Phytoremediation of Explosives

Referee: Dr. C. Neal Stewart, Jr., Department of Plant Science and Landscape Systems, The University of Tennessee, 2431 Center Drive, Knoxville, TN 37996-4561 There is major international concern over the widescale contamination of soil and associated groundwater by persistant explosives residues. The development of methods to remediate these contaminants has been a significant research interest for several decades. In the last 10 years, phytoremediation has emerged as a focus for explosives remediation because of its low cost, low energy requirements, and promising research observing explosives removal from contaminated groundwater and soil. More recent work has focused on the modes of transformation and metabolism of energetic compounds by plants. These biochemical studies and the experimental conditions enabling the degradation and uptake of explosives by different plant species are discussed.     

Phytoremediation of Mono-, Di-, and Triethylene Glycol by Echinodorus cordifolius L. Griseb

Mono-, di-, and triethylene glycol are chemicals used in various industrial (polyester products, plasticizers, printing, etc.) and domestic settings. The toxicity of these compounds is relatively low, but they do pose risks to the environment. Phytoremediation of the three glycols by Echinodorus cordifolius L. Griseb. were studied. The glycols were degraded in the leaves and roots, but leaves were the main source of degradation. The results of this study indicate that the plant can degrade triethylene glycol to diethylene glycol, diethylene glycol to 1,4-dioxan-2-one, or even further to monoethylene glycol. Moreover, 2-methoxy-4-vinylphenol, 1,2-cyclopentanedione, 1,4:3,6-dianhydro-.alpha.-d-glucopyranose, 2-propenamide, and 2,5-anhydro-1,6-dideoxyhexo-3,4-diulose were produced by this plant in response to the glycols.     

Evidence for biological nature of the grape replant problem in California

A bioassay was developed to investigate causes of grape replant problems under controlled conditions. Soils were collected from methyl bromide-fumigated and non-fumigated plots at a site cleared from a 65-year-old grape vineyard (Vitis vinifera cv. Thompson seedless) at Parlier, CA. Subsamples of the non-fumigated soil were either left non-treated, subjected to autoclaving (twice 45 min), or heating at 40, 50, 60, 70, 80 or 90 °C for 30 min. Subsequently, the samples were placed in 120-mL pots, planted with rooted hardwood grape cuttings (V. vinifera, cv. Carignane) and placed in a greenhouse or growth chamber. Three months after transplanting, vines from non-treated or 40 °C-treated soil had lower shoot weights and densities of healthy lateral roots than vines from the other treatments. Pythium spp. were isolated from 45 to 55% of the plated root segments from vines grown in non-treated, or soil that had been heated at 40 or 50 °C but were not detected in roots from soil given other treatments. Egg masses of root-knot nematode, Meloidogyne spp., were produced on roots from non-treated or heated at 40 °C soil, but no egg masses were detected on roots of the other treatments. In another test with the same soils, remnant roots from non-fumigated or pre-plant methyl bromide-fumigated soil were extracted and amended to non-fumigated soil, soil from fumigated field plots, soil fumigated in a small container, or autoclaved potting mix. The transfer of old vine roots from non-fumigated field soil resulted in incidence of Pythium spp. on grape assay roots, but there was no measurable effect of the transfer on growth and health of the bioassay plant roots. The results of the bioassays indicate that grape replant problem at the California site had biological causes. The bioassay approach may aid in future determinations of the etiology of grape replant problems.     

Accumulation of Trace Metals by Mangrove Plants in Indian Sundarban Wetland: Prospects for Phytoremediation

The work investigates on the potential of ten mangrove species for absorption, accumulation and partitioning of trace metal(loid)s in individual plant tissues (leaves, bark and root/pneumatophore) at two study sites of Indian Sundarban Wetland. The metal(loid) concentration in host sediments and their geochemical characteristics were also considered. Mangrove sediments showed unique potential in many- fold increase for most metal(loid)s than plant tissues due to their inherent physicochemical properties. The ranges of concentration of trace metal(loid)s for As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in plant tissue were 0.006–0.31, 0.02–2.97, 0.10–4.80, 0.13–6.49, 4.46–48.30, 9.2–938.1, 0.02–0.13, 9.8–1726, 11–5.41, 0.04–7.64, 3.81–52.20 μg g ^?1respectively. The bio- concentration factor (BCF) showed its maximum value (15.5) in Excoecaria agallocha for Cd, suggesting that it can be considered as a high-efficient plant for heavy metal bioaccumulation. Among all metals, Cd and Zn were highly bioaccumulated in E. agallocha (2.97 and 52.2 μg g ^?1 respectively. Our findings suggest that the species may be classified as efficient metal trap for Cd in aerial parts, as indicated by higher metal accumulation in the leaves combined with BCF and translocation factor (TF) values.     

