Heterogeneous transformation of peroxyacetylnitrate

The heterogeneous decomposition of peroxyacetylnitrate (PAN) has been investigated using a flow reactor and infrared spectroscopic analysis. The decomposition rate in air due to glass surfaces follows the relation d[PAN]/dt = −S/V([PAN] × 7 × 10⁷ + [CH₃C(O)OO] × 5 × 90¹²)exp(−9382/T) molecules cm⁻³ s⁻¹ (S/V=surface to volume ratio). The rate observed for NH₄HSO₄-covered surfaces is lower than in the glass case. The rate is high enough to affect many laboratory experiments but too slow to have any influence on PAN decomposition under ambient conditions.     

高分辨率气溶胶光学厚度在珠三角及香港地区区域颗粒物监测中的应用研究

利用最新的MODlS(中分辨率成像光谱仪)气溶胶光学厚度(AOD)反演算法,反演珠江三角洲及香港地区2008年高分辨率(1 km x1 km)AOD分布,并与AERONET观测数据进行了验证(r=0.917).分析了2008年珠江三角洲及香港地区5个站点地面监测PM10质量浓度与反演的AOD数据相关性.结果表明:两者直...     

Aqueous S(IV) oxidation—I. Catalytic effects of some metal ions

Catalytic effect of metal ions [Fe(III), Mn(II), Cu(II), Pb(II) and Zn(II)] on the oxidation of S(IV) in aqueous solution at concentrations of metal ions and S(IV) as found in an urban atmosphere were studied under controlled experimental conditions (T, pH air flow rate, mixing, concentration of reactant, etc.). The following rate expressions were obtained: −r_S(IV) = k [Fe(III)] [S(IV)], −r_S(IV) = k [Mn(II)] [S(IV)]^0.65, −r_S(IV) = k [Cu(II)] [S(IV)]². The activation energy equals 104 kJ mol⁻¹ for Fe(III), 63.3 kJ mol⁻¹ for Mn(II), and 116.8 kJ mol⁻¹ for Cu(II) catalysed S(IV) oxidation.     

冷空气过程对江苏持续性霾的影响研究

利用地面气象观测资料、PM_(2.5)浓度监测资料和数值模式产品对2016年12月14—24日江苏遭遇的一次长时间霾天气过程进行分析.研究结果表明:过程期间有两次冷空气南下影响江苏省,两次冷空气均带来大风和降水,有效地清除了前期污染物,但随后全省PM_(2.5)浓度开始升高.第一次冷空气强度强于第二次,造成的污染也较重.WRF-Chem模式对本次过程的气象场和PM_(2.5)浓度模拟均较好,模拟观测相关系数分别达到0.52~0.99和0.40.模式能够较好地模拟出污染物的输送过程和时空分布.与第二次冷空气过程相比,第一次冷空气过程存在明显的污染物自北向南输送过程,100~500 m高空持续偏北气流(第2次过程为西北-偏西气流),期间全省平均边界层高度(PBLH)只有260 m(低于第2次过程的500 m),不利于污染物垂直扩散,造成地面浓度较高.利用HYSPLIT-4模式追踪了两次过程中淮安、泰州、无锡三站上空100 m处大气48 h后向轨迹,发现第一次过程中污染物来自山东中西部,第二次来自西部内陆地区.     

Oxidation of organic substances in aqueous solutions over Ru catalysts by oxygen

The catalytic performance of supported Ru catalysts has been studied in the reactions of wet oxidation of acetonitrile, N,N-dimethyl formamide and carbamide at T=433–533 K and P=2.0–4.6 MPa, and wet oxidation of real sewage from an alcohol plant (so-called Luther water) at T=403–473 K and P=1.5–3.6 MPa. The Luther water contained a mixture of low-boiling (C₁–C₅) aldehydes and alcohols. The experiments were carried out in a perfectly mixed batch autoclave reactor. The conversion of alcohols and aldehydes contained in the Luther water and selectivity of the process towards CO₂ and water as well as the selectivity of the oxidation of acetonitrile, N,N-dimethyl formamide and carbamide towards CO₂, N₂ and water were determined at various temperatures and reaction times. Ru (4.8 wt.%)/graphite-like carbon was effective in the oxidation of Luther water (ΔTOC=97.5% at T=423 K for 1 h), carbamide (X_CO(NH2)2=100%, S_{CO(NH2)2→CO2}=100%, S_{CO(NH2)2→N2}=71% at 473 K, 2 h) and acetonitrile (X_CH3CN=100%, S_CH3CN→CO2=100%, S_CH3CN→N2=75% at 493 K, 1 h). Ru/active carbon/γ-Al₂O₃ was effective in the oxidation of N,N-dimethyl formamide (X_HCON(CH3)2=100%, S_{HCON(CH3)2→CO2}=61%, S_{HCON(CH3)2→N2}=100% at 493 K).     

