武汉市居民区大气VOCs的污染特征和来源解析

于2016年7月-2017年6月在武汉市典型居民区对大气中101种挥发性有机物（VOCs）进行了监测,以便研究武汉市典型居民区周边VOCs的组成特征和变化规律,并探讨了其主要来源.结果表明,武汉市空气中VOCs的体积分数为（46.24±24.57）×10^-9,表现为烷烃>含氧有机物>烯烃>卤代烃>芳香烃.受交通排放影响烷烃的比例上午高于下午,1月机动车尾气为武汉市主要的VOCs排放源,夏季含氧类化合物浓度高于冬季,可能更多地受本地喷涂等溶剂使用行业和光化学反应生成的影响,5-9月表现出明显的生物源排放特征.利用正交矩阵因子分析（PMF）得到武汉市居民区大气VOCs主要有6个来源,分别为燃烧源、机动车尾气、工业排放、溶剂使用、汽油挥发和植物排放.其中,燃烧源、机动车尾气贡献比例最高,是该区域VOCs控制的重要排放源.     

Analysis of VOC emissions using PCA/APCS receptor model at city of Shanghai,China

Qualification of the sources of volatile organic compounds (VOCs) and their effects on city air pollution are crucial issues to develop an effective air pollution control strategy in many polluted large cities of China. In this study, the VOC concentrations measured in Shanghai, China from 2006 to 2008 are analyzed. A receptor model (PCA/APCS; Principal Component Analysis/Absolute Principal Component Scores) is applied for identifying the contributions of individual VOC sources to VOC concentrations. Using the PCA/APCS technique, five and four surrogated VOC sources are classified in the center of Shanghai city in summer and in winter. In summer, the five VOC sources include PCs1 (liquefied petroleum gas/natural gas leakage and gasoline evaporation), PCs2 (vehicle related emissions), PCs3 (solvent usages), PCs4 (industrial productions), and PCs5 (biomass/biofuel/coal burning and other natural sources). In winter, the four VOC sources include PCw1 (liquefied petroleum gas/natural gas leakage and gasoline evaporation), PCw2 (solvent usages and industrial productions), PCw3 (vehicle related emissions), and PCw4 (biomass/biofuel/coal burning). The result suggests that during summer, 24, 28, 17, 18, and 13% of the measured VOC concentrations were estimated due to the PCs1, PCs2, PCs3, PCs4, and PCs5 VOC sources, respectively. During winter, 17, 48, 23, and 12% of the measured VOC concentrations were attributed to the PCw1, PCw2, PCw3, and PCw4 VOC sources, respectively. For aromatic concentrations, 35% of the concentrations were resulted from solvent usage (PCs3), following by industrial productions (PCs4) of 27%, and vehicle emissions (PCs2) of 19%. For alkene concentrations, the two largest contributors were due to gasoline industrial and vehicle emissions in both summer and winter. For alkane concentrations, the largest sources were due to gasoline industrial emissions (PCs1) and vehicle emissions (PCs2) in summer. In winter, vehicle emissions (PCw3), solvent usages/industrial productions (PCw2), and gasoline industrial emissions (PCw1) were the major sources. For halo-hydrocarbon concentrations, biomass/biofuel/coal burning and other natural sources were the major sources in both summer and winter.     

Characterization and source apportionment of volatile organic compounds in urban and suburban Tianjin,China

Tianjin is the third largest megacity and the fastest growth area in China, and consequently faces the problems of surface ozone and haze episodes. This study measures and characterizes volatile organic compounds(VOCs), which are ozone precursors, to identify their possible sources and evaluate their contribution to ozone formation in urban and suburban Tianjin,China during the Ha Chi(Haze in China) summer campaign in 2009. A total of 107 species of ambient VOCs were detected,and the average concentrations of VOCs at urban and suburban sites were 92 and 174 ppbv, respectively. Of those, 51 species of VOCs were extracted to analyze the possible VOC sources using positive matrix factorization. The identified sources of VOCs were significantly related to vehicular activities, which specifically contributed 60% to urban and 42% to suburban VOCs loadings in Tianjin. Industrial emission was the second most prominent source of ambient VOCs in both urban and suburban areas, although the contribution of industry in the suburban area(36%) was much higher than that at the urban area(16%). We conclude that controlling vehicle emissions should be a top priority for VOC reduction, and that fast industrialization and urbanization causes air pollution to be more complex due to the combined emission of VOCs from industry and daily life, especially in suburban areas.     

