工艺非球形颗粒在呼吸道内沉积的动力学特性

为探明铸造车间内非球形颗粒在工人呼吸道内沉积的动力学特性,借助电镜扫描获得粉尘颗粒的微观形貌,通过数值模拟方法分析5种形状颗粒在G3～G6及G9～G12呼吸道内运动规律,并讨论颗粒形状、呼吸量、颗粒粒径对其沉积分布的影响.结果表明,颗粒的形状因子φ越大、粒径越大、呼气量越大,非球形颗粒在呼吸道内沉积率η_t越高;φ越小,非球形颗粒在G3～G6呼吸道内沉积分布越分散,在G9～G12呼吸道内则相反;非球形颗粒在G3～G6呼吸道内主要因惯性碰撞发生沉积,φ越小的颗粒受到的曳力作用越强,不同形状颗粒间沉积率差异明显胜于其在G9～G12呼吸道,局部沉积率差异更是超过了30%.因此,形状因子小的非球形颗粒更易被输运至呼吸道较深的位置,对工人的健康威胁可能性更大.     

阵列荷电液滴吸附细颗粒物的数值模拟

静电湿式除尘技术可以改善传统湿式除尘技术对于微细颗粒物吸附效果不佳的状况。通过求解牛顿方程,建立静电力和气动力共同作用下在阵列液滴群吸附下细颗粒物运动的数值模型,通过追踪二维空间中细颗粒物的运动轨迹,描述荷电液滴吸附细颗粒物的动力学演变过程。结果表明:大阵列的液滴群,较小的相邻液滴平均间距能获得更高的吸附效率;相同的气液比下,小粒径的液滴群能获得更高的除尘效率。     

高效纤维滤料过滤纳米颗粒物时的反弹效应

经典过滤理论未考虑纳米颗粒物在纤维表面反弹并降低过滤效率的可能性. 选择不同等级的HEPA(高效空气过滤)玻璃纤维滤料,使用SMPS(扫描电迁移率粒度分析仪)测量粒径在10~500 nm内3种颗粒物——直角立方体MgO、圆角立方体NaCl和球形PSL(聚苯乙烯)固体颗粒的过滤效率,通过比较不同滤料状态下过滤效率的差别分析反弹效应的影响. 结果表明:①硅油熏蒸法制备的湿态滤料可以模拟过滤的理想状态. ②过滤时颗粒物反弹效应大小与其自然运动规律有关,NaCl颗粒的反弹率约为MgO颗粒的66.7%,PSL颗粒的反弹率比非球形颗粒小一个数量级左右. ③颗粒物反弹率也受到滤速的影响,在1.0~5.3 cm/s滤速范围内,反弹率与滤速成正比;滤速在5.3 cm/s时颗粒物的最大反弹率在0.363%~2.667%之间,不同颗粒物的最大反弹率不同,但最大反弹粒径相差不大. ④可以将干态滤料在5.3 cm/s滤速下对MgO颗粒的过滤作为HEPA滤料反弹效应试验的计算基准,根据形状参数(S)和过滤介质透过率的动力学模型对其他滤速和形状的颗粒物反弹率进行修定. ⑤反弹效应对透过率的影响较大,在MPPS(最易透过粒径)附近,非球形颗粒反弹效应对实际透过率的贡献可达30%~40%. 研究表明,HEPA过滤需要考虑颗粒物反弹效应对过滤效率的影响.      

反硝化型甲烷厌氧氧化（DAMO）系统温度耦合模型研究

对Anammox-DAMO系统、Nitrite-DAMO系统、Nitrate-DAMO系统进行基质降解动力学研究,建立了3个DAMO系统温度耦合模型,并对建立的温度耦合模型进行拟合分析.结果表明,二级基质降解动力学能更好地描述Anammox-DAMO系统脱氮动力学行为,半级基质降解动力学能更好地描述Nitrite-DAMO系统和Nitrate-DAMO系统脱氮动力学过程.在15~50 ℃条件下,3个系统脱氮效率均在35 ℃时达到最高,对脱氮动力学的评估表明,3个系统反应动力学均符合Arrhenius方程.根据动力学模拟得出,Anammox-DAMO系统受高温影响更明显,而另外两个 系统则受低温影响更明显.     

改性泥炭-树脂颗粒对水溶液中酸性橙Ⅱ的吸附

通过批量实验研究了改性泥炭-树脂颗粒对水溶液中酸性橙Ⅱ的吸附特性.Langmuir和Freundlich吸附等温方程被用于分析吸附等温数据,准一级动力学模型、准二级动力学模型和颗粒扩散模型被用于吸附动力学实验数据分析.结果表明,改性泥炭-树脂颗粒对水溶液中酸性橙Ⅱ的吸附过程符合Langmuir和Freundlich吸附等温方程,最大吸附量达到71.43 mg·g^-1;颗粒扩散模型能够很好地描述改性泥炭-树脂颗粒对水溶液中酸性橙Ⅱ的吸附动力学过程,水溶液中染料的初始浓度、颗粒直径、颗粒量及搅拌速度对吸附速率均产生一定的影响.改性泥炭-树脂颗粒对水溶液中酸性橙Ⅱ的吸附作用主要发生在颗粒的外表面.     

