Toxicity Assessment of Volatile Organic Compounds in Poplar Trees

A method is described to assess the toxicity of selected volatile organic compounds (VOCs) in poplar trees. The method is illustrated for a specific aqueous mixture of VOCs that contaminates the groundwater at a site for which phytoremediation was being considered. The VOC mixture contained a variety of aromatic compounds, chlorinated aliphatics, and alcohols. Poplar tree cuttings planted in 50-gallon barrels in the greenhouse were watered via subirrigation. The subirrigant contained either a low (42 mg/L), medium (85 mg/L), or high (169 mg/L) dose of the VOC mixture, or water only (experimental control). Phytotoxicity was evaluated by measuring the physiological parameters of stomatal conductance, shoot elongation, and biomass production. Two experiments are briefly described: (1) The poplar tree cuttings were allowed to become established in the barrels and then treated to gradually increasing concentrations of the VOC mixture until the final dose was reached. The objective was to establish a detailed dose-response relationship. (2) The poplar tree cuttings were given the low, medium, or high dose of the VOC mixture immediately after planting. The aim of this experiment was to determine if the VOC mixture would be inhibitory to root development. Phytotoxic effects were not observed in either experiment.     

Monitoring the Effect of Poplar Trees on Petroleum-Hydrocarbon and Chlorinated-Solvent Contaminated Ground Water

At contaminated groundwater sites, poplar trees can be used to affect ground-water levels, flow directions, and ultimately total groundwater and contaminant flux to areas downgradient of the trees. The magnitude of the hydrologic changes can be monitored using fundamental concepts of groundwater hydrology, in addition to plant physiology-based approaches, and can be viewed as being almost independent of the contaminant released. The affect of poplar trees on the fate of groundwater contaminants, however, is contaminant dependent. Some petroleum hydrocarbons or chlorinated solvents may be mineralized or transformed to innocuous compounds by rhizospheric bacteria associated with the tree roots, mineralized or transformed by plant tissues in the transpiration stream or leaves after uptake, or passively volatilized and rapidly dispersed or oxidized in the atmosphere. These processes also can be monitored using a combination of physiological- or geochemical-based field or laboratory approaches. When combined, such hydrologic and contaminant monitoring approaches can result in a more accurate assessment of the use of poplar trees to meet regulatory goals at contaminated groundwater sites, verify that these goals continue to be met in the future, and ultimately lead to a consensus on how the performance of plant-based remedial strategies (phytoremediation) is to be assessed.     

Phytoextraction and Accumulation of Boron and Selenium by Poplar (Populus) Hybrid Clones

There has been much interest recently in central California for reusing drainage water to grow trees. A sand-culture study was conducted to investigate the accumulation of boron (B) and selenium (Se) in eight hybrid poplar (Populus) clones irrigated with synthetic agricultural effluent containing increasing levels of chloride salt, B, and Se. Electrical conductivity (EC) ranged from 1.5 to 15 dS m^-1, B levels from 1 to 5 mg L^-1, and Se levels from 100 to 500 μg L^-1. Compared with all tree organs, the leaves accumulated the greatest concentrations of B and Se at the time of harvest. The results show that pooled leaf B concentrations were positively correlated with EC levels (r = 0.78, P < 0.001) and negatively correlated (r = -0.53, P < 0.001) with leaf dry matter for all clones at all tested B levels. Combined leaf and stem Se data show, respectively, a significant decrease (P < 0.05 level) in tissue accumulation of Se with increased salinity. Toxicity symptoms (e.g., burning leaf margins, shoot die back) occurred in most clones grown at 12 and 15 dS m^-1 treatments leading to leaf abscission. Based on the data, clone 49177 (Populus trichocarpa × P. deltoidus) best tolerated the tested parameters among the clones and accumulated the greatest amount of B and Se. The moderate ability of the Populus species to remove and accumulate B and Se from saline effluent is most effective at salinity levels less than 7 dS m^-1.     