植物修复技术及其遗传工程改良

环境的污染在全球变得越来越严重。目前常用的环境污染治理措施不但费用大,效率底,往往还对生态环境本身带来其他的破坏。植物修复技术已在治理环境污染中越来越受到重视。本文综述了植物修复技术的五种应用方式：植物提取、植物降解、植物挥发、植物过滤和植物固定技术对环境污染的修复作用及其机理,并总结了通过遗传工程改良技术来提高植物修复环境污染的能力的研究进展。     

Utilization of Multi-Tasking Non-Edible Plants for Phytoremediation and Bioenergy Source-A Review

Heavy metal contamination of land and freshwater resources is a serious concern worldwide. It adversely affects the health of animals, plants and humans. Therefore, remediation of toxic heavy metals must be highly considered. Unlike other techniques, phytoremediation is a holistic technology and can be used in large scale for soil remediation as it is costless, novel, environmentally-safe and solar-driven technology. Utilization of non-edible plants in phytoremediation is an ingenious technique as they are used to generate new bioenergy resources along with the remediation of contaminated soils. Some nonfood bioenergy crops such as Salix species, Miscanthus species, Populus species, Eucalyptus species, and Ricinus communis exhibit high capability to accumulate various metals and to grow in contaminated lands. However, there are still sustainable challenges facing coupling phytoremediation with bioenergy production from polluted lands. Therefore, there has long been a need for developing different strategies to resolve such challenges. In this article review, we will discuss the phytoremediation mechanism, the technique of phytoremediation coupling with bioenergy production, sustainable problems facing linking phytoremediation with energy production as well as possible strategies to enhance the efficiency of bioenergy plants for soil decontamination by improving their characteristics such as metal uptake, transport, accumulation, and tolerance.     

Phytoremediation Potential of Selected Plants for Nitrate and Phosphorus from Ground Water

The phytoremediation potential of three aquatic plants namely, water lettuce(Pistia stratioes), water hyacinth (Eichhornia crassipes), and water spinach (Ipomoea aquatica) for nitrate N and phosphorus from nutrient treated ground water was assessed. A total of twelve treatment combinations including four levels of nitrate (expressed as nitrate N 0, 20, 40, and 60 mg/l) and three levels of phosphorus (0, 20, and 40 mg/l) were treated for the total volume of 1 and 20 liters of water respectively, for Pistia stratiotes and Eichhornia crassipes. For Ipomoea aquatica ten treatment combinations with five levels of nitrate N (0, 10, 20, 40, and 50 mg/l) and two levels of phosphorus (0 and 5 mg/l) were treated to 3 liters of water. The design used was a two factor factorial with three replicates. Water was analyzed at weekly interval for nitrate N and phosphorus. Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica had the potential to remove nitrate N between 61.5–91.8%, 40–63.5%, and 29.3–75% during the period of six, three and three and weeks, respectively. In addition, 90–99%, 75–97.2%, and 75–83.3% of phosphorus was removed from water by Pistia stratiotes, Eichhornia crassipes and Ipomoea aquatica respectively, during the same period.     

Biosynthesis of halomethanes and methanethiol by higher plants via a novel methyltransferase reaction