有机垃圾序批式厌氧消化水解动力学模型研究

在传统一级模型中引入水解有机颗粒表面积,推导并建立了片状颗粒、圆柱形颗粒和球形颗粒有机物水解修正一级模型.片状颗粒模型与传统一级模型的表达式相同.圆柱形颗粒模型和球形颗粒模型的水解速率与未水解颗粒有机物浓度并非服从一级反应动力学,而是分别与未水解颗粒有机物浓度的3/2和5/3次方成正比,且与颗粒有机物的初始浓度有关.通过试验求得有机垃圾的传统一级模型、圆柱形颗粒模型和球形颗粒模型的水解速率常数分别为0.2493、0.5378和0.6741d-1.模型预测结果与残差分析表明,有机垃圾的形状更接近于圆柱形或球形,修正一级模型比传统一级模型能更好地预测有机垃圾的水解过程.     

活化煤矸石对水中亚甲基蓝吸附行为的研究

采用批量吸附实验,研究了活化煤矸石对水中亚甲基蓝的吸附行为。结果表明,活化煤矸石能有效地吸附水中的亚甲基蓝。利用Freundlich等温吸附方程和Langmuir等温吸附方程对其吸附进行描述,表明活化煤矸石易于吸附亚甲基蓝,吸附属于化学吸附,吸附过程是放热反应;用颗粒内扩散方程、准二级吸附动力学方程和准一级吸附动力学方程对实验数据进行回归分析,准二级吸附动力学方程能更好地描述亚甲基蓝在活化煤矸石上的吸附;根据Arrhenius方程得出该吸附的表观活化能为88．14kJ／mol。     

混合钠-钙电解质溶液的物质的量比和胶体粒径对胶体在饱和多孔介质中运移的影响

通过室内砂柱实验,研究了饱和多孔介质中,相同离子强度条件下,混合钠-钙电解质溶液的Ca~(2+)/Na~+物质的量比和胶体粒径对胶体运移的影响.实验结果表明,胶体粒径相同时,随着背景电解质溶液物质的量比的增大,胶体的滞留量增多;物质的量比相同时,相同质量浓度条件下,粒径越小的胶体滞留量越大.经模型拟合,考虑Langmuirian动力学阻塞和与深度有关的沉积行为的对流-弥散-吸附-解吸方程能够很好地描述本次实验条件下胶体在饱和多孔介质中的运移行为.     

福岛事故后放射性气溶胶理化模型的进展

2011年的福岛核事故导致大量放射性气溶胶进入了大气环境,事故等级达到国际核事件分级表的最高级7。为了追踪放射性物质的释放、扩散、沉积和与实际测量进行比较,多种数学模型被用于获取气溶胶的理化特性和动力学行为。文章综述了事故后放射性气溶胶理化模型的研究进展,包括气溶胶源项模型、输运模型、粒子沉积模型、电荷变化模型和人体可吸入颗粒模型等,涉及到气溶胶颗粒的形成、凝并、沉降与再悬浮等理化行为机理。模型的分析结果表明,福岛核事故释放的放射性气溶胶的粒子尺寸、活度、化学组成、电荷变化、滞留时间等理化性质依赖于形成模态而非常善变。     

气象条件对空气质量影响的研究

通过对降雨过程中污染物浓度的研究，得出了颗粒物和非颗粒物在降雨过程中浓度的变化规律；通过对逆温条件下污染物浓度的研究，建立了相关的多元回归方程。     

Derivation and numerical solution of the species mass distribution equations for multicomponent particulate systems

Equations that describe the evolution of the species mass distribution of aparticulate system undergoing growth or evaporation, coagulation, deposition and introduction of new particles are derived. The system of equations is solved using a finite difference-finite element technique. Numerical solutions are obtained for cases for which analytical solutions are available. The results indicate that, for simulating multicomponent particulate system dynamics, the method is highly accurate.     

Impacts of continuously regenerating trap and particle oxidation catalyst on the NO2 and particulate matter emissions emitted from diesel engine

Two continuously regenerating diesel particulate filter (CRDPF) with different configurations and one particles oxidation catalyst (POC) were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO₂, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO₂/NO_x significantly. The results of smoke emissions and particle number (PN) emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter (PM) and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO₂/NO_x. The PN emission results from two CRDPFs indicated that more NO₂ generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO₂ exposure in atmosphere.     

