This study evaluated the phytotoxicity and bioconcentration of the insensitive munition compounds 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one in perennial ryegrass (Lolium perenne) grown in Sassafras sandy loam soil. A 21-day plant toxicity test identified sublethal concentrations for a subsequent 42-day bioconcentration study. In the 21-day test, DNAN exposure reduced seedling emergence at ≥ 50 mg kg−1, with shoot biomass significantly reduced at 100 mg kg−1 and completely inhibited at ≥ 250 mg kg−1. Root biomass declined at 50 mg kg−1 and was fully inhibited at 100 mg kg−1 and above. Chemical analysis revealed formation of the DNAN transformation product 2-amino-4-nitroanisole (2-ANAN), with total SumDNAN (DNAN + 2-ANAN) decreasing in both planted and unplanted soils. 2,4-Dinitroanisole bioconcentration factors (BCFs) remained < 1 in both roots and shoots. However, 2-ANAN showed higher accumulation in the 21-day study, with shoot and root BCFs of 36 and 8.0, respectively, and translocation factors (TFs) > 1. 3-Nitro-1,2,4-triazol-5-one was not detected in ryegrass tissues after 21 days. In the 42-day study, the DNAN soil concentration decreased by 58% in planted soil and 38% without plants. 2,4-Dinitroanisole was detected in both tissues, with shoot and root BCFs < 1 and a TF of 2.95. 2-Amino-4-nitroanisole was detected in only one replicate but exhibited shoot and root BCFs > 1 and a TF of 7.17. These results suggest that DNAN has low bioconcentration potential in ryegrass, but its transformation product 2-ANAN may accumulate and translocate more readily. 3-Nitro-1,2,4-triazol-5-one exhibited negligible uptake. Findings highlight the importance of assessing transformation products and exposure duration when evaluating the fate of munitions in terrestrial plant systems.

Individual effects of nitrogen-based energetic materials (EMs) 2,4-dinitrotoluene (2,4-DNT), 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), nitroglycerin (NG), and 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) on litter decomposition, an essential biologically-mediated soil process, were assessed using Orchard grass (Dactylis glomerata) straw in Sassafras sandy loam (SSL) soil, which has physicochemical characteristics that support "very high" qualitative relative bioavailability for organic chemicals. Batches of SSL soil were separately amended with individual EMs or acetone carrier control. To quantify the decomposition rates, one straw cluster was harvested from a set of randomly selected replicate containers from within each treatment, after 1, 2, 3, 4, 6, and 8 months of exposure. Results showed that soil amended with 2,4-DNT or NG inhibited litter decomposition rates based on the median effective concentration (EC50) values of 1122 mg/kg and 860 mg/kg, respectively. Exposure to 2-ADNT, 4-ADNT or CL-20 amended soil did not significantly affect litter decomposition in SSL soil at ≥ 10,000 mg/kg. These ecotoxicological data will be helpful in identifying concentrations of EMs in soil that present an acceptable ecological risk for biologically-mediated soil processes.

