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671.
在对多态系统可靠性研究的基础上,将基于矩阵分析的多态系统可靠性分析方法用于区域地质灾害的危险性评价研究,结果表明该方法能较好地定量评价区域地质灾害的危险程度.利用多态系统的可靠性分析方法进行地质灾害危险性区划,不仅可以得出各子区域所处的主要危险区和次主要危险区,而且还可以得出各子区域处于不同地质灾害危险区的可靠度(即可能性大小).该方法基本克服了目前危险性评价方法中评价指标分级和量化以及危险性程度分级的人为性和随意性,具有分级标准统一、评价因素和评价方法相对简单、不受区域条件限制、适用性强等特点. 相似文献
672.
饮用水中微量有机物的污染是关系饮用水生态安全的重要问题。以饮用水中微量的内分泌干扰类除草剂阿特拉津为研究对象,分别采用微生物降解技术和光催化氧化技术对其进行降解,考察温度对阿特拉津降解效果的影响。研究结果表明:阿特拉津浓度为1 mg/L时,3种温度条件下,除锰功能菌MB4对阿特拉津均有明显的去除效果,降解时间为7 d时,阿特拉津的去除率达到65%。底物浓度为200 μg/L,3种温度条件下,活性炭负载二氧化钛(TiO2/PAC)催化剂光降解阿特拉津30 min时,其去除率均达到90%。光催化氧化技术协同微生物降解技术在饮用水中微量的内分泌干扰物的去除中有广阔的应用前景。 相似文献
673.
孔繁德 《中国环境管理干部学院学报》2010,20(3):1-4
曲格平撰写的《生态文明理念和发展方略》重点阐述了生态文明的重要性,深刻揭示了生态文明的必然性,提出了中国生态文明建设的路径和发展方略,启示我们要更加深刻地认识生态文明的重要现实意义和历史必然性,进一步提高贯彻落实科学发展观的自觉性,努力开辟具有中国特色的人与自然和谐发展的道路,开创环保工作的"战略反攻"的新阶段,积极发展环境科技,培养大批高素质环保科技人才。 相似文献
674.
Exposure assessment for trace elements from consumption of marine fish in Southeast Asia 总被引:1,自引:0,他引:1
Agusa T Kunito T Sudaryanto A Monirith I Kan-Atireklap S Iwata H Ismail A Sanguansin J Muchtar M Tana TS Tanabe S 《Environmental pollution (Barking, Essex : 1987)》2007,145(3):766-777
Concentrations of 20 trace elements were determined in muscle and liver of 34 species of marine fish collected from coastal areas of Cambodia, Indonesia, Malaysia and Thailand. Large regional difference was observed in the levels of trace elements in liver of one fish family (Carangidae): the highest mean concentration was observed in fish from the Malaysian coastal waters for V, Cr, Zn, Pb and Bi and those from the Java Sea side of Indonesia for Sn and Hg. To assess the health risk to the Southeast Asian populations from consumption of fish, intake rates of trace elements were estimated. Some marine fish showed Hg levels higher than the guideline values by U.S. Environmental Protection Agency and Joint FAO/WHO Expert Committee on Food Additives (JECFA). This suggests that consumption of these fish may be hazardous to the people. 相似文献
675.
A regression method was developed for the hydrophobicity ruler approach, which is an indirect method for determining the octanol/water partition coefficients of very hydrophobic compounds. Two constants introduced into the mathematical model were obtained by regression of the absorption data sampled before the partition equilibrium. A water miscible organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution so that the hydrophobicity scale was reduced and the equilibration was accelerated. Polydimethylsiloxane/methanol aqueous solution and a series of 21 polychlorinated biphenyls (PCBs) were used to demonstrate the regression method. The PCB compounds with known experimental logK(o/w) values served as reference compounds, while the PCB compounds without known logK(o/w) values were determined. The distribution coefficients (logK(p/s)), uptake and elimination rate constants were obtained from the two regression constants for each compound (reference or unknown). The correlation of the logK(p/s) values of the reference PCB compounds with their logK(o/w) values was linear (logK(o/w)=2.69logK(p/s)+0.76, R(2)=0.97). The logK(o/w) values were compared with literature values and suggested that some values from the literature far off the calibration line could be inaccurate. The critical experimental factors, the merits of the regression method were discussed. 相似文献
676.
