Leaching of contaminated leaves following uptake and phytoremediation of RDX, HMX, and TNT by poplar

The uptake and fate of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by hybrid poplars in hydroponic systems were compared and exposed leaves were leached with water to simulate potential exposure pathways from groundwater in the field. TNT was removed from solution more quickly than nitramine explosives. Most of radioactivity remained in root tissues for 14C-TNT, but in leaves for 14C-RDX and 14C-HMX. Radiolabel recovery for TNT and HMX was over 94%, but that of RDX decreased over time, suggesting a loss of volatile products. A considerable fraction (45.5%) of radioactivity taken up by whole plants exposed to 14C-HMX was released into deionized water, mostly as parent compound after 5 d of leaching. About a quarter (24.0%) and 1.2% were leached for RDX and TNT, respectively, mostly as transformed products. Leached radioactivity from roots was insignificant in all cases (< 2%). This is the first report in which small amounts of transformation products of RDX leach from dried leaves following uptake by poplars. Such behavior for HMX was reported earlier and is reconfirmed here. All three compounds differ substantially in their fate and transport during the leaching process.     

A Transient Study of Formation of Conjugates during TNT Metabolism by Plant Tissues

The formation of TNT-derived conjugates was investigated in hairy root tissue cultures of Catharanthus roseus and in aquatic plant systems of Myriophyllum aquaticum. The temporal profiles of four TNT-derived conjugates, TNT-1, 2A-1, TNT-2 and 4A-1, were determined over 3 to 16-day exposure durations. When axenic C. roseus roots were exposed separately to 2,4,6 trinitrotoluene, 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene, the array and levels of conjugates varied. Exposure of axenic roots to either 4-amino-2,6-dinitrotoluene or 2-amino-4,6-dinitrotoluene resulted in the formation of only 4A-1 and 2A-1, respectively, and not TNT-1 and TNT-2. However, amendment of previously unexposed roots with TNT produced all four conjugates. The conjugates were preferentially accumulated within the biomass phase of root cultures. Significantly, conjugates TNT-1 and TNT-2 were observed in the biomass phase of intact M. aquaticum plants exposed to TNT. The results clearly indicate the presence of common TNT transformation products in two diverse plants species and tissue type. The distribution of conjugates formed via monoamine derivatives of TNT, however, may be a function of several factors, including the starting xenobiotic type and/or level. Initial bulk rate constants for disappearance of 2,4,6 trinitrotoluene, 2-amino-4,6-dinitrotoluene, and 4-amino-2,6-dinitrotoluene were also determined. Their magnitude followed the order: TNT >> 4-A-2,6-DNT > 2-A-4,6-DNT.     

Phytoremediation of Mercury- and Methylmercury-Polluted Soils Using Genetically Engineered Plants

Inorganic mercury in contaminated soils and sediments is relatively immobile, though biological and chemical processes can transform it to more toxic and bioavailable methylmercury. Methylmercury is neurotoxic to vertebrates and is biomagnified in animal tissues as it is passed from prey to predator. Traditional remediation strategies for mercury contaminated soils are expensive and site-destructive. As an alternative we propose the use of transgenic aquatic, salt marsh, and upland plants to remove available inorganic mercury and methylmercury from contaminated soils and sediments. Plants engineered with a modified bacterial mercuric reductase gene, merA, are capable of converting Hg(II) taken up by roots to the much less toxic Hg(0), which is volatilized from the plant. Plants engineered to express the bacterial organo-mercurial lyase gene, merB, are capable of converting methylmercury taken up by plant roots into sulfhydryl-bound Hg(II). Plants expressing both genes are capable of converting ionic mercury and methylmercury to volatile Hg(0) which is released into an enormous global atmospheric Hg(0) pool. To assess the phytoremediation capability of plants containing the merA gene, a variety of assays were carried out with the model plants Arabidopsis thaliana, and tobacco (Nicotiana tabacum).     

