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1.
Min XUE Jianzhong MA Guiqian TANG Shengrui TONG Bo HU Xinran ZHANG Xinru LI Yuesi WANG 《大气科学进展》2021,38(7):1209-1222
Photochemical smog characterized by high concentrations of ozone (O3) is a serious air pollution issue in the North China Plain (NCP) region, especially in summer and autumn. For this study, measurements of O3, nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), nitrous acid (HONO), and a number of key physical parameters were taken at a suburban site, Xianghe, in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O3 formation and find an optimal way to control O3 pollution. Here, the radical chemistry and O3 photochemical budget based on measurement data from 1-23 July using a chemical box model is investigated. The daytime (0600-1800 LST) average production rate of the primary radicals referred to as ROx (OH + HO2+ RO2) is 3.9 ppbv h-1. HONO photolysis is the largest primary ROx source (41％). Reaction of NO2 + OH is the largest contributor to radical termination (41％), followed by reactions of RO2 + NO2 (26％). The average diurnal maximum O3 production and loss rates are 32.9 ppbv h-1 and 4.3 ppbv h-1, respectively. Sensitivity tests without the HONO constraint lead to decreases in daytime average primary ROx production by 55％ and O3 photochemical production by 42％, highlighting the importance of accurate HONO measurements when quantifying the ROx budget and O3 photochemical production. Considering heterogeneous reactions of trace gases and radicals on aerosols, aerosol uptake of HO2 contributes 11％ to ROx sink, and the daytime average O3 photochemical production decreases by 14％. The O3-NOx-VOCs sensitivity shows that the O3 production at Xianghe during the investigation period is mainly controlled by VOCs. 相似文献
2.
The objective of the present study was to better understand the impacts of the additional sources of nitrous acid （HONO） on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain （NCP） during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry （WRF/Chem） model were performed, including three additional HONO sources： （1） the reaction of photo-excited nitrogen dioxide （NO~） with water vapor; （2） the NO2 heterogeneous reaction on aerosol surfaces; and （3） HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% （3-4 km） in local urban areas of the NCP. Monthly-mean concentrations of NO3, NH＋, SO]- and PM2.5 were increased by 20%-52% （3-11μg m-3）, 10%-38%, 6%-10%, and 6%-11% （9-17 μg m-3）, respectively; and in urban areas, monthly-mean accumulation- mode number concentrations （AMNC） and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NOx and aerosols. 相似文献
3.
Yawei QU Tijian WANG Yanfeng CAI Shekou WANG Pulong CHEN Shu LI Mengmeng LI Cheng YUAN Jing WANG Shaocai XU 《大气科学进展》2018,35(11):1381-1395
Particulate matter with diameters of 2.5 μm or smaller(PM_(2.5)) and ozone(O_3) are major pollutants in the urban atmosphere. PM_(2.5) can affect O_3 by altering the photolysis rate and heterogeneous reactions. However, these two processes and their relative importance remain uncertain. In this paper, with Nanjing in China as the target city, we investigate the characteristics and mechanism of interactions between particles and O_3 based on ground observations and numerical modeling.In 2008, the average concentrations of PM_(2.5) and O_3 at Caochangmen station are 64.6 ± 47.4 μg m~(-3) and 24.6 ± 22.8 ppb,respectively, while at Pukou station they are 94.1 ± 63.4 μg m~(-3) and 16.9 ± 14.9 ppb. The correlation coefficient between PM_(2.5) and O_3 is -0.46. In order to understand the reaction between PM_(2.5) and O_3, we construct a box model, in which an aerosol optical property model, ultraviolet radiation model, gas phase chemistry model, and heterogeneous chemistry model,are coupled. The model is employed to investigate the relative contribution of the aforementioned two processes, which vary under different particle concentrations, scattering capability and VOCs/NOxratios(VOCs: volatile organic compounds;NOx: nitric oxide and nitrogen dioxide). Generally, photolysis rate effect can cause a greater O_3 reduction when the particle concentrations are higher, while heterogeneous reactions dominate O_3 reduction with low-level particle concentrations.Moreover, in typical VOC-sensitive regions, O_3 can even be increased by heterogeneous reactions. In Nanjing, both processes lead to O_3 reduction, and photolysis rate effect is dominant. Our study underscores the importance of photolysis rate effect and heterogeneous reactions for O_3, and such interaction processes should be fully considered in future atmospheric chemistry modeling. 相似文献
4.
