Laboratory Column Evaluation of High Explosives Attenuation in Grenade Range Soils

Abstract

High explosives (HEs) deposited on military ranges can leach through the soil and contaminate groundwater. We examined the transport and fate of HEs in laboratory columns containing soils from two hand grenade bays (Bays C and T) and the impact of organic amendments on biodegradation. Soil characteristics were similar; however, Bay C had somewhat higher clay and organic C. Experimental treatments included addition of crude glycerin and lignosulfonate, and parallel control columns. Experimental results showed extensive 2,4,6-trinitrotoluene (TNT) degradation with minimal leaching, consistent with prior batch microcosm results. Amendment addition enhanced TNT degradation in both Bays C and T compared with controls. Although hexahydro-1,3,5-trinitro-1,3,5-triazine (Royal Demolition Explosive, or RDX) did not biodegrade in prior aerobic batch microcosms, 64 to 77% of RDX biodegraded in untreated soil columns with O present in the mobile soil gas. The RDX biodegradation was likely associated with short-term anoxic conditions or anoxic micro-niches. In nearly saturated Bay C columns, RDX removal increased to >92%. Amendment addition to unsaturated Bay T columns increased RDX removal to >86%. In one column, the soil remained anoxic (O < 5% by volume) for about a year after amendment addition, significantly reducing RDX leaching. Nitroso degradation products were produced equivalent to 9 to 39% of the RDX degraded, with most retained in the soil (9-37%) and 0 to 3% in the effluent. These results demonstrate that RDX biodegradation can occur in soils with measurable O, and that amendment addition can reduce RDX leaching by stimulating anaerobic biodegradation.

Natural and Enhanced Attenuation of Explosives on a Hand Grenade Range

“…Similar results were observed by Won and Borden (2017) in laboratory column experiments with Bay T soil. Six to twelve months after GL+LS addition, small amounts of TOC and Cl were discharged in the column effluent, followed by a rapid decline in NO 3 , and increase in Mn, and removal of RDX.…”

“…However, nitrate and RDX levels recovered much more slowly due to the low drainage rates and long travel time through the soil. Similar results were observed in laboratory column experiments containing Bay C soil, where saturated, anoxic conditions reduced RDX leaching by 92% (Won and Borden, 2017). Larson et al (2008) observed similar results at Fort Jackson, SC, where RDX levels varied from <1 to 3200 μg L −1 (average = 435 μg L −1 ) in suction lysimeters installed below an untreated grenade bay.…”

“…Half‐lives of RDX varied from 5 to 14 d, with more rapid degradation with added glycerin and/or Norlig A lignosulfonate. In variably saturated column experiments without amendments, extensive RDX removal was observed in columns containing Bay C soil, but there was lower removal in columns with Bay T soil (Won and Borden, 2017). Addition of glycerin and lignosulfonate (GL+LS) to the surface of the Bay T columns, significantly increased RDX removal.…”

Predicting the transport of 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO) in sandy and sandy loam soils

“…These experiments can be classified into static, in which the outcome does not change over time, and dynamic, in which the outcome changes over time (UK Government Office for Science, 2018). Static experiments, such as bottle flask tests and microcosms have been performed to study processes affecting persistence such as the degradation rate of explosives and reversible and irreversible sorption onto soil (Halasz et al, 2018;Indest et al, 2017;Krzmarzick et al, 2015;Won and Borden, 2017). In this way, key parameters for defining transport processes such as partition coefficients (matrix-water, organic carbon-water, octanol-water etc…) and half-life times of IHE in different media have been quantified.…”