Microecological characteristics of water bodies/sediments and microbial remediation strategies after 50 years of pollution exposure in ammunition destruction sites in China.

The effects of long-term ammunition pollution on microecological characteristics were analyzed to formulate microbial remediation strategies. Specifically, the response of enzyme systems, N/O stable isotopes, ion networks, and microbial community structure/function levels were analyzed in long-term (50 years) ammunition-contaminated water/sediments from a contamination site, and a compound bacterial agent capable of efficiently degrading trinitrotoluene (TNT) while tolerating many heavy metals was selected to remediate the ammunition-contaminated soil. The basic physical and chemical properties of the water/sediment (pH (up: 0.57-0.64), nitrate (up: 1.31-4.28 times), nitrite (up: 1.51-5.03 times), and ammonium (up: 7.06-70.93 times)) were changed significantly, and the significant differences in stable isotope ratios of N and O (nitrate nitrogen) confirmed the degradability of TNT by indigenous microorganisms exposed to long-term pollution. Heavy metals, such as Pb, Zn, Cu, Cd, Cs, and Sb, have synergistic toxic effects in ammunition-contaminated sites, and significantly decreased the microbial diversity and richness in the core pollution area. However, long-term exposure in the edge pollution area induced microorganisms to use TNT as a carbon and nitrogen sources for life activities and growth and development. The Bacteroidales microbial group was significantly inhibited by ammunition contamination, whereas microorganisms such as Proteobacteria, Acidobacteriota, and Comamonadaceae gradually adapted to this environmental stress by regulating their development and stress responses. Ammunition pollution significantly affected DNA replication and gene regulation in the microecological genetic networks and increased the risk to human health. Mg and K were significantly involved in the internal mechanism of microbial transport, enrichment, and metabolism of TNT. Nine strains of TNT-utilizing microbes were screened for efficient TNT degradation and tolerance to typical heavy metals (copper, zinc and lead) found in contaminated sites, and a compound bacterial agent prepared for effective repair of ammunition-contaminated soil significantly improved the soil ecological environment.

Oxygen-insensitive nitroreductase bacteria-mediated degradation of TNT and proteomic analysis.

2,4,6-trinitrotoluene (TNT) is a nitroaromatic compound that causes soil and groundwater pollution during manufacture, transportation, and use, posing significant environmental and safety hazards. In this study, a TNT-degrading strain, Bacillus cereus strain T4, was screened and isolated from TNT-contaminated soil to explore its degradation characteristics and proteomic response to TNT. The results showed that after inoculation with the bacteria for 4 h, the TNT degradation rate reached 100% and was transformed into 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT), and 2,6-diamino-4-nitrotoluene (2,6-DANT), accompanied by the accumulation of nitrite and ammonium ions. Through proteomic sequencing, we identified 999 differentially expressed proteins (482 upregulated, 517 downregulated), mainly enriched in the pentose phosphate, glycolysis/gluconeogenesis, and amino acid metabolism pathways. In addition, the significant upregulation of nitroreductase and N-ethylmaleimide reductase was closely related to TNT denitration and confirmed that the strain T4 converted TNT into intermediate metabolites such as 2-ADNT and 4-ADNT. Therefore, Bacillus cereus strain T4 has the potential to degrade TNT and has a high tolerance to intermediate products, which may effectively degrade nitroaromatic pollutants such as TNT in situ remediation in combination with other bacterial communities.

Defense mechanisms of alfalfa against cyclic tetramethylene tetranitramine (HMX) stress.

