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1.
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.  相似文献   

2.
Volatile organic compounds (VOCs) were measured at two sites in a highly industrialized zone in western Canada from September 2004 to March 2006. Principal component analysis (PCA) with varimax rotation was performed on 30 VOCs to identify the pollution sources. Aliphatics, aromatics, and halogenated aliphatics were studied. The two monitoring sites were 11 km apart, with site 1 closer to the city of Fort Saskatchewan and site 2 predominantly down wind from the industrial sources. PCA results provided the basis for interpreting the relationship between the ambient 24-h integrated VOC samples and the emission sources in the region. Challenges existed in interpreting the PCA results in such a highly industrialized region; however a unique feature to this study was the fact that the region was home to the only 1,2-dichloroethane emitting facility in Canada. Other specific industry related VOCs in the region were vinyl chloride, styrene and HCFC-22. Making use of these specific VOCs in the PCA allowed for easy identification of an industrial contribution. For factors that were not easily distinguishable, further PCA tests were conducted using carbon monoxide concentrations, wind direction data and seasonal splitting of the samples. The analysis found that five factors accounted for 82% of the variance at site 1 and five factors accounted for 81% of the variance at site 2. The factor accounting for the highest variability (∼40%) at the two sites was the most difficult to interpret, but showed contributions from both industry and vehicle related emissions. Specific industrial sources were identified using 1,2-dichloroethane as a chemical tracer or by corroborating wind speed with known industry VOC emissions. Both sites had two factors identified as specific industry sources and these factors totaled to over 20% of the variance. Long range transport of stable halogenated compounds accounted for greater than 10% of the variance, and seasonal effects accounted for 5% of the variance.  相似文献   

3.
This study uses the WRF-Chem model combined with the empirical kinetic modeling method (EKMA curve) to study the compound pollution event in Beijing that happened in 13-23 May 2017. Sensitivity tests are conducted to analyze ozone sensitivity to its precursors, and to develop emission reduction measures. The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze. When VOCs and NOx were reduced by the same proportion, the effect of O3 reduction at peak time was more obvious, and the effect during daytime was more significant than at night. The degree of change in ozone was peak time > daytime average. When reducing or increasing the ratio of precursors by 25％ at the same time, the effect of reducing 25％ VOCs on the average ozone concentration reduction was most significant. The degree of change in ozone decreased with increasing altitude, the location of the ozone maximum change shifted westward, and its range narrowed. As the altitude increases, the VOCs-limited zone decreases, VOCs sensitivity decreases, NOx sensitivity increases. The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited. Upon examining the EKMA curve, we have found that suburban and urban are sensitive to VOCs. The sensitivity tests indicate that when VOCs in suburban are reduced about 60％, the O3-1h concentration could reach the standard, and when VOCs of the urban decreased by about 50％, the O3-1h concentration could reach the standard. Thus, these findings could provide references for the control of compound air pollution in Beijing.  相似文献   

4.
We present a comprehensive discussion on what cause high ozone episodes at a suburban photochemical observation site of the Seoul Metropolitan Area (population ～23 million). The observational site, Taehwa Research Forest (TRF), is situated ～30 km from the center of Seoul. In June 2011, we observed two very distinctive ozone periods-high ozone (peak up to 120 ppbv) and low ozone (peak up to 60 ppbv) in the mid and early month, respectively. The trace gas measurement dataset, especially CO and NO X clearly indicate that less anthropogenic influences during the high ozone period. Volatile organic compound (VOC) measurement results show that at the observational site, biogenic VOCs (mostly isoprene) contribute most of chemical reactivity towards OH, although toluene from anthropogenic activities was observed in higher concentrations. Back-trajectory analysis indicates that air-masses from the forest part of Korea Peninsula were dominant influences during the high ozone episode event. On the other hand, Aged air masses from China were the dominant influence during the low ozone episode event. Model calculations conducted using the University of Washington Chemical Mechanism (UWCM) box model, also consistently show that BVOC, especially isoprene photochemistry, can be the significantly contribution to local ozone formation in the given photochemical environments of TRF. These research results strongly suggest that ozone control strategy in the Eastern Asian megacities, mostly situated in surrounding forest areas should be based on the comprehensive scientific understanding in BVOC photochemistry and interplays between anthropogenic and biogenic interactions.  相似文献   