Vertical Evolution of Boundary Layer Volatile Organic Compounds in Summer over the North China Plain and the Differences with Winter

The vertical observation of volatile organic compounds(VOCs) is an important means to clarify the mechanisms of ozone formation. To explore the vertical evolution of VOCs in summer, a field campaign using a tethered balloon during summer photochemical pollution was conducted in Shijiazhuang from 8 June to 3 July 2019. A total of 192 samples were collected, 23 vertical profiles were obtained, and the concentrations of 87 VOCs were measured. The range of the total VOC concentration was 41–48 ppbv below 600 m. It then slightly increased above 600 m, and rose to 58 ± 52 ppbv at 1000 m.The proportion of alkanes increased with height, while the proportions of alkenes, halohydrocarbons and acetylene decreased. The proportion of aromatics remained almost unchanged. A comparison with the results of a winter field campaign during 8–16 January 2019 showed that the concentrations of all VOCs in winter except for halohydrocarbons were more than twice those in summer. Alkanes accounted for the same proportion in winter and summer. Alkenes,aromatics, and acetylene accounted for higher proportions in winter, while halohydrocarbons accounted for a higher proportion in summer. There were five VOC sources in the vertical direction. The proportions of gasoline vehicular emissions + industrial sources and coal burning were higher in winter. The proportions of biogenic sources + long-range transport, solvent usage, and diesel vehicular emissions were higher in summer. From the surface to 1000 m, the proportion of gasoline vehicular emissions + industrial sources gradually increased.     

泰州市大气挥发性有机物化学组分特征、活性及来源解析

挥发性有机物（VOCs）是臭氧和大气颗粒物的重要前体物,本研究利用在线气相色谱-质谱仪（Online-GC-MS）于2018年5—6月对江苏省泰州市大气中98种VOCs进行监测,依据监测结果对泰州市大气VOCs的组成特征、日变化趋势进行分析,对醛酮类VOCs数据进行参数化拟合探究其一次二次贡献,并采用正矩阵因子分解模型（PMF）对VOCs数据进行来源分析,用最大增量反应活性（MIR）计算臭氧生成潜势（OFP）.研究结果表明：泰州市大气VOCs中烷烃占比最高,其次为醛酮;烷烃、烯烃、卤代烃和芳香烃浓度日变化趋势明显,特征相近;参数化方法表明醛类物质主要来自于二次生成,而酮类物质主要来自一次排放;PMF模型结果表明泰州市VOCs的主要贡献源分别为机动车排放、油气溶剂挥发、生物质燃烧、其他工业和天然源;OFP的主要贡献物种为烯烃类,占比34.18%.研究结果表明,控制工业排放和溶剂使用是泰州市大气污染物控制的重点.     

PMF和PCA/APCS模型对南京北郊大气VOCs源解析对比研究

利用PMF模型和PCA/APCS模型对南京北郊大气VOCs进行定性和定量的源解析,并对比了两种模型的结果。结果表明：PMF模型对不同VOCs种类的模拟效果差别较大,而PCA/APCS对不同VOCs种类的模拟效果相近;PMF模型解析的源个数多于PCA/APCS模型,两种模型结果的源性质方面存在很大相似性,但PCA/APCS模型未能区分汽油挥发和汽车尾气源;两种模型源解析出的植物排放源、工业生产源的贡献率较接近,而其他源的贡献率存在差异,PCA/APCS模型解析的溶剂使用源的贡献率高于PMF模型结果,PMF模型解析出的汽油挥发+汽车尾气源的贡献率高于PCA/APCS模型结果。     

Stable Carbon Isotope Ratios and the Photochemical Age of Atmospheric Volatile Organic Compounds

