Trends in environmental monitoring of high explosives present in soil/sediment/groundwater using LC-MS/MS.

Environmental contamination by explosives occurs due to improper handling and disposal procedures. Explosives and their transformation products pose threat to human health and the ecosystem. Trace level detection of explosives present in different environmental matrices is a challenge, due to the interference caused by matrix components and the presence of cocontaminants. Liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) is an advanced analytical tool, which is ideal for quantitative and qualitative detection of explosives and its metabolites at trace levels. This review aims to showcase the current trends in the application of LC-MS/MS for detecting explosives present in soil, sediment, and groundwater with detection limits ranging from nano to femtogram levels. Specificity and advantages of using LC-MS/MS over conventional analytical methods and various processing methods and techniques used for sample preparation are discussed in this article. Important application aspects of LC-MS/MS on environmental monitoring include site characterization and degradation evaluation. Studies on qualitative and quantitative LC-MS/MS analysis in determining the efficiency of treatment processes and contamination mapping, optimized conditions of LC and MS/MS adopted, role of different ionization techniques and mass analyzers in detection of explosives and its metabolites, relative abundance of various product ions formed on dissociation and the levels of detection achieved are reviewed. Ionization suppression, matrix effect, additive selection are some of the major factors which influence MS/MS detection. A summary of challenges and future research insights for effective utilization of this technique in the environmental monitoring of explosives are presented.

Bioaugmentation for remediation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) contaminated soil using a clay based bioformulation.

Bioaugmentation is an important remediation strategy for hazardous organic compounds. A microcosm study was conducted to evaluate the remediation of soils contaminated with hazardous high explosive, Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) using an eco-friendly bioformulation. Janibacter cremeus, an enriched indigenous soil bacterium isolated from the explosive contaminated site was immobilized in a mixture of calcite and cocopeat for bioaugmentation. The developed bioformulation showed a consistent viability for 150 days, at 4 °C storage conditions. HMX at field concentrations was degraded in microcosms for 35 days under unsaturated (aerobic) and saturated (anoxic) moisture conditions. Negligible degradation was observed under unsaturated moisture conditions, whereas, saturated conditions led to substantial decrease in HMX. Mass spectrometric (MS) analysis revealed the formation of nitroso derivatives of HMX during the anoxic degradation. Also, observed was the presence of 5-hydroxy-4-nitro-2,4-diazapentanal, a precursor of 4- nitro-2,4-diazabutanal, which eventually could be mineralized. An inexpensive and natural carrier when chosen for immobilization of explosive degrading microbes was found to be effective in the in situ remediation of explosive.

A novel egg shell-based bio formulation for remediation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) contaminated soil.

Environmental contamination by secondary explosive has been posing threat to human health and the ecosystem. We investigated the potential of a novel bioformulation developed from poultry waste for the bioremediation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) contaminated soils. Eggshells and additives immobilized with an indigenous explosive degrading microbe Janibacter cremeus were utilized for the development of the wettable powder bioformulation. Treatments carried out under unsaturated and saturated soil conditions resulted in 62 and 73 % removal of RDX respectively in 35 days meeting the soil clean up goals. The saturated treatment sets exhibited better microbial growth during the study in terms of live cell count and total enzyme activity. The bacteria, J. cremeus was observed to exhibit significant release of nitrite under both unsaturated as well as saturated conditions. Mass spectrometric studies showed that, both the conditions lead to the formation of nitroso-derivatives of RDX. But under saturated condition, an intermediate, 5-hydroxy-4-nitro-2,4-diazapentanal was observed which is a precursor to 4-nitro-2,4-diazabuatnal ultimately leading to mineralization. An accessible bio resource from poultry waste when used as a carrier for explosive degrading microbe has proven effective for in situ remediation of explosive contaminated soils.