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1.
In this study, we used satellite data (GOME and MOPITT) together with a global chemical-transport-model of atmosphere (MOZART-2) to characterize the chemical/aerosol composition over eastern China. We then estimated the effects of local emissions in China on the chemical budgets in other regions of the world. Likewise, we also investigated the effects of air pollution from other regions on the chemical budget over eastern China. The study shows that the column CO and NO x concentrations are also high in eastern China. The high CO and NO x concentrations produce modest levels of O3 concentrations during summer (about 40 to 50 ppbv) and very low O3 during winter (about 10 to 20 ppbv) in eastern China. The calculated NO2 column is fairly consistent from the GOME measurement. The calculated CO column is underestimated from the MOPITT measurement. One of the reasons of the underestimation of the predicted CO is due to a fact that the CO emissions were taken without considering the rapid increase of emissions from 1990 to 2000. The calculated surface O3 is consistent with the measured values, with strong seasonal variations. However, the measurement is very limited, and more measurements in eastern China will be needed. The column NO2 has a very strong seasonal variation in eastern China, with the highest concentrations during winter and the lowest concentrations during summer. The cause of this seasonal variability is mainly due to the seasonal changes in the chemical loss of NO x , which is very high in summer and very low during winter. The effects of the local emissions in China and long-range transport from other regions on the chemical distributions in eastern China are studied. The results show that NO x concentrations in eastern China are mostly caused by the local emissions in China, especially during the winter. The CO concentration over eastern China is from both the local emissions (30% to 40%) and the transport from other regions. Likewise, the CO emissions in China have an important effect on the other regions of the world, but the effect is limited in the northern hemisphere. The local emissions in China also have an important effect on surface O3 concentrations. During winter, the local emissions reduce the surface O3 concentrations by 30 to 50%. During summer, the local emissions produce about 50 to 70% of the O3 concentration in eastern China.  相似文献   

2.
Continuous in-situ measurements of surface ozone (O3), carbon monoxide (CO) and oxides of nitrogen (NOx) were conducted at Udaipur city in India during April 2010 to March 2011. We have analyzed the data to investigate both diurnal and seasonal variations in the mixing ratios of trace gases. The diurnal distribution of O3 showed highest values in the afternoon hours and lower values from evening till early morning. The mixing ratios of CO and NOx showed a sharp peak in the morning hours but lowest in the afternoon hours. The daily mean data of O3, CO and NOx varied in the ranges of 5–51 ppbv, 145–795 ppbv and 3–25 ppbv, respectively. The mixing ratios of O3 were highest of 28 ppbv and lowest 19 ppbv during the pre-monsoon and monsoon seasons, respectively. While the mixing ratios of both CO and NOx showed highest and lowest values during the winter and monsoon seasons, respectively. The diurnal pattern of O3 is mainly controlled by the variations in photochemistry and planetary boundary layer (PBL) depth. On the other hand, the seasonality of O3, CO and NOx were governed by the long-range transport associated mainly with the summer and winter monsoon circulations over the Indian subcontinent. The back trajectory data indicate that the seasonal variations in trace gases were caused mainly by the shift in long-range transport pattern. In monsoon season, flow of marine air and negligible presence of biomass burning in India resulted in lowest O3, CO and NOx values. The mixing ratios of CO and NOx show tight correlations during winter and pre-monsoon seasons, while poor correlation in the monsoon season. The emission ratio of ?CO/?NOx showed large seasonal variability but values were lower than those measured over the Indo Gangetic Plains (IGP). The mixing ratios of CO and NOx decreased with the increase in wind speed, while O3 tended to increase with the wind speed. Effects of other meteorological parameters in the distributions of trace gases were also noticed.  相似文献   