Abstract

The dependence of ozone formation on the mixing ratios of volatile organic compounds (VOCs) and nitrogen oxides (NO_x) has been widely studied. In addition to the atmospheric levels of VOCs and NO_x, the extent of photochemical processing of VOCs has a strong impact on ozone levels. Although methods for measuring atmospheric mixing ratios of VOCs and NO_x are well established and results of those measurements are widely available, determination of the extent of photochemical processing of VOCs, known as photochemical age (PCA), is difficult. In this article a recently developed methodology for the determination of PCA for individual compounds based on the change in their stable carbon isotope composition is used to investigate the dependence between ozone and VOC or NO_x mixing ratios at a rural site in Ontario, Canada, during fall and winter. The results show that under these conditions the variability in VOC mixing ratios is predominantly a result of the varying impact of local emissions and not a result of changes in the extent of atmospheric processing. This explains why the mixing ratio of ozone shows no systematic dependence on the mixing ratios of VOCs or NO_x in this environment and at this time of the year.     

Ambient volatile organic compounds in the atmosphere of industrial central India

Volatile organic compounds (VOCs) are an important group of compounds because of their role in atmospheric chemistry and the risk they pose to human health and ecosystem. Therefore, the interest in determining VOCs in the atmosphere has increased over the last few decades to understand their emission, distribution, and sources. Considering the expanding urbanization and increasing use of fuels, very limited data of VOCs in India is available. This paper describes the chemical analysis of 12 light VOCs in 144 ambient air samples collected from three different sites near Raipur, India during a period of April, 2006-March, 2007 in order to understand their temporal and spatial distributions. This data has provided some important insights into the VOC profile, for the first time, of an industrial area in India. The annual average concentrations of all 12 VOCs in our study ranged from 43.2 to 160.4 μg m^?3 (mean: 95.6?±?31.0). The annual average concentration of individual VOCs in Raipur region ranged from 3.4 μg m^?3 for xylenes to 18.3 μg m^?3 for n-butane. n-Butane, i-butane, and propane were the three most abundant pollutants among all of the VOCs measured. The observed concentrations of these compounds in Raipur region were comparable to other Asian cities with some exceptions. The levels of total VOCs showed seasonal variations with a statistically significant winter maximum and lower values during summer and monsoon ranging from 55.9?±?9.9 μg/m³ in August to 144.5?±?15.5 μg/m³ in January. Sources of these VOCs have been described using species ratios and correlation studies.     

珠三角关键大气挥发性有机物的模拟精度评估

大气挥发性有机物（VOCs）是导致臭氧污染的关键前体物,是城市空气质量建模不可或缺的重要组成部分,但由于其非常复杂的构成和来源以及监测数据缺乏,目前对其模拟精度的了解仍非常有限。本文利用嵌套网格空气质量模式预报系统（NAQPMS）对珠江三角洲（简称珠三角）地区2017年9月21日至11月20日的VOCs开展了模拟试验,并利用光化学监测网8个地面站点的VOCs浓度监测数据,对模式模拟的关键VOCs组分进行了精度评估。结果发现,模式对强活性的甲苯、乙烯和二甲苯具有较高的模拟精度,模拟浓度偏差百分比为0.4%～26.6%,模拟能较好再现其日均浓度变化趋势和日变化的双峰特征。但是模式对化学反应活性强且与植物排放密切相关的异戊二烯具有很大的模拟偏差,偏差比近100%,无法再现其白天浓度高、夜间浓度低的观测日变化特征。通过分析发现,现有模拟系统主要考虑人为污染物排放而未考虑生物源排放,可能是导致这一模拟偏差的关键原因。同时,评估结果也表明模式在VOCs空间分布模拟上仍面临很大的不确定性。本文结果揭示了珠三角VOCs模拟面临的关键不确定性,表明融合VOCs观测数据来揭示并减小VOCs模拟的不确定性具有非常迫切的需求。     