Tolerance of Hybrid Poplar (Populus) Trees Irrigated with Varied Levels of Salt,Selenium, and Boron

Agricultural drainage waters and industrial effluents often consist of waste waters laden with salts, boron (B), selenium (Se), molybdenum (Mo), and other contaminants. However, increasing shortages of high-quality water in arid and semiarid regions and increasing demands to maintain the water quality in rivers, lakes, streams, and groundwater have made water reuse an imperative. Trees have been viewed as potential candidates for wastewater reuse because of their capacities for high evapotranspiration, high growth rates, and abilities to accumulate salts and specific ions in a marketable product that is not biologically hazardous. Clones of eight hybrid poplar (Populus spp.) crosses were tested for salt tolerance and ion uptake characteristics in a sand culture study in Riverside, CA. After hardwood cuttings were planted and established under nonsaline conditions, young saplings were treated with artificial waste waters containing different levels of salts, Se, and B. High salt concentrations reduced growth and led to leaf damage and shedding; however, Se and B had no detrimental effect on growth. Salinity affected Se and B accumulation patterns in leaves. A significant degree of genetic variation in salt tolerance was noted among the clones. The salinity at which dry weight was reduced ranged from about 3.3 to about 7.6 dS m^-1 depending on clone, and the relative decrease in dry weight yield with increasing salinity varied among clones and ranged from about 10 to 15% per dS m^-1. This would indicate that poplars, whereas certainly more salt tolerant than avocado trees, are significantly less salt tolerant than eucalyptus. Leaf C1 concentrations increased in relation to the C1 concentrations in the irrigation waters, but also were subject to clonal variation. Salt tolerance in poplar was generally related to C1 in the leaves and stems but was also influenced by growth and vigor characteristics, as well as the allometric relationships between leaves and stems that influenced the sinks in which ions could accumulate before reaching toxic levels.     

Disposition of Atrazine Metabolites Following Uptake and Degradation of Atrazine in Switchgrass

Extensive use of the agricultural herbicide atrazine has led to contamination of numerous ground and surface water bodies. Research has shown that it can have a variety of negative impacts on numerous non-target organisms in the environment. Phytoremediation is one strategy that has been studied to remove atrazine contamination. This paper investigates the hypothesis that switchgrass (Panicum virgatum) can exude metabolites of atrazine after uptake and degradation, which has been suggested by prior research. Pots planted with switchgrass were treated with a 4 ppm solution of atrazine spiked with [¹⁴C]atrazine. After 4 days, switchgrass plants were transplanted to new pots with fresh sand. Four days later, the pots were sacrificed, and sand and plant samples were extracted. Plant and sand samples were analyzed for the presence of atrazine and its major metabolites. The percentage of radiotracer remaining as the parent atrazine was observed to decrease over the course of the study while the percentages of the metabolites were observed to increase. The presence of the metabolite cyanuric acid in a switchgrass phytoremediation system is reported for the first time.     

转双抗虫基因杂种741毛白杨的研究

用部分改造后的苏云金芽孢杆菌 (Bt)杀虫蛋白基因和慈菇蛋白酶抑制剂 (API)基因A构建了植物表达载体。然后通过根癌土壤杆菌 (Agrobacteriumtumefaciens (SmithetTownsend)Conn .)介导将此表达载体上的双抗虫基因转入杂种 741毛白杨 [PopulusalbaL .× (P .davidianaDode P .simoniiCarr.)×P .tomentosaCarr.]获得了一批抗卡那霉素的转化再生植株。用杨扇舟蛾 (Closteraanachoreta (Fabricius) )进行虫试的结果表明有 3株抗虫杨树 ,其中有1株杨树的叶片可使试虫在 6天内的死亡率达 90 %以上 ,而且存活幼虫的生长发育受到了明显的抑制。PCR检测及基因组DNASouthern杂交分析的结果都表明Bt杀虫蛋白基因和API基因已整合到以上 3株抗虫杨树的基因组中 ,而且表现为单拷贝整合。用Bt毒蛋白抗血清进行滤膜免疫反应及ELISA检测结果表明 3株转基因杨树都有Bt杀虫蛋白的表达 ,表达量约占叶总可溶性蛋白的 0 .0 15 %。这是国内外首次报道用双抗虫基因获得的抗虫 741毛白杨植株。     

