scholarly journals An unexpected large continental source of reactive bromine and chlorine with significant impact on wintertime air quality

2020 ◽  
Author(s):  
Xiang Peng ◽  
Weihao Wang ◽  
Men Xia ◽  
Hui Chen ◽  
A R Ravishankara ◽  
...  
Keyword(s):  
Air Quality ◽  
Atmospheric Chemistry ◽  
North China ◽  
Primary Source ◽  
Ozone Production ◽  
Bromine Chloride ◽  
Halogen Atoms ◽  
Continental Source ◽  
Cl Atoms

Abstract Halogen atoms affect the budget of ozone and the fate of pollutants such as hydrocarbons and mercury. Yet their sources and significances in polluted continental regions are poorly understood. Here we report the observation of unprecedented levels (averaging to 60 parts per trillion) of bromine chloride (BrCl) at a mid-latitude site in North China during winter. Widespread coal burning in rural households and a photo-assisted process were the primary source of BrCl and other bromine gases. BrCl contributed about 55% of both bromine (Br) and chlorine (Cl) atoms. The halogen atoms increased the abundance of ‘conventional’ tropospheric oxidants (OH, HO2, and RO2) by 26–73%, and enhanced oxidation of hydrocarbon by nearly a factor of two and the net ozone production by 55%. Our study reveals the significant role of reactive halogen in winter atmospheric chemistry and the deterioration of air quality in continental regions where uncontrolled coal combustion is prevalent.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

Urban particulate matter pollution: a tale of five cities

2016 ◽  
Vol 189 ◽  
pp. 277-290 ◽  
Author(s):  
Spyros N. Pandis ◽  
Ksakousti Skyllakou ◽  
Kalliopi Florou ◽  
Evangelia Kostenidou ◽  
Christos Kaltsonoudis ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Los Angeles ◽  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Fine Particulate Matter ◽  
The United States ◽  
Chemical Signatures ◽  
Range Transport

Five case studies (Athens and Paris in Europe, Pittsburgh and Los Angeles in the United States, and Mexico City in Central America) are used to gain insights into the changing levels, sources, and role of atmospheric chemical processes in air quality in large urban areas as they develop technologically. Fine particulate matter is the focus of our analysis. In all cases reductions of emissions by industrial and transportation sources have resulted in significant improvements in air quality during the last few decades. However, these changes have resulted in the increasing importance of secondary particulate matter (PM) which dominates over primary in most cases. At the same time, long range transport of secondary PM from sources located hundreds of kilometres from the cities is becoming a bigger contributor to the urban PM levels in all seasons. “Non-traditional” sources including cooking, and residential and agricultural biomass burning contribute an increasing fraction of the now reduced fine PM levels. Atmospheric chemistry is found to change the chemical signatures of a number of these sources relatively fast both during the day and night, complicating the corresponding source apportionment.

scholarly journals Significant increase of summertime ozone at Mount Tai in Central Eastern China

2016 ◽  
Vol 16 (16) ◽  
pp. 10637-10650 ◽  
Author(s):  
Lei Sun ◽  
Likun Xue ◽  
Tao Wang ◽  
Jian Gao ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Production Efficiency ◽  
North China ◽  
Climate Model ◽  
Eastern China ◽  
Linear Regression Analysis ◽  
Ozone Production ◽  
The North ◽  
Short Period ◽  
Central Eastern

Abstract. Tropospheric ozone (O3) is a trace gas playing important roles in atmospheric chemistry, air quality and climate change. In contrast to North America and Europe, long-term measurements of surface O3 are very limited in China. We compile available O3 observations at Mt. Tai – the highest mountain over the North China Plain – during 2003–2015 and analyze the decadal change of O3 and its sources. A linear regression analysis shows that summertime O3 measured at Mt. Tai has increased significantly by 1.7 ppbv yr−1 for June and 2.1 ppbv yr−1 for the July–August average. The observed increase is supported by a global chemistry-climate model hindcast (GFDL-AM3) with O3 precursor emissions varying from year to year over 1980–2014. Analysis of satellite data indicates that the O3 increase was mainly due to the increased emissions of O3 precursors, in particular volatile organic compounds (VOCs). An important finding is that the emissions of nitrogen oxides (NOx) have diminished since 2011, but the increase of VOCs appears to have enhanced the ozone production efficiency and contributed to the observed O3 increase in central eastern China. We present evidence that controlling NOx alone, in the absence of VOC controls, is not sufficient to reduce regional O3 levels in North China in a short period.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Vol 17 (22) ◽  
pp. 13669-13680 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth's climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain-like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model–model comparisons to better identify the root causes of model differences.