Enhancements of Major Aerosol Components Due to
Additional HONO Sources in the North China Plain
and Implications for Visibility and Haze 总被引：2，自引：0，他引：2
The Weather Research and Forecasting/Chemistry model(WRF-Chem) was updated by including photoexcited nitrogen dioxide(NO2) molecules,heterogeneous reactions on aerosol surfaces,and direct emissions of nitrous acid(HONO) in the Carbon-Bond Mechanism Z(CBM-Z).Five simulations were conducted to assess the effects of each new component and the three additional HONO sources on concentrations of major chemical components.We calculated percentage changes of major aerosol components and concentration ratios of gas NO y(NOyg) to NO y and particulate nitrates(NO-3) to NO y due to the three additional HONO sources in the North China Plain in August of 2007.Our results indicate that when the three additional HONO sources are included,WRF-Chem can reasonably reproduce the HONO observations.Heterogeneous reactions on aerosol surfaces are a key contributor to concentrations of HONO,nitrates(NO 3),ammonium(NH + 4),and PM 2.5(concentration of particulate matter of 2.5 μm in the ambient air) across the North China Plain.The three additional HONO sources produced a～5%-20% increase in monthly mean daytime concentration ratios of NO-3 /NO y,a ～15%-52% increase in maximum hourly mean concentration ratios of NO-3 /NO y,and a ～10%-50% increase in monthly mean concentrations of NO-3 and NH+4 across large areas of the North China Plain.For the Bohai Bay,the largest hourly increases of NO-3 exceeded 90%,of NH+4 exceeded 80%,and of PM 2.5 exceeded 40%,due to the three additional HONO sources.This implies that the three additional HONO sources can aggravate regional air pollution,further impair visibility,and enhance the incidence of haze in some industrialized regions with high emissions of NO x and particulate matter under favorable meteorological conditions. 相似文献
5.
Urban Atmospheric Chemistry During the PUMA Campaign 2: Radical Budgets for OH,HO<Subscript>2</Subscript> and RO<Subscript>2</Subscript> 总被引：1，自引：0，他引：1
A detailed photochemical box model was used to investigate the key reaction pathways between OH, HO2 and RO2 radicals during the summer and winter PUMA field campaigns in the urban city-centre of Birmingham in the UK. The model employed
the most recent version of the Master Chemical Mechanism and was constrained to 15-minute average measurements of long-lived
species determined in situ at the site. The results showed that in the summer, OH initiation was dominated by the reactions of ozone with alkenes, nitrous
acid (HONO) photolysis and the reaction of excited oxygen atoms atoms with water. In the winter, ozone+alkene reactions were
the primary initiation route, with a minor contribution from HONO photolysis. Photolysis of aldehydes was the main initiation
route for HO2, in both summer and winter. RO2 initiation was dominated by the photolysis of aldehydes in the summer with a smaller contribution from ozone+alkenes, a situation
that was reversed in the winter. At night, ozone+alkene reactions were the main radical source. Termination, under all conditions,
primarily involved reactions with NO (OH) and NO2 (OH and RCO3). These results demonstrate the importance of ozone+alkene reactions in urban atmospheres, particularly when photolysis reactions
were less important during winter and at nighttime. The implications for urban atmospheric chemistry are discussed. 相似文献
6.
A series of indoor air quality parameters were determined in two medieval churches, in Cyprus (temperature, relative humidity,
total and UV solar radiation, CO2 indoors and O3, NO, NO2
*, HNO3
*, HCl, HCOOH, CH3COOH indoors and outdoors). These data were used as input in a validated indoor air quality model to predict indoor air pollutant
source strengths and species concentrations that resulted from dark or photochemical reactions. The NO and NO2 emission rates due to the burning of incense or candles were estimated. Model results revealed that heterogeneous NO formation
takes place simultaneously with the heterogeneous HONO formation. Also, model application has shown that indoor NOx emissions resulted in decreased free radical concentrations, in contrast to the organic compound emissions, which increased
free radical concentrations. This effect of indoor emissions on indoor radicals can partly explain the indoor enhancement/depression
of indoor gaseous acid formation. 相似文献
7.
