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1.
为了解我国不同气候背景城市O3污染及其与前体物的关系,选取北京市、沈阳市、银川市、成都市、南京市和广州市作为典型代表城市,基于这6个城市2014-2016年ρ(O3)、ρ(NO2)和ρ(CO)资料对O3与其前体物质量浓度变化特征及二者相关性进行研究.结果表明:①2014-2016年6个城市ρ(O3)年均值大小顺序依次为南京市>沈阳市>北京市>银川市>成都市>广州市,ρ(NO2)年均值大小顺序依次为北京市>成都市>南京市>沈阳市>广州市>银川市,ρ(CO)年均值大小顺序依次为北京市>银川市>成都市>沈阳市>南京市>广州市.2014-2016年除广州市ρ(O3)下降、沈阳市变化不明显外,其他城市ρ(O3)总体呈上升趋势;各城市ρ(NO2)和ρ(CO)普遍呈下降趋势.②广州市ρ(O3)夏季最高、春季最低,其他城市四季ρ(O3)大小顺序依次为夏季>春季>秋季>冬季;北京市、沈阳市和银川市四季ρ(NO2)和ρ(CO)大小顺序依次为冬季>秋季>春季>夏季,成都市、广州市和南京市为冬季>春季>秋季>夏季.各城市ρ(O3)和ρ(Ox)日变化呈单峰型,ρ(NO2)和ρ(CO)日变化呈双峰型.③6个城市城区ρ(O3)均低于清洁对照点,城区ρ(NO2)和ρ(CO)均高于清洁对照点,并且城区与清洁对照点O3及其前体物质量浓度差值随城市和月份变化存在一定的差异.④各城市ρ(O3)与ρ(NO2)和ρ(CO)均呈负相关,与ρ(Ox)呈显著正相关;城区ρ(O3)与ρ(NO2)和ρ(CO)的相关性均好于清洁对照点,清洁对照点ρ(O3)与ρ(Ox)的相关性则好于城区.⑤各城市ρ(O3)超标率随ρ(NO2)和ρ(CO)的增加均呈先迅速上升再快速减小,之后缓慢变化的特征,但ρ(O3)超标率峰值对应的ρ(NO2)和ρ(CO)有所差异.研究显示,日照条件较好的银川市、北京市和沈阳市O3与其前体物相关性较成都市、南京市和广州市强.   相似文献   

2.
A series of 24 chemical mechanisms from the literature are compared against each other using harmonized emissions, photolysis rate coefficients for simple inorganic chemistry and life cycle data for ozone, PAN and H2O2. The evaluation sought to understand the impact of parameterizing hydrocarbon oxidation on the peak concentrations of photochemically-generated secondary pollutants. Only seven of the 24 chemical mechanisms gave peak concentrations of ozone, PAN and H2O2 simultaneously in their respective central ranges. PAN and H2O2 were generally calculated with a much lower precision compared to ozone. Only 11 mechanisms out of 24 gave responses to both 50% hydrocarbons and NOx emissions controls in their respective central bands. The lack of coordinated ozone, PAN and hydrogen peroxide measurements across Europe currently limits the adequacy of model comparisons and hence the confidence which may be placed in assessments of likely impacts of future control strategies.  相似文献   

3.
北京大气中NO、NO2和O3浓度变化的相关性分析   总被引:26,自引:8,他引:18  
臭氧(O3)是城市污染大气中的首要光化学污染物,其变化规律与氮氧化物(NOx=NO+NO2)关系密切.采用49C臭氧分析仪和42CTL氮氧化物分析仪对北京城区O3和NOx浓度进行了连续观测,时间为2004-08~2005-07.结果显示,O3和OX(O3+NO2)浓度在午后15:00左右出现峰值,NOx呈双峰态日变化,在07:00和23:00左右出现峰值.不同季节污染物的浓度变化存在差异,O3和NOx浓度分别在夏季和冬季达到最大.NOx浓度存在100×10-9(体积分数)的“分界点”,NOx低浓度时以NO2为主,NOx高浓度时NO占大部分.OX区域贡献和局地贡献存在明显的季节变化,前者主要受区域背景O3的影响,在春季最大,后者主要受局地NOx光化学反应的制约,在夏季最强,同时OX组分呈现显著的昼夜差异.  相似文献   