活性滤料滤池气提系统影响因素研究

为了研究气量、水深和提砂管规格对活性滤料滤池提砂系统性能的影响,本实验以石英砂作为活性滤料滤池的提升介质,在恒定水头状态下,测量了不同管径下被提升的水和砂的体积和质量随压缩空气流量的变化.结果表明:随着气量的增大,提升系统的提砂量和提砂效率均呈先增大后减小的趋势;提砂管管径是最大提砂量的限制因素,但提升的砂水体积比与管径无关;相同气量条件下,单位空气提砂量与水深呈线性关系.因此,在活性滤料滤池提砂系统的设计应用过程中应选择合适的提砂管径,尽量增加浸水率,并注意控制气量以提升系统能效.     

源头农业区不同类型水塘中水体沉积物磷吸附容量

湖泊和湿地沉积物性质受到其所在流域土地利用的显著影响.本实验以一个源头小流域的水塘系统为例,研究了位于不同土地利用中的水塘沉积物磷吸附特征.由于水塘分散于不同土地利用中,接收来自于不同土地利用的径流和土壤颗粒,水塘系统提供了研究磷吸附性质的极好范例.研究表明:水塘沉积物具有强的磷吸附容量.吸附最大值(S_max)为228～974mg·kg^-1,平衡浓度(EPC0)为0.004～0.032mg·L^-1,平均饱和度(DPS)仅为9.5%.水塘周围土地利用明显影响沉积物物理化学性质和吸附性质.对于S_max,周围土地利用为林地的山塘最大,而周围土地利用为村庄的村塘最小,其顺序为山塘>旱塘>田塘>河塘>村塘.对于EPC_O则正好相反,山塘<旱塘<田塘<河塘<村塘.分析表明,草酸浸提态铁(Fe_ox)同磷吸附最大值S_max具有显著正相关关系(r²=0.85,p<0.001),而KCl浸提态磷(KCl-P)同平衡浓度EPC_O具有显著正相关关系(r²=0.83,p<0.001).多重回归分析表明草酸浸提态铁(Fe_ox)和KCl浸提态磷(KCl-P)是控制水塘沉积物磷吸附的关键因子.     

The effect of wind velocity,air temperature and humidity on NH3 and SO2 transfer into bean leaves (phaseolus vulgaris L.)

The influence of wind velocity, air temperature and vapour pressure deficit of the air (VPD) on NH₃ and SO₂ transfer into bean leaves (Phaseolus vulgaris L.) was examined using a leaf chamber. The measurements suggested a transition in the properties of the leaf boundary layer at a wind velocity of 0.3–0.4 ms⁻¹ which corresponds to aRe_crit value of about 2000. At higher wind velocities the leaf boundary layer resistance (r_b) was 1.5–2 times lower than can be calculated from the theory. Nevertheless, the assessed relationships betweenr_b and wind velocity appeared to be similar to the theoretical derived relationship forr_b. The NH₃ flux and in particular the SO₂ flux into the leaf strongly increased at a VPD decline. The increase of the NH₃ flux could be attributed to an increase of the stomatal conductance (g_s). However, the increase of the SO₂ flux could only partly be explained by an increase ofg_s. An apparent additional uptake was also observed for the NH₃ uptake at a low temperature and VPD. The SO₂ flux was also influenced by air temperature which could be explained by a temperature effect ong_s. The results suggest that calculation of the NH₃ and SO₂ flux using data ofg_s gives a serious understimation of the real flux of these gases into leaves at a low temperature and VPD.     

Environmental chamber for study of the deposition flux of gaseous pollutants to material surfaces

A specially designed recirculating environmental chamber was constructed to study the environmental factors affecting the deposition of pollutant gases to the surface of stone and other building materials. The chamber and sample holder are designed to place samples in an aerodynamically well-defined air flow. The system is designed to permit use of radioactive ³⁵SO₂ as a tracer if necessary. A wide range of typical environmental conditions can be continuously maintained in the chamber. Wind speeds in the test section can range up to about 5 ms⁻¹, exposing replicate samples to air flow that is uniform to within approximately 3%. Relative humidity in the chamber can be maintained to within 3%, and SO₂, NO₂ and O₃ concentrations in the chamber air can be maintained to within 4%. Test results indicate SO₂ deposition and wind speed in the chamber are closely correlated, allowing for a direct determination of the surface resistance (r_c) component of the SO₂ deposition velocity to various test materials. Initial studies of SO₂ deposition to limestone and marble indicate the r_c values are approximately 1.3 s cm⁻¹ for fresh limestone and 34 s cm⁻¹ for fresh marble at 75% relative humidity, 26°C and 50 ppb SO₂.     