3.
Automobile exhaust emissions are becoming increasingly serious with the drastic increase of the number of vehicles in Beijing. In order to investigate the air pollution level and characteristics in the areas near the main traffic lines in Beijing and to identify the contributions from traffic and other sources, gaseous pollutants including NOx, CO, O3, SO2, and meteorological parameters have been monitored at a monitoring site and a contrasting site in winter and summer in 2006. The volumes of vehicles on Beiyuan Road were recorded. The average concentrations of NO, NO2, NOx, CO, O3, and SO2 at the monitoring site were 0.148 mg/m3, 0.107 mg/m3, 0.333 mg/m3, 5.110 mg/m3, 0.006 mg/m3, and 0.157 mg/m3, respectively during the sampling period in winter and 0.021 mg/m3, 0.068 mg/m3, 0.101 mg/m3, 4.170 mg/m3, 0.083 mg/m3, and 0.056 mg/m3, respectively in summer. The high concentrations of CO and O3 reflect the influence of vehicles emission near the traffic lines evidently. The higher concentrations of CO, NO and O3 in summer may indicate that the characteristics of traffic pollution were more pronounced in summer. Results of regression analysis showed that in winter the concentrations of SO2 and CO were significantly positively correlated with the emission of heating boilers at night and negatively correlated with wind speed in daytime. The concentrations of NO and NOx were negatively correlated with wind speed, positively correlated with emission of heating boilers in daytime and positively correlated with traffic density at nighttime. The concentrations of NO2 were positively correlated with the emission of heating boilers in daytime and traffic density at nighttime. In summer, the air quality at the monitoring site and the contrasting site was mainly influenced by the traffic emissions.  相似文献   

4.
Continuous measurements of surface ozone (O3), NOx (NO + NO2) and meteorological parameters have been made in Kannur (11.9?°N, 75.4?°E, 5?m asl), India from November 2009 to October 2010. It was observed that O3 and NOx showed distinct diurnal and seasonal variabilities at this site. The annual average diurnal profile of O3 showed a peak of (30.3?±?10.4) ppbv in the late afternoon and a minimum of (3.2?±?0.7) ppbv in the early morning. The maximum value of O3 mixing ratio was observed in winter (44?±?3.1) ppbv and minimum during monsoon (18.46?±?3.5) ppbv. The rate of production of O3 was found to be higher in December (10.1?ppbv/h) and lower in July (1.8?ppbv/h) during the time interval 0800?C1000?h. A correlation coefficient of 0.52 for the relationship between O3 and [NO2]/[NO] reveals the role of NO2 photolysis that generates O3 at this site. The correlation between O3 and meteorological parameters indicate the influence of seasonal changes on O3 production. Investigations were further extended to explore the week day weekend variations in O3 mixing ratio at an urban site reveals the enhancement of O3. The variations of O3 mixing ratio with seasonal air mass flows were elucidated with the aid of backward air trajectories. This study also indicates how vapor phase organic species present in the ambient air at this location may influence the complex chemistry involving (VOCs) that enhances the production of O3 at this location.  相似文献   

5.
Surface ozone (O3) and fine particulate matter (PM2.5) are dominant air pollutants in China. Concentrations of these pollutants can show significant differences between urban and nonurban areas. However, such contrast has never been explored on the country level. This study investigates the spatiotemporal characteristics of urban-to-suburban and urban-to-background difference for O3 (Δ[O3]) and PM2.5 (Δ[PM2.5]) concentrations in China using monitoring data from 1171 urban, 110 suburban, and 15 background sites built by the China National Environmental Monitoring Center (CNEMC). On the annual mean basis, the urban-to-suburban Δ[O3] is ?3.7 ppbv in Beijing–Tianjin–Hebei, 1.0 ppbv in the Yangtze River Delta, ?3.5 ppbv in the Pearl River Delta, and ?3.8 ppbv in the Sichuan Basin. On the contrary, the urban-to-suburban Δ[PM2.5] is 15.8, ?0.3, 3.5 and 2.4 μg m?3 in those areas, respectively. The urban-to-suburban contrast is more significant in winter for both Δ[O3] and Δ[PM2.5]. In eastern China, urban-to-background differences are also moderate during summer, with ?5.1 to 6.8 ppbv for Δ[O3] and ?0.1 to 22.5 μg m?3 for Δ[PM2.5]. However, such contrasts are much larger in winter, with ?22.2 to 5.5 ppbv for Δ[O3] and 3.1 to 82.3 μg m?3 for Δ[PM2.5]. Since the urban region accounts for only 2% of the whole country’s area, the urban-dominant air quality data from the CNEMC network may overestimate winter [PM2.5] but underestimate winter [O3] over the vast domain of China. The study suggests that the CNEMC monitoring data should be used with caution for evaluating chemical models and assessing ecosystem health, which require more data outside urban areas.  相似文献   