We investigated the toxicity of selenium (Se) to the soil invertebrates Folsomia candida (Collembola) and Enchytraeus crypticus (potworm). Studies were designed to generate ecotoxicological benchmarks for developing ecological soil screening levels (Eco‐SSLs) for risk assessments of contaminated soils. For the present studies, we selected Sassafras sandy loam, an aerobic upland soil with soil characteristics (low levels of clay and organic matter, soil pH adjusted from 5.2 to 7.1) that support high relative bioavailability of the anionic Se species that is typically found in aerobic soil. The Se was amended into soil as sodium selenate, subjected to weathering and aging using 21 d of alternating cycles of air‐drying/rehydration to 60% of the water‐holding capacity of the Sassafras sandy loam soil, under ambient greenhouse conditions. Effective concentrations at 20 and 50% (EC20 and EC50) levels for production of juveniles (reproduction) were 4.7 and 10.9 mg of Se/kg of soil (dry mass basis), respectively, for Collembola, and 4.4 and 6.2 mg/kg, respectively, for the potworms. The data enabled the derivation of toxicity benchmarks, contributing to the development of a soil invertebrate‐based Eco‐SSL of 4.1 mg/kg for Se. Environ Toxicol Chem 2018;37:846–853. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Energetic materials (EMs) bound to propellant residues can contribute to environmental risk and public health concerns. This work investigated how nitrocellulose, a common binding material in propellants, may control the release dynamics of nitroglycerin (NG) and 2,4-dinitrotoluene (2,4-DNT) from propellant residues. Batch adsorption/desorption experiments on nitrocellulose and re-interpretation on results from past leaching studies involving propellant-bound EMs were conducted. Mechanistic modeling of adsorption/desorption kinetics based on intra-particle diffusion (IPD) predicted aqueous intrinsic diffusivities (Diw) to within a factor of 2 of expected values. Furthermore, the IPD model was able to predict effective diffusivities (Deff) during the early leaching of NG from propellant residues to within a factor of 2 over a 3-log unit range. Prediction of leaching Deff's associated with fired residues was less successful probably due to the neglect of compositional and morphological heterogeneity within the residues. Close correlations were found between the early and late Deff's of residue-bound NG and between the fast- and slow-domain rate constants for both EMs, suggesting that the late leaching kinetics of bound-EMs may be empirically assessed from the early kinetics. This work illustrates that, in addition to dissolution, retarded diffusion through nitrocellulose matrix may also limit the overall release and transformation of residue-bound EMs in the field. Implications and limitations of the current study, and the steps forward are also presented.

Sustainable management of military ranges requires effective assessment of surface mobility and leaching potential of propellant compounds (PCs). Previous studies have focused mostly on PCs' dissolution from fired residues and their sorption to soil components. This work investigated the potential role of nitrocellulose, a major component in propellants, in the binding of PCs to propellant residues. Sorption isotherms of military grade nitrocellulose for dissolved nitroglycerine (NG) or 2,4-dinitrotoluene (2,4-DNT) was measured in batch experiments and were determined to be SNG=102.39(±0.05)CNG0.916(±0.032) and S2,4-DNT=103.08(±0.01)C2,4-DNT0.668(±0.010) (S and C in mg/kgnitrocellulose and mg/Lwat, respectively). Solid-to-water partitioning for NG and 2,4-DNT was 100 times greater in propellant residues than in typical military ranges soils. Since nitrocellulose can sorb NG and 2,4-DNT up to 23 and 5% of its mass, respectively, it can slow down, through retarded diffusion, the leaching of PCs from fired residues over the typical composition ranges of common propellants. The slow leaching of PCs from propellant grains in column studies can be better interpreted by considering their sorptive interaction with nitrocellulose in addition to dissolution kinetics. With nitrocellulose as the carrying matrix, residue-bound PCs may migrate farther and persist longer in subsurface environment.

Abstract : In separate, replicated experiments, we experimentally established wash-off coefficients (kw) for the chemical agent VX on grass, utilizing 1 and 3 L VX droplets at 0.017 (1 min), 1, and 4 h after dissemination. A 10 mm (0.39 in.) rain event at 0.017 h after dissemination washed off 95 and 83% of the 1 and 3 L VX droplets, respectively. At 1 h after dissemination, a 10 mm rain event washed off 0.03 and 0.5% of the 1 and 3 L VX droplets, respectively. At 0.017 h after dissemination, the kw values for 1 and 3 L droplets were 0.095 and 0.083 mm1, respectively. At 1 and 4 h after dissemination, the kw values for VX were approximately 3 orders of magnitude less than those at 0.017 h. Grass contaminated with 3 L VX droplets was exposed to multiple (10) 100 L light rain events, followed by multiple (10) surface wipes at 0.017, 0.5, 1, 4, and 24 h after dissemination. The cumulative proportions of 3 L VX droplets washed off by the rain events at 0.017 and 1 h after dissemination were 75.3 and 0.99%, respectively, and the cumulative proportions of VX wiped off after those rain events were 0.8 and 0.3%, respectively. Results from these investigations of agentplant interactions provide input for predictive models and functional information for Go/No-Go decisions that can affect soldiers on agent-contaminated battlefields.

