Binding of trinitrotoluene (TNT) to water extractable humus

Solid-state ¹⁵N NMR was applied to the aqueous extracts of a ¹³C-enriched plant slurry (Lolium perenne), anaerobically incubated with ¹⁵N₃-trinitrotoluene (TNT). Almost all ¹⁵N₃-TNT transformation products became covalently bound to the plant-derived organic material extractable with water. DCPMAS ¹⁵N ¹³C NMR revealed a three-step reaction scheme. After reduction of TNT, the aryl amines are acetylated. Subsequent alkylation of the resulting amides strengthens the incorporation of TNT-transformation products into humic material. Comparable results have been recently obtained under aerobic conditions, which indicates that this pathway is a common process during biological TNT transformation.     

新型纳米材料光催化反应器研究

为了充分发挥纳米材料的光催化性能,研制了一种带有旋转叶片且可负载光催化纳米材料的光催化反应器.并以制备的纳米TiO2/硅藻土复合材料作为光催化剂、TNT生产废水为处理对象,考察了催化材料附载量、废水浓度和多次重复使用对反应器催化降解效率的影响.结果表明:附载有光催化纳米材料的反应器经过6次6h重复使用,对TNT生产废水催化降解效率仍然保持在75%以上,远高于直接分散在废水中纳米材料的处理效率(47.25%),即多次重复使用并保持高降解效率;而且可较好地避免纳米光催化材料的团聚.避免因回收造成的纳米材料光催化效率降低以及回收不完全造成的水体二次污染等现象.     

电压对使用三维电极处理TNT废水的影响

本试验比较了三维电极电解法和二维电极电解法处理TNT废水的效果,考察了采用三维电极电解法时不同槽电压对电解效果的影响,并对电解机理作了初步探讨.实验表明,极板间距为4 cm、电动搅拌器转速250 r/min、电解时间为2h时,最佳的电解槽电压为15 V,此工艺条件下的COD、TOC的去除率分别为77.6%、62.7%.     

Dendroremediation of trinitrotoluene (TNT) part 1: Literature overview and research concept

BACKGROUND, AIM AND SCOPE: For decades, very large areas of former military sites have been contaminated diffusely with the persistent nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). The recalcitrance of the environmental hazard TNT is to a great extent due to its particulate soil existence, which leads to slow but continuous leaching processes. Although improper handling during the manufacture of TNT seems to be a problem of the past in developed countries, environmental deposition of TNT and other explosives is still going on unfortunately, resulting from thousands of unexploded ordnance or low order explosions at munitions test areas and at current battlefields. OBJECTIVE: Sustainable phytoremediation strategies for explosives in Germany, which intend to use trees to decontaminate soil and groundwater ('dendroremediation'), have to consider that most of the former German military sites are already covered with woodlands, mainly with conifer stands. Therefore, parallel investigation of the remediation potential is necessary for both of the selected hybrids of fast growing broadleaf trees, which are waiting for planting and forest conifers, which have already proven for decades that they are able to grow on explosive contaminated sites. MAIN FEATURES: A short literature review is given regarding phytoremediation of TNT with herbaceous plants and some general aspects of dendroremediation are discussed. Furthermore, an overview of our TNT-dendroremediation research network is introduced, which has the strategic goal to make dendroremediation more calculable for a series of potent trees for site-adapted in situ application and for the assessment of tree remediation potentials in natural attenuation processes. RESULTS AND DISCUSSION: Some of our methods, results and conclusions yet unpublished are presented. For a preliminary calculation of area-related annual TNT dendroremediation potential of five-year-old trees, the following values were assessed: Salix EW-13 6.0, Salix EW-20 8.5, Populus ZP-007 4.2, Betula pendula 5.2, Picea abies 1.9 and Pinus sylvestris 0.8 g m(-2) a(-1). For a 45-year-old spruce forest, an annual natural attenuation potential of 4.2 g TNT m(-2) a(-1) was found. CONCLUSION, RECOMMENDATIONS AND PERSPECTIVE: Our main results deliver quantitative proposals for dendroremediation strategies in situ and provide decision aids. Also aspects of growth of raw materials for energy production are considered. Our dendroremediation research concept for TNT and its congeners can be easily completed for other trees of interest and it can also be applied to herbaceous plants. Knowing the current bottlenecks of phytoremediation and considering the known environmental behaviour of other contaminants, elements of our methodological approach may be easily adapted to those pollutant groups, e.g. for pesticides, pharmaceuticals, PAHs, chlorinated recalcitrants and, with some restrictions, to inorganics and to multiple contaminations. Our dynamical dendrotolerance test systems will help to predict tree growth on polluted areas. To provide some light into the black box of TNT dendroremediation, experimental data regarding the uptake, distribution and degradation of [14C]-TNT in mature tree tissues will be reported in the second part of this publication.     