6.
Modeling tropospheric ozone formation over East China in springtime   总被引：1，自引：0，他引：1  
In this study, we investigate the springtime O3 formation over East China (April 2008) using the Weather Research and Forecasting Model with Chemistry (WRF/Chem). A simple process analysis scheme is added to WRF/Chem, which could calculate the contributions of photochemical and physical processes to O3 formation. WRF/Chem calculates the hourly 3-D O3 mixing ratios, photochemical O3 production rates (CPR) and physical processes contribution rates (PCR) on a two nested domain system, with inner domain focusing on East China. Model evaluation shows that the modeled results agree relatively well with the observations. On the ground level, the high O3 mixing ratios (>45 ppbv) are located over Fujian and Jiangxi provinces. The O3 levels over the Yangtze River Delta (YRD) and northern Jiangsu are low (<30 ppbv). The distribution patterns of CPR and PCR over East China reveal that the high O3 mixing ratios over Jiangxi and Fujian are caused by both local photochemical generation and regional transport, while the O3 concentrations over the YRD region are transported and diffused from surrounding areas. In addition, the contributions of biogenic and anthropogenic emissions as well as the regional transport from domain’s upstream regions are discussed. On average, the biogenic and anthropogenic emissions account for 2.6 and 4.5 ppbv of daytime mean O3 mixing ratios in East China, respectively.  相似文献   

7.
The manual harvest of sugar cane requires the burning of its foliage. This burning has strongly increased in Brazil after the National Alcohol Program was started which substituted automobile gasoline engines for alcohol engines. Presently, the source strength per unit area of this rural pollution is comparable to the well-known biomass burning source in Amazonia. The observed concentrations of CO and O3 in the rural area of the state of São Paulo during the 1988 burning season were twice as large as those reported from an aircraft experiment of 1985 for biomass burnings of the tropical rain forest. Results are reported from airplane measurements and from three fixed ground stations. Mixing ratios of ozone and carbon monoxide in the height range below 6 km are normally less than 40 and 100 ppbv, (parts per billion by volume), respectively, in the absence of burnings. A strong O3 and CO layer was observed during the burning period with peak concentrations of 80 ppbv of ozone and 580 ppbv of CO at about 2 km. The concentrations of CH4 and CO2 were also large, 1756 ppbv and 409 ppmv, respectively, at 1500 m. During the dry season period of the experiment, the ground based O3 average diurnal variations obtained at the rural sites were practically identical to the typical urban variation observed at São José dos Campos, with daytime ozone values between 45 and 60 ppbv. A second three-day airplane excursion to the surgar cane fields in the wet season of 1989 has produces results to be contrasted with the dry (burning) season of 1988 and 1989. Carbon monoxide concentrations were below 100 ppbv at all heights and ozone concentrations were around 30–40 ppbv. The maximum daytime concentrations at the ground station Bauru was 25 ppbv of O3, and at Jaboticabal it was 35 ppbv of O3, only one half of what was observed in the dry season.Universidade Estadual de São Paulo.  相似文献   

8.
气候变化引起的地面气溶胶浓度变化与区域空气质量密切相关。本文利用“国际大气化学—气候模式比较计划”（Atmospheric Chemistry and Climate Model Intercomparison Project, ACCMIP）中4个模式的试验数据分析了RCP8.5情景下2000~2100年气候变化对中国气溶胶浓度的影响。结果显示,在人为气溶胶排放固定在2000年、仅考虑气候变化的影响时,2000~2100年气候变化导致中国北部地区（31°N~45°N, 105°E~122°E）硫酸盐、有机碳和黑碳气溶胶分别增加28%、21%和9%,硝酸盐气溶胶在中国东部地区减少30%。气候变化对细颗粒物（PM2.5）浓度的影响有显著的季节变化特征,冬季PM2.5浓度在中国东部减少15%,这主要是由硝酸盐气溶胶在冬季的显著减少造成的;夏季PM2.5浓度在中国北部地区增加16%,而长江以南地区减少为9%,这可能与模式模拟的未来东亚夏季风环流的增强有关。  相似文献   

