Abstract:

Abstract:

Abstract:Energetic compounds represented by trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) are highly toxic. When released into the environment, these energetic compounds will undergo complex redistribution, migration and transformation in soil-water-organism system, and pose hazards to ecosystems and human health. According to the pollution status of energetic compounds in domestic and foreign sites, the environmental behaviors of TNT, RDX and HMX in soil such as dissolution/precipitation, volatilization, adsorption/desorption, photolysis, hydrolysis, reduction, microbial degradation and plant uptake and transformation were reviewed. The physical and chemical properties of explosives and soils, and the effect of on-site environmental conditions on these complex environmental behaviors were also analyzed. The latest research on the environmental behavior of hexanitrohexaazaisowurtzitane (CL-20) and other novel explosives was briefly introduced. Based on the current research status, it is recommended that more attention should be paid to marine environmental ammunition pollution and combined pollution between energetic compounds and heavy metals in the future, and more attention should be paid to the application of the advanced technologies, such as compound-specific stable isotope analysis, to the environmental behavior and fate of explosives.

Abstract:Typical military explosives, such as trinitrotoluene（TNT）, hexogen, octogen, pentaerythritol tetranitrate, can cause a variety of toxic effects on mammalian tissues and organs such as liver, kidney, blood and nerves. This paper reviewed the toxic effects and mechanisms of typical explosives, and briefly summarized their cellular, microbial and animal toxic effects, as well as the epidemiological statistics of occupational populations. Taking TNT as an example, the review also introduced the toxic mechanisms of typical explosive, emphasizing the oxidative stress and the reaction of TNT metabolites with protein and DNA. Finally, it was pointed out that the current toxicity study of explosives mainly focuses on the testing of toxicity, while the understanding on toxic mechanisms of explosives is lacking. We presented future research priorities. For example, the quantitative structure-activity relationship between explosive molecules and biological toxicity by the machine learning technology, the investigation of toxic mechanism for nitroaromatic explosives, including hemoglobinemia, toxic cataract, carcinogenic and teratogenic, should be paid more attention.

Abstract:To further study the biotransformation process and producing enzyme properties of bacterial strain of Rhodobacter sphaeroides to HMX, the effects of different carbon sources, nitrogen sources and metal ions on the biotransformation efficiency of HMX of the strain and its growth were studied. The intermediate metabolites of HMX degraded by Rhodobacter sphaeroides were analyzed by liquid chromatography-mass spectrometry (LC-MS), and the possible degradation pathways were presumed. The effects of different conditions on the specific activity of the enzymes produced by the strain were determined. The zymograms were analyzed by polyacrylamide gel electrophoresis. The results show that the optimum carbon source, combined nitrogen source and metal ion for transforming HMX by the strain are malic acid, (NH₄)₂SO₄ and yeast extract, Ca²⁺, respectively. When the initial concentration of HMX is 100 mg·L^-1, after 96 h of culture, three substances can be detected: two HMX nitroso derivatives (mononitroso mNs-HMX and dinitroso dNs-HMX), methine dinitramine (MEDINA), and the mass-to-charge ratios of their mother ions are 279, 263 and 136, respectively. The possible degradation pathways presumed have two branches. One branche is that HMX is reduced to mNs-HMX and dNs-HMX by reductase, the other branche is that HMX is transformed and open-loop cleavaged into methine dinitramine by hydrolase. The specific activity of enzyme and polyacrylamide gel electrophoresis experiments show that the specific activity of the enzyme produced by the strain is significantly promoted when the concentration of HMX is 75 mg·L^-1 and 100 mg·L^-1, while when the concentration of HMX is 125 and 50 mg·L^-1, the specific activity of the enzyme produced by the strain has an inhibitory effect. When pH is 7, the specific activity of the enzyme produced by the strain is the highest.

Abstract:With p-nitrophenol (PNP) as the target pollutant, the degradation characteristics of PNP by Rhodobacter sphaeroides H strain were studied. The degradation conditions were optimized by single factor test and response surface analysis, and the degradation ability of H strain to PNP was improved. Different reaction systems have been set up to prove that H strain living cells are the main body of degrading PNP, and can degrade PNP under anaerobic light, anaerobic darkness, aerobic light and aerobic darkness. The single factor experiments show that the significant influencing factors are initial concentration of PNP, pH value and temperature. The optimal degradation conditions after response surface optimization are: initial concentration of PNP is 81.01 mg·L^-1, pH value is 8.09 and temperature is 30.49 ℃. The predicted value of PNP degradation rate is 92.3%, which is 1.2%(<2%) different from the actual value(91.1%). Under the optimum conditions, the relationship between the growth of H strain and the concentration of PNP with time shows that the concentration of PNP decreased from 81.01 mg·L^-1 to 20.33 mg·L^-1 within 96 hours of the growth adaptation period of H strain, and the corresponding degradation rate is 74.9%. Then, in the exponential growth period of 96-168 hours, PNP is rapidly degraded, and the degradation rate reaches 91.1%. At the same time, the first-order kinetic equation of PNP degradation of H strain under this condition was fitted.