Effects of Cd2+ on K+, Ca2+ and N uptake in two halophytes Sesuvium portulacastrum and Mesembryanthemum crystallinum: consequences on growth 总被引:1,自引:0,他引:1
One of the limits of Cd2+-phytoextraction is the high toxicity of this metal to plants. Growth restriction, chlorosis and necrosis are usually accompanied with a large disturbance of the uptake of essential elements. This work aims to study the effects of cadmium (Cd2+) on potassium (K+), calcium (Ca2+) and nitrogen (N) acquisition, and their consequences on growth in two halophytes species: Sesuvium portulacastrum and Mesembryanthemum crystallinum. Seedlings were grown for 30 days in split-root conditions. One half of the root system was immersed in complete nutrient solution (Basal medium (B)) supplemented with 100 microM Cd2+, and the other half was immersed in a Cd2+-free medium, containing all nutrients (B/Cd plants) or deprived of potassium ((B-K)/Cd) or calcium ((B-Ca)/Cd) or nitrogen ((B-N)/Cd). Using this approach, we demonstrated that K+ and Ca2+ uptake was impaired in roots exposed to Cd2+. Concerning N, we noticed no indication of uptake inhibition by Cd2+. However, restriction of K+ uptake by roots was compensated by an increase in the K+-use efficiency, so that growth was not inhibited. Calcium uptake was strongly limited by Cd2. This inhibition was accompanied by a reduction in growth of ((B-Ca)/Cd) plants. Thus, we conclude that Cd2+ limits growth of both halophytes through restriction imposed on Ca2+ uptake. We suggest that the increase of Ca2+ availability in soils could improve the growth of both species in the presence of Cd2+. This would be essential for improving their utility for extraction of this metal by from salty contaminated soils. 相似文献
677.
Kong WD Zhu YG Liang YC Zhang J Smith FA Yang M 《Environmental pollution (Barking, Essex : 1987)》2007,147(1):187-193
A series of experiments were conducted in a hydroponic system to investigate the uptake of oxytetracycline (OTC) and its toxicity to alfalfa (Medicago sativa L.). OTC inhibited alfalfa shoot and root growth by up to 61% and 85%, respectively. The kinetics of OTC uptake could be well described by Michaelis-Menten equation with Vmax of 2.25 micromol g-1 fresh weight h-1, and Km of 0.036 mM. The uptake of OTC by alfalfa was strongly inhibited by the metabolic inhibitor, 2,4-DNP (2,4-dinitrophenol), at pH 3.5 and 6.0, but not by the aquaporin competitors, glycerol and Ag+. OTC uptake, however, was significantly inhibited by Hg2+, suggesting that the inhibition of influx was due to general cellular stress rather than the specific action of Hg2+ on aquaporins. Results from the present study suggested that OTC uptake into alfalfa is an energy-dependent process. 相似文献
678.
Thirteen organochlorine pesticides (OCPs) in 18 fish species from Qiantang River were firstly determined by GC-ECD. To elucidate the sources and the environment fate of these pollutants, water and sediment samples were also analyzed for OCPs contents. Total concentrations of OCPs in fish muscles ranged from 7.43 to 143.79 ng g(-1) wet weight (ww) with highest concentration recorded in sole fish (Cynoglossus abbreviatus), a benthic carnivore. The results indicated that carnivore fish have higher OCPs concentration than other fish with different feeding modes. OCPs concentration in fish was in the range of 1.86-5.85, 2.65-133.51 and 1.94-12.48 ng g(-1) for HCHs (alpha-, beta-, gamma-, delta-HCH), DDTs (p,p'-DDD, p,p'-DDE, p,p'-DDT, o,p'-DDD) and other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), respectively. The highest OCPs concentration in fish organs of four big fish species was found in brain of silver carp (Hypophthalmichthys molitrix), 289.26 ng g(-1) ww followed by kidney, liver, heart and gill. Among the OCPs analyzed, DDE, gamma-HCH and heptachlor were the predominant contaminants in fish muscle, which indicated that there was recent input of lindane. Significant correlation was observed between concentrations of DDTs and lipid content as well as between OCPs and lipid contents in fish species. Both field water bioconcentration factors (BCF) and sediment BCF showed a positive correlation with octanol-water partition coefficients (Kow) in the sole fish. 相似文献
679.
Hu Z Navarro R Nomura N Kong H Wijesekara S Matsumura M 《Environmental science and pollution research international》2007,14(1):12-18
Background There has been an increasing concern about the treatment and disposal of contaminated sediment from dredged river, harbor
or estuary due to the accumulated toxic organics such as dioxins and inorganics particularly heavy metals like Cr, Pb, Zn,
Cu, Hg and Cd. However, considering the huge amount of materials and financial costs involved, any candidate technology must
ultimately result to reusable residual by-products. This can only be made possible if the toxic pollutants are removed or
stabilized in the raw sediment and then fed back into the materials cycle. Currently, we are developing a pyrolysis process
for the commercial-scale cleanup of dioxins and heavy metal-contaminated river sediment to yield reusable char for various
economical applications. In this connection, this paper describes our preliminary investigation into the extent of dioxins
and heavy metal volatilization from actual contaminated sediment. The stabilization of certain metallic species particularly
Cr ions was studied.