Biogenic emissions of halomethanes (CH₃CI, CH₃Br and CH₃I) and methanethiol (CH₃SH) are of major significance to atmospheric chemistry, but there is little information on such emissions from higher plants. We present evidence that plants can produce all these gases through an identical methyltransferase reaction. A survey of 118 herbaceous species, based on CH₃I production by leaf discs supplied with Kl, detected the presence of in vivo halide methyltransferase activity in 87 species. The activities ranged over nearly 4 orders of magnitude. Plants generally considered salt tolerant had relatively low activities, and salinization of three such species did not increase the activity. The highest activities were found in the family Brassicaceae. Leaf extracts of Brassica oleracea catalysed the S-adenosyl-L-methioninc-dependenl niethylalion of the halides I^?, Br^? and CI^? to the respective halomethanes. In addition, the extract similarly methylated HS^? (bisulphide) to CH₃SH. These two types of enzyme activity (halide and bisulphide methyltransferase) were also present in all of the 20 species comprising a subsample that represented the range of CH₃I emissions observed in the initial survey of in vivo CH₃I production ability, and in a marine red alga Endocladia muricata. Moreover, the two activities occurred in approximately the same ratio in all the higher plants tested. These findings highlight the potential of higher plants to contribute to the atmosphericbudget of halomethanes and melhanethiol. The halide and bisulphide methyltransferase activities may also provide a mechanism for the elimination of halide and HS^? ions, both of which are known to be phytotoxic.     

Technical note phytoremediation of triazophos by Canna indica Linn. in a hydroponic system

The phytoremediation of triazophos (O, O-diethyl-O-(1-phenyl-1, 2, 4-triazole-3-base) sulfur phosphate, TAP) by Canna indica Linn. in a hydroponic system was studied. After 21 d of exposure, the removal kinetic constant (K) of TAP was 0.0229-0.0339 d(-1) and the removal percentage of TAP was 41-55% in the plant system and the K and removal percentage of TAP were about 0.002 d(-1) and 1%, respectively, in darkness and disinfected control. However, the K and removal percentage of TAP were 0.006 d(-1) and approximately 11%, respectively, in the treatment with eluate from the media of constructed wetland. The contribution of plant to the remediation of TAP was 74% and C. indica played the most important role in the hydroponic system. Under the stress of TAP and without inorganic phosphorus nutrient, the activity of phosphatase in the plant system increased and phytodegradation was observed. The production and release of phosphatase is seen as the key mechanism for C. indica to degrade TAP. C. indica, which showed the potential of phytoremediation of TAP, and is commonly used in constructed wetland, so the technique of phytoremediation of TAP from contaminated water can be developed with the combination of constructed wetland.     

Treatment of wastewater from Dioscorea zingiberensis tubers used for producing steroid hormones in a microbial fuel cell

A two-chamber microbial fuel cell (MFC) was used to treat Dioscorea zingiberensis processing wastewater and generate electricity. The contaminant degradation process was systematically investigated with the help of UV-Vis, FTIR spectra and GC-MS. The results showed that the COD removal efficiency of the MFC reached 93.5% and the maximum power density achieved 175 mW/m². In the anodic chamber, low molecule weight acid, sugars and cellulose in D. zingiberensis processing wastewater were completely consumed, while complicated contaminants including some furanic and phenolic compounds were decomposed under co-metabolism process. In the cathodic chamber, fatty ester and alkene generated in the anodic chamber were removed, and aromatic compounds were further degraded. Aromatic ester and N-containing compounds were detected as the main residual contaminants by GC-MS. Compared to the effluents of anaerobic digestion and biological aerated filter, fewer and simpler aromatic pollutants existed in the effluents of MFC.     

Potential of Phytoremediation for Treatment of PAHs in Soil at MGP Sites

Phytoremediation is a natural, aesthetically pleasing, low-cost technology that employs plant-influenced microbial, chemical, and physical processes to remediate contaminated soils and waters. The Institute of Gas Technology (IGT) conducted a laboratory study to determine the potential of phytoremediation to remediate soils contaminated with polynuclear aromatic hydrocarbons (PAHs). The soils used for the study were collected from a former manufactured gas plant (MGP) site in Newark, NJ. Phytoremediation was assessed both as a primary remediation technology and as a final polishing step for soil treatment. The following three plant species were used for the 6-month laboratory study: alfalfa (Medicago sativa), switch grass (Panicum virgatum), and little bluestem grass (Schizachyrium scoparium). Using both alfalfa and switch grass for primary treatment of PAH-contaminated soil, a 57% reduction in total PAH concentration was observed after 6-months of treatment. Final polishing of that soil using alfalfa further reduced the total PAH concentration in that soil by 15%. Research is in progress with the objective of improving both the efficiency and the economics of phytoremediation for the cleanup of contaminated soils to environmentally acceptable endpoints at MGP sites.     