In view of the uncertainty of the origin of the secular increase of N2O, we studied heterogeneous processes that contribute to formation of N2O in an environment that comes as close as possible to exhaust conditions containing NO and SO2, among other constituents. The N2O formation was followed using electron capture gas chromatography (ECD-GC). The other reactants and intermediates (SO2, NO, NO2 and HONO) were monitored using gas phase UV-VIS absorption spectroscopy. Experiments were conducted at 298 and 368 K as well as at dry and high humidity (approaching 100% rh) conditions. There is a significant heterogeneous rate of N
2
O formation at conditions that mimic an exhaust plume from combustion processes.The simultaneous presence of NO, SO2, O2 in the gas phase and condensed phase water, either in the bulk liquid or adsorbed state has been confirmed to be necessary for the production of significant levels of N2O. The stoichiometry of the overall reaction is: 2 NO+SO2+H2O N2O+H2SO4. The maximum rate of N2O formation occurred at the beginning of the reaction and scales with the surface area of the condensed phase and is independent of its volume. A significant rate of N2O formation at 368 K at 100% rh was also observed in the absence of a bulk substrate. The diffusion of both gas and liquid phase reactants is not rate limiting as the reaction kenetics is dominated by the rate ofN2O formation under the experimental conditions used in this work. The simultaneous presence of high humidity (90–100% rh at 368 K) and bulk condensed phase results in the maximum rate and final yield of N2O approaching 60% and 100% conversion after one hour in the presence of amorphous carbon and fly-ash, respectively.Work performed in partial fulfillment of the requirements of Dr ès Sciences at EPFL. 相似文献
8.
Observations of the Nitrate Radical in the Marine Boundary Layer 总被引：3，自引：0，他引：3
B. J. Allan N. Carslaw H. Coe R. A. Burgess J. M. C. Plane 《Journal of Atmospheric Chemistry》1999,33(2):129-154
A study of the nitrate radical (NO3) has been conducted through a series of campaigns held at the Weybourne Atmospheric Observatory, located on the coast of north Norfolk, England. The NO3 concentration was measured in the lower boundary layer by the technique of differential optical absorption spectroscopy (DOAS). Although the set of observations is limited, seasonal patterns are apparent. In winter, the NO3 concentration in semi-polluted continental air masses was found to be of the order of 10 ppt, with an average turnover lifetime of 2.4 minutes. During summer in clean northerly air flows, the concentration was about 6 ppt with a lifetime of 7.2 minutes. The major loss mechanisms for the radical were investigated in some detail by employing a chemical box model, constrained by a suite of ancillary measurements. The model indicates that during the semi-polluted conditions experienced in winter, the major loss of NO3 occurred indirectly through reactions of N2O5, either in the gas-phase with H2O, or through uptake on aerosols. The most important direct loss was via reactions of NO3 with a number of unsaturated nonmethane hydrocarbons. The cleaner air masses observed during the summer were of marine origin and contained elevated concentrations of dimethyl sulfide (DMS), which provided the major loss route for NO3. The box model was then used to investigate the conditions in the remote marine boundary layer under which DMS will be oxidised more rapidly at night (by NO3) than during the day (by OH). This should occur if the concentration of NO2 is more than about 60% that of DMS. 相似文献
9.
A study on hydrogen peroxide in the atmosphere 总被引：1，自引：0，他引：1
Hydrogen peroxide (H2O2) concentrations were measured at two sites. One was on Lushan Mountain in May, 1987. The other was in Beijing in August, 1987 and in December, 1986. The automated fluorometric method was used for the determination of H2O2. The concentrations of H2O2 ranged from approximately 0.50 to 4.32 ppb on Lushan Mountain. The concentrations of H2O2 ranged from approximately 0.05 to 1.49 ppb in August in Beijing, and it was only 0.01 ppb in December in Beijing. 相似文献
10.
11.
北京奥运会期间NO2浓度降低原因分析 总被引：1，自引：0，他引：1
2002～2008年,北京市城区和近郊8月的NO2月均浓度大体呈现逐年下降趋势,其中前5年二者均以每年约10%的降幅下降,2008年发生显著下降,降幅达40%左右。利用嵌套网格空气质量模式系统(NAQPM/IAP),采用敏感性试验方法,评估了气象条件与污染控制措施对北京奥运会期间大气NO2浓度降低的影响,评估不同污染控制措施对NO2浓度降低的作用。研究结果表明,污染控制措施是NO2浓度降低的主要影响因素,其中面源的污染控制措施对于NO2浓度降低的作用最明显。 相似文献
12.
南京北郊冬季大气SO2、NO2和O3的变化特征 总被引：1，自引：0，他引：1
利用差分吸收光谱仪DOAS（differential optical absorption spectroscopy）,对2007年11月—2008年1月南京北郊大气SO2、NO2和O3进行了观测。结合Parsivel降水粒子谱仪和自动气象站的资料,对冬季大气污染气体的浓度变化规律及降水和风速风向对其的影响进行了分析。结果表明,南京北郊大气SO2浓度较高,呈明显双峰特征,分别在12时（北京时,下同）和00时达最大,受附近排放源的影响最大,东风及南风时比静风时SO2浓度更高。降水对SO2湿清除效果明显,清除系数平均为0.168 h-1。NO2气体呈明显单峰特征,在18时达最高值。南京北郊是NO2源区之一,主要受附近高速公路汽车尾气排放源的影响。静风时NO2浓度最高。O3浓度受NO2的影响较明显。O3日变化呈单峰特征,在15时达最大值,静风时O3浓度最低。降水对O3的间接影响较明显,在降水时,白天由于太阳辐射较弱,O3浓度降低;夜晚NO浓度较低,使得O3浓度升高。 相似文献
13.
