scholarly journals Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies

2021 ◽  
Author(s):  
Zhenze Liu ◽  
Ruth M. Doherty ◽  
Oliver Wild ◽  
Michael Hollaway ◽  
Fiona M. O'Connor
Keyword(s):  
Climate Model ◽  
Control Strategies ◽  
Regional Scale ◽  
Emission Control ◽  
Response Surfaces ◽  
River Delta ◽  
Nox Emissions ◽  
Voc Emissions ◽  
Industrial Regions ◽  
Surface O3

Abstract. The UKCA chemistry-climate model is used to quantify the differences in chemical environment for surface O3 for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive VOC tracers that are necessary to represent urban and regional-scale O3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O3 concentrations across these regions well. Simulated O3 concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime O3 production rates in Guangzhou. NOx / VOC and H2O2 / HNO3 ratios indicate that O3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O3 response surfaces for each region changing NOx and VOC emissions and further contrast the effectiveness of measures to reduce surface O3 concentrations. In VOC limited regions, reducing NOx emissions by 20 % leads to a substantial O3 increase (11 %) in Shanghai. We find that reductions in NOx emissions alone of more than 70 % are required to decrease O3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (−11 %) in O3 levels in Shanghai and Guangzhou and the smallest decrease (−1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher NOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O3 pollution in these major industrial regions, and emphasizes that combined NOx and VOC emission controls play a pivotal role in effectively offsetting high O3 levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air quality-climate interactions.

scholarly journals Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies

2021 ◽  
Vol 21 (13) ◽  
pp. 10689-10706
Author(s):  
Zhenze Liu ◽  
Ruth M. Doherty ◽  
Oliver Wild ◽  
Michael Hollaway ◽  
Fiona M. O’Connor
Keyword(s):  
Climate Model ◽  
Control Strategies ◽  
Regional Scale ◽  
Emission Control ◽  
Response Surfaces ◽  
River Delta ◽  
Nox Emissions ◽  
Voc Emissions ◽  
Industrial Regions ◽  
Surface O3

Abstract. The United Kingdom Chemistry and Aerosols (UKCA) chemistry–climate model is used to quantify the differences in chemical environment for surface O3 for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive volatile organic compound (VOC) tracers that are necessary to represent urban and regional-scale O3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O3 concentrations across these regions well. Simulated O3 concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime O3 production rates in Guangzhou. NOx / VOC and H2O2 / HNO3 ratios indicate that O3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O3 response surfaces for each region changing NOx and VOC emissions and further contrast the effectiveness of measures to reduce surface O3 concentrations. In VOC-limited regions, reducing NOx emissions by 20 % leads to a substantial O3 increase (11 %) in Shanghai. We find that reductions in NOx emissions alone of more than 70 % are required to decrease O3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (−11 %) in O3 levels in Shanghai and Guangzhou and the smallest decrease (−1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher NOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O3 pollution in these major industrial regions and emphasises that combined NOx and VOC emission controls play a pivotal role in effectively offsetting high O3 levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air-quality–climate interactions.

scholarly journals Decadal changes in summertime reactive oxidized nitrogen and surface ozone over the Southeast United States

2018 ◽  
Vol 18 (3) ◽  
pp. 2341-2361 ◽  
Author(s):  
Jingyi Li ◽  
Jingqiu Mao ◽  
Arlene M. Fiore ◽  
Ronald C. Cohen ◽  
John D. Crounse ◽  
...  
Keyword(s):  
Climate Model ◽  
Surface Ozone ◽  
Regional Scale ◽  
Nox Emissions ◽  
Alkyl Nitrates ◽  
Southeast United States ◽  
Ground Measurement ◽  
Southeast Us ◽  
June July ◽  
Relative Change