石油污染土壤的生物修复技术

1　前　言在石油生产、贮运、炼制加工及使用过程中 ,由于事故 ,不正常操作及检修等原因 ,都会有石油烃类的溢出和排放。例如 ,油田开发过程中的井喷事故 ;输油管线和贮油罐的泄漏事故 ;油槽车和油轮的泄漏事故 ;油井清蜡和油田地面设备检修 ;炼油和石油化工生产装置检修等。石油烃类大量溢出 ,应当尽可能予以回收 ,但有的情况下回收很困难 ,即使尽力回收 ,仍会残留一部分 ,对环境 (土壤、地面和地下水 )造成污染。其进入土壤后 ,会破坏土壤结构 ,分散土粒 ,使土壤的透水性降低。其富含的反应基能与无机氮、磷结合并限制硝化作用和脱磷酸作…     

Soil Erosion Impact on Agronomic Productivity and Environment Quality

Soil erosion is a global issue because of its severe adverse economic and environmental impacts. Economic impacts on productivity may be due to direct effects on crops/plants on-site and off-site, and environmental consequences are primarily off-site due either to pollution of natural waters or adverse effects on air quality due to dust and emissions of radiatively active gases. Off-site economic effects of erosion are related to the damage to civil structure, siltation of water ways and reservoirs, and additional costs involved in water treatment. There are numerous reports regarding the on-site effects of erosion on productivity. However, a vast majority of these are from the U.S., Canada, Australia, and Europe, and only a few from soils of the tropics and subtropics. On-site effects of erosion on agronomic productivity are assessed with a wide range of methods, which can be broadly grouped into three categories: agronomic/soil quality evaluation, economic assessment, and knowledge surveys. Agronomic methods involve greenhouse and field experiments to assess erosion-induced changes in soil quality in relation to productivity. A widely used technique is to establish field plots on the same soil series but with different severity of past erosion. Different erosional phases must be located on the same landscape position. Impact of past erosion on productivity can also be assessed by relating plant growth to the depth of a root-restrictive horizon. Impact of current erosion rate on productivity can be assessed using field runoff plots or paired watersheds, and that of future erosion using topsoil removal and addition technique. Economic evaluation of the on-site impact involves assessment of the losses of plant available water and nutrients and other additional inputs needed due to erosion. Knowledge surveys are conducted as a qualitative substitute for locations where quantitative data are not available. Results obtained from these different techniques are not comparable, and there is a need to standardize the methods and develop scaling procedures to extrapolate the data from plot or soil level to regional and global scale. There is also a need to assess on-site impact of erosion in relation to soil loss tolerance, soil life, soil resilience or ease of restoration, and soil management options for sustainable use of soil and water resources. Restoration of degraded soils is a high global priority. If about 1.5×10⁹?ha of soils in the world prone to erosion can be managed to effectively control soil erosion, it would improve air and water quality, sequester C in the pedosphere at the rate of about 1.5?Pg/year, and increase food production. The risks of global annual loss of food production due to accelerated erosion may be as high as 190×10⁶?Mg of cereals, 6×10⁶?Mg of soybeans, 3×10⁶?Mg of pulses, and 73×10⁶?Mg of roots and tubers. The actual loss may depend on weather conditions during the growing season, farming systems, soil management, and soil ameliorative input used. Erosion-caused losses of food production are most severe in Asia, Sub-Saharan Africa, and elsewhere in the tropics rather than in other regions.     

