微波加热对活性炭表面基团及其对SO2吸附性能的影响

采用了微波加热技术,通过在不同微波功率和辐射时间条件下对不同粒径活性炭进行改性,研究了改性前后活性炭的表面化学基团、元素组成的变化,以及对SO2吸附性能的影响.结果表明,经过微波改性后活性炭的SO2吸附性能大为提高,微波功率是影响改性活性炭脱硫性能的主要因素.活性炭经微波热处理后,酸性基团发生分解,表面含氧量减少,碱性特征增强,是吸附性能增加的主要原因之一.     

氧化镁脱硫结垢研究

对氧化镁脱硫法中的结垢问题进行了系统的研究 ,通过对比实验 ,分析了结垢的机理、氧化镁法在防止结垢方面所具有的优势及其原因 ,提出了实际中判断结垢倾向的方法和避免结垢的合理建议。     

污泥膨胀形成机理及控制措施研究现状和进展

污泥膨胀现象在全球污水处理厂普遍存在,已成为制约活性污泥工艺发展的重大难题之一.本文总结了丝状细菌研究现状;重点阐述了当前引起污泥膨胀的主要机理;说明了基于这些机理的选择器控制理论;给出了主要的选择器类型.对当前关于污泥膨胀的研究进展和方向,分别从微生物和数学模型2个方面进行了讨论,最后,提出了一系列亟待解决的问题.     

高气泡表面积通量浮选柱气浮除藻的研究

湖泊、水库等水源的富营养化,使藻类去除成为饮用水生产的重要任务.本研究采用高气泡表面积通量浮选柱气浮除藻,考察了混凝剂、气泡表面积通量和浮选柱高度等因素的影响.试验表明,高气泡表面积通量浮选柱气浮可高效地去除绿藻、硅藻和蓝藻,叶绿素a和藻类去除率达95%以上,比传统浮选柱气浮和沉降作业有较大幅度提高.与普通气浮柱比较,高气泡表面积通量浮选柱增加了气泡与藻的碰撞几率,防止因大表观充气速率造成的紊流和扰动,使气泡/藻结合体有相对静态的浮升环境,避免了气泡/藻结合体在浮升过程中的脱落,实现对藻类的迅速捕集和转移.     

Attempt to adsorb N-nitrosamines in solution by use of zeolites

The strong adsorption of zeolite for N-nitrosamines in solution was first revealed by use of adsorption, and temperature programmed surface reaction (TPSR) techniques. N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) as well as N-nitrosohexamethyleneimine (NHMI) can be adsorbed on zeolite Y, ZSM-5 and A in the solution of methylene chloride or water, which will be helpful for removal of the N-nitrosamines pollution in environmental protection. The equilibrium data were fitted to Freundlich-type isotherms, but the adsorption capacity of zeolites mainly depended on their pore size, surface area and acid-basic properties. Molecular size of adsorbate and solute-solvent interaction also strongly affected the adsorption of N-nitrosamines on zeolite in solution. The extraordinary adsorption properties of NaA zeolite for N-nitrosamines in aqueous solution is first reported and discussed.     

Mineralogical compositions of aquifer matrix as necessary initial conditions in reactive contaminant transport models

Mineralogical compositions and their spatial distributions are important initial conditions for reactive transport modeling. However, popular Kd-based "reactive" transport models only require contaminant concentrations in the pore fluids as initial conditions, and minerals implicitly represent infinite sources and sinks in these models. That situation results in a general neglect of mineralogical characterization in site investigations. This study uses a coupled multi-component reactive mass transport model to predict the natural attenuation of a ground water plume at a uranium mill tailings site in western USA. Numerous ground water geochemistry data are available at this site, but mineralogical data are sketchy. Even given the well-defined pore fluid chemistry, variations of secondary mineral species and mineral abundances in the aquifer resulted in significantly different modeling outcomes. Results show that the amount of calcite in the aquifer determines the distances of plume migration. The possible presence of jurbanite, an aluminum sulfate phase, can store acidity temporarily but cause more severe contamination on a later date. The surfaces of iron oxyhydroxides can store significant amounts of sulfate and protons and serve as a second source for prolonged contamination. These simulations under field conditions illustrate that mineralogical compositions are an essential requirement for accurate prediction of contaminant fate and transport.     

