Monitored natural attenuation of explosives

Explosives are subject to several attenuation processes that potentially re duce concentrations in groundwater over time. Some of these processes are w ell defined, while others are poorly understood. The objective of the proje ct was to optimize data collection and processing procedures for evaluation and implementation of monitored natural attenuation of explosives. After c onducting experiments to optimize data quality, a protocol was established for quarterly monitoring of thirty wells over a 2-year period at a former w aste disposal site. Microbial biomarkers and stable isotopes of nitrogen an d carbon were explored as additional approaches to tracking attenuation pro cesses. The project included a cone penetrometry sampling event to characte rize site lithology and to obtain sample material for biomarker studies. A three-dimensional groundwater model was applied to conceptualize and predic t future behavior of the contaminant plume. The groundwater monitoring data demonstrated declining concentrations of explosives over the 2 years. Biom arker data showed the potential for microbial degradation and provided an e stimate of the degradation rate. Measuring stable isotopic fractions of nit rogen in TNT was a promising method of monitoring TNT attenuation. Overall, results of the demonstration suggest that monitored natural attenuation is a viable option that should be among the options considered for remediatio n of explosives-contaminated sites.