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441.
The toxicity characteristic leaching procedure (TCLP) is the current US-EPA standard protocol to evaluate metal leachability
in wastes and contaminated soils. However, application of TCLP to assess lead (Pb) leachability from contaminated shooting
range soils may be questionable. This study determined Pb leachability in the range soils using TCLP and another US-EPA regulatory
leaching method, synthetic precipitation leaching procedure (SPLP). Possible mechanisms that are responsible for Pb leaching
in each leaching protocol were elucidated via X-ray diffraction (XRD). Soil samples were collected from the backstop berms
at four shooting ranges, with Pb concentrations ranging from 5,000 to 60,600 mg kg−1 soil. Lead concentrations in the TCLP leachates were from 3 to 350 mg l−1, with all but one soil exceeding the USEPA non-hazardous waste disposal limit of 5 mg l−1. However, continued dissolution of metallic Pb particles from spent Pb bullets and its re-precipitation as cerussite (PbCO3) prevented the TCLP extraction from reaching equilibrium at the end of the standard leaching period (18 h). Thus, the standard
one-point TCLP test would either over- or under-estimate Pb leachability in shooting range soils. Lead concentration in the
SPLP leachates ranged from 0.021 to 2.6 mg l−1, with all soils above the USEPA regulatory limit of 0.015 mg l−1. In contrast to TCLP, SPLP leaching had reached equilibrium, with regard to both pH and Pb concentrations, within the standard
18 h leaching period, and the analytical SPLP results were in good agreement with those derived from modeling. Thus, we concluded
that SPLP is a more appropriate alternative than TCLP for assessing lead leachability in range soils. 相似文献
442.
水稻新材料耐淹涝能力的比较研究 总被引:4,自引:0,他引:4
以“禾稗”DNA导入后代及受体、供体为试验材料,应用地上部干重和根系干重的相对受害率(RD/%),叶片的电导率(k)和膜脂过氧化物的产物丙二醛(MDA)的增加量几个生长、生理指标,在苗期模拟没顶淹水处理2、4、6d,比较研究了“禾稗”DNA导入后代与供体、受体耐淹涝能力。结果显示:在淹涝胁迫下,“94D-05”、“94D-34”的干重RD/%分别小于它们的受 “科长早3号”和“圭630”,达到或接 相似文献
443.
E. E. Timoshok 《Russian Journal of Ecology》2000,31(1):8-13
The data on the ecology of bilberry and cowberry in the West Siberian Plain, Kuznetsk Ala Tau, and highland Altai are presented.
Ecological ranges of these plants and amplitudes of their tolerance for some environmental factors are described. 相似文献
444.
浆固碎石桩作为一种新型软土地基处理技术,其主要通过注浆改善桩体的加固效果,同时通过浆体渗透来改善桩周土体的物理力学性质,从而减小浆固碎石桩复合地基沉降。针对浆体对桩周土体的渗透作用,按照平面轴对称问题,推导出注浆渗透影响范围的计算方法和浆固区压缩模量计算公式,并通过室内模型试验研究,验证了浆固区压缩模量计算公式的正确性。随后,利用数值计算分析,对浆固区影响范围进行量化分析,并通过数值拟合得到了考虑注浆渗透影响的桩体等效半径计算公式。所得结果对工程设计具有重要的指导意义。 相似文献
445.
Susan Bengtson Nash Stephen R. Rintoul Iain Staniland Megan Tierney 《Environmental pollution (Barking, Essex : 1987)》2010,158(9):2985-2991
In order to investigate the extent to which Perfluorinated Contaminants (PFCs) have permeated the Southern Ocean food web to date, a range of Antarctic, sub-Antarctic and Antarctic-migratory biota were analysed for key ionic PFCs.Based upon the geographical distribution pattern and ecology of biota with detectable vs. non-detectable PFC burdens, an evaluation of the potential contributory roles of alternative system input pathways is made. Our analytical findings, together with previous reports, reveal only the occasional occurrence of PFCs in migratory biota and vertebrate predators with foraging ranges extending into or north of the Antarctic Circumpolar Current (ACC).Geographical contamination patterns observed correspond most strongly with those expected from delivery via hydrospheric transport as governed by the unique oceanographic features of the Southern Ocean. We suggest that hydrospheric transport will form a slow, but primary, input pathway of PFCs to the Antarctic region. 相似文献
446.