9.
During a 3-year study, gaseous hydrogenperoxide (H2O2) concentrations were measuredas part of the SANA project at the Melpitz FieldResearch Station and in the city of Leipzig. Typicaldaily mean H2O2 mixing ratios on sunny dayswere 0.15 to 0.25 ppbv with maximum values of 0.3 to0.5 ppbv at Melpitz, and 0.3 to 0.6 ppbv with maximumvalues of 0.4 to 1.0 ppbv in Leipzig. Over the entireperiod of the project the maximum hourly mean valueswere 2.1 ppbv and 5.3 ppbv in Melpitz and Leipzig,respectively. The data were not complete enough to show a trend.Linear regression analysis shows, that ozone(O3), temperature and solar radiation arepositively correlated with H2O2, whereasnitrogen oxides (NOx), carbon monoxide (CO) andrelative humidity are negatively correlated. Negativecorrelation between H2O2 and CO is caused byjoint occurrence of CO with NOx in exhaust gases.Negative correlation between H2O2 andrelative humidity is not necessarily in contradictionto the accelerating effect of water vapour onH2O2 formation. The strong positivecorrelation of H2O2 with the dew pointdifference however seems to better reflect theinfluence of water vapour. Multiple linear regression analysis (MLRA) of thecomponents measured, indicates the great influence of CO on the formation of H2O2 in the gasphase.  相似文献   

10.
The impacts of emissions from industry,power plant,transportation,residential,and biogenic sources on daily maximum surface ozone （O3DM） over the Beijing-Tianjin-Hebei （BTH） region in North China in the summer of 2007 were examined in a modeling study.The modeling system consisted of the Weather Research and Forecasting （WRF） model and the photochemical dispersion model,CAMx.The factor separation technique （FST） was used to quantify the effect of individual emission source types and the synergistic interactions among two or more types.Additionally,the effectiveness of emission reduction scenarios was explored.The industry,power plant,and transportation emission source types were found to be the most important in terms of their individual effects on O3DM.The key contributor to high surface O3 was power plant emissions,with a peak individual effect of 40 ppbv in the southwestern BTH area.The individual effect from the biogenic emission category was quite low.The synergistic effects from the combinations of each pair of anthropogenic emission types suppressed O3 formation,while the synergistic effects for combinations of three were favorable for O3 formation when the industrial and power plant emission source types coexisted.The quadruple synergistic effects were positive only with the combination of power plant,transportation,residential,and biogenic sources,while the quintuple synergistic effect showed only minor impacts on O3DM concentrations.A 30％ reduction in industrial and transportation sources produced the most effective impacts on O3 concentrations,with a maximum decrease of 20 ppbv.These results suggested that the synergistic impacts among emission source types should be considered when formulating emission control strategies for O3 reduction.  相似文献   

11.
In part two of this series of papers on the IMS model, we present the chemistry reaction mechanism usedand compare modelled CH4, CO, and O3 witha dataset of annual surface measurements. The modelled monthly and 24-hour mean tropospheric OH concentrationsrange between 5–22 × 105 moleculescm–3, indicating an annualaveraged OH concentration of about 10 × 105 moleculescm–3. This valueis close to the estimated 9.7 ± 0.6 × 105 moleculescm–3 calculated fromthe reaction of CH3CCl3 with OH radicals.Comparison with CH4 generally shows good agreementbetween model and measurements, except for the site at Barrow where modelledwetland emission in the summer could be a factor 3 too high.For CO, the pronounced seasonality shown in the measurements is generally reproduced by the model; however, the modelled concentrations are lower thanthe measurements. This discrepancy may due to lower the CO emission,especially from biomass burning,used in the model compared with other studies.For O3, good agreement between the model and measurements is seenat locations which are away from industrial regions. The maximum discrepancies between modelled results and measurementsat tropical and remote marine sites is about 5–10 ppbv,while the discrepancies canexceed 30 ppbv in the industrial regions.Comparisons in rural areas at European and American continental sites arehighly influenced by the local photochemicalproduction, which is difficult to model with a coarse global CTM.The very large variations of O3 at these locations vary from about15–25 ppbv in Januaryto 55–65 ppbv in July–August. The observed annual O3amplitude isabout 40 ppbv compared with about 20 ppbv in the model. An overall comparison of modelled O3 with measurements shows thatthe O3seasonal surface cycle is generally governed bythe relative importance of two key mechanisms that drivea springtime ozone maximum and asummertime ozone maximum.  相似文献   

