Effect of system variables and particle size on physical characteristics of air sparging plumes     

Daniel M. Baker  Craig H. Benson 《Geotechnical and Geological Engineering》2007,25(5):543-558

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   

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  

李琳  刘菲 《黄金地质》2002,8(2):74-76

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   

钾膨胀石墨层间化合物(K-EGIC_S)的电阻率测量     

孔洪亮  陈代璋  曾荣树 《岩石矿物学杂志》2001,20(2):167-170

在低温惰性条件下合成的钾膨胀石墨层间化合物 (K_EGICS)的电学性能与膨胀石墨的电学性能完全相反 ,随着温度的升高 ,K_EGICS 的电阻率逐渐升高 ,电导率逐渐降低。这一现象是由客体材料钾自身的结构及其与膨胀石墨化合时的键性决定的。  相似文献   

Processing of oxidised nitrogen compounds by passage through winter-time orographic cloud     

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   

Two-dimensional modelling of some CFC replacement compounds     

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   

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  

Pradeep Saxena  Lynn M. Hildemann 《Journal of Atmospheric Chemistry》1996,24(1):57-109

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   

西太平洋区域二甲硫酸及其他硫化物的模拟研究     

李兴生  郑敏  颜鹏 《大气科学》1995,(4)

本文利用一维光化学模式，以二甲硫醚（ＤｉｍｅｔｈｙｌＳｕｌｆｉｄｅ，简称ＤＭＳ）为源模拟了西太平洋对流层的硫化物循环。ＤＭＳ海－气通量由“ｓｔａｇｎａｎｔ－ｆｉｌｍ”模式进行计算。尽管海洋大气中ＯＣＳ浓度比ＤＭＳ大一个量级，但它对ＳＯ２的贡献很小，ＤＭＳ仍是海洋大气中ＳＯ２的主要源。在大气垂直湍流输送过程中，ＤＭＳ白天与ＯＨ反应，夜间与ＮＯ３反应被氧化成ＳＯ２，ＳＯ２大部分通过非均相转化形成Ｈ２ＳＯ４。模拟结果与ＰＥＭ－ＷＥＳＴ－Ａ观测资料对比，取得了较好的一致性。  相似文献   

苯并噻吩系列化合物的成因模拟及其地球化学意义   总被引：4，自引：1，他引：3  

夏燕青  孟仟祥  王红勇  杜丽  王春江 《沉积学报》1999,17(1):127-129

在硫和β胡萝卜素反应产物中有丰富的苯并噻吩系列化合物,在硫与饱和链状化合物反应产物中既有噻吩系列化合物也有苯并噻吩系列化合物。所以推断苯并噻吩系列是硫作用于噻吩系列或含侧链的苯而形成的。噻吩系列和苯并噻吩系列的相对含量可以指示成熟度:在沉积条件相同的前提下,前者多后者少指示成熟度低,反之则指示成熟度高。  相似文献   

我国砷中毒病区的环境特征研究   总被引：18，自引：0，他引：18  

林年丰  汤洁 《地理科学》1999,19(2):135-139

我国饮水型砷中毒的流行屡见报道,台湾嘉南,新疆奎屯,内蒙古河套及山西大同等地是我国几个有代表性的病区。病区多为河湖相和滨海相沉积,粘土,粘土质淤泥和有机淤泥层发育,为富含有要质的还原环境,地下水中的含量一般为０．２－０．６ｍｇ／Ｌ。有时还有氟,腐殖酸,甲基胂酸和某些烷烃类等的有害有机化合物。  相似文献   

The Atmospheric Oxidation of the HS Radical: Reaction with NO2     

Stella M. Resende 《Journal of Atmospheric Chemistry》2007,56(1):21-32

The atmospheric reaction between HS and NO₂ was theoretically investigated at 298 K and 1 atm of pressure. Our results show that the first reaction step will lead to the formation of HSNO₂ or HSONO, spontaneously and exothermically. HSONO easily decomposes into HSO + NO. On the other hand, HSNO₂ can hardly dissociate in the reactants, and its isomerization to other adducts is much hindered. Production of HNO + SO and SNO + OH was found to be unfavorable. Thus, the main products would be HSO + NO and HSNO₂, and new investigations focusing on the atmospheric fate of HSNO₂ are suggested. A general discussion of the fate of HS under atmospheric conditions is presented. Recent investigations indicate that NO₂, O₂ and N₂O should be the most important oxidants of HS, while the O₃ influence will not be significant.  相似文献