5.
Understanding the chemical links between ozone (O3) and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOC), is important for designing effective photochemical smog reduction strategies. This chemical relationship will determine which precursor (NOx or VOC) emission reduction will be more effective for decreasing the ozone formation. Under certain conditions, ozone levels decrease as a result of a reduction in NOx emissions but do not respond significantly to changes in VOC emissions (NOx-sensitive condition), while under other conditions ozone concentrations decrease in response to reductions in VOCs and may even increase when NOx emissions are reduced (VOC-sensitive conditions). Indicator species can be used to assess the sensitivity of ozone to changes in the emissions of its precursors. These indicators are species or species ratios involved in ozone photochemistry which reflect the primary chemical process through which the ozone was formed. In this work we use the MM5-CAMx model system to explore the behaviour of various indicator species during two meteorological situations featuring different atmospheric conditions in a complex terrain area. The results show that indicators based on nitrogen compounds (i.e,. NOy and NOz) are suitable for defining the transition range from VOC- to NOx-sensitive chemistry, and that despite the uncertainties associated with the use of chemical indicators, the ratios O3/NOy and O3/NOz may provide a simple and useful way to summarize the response of ozone to changes in NOx and VOC emissions in Southwestern Spain.  相似文献   

6.
为解决城市边界层中大气O3浓度的预报问题，选用一种简明有效的光化学反应方案建立光化学模式, 并与大气平流扩散的箱格预报模型进行了嵌套，从而将大气化学过程引入到城市空气污染数值预报系统 (CAPPS) 中。同时，根据实际需要研究了VOC (Volatile Organic Compounds) 浓度及NOx源排放量等参数缺测时，根据前期监测浓度采用遗传算法反演未知参数的具体方法。利用2001年9月8~17日在北京舞蹈学院监测的O3、NOx资料及相应的气象数据，用改进后的CAPPS模式进行了单箱预报试验。预报试验结果表明，嵌套后的模式对O3浓度的变化具备一定的预报能力。  相似文献   

7.
餐饮排放是城市地区挥发性有机物（VOCs）重要的无组织来源,由于其排放特征复杂,是大气环境研究和管理的薄弱环节.本研究采用了现场和实验模拟两种采样方式,利用2,4-二硝基苯肼（DNPH）采样柱和不锈钢罐分别采集羰基化合物和全空气样品,然后利用高效液相色谱（HPLC）和气相色谱-质谱联用仪（GC-MS/FID）对116种组分进行定性定量分析.在此基础上,分析了餐饮源VOCs的排放特征及其影响因素.总体来看,含氧有机物（OVOCs）和烷烃是VOCs浓度的主要贡献者,但不同餐饮源的源谱特征差异较大.另外,通过比较发现食用油的种类、油的使用次数、加热方式、烹饪方式和调味料等因素会对餐饮源VOCs排放特征造成显著影响.进一步分析了不同菜系所排放VOCs的臭氧生成潜势（OFP）,关键组分主要是甲醛、乙醛、丁烯醛、乙烯和丙烯等.本研究成果能够补充我国餐饮源VOCs控制所需的基础数据.  相似文献   

8.
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.  相似文献   

9.
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。  相似文献   

10.
Fine aerosol samples were collected throughout spring, summer, and winter in 2004∼2005 at a major urban traffic junction (BNU) and a suburban location (MY) in Beijing and at a downtown site (SH) in Shanghai, China. Ten of the 16 EPA priority polycyclic aromatic hydrocarbons (PAHs), seven fatty acids, levoglucosan, and cholesterol were identified and quantified. PAHs detected in Beijing and Shanghai were up to one order of magnitude higher than those reported in the developed countries either in urban or suburban areas, while levoglucosan was one order of magnitude lower than that in other countries for no biomass combustion in domestic heating in the mega-cities in China. PAHs showed the same seasonal trend in all sampling sites as the highest in winter and the lowest in summer, while fatty acids no pronounced seasonal variation. A significant fraction of levoglucosan from cooking with higher concentrations in urban than in suburban area contributed to the ambient atmosphere, indicating that the main source of levoglucosan in urban environment would be cooking rather than biomass burning. The relative contributions of coal combustion and vehicle exhaust sources to PAHs in fine aerosols were preliminarily estimated to be 1:2 in Beijing and 1:1 in Shanghai, revealing that the air pollution in these mega-cities in China was mainly the mixing of coal combustion with vehicle exhaust. Cooking was one of the major sources of organic aerosols in both Beijing and Shanghai.  相似文献   