Much attention has been paid to the environmental toxicity and ecological risk caused by cyclic tetramethylene tetranitramine (HMX) pollution in military activity sites. In this study, the response mechanism of alfalfa plants to HMX was analyzed from the aspects of the photosynthetic system, micromorphology, antioxidant enzyme system, mineral metabolism, and secondary metabolism, in order to improve the efficiency of plant restoration. Exposure to 5 mg·L-1 HMX resulted in a significant increase in leaf N content and a significant increase and drift of the Fourier transform infrared protein peak area. Transmission electron microscopy images revealed damage to the root system subcellular morphology, but the plant leaves effectively resisted HMX pressure, and the photosynthetic parameters essentially maintained steady-state levels. The root proline content decreased significantly by 23.1-47.2 %, and the root reactive oxygen species content increased significantly by 1.66-1.80 fold. The roots regulate the transport/absorption of many elements that impart stress resistance, and Cu, Mn, and Na uptake is significantly associated with secondary metabolism. The metabolism of roots was upregulated in general by HMX exposure, with the main differences appearing in the content of lipids and lipid-like molecules, further confirming damage to the root biofilm structure. HMX causes an imbalance in the energy supply from oxidative phosphorylation in roots and generates important biomarkers in the form of pyrophosphate and dihydrogen phosphate. Interestingly, HMX had no significant effect on basic metabolic networks (i.e., glycolysis/gluconeogenesis and the tricarboxylic acid cycle), confirming that alfalfa has good stress resistance. Alfalfa plants apparently regulate multiple network systems to resist/overcome HMX toxicity. These findings provide a scientific basis for improving plant stress tolerance and understanding the HMX toxicity mechanism.

Physiological response mechanism of alfalfa seedlings roots to typical explosive cyclotrimethylene trinitramine (RDX).

This study explored the physiological response mechanism of alfalfa seedlings roots to a typical explosive, cyclotrimethylenetrinitramine (RDX), so as to improve the efficiency of phytoremediation. The response of plants to different levels of RDX were analyzed from the perspectives of mineral nutrition and metabolic networks. Exposure to RDX at 10-40 mg L-1 had no significant effect on root morphology, but the plant roots significantly accumulated RDX in solution (17.6-40.9%). A 40 mg L-1 RDX exposure induced cell gap expansion and disrupted root mineral metabolism, The key response elements, P, Cu, and Mg, were significantly increased by 1.60-1.66, 1.74-1.90, and 1.85-2.50 times, respectively. The 40 mg L-1 RDX exposure also significantly disturbed root basal metabolism, resulting in a total of 197 differentially expressed metabolites (DEMs). The main response metabolites were lipids and lipid-like molecules, and the key physiological response pathways were arginine biosynthesis and aminoacyl-tRNA biosynthesis. A total of 19 DEMs in root metabolic pathways, including L-arginine, L-asparagine, and ornithine, were significantly responsive to RDX exposure. The physiological response mechanism of roots to RDX therefore involve mineral nutrition and metabolic networks and are of great significance for improving phytoremediation efficiency.

[Distribution Characteristics and Pollution Assessment of Heavy Metals in Soils of a Testing Range].

Heavy metal pollution in testing ranges is one of the most widely concerning environmental problems. The ammunition static detonation test area, the bomb falling area, and the living area of a testing range in Jilin were selected as the study objects. The contents of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in 112 topsoil samples and two soil profiles were analyzed, and their distribution characteristics and sources were analyzed in detail. After that, the pollution degree and potential ecological risk of heavy metals were investigated using multiple pollution index assessment methods. The results showed that the average contents of As, Cd, Cu, Ni, and Zn in the soil of the ammunition static detonation test area were higher than the soil background values in Jilin province, and the contents of Cu, Zn, As, and Cd showed strong spatial heterogeneity. The average concentrations of As, Cd, and Ni in the soil of the bomb falling area exceeded their background values. The average contents of As and Cd in the soil of the living area were higher than the background values, and the variation coefficients of Pb, Cd, Zn, and Cr were relatively high, indicating that they may have been affected by human activities. In different test areas, the contents of As, Cr, Cu, Ni, and Zn in the soil samples were significantly different (P<0.05). The ammunition static detonation test area was more strongly affected by the test activities than the bomb falling area, and the heavy metal contents in the surface layer of the soil profile were significantly higher. There was no obvious vertical migration of heavy metals in the soil profiles. The results of multivariate statistics and source identification analysis using absolute principal component score-multiple linear regression (APCS-MLR) showed that Zn, Pb, and Cd were mainly affected by pollution sources related to test activities; Cr and Ni were mainly affected by natural sources of soil forming materials; and the sources of As and Cu were more complicated. The geo-accumulation index showed that Cd in the three areas and Ni in the bomb falling area belonged to pollution level 1 (uncontaminated to moderately contaminated). The Nemerow comprehensive pollution index showed that the pollution levels among the different functional areas were:living area>ammunition static detonation test area>bomb falling area, and the three functional areas were slightly polluted. The potential ecological risk index showed that the study area was at moderate ecological risk level, and Cd was considered to be the main soil pollution factor.