scholarly journals Elevated dust layers inhibit dissipation of heavy anthropogenic surface air pollution

2020 ◽  
Vol 20 (23) ◽  
pp. 14917-14932
Author(s):  
Zhuang Wang ◽  
Cheng Liu ◽  
Zhouqing Xie ◽  
Qihou Hu ◽  
Meinrat O. Andreae ◽  
...  
Keyword(s):  
Air Quality ◽  
North China ◽  
Spherical Particles ◽  
Trace Gas ◽  
Nonspherical Particles ◽  
Anthropogenic Aerosols ◽  
Haze Pollution ◽  
Multi Wavelength ◽  
Upper Level

Abstract. Persistent wintertime heavy haze incidents caused by anthropogenic aerosols have repeatedly shrouded North China in recent years, while natural dust from the west and northwest of China also frequently affects air quality in this region. Through continuous observation by a multi-wavelength Raman lidar, here we found that wintertime aerosols in North China are typically characterized by a pronounced vertical stratification, where scattering nonspherical particles (dust or mixtures of dust and anthropogenic aerosols) dominated above the planetary boundary layer (PBL), and absorbing spherical particles (anthropogenic aerosols) prevailed within the PBL. This stratification is governed by meteorological conditions that strong northwesterly winds usually prevailed in the lower free troposphere, and southerly winds dominated in the PBL, producing persistent and intense haze pollution. With the increased contribution of elevated dust to the upper aerosols, the proportion of aerosol and trace gas at the surface in the whole column increased. Model results show that, besides directly deteriorating air quality, the key role of the elevated dust is to depress the development of PBL and weaken the turbulent exchange, mostly by lower level cooling and upper level heating, and it is more obvious during the dissipation stage, thus inhibiting the dissipation of heavy surface anthropogenic aerosols. The interactions of natural dust and anthropogenic aerosols under the unique topography of North China increase the surface anthropogenic aerosols and precursor gases, which may be one of the reasons why haze pollution in North China is heavier than that in other heavily polluted areas in China.

scholarly journals Chemical Analysis of Surface-Level Ozone Exceedances during the 2015 Pan American Games

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 572 ◽  
Author(s):  
Craig Stroud ◽  
Shuzhan Ren ◽  
Junhua Zhang ◽  
Michael Moran ◽  
Ayodeji Akingunola ◽  
...  
Keyword(s):  
Air Quality ◽  
Field Study ◽  
Atmospheric Chemistry ◽  
Urban Air Quality ◽  
Ozone Production ◽  
Urban Air ◽  
Lake Breeze ◽  
Surface Level ◽  
Pan American ◽  
Updraft Region