植物对土壤中铀的吸收与富集

核工业发展导致重金属铀排放和扩散,并造成了地表土壤的污染,对人类的生存环境产生了极其不利的影响。如何修复铀污染土壤成为亟待解决的问题。近年来发展起来的植物修复技术以其成本低廉、安全和环保的特点成为修复铀污染土壤的新选择。寻找理想的铀富集植物是这一技术的基础和关键。该文通过实验模拟铀污染的土壤（土壤中铀的浓度为100 mg.kg–1）,进行一次和二次铀污染土壤的植物修复后,从4个方面对植物修复铀污染土壤效果进行评估,即富集铀的浓度、生物提取量、生物富集系数（BFS）和转运系数（TFS）。实验结果表明：第1次修复时,四季香油麦菜（Lactuca dolichophylla）地上部富集铀的浓度为1.67×103 mg.kg–1,生物富集系数和转移系数均大于3;第2次修复时,麦冬（Ophiopogon japoni-cus）富集铀的浓度与第1次修复相比变化不大,而吊兰（Chlorophytum comosum）、四季豆（Phaseolus vulgaris）和艾蒿（Artemisia lavandulaefolia）富集铀的浓度与第1次修复相比均减少4–8倍;施加土壤改良剂鸡粪肥、海藻肥和柠檬酸后发现海藻肥和柠檬酸能够增强植物对铀污染土壤的修复;对两次修复土壤中铀的形态进行对比分析,发现二次修复时土壤中生物有效态铀的含量降低,造成第2次修复的难度增加。     

Evaluating Biodegradation as a Primary and Secondary Treatment for Removing RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine) from a Perched Aquifer

Ground water beneath the U.S. Department of Energy (USDOE) Pantex Plant is contaminated with the high explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine). The authors evaluated biodegradation as a remedial option by measuring RDX mineralization in Pantex aquifer microcosms spiked with ¹⁴C-labeled RDX (75 g soil, 15 ml of 5 mg RDX/L). Under anaerobic conditions and constant temperature (16°C), cumulative ¹⁴CO₂ production ranged between 52% and 70% after 49 days, with nutrient-amended (C, N, P) microcosms yielding the greatest mineralization (70%). The authors also evaluated biodegradation as a secondary treatment for removing RDX degradates following oxidation by permanganate (KMnO₄) or reduction by dithionite-reduced aquifer solids (i.e., redox barriers). Under this coupled abiotic/biotic scenario, we found that although unconsumed permanganate initially inhibited biodegradation, > 48% of the initial ¹⁴C-RDX was recovered as ¹⁴CO₂ within 77 days. Following exposure to dithionite-reduced solids, RDX transformation products were also readily mineralized (> 47% in 98 days). When we seeded Pantex aquifer material into Ottawa Sand that had no prior exposure to RDX, mineralization increased 100%, indicating that the Pantex aquifer may have an adapted microbial community that could be exploited for remediation purposes. These results indicate that biodegradation effectively transformed and mineralized RDX in Pantex aquifer microcosms. Additionally, biodegradation may be an excellent secondary treatment for RDX degradates produced from in situ treatment with permanganate or redox barriers.     

有机物及重金属植物修复研究进展

植物修复技术是近年来发展起来的一种非常有前途的生物治理技术 ,也是当前学术界研究的热点领域 .本文对植物修复的类型 ,植物修复土壤、水体有机污染物、重金属和某些放射性核素的过程、机理及可能影响因子作了概括和详尽讨论 ,并就国内外近年来植物修复技术在污染环境中的应用和研究成果进行了综述     

Water-Saving and High-Yielding Irrigation for Lowland Rice by Controlling Limiting Values of Soil Water Potential

The present study investigated whether an irrigation system could be established to save water and increase grain yield to enhance water productivity by proper water management at the field level in irrigated lowland rice （Oryza sativa L.）. Using two field-grown rice cultivars, two irrigation systems; conventional irrigation and water-saving irrigation, were conducted. In the water-saving irrigation system, limiting values of soil water potential related to specific growth stages were proposed as irrigation indices. Compared with conventional irrigation where drainage was in mid-season and flooded at other times, the water-saving irrigation increased grain yield by 7.4% to 11.3%, reduced irrigation water by 24.5% to 29.2%, and increased water productivity （grain yield per cubic meter of irrigation water） by 43.1% to 50.3%. The water-saving irrigation significantly increased harvest index, improved milling and appearance qualities, elevated zeatin-I-zeaUn riboside concentrations in root bleedings and enhanced activities of sucrose synthase, adenosine diphosphate glucose pyrophosphorylase, starch synthase and starch branching enzyme in grains. Our results indicate that water-saving irrigation by controlling limiting values of soil water potential related to specific growth stages can enhance physiological activities of roots and grains, reduce water input, and increase grain yield.     

