天津地区大气污染状况和气溶胶硫酸盐的研究

我们于1980—1981年对天津市大气污染物浓度做了同步监测,对天津市大气污染状况,二氧化硫转化为硫酸盐的过程及其对大气能见度的影响做了研究。以超C_i几率和的方法处理数据,研究结果表明,大气污染以早晨最严重,傍晚次之,中午较轻:冬季比夏季污染严重。各种污染物中以硫酸盐对大气能见度的影响最大,总颗粒物次之。当大气相对湿度大于70%时,对大气能见度的影响比较突出。颗粒物中的苯溶物对大气能见度有一定的影响。城市中相对湿度高时硫酸盐浓度大,可能是产生冬季烟雾事件的原因。下风方向的硫酸根浓度与二氧化硫浓度的比值和硫酸根含硫浓度与大气总硫浓度的比值均比上风方向相应的数值高,说明城市燃煤烟气是硫酸盐的来源。城市中硫酸根浓度与二氧化硫浓度的相关系数为0.77,硫酸根与颗粒物浓度的相关系数为0.95。在形成硫酸根的过程中二氧化硫浓度和颗粒物可能有贡献。以一维有源简化模式估算二氧化硫转化为硫酸根的速率常数,约为2.3±1.1%/hr,冬季约1.5%/hr。二氧化硫的迁移距离约为17—340km。     

Laboratory simulation of SO2 heterogeneous reactions on hematite surface under di erent SO2 concentrations

The variations of sulfate formation and optical coe cients during SO2 heterogeneous reactions on hematite surface under di erent SO2 concentrations were examined using in situ di use reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatograph (IC). Laboratory experiments revealed that within ambient SO2 of 0.51–18.6 ppmv, sulfate product, producing velocity, absorption and backward scattering coe cients showed an increasing trend with SO2 concentration. Under given SO2 concentration, the velocity of sulfate producing performed an evolution of initial increasing, midterm decreasing and final stabilizing. The reactive uptake and Brunauer-Emmett-Teller (BET) uptake coe cients of heterogeneous reactions rose with SO2 and exhibited high reactivities. Considering global warming, this result is important for the knowledge of heterogeneous reactions of SO2 on mineral particle surface in the atmosphere and the assessment of their impacts on radiative forcing.     

Mathematical modeling of cloud chemistry in the Los Angeles basin

A mathematical model of cloud chemistry was evaluated with the cloud chemistry data collected by Richardset al. (1983,Atmospheric Environment17, 911–914) from 1981 to 1985 in stratus clouds in the Los Angeles Basin. The model simulates atmospheric chemistry including gas-phase chemistry, aqueous-phase chemistry and droplet mass transfer, vertical transport, rainfall and turbulent diffusion.Evaluation of the model entailed two major part. First, the equilibrium chemistry is evaluated with a total of 52 case studies. Then, the model with treatment of cloud chemistry, vertical transport and diffusion is evaluated with two case studies. The results of the model simulations show the importance of vertical transport in determining the chemical composition of stratiform clouds.The sensitivity of sulfate, nitrate, ammonium and hydrogen ion concentrations to precursor levels, various chemical kinetic and cloud microphysical parameters and various environmental conditions is discussed.     

京津渤地区二氧化硫浓度分布模式

本文介绍一种适用于区域污染并考虑了二氧化硫在输送过程中转化为硫酸盐和被地面吸收等过程的烟团模式。根据北京、天津和渤海地区六氟化硫实验提供的扩散参数及该地区气象资料(风向、风速)和污染源资科,用模式计算出该地区在西北风,东南风为主的气象条件下二氧化硫浓度分布,并与实测值做了比较。     

Sulfur speciation and bioaccumulation in camphor tree leaves as atmospheric sulfur indicator analyzed by synchrotron radiation XRF and XANES