Microbial community structure and metabolome profiling characteristics of soil contaminated by TNT, RDX, and HMX.

This experiment was conducted to evaluate the ecotoxicity of typical explosives and their mechanisms in the soil microenvironment. Here, TNT (trinitrotoluene), RDX (cyclotrimethylene trinitramine), and HMX (cyclotetramethylene tetranitramine) were used to simulate the soil pollution of single explosives and their combination. The changes in soil enzyme activity and microbial community structure and function were analyzed in soil, and the effects of explosives exposure on the soil metabolic spectrum were revealed by non-targeted metabonomics. TNT, RDX, and HMX exposure significantly inhibited soil microbial respiration and urease and dehydrogenase activities. Explosives treatment reduced the diversity and richness of the soil microbial community structure, and the microorganisms able to degrade explosives began to occupy the soil niche, with the Sphingomonadaceae, Actinobacteria, and Gammaproteobacteria showing significantly increased relative abundances. Non-targeted metabonomics analysis showed that the main soil differential metabolites under explosives stress were lipids and lipid-like molecules, organic acids and derivatives, with the phosphotransferase system (PTS) pathway the most enriched pathway. The metabolic pathways for carbohydrates, lipids, and amino acids in soil were specifically inhibited. Therefore, residues of TNT, RDX, and HMX in the soil could inhibit soil metabolic processes and change the structure of the soil microbial community.

Analysis of the biodegradation and phytotoxicity mechanism of TNT, RDX, HMX in alfalfa (Medicago sativa).

The aim of this study was to reveal the mechanism underlying the toxicity of TNT (trinitrotoluene), RDX (cyclotrimethylene trinitroamine), and HMX (cyclotetramethylene tetranitramine) explosives pollution in plants. Here, the effects of exposure to these three explosives were examined on chlorophyll fluorescence, antioxidant enzyme activity, and the metabolite spectrum in alfalfa (Medicago sativa) plants. The degradation rates for TNT, RDX, and HMX by alfalfa were 26.8%, 20.4%, and 18.4%, respectively, under hydroponic conditions. TNT caused damage to the microstructure of the plant roots and inhibited photosynthesis, whereas RDX and HMX induced only minor changes. Exposure to any of the three explosives caused disturbances in the oxidase system. Non-targeted metabolomics identified a total of 6185 metabolites. TNT exposure induced the appearance of 609 differentially expressed metabolites (189 upregulated, 420 downregulated), RDX exposure induced 197 differentially expressed metabolites (155 upregulated and 42 downregulated), and HMX induced 234 differentially expressed metabolites (132 upregulated and 102 downregulated). Of these differentially expressed metabolites, lipids and lipid-like molecules were the main metabolites induced by explosives poisoning. TNT mainly caused significant changes in the alanine, aspartate, and glutamate metabolism metabolic pathways, RDX mainly caused disorders in the arginine biosynthesis metabolic pathway, and HMX disrupted the oxidative phosphorylation metabolic pathway. Taken together, the results show that exposure to TNT, RDX, and HMX leads to imbalances in plant photosynthetic characteristics and antioxidant enzyme systems, changes the basic metabolism of plants, and has significant ecotoxicity effects.

Biodegradation and physiological response mechanism of Bacillus aryabhattai to cyclotetramethylenete-tranitramine (HMX) contamination.