Abstract. Widespread efforts to abate ozone (O3) smog have significantly reduced emissions of nitrogen oxides (NOx) over the past 2 decades in the Southeast US, a place heavily influenced by both anthropogenic and biogenic emissions. How reactive nitrogen speciation responds to the reduction in NOx emissions in this region remains to be elucidated. Here we exploit aircraft measurements from ICARTT (July–August 2004), SENEX (June–July 2013), and SEAC4RS (August–September 2013) and long-term ground measurement networks alongside a global chemistry–climate model to examine decadal changes in summertime reactive oxidized nitrogen (RON) and ozone over the Southeast US. We show that our model can reproduce the mean vertical profiles of major RON species and the total (NOy) in both 2004 and 2013. Among the major RON species, nitric acid (HNO3) is dominant (∼ 42–45 %), followed by NOx (31 %), total peroxy nitrates (ΣPNs; 14 %), and total alkyl nitrates (ΣANs; 9–12 %) on a regional scale. We find that most RON species, including NOx, ΣPNs, and HNO3, decline proportionally with decreasing NOx emissions in this region, leading to a similar decline in NOy. This linear response might be in part due to the nearly constant summertime supply of biogenic VOC emissions in this region. Our model captures the observed relative change in RON and surface ozone from 2004 to 2013. Model sensitivity tests indicate that further reductions of NOx emissions will lead to a continued decline in surface ozone and less frequent high-ozone events.

scholarly journals Spatial and temporal changes of the ozone sensitivity in China based on satellite and ground-based observations

2020 ◽  
Author(s):  
Wannan Wang ◽  
Ronald van der A ◽  
Jieying Ding ◽  
Michiel van Weele ◽  
Tianhai Cheng
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Eastern China ◽  
Ground Level ◽  
Nox Emissions ◽  
Transitional Regime ◽  
Ground Level Ozone ◽  
Ozone Sensitivity ◽  
Rural And Remote Areas ◽  
Surface O3

Abstract. Ground-level ozone (O3) pollution has been steadily getting worse in most part of eastern China during the past five years. The non-linearity of O3 formation with its precursors like nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs) are complicating effective O3 abatement plans. The diagnosis from space-based observations, the ratio of formaldehyde (HCHO) columns to tropospheric NO2 columns (HCHO / NO2), has previously been proved to be highly consistent with our current understanding of surface O3 chemistry. HCHO / NO2 ratio thresholds distinguishing O3 formation sensitivity depend on regions and O3 chemistry interactions with aerosol. To shed more light on current the O3 formation sensitivity over China, we have derived HCHO / NO2 ratio thresholds by directly connecting satellite-based HCHO / NO2 observations and ground-based O3 measurements over the major Chinese cities in this study. We find that a VOC-limited regime occurs for HCHO / NO2  4.2. The HCHO / NO2 between 2.3 and 4.2 reflects the transition between the two regimes. Our method shows that the O3 formation sensitivity tends to be VOC-limited over urban areas and NOx-limited over rural and remote areas in China. We find that there is a shift in some cities from the VOC-limited to the transitional regime that is associated with a rapid drop of anthropogenic NOx emissions owing to the widely-applied rigorous emission control strategies between 2016 and 2019. This detected spatial expansion of the transitional regime is supported by rising surface O3 concentrations. The enhanced O3 concentrations in urban areas during the COVID-19 lockdown in China indicate that a protocol with simultaneous anthropogenic NOx emissions and VOC emissions controls is essential for O3 abatement plans.

scholarly journals Path-integral method for the source apportionment of photochemical pollutants

2014 ◽  
Vol 7 (6) ◽  
pp. 9079-9107 ◽  
Author(s):  
A. M. Dunker
Keyword(s):  
Path Integral ◽  
Integral Method ◽  
Direct Method ◽  
Emission Control ◽  
Nox Emissions ◽  
Concentration Difference ◽  
Voc Emissions ◽  
Source Contributions ◽  
The Difference ◽  
Path Integral Method