Analyzing and understanding the effects of ambient pollution on plants is getting more and more attention as a topic of environmental biology.A method based on synchrotron radiation X-ray fluorescence and X-ray absorption near edge structure spectroscopy was established to analyze the sulfur concentration and speciation in mature camphor tree leaves (CTLs),which were sampled from 5 local fields in Shanghai,China.Annual SO2 concentration,SO42-concentration in atmospheric particulate,SO42-and sulfur concentration in soil were also analyzed to explore the relationship between ambient sulfur sources and the sulfur nutrient cycling in CTLs.Total sulfur concentration in mature camphor tree leaves was 766-1704 mg/kg.The mainly detected sulfur states and their corresponding compounds were +6 (sulfate,include inorganic sulfate and organic sulfate),+5.2 (sulfonate),+2.2 (suloxides),+0.6 (thiols and thiothers),+0.2 (organic sulfides).Total sulfur concentration was strongly correlated with sulfate proportion with a linear correlation coefficient up to 0.977,which suggested that sulfur accumulated in CTLs as sulfate form.Reduced sulfur compounds (organic sulfides,thiols,thioethers,sulfoxide and sulfonate) assimilation was sufficed to meet the nutrient requirement for growth at a balanced level around 526 mg/kg.The sulfate accumulation mainly caused by atmospheric sulfur pollution such as SO2 and airborne sulfate particulate instead of soil contamination.From urban to suburb place,sulfate in mature CTLs decreased as the atmospheric sulfur pollution reduced,but a dramatic increase presented near the seashore,where the marine sulfate emission and maritime activity pollution were significant.The sulfur concentration and speciation in mature CTLs effectively represented the long-term biological accumulation of atmospheric sulfur pollution in local environment.     

Effectiveness of national air pollution control policies on the air quality in metropolitan areas of China

Understanding the effectiveness of national air pollution controls is important for control policy design to improve the future air quality in China. This study evaluated the effectiveness of major national control policies implemented recently in China through a modeling analysis. The sulfur dioxide （SO2） control policy during the llth Five Year Plan period （2006-2010） had succeeded in reducing the national SO2 emission in 2010 by 14% from its 2005 level, which correspondingly reduced ambient SO2 and sulfate （SO42-） concentrations by 13%-15% and 8%-10% respectively over east China. The nitrogen oxides （NOx） control policy during the 12th Five Year Plan period （2011-2015） targets the reduction of the national NOx emission in 2015 by 10% on the basis of 2010. The simulation results suggest that such a reduction in NOx emission will reduce the ambient nitrogen dioxide （NO2）, nitrate （NO3-）, 1-hr maxima ozone （03） concentrations and total nitrogen deposition by 8%, 3%-14%, 2% and 2%--4%, respectively over east China. The application of new emission standards for power plants will further reduce the NO2, NO3-, 1-hr maxima 03 concentrations and total nitrogen deposition by 2%-4%, 1%-%, 0-2% and 1%-2%, respectively. Sensitivity analysis was conducted to evaluate the inter-provincial impacts of emission reduction in Beijing-Tianjin-Hebei and the Yangtze River Delta, which indicated the need to implement joint regional air pollution control.     

Numerical modeling of long-range transport of acidic species in association with mesoβ-convective-clouds across the Japan sea resulting in acid snow over coastal Japan—II. Results and discussion

The acid snow/rain model [describedin Part I, Kitada et al., Atmospheric Environment27A, 1061–1076, 1993] was applied to investigate transport/transformation/deposition of acidic species in association with snow-precipitating cloud over the Japan Sea in winter. The model results showed: (1) The snow-precipitating clouds generated by relatively weak convective motions tend to trap aerosols of sulfate and nitrate and soluble gases such as SO₂ and HNO₃ below cloud levels, thus keeping their concentrations at higher levels than those for no-cloud situations. The mechanisms involved are: transfer of gas- and aerosol-phase species to cloud-phase through absorption and nucleation scavenging, then their transfer from cloud to snow through riming, and subsequent release from sublimating snow back to gas- and aerosol-phases below cloud base. (2) In-cloud oxidation enhanced the overall conversion of SO₂ to SO₄²⁻ by some 25% with respect to no-cloud situation after 12 h. Furthermore, contributions to the oxidation were 77.4%, 21.1% and 1.5% for S(IV)H₂O₂, S(IV)O₂ with catalysts of Fe³⁺ + Mn²⁺ and S(IV)O₃ reactions, respectively. (3) The sulfate wet deposited by precipitating snow for 12 h was due mostly to in-cloud scavenging and in-cloud oxidation, i.e. 66% by nucleation scavenging and the remaining by in-cloud oxidation of S(IV), while the contribution of below-cloud scavenging was negligible. (4) The adsorption process of HNO₃ onto the surface of falling snow was found to account for major below-cloud scavenging of snow, and thus in contrast to SO₄²⁻, the below-cloud scavenging contributed very significantly to the nitrate wet deposition. Throughout the stimulation, below-cloud scavenging was responsible for 75% of the snow-NO₃⁻ formation. Therefore, taking account of this process in acid snow models is important.     