4.
北京城区夏季O3化学生成过程   总被引:3,自引:2,他引:1  
选取2007年7月1日—8月31日中的21个晴空日,利用观测资料和光化学箱模式计算了北京城区测点的O3生成速率G(O3)和O3生成效率OPE.结果表明,21个晴空日中G(O3)日最高小时值分布在(18~82)×10-9h-1之间;在O3污染和非污染日G(O3)最高值的平均水平无显著差异,且与Ox浓度之间不存在一致的对应关系,表明O3化学生成过程不能全面解释地面O3浓度的累积,物理传输过程对测点O3实测浓度有显著作用;各个化学过程对G(O3)的贡献率对比结果显示,HO2 在 NO向NO2的转化中贡献最大;OPE值分布在2.8~5.8之间,总体水平为4.1±0.1;OPE值与NOx浓度之间为非线性关系,OPE值随NOx浓度的增加而减少,表明消减测点附近VOCs排放能有效降低O3浓度.  相似文献   

5.
2020年8月利用化学放大法对合肥市西郊大气总过氧自由基RO*2·(RO2·+HO2·)体积分数进行监测,并结合O3和其前体物,分析了过氧自由基体积分数、O3生成速率和O3生成对前体物的敏感性.结果表明,观测期间总过氧自由基体积分数的日均值呈典型的单峰型变化,12:00左右出现最高值,日间峰值体积分数为43.8×10-12,日间RO*2·与太阳辐射强度、温度和O3呈明显的相关性.利用实测RO*2·和NO,获得合肥市西郊夏季O3生成速率,日间峰值为10.6×10-9h-1,O3生成速率对NO变化更为敏感.基于大气自由基和NOx(NO+NO2)反应去除速率占比(Ln/Q),对合肥...  相似文献   

6.
夏季城市大气O3浓度影响因素及其相关关系   总被引:22,自引:3,他引:19  
利用2003年夏季济南市区近地面大气O3、相关前体物和气象因素等观测数据,研究了O3浓度的分布特征及时间变化规律,分析了7月份O3与NO、NO2和CO等前体物及太阳辐射和气温气象条件的相关性.结果表明,济南市区夏季O3污染比较严重,观测期间各污染物O3、NO、NO2、NOx和CO浓度都相对较高,昼间O3与各前体物的浓度呈较好的负相关关系,与太阳辐射具有非常明显的相关性,而与气温的相关性不明显.根据以上分析结果,利用回归分析方法,建立了昼间O3浓度与前体物、气象因子之间的相关模式,结果表明O3浓度的计算值与观测值符合性较好.  相似文献   

7.
Wet scrubbing combined with ozone oxidation has become a promising technology for simultaneous removal of SO2 and NOx in exhaust gas. In this paper, a new 20-species, 76-step detailed kinetic mechanism was proposed between O3 and NOx. The concentration of N2O5 was measured using an in-situ IR spectrometer. The numerical evaluation results kept good pace with both the public experiment results and our experiment results. Key reaction parameters for the generation of NO2 and N2O5 during the NO ozonation process were investigated by a numerical simulation method. The effect of temperature on producing NO2 was found to be negligible. To produce NO2, the optimal residence time was 1.25 sec and the molar ratio of O3/NO about 1. For the generation of N2O5, the residence time should be about 8 sec while the temperature of the exhaust gas should be strictly controlled and the molar ratio of O3/NO about 1.75. This study provided detailed investigations on the reaction parameters of ozonation of NOx by a numerical simulation method, and the results obtained should be helpful for the design and optimization of ozone oxidation combined with the wet flue gas desulfurization methods (WFGD) method for the removal of NOx.  相似文献   

