Bioaccumulation kinetics of the conventional energetics TNT and RDX relative to insensitive munitions constituents DNAN and NTO in Rana pipiens tadpoles

Abstract

The manufacturing of explosives and their loading, assembling, and packing into munitions for use in testing on training sites or battlefields has resulted in contamination of terrestrial and aquatic sites that may pose risk to populations of sensitive species. The bioaccumulative potential of the conventional explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and of the insensitive munitions (i.e., less shock sensitive) compound 2,4-dinitroanisole (DNAN) were assessed using the Northern leopard frog, Rana pipiens. Trinitrotoluene entering the organism was readily biotransformed to aminodinitrotoluenes, whereas no transformation products were measured for RDX or DNAN. Uptake clearance rates were relatively slow and similar among compounds (1.32-2.19 L kg(-1) h(-1) ). Upon transfer to uncontaminated water, elimination rate was very fast, resulting in the prediction of fast time to approach steady state (5 h or less) and short elimination half-lives (1.2 h or less). A preliminary bioconcentration factor of 0.25 L kg(-1) was determined for the insensitive munitions compound 3-nitro-1,2,4-trizole-5-one (NTO) indicating negligible bioaccumulative potential. Because of the rapid elimination rate for explosives, tadpoles inhabiting contaminated areas are expected to experience harmful effects only if under constant exposure conditions given that body burdens can rapidly depurate preventing tissue concentrations from persisting at levels that may cause detrimental biological effects.

Toxicity of the conventional energetics TNT and RDX relative to new insensitive munitions constituents DNAN and NTO in Rana pipiens tadpoles

“…The companion study to the present study, described in Lotufo et al [22], reported a bioconcentration factor of 0.9 mg/L for TNT in R. pipiens tadpoles. Furthermore, Lotufo et al [22] demonstrated that the body residue of TNT approaches steady state in as little as 1 h and that TNT also depurates rapidly, achieving non-detectible tissue concentrations in less than 6 h upon transfer to clean water. In total, these results indicate that TNT body residues in R. pipiens tadpoles are expected to closely track the concentration of TNT in water.…”

“…Similar to TNT, both DNAN and NTO were not observed to bioconcentrate in R. pipiens tadpoles, with each having a bioconcentration factor < 1, and had even more rapid uptake and elimination kinetics than TNT . These results indicate that DNAN and NTO body residues in R. pipiens tadpoles closely track environmental concentrations (in water); however, the tadpoles do not appear to be as adversely affected by sustained tissue residues of DNAN and NTO compared with TNT.…”

Accumulation of 2,4‐dinitroanisole in the earthwormEisenia fetidafrom chemically spiked and aged natural soils

“…Among aquatic species, the toxicity of DNAN has been reported for the microalga Pseudokirchneriella subcapitata , the bioluminescent bacterium Vibrio fischeri , the cladocerans Ceriodaphnia dubia and Daphnia pulex , the fathead minnow Pimephales promelas , and tadpoles of Rana pipiens . In addition, exposures of R. pipiens tadpoles to water dosed with DNAN resulted in very low bioconcentration factors (BCFs, <2 L/kg) and rapid depuration of body burdens after transfer to clean water (elimination half‐life <1.2 h) . Limited information on the toxicity and bioaccumulation of DNAN in soil invertebrates is available.…”

Right on target: using plants and microbes to remediate explosives

“…A log K ow value greater than 5 is a predictive indicator for bioaccumulation. Unlike famously bioconcentrating organic pollutants such as DDT (dichlorodiphenyltrichloroethane) and polychlorinated biphenyls (PCBs), which have log K ow values of 4.89 to 6.91; and upwards of 6.47, respectively, values for TNT, DNAN, RDX, and NTO are low, and these compounds, fortunately, have a correspondingly low tendency to bioconcentrate (Lotufo et al 2015).…”