大气污染物垂直梯度自动监测系统的研制

设计的大气污染物垂直梯度自动监测系统是用 2个电磁阀实现 3个高度的气体采样 ,依靠分析仪器自身的抽气泵将气体样品通过聚四氟乙烯管抽入各分析仪器进行测量 ,并用一台微机和一块 AD/DA转换板实施对电磁阀的控制和数据采集 .现场观测实验表明 ,对于 25m长的采样管清洗时间可设置 1 min,而采样管长度间的差异不会导致测量 O₃、SO₂、NO和 NO₂ 小时平均浓度存在显著性差异 .     

Interdependence of the slopes and intercepts from log-log correlations of measured gas-particle paritioning and vapor pressure—I. theory and analysis of available data

Gas-particle partitioning is examined using a partitioning constant K_p = (F/TSP)/A, where F (ng m⁻³) and A (ng m⁻³) are the particulate-assiociated and and concentrations, respectively, and TSP is the total suspended particulate matter level (μg m⁻³). At a given temperature and for a given sample of particulate matter, compound-dependent values of K_p tend to be correlated with the sub-cooled liquid vapor pressure (p_L⁰, toor according to log K_p = m_r log p_L⁰+b_m. Theory predicts that b_r values should be somewhat similar, and that m_r values should be near −1. This is supported by field and laboratory work. However, there is still noticeable variability in reported m_r and b_r values, even when obtained by the same researchers sampling in the same location. Three possible thermodynamic sources of variability include variability in the compound-to-compound differences in the thermodynamics of adsorption, event-to-event variability in the specific surface area of the aerosol and event-to-event variability in the ambient temperature. Non-thermodynamic sources of variability include sorption of gaseous analytes to the filters used in differentiating between F and A, the presence of non-exchangeable component in the measured F values, within-event adsorption/desorption kinetics, within-event changes in contaminant levels, and within-event changes in temperature. Each of these sources of variability operate in their own way to cause variability in m_r and b_r. In general, one can expect there to be a correlation in the obseved m_r and b_r of the form b_r = m_sm_r+b_s. For the study of Yamasaki et al. (1982, Envir. Sci. Technol. 16, 189–194), one obtains m_s = 5.77 and b_s = −2.18, with r² = 0.91. In the presence of such a correlation, one can expect that all log (F/TSP)/A vs log p_L⁰ plot will tend to intersect at the same (x,y) poitn given by (−m_s, b_s. Exisiting field and laboratory data show this tendency.     

Evaluation of a detailed gas-phase atmospheric reaction mechanism using environmental chamber data

This paper describes an evaluation of the performance of a detailed gas-phase reaction mechanism in simulating the results of 561 experiments carried out in four different environmental chambers. The experiments included background air, NO_x-air, CONO_x-air and aldehyde-air irradiations used for chamber characterization, NO_x-air irradiations of single organics as well as simple and complex organic mixtures, and irradiations of auto exhaust. The methods used to represent the major chamber effects and the lighting characteristics in the model simulations of the experiments are described and their associated uncertainties are discussed. Statistical measures of the performance of the mechanism in simulating results of the various types of experiments are summarized and discussed. The mechanism was able to predict maximum ozone yields and rates of NO oxidation to within ±30% for 63% of the experiments modeled, and to within ±50% for 85% of the runs. There is a slight bias (∼15%) towards overprediction of ozone in mixture runs. Although there are cases where the simulations suggest possible problems with the gas-phase mechanism, much of the variability in the goodness of the fits could be attributed to uncertainties in chamber effects. It is concluded that better characterization of chamber conditions are needed if more comprehensive tests of atmospheric photochemical mechanisms are desired.     

造纸废水二级生化出水的电离辐射深度处理

探讨了采用电离辐射对造纸废水二级生化出水进行深度处理的可行性.结果表明,二级生化出水主要由相对分子质量为1000～3000和3000以上的有机物组成,它们对COD的贡献分别为69.5%和6.9%,它们对溶解性有机质（DOC）的贡献分别为40.6%和31.6%.电离辐射促使废水中的一些大分子有机物向小分子有机物转化,相对...     