Concentration and size distribution of ultrafine particles near a major highway

Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 microm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7-2.2 ppm, 3.4-10.0 microg/m3, 1.3-2.0 x 10(5)/cm3, and 30.2-64.6 microg/m3, respectively. For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6-220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 x 10(5)/cm3, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.     

Chapter three: methodology of exposure modeling

In this chapter, the concept of exposure assessment and its evolution is introduced, and evaluated by critically appraising the pertinent literature as it applies to exposures to Particulate Matter (PM). Exposure measurement or estimation methodologies and models are reviewed. Three exposure/measurement methodologies are assessed. Estimation methods focus on source evaluation and attribution, sources include those outdoors and indoors as well as in occupational and in-transit environments. Fate and transport models and their inputs are addressed to estimate concentrations outdoors and indoors; source attribution techniques help focus on the contributing sources. Activity pattern techniques are also reviewed and their use in exposure models to estimate inhalation exposure to PM is presented. Deterministic, regression and other stochastic models of exposure to PM are reviewed and evaluated. Strengths, limitations, assumptions and affirmations of the use of exposure assessment as an integral component of risk assessment and risk management are discussed in the conclusions and discussions section of this work.     

Effect of pH on phosphine production and the fate of phosphorus during anaerobic process with granular sludge

The effect of pH on phosphine formation during anaerobic cultivation of granular sludge was investigated. The sludge was taken from full-scale anaerobic reactors treating brewery wastewater. Acetate and phosphate were used as the carbon source and phosphorus source respectively. After 10 days cultivation in the dark, results showed that acidic conditions were more favorable for free phosphine production. At pH 5, the optimum concentration 86.42 ng PH3 m-3 of free phosphine was obtained. The level at pH 7 was reduced to 18.53 ng PH3 m-3, about 1/5 of the maximum. The maximum concentration of matrix-bound phosphine of 3.30 ng PH3 kg-1 wet sludge was achieved at pH 6. More than 83% of the total phosphine was matrix-bound phosphine, which accounted for 0.003-0.009 per thousand of the phosphate removal, while free phosphine comprised 0.00002-0.001 per thousand of the phosphate removal. Most of the phosphorus removal from solution was turned into chemical precipitation or was adsorbed by sludge. The mechanism of the phosphate reduction-step in the formation of phosphine production is still unknown. The promotion of phosphine formation by low pH is compatible with an acidic bio-corrosion mechanism of metal particles in the sludge or of metal phosphides which form phosphine at low pH.     

Nitrous oxide emissions from tundra soil and snowpack in the maritime Antarctic

The nitrous oxide emissions were measured at three tundra sites and one snowpack on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were 1.1 ± 2.2 and 0.6 ± 1.7 μg N₂O m⁻² h⁻¹, respectively. The average flux from tundra soil site with penguin dropping addition was 3.7 ± 2.0 μg N₂O m⁻² h⁻¹, 3–6 times those from the normal tundra soils, suggesting that the deposition of fresh droppings enhanced N₂O emissions during penguin breeding period. The summer precipitation had an important effect on N₂O emissions; the flux decreased when heavy precipitation occurred. The diurnal cycle of the N₂O fluxes from Antarctic tundra soils was not obtained due to local fluky weather conditions. The N₂O fluxes through four snowpack sites were obtained by the vertical N₂O concentration gradient and their average fluxes were 0.94, 1.36, 0.81 and 0.85 μg N₂O m⁻² h⁻¹, respectively. The tundra soils under snowpack emitted N₂O in the maritime Antarctic and increased local atmospheric N₂O concentrations; therefore these fluxes could constitute an important part of the annual N₂O budget for Antarctic tundra ecosystem.