8.
上海市浦东城区二次气溶胶生成的估算   总被引:1,自引:5,他引:1  
利用2010年5~10月不同日最高O3小时浓度(O3,max)下PM10浓度变化评估不同O3浓度水平下二次气溶胶生成量.CO作为一次颗粒物的标志物,O3作为光化学反应水平的指示物种.结果表明不同光化学水平条件下,PM10中一次与二次气溶胶浓度及比例存在较大差异.随着光化学水平的增加,PM10中一次气溶胶排放浓度增长不大(0.036~0.044 mg.m-3),二次气溶胶的生成量却呈数倍增长(0.018~0.055 mg.m-3);二次与一次气溶胶浓度的比例也从49.8%增加到124.5%.O3,max出现的时间也随着光化学水平的增强由13:00推迟到14:00,二次气溶胶生成的主要时段也从11:00~20:00增加到09:00~20:00;此外,PM2.5中主要组分SO24-、NO3-、OC等比例随着光化学水平(即O3,max浓度)的不同而存在一定差异,当O3,max<0.10 mg.m-3时,PM2.5主要由12.0%有机碳(OC)、18.7%硫酸盐、13.1%硝酸盐和4.5%元素碳(EC)组成,而O3,max>0.20mg.m-3时,PM2.5主要由20.0%有机碳(OC)、22.9%硫酸盐、23.1%硝酸盐和4.7%元素碳(EC)组成.说明SO24-、NO3-、OC受光化学水平影响较大.  相似文献   

9.
济南大气臭氧浓度变化规律   总被引:15,自引:3,他引:12  
殷永泉  单文坡  纪霞  由丽娜  苏元成 《环境科学》2006,27(11):2299-2302
利用近2a济南市区近地面大气O3浓度的观测数据,分析了O3浓度的分布特征及时间变化规律.结果表明,济南市区O3浓度以1a为周期呈明显的波动变化特征,城市光化学污染较重;1d当中O3浓度呈明显的单峰型变化,一般在午后达到最高值,而日出时分出现最低值;春季和夏季O3浓度高于秋季和冬季,而夏季和秋季O3浓度的日内变化幅度明显高于春季和冬季;受人们活动规律的影响,周末O3浓度的日内变化规律与平日有所不同.  相似文献   

10.
Based on observational data of ozone(O3) and nitrogen oxide(NOx) mixing ratios on the ground and at high altitude in urban areas of Beijing during a period of six days in November 2011,the temporal and spatial characteristics of mixing ratios were analyzed.The major findings include:urban O3 mixing ratios are low and NOx mixing ratios are always high near the road in November.Vertical variations of the gases are significantly different in and above the planetary boundary layer.The mixing ratio of O3 is negatively correlated with that of NOx and they are positively correlated with air temperature,which is the main factor directly causing vertical variation of O3 and NOx mixing ratios at 600-2100m altitude.The NOx mixing ratios elevated during the heating period,while the O3 mixing ratios decreased:these phenomena are more significant at high altitudes compared to lower altitudes.During November,air masses in the urban areas of Beijing are brought by northwesterly winds,which transport O3 and NOx at low mixing ratios.Due to Beijing’s natural geographical location,northwest air currents are beneficial to the dilution and dispersion of pollutants,which can result in lower O3 and NOx background values in the Beijing urban area.  相似文献   