This study aims to reveal the biodegradation and interaction mechanism of cyclotetramethylenete-tranitramine (HMX) by a newly isolated bacteria. In this study, a bacterial strain (Bacillus aryabhattai) with high efficiency for HMX degradation was used as the test organism to analyze the changes in growth status, cell function, and mineral metabolism following exposure to different stress concentrations (0 and 5 mg L-1) of HMX. Non-targeted metabonomics was used to reveal the metabolic response of this strain to HMX stress. The results showed that when the HMX concentration was 5 mg L-1, the removal rate of HMX within 24 h of inoculation with Bacillus aryabhatta was as high as 90.5%, the OD600 turbidity was 1.024, and the BOD5 was 225 mg L-1. Scanning electron microscope (SEM) images showed that the morphology of bacteria was not obvious Variety, Fourier transform infrared spectroscopy (FTIR) showed that the cell surface -OH functional groups drifted, and ICP-MS showed that the cell mineral element metabolism was disturbed. Non-targeted metabonomics showed that HMX induced the differential expression of 254 metabolites (133 upregulated and 221 downregulated). The main differentially expressed metabolites during HMX stress were lipids and lipid-like molecules, and the most significantly affected metabolic pathway was purine metabolism. At the same time, the primary metabolic network of bacteria was disordered. These results confirmed that Bacillus aryabhattai has a high tolerance to HMX and can efficiently degrade HMX. The degradation mechanism involves the extracellular decomposition of HMX and transformation of the degradation products into intracellular purines, amino sugars, and nucleoside sugars that then participate in cell metabolism.

[Advances in peroxide-based decontaminating technologies].

With the boosting demand for eco-friendly decontaminants, great achievements in peroxide-based decontaminating technologies have been made in recent years. These technologies have been applied in countering chemical/biological terrorist attacks, dealing with chemical/biological disasters and destructing environmental pollutants. Recent research advances in alpha-nucleophilic/oxidative reaction mechanisms of peroxide-based decontamination against chemical warfare agents were reviewed, and some classical peroxide-based decontaminants such as aqueous decontaminating solution, decontaminating foam, decontaminating emulsions, decontaminating gels, decontaminating vapors, and some newly developed decontaminating media (e.g., peroxide-based self-decontaminating materials and heterogeneous nano-catalytic decontamination systems) were introduced. However, currently available peroxide-based decontaminants still have some deficiencies. For example, their decontamination efficiencies are not as high as those of chlorine-containing decontaminants, and some peroxide-based decontaminants show relatively poor effect against certain agents. More study on the mechanisms of peroxide-based decontaminants and the interfacial interactions in heterogeneous decontamination media is suggested. New catalysts, multifunctional surfactants, self-decontaminating materials and corrosion preventing technologies should be developed before peroxide-based decontaminants really become true "green" decontaminants.

[Feasibility study of preserving intercostobrachial nerve during dissection for breast carcinoma: evidences from a preliminary pathologic exploration].

OBJECTIVE: To determine the feasibility of preservation of intercostobrachial nerve (ICBN) in breast cancer. METHODS: During June 2004 to June 2006, 99 patients with operable breast cancer receiving an axillary lymph node dissection at our department were analyzed. The extirpated ICBN and ambient tissues were tested by HE staining to observe the pathological changes. RESULTS: In 96 (96.97%) cases with ICBN sacrificing, the nerves were not violated microscopically and the nerve cells remained intact. Of 28 patients with axillary lymphadenectasis, only 3 cases (10.71%) were found to have tumor emboli in the peri-neural vessels. CONCLUSION: The preservation of ICBN is a feasible and safe technique. The operative approach should be advocated. If at all possible, a surgeon should identify ICBN and preserve it.

Fabrication of novel supramolecular hydrogels with high mechanical strength and adjustable thermosensitivity.

An effective strategy was developed to fabricate the supramolecular hydrogels with high mechanical strength and adjustable thermosensitivity in aqueous systems, in which physical hydrogel precursors were first formed by the inclusion complexation of Pluronic F68/poly(epsilon-caprolactone) block copolymer end-capped with acryloyl groups with alpha-cyclodextrin (alpha-CD) and subsequently in situ UV photo-cross-linking was carried out. In this way, strong supramolecular hydrogels with elastic moduli greater than 100 000 Pa could be created, which is an order of magnitude higher than that previously achieved with related supramolecular hydrogels. Moreover, the stimuli-responsive property of these hydrogels could be tailored by changing the molar feed ratio of alpha-CD to the macromer. By X-ray diffraction and thermogravimetric analyses, the polypseudorotaxane structure of the inclusion complexes in as-obtained hydrogels was confirmed.

