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41.
采用气袋直接进样法测定环境和污染源空气中的丙烯腈。结果表明:丙烯腈在0.4~99.5 mg/m3浓度范围内具有良好的线性关系,相关系数为0.999 8。在低、中、高3个添加水平回收率为88.9%~100%,相对标准偏差为0.6%~4.7%,均能较好地满足实验室分析要求。 相似文献
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本文将低浓度瓦斯与脉动燃烧结合,主要研究了脉动频率对低浓度瓦斯燃烧的影响。实验结果发现:频率为99Hz至120Hz之间的脉动燃烧不仅可以降低贫燃极限.实现瓦斯在5%浓度下稳定而充分的燃烧,而且在相同温度下提高了瓦斯燃烧效率,污染物的排放也得到了改善。 相似文献
45.
Jun Bai Xiuhong Yang Ruiying Du Yanmei Chen Shizhong Wang Rongliang Qiu 《环境科学学报(英文版)》2014,26(10):2056-2064
Mechanisms of soil Pb immobilization by Bacillus subtilis DBM, a bacterial strain isolated from a heavy-metal-contaminated soil, were investigated. Adsorption and desorption experiments with living bacterial cells as well as dead cells revealed that both extracellular adsorption and intracellular accumulation were involved in the Pb2+removal from the liquid phase. Of the sequestered Pb(II), 8.5% was held by physical entrapment within the cell wall, 43.3% was held by ion-exchange, 9.7% was complexed with cell surface functional groups or precipitated on the cell surface, and 38.5% was intracellularly accumulated.Complexation of Pb2+with carboxyl, hydroxyl, carbonyl, amido, and phosphate groups was demonstrated by Fourier transform infrared spectroscopic analysis. Precipitates of Pb5(PO4)3OH, Pb5(PO4)3Cl and Pb10(PO4)6(OH)2that formed on the cell surface during the biosorption process were identified by X-ray diffraction analysis. Transmission electron microscopy–energy dispersive spectroscopic analysis confirmed the presence of the Pb(II)precipitates and that Pb(II) could be sequestered both extracellularly and intracellularly.Incubation with B. subtilis DBM significantly decreased the amount of the weak-acid-soluble Pb fraction in a heavy-metal-contaminated soil, resulting in a reduction in Pb bioavailability, but increased the amount of its organic-matter-bound fraction by 71%. The ability of B.subtilis DBM to reduce the bioavailability of soil Pb makes it potentially useful for bacteria-assisted phytostabilization of multi-heavy-metal-contaminated soil. 相似文献
46.
分析2013年大气降水pH值及近10年历史演变的方法分析丹东市酸雨污染现状、特征,并从污染源和气候条件解释酸雨形成的原因,确定酸雨的形成受外来空气污染物影响较大,而酸雨强度的大小具有本地环境条件和环境污染特征。 相似文献
47.
Seasonal and particle size-dependent variations in gas/particle partitioning of PCDD/Fs 总被引:1,自引:0,他引:1
Lee SJ Ale D Chang YS Oh JE Shin SK 《Environmental pollution (Barking, Essex : 1987)》2008,153(1):215-222
This study monitored particle size-dependent variations in atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Two gas/particle partitioning models, the subcooled liquid vapor pressure (P(L)(0)) and the octanol-air partition coefficient (K(OA)) model, were applied to each particle sizes. The regression coefficients of each fraction against the gas/particle partition coefficient (K(P)) were similar for separated particles within the same sample set but differed for particles collected during different periods. Gas/particle partitioning calculated from the integral of fractions was similar to that of size-segregated particles and previously measured bulk values. Despite the different behaviors and production mechanisms of atmospheric particles of different sizes, PCDD/F partitioning of each size range was controlled by meteorological conditions such as atmospheric temperature, O(3) and UV, which reflects no source related with certain particle size ranges but mixed urban sources within this city. Our observations emphasize that when assessing environmental and health effects, the movement of PCDD/Fs in air should be considered in conjunction with particle size in addition to the bulk aerosol. 相似文献
48.
Kopittke PM Asher CJ Menzies NW 《Environmental pollution (Barking, Essex : 1987)》2008,153(3):548-554
Despite the presence of numerous studies in the literature examining the phytotoxicity of Pb, there is a lack of precise quantitative data on limiting concentrations of Pb for plant growth. Using the PhreeqcI chemical equilibrium model, simulations were conducted to examine the speciation of Pb in concentrated and dilute nutrient solutions. Due to the higher P concentration of Hoagland's solution (1000microM), precipitation of chloropyromorphite (Pb5(PO4)3Cl) was predicted to occur at lower pH values, and at lower Pb concentrations, than for a dilute nutrient solution (2microM P). Although nutrient solutions prepared in the glasshouse were supersaturated (and Pb concentrations were substantially higher than predicted by modeling), they confirmed the importance of the P concentration in influencing the precipitation of Pb. Given the low solubility of Pb-phosphates, nutrient solutions with low P concentrations should be utilized, and plant growth should be related to measured Pb concentrations rather than to the quantity of Pb initially added. 相似文献
49.
Paoletti E Contran N Manning WJ Castagna A Ranieri A Tagliaferro F 《Environmental pollution (Barking, Essex : 1987)》2008,155(3):464-472
Treatments with ethylenediurea (EDU) protect plants from ozone foliar injury, but the processes underlying this protection are poorly understood. Adult ash trees (Fraxinus excelsior), with or without foliar ozone symptoms in previous years, were treated with EDU at 450ppm by gravitational trunk infusion in May-September 2005 (32.5ppmh AOT40). At 30-day intervals, shoot growth, gas exchange, chlorophyll a fluorescence, and water potential were determined. In September, several biochemical parameters were measured. The protective influence of EDU was supported by enhancement in the number of leaflets. EDU did not contribute its nitrogen to leaf tissue as a fertiliser, as determined from lack of difference in foliar N between treatments. Both biochemical (increase in ascorbate-peroxidase and ascorbic acid, and decrease in apoplastic hydrogen peroxide) and biophysical (decrease in stomatal conductance) processes regulated EDU action. As total ascorbic acid increased only in the asymptomatic trees, its role in alleviating O(3) effects on leaf growth and visible injury is controversial. 相似文献
50.
Wetherbee GA Gay DA Brunette RC Sweet CW 《Environmental monitoring and assessment》2007,131(1-3):49-69
The National Atmospheric Deposition Program/Mercury Deposition Network (MDN) provides long-term, quality-assured records of
mercury in wet deposition in the USA and Canada. Interpretation of spatial and temporal trends in the MDN data requires quantification
of the variability of the MDN measurements. Variability is quantified for MDN data from collocated samplers at MDN sites in
two states, one in Illinois and one in Washington. Median absolute differences in the collocated sampler data for total mercury
concentration are approximately 11% of the median mercury concentration for all valid 1999–2004 MDN data. Median absolute
differences are between 3.0% and 14% of the median MDN value for collector catch (sample volume) and between 6.0% and 15%
of the median MDN value for mercury wet deposition. The overall measurement errors are sufficiently low to resolve between
NADP/MDN measurements by ±2 ng·l−1 and ±2 μg·m−2·year−1, which are the contour intervals used to display the data on NADP isopleths maps for concentration and deposition, respectively. 相似文献