中国大气本底条件下不同地区地面臭氧特征 总被引：20，自引：1，他引：20
分析了晴天和阴天时瓦里关本底台、临安和龙凤山本底站地面 O3浓度的特点。晴天时 ,临安站地面 O3有明显日变化 ,以春季最大 (42 .9× 1 0 - 9) ,夏季最小 (2 0 .3× 1 0 - 9) ;龙凤山站日变化更规则 ,秋季最大 (约 2 7× 1 0 - 9) ;瓦里关本底台除了夏季有微弱日变化外 ,其它季节没有明显的日变化 ,日较差也很小 ,但夏季地面 O3浓度显著高於冬季 ;夏季晴天瓦里关地面O3浓度要比龙凤山、临安高 2 0× 1 0 - 9以上。阴天时 ,临安和龙凤山站除了日变化不很规则和日较差较小外 ,其它大致与晴天相同。阴天时瓦里关不仅没有日变化 ,而且日较差更小 ,但夏季地面 O3仍然高於冬季。太阳总辐射和 NOx 浓度是控制龙凤山和临安晴天和阴天地面O3浓度的决定性因子 ,它在不同季节和地区发挥着重要作用。夏季青藏高原周围地区气流向高原输送作用 ,是形成夏季瓦里关地面 O3高值以及微弱日变化的主要原因。在美国 MaunaLoa基准站也曾观测到类似的输送影响。O3在低对流层随垂直高度增加的分布特征 ,决定了东西部测点地面 O3的差异 相似文献
14.
A comprehensive kinetic study of a potential daytime nitrous acid (HONO) source reaction, the photoenhanced reduction reaction of the nitrogen dioxide (NO2) on acidic humic acid (HA), was completed using a wetted-wall flow tube (WWFT) (Fickert et al.: J. Phys. Chem. A. 102, 10689, 1998) photoreactor integrated with a high sensitivity HONO analyser (Wall et al.: J. Atmos. Chem. 55, 31–54, 2006; Huang et al.: Atmos. Environ. 36, 2225–2235, 2002). The nature of this reaction, is of great interest since recently observed, unpredictably high HONO daytime concentrations demand its ordinarily proposed heterogeneous source to proceed 60 times more rapidly at noon than during the night (Kleffmann et al.: ChemPhysChem 8, 1137–1144, 2007). This study investigated the nature of the reduction reaction with simulated colloidal HA aqueous solutions characteristic of anaerobic environmental conditions, varying in acidity, concentration and composition. Typical urban NO2 levels were investigated. Increasing photoenhanced HONO production with weakening solution acidity was detected due to increased deprotonation of the carboxyl groups within the humic acid. It was deduced that the acidic HA substrate contains numerous feasible chromophoric sensitizer units capable of photochemically reducing NO2 to HONO, owing to its ‘biofilm’ (Donlan, 2002) function under UV exposure. The mechanism was found to be more effective for HA standards with higher levels of ‘bioactivity’ (refractivity). Using a complex mathematical model developed, incorporating both chemistry and diffusion, reaction probability datasets were produced from the experimental data, providing evidence that this is, indeed, an environmentally important daytime HONO surface source reaction. The parameters required to scale up the data of the photoreactor to that of a regional rural/urban scale were assessed. 相似文献
15.
利用2003年12月—2005年3月青岛八关山观测资料,分析大气中O3、NOX和CO浓度时间变化规律与影响因素,探讨O3及其主要前体物NOX、CO间复杂的相互作用及相关关系。结果表明:青岛NO2日平均浓度年超标率为25%;受光化学反应及大气运动等影响,NOX与CO浓度为冬季高、夏季低,O3与之相反;NOX与CO浓度日变化呈双峰型分布,日间高于夜间;O3浓度峰值出现于午后(滞后于NOX约5 h),阴雨天夜间浓度出现回升。经滞后相关分析,NOX对O3浓度变化的累积效应作用时间为5—6 h;O3与NO、NO2浓度比值可较明显地验证出辐射强度与尾气排放对青岛及其他地区污染特征的影响。青岛CO与NOX比值在不同天气条件下维持在10.0左右,可用于定性估计其大气污染特征。 相似文献
16.