YANG Zhong-yi CHEN Fu-hu YUAN Jian-gang ZHENG Zheng-wei WONG Ming-hung 《环境科学学报(英文版)》2004,16(4):670-673
Responses of Sesbania rostrata and S. cannabina to Pb, Zn, Cu and Cd toxicities were assessed by a seed-suspending seedbed(SSS) approach. The results showed that the SSS approach was suitable for testing the tolerance of a plant to the stress of toxic metals. The endpoints include seed germination success, straightened radicle and hypocotyl of the seedlings from the seeds. The measurements could be done easily and accurately. It was found that the elongation of radicle was the most sensitive indicator to the stress of heavy metals among the endpoints. When exposure to lower or medium concentrations of Pb, Zn, and Cd, the development of the lateral roots were favorable. Species of S. rostrata was more tolerant than S. cannabina to the heavy metals, especially to Zn and Cd. The ED50 of Pb, Zn, Cu and Cd were 32.90, .5.32, 4.40 and 12.00 μg/ml for S. rostrata,respectively, and they were 30.11, 2.87, 4.0.5 and 4.94 μg/ml respectively for S. cannabina. 相似文献
447.
We evaluated the toxic-units model developed by Wildhaber and Schmitt (1996) as a predictor of indices of mean tolerance to pollution (i.e., Lenat, 1993; Hilsenhoff, 1987) and other benthic community indices from Great Lakes sediments containing complex mixtures of environmental contaminants (e.g., polychlorinated biphenyls – PCBs, polycyclic aromatic hydrocarbons – PAHs, pesticides, chlorinated dioxins, and metals). Sediment toxic units were defined as the ratio of the estimated pore-water concentration of a contaminant to its chronic toxicity as estimated by U.S. Environmental Protection Agency Ambient Water Quality Criteria (AWQC) or other applicable standard. The total hazard of a sediment to aquatic life was assessed by summing toxic units for all contaminants quantified. Among the benthic community metrics evaluated, total toxic units were most closely correlated with Lenat's (1993) and Hilsenhoff's (1987) indices of community tolerance (T
L
and T
H
, respectively); toxic units accounted for 42% T
L
and 53% T
H
of variability in community tolerance as measured by Ponar grabs. In contrast, taxonomic richness and Shannon-Wiener diversity were not correlated (P > 0.05) with toxic units. Substitution of order- or family-level identifications for lowest possible (mostly genus- or species-) level identifications in the calculation of T
L
and T
H
indices weakened the relationships with toxic units. Tolerance values based on order- and family-level identifications of benthos for artificial substrate samples were more strongly correlated with toxic units than tolerance values for benthos from Ponar grabs. The ability of the toxic-units model to predict the other two components (i.e., laboratory-measured sediment toxicity and benthic community composition) of the Sediment Quality Triad (SQT) may obviate the need for the SQT in some situations. 相似文献
448.
为提升侧面碰撞中后排乘员胸腹部保护效果,在国内某款汽车原有侧面碰撞系统模型基础上,构建后排座椅侧气囊(RSAB)仿真试验模型,通过各项零部件试验与气囊模型对标后导入侧面碰撞系统试验模型;分析RSAB及气帘对后排被试的保护性能,针对胸腹部损伤防护优化侧面气囊相关参数,设计正交试验,运用极差分析法,得出最优参数组合,并对比... 相似文献
449.
Metabolic responses of weeping willows to selenate and selenite 总被引:2,自引:0,他引:2
Goal, Scope and Background Selenium (Se) is one of the most widely distributed elements of the earth’s crust at low concentrations. The extensive use
of Se-containing chemicals due to anthropogenic activities has increased the ecological risk to environmental compartments.
Plants, under unfavorable environmental conditions, often increase the formation of reactive oxygen species (ROS), and consequently
plant antioxidant enzymatic systems have been proposed to be important in plant stress tolerance. The goal of this study was
to find out the metabolic responses of plants to Se, to provide quantitative information whether exogenous Se has a beneficial
role in plants, and to investigate the potential of vegetation management of Se for potential phytoremediation.