北京自备井水源内毒素污染及与其他水质参数的相关分析

本研究采集驻京部队14个自备井水源样品,采用动态浊度东方鲎试验定量检测内毒素活性,同时检测了细菌总数(流式细胞术法)、异养菌平板计数(HPC)、菌落总数(平板法)、总大肠菌群、颗粒物特征、浊度、溶解性有机碳(DOC)和UV254值,比较了内毒素与这些水质参数的相关性.结果表明自备井水源的总内毒素活性为0.15~13.20 EU·m L~(-1),其中游离态内毒素活性为0.10~5.29 EU·m L~(~(-1)),结合态内毒素活性为0.01~8.60 EU·m L~(-1).对于内毒素污染较严重的自备井水源来说,结合态内毒素所占比例明显高于游离态内毒素.总内毒素与其他水质参数关联顺序为细菌总数(流式细胞术法)(r=0.88)HPC(r=0.79)DOC(r=0.77)UV254(r=0.57)总大肠菌群(r=0.50)菌落总数-平板法(r=0.49)=浊度(r=0.49)颗粒物总数(r=0.41).结合态内毒素与其他水质参数关联顺序为细菌总数-流式细胞术法(r=0.81)HPC(r=0.66)总大肠菌群(r=0.65)浊度(r=0.62)颗粒物总数(r=0.58)菌落总数(平板法)(r=0.22).游离态内毒素与水中DOC、UV254的相关系数r分别为0.58和0.26,结果表明游离态内毒素与水中DOC的相关性较大,与UV254相关性很小.     

焦化废水活性污泥法处理中微型动物群落及其与处理性能之间的关系

为了分析难降解焦化废水活性污泥法处理中的微型动物群落特征,本研究考察了活性污泥法焦化废水处理厂中的微型动物群落,分析了其与处理性能之间的相互关系.结果发现,本研究共采集的64个水样中,鉴别出28个种属微型动物,其中,原生动物27种(22种纤毛虫、4种鞭毛虫、1种有壳变形虫),1个类群微型后生动物.固着型和匍匐型纤毛虫为共优势群,固着型小口钟虫(Vorticella microstoma)为绝对优势种.除小口钟虫(V.microstoma)(出现频率100%)外,出现频率较高的种类还有轮虫(rotifers)(97%)、沟钟虫(Vorticella convallaria)(69%)等.与常规废水活性污泥法处理系统相比,焦化废水处理系统中的微型动物种类和数量相对偏低.相关性分析结果表明,生物学参数与出水水质、运行参数间存在着不同的相关性.其中,累枝虫属(Epistylis spp.)与出水氨氮(r=-0.740,p0.01)、氰化物(r=0.509,p0.05)和DO(r=0.514,p0.05)存在着显著的相关性;吸管虫属(Podophrya spp.)与硝化效率呈显著负相关(p0.05),它们可作为系统处理性能参数的指示微生物;其他种属与出水水质和运行参数间的相关性不显著(p0.05).因子分析揭示了与系统相关联的潜在的重要影响因素,以及某些微型动物种属间存在的相互关系.     

发酵稻壳对亚铁离子和硫离子的吸附-解吸附特性

为了解发酵稻壳对Fe2+和S2-离子的固定潜力,采用静态批式法研究了发酵稻壳对Fe2+和S2-离子的吸附行为,探讨了反应时间、溶液中Fe2+和S2-浓度、溶液p H、吸附反应环境温度及溶液离子强度对发酵稻壳吸附Fe2+和S2-特性的影响,并进一步通过解吸附试验了解发酵稻壳吸附态Fe2+和S2-的稳定性.结果表明,发酵稻壳吸附Fe2+(r=0.912 1)和S2-(r=0.901 1)的动力学过程均符合Elovich动力学模型,且Fe2+(R2=0.965 1)和S2-(R2=0.936 6)的等温吸附特征可较好地用Freundlich等温吸附模型描述.发酵稻壳对Fe2+和S2-的吸附为非优惠型吸附,其中对Fe2+的吸附为非自发反应,对S2-的吸附为自发反应.发酵稻壳对Fe2+和S2-的吸附过程是一吸热过程,升温有利于吸附作用的进行,发酵稻壳对Fe2+的吸附主要为配位吸附,而对S2-的吸附主要为阴离子交换吸附.一定p H范围内(1.50~11.50)发酵稻壳吸附Fe2+和S2-具有较强的适应性.同时随着离子强度的增加发酵稻壳对Fe2+的吸附量有所增加,而对S2-的吸附量略有减少,进一步证明发酵稻壳对Fe2+的吸附以内层配位为主,对S2-的吸附以外层络合为主.此外,不同p H条件及离子强度下发酵稻壳吸附的Fe2+和S2-解吸率很低,解吸率均小于10.00%.上述结果说明,发酵稻壳对Fe2+和S2-具有较好的吸附能力和环境适应性,吸附态Fe2+和S2-稳定性好,不易再释放.     