Smog chamber study on the evolution of fume from residential coal combustion

Domestic coal stoves are widely used in countryside and greenbelt residents in China for heating and cooking, and emit considerable pollutants to the atmosphere because of no treatment of their exhaust, which can result in deteriorating local air quality. In this study, a dynamic smog chamber was used to investigate the real-time emissions of gaseous and particulate pollutants during the combustion process and a static smog chamber was used to investigate the fume evolution under simulate light irradiation. The real-time emissions revealed that the total hydrocarbon (THC) and CO increased sharply after ignition, and then quickly decreased, indicating volatilization of hydrocarbons with low molecular weight and incomplete combustion at the beginning stage of combustion made great contribution to these pollutants. There was evident shoulder peak around 10 min combustion for both THC and CO, revealing the emissions from vitrinite combustion. Additionally, another broad emission peak of CO after 30 min was also observed, which was ascribed to the incomplete combustion of the inertinite. Compared with THC and CO, there was only one emission peak for NOx, SO₂ and particular matters at the beginning stage of combustion. The fume evolution with static chamber simulation indicated that evident consumption of SO₂ and NOx as well as new particle formation were observed. The consumption rates for SO₂ and NOx were about 3.44% hr^-1 and 3.68% hr^-1, the new particle formation of nuclei particles grew at a rate of 16.03 nm/hr during the first reaction hour, and the increase of the diameter of accumulation mode particles was evident. The addition of isoprene to the diluted mixture of the fume could promote O₃ and secondary particle formation.     

Multiphase chemistry in a microphysical radiation fog model—A numerical study

A microphysical radiation fog model is coupled with a detailed chemistry module to simulate chemical reactions in the gas phase and in fog water during a radiation fog event. In the chemical part of the model the microphysical particle spectrum is subdivided into three size classes corresponding to non-activated aerosol particles, small and large fog droplets. Chemical reactions in the liquid phase are separately calculated in the small and in the large droplet size class. The impact of the chemical constitution of activated aerosols on fogwater chemistry is considered in the model simulations. The mass transfer of chemical species between the gas phase and the two liquid phases is treated in detail by solving the corresponding coupled differential equation system. The model also accounts for concentration changes of gas-phase and aqueous-phase chemical species which are induced by turbulence, gravitational settling and by evaporation/condensation processes.Numerical results demonstrate that fogwater chemistry is strongly controlled by dynamic processes, i.e. the vertical growth of the fog, turbulent mixing processes and the gravitational settling of the particles. The concentrations of aqueous-phase chemical species are different in the two droplet size classes. Reactands with lower water solubility are mainly found in the large droplet size class because the characteristic time for their mass transfer from the gas phase into the liquid phase is essentially longer than the characteristic time for the formation of large fog droplets. Species with high water solubility are rapidly transferred into the small fog droplets and are then washed out by wet deposition before these particles grow further to form large droplets. Thus, the concentrations of the major ions (NO₃⁻, NH₄⁺) are much higher in small than in large droplets, yielding distinctly lower pH values of the small particles. In the present study the reaction of sulfur with H₂O₂ and the Fe(III)-catalysed autoxidation of S(IV) are the major S(VI) producing mechanisms in fog water. Most of the time the sulfur oxidation rates are higher in the large than in the small droplets. Fogwater deposition by gravitational settling occurs mainly in the large droplet size class. However, since in the small droplets the concentrations of chemical species with very good water solubility are relatively high, in both droplet size classes the total wet deposition of these reactands is of the same order of magnitude.     

多环芳烃在长江口滨岸颗粒物-水相间的分配

利用长江口滨岸水环境中颗粒相与溶解相多环芳烃的实测浓度,获取了多环芳烃化合物在颗粒物-水相间的分配系数K_p.结果表明,分配系数K_p值在507～10 179 L/kg之间,枯季高于洪季,随多环芳烃环数的增加而增大;K_oc值与辛醇-水分配系数K_ow之间存在较好的线性自由能关系（枯季R²＝0.82,洪季R²＝0.68）,推断出长江口滨岸颗粒物亲脂性较差,对多环芳烃的吸收能力相对较弱.长江口滨岸各采样点多环芳烃化合物的lgK_oc值均超过了经典平衡分配模型的预测值上限,多环芳烃两相分配行为不受颗粒物浓度、粒径及上覆水盐度、溶解态有机碳的控制（R²<0.1）,表现出主要受POC及非均一性混合物PSC共同影响的特点;扩展后的含PSC相的颗粒物-水相分配模型较为准确地模拟了lgK_ow<6的多环芳烃化合物野外原位分配过程.     