12.
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   

13.
中国地区臭氧前体物对地面臭氧的影响   总被引：5，自引：1，他引：4  
利用GEOS-Chem模式的数值试验结果,研究中国地区NOx和两类VOCs对O3质量浓度分布及其化学机理的影响。研究表明,NOx的减少会使得中国西部O3质量浓度显著降低,但在冬季NOx的减少会使得东北、华北地区O3质量浓度上升。而京津唐地区由于VOCs/NOx比值偏低,不能通过单一减少NOx来控制O3质量浓度。VOCs排放的减少会使得我国东部地区O3质量浓度大幅减少,其中人为VOCs的减少能降低我国东部地面O3质量浓度,而生物VOCs的减少只能在夏秋季有效减少我国东部地区35°N以南区域的地面O3质量浓度。控制地面O3质量浓度时,中国西部主要考虑NOx的减排,东部35°N以北主要考虑AVOCs的减排,而30~35°N应同时考虑AVOCs和BVOCs的减排,在30°N以南的地区,则需要全面考虑NOx和VOCs的减排。  相似文献   

14.
秸秆焚烧对区域城市空气质量影响的模拟分析   总被引：2，自引：0，他引：2  
利用融合火点排放源、人为源和生物源的WRF-Chem(Weather Research and Forecasting Model coupled with Chemistry)模式,模拟2015年9月30日08:00(北京时间)起的72 h发生在淮河流域的一次农作物秸秆大面积露天焚烧过程,研究了农作物秸秆焚烧释放的气态污染物和颗粒物对区域城市空气质量的影响。通过有无火点两组试验分析了此次秸秆焚烧对流域内河南、山东、江苏和安徽四省83座城市CO、PM10(空气动力学当量直径小于等于10μm的颗粒物,即可吸入颗粒物)、PM2.5(空气动力学当量直径小于等于2.5μm的颗粒物,即细颗粒物)和O3浓度的定量影响,结果表明:(1)融合NCAR-FINN(Fire Inventory from NCAR)火点排放资料的WRF-Chem模式较好地再现了此次秸秆焚烧及火点烟羽扩散过程。同时结合EDGAR-HTAP(Emission Database for Global Atmospheric Research on Hemispheric Transport of Air Pollution)人为源和MEGAN(Model of Emission of Gases and Aerosols from Nature)生物源的WRF-FIRE(考虑火点排放试验)对流域内城市大气污染物的模拟效果较为理想,尤其对秸秆焚烧释放的污染物CO、PM10和PM2.5和产生的二次污染物O3浓度的模拟。(2)秸秆焚烧所释放的污染物造成流域内城市一次污染物CO、PM10和PM2.5浓度的增加,火点中心和下风向城市增幅最为明显,最大小时浓度增幅达到3倍标准差。气态污染物CO和相比PM10粒径更小的PM2.5可随风扩散至更远的地区,对城市浓度影响更大。(3)此外,秸秆焚烧也使得火点中心城市和下风向城市二次污染物O3浓度增加,但小时浓度增幅极值区分布在火点下风向烟羽末端太阳光照充足的地区,最大小时浓度增幅接近3倍标准差。秸秆焚烧对区域城市空气质量的影响存在明显的空间分布差异且对城市各大气污染成分的影响也不相同。  相似文献   

15.
A unified chemistry-aerosol-climate model is applied in this work to compare climate responses to chang- ing concentrations of long-lived greenhouse gases(GHGs,CO2,CH4,N2O),tropospheric O3,and aerosols during the years 1951–2000.Concentrations of sulfate,nitrate,primary organic carbon(POA),secondary organic carbon(SOA),black carbon(BC)aerosols,and tropospheric O3 for the years 1950 and 2000 are obtained a priori by coupled chemistry-aerosol-GCM simulations,and then monthly concentrations are in- terpolated ...  相似文献   

16.
Measurements of surface O3, CO, NOx and light NMHCs were made during December 2004 at Hissar, a semi-urban site in the state of Haryana in north-west region of the Indo-Gangetic Plain (IGP). The night-time O3 values were higher when levels of CO, NO and NO2 were lower but almost zero values were observed during the episodes of elevated mixing ratios of CO (above 2000 ppbv) and NOx (above 50 ppbv). Slopes derived from linear fits of O3 versus CO and O3 versus NOx scatter plots were also negative. However, elevated levels of O3 were observed when CO and NOx were in the range of 200–300 ppbv and 20–30 ppbv, respectively. Slope of CO-NOx of about 33 ppbv/ppbv is much larger than that observed in the US and Europe indicating significant impact of incomplete combustion processes emitting higher CO and lesser NOx. Correlations and ratios of these trace gases including NMHCs show dominance of recently emitted pollutants mostly from biomass burning at this site.  相似文献   