石油污染土壤的生物修复与土壤酶活性关系

研究了不同油浓度污染土壤经过两个为期125d的生物修复后的土壤中过氧化氢酶、多酚氧化酶和脂肪酶的酶活变化,分析了土壤中3种酶活性的变化特征与规律。结果表明,随着油浓度的增加,土壤中过氧化氢酶和多酚氧化酶的活性下降,脂肪酶活性增加;经过生物修复后,土壤中的过氧化氢酶和多酚氧化酶的活性在第二周期要比第一周期提高,而脂肪酶活性下降;这3种土壤酶活性变化受污染物浓度影响不显著,但不同浓度油污染土壤的修复对过氧化氢酶的影响要大于对多酚氧化酶和脂肪酶的影响。     

重金属污染土壤植物修复基本原理及强化措施探讨

阐述了植物修复的基本概念及主要作用方式 ,并从土壤中重金属存在形态 ,植物对重金属吸收、排泄和积累以及植物生物学特性与植物修复的关系等方面讨论了重金属污染土壤植物修复的基本原理及局限性和限制性因素 ,从超富集植物性能强化和技术强化两方面探讨了植物修复的强化措施 ,并指出与现代化农业技术相结合是植物修复重金属污染土壤大规模商业应用的一条捷径     

Uptake and Translocation of Benthiocarb Herbicide by Plants

The uptake and translocation of ¹⁴C-benthiocarb labelled at benzyl methylene by rice plant, bamyardgrass, wild amaranth, smart weed and lambsquarters were investigated, ¹⁴C-Benthiocarb was absorbed through the roots and the radioactivity was translocated into whole plants. The rate of absorption and translocation varied by the kind of plants. The translocation was occurred not only from roots into leaves, but from a leaf into other leaves, and even into roots of some kinds of plant. The absorption and translocation was more easy in barnyard-grass than in rice plant. Benthiocarb was rapidly absorbed by seeds and accumulated mostly in the embryo. The uptake of benthiocarb by seedlings decreased with the order of mesocotyl (bamyardgrass only), coleoptyl, root and leaf. Benthiocarb was degraded rapidly in plants.     

A Peat Moss-Based Technology for Mitigating Residues of the Explosives TNT,RDX, and HMX in Soil

There is increased interest in how to balance military preparedness and environmental protection at Department of Defense (DoD) facilities. This research evaluated a peat moss-based technology to enhance the adsorption and biodegradation of explosive residues at military testing and training ranges. The evaluation was performed using 30-cm-long soil columns operated under unsaturated flow conditions. The treatment materials were placed at the soil surface, and soil contaminated with 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was spread over the surface. Simulated rainfall initiated dissolution and leaching of the explosive compounds, which was monitored at several depths within the columns. Peat moss plus soybean oil reduced the soluble concentrations of TNT, RDX and HMX detected at 10 cm depth by 100%, 60%, and 40%, respectively, compared to the no-treatment control column. Peat moss alone reduced TNT and HMX concentrations at 10 cm depth relative to the control, but exhibited higher soluble RDX concentrations by the end of the experiment. Concentrations of HMX and RDX were also reduced at 30 cm depth by the peat moss plus soybean oil treatments relative to those observed in the control column. These preliminary results demonstrate proof-of-concept of a low cost technology for reducing the contamination of groundwater with explosives at military test and training ranges.     

