Enhancing the attenuation of explosives in surface soils at military facilities: Combined sorption and biodegradation

Abstract

This research evaluated soil amendments designed to enhance the adsorption and biodegradation of explosives at military training facilities, thus minimizing their potential for transport to subsurface environments. Several carbon cosubstrates were tested in soil slurries for their ability to stimulate the biodegradation of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (royal demolition exposive [RDX]), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (high-melting explosive [HMX]) by indigenous soil microorganisms. Crude soybean oil and molasses stimulated mineralization of RDX (30-40%) and HMX (approximately 10%). The TNT was not significantly mineralized in any of the treatments, but high-performance liquid chromatography (HPLC) analysis indicated extensive transformation of TNT to amino-containing compounds. The biodegradation of explosives was then examined in unsaturated soil microcosms amended with crude soybean oil and molasses combined with sphagnum peat moss and sawdust. Minimal TNT mineralization was observed, and HMX mineralization was only observed with molasses addition. In contrast, RDX mineralization was extensive in microcosms amended with soybean oil or molasses. The presence of peat moss decreased soybean oil-stimulated RDX mineralization by approximately 5%, but resulted in about 5% greater RDX mineralization compared with molasses only. Sawdust markedly decreased mineralization regardless of cosubstrate type. Mass balance results indicated that the formation of bound residues likely was occurring, especially for TNT. These results indicate that the application of inexpensive adsorbents and cosubstrates to soils may significantly improve the protection of groundwater resources underlying live fire ranges.

Microbial Degradation of 2,4,6-Trinitrotoluene In Vitro and in Natural Environments

“…The degradation of TNT by microorganisms has been extensively studied for many years and the results have been compiled in numerous reviews (Fritsche et al 2000;Hawari et al 2000;Lenke et al 2000;Spain et al 2000;Esteve-Núñez et al 2001;Rodgers and Bunce 2001;Rosser et al 2001;van Aken and Agathos 2001;Heiss and Knackmus 2002;Fuller et al 2004;Lewis et al 2004;Schrader and Hess 2004;Zhao et al 2004;Stenuit and Agathos 2010;Rylott et al 2011). Some basic reactions are listed in Table 1.…”

“…In the past, various bioremediation technologies have been developed for soil environments (Held et al 1997;Daun et al 1998;Drzyzga et al 1999;Lenke et al 2000;Fuller et al 2004;Kröger et al 2004;Lewis et al 2004). Biological ex situ methods rely upon the microbial community to treat contaminated media which include soil slurry reactors, land farming and soil composting.…”

“…As a result, many sites used for TNT production have become seriously contaminated with the explosive and related compounds (Fuller et al 2004; Lewis et al 2004). Typical contaminated sites may contain up to 10 g/kg TNT in soils and up to 100 mg/l in water.…”

“…The reductive reactions are the basis of several treatment processes for the bioremediation of TNT-contaminated soils (Breitung 1996;Lenke et al 1998Lenke et al , 2000Fuller et al 2004;Lewis et al 2004). However, there is a lack of biological strategies to clean up contaminated water ecosystems.…”

Effect of plant extract on the degradation of nitroaromatic compounds by soil microorganisms

“…It has been demonstrated that diVerent media giving comparable plate counts can be used to select for diVerent bacterial types, leading to diVerent estimates of diversity for the same soil [1,20]. In addition, bacteria's ability to degrade TNT and other explosives can be considerably inXuenced by various amendments added to the explosives-containing medium [4,9].…”