柳树对叔丁醇的降解试验

甲基叔丁基醚(MTBE)是目前北美燃料市场最常用的汽油添加剂。由于其化学稳定性强且难于转化,MTBE已成为一种蔓延性的地下水污染物。有氧微生物降解技术被认为是目前对MTBE污染治理最为有效的方法之一,其作用机理是：MTBE在细胞色素酶(CYP-450s)的作用下首先分解成为叔丁醇(TBA),进而完全转化为CO2和H2O。细胞色素酶(CYP-450s)是维管束植物中最为常见的一种酶,我们有理由相信维管束植物细胞能降解MTBE,但试验研究表明超过25种以上的常见植物细胞并不能降解MTBE。TBA是MTBE降解过程中最为稳定的中间产物,植物对其降解的研究目前尚未见报道。本实验用一自行设计的植物反应器来研究柳树(Sallx alba)对TBA降解的可能性。长出新根须和嫩叶的柳树枝条在一容积500ml的植物反应器中生长12d(其中TBA溶液450ml)来观察TBA对柳树生长的影响,同时测定柳树对TBA的吸收和降解。TBA及其它可能的降解产物用气相色谱来检测。本实验结果表明在为期12d的时间内,水溶液中15．26％的TBA可以通过柳树的蒸腾作用去除,但是没有检测到任何可能的降解产物,在植物体内也只发现了少量的TBA残留(＜1％)。同时柳树的根细胞和叶细胞也用来研究对TBA的降解可能性,在为期3d的试验中;柳树的根细胞和叶细胞对TBA的吸收是非常有限的(＜10％),也没有检测到任何可能的降解产物。本研究结果表明柳树同样也不能降解TBA,也许TBA难被降解就是富含CYP-450s酶的维管束植物不能降解MTBE的原因所在。     

臭氧对无土栽培营养液的消毒作用研究

采用稀释平板法和MPN法,测定了臭氧对无土栽培营养液的消毒杀菌作用。结果表明,随着臭氧浓度(时间)的增加,对微生物杀灭率明显上升;连续处理20min,可杀灭90%以上的细菌、真菌和藻类;臭氧间歇曝气消毒营养液,有效控制微生物的滋生,对莴苣根系无不良影响,增加产量36.8%。     

Suppression of Meloidogyne hapla populations by Hirsutella minnesotensis

The effects of the endoparasitic fungus Hirsutella minnesotensis on populations of Meloidogyne hapla from Michigan (MI), Rhode Island (RI), Connecticut (CT), Lyndonville, New York (NYL), Geneva, New York (NYG), and Wisconsin (WI) were studied in the greenhouse. Twenty-day-old tomato (cv. Rutgers) seedlings were inoculated with either 0 or 600 eggs of each nematode population mixed with either 0, 0.02, or 0.1 g of fresh H. minnesotensis mycelium 0.1 L^-1 of soil in pots containing 0.5 L of soil, and maintained at 25±2°C for 2 months. No effect of the fungal treatments and nematode treatments on tomato plant heights and shoot dry weights was observed. While all M. hapla populations were suppressed by H. minnesotensis, the degree to which each population was affected varied slightly. Across fungal treatments and nematode populations, the fungus reduced total number of nematodes in roots by 61-98%, with the highest for NYG and RI, intermediate for NYL and CT, and lowest for MI and WI populations. The study demonstrated that H. minnesotensis may be used as a potential suppressor of M. hapla in vegetable production systems in the Great Lakes Region.     

水稻叶片中过氧化氢与核酮糖-1，5-二磷酸羧化酶/加氧酶降解的关系

甲基紫精(MV)处理水稻植株能快速诱导核酮糖-1,5-二磷酸羧化酶／加氧酶(Rubisco,EC4．1．1．39)及其它可溶性蛋白的降解。MV浓度越高,降解速率越高。MV能诱发叶片内源H     

黄孢原毛皮革菌降解苯胺的工艺研究

通过正交试验优化筛选了适合黄孢原毛皮革菌降解苯胺的适宜培养基和摇瓶培养降解条件。结果表明：其适宜降解的液体培养基组成为：蔗糖20g／L,可溶性淀粉20g／L,(NH4)2SO4l0g／L,Mn^2 lμmol／L,Tween-800．3％,蛋白胨30g／L。适宜降解的摇瓶培养条件为：接种量为20％、pH为7．0、温度为30℃、培养时间为12d．此条件下的苯胺最高降解率可达95．5％。     