11.
利用2019年8月13日—9月30日江苏省13个设区市离线监测的VOCs数据,对江苏省城区VOCs污染特征及其关键活性组分进行分析研究.结果表明,江苏省逐日VOCs的体积分数范围为8.83×10-9~45.11×10-9,表现为烷烃 > 芳香烃 > 烯烃 > 炔烃.江苏省13个设区市VOCs的体积分数为7.85×10-9~30.52×10-9,徐州市VOCs最高,这与徐州市监测点位置分布及其工业结构相关.全省13个设区市臭氧浓度处于优、良、轻度污染和中度污染时,VOCs总体积分数分别为14.96×10-9、17.96×10-9、25.85×10-9和25.11×10-9,臭氧浓度处于污染状态时的VOCs高于优、良状态,且炔烃占比随着臭氧污染程度的加重呈升高趋势,表明现阶段臭氧生成与人类活动关系密切.通过加权的方式筛选出间/对二甲苯、乙烯、甲苯、丙烯、异戊二烯、邻二甲苯等物种,它们是目前对江苏省城区影响程度较大且影响范围较广的关键活性物种.  相似文献   

12.
As the key precursors of O_3, anthropogenic non-methane volatile organic compounds(NMVOCs) have been studied intensively. This paper performed a meta-analysis on the spatial and temporal variations of NMVOCs, their roles in photochemical reactions, and their sources in China, based on published research. The results showed that both nonmethane hydrocarbons(NMHCs) and oxygenated VOCs(OVOCs) in China have higher mixing ratios in the eastern developed cities compared to those in the central and western areas. Alkanes are the most abundant NMHCs species in all reported sites while formaldehyde is the most abundant among the OVOCs. OVOCs have the highest mixing ratios in summer and the lowest in winter, which is opposite to NMHCs. Among all NMVOCs, the top eight species account for 50%-70% of the total ozone formation potential(OFP) with different compositions and contributions in different areas. In devolved regions, OFP-NMHCs are the highest in winter while OFP-OVOCs are the highest in summer. Based on positive matrix factorization(PMF) analysis, vehicle exhaust, industrial emissions, and solvent usage in China are the main sources for NMHCs. However, the emission trend analysis showed that solvent usage and industrial emissions will exceed vehicle exhaust and become the two major sources of NMVOCs in near future. Based on the meta-analysis conducted in this work,we believe that the spatio-temporal variations and oxidation mechanisms of atmospheric OVOCs, as well as generating a higher spatial resolution of emission inventories of NMVOCs represent an area for future studies on NMVOCs in China.  相似文献   

13.
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14.
A Unified Regional Air-quality Modelling System, AURAMS, was expanded to predict six toxic volatile organic compounds (VOCs) within a continental domain and two nested domains covering eastern and western Canada. The model predictions were evaluated against Environment Canada’s National Air Pollution Surveillance (NAPS) data set to assess the predictive capability of the model at daily and seasonal time scales. The predictions were also evaluated with satellite-derived column total maps for formaldehyde, carbon monoxide, and nitrogen dioxide. In general, the model showed fair to good predictive skill in terms of both correlation (R) and normalized mean bias (NMB) for benzene (R = 0.53 NMB = 26 %), formaldehyde (R = 0.73, NMB = ?15 %) and acetaldehyde (R = 0.55, NMB = 29 %). For the other toxics VOCs, the model showed less predictive skill in the order 1,2,4-trimethylbenzene (R = 0.50, NMB = ?41 %), 1,3-butadiene (R = 0.26, NMB = 40 %) and acrolein (R = 0.052, NMB = ?51 %). The goal of this study was to apply an air quality model to assess the contribution of mobile sources to ambient levels of toxic VOCs at urban locations across Canada. The mobile source contribution varied in a complex manner for each species for different regions. For benzene and 1,2,4-trimethylbenzene, the mobile source contribution was in the range 40–65 % for major Canadian cities. The model predicted considerably lower mobile source contributions for rural locations in the Canadian Prairies, where other area sources dominate, such as the petrochemical industry. Measured concentration trends in toxics are also presented from 2004 to 2010. The primary emitted toxics declined gradually (13–16 % over 6 yr) whereas the toxic aldehydes showed no trend.  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
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（NOx）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.  相似文献   