我国污染土壤修复研究现状与展望

介绍了我国土壤污染的突出特点及其危害,回顾了污染土壤从清洁技术研究到物理、化学和生物修复研究的历程,总结了污染土壤修复取得的初步成果,提出了污染土壤修复的实质和系统技术方法。根据我国土壤污染的实际和修复需求,本文提出了当前本领域急需开展的研究内容,预测了污染土壤修复研究对环境科学相关学科的推动作用。     

Micronutrient Cation Sorption by Roots and Uptake by Plants

The sorption of ferric iron, copper, zinc and manganese by wheatseedling roots and by discs of cellulose filter paper was measured.The magnitude of sorption at pH 5-0 was Fe(III) > Cu(II)> Zn(II) > Mn(II). Sorption of Cu(II), Zn(II) and Mn(II)increased with increasing pH whilst sorption of Fe(III) decreased.The patterns of sorption are discussed in the light of our knowledgeof the hydrolysis of the metal ions. It is suggested that metalsadsorbed on root surfaces may be remobilized by organic ligandswhich leak from the root cells. Where an external liquid diffusionpath away from the root does not exist, soluble metal ligandcomplexes might accumulate in the water free space and superficialwater film of the root, thus facilitating their uptake intoroot cells and translocation within the plant. Under such conditionsthe amounts of metal translocated to the shoots of wheat seedlingsare shown to be related to the amounts of metal adsorbed bytheir roots. Key words: Adsorption, Micronutrients, Roots     

不同土层测墒补灌对冬小麦耗水特性与光合速率和产量的影响

于2012—2014年两个冬小麦生长季,在大田条件下设置：全生育期不灌水(W₀)处理,当地定量节水灌溉(拔节期和开花期均灌水60 mm,W₁)处理,依据0～20 cm (W₂)、0～40 cm (W₃)、0～60 cm (W₄)和0～140 cm (W₅)土层土壤含水量测墒补灌处理,于拔节期和开花期补灌至土壤相对含水量为田间持水量的65%和70%,研究依据不同土层土壤含水量测墒补灌对冬小麦耗水特性、光合速率和籽粒产量的影响.结果表明：各处理拔节期灌水量为W₁、W₄＞W₃＞W₂、W₅,开花期灌水量和总灌水量均为W₅＞W₁、W₄＞W₃＞W₂,W₃总耗水量显著高于W₂处理,与W₁、W₄和W₅处理无显著差异.W₃土壤贮水消耗量高于W₁、W₄和W₅处理,其中,W₃在拔节至开花阶段和开花至成熟阶段对40～140 cm和60～140 cm土层土壤贮水消耗量均显著高于其余灌水处理.灌浆中期W₃处理小麦旗叶光合速率、蒸腾速率和水分利用效率最高,W₁和W₄处理次之,W₀处理最低.W₃处理两个生长季的籽粒产量分别为9077和9260 kg·hm^-2,水分利用效率分别为20.7和20.9 kg·hm-2·mm^-1,均显著高于其余处理,灌溉水生产效率最高.综合考虑灌水量、籽粒产量和水分利用效率,小麦拔节期和开花期适宜进行测墒补灌的土层深度为0～40 cm.     

利用能源植物治理土壤重金属污染

随着工农业的发展,土壤重金属污染日益加剧,严重威胁着粮食生产和人类健康。植物修复因其成本低、环境友好以及可大规模原位修复等优点备受关注,成为近年来迅速发展的重金属污染土壤治理技术。在介绍国内外植物修复技术发展与应用现状的基础上,提倡大力发展能源植物修复重金属污染土地,并结合湖南重金属污染田间试验结果,重点对甜高粱(Sorghum bicolor(Linn.)Moench)用于重金属污染土壤修复的优势、可行性及提高修复效率的措施进行了深入分析与探讨。利用甜高粱治理土壤重金属污染,能将土壤修复与生物能源生产有机结合,使重金属从粮食链转入能源链,同时兼顾了生态和经济效益,具有广阔的应用前景。