Parameterization of episodical cloud and rainout events in large-scale atmospheric chemistry models

A parameterization scheme taking into account the episodical nature of rainout and incloud chemical transformation has been tested in a 2-D channel model. In the liquid phase many soluble gases are observed in concentrations never experienced in the gas phase. The effects on the trace gases SO₂ and hydrogen peroxide, when they are modified by clouds and precipitation, are studied. When incloud interaction of SO₂ and hydrogen peroxide is taken into consideration, calculated hydrogen peroxide profiles are brought closer to observed distributions. The effect of varying the time periods between cloud and rain events is tested. The impact on the formation and destruction of tropospheric ozone is also discussed.     

SO2气氛下Cu-Ce-O催化剂氧化柴油车排气碳烟的性能

运用程序升温氧化(TPO)对共沉淀法合成的Cu-Ce-O催化剂进行了活性评价,考察了在不同浓度的S0,气氛下cu-Ce-O催化剂氧化模拟碳黑的性能,并用BET、XRD、TPR和FT-IR对催化剂进行了表征.BET和XRD测试显示,cu和ce的结合使催化剂比表面积增大,晶体结构发生变化,形成了复合氧化物;TPO活性测试结果表明,Cu-Ce-O复合催化剂比单一组分的CuO或CeO2具有更好的低温催化活性.复合氧化物cu-Ce-O中Cu原子含量越高,对应硫化后的催化剂氧化碳烟的能力越低,同时催化剂表面生成的硫酸盐越多,即催化剂抗硫中毒能力也降低.浓度低于0.03%的SO2对Cu-Ce-O的催化性能有一定的促进作用,但SO2的体积分数超过0.03%后碳黑燃烧速率变慢;FT-IR初步证实了高体积分数的SO2所产生的大量SO24-可能是抑制催化剂活性的原因.     

Receptor modeling of the fine aerosol at a residential Los Angeles site

Receptor modeling on ambient aerosol and air quality data collected at Duarte, CA (a residential site near Los Angeles), in 1983 and 1987–1988 was carried out. A significant change in the ambient concentrations of SO₄²⁻, Al, Si, Mn, Fe, Pb, Br, volatile and organic carbon and fine particle (FP) mass took place from 1983 to 1987–1988. A drastic reduction (∼80%) of the ambient Pb and Br concentrations took place as the lead content and the usage of leaded gasoline decreased in the Los Angeles Basin during that period. A day-of-the-week analysis indicated that both crustal (Si, Ca, Fe) and transportation (Pb, CO, organic carbon and black carbon) related pollutants exhibit significantly different concentrations between weekdays and weekends of 1987–1988. this indicates that loadings of suspended soil dust are more affected by anthropogenic activities than meteorological patterns. In contrast, sulfate and volatile carbon concentrations seem to be insensitive to that cycle indicating that other sources/processes can be responsible for the ambient levels of these pollutants. Principal component analysis of aerosol and air quality data showed that the major contributions to the variance of the ambient aerosol loadings come from soil, motor vehicles and sulfates.     

Oxidation of SO2 in thin water films containing NH3

The reaction between NH₃ and SO₂ in thin water films was studied with a focus on the formation of sulfate. The reactions were conducted at 5 and 60% relative humidities or partial pressure of water vapor and at 0.04, 0.16 or 0.20 atm O₂ for temperatures between 20 and 50°C using a flow reactor and static flask reactors. In the presence of water vapor, the oxidation of SO₂ to sulfate was observed only when NH₃ was present. The product was primarily (NH₄)₂SO₄. Conversion of as much as 81% of the SO₂ to sulfate was observed after 10 min of reaction when the initial concentrations of SO₂ and NH₃ were 1 ppm and the relative humidity was 60%. Conversion was only 1–3% when NH₃ and/or water vapor were absent from the system. The surface of the reactor was found to influence the reaction by providing a place for a film of liquid water to form, and for the first several hours of reaction in the film, th e rate of sulfate formation was observed to be faster than oxidation in liquid water. In general, these results suggest that thin water films on environmental surfaces play a greater role in the deposition of atmospheric gases and the accumulation of their reaction products on surfaces than previously considered.     

The relationship between upwind SO2 emissions and SO4– concentrations in precipitation at six sites in the eastern U.S.A.