11.
During the summer portion of the 1987 Southern California Air Quality Study (SCAQS), outdoor smog chamber experiments were performed on Los Angeles air to determine the response of maximum ozone levels, O3(max), to changes in the initial concentrations of hydrocarbons, HC, and nitrogen oxides, NOx. These captive-air experiments were conducted in downtown Los Angeles and in the downwind suburb of Claremont. Typically, eight chambers were filled with LA air in the morning. In some chambers the initial HC and/or NOx concentrations were changed by 25% to 50% by adding various combinations of a mixture of HC, clean air, or NOx. The O3 concentration in each chamber was monitored throughout the day to determine O3(max).An empirical mathematical model for O3(max) was developed from regression fits to the initial HC and NOx concentrations and to the average daily temperature at both sites. This is the first time that a mathematical expression for the O3-precursor relationship and the positive effect of temperature on O3(max) have been quantified using captive-air experiments. An ozone isopleth diagram prepared from the empirical model was qualitatively similar to those prepared from photochemical mechanisms. This constitutes the first solely empirical corroboration of the O3 contour shape for Los Angeles.To comply with the Federal Ozone Standard in LA, O3(max) must be reduced by approximately 50%. Several strategies for reducing O3(max) by 50% were evaluated using the empirical model. For the average initial conditions that we measured in LA, the most efficient strategy is one that reduces HC by 55–75%, depending on the ambient HC/NOx ratio. Any accompanying reduction in NOx would be counter-productive to the benefits of HC reductions. In fact, reducing HC and NOx simultaneously requires larger percentage reductions for both than the reduction required when HC alone is reduced. The HC-reduction strategy is the most efficient on average, but no single strategy is the optimum every day.  相似文献   

12.
Seasonal averaged ground level concentrations for O3 have been calculated for The Netherlands by means of a two-layer Lagrangian long-range transport (LRT) model. The model includes emissions, nonlinear atmospheric chemistry, dry deposition, exchange between boundary layer (BL) and free troposphere (FT) and fumigation between a mixed layer and an aged smog layer. Concentrations of primary and secondary pollutants in the FT are obtained from a two-dimensional global model developed by Isaksen.In the reference calculation the modelled concentrations of Ox (sum of O3 and NO2) and O3 are in fair agreement with measurements. The NOx (sum of NO and NO2) and NO2 concentrations are under-estimated by the model but there is a good temporal correlation between calculated and measured concentrations. Validation of other components involved in the chemical scheme is hardly possible due to the paucity of measured data. It can only be stated that the results presented in this paper are not in disagreement with measured or modelled data presented in the literature.In a number of sensitivity runs the influence of European anthropogenic emissions of NOx and volatile organic compounds (VOC) has been investigated. The calculations indicate that the influence of European emissions on the growing season, daytime averaged (May–September, 10–17 h) O3 concentrations in The Netherlands is small. For European reductions in the order of tens of per cents a VOC emission reduction is more effective than a NOx emission reduction in lowering the O3 concentrations. For strong reductions (about 70%) VOC and NOx are equally effective. The effects of the modelled underprediction of NOx concentrations on the production of O3 on a European scale are probably small. On a local scale the effects are more pronounced due to the NO/O3 titration (photostationary equilibrium). Therefore, an empirical correction is applied on the modelled O3 concentrations. After this correction, it is shown that daytime O3 levels during the growing season increase when European NOx emissions are reduced (2.0–7.7.% increase at 50% NOx emission reduction). A reduction in VOC emission leads to decreasing O3 levels (9% reduction for 40% VOC emission reduction, 16% reduction for 70% VOC emission reduction). For a combined reduction of both VOC and NOx slightly decreasing ground level O3 concentrations are expected.  相似文献   

13.
Outdoor smog chamber experiments were used to study the sensitivity of the yields of two important nitrogen-containing pollutants, nitric acid (HNO3) and peroxyacetyl nitrate (PAN) to changes in nonmethane hydrocarbon (HC) and nitrogen oxide (NOx) concentrations in Los Angeles. The experiments were conducted at two sites in the Los Angeles Basin using eight chambers filled with morning Los Angeles air on 33 days. At least one chamber was unchanged and served as a control, while the initial HC and/or NOx concentrations were changed by 25–50% in up to seven chambers to simulate O3 control strategies and to broaden the range of HC - NOx conditions studied. Empirical models that predict the maximum yields of HNO3 and PAN were used to determine the response of these pollutants to three possible ozone control strategies. All three strategies (reductions in HC, NOx or both HC and NOx) reduced PAN while only NOx reductions decreased HNO3. However, reducing NOx increased the HC reductions required to attain lower O3 levels. Thus, there is a conflict between the O3 and HNO3 control strategies.  相似文献   