水中天然有机大分子对混凝影响的电动特征

以流动电流为特征参数，研究了水处理混凝过程中，天然有机大分子对水中悬浮胶体颗粒，无机盐混凝剂及其相互作用过程所表现出的电动性质特征，探讨了ＨＡ和ＤＡ影响混凝过程电动特性的条件与机理。结果表明，ＨＡ和ＤＡ的存在大大降低了无机盐混凝剂对水中悬浮胶粒作用的电动效果，这与二对混凝效果的影响具有一致性。     

Computer simulation of the coagulation of suspended solids — The applicability of the Müller–Smoluchowski theory

The results of studies carried out using a computer programme simulating the coagulation of suspensions containing spherical sol particles and spherical coagulant particles are reported.The influence of the degree of dispersion of the system on the coagulation reaction kinetics was investigated. The obtained results of kinetic studies were tested in the light of classical Müller–Smoluchowski equations. The influence of the physical properties of the coagulant,such as size, density and mass, on the coagulation rate was tested. It was found that within the range described in this paper, the rate of the simulated coagulation process fulfils both the kinetic equation of a first-order reaction, and the kinetic equation of a second-order reaction.Within the tested range, a significant influence of the mass and size of the coagulant on the coagulation rate was ascertained. The kinetic Müller–Smoluchowski dependence is fulfilled in a broader range of the degree of dispersion, when the coagulant particle mass and the sol particle mass are equal. When the particle mass increases with an increase in the particle radius, the coagulation rate increases faster that it would result from the Müller's dependence.     

Characteristics of mass distributions of aerosol particle and its inorganic water-soluble ions in summer over a suburb farmland in Beijing

Agricultural activity is one of the most important sources of aerosol particles. To understand the mass distribution and sources of aerosol particles and their inorganic water-soluble ions in a suburb farmland of Beijing, particle samples were collected using a microorifice uniform deposit impactor (MOUDI) in the summer of 2004 in a suburb vegetable field. The distribution of the particles and their inorganic water-soluble ions in the diameter range of 0.18–18 μm were measured. The dominant fine particle ions were SO₄ ²⁻, NO₃ ⁻, and NH₄ ⁺. The association of day-to-day variation of the concentration of these ions with temperature, humidity, and solar radiation suggested that they are formed by the reaction of NH₃ released from the vegetable field with the acid species produced from photochemical reactions. Fine particle K⁺ is likely from vegetation emission and biomass burning. Coarse particles like Ca²⁺, Mg²⁺, NO₃ ⁻, and SO₄ ²⁻ are suggested to come from the mechanical process by which the soil particle entered the atmosphere, and from the reaction of the acid species at the surface of the soil particle. The results show that fertilizer and soil are important factors determining the aerosol particle over agricultural fields, and vegetable fields in suburban Beijing contribute significantly to the aerosol particle. Translated from Environmental Science, 2006, 27(2): 193–199 [译自: 环境科学]     

On the interaction between equilibration processes and wet or dry deposition

Atmospheric equilibration processes between two phases with different deposition velocities have the potential to affect significantly the amount of total material deposited on the ground. The magnitude of the effects of the equilibration processes depends primarily on the ratio of the deposition velocities of the two phases, on the production/emission rate of the gas phase species, and on the initial distribution of species between the two phases. The deposition of a condensible species equilibrating between gas and aerosol phases can increase by as much as 20 times over that when equilibration processes are not present under appropriate conditions (very large aerosol particles, most of the material initially in the gas phase and high gas-phase production rate) or to decrease by as much as 15 times (very small aerosol particles, most of the material initially in the gas phase and high gas-phase production rate). In fog episodes, the deposition of a gaseous species with a Henry's Law constant between 10³ and 10⁶ M atm⁻¹ (e.g. SO² for pH between 4.5 and 7, H₂O₂, HCHO etc) can be enhanced by as much as a factor of 3 because of its transfer to the aqueous phase. For the NH₃HNO₃NH₄NO₃ system the total deposition can be reduced by as much as a factor of 3 for typical conditions in a polluted atmosphere and small initial concentration of aerosol NH₄NO₃ with NH₃ initially dominating HNO₃ in the gas phase. If an operator splitting scheme is used in a mathematical both equilibration and removal processes should be included in the same operator or very small operator time steps (typically less than 1 min) will be necessary.     

汽车排气尾流中微粒分布及其变化特性的研究

根据微粒核化、凝并及凝结模型对汽车排气尾流中微粒分布的变化特性进行了分析.结果表明,微粒的核化增加了排气尾流中超细微粒的数量;微粒的凝并和凝结将改变排气尾流中的微粒分布.在核化、凝并及凝结过程同时存在时,核化对微粒分布的影响相对较小,微粒分布的变化主要受凝并和凝结的作用.在排气管出口处,微粒的核化、凝并及凝结过程比较剧烈,微粒分布变化较大;随着距排气管出口距离的增加,微粒演变逐渐减弱.研究工作可以为汽车排放控制策略的确定以及汽车微粒对人体健康影响的研究提供依据.