Surface-level ozone (O3) continues to be a significant health risk in the Greater Toronto Hamilton Area (GTHA) of Canada even though precursor emissions in the area have decreased significantly over the past two decades. In July 2015, Environment and Climate Change Canada (ECCC) led an intensive field study coincident with Toronto hosting the 2015 Pan American Games. During the field study, the daily 1-h maximum O3 standard (80 ppbv) was exceeded twice at a measurement site in North Toronto, once on July 12 and again on July 28. In this study, ECCC’s 2.5-km configuration of the Global Environmental Multi-scale (GEM) meteorological model was combined with the Modelling Air-quality and CHemistry (MACH) on-line atmospheric chemistry model and the Town Energy Balance (TEB) urban surface parameterization to create a new urban air quality modelling system. In general, the model results showed that the nested 2.5-km grid-spaced urban air quality model performed better in statistical scores compared to the piloting 10-km grid-spaced GEM-MACH model without TEB. Model analyses were performed with GEM-MACH-TEB for the two exceedance periods. The local meteorology for both cases consisted of light winds with the highest O3 predictions situated along lake-breeze fronts. For the July 28 case, O3 production sensitivity analysis along the trajectory of the lake-breeze circulation showed that the region of most efficient O3 production occurred in the updraft region of the lake-breeze front, as the precursors to O3 formation underwent vertical mixing. In this updraft region, the ozone production switches from volatile organic compound (VOC)-sensitive to NOx-sensitive, and the local net O3 production rate reaches a maximum. This transition in the chemical regime is a previously unidentified factor for why O3 surface-level mixing ratios maximize along the lake-breeze front. For the July 12 case, differences between the model and observed Lake Ontario water temperature and the strength of lake-breeze opposing wind flow play a role in differences in the timing of the lake-breeze, which impacts the predicted location of the O3 maximum north of Toronto.

scholarly journals Interference from alkenes in chemiluminescent NO<sub><i>x</i></sub> measurements

2020 ◽  
Vol 13 (11) ◽  
pp. 5977-5991
Author(s):  
Mohammed S. Alam ◽  
Leigh R. Crilley ◽  
James D. Lee ◽  
Louisa J. Kramer ◽  
Christian Pfrang ◽  
...  
Keyword(s):  
Air Quality ◽  
Atmospheric Chemistry ◽  
Systematic Investigation ◽  
Atmospheric Pollutants ◽  
Quality Monitoring ◽  
Ozone Production ◽  
Atmospheric Composition ◽  
Anthropogenic Sources ◽  
Indoor Environments ◽  
Air Quality Monitoring

Abstract. Nitrogen oxides (NOx=NO+NO2) are critical intermediates in atmospheric chemistry and air pollution. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3 and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants, such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial for air quality monitoring and understanding atmospheric composition. The most commonly used approach for the measurement of NO is the chemiluminescent detection of electronically excited NO2 (NO2∗) formed from the NO + O3 reaction within the NOx analyser. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in conventional instrument background cycles, which also utilises the reaction with ozone, differs from that in the measurement cycle such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed, the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors to a series of alkenes. These NOx monitors range from systems used for routine air quality monitoring to atmospheric research instrumentation. The species-investigated range was from short-chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European PHOtoREactor (EUPHORE) to ensure common calibration and samples for the monitors and to unequivocally confirm the alkene levels present (via Fourier transform infrared spectroscopy – FTIR). The instrument interference responses ranged from negligible levels up to 11 %, depending upon the alkene present and conditions used (e.g. the presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high VOC, low NOx environments such as forests or indoor environments where alkene abundance from personal care and cleaning products may be significant.

scholarly journals Elevated dust layers inhibit dissipation of heavy anthropogenic surface air pollution

2020 ◽  
Author(s):  
Zhuang Wang ◽  
Cheng Liu ◽  
Zhouqing Xie ◽  
Qihou Hu ◽  
Meinrat O. Andreae ◽  
...  
Keyword(s):  
Air Quality ◽  
North China ◽  
Spherical Particles ◽  
Trace Gas ◽  
Anthropogenic Aerosols ◽  
Haze Pollution ◽  
Multi Wavelength ◽  
Upper Level ◽  
Winter Time

Abstract. Persistent winter–time heavy haze incidents caused by anthropogenic aerosols have repeatedly shrouded North China in recent years, while natural dust from west and northwest of China also frequently affects air quality in this region. Through continuous observation by a multi–wavelength Raman lidar, here we found that aerosols in North China are typically characterized by a pronounced vertical stratification, where scattering non–spherical particles (dust or mixtures of dust and anthropogenic aerosols) dominated above the planetary boundary layer (PBL), and absorbing spherical particles (anthropogenic aerosols) prevailed within the PBL. This stratification is governed by meteorological conditions that strong northwesterly winds usually prevailed in the lower free troposphere, and southerly winds are dominated in the PBL, producing persistent and intense haze pollution. With the accumulation of elevated dust, the proportion of aerosol and trace gas at the surface in the whole column increased. Model results show that, besides directly deteriorating air quality, the key role of the elevated dust is to depress the development of PBL and weaken the turbulence exchange, mostly by lower–level cooling and upper–level heating, and it is more obvious during dissipation stage, thus inhibiting the dissipation of heavy surface anthropogenic aerosols. The interactions of natural dust and anthropogenic aerosols under the unique topography of North China increases the surface anthropogenic aerosols and precursor gases, which may be one of the reasons why haze pollution in North China is heavier than that in other heavily polluted areas in China.