New semi-interpenetrating network hydrogels: synthesis, characterization and properties.

Amphiphilic hydrogels composed of aliphatic polyesters and poly(ethylene glycol) have potential applications in drug delivery, tissue engineering and other biomedical devices due to their advantageous biological properties, biocompatibility and biodegradability. However, they also exhibit some shortcomings in terms of their reactivity, swelling and mechanical properties. To address these limitations, new semi-interpenetrating network (semi-IPN) hydrogels based on poly(ethylene glycol)-co-poly(epsilon-caprolactone) (PEG-PCL) diacrylate macromer and hydroxypropyl guar gum (HPGG) were prepared by a low intensity ultraviolet (UV) light irradiation method, and characterized by FT-IR, DSC and WAXD analysis. Their properties were evaluated by investigating the swelling kinetics, dynamic mechanical rheology and the release behavior for bovine serum albumin (BSA). It was found that the introduction of the semi-IPN structure and HPGG decreased the crystallinity of PEG segments in the hydrogel, and improved the swelling and mechanical properties of the hydrogel, as well as lowered the release percentage of BSA from the hydrogel. Such hydrogel materials may have more advantages as a potentially interesting platform for the design of medical devices.The elastic modulus (G') and viscous modulus (G'') as a function of frequency for various hydrogel samples.

Supramolecular hydrogels induced rapidly by inclusion complexation of poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) block copolymers with alpha-cyclodextrin in aqueous solutions.

On the basis of the synthesis of water-soluble poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL) block copolymers, the supramolecular hydrogels were fabricated rapidly in aqueous solutions by their inclusion complexation with alpha-cyclodextrin. X-ray diffraction (XRD) analyses confirmed the supramolecular self-assemblies of alpha-cyclodextrin threaded onto amphiphilic PCL-PEG-PCL block copolymers. The resulting hydrogels display a high degree of elasticity, with the storage modulus (G') greater than the loss modulus (G'') over the entire range of frequency. Moreover, their viscosity greatly diminished as they were sheared. By controlling the molecular weight of the PEG component in the block copolymers and the content of the block copolymer, their rheological properties could be modulated. Such hydrogel materials have the potential to be used as tissue engineered scaffolds, biosensors in the human body, and carriers for controlled drug delivery.

Preliminary studies on methane flux from the ornithogenic soils on Xi-sha atoll, South China Sea.

Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from -4226.7 microg/(m2 x h) to 226.3 microg/(m2 x h) at the observation sites on Dong Island. High atmospheric CH4 consumption was observed from the ornithogenic soils on sunny days. CH4 uptake rates showed the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH4 consumption and the average flux was -141.8 microg/(m2 x h). However, disturbed soils via anthropogenic reclamation showed CH4 emissions and the average flux was 441.7 microg/(m2 x h). Therefore land use changes may have an important effect on the CH4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH4 fluxes. The wetland in salt marsh showed the CH4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH4 consumption, suggesting that CH4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH4 fluxes were also analyzed and discussed in this paper.

Preliminary studies on nitrous oxide emissions from the ornithogenic soils on Xi-sha atoll, South China Sea.

The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N2O fluxes from the ornithogenic soils ranged from 1.8 to 40.3 microg/(m2 x h) on Dong Island and 3.2 to 20.4 microg/(m2 x h) on Yongxing Island and their flux averaged 11.0 microg/(m2 x h) and 8.3 microg/(m2 x h), respectively. N2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2.1 microg/(m2 x h) and 2.4 microg/(m2 x h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N2O fluxes and the average was 4.8 microg/(m2 x h) and the soils via the reclamation showed the higher N2O fluxes and the average was 16.6 microg/(m2 x h) on Yongxing Island, suggesting that the changes of land use have an important effect on N2O fluxes from the ornithogenic soils. In addition, the N2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO3-, PO4(3-) and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.