Using a relative rate method, rate constants have been measured for the gas-phase reactions of OH and NO3 radicals with pinonaldehyde, caronaldehyde and sabinaketone at 296 ± 2 K. The OH radical reaction rate constants obtained are (in units of 10–12 cm3 molecule–1 s–1): pinonaldehyde, 48 ± 8; caronaldehyde, 48 ± 8; and sabinaketone, 5.1 ± 1.4, and the NO3 radical reaction rate constants are (in units of 10–14 cm3 molecule–1 s–1): pinonaldehyde, 2.0 ± 0.9; caronaldehyde, 2.5 ± 1.1; and sabinaketone, 0.036 ± 0.023, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Upper limits to the O3 reaction rate constants were also obtained, of <2 × 10–20 cm3 molecule–1 s–1 for pinonaldehyde and caronaldehyde, and <5 × 10–20 cm3 molecule–1 s–1 for sabinaketone. These reaction rate constants are combined with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals and O3 to calculate tropospheric lifetimes and dominant transformation process(es) of these and other monoterpene reaction products. 相似文献
17.
利用北京地区2006—2015年春节及其前后三周的城区、郊区站数据分析了早晚高峰期出行活动对城市热岛效应、NO_x浓度、PM2.5浓度的影响。结果表明人口、交通、社会活动的密集程度的确会对城市热岛效应和大气污染物浓度造成一定的影响:(1)第-3、-2、+2、+3周(以下称"BG时段")与春节周(以下称"CNY时段")间的城市热岛效应差异在早高峰期间平均为0.30℃,在晚高峰期间平均为0.43℃,在其他时段平均为0.26℃,晚高峰对城市热岛效应的影响更明显;(2)BG时段与CNY时段城、郊NO_x浓度差的最大差异出现在08时,为54.95μg/L。在早高峰期间为48.55μg/L,晚高峰期间为23.44μg/L。城市晚高峰出行活动对NOx浓度城、郊差异的贡献量随着夜间的不利扩散条件而延迟出现峰值,城市早高峰出行对NO_x浓度城、郊差异的增大作用更为突出;(3)城郊PM2.5浓度BG时段高于CNY时段的时间出现在05—19时,早高峰期间平均差值为12.82μg/m3,晚高峰期间平均差值为8.22μg/m3。考虑到汽车尾气中的超细粒子和污染气体需要在空气中进行化学反应或者吸湿增长才能变成PM2.5,因此PM2.5浓度的变化情况并不完全对应于早晚高峰出行的时间,而是有所延迟。 相似文献
18.
The gas-phase degradation of NH3 in the atmosphere still has many uncertainties. One of them is the possible isomerisation of NH2O to NHOH, as indicated by kinetic studies. Since NH2O is formed during the gas-phase oxidation of ammonia in the troposphere, this reaction can potentially influence the subsequent production of N2O and NOx. So far, the isomerisation has never been implemented into current chemical schemes describing the atmospheric gas-phase degradation of NH3 and its atmospheric relevance has never been assessed. The N2O yield from NH3 degradation is calculated to be in the range of 10–43 %. It depends on the NO2 and O3 concentrations, but is independent of the NH3 concentration. Compared with the results from recent literature, the N2O yield derived from the new mechanism is 20–80% lower, implying a smaller global N2O source strength of 0.4 Tg yr- 1. The production of NH2SO2 seems to be less important for the atmospheric degradation of NH3. NH3 oxidation is a sink for NOx at NOx mixing ratios of more than about 1 ppb and a source at lower NOx burdens. 相似文献
19.
Z.-H. Shon G. Lee S.-K. Song M. Lee J. Han D. Lee 《Journal of Atmospheric Chemistry》2007,58(3):203-218
This study examines the general characteristics of reactive nitrogen oxides (NOy) at urban and rural sites in terms of measurement- and modeling-based analyses. In this field study, NOx at urban and rural sites were 92 and 89% of NOy on average, respectively. HONO levels (e.g., 1.8 ppbv) at the urban site were significantly higher than those at the rural
site by a factor of 4.5. HONO concentrations at the urban site during the night were clearly higher than those during the
day, which were likely to result from heterogeneous reactions on the surfaces of airborne aerosols and/or grounds. In contrast,
there were no significant differences of PAN concentrations in either the temporal or spatial distributions. The significantly
low ratios of NOz/NOy at both sampling sites indicated a more limited chemical aging process in air mass. O3 levels were weakly related to NOx oxidation at both sites, especially at the rural site. 相似文献