14.
Following the Council Directive 92/72/EEC on air pollution by ozone the Member States of the European Union have to inform the European Commission on ozone concentrations and exceedances of threshold values within their territory. Using the available information covering the period of 5 years (1994–1998), the data has been analysed for a possible trend in statistical parameters (50- and 98-percentiles) and number and severity of exceedances. Time series are relatively short but the data suggest that there might be a small increasing trend in the 50 percentile values. The ozone peak values, expressed as 98-percentile values or as number of exceedance days tend to decrease. However, these conclusions must be interpreted carefully as on the short time scales considered here meteorological variations and inter-annual changes may play an important role. The decrease in peak values is most likely caused by the decrease in European ozone precursor emissions since 1990; insufficient data is available to explain the increasing 50-percentile values. Possible explanations are an increase in tropospheric ozone background values caused by a world-wide increase in CH4, CO and NOx emissions or a reduced ozone titration by reduced NOx emissions on the local scale. The data submitted under the ozone directive is insufficient to provide firm conclusions on this point.  相似文献   

15.
烟雾箱与数值模拟研究苯和乙苯的臭氧生成潜势   总被引:1,自引:0,他引:1  
贾龙  徐永福 《环境科学》2014,35(2):495-503
结合光化学烟雾箱实验与数值模拟研究了苯和乙苯在NO x存在条件下的光氧化臭氧生成潜势.重复实验表明,在乙苯-NO x反应体系中,反应物初始浓度、温度、湿度和光照强度接近的条件下,整个反应过程中臭氧的最大偏差仅为4%,证明了烟雾箱的可重复性较高.在烟雾箱实验的基础上,使用MCM(master chemical mechanism)模拟了苯和乙苯的光氧化O3生成,并将其结果与实验数据进行了比对分析.干燥(≤5%)时MCM对苯和乙苯的模拟结果与实验结果较接近,如在苯-NO x反应体系中,MCM模拟的O3峰值比实验值偏大20%;在湿度为5%~70%时,MCM模拟的乙苯光氧化O3峰值与实验值偏高约(10%~25%).用MCM模拟了太阳光照条件下苯和乙苯的臭氧生成等值线,得到在它们浓度为(10~50)×10-9,NO x在(10~100)×10-9时,苯和乙苯的6 h臭氧贡献值分别为(3.1~33)×10-9和(2.6~122)×10-9,臭氧峰值范围分别是(3.5~54)×10-9和(3.8~164)×10-9.此外,模拟得到苯和乙苯的最大增量反应活性(maximum incremental reactivity,MIR)值分别为0.25/C和0.97/C(每单位碳).该结果与Carter通过SAPRC机制得到的MIR值趋势一致.模拟得到苯和乙苯的最大臭氧反应活性(maximum ozone reactivity,MOR)分别为0.73/C和1.03/C.苯的MOR值远高于Carter使用SAPRC得到的结果,说明根据Carter得到的苯MOR会低估苯的O3潜势.  相似文献   

16.
臭氧污染动态源贡献分析方法及应用初探   总被引:2,自引:1,他引:1  
论文创新提出了基于RSM/CMAQ臭氧污染动态源贡献分析方法,并以佛山市顺德区2014年10月为例,分析了不同区域的人为可控源NO_x和VOCs减排情景下(10%、70%和100%)对本地O_3浓度变化的量化贡献.研究结果表明顺德区O_3的人为可控比例约43%,且受区域排放影响非常明显,主导上风向广州排放源总贡献(14%)超过顺德本地贡献(7%).VOCs的减排可有效削减顺德区O_3浓度,当减排力度较小时(12%),若仅控制区域NO_x排放将导致顺德区O_3浓度上升,随着减排力度的加大,区域NO_x的削减贡献会反超VOCs.RSM/CMAQ动态源贡献分析方法可为空气质量管理提供科学决策依据.  相似文献   