Influence of overlap between the laser beam tracks on surface quality in laser polishing of AISI H13 tool steel

Polishing by laser beam radiation is a novel manufacturing process to modify the initial surface topography in order to achieve a desired level of surface finish. The performance of laser polishing (LP) is determined by an optimum combination of several key process parameters. In this regard, the overlap between two successive laser beam tracks is one of the important LP process parameters, which has a significant effect over the final surface quality. In the current study, influence of overlap between the laser beam tracks on surface quality was experimentally investigated during the laser polishing of AISI H13 tool steel. Surface areas were polished by using four different overlap percentages (e.g. 80%, 90%, 95%, and 97.5%) while applying the same energy density. The improvement of surface quality was estimated through the analysis of line profiling surface roughness R_a, areal topography surface roughness S_a, and material ratio function. Also, individual components of the surface quality, e.g. waviness and roughness, and their evolution during LP were statistically analyzed using the power spectral density and the transfer functions. Finally, as an example of the best achieved LP result, flat surface area was polished using optimum set of the process parameters improving surface quality by 86.7% through the reduction of an areal topography surface roughness S_a from 1.35 μm to 0.18 μm.     

The effect of freezing on the composition of supercooled droplets—II. Retention of S(IV)

S(IV) dissolved in droplets is partially evolved as SO₂ during freezing. A spray of droplets with average diameter 39μm, produced by an ultrasonic transducer, was let to fall through a controlled atmosphere with known SO₂ concentration, at varying temperatures between −8 and −23°C, attaining thermal and chemical equilibrium. In a first arrangement, the droplets fell by gravitation on an ice surface. Two other arrangements simulated the riming ventilation conditions: in one series of experiments, the droplets were projected by a gas jet at several m s⁻¹ against a target; in another, the droplets were caught by rotating rods. The fraction of S(IV) retained in the ice Γ was determined by analysis of the samples and comparison with the equilibrium concentration in the liquid droplets. Samples collected by gravitation showed a retention coefficient Γ = 0.25 + 0.012 T_s (T_s = supercooling); rime samples showed large dispersion in the results, the retention coefficient being best represented by an average value Γ = 0.62, independent of temperature.     

Simple systems for calibrating and auditing SO2 monitors at remote sites

Described are compact, lightweight, rugged, and simple-to-operate pollutant generating systems that can be used to calibrate and to audit SO₂ and possibly other ambient air monitors located at inaccessible sites. The field and laboratory experiments done during the development of these systems are also described. The laboratory studies indicated that the systems could also be used for NO₂, but the field tests were inconclusive. The portion of the systems used to generate the dilution air is sufficiently inexpensive and modular that many networks could dedicate one zero (dilution) air system to each field site. The systems use a diaphragm pump, a cartridge containing Purafil/silica gel, a cartridge containing silica gel, a flow measuring system, and a low output permeation tube to generate pollutant concentrations between 1 and 30 ppbv with an accuracy (for SO₂) of better than 2 ppbv. To avoid using a temperature control device such as a bath or oven, the output of the permeation tube as a function of temperature is determined in the laboratory. At the field site, the temperature of the dilution air flowing over the permeation device and the barometric pressure are used to determine the output of the permeation device.     

Comparison of atmospheric nitrous acid measurements by annular denuder and differential optical absorption systems

As part of the Southern California Air Quality Study (SCAQS), nitrous acid (HONO) measurements were made at Long Beach, CA during the period 11 November–12 December 1987, using two distinctly different techniqes. One of these, the annular denuder method (ADM), used two denuders in tandem, coated with an alkaline medium to obtain 4- or 6-h integrated measurements. A small FEP Tefloncoated glass cyclone preceded the denuders to exclude coarse particles while minimizing loss or artifactual formation of HONO. Nitrite recoveries from the rear denuder were used to correct for sampling artifacts. In the second method, 15 min average HONO concentrations were measured with a differential optical absorption spectrometer (DOAS) coupled to a 25 m basepath, open multiple reflection system operated at a total optical path of 800 m. Period-averaged HONO concentrations from the two techniques were highly correlated (r = 0.94), with DOAS results averaging about 10% higher. However, ADM results were biased high at low HONO concentrations. HONO and NO concentrations showed a significant, positive correlation (r = 0.8), consistent with a common emission source (e.g. auto exhaust) for the two pollutants.