: We investigated the toxicity of selenium (Se) to the soil invertebrate Folsomia candida using the Folsomia Reproduction Test (ISO 11267:1999). Studies were designed to generate ecotoxicological benchmarks for developing the ecological soil screening levels (Eco-SSLs) for risk assessments of contaminated soils. For this study, we selected aerobic upland soil, Sassafras sandy loam (SSL), with soil characteristics (low levels of clay and organic matter, soil pH adjusted high) that support high relative bioavailability of the anionic Se species that is typically found in aerobic soil. Se was amended into soil as sodium selenate, subjected to weathering-and-aging using 21 days of alternating cycles of air-drying/rehydration to 60 75% of the water-holding capacity of the SSL soil, under ambient greenhouse conditions. Effective concentration at 20 and 50% (EC20 and EC50) levels were 4.7 and 10.9 mg of Se/kg of soil, respectively, as determined on the basis of production of juveniles (reproduction) by F. candida exposed to Se weathered-and-aged in SSL soil. Toxicity benchmarks established in this study were submitted to the U.S. Environmental Protection Agency Eco-SSL Workgroup, and the EC20 value was used in developing soil invertebrate-based Eco-SSL for Se.

•Indigenous invertebrates were affected by explosive CL-20 in soil microcosms.•Microarthropods and nematodes showed contrasting sensitivities to CL-20 in soil.•Predatory mesostigmatid mites and predatory nematodes were most sensitive to CL-20.•Total numbers of nematodes were unaffected or increased in CL-20 treatments.

: We investigated the effects of individual nitrogen-based energetic materials (EMs) 2,4-dinitrotoluene (2,4-DNT), 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), nitroglycerin (NG), and 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) on decomposition, an essential soil process, utilizing Orchard grass (Dactylis glomerata) straw in Sassafras sandy loam (SSL) soil. Three pieces of 5-cm long internodular sections of straw were used to form a straw cluster. Pre-weighed straw clusters were placed in the soil in each 900 mL volume test container containing approximately 200 g of loosely packed EM-amended soil or carrier (acetone) control soil. After 1, 2, 3, 4, 6, and 8 months of exposure, one straw cluster was harvested from a set of randomly selected replicate containers from within each treatment to quantify the decomposition rates. The exposure concentrations of each EM in soil were analytically determined soils using the U.S. Environmental Protection Agency Method 8330A. The results showed that soil contamination with 2,4-DNT or NG can inhibit litter decomposition rates based on the EC50 values of 1122 mg/kg and 860 mg/kg, respectively. Exposure to 2-ADNT, 4-ADNT or CL-20 did not significantly affect litter decomposition in SSL soil at 10000 mg/kg. These ecotoxicological benchmarks can help identify concentrations of contaminant EM in soil that present an acceptable ecological risk for biologically-mediated processes in soil.

: This study was designed to produce scientifically defensible benchmark data for the development of ecological-based soil screening levels for 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) for terrestrial plants. The physical and chemical properties of different soils may alter the bioavailability and toxicity of TNT and RDX to plant species. We investigated individual ecotoxicities of TNT and RDX to alfalfa (Medicago sativa L.), Japanese millet (J. millet; Echinochloa crus-galli L. [Beauv.]), and perennial ryegrass (Lolium perenne L.) in five natural soils that varied in pH, organic matter, and clay contents. On the basis of EC50 values (the TNT or RDX concentrations that produce 50% reductions in selected measurement endpoints) and 95% confidence intervals for shoot fresh and dry masses (SDM), TNT weathered-and-aged (W-A) in soils significantly reduced (p 0.05) growth of alfalfa, J. millet, and perennial ryegrass. RDX W-A in soil was moderately inhibitory to growth of J. millet and perennial ryegrass in all five soils but did not affect growth of alfalfa. No statistically significant correlations between TNT toxicity and these soil properties were identified; however, statistically significant (p 0.05) inverse relationships were identified between the RDX EC50 values for perennial ryegrass SDM and soil clay content and pH.