Material and Methods Pre-rooted plants of weeping willows (Salix babylonica L.) were grown hydroponically in growth chambers and treated with Na2SeO4 or Na2SeO3 at 24.0 ± 1°C for 168 h. Five different treatment concentrations were used, ranging from 0.44 to 8.72 mg Se/L for the treatments
exposed to SeO42− and from 0.50 to 10.0 mg Se/L for the treatments exposed to SeO32−, respectively. Transpiration rates, soluble protein contents and antioxidative enzyme activities of the plants were monitored
to evaluate toxicity from exogenous Se exposure. At the end of the study, total Se in the hydroponic solution was analyzed
by hydride generation-atomic fluorescence spectrometry (HG-AFS).
Results Both chemical forms of Se at low concentrations showed growth-promoting effects on plants. A significant decrease of transpiration
rates and of soluble protein contents of plants was observed at higher Se concentrations after 168 h of exposure. Measurable
change of superoxide dismutases (SOD) activity in leaves was only detected under high Se treatments. Catalase (CAT) activity
was significantly affected by the Se application. Slight change of peroxidase (POD) activity was measured in all treatments,
whereas significant inhibition of POD activity was detected for the plants exposed to SeO32− of 10.0 mg Se/L. Se-induced stress appeared in all treatments, thus resulting in measurable increase of glutathione peroxidase
(GSH-Px) activity of the plants. Although both chemical forms of Se were taken up by weeping willows efficiently, their uptake
rates were different.
Discussion Of all measured parameters, POD and CAT activities in leaves were noted the most sensitive indicator for the plants exposed
to SeO42− and SeO32−, respectively. Deleterious effects on plant physiological functions due to Se application were not observed over 168 h of
exposure. This is largely due to the fact that well-established antioxidant enzymatic systems in plants and higher activities
of GSH-Px largely reduced the negative effects on plants; SeO32− caused much more severe stress to plants than SeO42− at higher Se application rates. The uptake mechanisms between the two chemical species were quite different.
Conclusions Neither visible toxic symptoms nor metabolic lesions were observed at low concentrations of Se, probably due to the effective
established enzymatic systems in weeping willows. All selected parameters for toxicity determination were significantly correlated
to Se application, but metabolic responses of plants to SeO42− and SeO32− were quite different. GSH-Px in leaves was probably the principle enzyme responsible for stress reduction from Se exposure.
Due to their different chemical properties, weeping willows showed a faster uptake rate for SeO42− than for SeO32−.
Recommendations Exogenous Se has a beneficial role in plants and vegetation management of Se is a potential remediation strategy in cleaning
up Se-contaminated sites. Further investigation on the biochemical mechanism of Se metabolism will provide insight to the
specific interactions between Se and plants on the molecular level.
Perspectives Weeping willow has a sound potential for phytoremediation of Se-contaminated sediment and groundwater because the tree is
not only tolerant to Se but also uptakes chemical species from the environment. 相似文献
450.
Mining activities in Rakha copper mine (Jharkhand, India) were ceased in the year 2001, leaving a huge amount of untreated
tailings in the nearby tailings pond. The copper tailings contained high concentrations of heavy metals (total Cu, Ni concentrations
1779, 564 mgkg−1, respectively), and low contents of major nutrient elements and organic matter. Tailings are often very unstable, and a potential
vegetation cover may reduce the erosion or immobilize the toxicants to surrounding environment by phytostabilization. However,
high shoot concentrations of elements might disperse them and could be harmful to grazing animals. The objective of this study
was to find out which of the three properties; low-accumulation, root accumulation or shoot accumulation of elements (Cu,
Ni, Mn, Zn, Pb, Cd and Co), occur in the semi aquatic species Ammania baccifera growing on copper tailings. Roots of this species accumulated high levels of Cu, even more than 1000 mg kg−1, DW. Metals accumulated by A. baccifera were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them.
Thus, establishment of such plant on copper tailings can be a safe method to stabilize the metals. 相似文献