Soil Fertility Status and Degradation of Munitions Constituent Contaminated Soil.

Current models for predicting the environmental fate of munitions constituents (MC) in soils are solely based on chemical distribution parameters, and neglect the larger considerations with respect to other soil parameters. We are working towards a new model based on the whole soil activity for predicting the long-term residence time and fate of MC with connection to agronomic soil fertility concepts. These relationships are demonstrated by correlating experiments involving full physical and chemical characterization of 8 taxonomically distinct soils, with batch reactor studies determining MC degradation potential. Soils were incubated in a slurry for 10 days in a closed reactor system with temperature, pH, and Eh readings recorded every 24-h. Air and slurry samples were taken 8 times within the incubation period. Carbon dioxide production, TNT, RDX, degradation product concentrations in solution and sediment, and solution nutrient concentrations were collected to obtain a full picture of soil chemistry changes due to microbial activity in response to additions of TNT.  Multivariate analysis was used to determine the main factors impacting degradation rate. Principle components analysis showed that TNT degradation was possibly correlated with boron, percent organic matter, cation exchange capacity, zinc, and potential buffering capacity of potassium. Degradation rate of RDX was possibly correlated with salt content including concentrations of magnesium, calcium, sodium, potassium; negative ions of sulfur, phosphorus, and chloride; and the potential buffering capacity of phosphorus. These results suggest that there are different factors influencing the degradation rate for TNT and RDX, although further analysis is required to verify these findings.