17.
Effects of tropical deforestation on global and regional atmospheric chemistry   总被引：10，自引：0，他引：10  
A major portion of tropospheric photochemistry occurs in the tropics. Deforestation, colonization, and development of tropical rain forest areas could provoke significant changes in emissions of radiatively and photochemically active trace gases. A brief review of studies on trace-gas emissions in pristine and disturbed tropical habitats is followed by an effort to model regional tropospheric chemistry under undisturbed and polluted conditions. Model results suggest that changing emissions could stimulate photochemistry leading to enhanced ozone production and greater mineral acidity in rainfall in colonized agricultural regions. Model results agree with measurements made during the NASA ABLE missions. Under agricultural/pastoral development scenarios, tropical rain forest regions could export greater levels of N2O, CH4, CO, and photochemical precursors of NO y and O3 to the global atmosphere with implications for climatic warming.  相似文献   

18.
Emissions may affect climate indirectly through chemical interactions in the atmosphere, but quantifications of such effects are difficult and uncertain due to incomplete knowledge and inadequate methods. A preliminary assessment of the climatic impact of changes in tropospheric O3 and CH4 in response to various emissions is given. For a 10% increase in the CH4 emissions the relative increase in concentration has been estimated to be 37% larger. The radiative forcing from enhanced levels of tropospheric O3 is estimated to 37% of the forcing from changes in CH4. Inclusion of indirect effects approximately doubles the climatic impact of CH4 emissions. Emissions of NOx increase tropospheric O3, while the levels of CH4 are reduced. For emissions of NOx from aircraft, the positive effects via O3 changes are significantly larger than the negative through changes in CH4. For NOx emitted from surface sources, the effects through changes in O3 and CH4 are estimated to be of similar magnitude and large uncertainty is connected to the sign of the net effect. Emissions of CO have positive indirect effects on climate through enhanced levels of tropospheric o3 and increased lifetime of CH4. These results form the basis for estimates of global warming potentials for sustained step increases in emissions.  相似文献   

19.
The North China Plain （NCP） has recently faced serious air quality problems as a result of enhanced gas pollutant emissions due to the process of urbanization and rapid economic growth. To explore regional air pollu- tion in the NCP, measurements of surface ozone （O3）, nitrogen oxides （NOx）, and sulfur dioxide （SO2） were car- ried out from May to November 2013 at a rural site （Xianghe） between the twin megacities of Beijing and Tianjin. The highest hourly ozone average was close to 240 ppbv in May, followed by around 160 ppbv in June and July. High ozone episodes were more notable than in 2005 and were mainly associated with air parcels from the city cluster in the hinterland of the polluted NCP to the southwest of the site. For NOx, an important ozone precur- sor, the concentrations ranged from several ppbv to nearly 180 ppbv in the summer and over 400 ppbv in the fall. The occurrence of high NOx concentrations under calm condi- tions indicated that local emissions were dominant in Xianghe. The double-peak diurnal pattern found in NOx concentrations and NO/NOx ratios was probably shaped by local emissions, photochemical removal, and dilution re- sulting from diurnal variations of surface wind speed and the boundary layer height. A pronounced SO2 daytime peak was noted and attributed to downward mixing from an SO2-rich layer above, while the SO2-polluted air mass transported from possible emission sources, which differed between the non-heating （September and October） and heating （November） periods, was thought to be responsible for night-time high concentrations.  相似文献   

20.
This paper investigates, the variability and correlation of surface ozone (Os) and carbon monoxide (CO) observed at Cape D'Aguilar in Hong Kong from 1 January 1994 to 31 December 1995. Statistical analysis shows that the average O3 and CO mixing ratios during the two years are 32±17ppbv and 305±191 ppbv, respectively. The O3/CO ratio ranges from 0.05 to 0.6 ppbv/ppbv with its frequency peaking at 0.15. The raw dataset is divided into six groups using backward trajectory and cluster analyses. For data assigned to the same trajectory type, three groups are further sorted out based on CO and NOX mixing ratios. The correlation coefficients and slopes of O3/CO for the 18 groups are calculated using linear regression analysis. Finally, five kinds of air masses with different chemical features are identified: continental background (CB), marine background (MB), regional polluted continental (RPC), perturbed marine (P*M), and local polluted (LP) air masses. Further studies indicate that O3 and CO in the conti  相似文献   

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