三倍体白杨杂种无性系指纹图谱的构建

目的:构建三倍体白杨杂种无性系指纹图谱,鉴定三倍体白杨杂种无性系。方法:分离纯化三倍体白杨杂种DNA模板,采用扩增片段长度多态性(AFLP)分子标记技术构建三倍体白杨杂种无性系指纹图谱。结果:从64对引物组合中筛选出M-CTA/E-CAG、M-CAC/E-CCA、M-ACT/E-CTC和M-CTT/E-CTG等4对多态性较高的引物组合,并应用该引物组合对21个三倍体白杨杂种无性系进行了AFLP分析,构建了21个三倍体白杨杂种无性系指纹图谱。结论:构建无性系指纹图谱是鉴别三倍体白杨杂种无性系的有效方法,能够有效鉴别21个三倍体白杨杂种无性系。本研究为品种鉴定及新品种权保护奠定了基础。     

转基因植物对有机污染物的吸收、转化和降解

有机污染物是土壤、水体和大气环境的重要污染物.利用和加强植物修复作用是控制环境污染的有效途径.近年来,一些具有修复功能的外源基因被陆续引入到植物中,使转基因植物的生物修复能力大大增强.文章介绍了植物对污染环境中有机污染物,尤其是持久性有机污染物(POPs)的吸收、转化和降解作用,阐述了转基因植物用于被污染环境修复方面的研究进展和应用前景.     

Performance of Deep-Rooted Phreatophytic Trees at a Site Containing Total Petroleum Hydrocarbons

Poplar and willow tree stands were installed in 2003 at a site in Raleigh, North Carolina containing total petroleum hydrocarbon – contaminated groundwater. The objective was groundwater uptake and plume control. The water table was 5 to 6 m below ground surface (bgs) and therefore methods were used to encourage deep root development. Growth rates, rooting depth and sap flow were measured for trees in Plot A located in the center of the plume and in Plot B peripheral to the plume. The trees were initially sub-irrigated with vertically installed drip-lines and by 2005 had roots 4 to 5 m bgs. Water balance calculations suggested groundwater uptake. In 2007, the average sap flow was higher for Plot B (～59 L per day per tree) than for Plot A (～23 L per day per tree), probably as a result of TPH-induced stress in Plot A. Nevertheless, the estimated rate of groundwater uptake for Plot A was sufficient, relative to the calculated rate of groundwater flux beneath the stand, that a high level of plume control was achieved based on MODFLOW modeling results. Down-gradient groundwater monitoring wells installed in late 2011 should provide quantitative data for plume control.     

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.     

The Distribution of Mineral Elements Following Leaf and Root Uptake

The initial and subsequent distribution of ²²Na, ⁴³K, ⁸⁶Rb, ¹³⁴Cs, ³²P, ³⁵S, ⁴⁵Ca, ⁶⁵Zn and ⁸⁵Sr in bean plants, following leaf and root uptake was studied under controlled environmental conditions. Autoradiographic and counting methods reveal vascular connections between leaves and roots and two patterns of distribution in the leaves following root uptake are reported. Distribution following treatment of specific parts of the leaves or roots points to a morphological unity in the bean plant. A possible circulation pattern for some ions is discussed.     

鞭角华扁叶蜂对自然生境柏木挥发物释放的影响

植物挥发物（Volatile organic compounds;VOCs）在植物抵御害虫侵袭的过程中具有重要作用。本研究以重庆市云阳县长江林场人工林中健康和受害柏木为研究对象,通过VOCs测定分析发现鞭角华扁叶蜂虫害发生之前,两种柏木共计有37种VOCs成分,主要为萜类化合物,其次为醇、酯、醛、烷烃等类化合物;其中健康柏木特有驱赶作用的2-莰醇（龙脑）,受害柏木特有吸引作用的顺式-2-癸烯醛,其余35种为共有成分;各成分浓度在两种柏木中存在较大差异。虫害发生之后,两种柏木共计有32种VOCs成分,而2-莰醇、顺式-2-癸烯醛、薄荷醇、臭樟脑和α-石竹烯等5种成分消失;许多成分的浓度变化趋势与虫害发生前的相反。结果表明健康与受害柏木VOCs释放的差异可能是柏木能否抵御鞭角华扁叶蜂侵害的主要防御机制之一,这将为优良抗虫柏木选育提供理论依据和参考指标。     