: We investigated the effects of nitramine explosive, CL-20, on the soil microinvertebrate community in Sassafras sandy loam (SSL) soil using a 12 week soil microcosm assay. Freshly collected SSL soil was amended with CL-20 to prepare multiple treatment concentrations ranging from 0 (acetone control) to 10,300 mg kg 1. The selected CL-20 concentration range adequately assessed the concentration response relationships for total microarthropods and for individual microarthropod groups. Based on the number of taxonomic groups present in the individual treatments after 12 weeks, the overall composition of microarthropod community in SSL soil was not affected by exposure to CL-20. However, community structure analysis revealed greater sensitivity to CL-20 by predatory mesostigmatid mites. Microarthropod and nematode communities showed contrasting sensitivities to CL-20 in SSL soil. Total numbers of nematodes were unaffected or significantly (p 0.05) increased in the CL-20-treated soil compared with the control. Only the predator group among nematodes was consistently adversely affected by exposure to CL-20. The abundance of predatory nematodes decreased in a concentration-dependent manner throughout the 12 week exposure. Microcosm assays with corresponding community structure analysis can be used to validate the ecotoxicity data from standardized laboratory tests and complement and expand upon the ecotoxicological significance of data from standardized single-species toxicity tests.

: The toxicities of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to Folsomia candida (Collembola) were investigated using an ISO 11267:1998 test. Studies were designed to identify and characterize soil physicochemical parameters that may affect the acute (adult mortality) and chronic (reproduction) toxicities of TNT and RDX to F. candida and also to generate ecotoxicological benchmarks for development of ecological soil screening levels for risk assessments of contaminated soils. Soils studied included Teller and Sassafras sandy loams (TSL and SSL, respectively) and Richfield, Kirkland, and Webster clay loams (RCL, KCL, and WCL, respectively). Based on the effective concentrations for 50% of the population (EC50 values), for TNT weathered-and-aged in soil, chronic toxicity to F. candida was in the order KCL RCL TSL WCL SSL, and for RDX weathered-and-aged in soil, the order was RCL WCL TSL KCL SSL. Organic matter was the dominant soil property that mitigated TNT toxicity for adult survival in freshly amended soil; soil pH correlated strongly with acute toxicity benchmarks (the effective concentrations for 20% of the population [EC20 values] for adult survival) for RDX freshly amended in soil. These correlations were not sustained after weathering-and-aging of TNT or RDX in soil.

The authors investigated individual toxicities of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to the potworm Enchytraeus crypticus using the enchytraeid reproduction test. Studies were designed to generate ecotoxicological benchmarks that can be used for developing ecological soil-screening levels for ecological risk assessments of contaminated soils and to identify and characterize the predominant soil physicochemical parameters that can affect the toxicities of TNT and RDX to E. crypticus. Soils, which had a wide range of physicochemical parameters, included Teller sandy loam, Sassafras sandy loam, Richfield clay loam, Kirkland clay loam, and Webster clay loam. Analyses of quantitative relationships between the toxicological benchmarks for TNT and soil property measurements identified soil organic matter content as the dominant property mitigating TNT toxicity for juvenile production by E. crypticus in freshly amended soil. Both the clay and organic matter contents of the soil modulated reproduction toxicity of TNT that was weathered and aged in soil for 3 mo. Toxicity of RDX for E. crypticus was greater in the coarse-textured sandy loam soils compared with the fine-textured clay loam soils. The present studies revealed alterations in toxicity to E. crypticus after weathering and aging TNT in soil, and these alterations were soil- and endpoint-specific.

: Studies were designed to characterize soil physicochemical parameters that can affect the toxicities of 2,4,6- trinitrotoluene (TNT) or hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to Eisenia fetida earthworms and also to generate ecotoxicological benchmarks for development of ecological soil screening levels (Eco-SSLs) for ecological risk assessments of contaminated soils. Soils with varied physicochemical properties were tested, including Teller sandy loam (TSL), Sassafras sandy loam (SSL), Richfield clay loam (RCL), Kirkland clay loam (KCL), and Webster clay loam (WCL). Reproduction toxicity of TNT to E. fetida in freshly amended soils was in the order (greatest to least) of TSL SSL = KCL = RCL WCL. Weathering-and-aging of TNT in SSL, KCL, RCL, and WCL soils increased the toxicity to E. fetida compared with corresponding freshly amended treatments. Reproduction toxicity of RDX weathered-and-aged (W-A) in soil was comparable with that of TNT W-A in TSL, SSL, RCL, and WCL soils. No clear relationships were identified between TNT or RDX toxicities and the soil organic matter or clay contents or the pH levels. Toxicity benchmarks established utilizing TSL and SSL will be submitted to the U.S. Environmental Protection Agency Eco-SSL Workgroup for developing soil invertebrate-based Eco-SSLs for TNT and RDX.