Methods for the Analyses of Case-Cohort Studies

Case-cohort and nested case-control sampling methods have recently been introduced as a means of reducing cost in large cohort studies. The asymptotic distribution theory results for relative rate estimation based on Cox type partial or pseudolikelihoods for case-cohort and nested case-control studies have been accounted for. However, many researchers use (stratified) frequency table methods for a first or primary summarization of the most important evidence on exposure-disease or dose-response relationships, i.e. the classical Mantel-Haenszel analyses, trend tests and tests for heterogeneity of relative rates. These can be followed by exponential failure time regression methods on grouped or individual data to model relationships between several factors and response. In this paper we present the adaptations needed to use these methods with case-cohort designs, illustrating their use with data from a recent case-cohort study on the relationship between diet, life-style and cancer. We assume a very general setup allowing piecewise constant failure rates, possible recurrent events per individual, independent censoring and left truncation.     

基因枪法获得GAI转基因橡胶树植株的研究

将含有Camv35S启动子、卡那霉素抗性基因和GUS报告基因,目的基因为GAI基因的转化载体质粒pBI121,通过基因枪轰击巴西橡胶树(Hevea brasiliensis Muell-Arg.)花药愈伤组织,50 mg L~(-1)卡那霉素的继代培养基进行抗性筛选.获得了抗性再生植株,经过PCR、Southern检测结果表明:GAI基因已经成功转入橡胶树基因组中.     

Phytoremediation potentials of cowpea (Vigina unguiculata) and maize (Zea mays) for hydrocarbon degradation in organic and inorganic manure-amended tropical typic paleustults

A field study on phytoremediation of hydrocarbon contaminated soil was designed to assess the effects of organic manures (poultry droppings and cassava peels) and NPK fertilization on the potentials of cowpea (Vigina unguiculata) and maize (Zea mays) to stimulate hydrocarbon degradation in soil. Cowpea and maize crops were established on the hydrocarbon contaminated soil amended with three rates (0, 4, and 8 ton/ha) of the soil amendments, and arranged in 3 x 3 x 3 factorial in Randomized Complete Block Design. Hydrocarbon was significantly (P < 0.05) reduced in plots treated with the combined forms of the soil amendments. While the treatment combinations of 8 t/ha Poultry Droppings (PD) + 8 t/ha Cassava Peels (CP) + 4 t/ha NPK fertilizer was optimal for hydrocarbon degradation in the cowpea plots, 4 t/ha PD + 8 t/ha CP + 8 t/ha NPK fertilizer was the most preferred in the maize plot. Cowpea showed greater potential for hydrocarbon degradation at the first year. The mean values of hydrocarbon concentrations at the cowpea and maize plots indicated no significant difference at the second year. Grain yield of cowpea increased by 87% at the second year, while maize was unable to grow to maturity in the first year.     

Treatment with Methyl Jasmonate Alleviates the Effects of Paraquat on Photosynthesis in Barley Plants

Twelve-day-old barley seedlings were supplied with 23 M methyl jasmonate (MeJA) or 10 M paraquat (Pq) via the transpiration stream and kept in the dark for 24 h. Then they were exposed to 100 mol m^–2 s^–1 PAR and samples were taken 1, 2, 3, and 6 h after irradiation. Treatment of seedlings with MeJA alone resulted in decreased content of chlorophyll (Chl), and net photosynthetic (P _N) and transpiration rates. Pq treatment led to a decrease in Chl content and to a very strong inhibition of P _N, the effects were manifested by 1 h of irradiation. Pq treatment did not affect the activity of ribulose-1,5 bisphosphate carboxylase (RuBPC, EC 4.1.1.39) but increased the activity of the photorespiratory enzymes phosphoglycolate phosphatase (PGP, EC 3.1.3.18), glycolate oxidase (GO, EC 1.1.3.1), and catalase (EC 1.11.1.6). Pre-treatment of seedlings with MeJA before exposure to Pq fully blocked the inhibitory effect of Pq on photosynthesis and protected against subsequent Pq-induced oxidative damage.