环境因子对植物释放挥发性化合物的影响

对近年来有关环境因子与植物释放挥发性化合物关系的研究进展进行了综合和概括。本文主要包括3类挥发性化合物。⑴异戊二烯是由叶绿体产生并且直接释放到大气中的C5化合物。⑵单萜类化合物是一类环状或非环状的C10化合物,它在植物体内合成后首先贮存于体内的特殊结构中（如树脂道、油腺）,然后由此通过气孔向大气中释放。⑶含氧挥发性化合物以各种形式释放大大气中。它包括醇、醛、酮、酯和有机酸。本文的重点是前两者,主要阐述了二方面内容：⑴植物军发性化合物的生物合成和释放机理。⑵环境因子（如温度、光照、水分胁迫、营养、CO2浓度、空气湿度）及植物的发育阶段、机械损伤和昆虫取食等对植物挥发性化合物合成与释放的影响机制。     

光胁迫对杂种杨无性系光合放氧,光化学能量贮藏的影响

以光声光谱技术对经不同光强预处理的 3个杂种杨无性系即三倍体无性系B34 2、二倍体无性系B1 1[(Populusalba×P .glandulosa)× (P .tomentosa×P .bolleana) ]和三倍体无性系B34 6 [(P .tomentosa×P .bolleana)×(P .alba×P .glandulosa) ]的光合放氧、光声热信号及光化学能量贮藏进行测定。叶圆片的光声放氧信号和光化学能量贮藏与预处理光强度成反比 ;而光声热信号与预处理光强度成正比。光化学能量贮藏分配到PSⅡ的份额要比分配到PSⅠ的多。在强光胁迫下PSⅠ的光化学能量贮藏要比PSⅡ的光化学能量贮藏稳定。 3种抑制剂 (strepto mycin ,dithiothreitol,sodiumfluoride)均对叶圆片的光声放氧信号有影响。无性系B1 1和B34 2抵抗光胁迫的能力比无性系B34 6高     

Arbuscular Mycorrhizae Effects on Heavy Metal Uptake by Corn

Maximizing uptake of soil-borne metals into plants is important for successful phytoremediation. Arbuscular mycorrhizae (AM) have been shown previously by our group to sequester metals in the roots of plants and prevent translocation to the shoot. If AM colonization of roots can be reduced, it may be possible to increase metal uptake into plants, thus increasing the efficiency of phytoremediation. The fungicide Benomy® was applied to a Pb-contaminated soil and seeded to corn (Zea mays). Because soil pH affects metal solubility, two pHs were also examined. Colonization of roots by AM was significantly decreased by application of Benomyl to soil, but only at the higher soil pH. Benomyl increased the concentration of several elements, including Pb, in shoots. However, the total Pb content in the shoot decreased due to the reduced shoot weight associated with Benomyl application.

     

Uptake of phosphorus and lead by Brassica juncea and Medicago sativa from chloropyromorphite

In situ remediation of lead (Pb)-contaminated soils via phosphate amendments has been extensively used to immobilize Pb as pyromorphite. However, in phosphorus (P) deficient soils, plants may develop extensive root systems to access P in any P-containing minerals, thereby affecting the stability of Pb5 (PO4)3Cl (Chloropyromorphite; CP). We grew Brassica juncea and Medicago sativa in sand culture to evaluate the stability of CP in the presence or absence of hydroxyapatite (HA) as P source. Treatments (per kilogram of sand) watered with P-nutrient solution were control [PC0, (without CP)], 1, and 5 g Pb as CP [PC1, and PC5] and 0.45 g P as HA (PA), and those of watered with P-free nutrient solution were 1 and 5 g Pb as CP [NC1 and NC5], 5 g Pb as CP plus 0.45 g P as HA [NAC5], and 0.45 g P as HA [NA]. Plants in NC1 and NC5 treatments showed stunted growth and reductions in shoot elongation and leaf size. Among CP treated pots, the highest shoot Pb uptake was observed in NAC5 treatment. The results suggested that Pb accumulation and translocation in the plants was markedly higher in P-sufficient conditions than in P-deficient conditions.     