Volatile organic compounds at a rural site in western Senegal

The objectives of this study were to identify species and levels of volatile organic compounds (VOCs), and determine their oxidation capacity in the rural atmosphere of western Senegal. A field study was conducted to obtain air samples during September 14 and September 15, 2006 for analyses of VOCs. Methanol, acetone, and acetaldehyde were the most abundant detected chemical species and their maximum mixing ratios reached 6 parts per billion on a volume basis (ppbv). Local emission sources such as firewood and charcoal burning strongly influenced VOC concentrations. The VOC concentrations exhibited little temporal variations due to the low reactivity with hydroxyl radicals, with reactivity values ranging from 0.001 to 2.6 s⁻¹. The conditions in this rural site were rather clean. Low ambient NO _x levels limited ozone production. Nitrogen oxide (NO _x ) levels reached values less than 2 ppbv and maximum VOC/NO _x ratios reached 60 ppbvC/ppbv, with an overall average of 2.4 ± 4.5 ppbvC/ppbv. This indicates that the rural western Senegal region is NO _x limited in terms of oxidant formation potential. Therefore, during the study period photochemical ozone production became limited due to low ambient NO _x levels. The estimated ozone formation reactivity for VOCs was low and ranged between −5.5 mol of ozone/mol of benzaldehyde to 0.6 mol/mol of anthropogenic dienes.     

2017年8—9月湖州市臭氧污染特征及其生成机制研究

近年来近地面臭氧问题日益凸显,成为影响空气质量持续改善的瓶颈.本研究基于2017年8—9月在湖州市城区开展的为期1个月的臭氧及其前体物挥发性有机物（VOCs）和氮氧化物（NO_x）在线观测数据,分析了臭氧及其前体物污染特征,利用正矩阵因子分析（PMF）解析了VOCs来源,并采用基于观测的模型（OBM）对臭氧生成机制进行研究.研究结果表明：1）观测期间湖州市VOCs平均体积分数为（24.78±9.10）×10^-9,其中占比最高的组成为烷烃、含氧VOCs （OVOCs）和卤代烃;2）在臭氧非超标时段,湖州市臭氧生成处于VOCs控制区,而在臭氧重污染期间湖州市处于以VOCs控制为主的过渡区;3）在臭氧超标时段,对臭氧生成潜势（OFP）贡献最大的是芳香烃（39.6%）,其次是烯烃（21.5%）和OVOCs （19.4%）,排名前三的关键组分为甲苯、乙烯和间/对二甲苯;4）源解析结果显示观测期间湖州市VOCs的主要来源是溶剂使用（27.0%）、交通排放（22.7%）、背景+传输（19.3%）、工业排放（16.9%）、汽油挥发（7.7%）和植物排放（6.4%）,重污染过程期间对OFP贡献最大的两类源是交通排放源和溶剂使用源,贡献百分比分别为35.1%和30.5%.因此,对交通排放和溶剂使用方面进行控制管理对湖州市大气臭氧污染防控有重要意义.     

Vertical Profiles of Volatile Organic Compounds in Suburban Shanghai

As Volatile Organic Compounds(VOCs) are one of the precursors of ozone, their distribution and variable concentrations are highly related to local ozone pollution control. In this study, we obtained vertical profiles of VOCs in Shanghai's Jinshan district on 8 September and 9 September in 2016 to investigate their distribution and impact on local atmospheric oxidation in the near surface layer. Vertical samples were collected from heights between 50 m and 400 m by summa canisters using an unmanned aerial vehicle(UAV). Concentrations of VOCs(VOCs refers to the 52 species measured in this study) varied minimally below 200 m, and decreased by 21.2% from 100 m to 400 m. The concentrations of VOCs above 200 m decreased significantly in comparison to those below 200 m. The proportions of alkanes and aromatics increased from 55.2% and 30.5% to 57.3% and 33.0%, respectively. Additionally, the proportion of alkenes decreased from 13.2% to 8.4%. Toluene and m/p-xylene were the key species in the formation of SOA and ozone. Principal component analysis(PCA) revealed that the VOCs measured in this study mainly originated from industrial emissions.     