17.
王晓彦  王帅  朱莉莉  许荣  李健军 《环境科学》2018,39(10):4422-4429
对北京、保定、石家庄、邢台和邯郸这5个京津冀太行山沿山城市2014~2016年空气质量首要污染物进行分析,探讨其空间分布特征和时间变化趋势.结果表明,北京首要污染物由主到次为PM2.5、O3-8h、NO2和PM10,其他4个城市首要污染物排序为PM2.5、PM10、O3-8h、NO2、SO2和CO.在空间分布上,各城市PM2.5首要污染物天数比例3 a均值相当(53.3%~58.1%),但从北向南,5个城市PM10天数比例基本呈上升趋势,而O3-8h反之.除邯郸PM2.5首要污染物天数比例逐年明显下降外,其他4个城市的天数比例年际变化幅度较小;2016年石家庄、邢台和邯郸O3-8h天数比例均显著上升.各城市PM2.5和O3-8h首要污染物天数月变化曲线分别呈"W"型和"倒U"型,PM10首要污染物天数在3~5月出现明显高值区.从良至严重污染,各城市PM2.5和PM10首要污染物天数比例之和随空气质量级别逐级递增,其中PM10天数比例逐级下降,而PM2.5表现相反;O3-8h首要污染物天基本出现在良至中度污染级别,且总体上逐级下降;NO2仅在良级天有较高的天数比例贡献.  相似文献   

18.
Because of the recent growth in ground-level ozone and increased emission of volatile organic compounds (VOCs), VOC emission control has become a major concern in China. In response, emission caps to control VOC have been stipulated in recent policies, but few of them were constrained by the co-control target of PM2.5 and ozone, and discussed the factor that influence the emission cap formulation. Herein, we proposed a framework for quantification of VOC emission caps constrained by targets for PM2.5 and ozone via a new response surface modeling (RSM) technique, achieving 50% computational cost savings of the quantification. In the Pearl River Delta (PRD) region, the VOC emission caps constrained by air quality targets varied greatly with the NOx emission reduction level. If control measures in the surrounding areas of the PRD region were not considered, there could be two feasible strategies for VOC emission caps to meet air quality targets (160 µg/m3 for the maximum 8-hr-average 90th-percentile (MDA8-90%) ozone and 25 µg/m3 for the annual average of PM2.5): a moderate VOC emission cap with <20% NOx emission reductions or a notable VOC emission cap with >60% NOx emission reductions. If the ozone concentration target were reduced to 155 µg/m3, deep NOx emission reductions is the only feasible ozone control measure in PRD. Optimization of seasonal VOC emission caps based on the Monte Carlo simulation could allow us to gain higher ozone benefits or greater VOC emission reductions. If VOC emissions were further reduced in autumn, MDA8-90% ozone could be lowered by 0.3-1.5 µg/m3, equaling the ozone benefits of 10% VOC emission reduction measures. The method for VOC emission cap quantification and optimization proposed in this study could provide scientific guidance for coordinated control of regional PM2.5 and O3 pollution in China.  相似文献   

19.
北京夏季道路环境中NO_x,NMHCs及气象因子对ρ(O_3)的影响   总被引:1,自引:0,他引:1  
通过对北京市2009年夏季3种典型道路(开阔道路、交叉道路、街道峡谷)环境中O3,O3前体物(NO,NMHCs等)及气象因子的监测,分析了北京市典型道路环境中ρ(O3)的变化规律及O3前体物质量浓度与气象因子对ρ(O3)的影响.结果表明:夏季北京市典型道路环境中ρ(O3)呈明显的日间单峰变化规律,这与非道路环境并无不同.不同类型道路环境中ρ(O3)的变幅与峰值出现时间有所不同;3种典型道路环境中ρ(O3)与ρ(NO),ρ(NMHCs)等均呈良好的负相关关系,与ρ(NO2),ρ(NO2)/ρ(NO)呈良好的正相关关系;3种类型道路环境中ρ(O3)均呈现出与紫外强度、温度相同的变化趋势,而与相对湿度的变化趋势相反,ρ(O)高值出现于高温、强紫外线与低湿度的时刻,ρ(O)变化略滞后于紫外强度变化.  相似文献   

20.
Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.  相似文献   

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