A method for estimating the upwind SO₂ emissions associated with individual wet SO₄²⁻ deposition events has been developed. The relationship between these estimates and wet SO₄²⁻ concentrations was examined at six Utility Acid Precipitation Study Program Sites (UAPSP) for the 1979–1986 period. Using Spearman correlation coefficients and the Bonferroni experimentwise criterion for statistical significance it was found that upwind emissions and concentrations were significantly related (p < 0.05). However, correlation's were sensitive to site location, time upwind of the emissions and season, and ranged from −0.03 to 0.50. Correlations were weaker at sites located west of the high emission region in the midwestern U.S.A. and stronger at sites further away and to the east of this region. There was a decrease in the strength of the correlations from the warm season to the cold season. It was also found that differences in meteorology between events obscured the relationship between emissions and concentrations. The effects of variations in ambient temperature and precipitation amount on wet SO₄²⁻ concentrations were taken into account by calculating partial correlation coefficients. A higher percentage of the resulting correlations were found to be statistically significant and the differences between sites decreased. This suggested that meteorological variability had a confounding influence on the detection of a link between concentrations and emissions. This influence should be considered when studying source-receptor relationships.     

Field studies of the SO2/aqueous S(IV) equilibrium in clouds

Concentrations of S(IV) were measured in cloudwater at Great Dun Fell and compared with theoretical HSO₃⁻ assuming equilibrium between aqueous and gaseous phases in cloud. Detectable concentrations of S(IV) in the range of 1 × 10⁻⁶ to 17.2 × 10⁻⁶ mol dm⁻³ were observed only in samples which contained low H₂O₂ concentrations, generally <1 × 10⁻⁶ mol dm⁻³. Concentrations of S(IV) were below the detection limit of 1 × 10⁻⁶ mol dm⁻³ in samples which contained hign H₂O₂ levels (1 × 10⁻⁶−80 × 10⁻⁶ mol dm⁻³) confirming that either SO₂ or H₂O₂ acts as the limiting reagent in the oxidation of SO₂ in cloudwater.Equilibrium HSO₃⁻ concentrations were estimated from the measured cloudwater pH, the gas phase SO₂ concentration and the ambient temperature and found to be on average about 5 times lower than the measured S(IV) concentrations. The possible role of formaldehyde in stabilizing S(IV) in cloudwater is discussed. The kinetic data available in the literature suggest that the complexation reaction between S(IV) and HCHO is too slow to account for the observed difference between measured and calculated S(IV) concentrations over the typical lifetime of clouds in our study.S(IV) accounted for up to 10% of the SO₄²⁻ measured in stored cloudwater samples.     

天津市2017年重污染过程二次无机化学污染特征分析

基于2017年天津市超级观测站数据,筛选出7次典型重污染过程,从污染物浓度、二次转化方面分析重污染过程二次无机化学污染特征.结果表明,重污染期间NO₃^-和SO₄^2-浓度较清洁天气增长幅度最高,显著高于PM_2.5的增长程度,说明二次无机转化是导致重污染期间PM_2.5污染加重的重要原因;下半年PM_2.5和SO₂污染程度较上半年减轻,与秋冬季采取燃煤治理等活动有关;重污染期间NO₂/SO₂比值为1.5~19.6,其中下半年NO₂/SO₂比值显著高于上半年,说明在各项污染源管控下移动源的影响比例相对增加;大部分重污染期间NO₃^-浓度大于SO₄^2-浓度,SOR值高于NOR值,说明重污染期间硫酸盐和硝酸盐转化均较重要;在SO₂浓度显著降低的情况下,重污染期间SO₄^2-浓度并未明显降低,说明除二次无机转化外,硫酸盐生成还受其他因素影响.     

A comparison of the corrosive action on Pentelic marble of nitrates and sulphates with the action of nitrogen oxides and sulphur dioxide

A comparison of the action on Pentelic marble of nitrates and sulphates with that of NO_x and SO₂ was achieved by passing the polluted ambient air through a filter pack before it entered the reactor chamber holding the marble grains. As a consequence the air reaching the marble was free of nitrates and sulphates, while it contained all the NO_x and SO₂. The effects on the marble grains were quantified and compared with those from a reactor through which unfiltered ambient air was passed simultaneously and under the same conditions. It was found that the action of the acids was much greater than that of the oxides, despite the fact that the concentrations of the latter were much greater.     