Daily and monthly averaged aerosol optical properties and diurnal variability deduced from AERONET sun-photometric measurements at Thala site (Tunisia)

Summary Spectral aerosol optical thickness have been measured at Thala site (central West of Tunisia) from March to October 2001. The measurement site is located in a continental and non industrialized region, approximately 150 km from the North coast of the Mediterranean Sea and nearby the Algerian border. Thala site could be then influenced by the dust content of the continental air masses carried by western and southern winds. A second pollution source is constituted by industrial and/or maritime particles carried by northern and eastern winds. AOT measurements acquired through the ground-based AERONET are analyzed. The diurnal cycle over Thala and two other areas within the network showed various trends and a prevailing pattern of the optical thickness increase by 10–40% during the day. Daily AOT and monthly averaged aerosol optical thickness, ?ngstr?m coefficient and precipitable water vapor are computed and compared with those of other sites. Measured meteorological parameters represent a valuable supplement to the data sets with the sunphotometer measurements. The analysis of the results shows that there is a high correlation between aerosol optical properties (AOT and ?ngstr?m coefficient) and the local weather conditions, essentially wind speed and direction and air specific humidity.     

Study of the Impact of Industrial Emission on the Vegetation Grown Around Huelva (South of Spain) City

This paper reports the spatial pollution variability, obtained by using vegetal samples for biomonitoring atmospheric pollution around one of the most industrialized areas in the southwestern Spain (Huelva), through the study of the impact of industrial emissions on two Mediterranean species: Pinus pinea L. and Nerium oleander L.Samples were collected during spring of 2002, at different distances (0.5, 1, 2, 4, 6, 8 km) along two transects running to the dominant wind directions from the industrial complex and another against wind direction. Leaves and branches of the two species, together with soil samples were collected at each site. The concentration of Cu, Pb and Zn was determined by simultaneous inductively coupled plasma mass spectrometry (ICP/MS). Two principal emission sources of pollution were identified, one from industrial focus that markedly affects the level of Cu and Zn in the vicinity (0.5–1 km) of the industrial complex, and another one from secondary anthropogenic activities that are responsible of the high level of Cu, Pb and Zn. P. pinea is a better biomonitor of Zn than N. oleander. Pine needles are better biomonitors of Zn pollution than bark because of their physicochemical characteristic.     

A summer and winter apportionment of particulate matter at urban and rural areas in northern France

The apportionment of atmospheric aerosols undertaken in Northern France during two sampling campaigns allowed to determine the influence of the atmospheric contribution of a heavy industrialized urban center on the particulate matter composition at a nearby rural site. The concentrations of major components and trace elements sampled by bulk filtration have been determined on June–July 2000 and January–February 2001, and the comparison of these two campaigns shows very well the importance of wind directions. The sources of 10 trace elements (Al, Ba, Cu, Fe, K, Mn, Pb, Sr, Ti and Zn) and 7 major components (Cl⁻, NO₃⁻, SO₄²⁻, NH₄⁺, Na, Mg and Ca) are better identified by studying their elemental contribution at each sampling site according to wind sectors. This kind of study shows that the concentrations recorded at the urban sampling site are always higher than those observed at the rural site as well during the summer campaign (about + 35%) as during the winter campaign (+ 90%), because of the predominance of the W–NW wind sector, corresponding to the influence of the urban and industrialized areas.     

Source apportionment of visibility‐degrading aerosols in the lower fraser valley,B.C.

Abstract

The Lower Fraser Valley of British Columbia (LFV) is currently experiencing rapid population growth and is perceived to suffer from reduced air quality, specifically, elevated ozone concentrations and impaired visibility. It is necessary to identify the sources of visibility‐degrading aerosols in order to develop strategies to prevent further degradation and to institute measures to improve air quality in this region. Although chemical mass balance analyses have typically been used in such studies, herein, a P‐mode principal component analysis (PCA) is performed upon the ambient aerosol species at one polluted site in the LFV, and source profiles are inferred from the resulting component loadings. The loading coefficients on the five significant components (which account for over 70% of the variance in the fine aerosol speciation dataset) are used to assess the contribution of these sources to paniculate light scattering (b_sp) Automobile emissions and wood burning are found to contribute most to b_sp at this site.     

