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41.
Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air
saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure,
well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60°
were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure
and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow
rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent
with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded
beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection
pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled
off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on
the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence
slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%),
or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging.
However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which
should reduce mass transfer limitations during sparging. 相似文献
42.
大兴安岭摩天岭雨养泥炭沼泽多环芳烃分布特征与来源分析 总被引:3,自引:0,他引:3
运用气相色谱—质谱(GC-MS)技术对大兴安岭摩天岭(47°22′23″N,120°38′45″E)雨养泥炭沼泽泥炭柱中的多环芳烃(PAHs)污染物进行了分析。结果表明,研究区雨养泥炭沼泽表层PAHs总含量的质量比为1 874.4 ng/g,与国内外雨养泥炭沼泽表层相比,其污染水平相对较高。由于研究区气候冷湿,雨养泥炭沼泽中的有机质腐殖化程度较低,有机碳含量较高,这和其PAHs含量的相关性较小。研究区样品中检测出的PAHs主要以2~3环的多环芳烃为主;由PAHs分子标志物指标分析结果可知,研究区雨养泥炭沼泽PAHs污染物的主要来源是当地森林火灾与大气远距离沉降;沉降的PAHs污染物是原油开采、石油生产和化石燃料燃烧的共同贡献。在距地表15~34 cm处,柱状剖面层的PAHs含量显著增加,这是由于1987年和1998年大兴安岭发生森林火灾树木燃烧所致。 相似文献
43.
水资源中氯代烃污染物的去除方法 总被引:3,自引:0,他引:3
随着工业化的发展。氯代有机溶剂使用越来越广泛。并且难于去除。在20世纪90年代初期,人们就已认识到用Fe^0恢复污染的地下水的潜力。国外正在研究帮使用扔几种还原挥发性氯代烃的还原反应介质,尤其要提高的是双金属反应系统,反应速度快,而且脱Cl中国难解产物少,目前国也只停留在实验室研究阶段,个别做了地上反应器的验证实验,它的脱Cl机理、介质钝化和完全脱Cl问题还有待于进一步研究。 相似文献
44.
鼎湖山自然保护区大气气溶胶中的PAHs 总被引:6,自引:2,他引:6
多环芳烃(PAHs)是环境中分布广泛、危害人类健康的有机化合物,通过对鼎湖山自然保护区自然地理和大气气溶胶中苯并(a)芘分析认为,春季样品中大气气溶胶中PAHs主要来源于高等植物排放,夏季来源于珠江三角洲经济区化石燃烧排放。 相似文献
45.
46.
R. N. Colvile T. W. Choularton J. N. Cape B. J. Bandy K. N. Bower R. A. Burgess T. J. Davies G. J. Dollard M. W. Gallagher K. J. Hargreaves B. M. R. Jones S. A. Penkett R. L. Storeton-West 《Journal of Atmospheric Chemistry》1996,24(3):211-239
Four case studies are described, from a three-site field experiment in October/November 1991 using the Great Dun Fell flow-through reactor hill cap cloud in rural Northern England. Measurements of total odd-nitrogen nitrogen oxides (NO
y
) made on either side of the hill, before and after the air flowed through the cloud, showed that 10 to 50% of the NO
y
, called NO
z
, was neither NO nor NO2. This NO
z
failed to exhibit a diurnal variation and was often higher after passage through cloud than before. No evidence of conversion of NO
z
to NO3
- in cloud was found. A simple box model of gas-phase chemistry in air before it reached the cloud, including scavenging of NO3 and N2O5 by aerosol of surface area proportional to the NO2 mixing ratio, shows that NO3 and N2O5 may build up in the boundary layer by night only if stable stratification insulates the air from emissions of NO. This may explain the lack of evidence for N2O5 forming NO3
- in cloud under well-mixed conditions in 1991, in contrast with observations under stably stratified conditions during previous experiments when evidence of N2O5 was found. Inside the cloud, some variations in the calculated total atmospheric loading of HNO2 and the cloud liquid water content were related to each other. Also, indications of conversion of NO
x
to NO
z
were found. To explain these observations, scavenging of NO
x
and HNO2 by cloud droplets and/or aqueous-phase oxidation of NO2
- by nitrate radicals are considered. When cloud acidity was being produced by aqueous-phase oxidation of NO
x
or SO2, NO3
- which had entered the cloud as aerosol particles was liberated as HNO3 vapour. When no aqueous-phase production of acidity was occurring, the reverse, conversion of scavenged HNO3 to particulate NO3
-, was observed. 相似文献
47.
Oliver Wild Oliver V. Rattigan Roderic L. Jones John A. Pyle R. Anthony Cox 《Journal of Atmospheric Chemistry》1996,25(2):167-199
The Cambridge 2-D Eulerian model has been used to study the potential atmospheric distributions and lifetimes of a number of CFC replacement compounds and their degradation products. The study has focused on HFC 134a and HCFCs 123, 141b and 142b and the major products formed by their atmospheric degradation. The loss of these compounds and their products by hydroxyl radical attack, photolysis and in-cloud hydrolysis have been investigated. The study has shown that HCFCs 141b and 142b have sufficiently long lifetimes to enter the stratosphere in significant quantities, where degradation leads to an increase in the total stratospheric chlorine concentration. The study has also highlighted areas where further experimental work would be valuable, in particular characterisation of the product channels for the degradation reactions and determination of the removal rates of the products in the aqueous phase. 相似文献
48.
Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds 总被引:15,自引:0,他引:15
Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecular composition remains poorly characterized. This is largely because atmospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chromatograph; therefore, a substantial portion typically remains unanalyzed. Most often the chemical analysis is performed on a fraction that extracts in organic solvents such as benzene, ether or hexane; consequently, information on the molecular composition of the water-soluble fraction is particularly sparse and incomplete.This paper investigates theoretically the characteristics of the water-soluble fraction by splicing together various strands of information from the literature. We identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics. The results show that water-soluble organics, which constitute a substantial fraction of the total organic mass, include C2 to C7 multifunctional compounds (e.g., diacids, polyols, amino acids). The importance of diacids is already recognized; our results provide an impetus for new experiments to establish the atmospheric concentrations and sources of polyols, amino acids and other oxygenated multifunctional compounds. 相似文献
49.
50.