Heterogeneous reaction of SO2 on CaCO3 particles: Different impacts of NO2 and acetic acid on the sulfite and sulfate formation

Despite the heterogeneous reaction of sulfur dioxide (SO₂) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO₃) combined with NO₂ and acetic acid to investigate their effects on the heterogeneous reaction of SO₂ on CaCO₃ particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO₂ or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO₂ and SO₂ that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO₂ that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO₂ with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.     

大气质量标准技术经济评定的数学模型

本文从研究大气质量与改善大气环境的技术措施及经济投资三者之间的关系着手,建立一套数学模型为大气标准的评定提供一个实用的工具。并将此理论模型应用于北京市SO_2年平均浓度二级标准的评定工作,得出以0.08mg/m~3为宜的结论。 本文所提出的数学方法对其他环境要素的质量标准的评定及某些技术经济问题也有一定的参考意义。     

The vertical distribution of aerosols and acid related compounds in air and cloudwater

Vertical profiles (surface to 5 km) of aerosol particle number concentration, NO_y′ mixing ratio, and cloudwater SO₄²⁻ and NO₃⁻ equivalent concentration were obtained in three field studies: North Bay, Ontario, during the summer of 1982 and the winter of 1983–1984, and Syracuse, New York, during the fall of 1984. The measurements from these locations and different seasons are compared. Generally, airborne concentrations are highest with air-mass back trajectories from the south and lowest with back trajectories from the north. For the southerly trajectories, median particle number concentrations (0.2–2 μm) near ground level (950 mb) vary from 1700 cm⁻³ during the summer project to 800 cm⁻³ during the winter project. At 700 mb, the south trajectory particle number concentration ranged between 60 and 170 cm⁻³. Median NO_y′ mixing ratios for southerly back trajectories were approximately 6 and 9 ppb at 950 mb and 0.4 and 0.8 ppb at 700 mb for the fall and winter projects, respectively. Comparison of particle number concentration profiles outside of cloud with cloud droplet plus interstitial aerosol particle number concentrations inside cloud indicate that cumulus clouds can transport aerosols vertically from below cloud base. In contrast, stratiform clouds have similar concentrations inside the clouds as outside at the same altitude. The vertical variations of cloudwater sulphate and nitrate concentrations and the NO₃⁻/SO₄²⁻ equivalent concentration ratio are discussed for each of the three field studies.     

2010年广州亚运期间空气质量与污染气象条件分析

利用2010年11月4日～12月10日广州地区NO2、O3、SO2、PM、能见度实测资料,区域空气污染指数RAQI及大气输送扩散特征参数,分析广州亚运期间空气质量与气象条件变化特征.结果表明,亚运期间空气质量比亚运前后好,能见度比亚运前后大,PM1和PM2.5浓度比亚运前后小,能见度与PM1和PM2.5有较好的反相关;亚运期间NO2和SO2日均值和小时均值均达到国家一级标准,PM10日均值和O3小时均值均满足国家二级标准,污染物得到较好的控制;广州地区SO2受本地源和外地源远距离输送叠加影响,NO2受本地源影响较大;广州周边城市NO2、SO2和PM10有向广州输送的潜势,而广州O3有向其周边城市扩散的潜势;亚运期间污染气象条件比亚运前后有利,亚运期间污染物浓度降低得益于政府实施的减排措施及良好的气象条件.     

The response of sulfate linearity and precipitation chemistry to gas-phase profiles

Results are reported from a series of cloud chemistry simulations designed to evaluate the sensitivity of precipitation sulfate concentrations to changes in the shape and mass of the preexisting gas phase profiles. Linearity factors relating chemical inflow conditions to depositio are evaluated. The height from which any given fraction of the sulfur in precipitation came in stratiform storms was found to be approximately equal to the height at which the corresponding fraction sulfur was located. This source height was greater for convective storms. Changes in the total sulfur generally resulted in an almost proportional change in the resulting precipitation sulfate concentrations. Because stratiform storms rely more strongly on the initial gas-phase profiles to define the available oxidant at a given height, the deposition and SO₂ linearity factors associated with such storms were found to be more sensitive to the initial height dependence of the ratio [SO₂] and [H₂O₂] than was found for convective storms. The deposition and the linearity factor for convective storms were found to be more strongly dependent on the total column mass of these species. The precipitation sulfate concentration and linearity were found to be generally insensitive to perturbations in the fine structure of the initial gas-phase profiles.