Methods Laboratory scale pyrolysis experiments were conducted using a special horizontal lab-scale pyrolyzer. Sediment samples from
Shanghai Suzhou Creek and Tagonoura Harbor were pyrolyzed in the reactor under nitrogen gas at 800°C and different retention
times of 30, 60 and 90 min. A constant heating rate of 10°C min-1 was employed. The pyrolysis gas was first allowed to pass
through a cold trap to condense the tar. Uncondensed gases were then channeled through a column containing an adsorbent (XAD-2
Resin) for dioxins. Heavy metal concentrations in the initial and final sediment residues were analyzed by ICP (Nippon Jarrel-Ash)
following their acid and alkali (for Cr6+) digestion. Dioxins content of the pyrolysis char, tar, and exhaust gases in the
dioxin adsorbent were also determined. For comparative purpose, thermal treatment under air flow was conducted.
Results The data for the removal of heavy metals from Suzhou Creek sediment showed very significant reductions in Pb, Zn and Cr6+
content of the sediment at this condition. Percentage removals were 42.4%, 60.8% and 42.2%, respectively. The disappearance
of Cr6+ was due to reduction reactions rather than volatilization since the total Cr content remained almost unchanged. Other
heavy metals such as Cu, Fe and Ni showed very minimal reductions. Nonetheless, Toxicity Characteristics Leaching Procedure
(TCLP) tests confirmed that these residual heavy metals were rather stable in the pyrolysis char. Reduction of toxic Cr6+
at 42.2% has also been achieved by pyrolysis (with N2) as opposed to the more than 580 % increase in Cr6+ observed during
thermal oxidation (with air).
Discussion Pyrolysis also remove toxic organics particularly dioxins from the sediment. For the total dioxins, removal percentage of
99.9999% was achieved even at the lowest retention time of 30 min. Almost all polychlorinated dibenzo-p-dioxine (PCDDs) and
polychlorinated dibenzo-furans (PCDFs) were removed at any retention time. The TEQs detected from the solid residues were
mainly contributed by dioxin-like PCBs, yet these were present in relatively trace quantities. At the shortest retention time
of 30 min, only 0.000085 pg-TEQ g-1 of polychlorinated biphenyls (PCBs) was detected in the pyrolysis char. Furthermore, the
residual PCBs have very low toxicity ratings and none of the highly toxic PCBs, which were initially present in the sediment
such as 3,3',4,4',5-PeCB and 3,3',4,4'5,5'-HxCB, were detected in the char. Results further confirmed that most of the dioxins
that were removed were transferred to the gas phase so that volatilization may be considered as the main mechanism for their
removal.
Conclusion Some heavy metals particularly Pb and Zn can be volatilized under N2 pyrolysis at 800oC. Pyrolysis also prevented the formation
of more toxic Cr6+ ions and at the same time resulted to its reduction by around 42.2% contrast to the 580% increase during
thermal oxidation. PCDDs and PCDFs have been removed and were not formed in the solid products over the retention time range
of 30-90 min at 800°C. Dioxin-like PCBs mostly remained and a retention time of 30 min was found sufficient for its maximum
removal.
Recommendations and Perspective . With the above results, a temperature of 800oC at a retention time of 30 min is sufficient for the removal of total dioxins
and some heavy metals by volatilization. It is however necessary to destroy the dioxins as well as recover heavy metals in
the gas phase. Stability of remaining heavy metals in the char also needs to be confirmed by leaching tests. These are the
major concerns, which we are currently evaluating to establish the feasibility of our proposed large scale pyrolysis system
for sediment treatment. 相似文献
680.
不同形态铝对小麦抗氧化系统的影响 总被引:14,自引:0,他引:14
研究了铝在不同pH条件下的形态分布,测定了单核铝和多核铝对小麦根中超氧化物歧化酶(SOD)和过氧化物酶(POD)活性的影响.结果表明,低浓度Ala和Alb激发了小麦根SOD活性;POD活性在pH≤5.0时被显著激活,而当 pH≥5,5,Ala与Alb浓度较低时PDD被显著地抑制;SOD与POD活性均在pH4.5,75μmol·l-1[Al]时达到本实验最高值,与Alb浓度的增加相关.本实验结果显示两种形态的铝对植物的致毒机理可能存在一定差异. 相似文献