Biological remediation of explosives and related nitroaromatic compounds

Nitroaromatics form an important group of recalcitrant xenobiotics. Only few aromatic compounds, bearing one nitro group as a substituent of the aromatic ring, are produced as secondary metabolites by microorganisms. The majority of nitroaromatic compounds in the biosphere are industrial chemicals such as explosives, dyes, polyurethane foams, herbicides, insecticides and solvents. These compounds are generally recalcitrant to biological treatment and remain in the biosphere, where they constitute a source of pollution due to both toxic and mutagenic effects on humans, fish, algae and microorganisms. However, relatively few microorganisms have been described as being able to use nitroaromatic compounds as nitrogen and/or carbon and energy source. The best-known nitroaromatic compound is the explosive TNT (2,4,6-trinitrotoluene). This article reviews the bioremediation strategies for TNT-contaminated soil and water. It comes to the following conclusion: The optimal remediation strategy for nitroaromatic compounds depends on many site-specific factors. Composting and the use of reactor systems lend themselves to treating soils contaminated with high levels of explosives (e.g. at former ammunition production facilities, where areas with a high contamination level are common). Compared to composting systems, bioreactors have the major advantage of a short treatment time, but the disadvantage of being more labour intensive and more expensive. Studies indicate that biological treatment systems, which are based on the activity of the fungus Phanerochaete chrysosporium or on Pseudomonas sp. ST53, might be used as effective methods for the remediation of highly contaminated soil and water. Phytoremediation, although not widely used now, has the potential to become an important strategy for the remediation of soil and water contaminated with explosives. It is best suited where contaminant levels are low (e.g. at military sites where pollution is rather diffuse) and where larger contaminated surfaces or volumes have to be treated. In addition, phytoremediation can be used as a polishing method after other remediation treatments, such as composting or bioslurry, have taken place. This in-situ treatment method has the advantage of lower treatment costs, but has the disadvantage of a considerable longer treatment time. In order to improve the cost-efficiency, phytoremediation of nitroaromatics (and other organic xenobiotics) could be combined with bio-energy production. This requires, however, detailed knowledge on the fate of the contaminants in the plants as well as the development of efficient treatment methods for the contaminated biomass that minimise the spreading of the contaminants into the environment during post harvest treatment.     

总磷TNT试剂在地表水环境监测中的应用研究

为有效监控地表水环境中总磷的变化趋势,落实环境保护水污染防治行动计划.选择稳定性好、分析高效、低能耗的总磷TNT试剂对南京市的长江流域水源地、城市内河道及湖泊治理监控区的地表水环境样品进行监测.应用该试剂测定总磷的方法检出限为0.008 mg/L,相对标准偏差为2.2%~7.4%(n=6),加标回收率为91.0%~110%,有证标准样品同步验证测试的相对误差为-1.3%~1.4%.试验证实总磷TNT试剂应用结果能够满足地表水环境中总磷监测的精密度、准确度要求.     

湿式氢气贮柜爆炸伤害效应预测

针对某动力公司工业用氢气贮柜发生的爆炸事故,建立了300 m3湿式氢气贮柜爆炸的模型,给出了事故模型的初始条件,用内能法和TNT当量法对爆炸伤害效应进行了预测.结果表明,对于300 m3湿式氢气贮柜,在混入空气整体达爆炸上限和局部达爆炸上限两种情况下,氢气柜发生一次爆炸的最高爆炸温度分别为1 637 K和1 120 K,最高爆炸超压分别为5.43×105Pa和3.73×105Pa,气柜腾空发生二次爆炸对周围环境的最大人体伤害半径分别为46.8 m和49.7 m,对房屋的最大损伤半径分别为72.5 m和81.6 m.     

新型电极体系电解处理高浓度酸性TNT废水的研究

通过大量试验研究了电解处理TNT废水的条件,尤其是筛选、制备了多种电极材料,在三维电极体系,低电流、短时间条件下电解处理TNT的去除率达到95%以上,pH值提高至6以上,大大节省了能源,为火炸药工业酸性TNT废水的处理提供了一种新型有效的处理方法.用本方法对实际工业"黄水"进行电解处理,获得了较为满意的效果.     

TNT生化降解时间序列的人工神经网络预报模型

利用变步长BP算法,对白腐真菌生化降解实际TNT装药废水过程中TNT含量变化的时间序列建立了人工神经网络预报模型,并利用该模型对生化降解过程的变化规律及趋势进行了研究。结果表明,模型的计算值与实测值之间的误差很小,对未来时刻数据的预测精度也较高,模型较好地反映了TNT含量的变化规律。      

Phytotoxicity to and uptake of TNT by rice

The contamination of the environment by explosives is a worldwide problem resulting in part from 2,4,6-trinitrotoluene (TNT) production. In situ phytoremediation is an appropriate, alternative, cost-effective technology to detoxify extended contamination of surface soil. The ability of rice (Oriza sativa) to both tolerate and assimilate ¹⁴C-labeled TNT was investigated over a 40-day exposure period. The germination rate decreased at 500 mg/kg TNT whereas root and shoot length increased significantly at high TNT concentrations, from 150 to 500 mg/kg. Rice took up TNT residues from soil and accumulated most in roots. Less than 25% of radioactivity taken up was translocated to aerial parts. Above 200 mg/kg TNT, the concentration of TNT residues in roots reached a maximum of approximately 0.7 mg/g. No TNT was found in plant extracts, good evidence for rapid metabolism of TNT. More than 60% of ¹⁴C activity was found as unextractable residues in roots. It was concluded that TNT metabolized and subsequently sequestered by roots could not be translocated to aerial parts.