18.
Volatile organic compounds (VOCs) emissions by vegetation present in the Mediterranean area are not well known. They may contribute with anthropogenic VOC emissions to the tropospheric ozone formation that reaches important level in the European Mediterranean region. The present work, carried out as part of the European ESCOMPTE project «fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions», adds a new contribution to the inventory of the main natural hydrocarbons sources likely to participate in the ozone production. The corresponding measurement campaign was conducted in La Barben, a site close to Marseilles (France), with the aim to quantify the terpenic emission pattern and the behaviour of Pinus halepensis, an important Mediterranean species slightly studied.The determination of biogenic emissions from P. halepensis was done by the enclosure of an intact branch in a Teflon cuvette. Main emitted monoterpenes were β trans-ocimene and linalool. The total monoterpenic emission rates thus recorded were found to reach maximum values around 30 μg gdry weight−1 h−1. The normalized emission rates calculated at 30 °C and 1000 μmol m−2 s−1 with Guenther's algorithm was 14.76, 8.65 and 4.05 μg gdry weight−1 h−1, respectively, for the total monoterpenes, β trans-ocimene and linalool.  相似文献   

19.
区域大气质量评价数值模式系统的建立及试用   总被引：4，自引：0，他引：4  
区域大气质量评价数值模式系统是以CALPUFF的应用开发为核心,根据陕西省的实际情况和大气环境业务服务需求,利用预报实时业务的网络环境,通过VB6.0编程,建立了一个具有自动数据处理、操作简便、比较实用的区域大气质量评价数值模式系统平台。依据2004年1月1日至12月31日的气象资料及源排放清单,对某工程的5个拟建地进行了大气质量数值模拟评价分析。结果表明,5地日均浓度超标的概率分别为27%、11%、5%、3%、8%。年平均浓度5地中3地未出现超负荷浓度值,满足2级标准要求,其他2地出现超负荷浓度值。其中一地污染超标最重,其可能原因是由于山体的影响,山谷中低层水平风速相对较小,不利于污染物的水平扩散,同时易形成地形山谷风次级环流,次级环流的存在把输送出去的污染物带回原地,形成二次污染。  相似文献   

20.
Atmospheric concentrations of ca. 250 C6–C15 hydrocarb on and C4–C12 oxygenated volatile organic compounds (VOC) including alkanes, benzene and alkyl benzenes, monoterpenes and aldehydes were measured in August 1994 during the POPCORN campaign (POPCORN = Photo-Oxidant formation by Plant emitted Compounds and OH Radicals in North-Eastern Germany). About 80 substances together contributed 90% of the atmospheric carbon in this range of molecular weight. During this field campaign VOC-emissions from several crop and tree species and the ambient concentrations of CO, C2–C7 non-methane hydrocarbons (NMHC), C1 and C2 aldehydes, nitrogen oxides, ozone and hydroxyl-radicals (OH) were also measured. These data were used to interpret the VOC measurements presented here. The on-line GC–MS used for the VOC measurements combines adsorptive sampling with thermal desorption and GC–MS analysis in an automated system. Internal standards were used to quantify the measurements. Ozone was destroyed prior to the sample preconcentration through the gas phase reaction with NO. Aromatic compounds like benzene, toluene and xylenes were the most abundant compound class among the measured substances, -pinene and 3-carene, most probably originating from pineforests ca. 1 km away from the measuring site, were the most abundant monoterpenes. The highest mixing ratios of most compounds were measured in nights with strong inversion situations. The toluene mixing ratios then reached 630 pptv; -pinene mixing ratios went up to 430 pptv. The median of all toluene and -pinene measurements during the campaign was 125 pptv or 22 pptv, respectively. These values are on the lower end of ambient measurements reported for continental sites. In most samples also n-pentanal, n-hexananl, n-nonanal and n-undecanal were present. Median mixing ratios were 9, 16, 14 and 8 pptv, respectively. Emission studies indicate that these highly reactive compounds are most probably emitted from maize. It is shown by a simple first order approach that the potential for ozone formation during the POPCORN campaign was roughly equal for anthropogenic and biogenic VOC. From measured concentrations of ozone, OH-radicals, methane, CO, C2–C15 nonmethane hydrocarbons (NMHC) and C5–C11 aldehydes a photochemical production of ozone in the order of 3.5 ppb/h can be estimated. Apart from formaldehyde and acetaldehyde, which are at least partly products of VOC oxidation, the substance group with the largest contribution to the VOC turnover are the monoterpenes. They contribute ca. 30%. However, the mechanism of terpene oxidation is very complex and presently only partly understood. Thus the actual contribution of monoterpenes to ozone formation is very uncertain. Other measured compound classes such as light alkenes, alkanes, aromatics, and C5–C11 aldehydes contribute each between 10% and 15% to ozone formation. The measuring site was not influenced directly from strong biogenic or anthropogenic sources, and the results obtained during the POPCORN campaign can be regarded as a typical picture of a remote rural central European environment.  相似文献   

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