FY-3A MWHS资料的质量控制——以四川“8.19”暴雨为例

FY-3A MWHS微波湿度计辐射率资料空间分辨率高,同化后能有效地提高中尺度系统的数值预报的准确率。但如果不进行质量控制,任由误差大的离群微波资料进入同化系统,将会降低分析场精度,影响预报准确率。本文选取2010年8月17~19日的暴雨个例,应用主成分分析(PCA)方法,找出FY-3A微波湿度计数据中的离群值。结果表明:采用PCA方法,3天的资料总共识别出148个离群值样本,占总数的19.3%,其中通道三离群值占5.5%,通道四离群值占8.2%,通道五占5.4%。去除这些离群值后的MWHS数据总体分布,更靠近数据中心,各EOF方差贡献更加平滑。这说明PCA方法是一种可以抵抗少数离群值对总平均值影响的有效质量控制方法。      

基于PCA RBF的风电场短期风速订正方法研究

风电功率预测中最重要的因子是风速,准确的风速预测是风电功率预测的前提和基础。为了提高短期风速预测的准确性,本研究采用WRF模式,对我国上海崇明吕四风电场的风速进行预报。在此基础上,利用PCA-RBF算法结合WRF模式预报风向、气温、气压等气象要素对预报风速进一步订正。实验结果表明,利用PCA-RBF算法对WRF模式预报风速进行订正后,预报风速的误差进一步减小,相对均方根误差降低20%~30%,相对平均绝对误差降低15%~20%。与其他智能算法(BP算法、LSSVM算法)对比分析后得出,PCA-RBF算法对WRF模式预报风速具有较好的订正效果,能够有效提高风速预报准确率。     

Formulation and Evaluation of IMS, an Interactive Three-Dimensional Tropospheric Chemical Transport Model 3. Comparison of Modelled C2–C5 Hydrocarbons with Surface Measurements

In part 3 of this series of papers on a new 3-D global troposphericchemical transport model, using an Integrated Modelling System (IMS), anevaluation of the model performance in simulating global distributions andseasonal variations for volatile organic compounds (VOCs) in the atmosphere,is presented. Comparisons of model OH concentrations with previous modelstudies show consistent modelled OH levels from the subtropics tomidlatitudes, while more discrepancies occur over the tropical lowlatitudes, with IMS predicting the highest levels of OH. The close agreementbetween modelled OH concentrations over midlatitudes, where high surfaceNO_xand VOC concentrations are also found, is indicative of the strongphotochemical coupling between NO_x, VOCs and O₃ overthese latitudes. IMSOH concentrations in the Northern Hemisphere (NH) midlatitudes during summerare generally lower than available measurements, implying that models ingeneral are underestimating OH levels at this location and time of year.Substantial differences between model OH concentrations over low latitudesclearly highlight areas of uncertainty between models. IMS OH concentrationsare the highest in general of the models compared, one possible reason isthat biogenic emissions of species such as isoprene and monoterpenes arehighest in IMS, leading to higher O₃ levels and hence higher OH.Generally, the IMS VOC concentrations show a similar seasonality to themeasurements at most locations. In general though, IMS tends to underestimatethe NH wintertime VOC maximum and overestimate the NH summertime VOCminimum. Such an overestimate in summer could be due to IMSunderestimating OH levels, or an overestimation of VOC emissions or possiblya problem with model transport, all of these possibilities are explored.Except for n-pentane, the model underprediction of a VOC maximum during theNH winter month strongly suggests a missing emission mechanism in the modelor an underestimate of an existing one. It is very likely that there is alack of time varying emission sources in the model to account for theseasonal change in emission behaviour such as increasing energy usage (e.g.,electricity and gas), road transportation, engine performance, and otheranthropogenic factors which show strong seasonal characteristics. Theanomalous overprediction of wintertime n-pentane compared with its closesummertime prediction with the measurements suggest that emissions in thiscase may be too high.     

Hydrocarbon reactivity and ozone formation in Europe

Several studies have shown that in qualitative terms VOCs can be ranked in terms of their importance to ozone formation in Europe, using a so-called photochemical ozone creation potential (POCP). However, all studies showed significant variability in the quantitative POCP values assigned to each VOC species. In this paper, we make use of a complex photochemical oxidant model to quantify how the reaction time-scales of emitted VOC and their reaction products vary with geographical location and time of year. The model is used to evaluate monthly POCP values for 9 hydrocarbon and oxygenated VOC compounds for a cross-section across Europe. Calculations are presented to illustrate the gradients in POCP values of one species,n-butane, across the whole of Europe for April and June 1989. We discuss some of the factors responsible for these variations.