Groundwater Capture Using Hybrid Poplar Trees: Evaluation of a System in Ogden,Utah

A phytoremediation system was installed in 1996 in Ogden, Utah, with the objective of controlling groundwater containing petroleum hydrocarbons. Hybrid poplar trees were deeply and densely planted in rows oriented perpendicular to the direction of groundwater flow, and the stand was never irrigated. Piezometers were installed to measure water table elevation and contaminant levels upgradient, within, and down-gradient of the trees. In 1998, an analysis of the root structure of a representative tree indicated that roots had extended down to the saturated zone, approximately 6 ft below ground surface. The rate of water use by the stand during 1998 was estimated from reference evapotranspiration (ET_o), leaf area, and a water use multiplication factor ($tH) specific to poplar trees. Sap velocity data were collected to measure actual water use by the stand in late summer of 1998. Estimated and measured values compared favorably, with measured values averaging 2.8 gallons day^-1 tree^-1 (1.7 mm day^-1 tree^-1). Water use by the stand in 1999 averaged an estimated 445 gallons day^-1 (6.9 mm day^-1 for the stand). Although the trees transpired a volume of water equivalent to a 10-ft thickness of the saturated zone, water table elevation data collected in 1999 did not indicate a depression in the water table.     

Mechanism of aerobic transformation of carbon tetrachloride by poplar cells

The biochemical mechanism of carbon tetrachloride transformation by poplarcells was investigated using an axenic poplar cell culture.After one-day incubations of poplar cells under aerobic conditions, about 1.5% of dosedcarbon tetrachloride was transformed to carbon dioxide, about 0.001% to chloroform andabout 3% of the carbon was bound to insoluble poplar cellular materials. The productionof carbon dioxide increased under aerobic conditions while the formation of chloroformand cell binding of carbon tetrachloride-carbon was enhanced under anaerobic conditions.Both carbon dioxide production and cell binding were significantly inhibitedby a general inhibitor of cytochrome P-450 activity (carbon monoxide) and by specific P-450 2E1 inhibitors(chlorzoxazone, isoniazid, 4-methylpyrazole and 1-phenylimidazole). However, no inhibitory effects were observed when the cells were incubated in thepresence of lignin peroxidase inhibitors (NaVO₃ and 3-amino-1,2,4-triazole). These resultssuggest that an enzyme similar to mammalian cytochrome P450-2E1 is involved inthe metabolism of carbon tetrachloride by poplar cells. This study demonstratesan environmental biodegradative process for carbon tetrachloridethat operates under aerobic conditions.     

Uptake and distribution of selenium in different fern species

There has been an interest in using hyperaccumulating plants for the removal of heavy metals and metalloids. High selenium (Se) concentrations in the environment are detrimental to animals, humans, and sustainable agriculture, yet selenium is also an essential nutrient for humans. This experiment was conducted to screen fern plants for their potential to accumulate selenium. Eleven fern species, Pteris vittata, P. quadriaurita, P. dentata, P. ensiformis, P. cretica, Dryopteris erythrosora, Didymochlaena truncatula, Adiantum hispidulum, Actiniopteris radiata, Davallia griffithiana, and Cyrtomium fulcatum, were grown under hydroponic conditions for one week at 20 mg L(-1) selenate or selenite. Root Se concentrations reached 245-731 and 516-1082 mg kg(-1) when treated with selenate and selenite, respectively. The corresponding numbers in the fronds were 153-745 and 74-1,028 mg kg(-1) with no visible toxicity symptoms. Only three fern species were able to accumulate more Se in the fronds than the roots, which were D. griffithiana when treated with selenate, P. vittata when treated with selenite, and A. radiata regardless of the forms of Se. A. radiata was the best species overall for Se accumulation. More research is needed to further determine the potential of the fern species identified in this study for phytoremediation of the Se contaminated soils and water.     

Health Risk Assessment of Workers' Exposure to Organic Compounds in a Tire Factory

This study focuses on a health risk assessment related to chemical exposure via inhalation for workers in a tire factory. Specifically, several volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) were measured in the four different points of the vulcanization unit. A chemical transport model was developed in order to better represent the workers' exposure to the chemicals. Then, a risk assessment methodology was employed to evaluate the potential adverse health effects of the chemicals according to their carcinogenicities. Concentrations measured near the milling machine and press in the vulcanization unit were generally higher than the respective occupational exposure limit values. The corresponding estimated cumulative cancer risks for the carcinogens at the each sampling point were higher than the designated acceptable risk level of 1 × 10^{? 4}. With respect to non-carcinogenic risks, the hazard indexes, both individually and cumulatively, were lower than the specified level of one. The high cancer risk estimated in this study suggests that the VOCs and SVOCs exposure for workers in the vulcanization unit should not be neglected. The results obtained in this study are valuable to plant managers, government officials, and regulators in the risk evaluation process.