scholarly journals Significant increase of summertime ozone at Mt. Tai in Central Eastern China: 2003–2015

2016 ◽  
Author(s):  
Lei Sun ◽  
Likun Xue ◽  
Tao Wang ◽  
Jian Gao ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Production Efficiency ◽  
North China ◽  
Eastern China ◽  
Linear Regression Analysis ◽  
Regional Scale ◽  
Ozone Production ◽  
Trace Gas ◽  
Back Trajectory ◽  
Surface O3

Abstract. Tropospheric ozone (O3) is a trace gas playing key roles in atmospheric chemistry, air quality and climate change. In contrast to North America and Europe, China has limited long-term records of surface O3 that can be used to establish trends. In this study, we compiled the available observations of O3 at Mt. Tai – the highest mountain over the North China Plain (NCP), and analyzed their seasonal and diurnal behavior as well as the trends over 2003–2015. The summertime climatological air mass transport pattern was established by back trajectory calculation and a subsequent cluster analysis. A significant increase of surface O3 (p < 0.01) in the summertime from 2003 to 2015 was derived from a linear regression analysis, with increasing rates of 1.7 ppbv yr−1 for June and 2.1 ppbv yr−1 for the July–August period. Analysis of satellite trace gas retrievals indicates that the O3 increase was mainly due to the increased emissions of O3 precursors, in particular volatile organic compounds (VOCs). An important finding is that the emissions of nitrogen oxides (NOx) have diminished since 2011, but the increase of VOCs appears to have enhanced the ozone production efficiency and contributed to the observed O3 increase in northern China. This study provides direct evidence that controlling NOx alone, in the absence of VOC controls, is not sufficient to reduce regional O3 levels in North China. In addition, the ozone observations at this regionally representative mountain site are ideal for evaluating global and regional scale chemical transport models.

scholarly journals Interference from alkenes in chemiluminescent NO<sub><i>x</i></sub> measurements

2020 ◽  
Author(s):  
Mohammed S. Alam ◽  
Leigh R. Crilley ◽  
James D. Lee ◽  
Louisa J. Kramer ◽  
Christian Pfrang ◽  
...  
Keyword(s):  
Air Quality ◽  
Atmospheric Chemistry ◽  
Systematic Investigation ◽  
Atmospheric Pollutants ◽  
Quality Monitoring ◽  
Ozone Production ◽  
Atmospheric Composition ◽  
Anthropogenic Sources ◽  
Indoor Environments ◽  
Air Quality Monitoring

Abstract. Nitrogen oxides (NOx = NO + NO2) are critical intermediates in atmospheric chemistry. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3, and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial to air quality monitoring and understanding atmospheric composition. The most commonly used approach for measurement of NO is chemiluminescent detection of electronically excited NO2 (NO2*) from the NO + O3 reaction. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in the instrument background cycle, which also utilises reaction with ozone, differs from the measurement cycle – such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors, ranging from systems used for routine air quality monitoring to atmospheric research instrumentation, to a series of alkenes. Alkenes investigated range from short chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European Photoreactor (EUPHORE) to ensure common calibration and samples for the monitors, and to unequivocally confirm the alkene levels present (via FTIR). The instrument interference responses ranged from negligible levels up to 11 % depending upon the alkene present and conditions used (e.g. presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high-VOC, low-NOx environments such as forests, or indoor environments where alkene abundance from personal care and cleaning products may be significant.

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