate-N wais as high as 315 and ammonium-N reached 150mg 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 colon forming units (CFU)q(-1) soil. In the most several 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-tern contamination by high by high-concentrations of explosives.