Abstract. A new, path-integral method is presented for apportioning the concentrations of pollutants predicted by a photochemical model to emissions from different sources. A novel feature of the method is that it can apportion the difference in a species concentration between two simulations. For example, the anthropogenic ozone increment, which is the difference between a simulation with all emissions present and another simulation with only the background (e.g., biogenic) emissions included, can be allocated to the anthropogenic emission sources. The method is based on an existing, exact mathematical equation. This equation is applied to relate the concentration difference between simulations to line or path integrals of first-order sensitivity coefficients. The sensitivities describe the effects of changing the emissions and are accurately calculated by the decoupled direct method. The path represents a continuous variation of emissions between the two simulations, and each path can be viewed as a separate emission-control strategy. The method does not require auxiliary assumptions, e.g., whether ozone formation is limited by the availability of volatile organic compounds (VOC's) or nitrogen oxides (NOx), and can be used for all the species predicted by the model. A simplified configuration of the Comprehensive Air Quality Model with Extensions is used to evaluate the accuracy of different numerical integration procedures and the dependence of the source contributions on the path. A Gauss–Legendre formula using 3 or 4 points along the path gives good accuracy for apportioning the anthropogenic increments of ozone, nitrogen dioxide, formaldehyde, and nitric acid. Source contributions to these increments were obtained for paths representing proportional control of all anthropogenic emissions together, control of NOx emissions before VOC emissions, and control of VOC emissions before NOx emissions. There are similarities in the source contributions from the three paths but also differences due to the different chemical regimes resulting from the emission-control strategies.

scholarly journals Retrospective analysis of 2015–2017 winter-time PM<sub>2.5</sub> in China: response to emission regulations and the role of meteorology

2018 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Junmei Ban ◽  
Pusheng Zhao ◽  
Min Chen
Keyword(s):  
Control Experiment ◽  
Control Strategies ◽  
Emission Control ◽  
Reanalysis Data ◽  
River Delta ◽  
Central China ◽  
Pressure System ◽  
Pollution Dispersion ◽  
Assimilation Experiment ◽  
Winter Time

Abstract. To better characterize the anthropogenic emission relevant aerosol species, the GSI-WRF/Chem data assimilation system was updated from the GOCART aerosol scheme to MOSAIC-4BIN scheme. Three year (2015–2017) winter-time (January) surface PM2.5 observations from 1600&amp;plus; sites were assimilated hourly using the updated 3DVAR system in the assimilation experiment CONC_DA. Parallel control experiment that did not employ DA (NO_DA) was also performed. Both experiments were verified against the surface PM2.5 observations, MODIS 550-nm AOD and also 550-nm AOD at 9 AERONET sites. In the NO_DA experiment using 2010_MEIC emissions, modeled PM2.5 are severely overestimated in Sichuan Basin (SB), Central China (CC), YRD (Yangzi River Delta), and PRD (Pearl River Delta) which indicated the emissions for 2010 are not appropriate for 2015–2017, as strict emission control strategies were implemented in recent years. Meanwhile, underestimations in Northeastern China (NEC) and Xin Jiang (XJ) were also observed. The assimilation experiments significantly reduced the high biases of surface PM2.5 in SB, CC, YRD, and PRD, and also low biases in NEC. However the improvement of the low biases in XJ is relatively small due to the large difference between the observations and the model background in the DA process, likely indicating that the emissions in the model are seriously underestimated in this region. Assimilating surface PM2.5 also significantly changed the column AOD and resulted in closer agreement with MODIS data and observations at AERONET sites. The observations and the reanalysis data from assimilation experiment were used to investigate the year-to-year changes. As the differences of the reanalysis data (CONC_DA) among years reflect combining effects of meteorology and emission and the differences of modeling result from control experiment (NO_DA, with same emissions) among years reflect the separate effect of meteorology, the important roles of emission and meteorology in driving the changes in the three years can be distinguished and analyzed quantitatively. The analysis indicated that meteorology played different roles in 2016 and 2017: the higher pressure system, lower temperature and higher PBLH in 2016 are favorable for pollution dispersion (compared with 2015) while the situation is almost the opposite in 2017 (compared with 2016) that leads to the increasing PM2.5 from 2016 to 2017 although emission control strategy were implemented in both years. There are still large uncertainties in this approach especially the inaccurate emission input in the model brings large biases in the analysis.

scholarly journals Path-integral method for the source apportionment of photochemical pollutants

2015 ◽  
Vol 8 (6) ◽  
pp. 1763-1773 ◽  
Author(s):  
A. M. Dunker
Keyword(s):  
Path Integral ◽  
Integral Method ◽  
Direct Method ◽  
Emission Control ◽  
Nox Emissions ◽  
Concentration Difference ◽  
Voc Emissions ◽  
Source Contributions ◽  
The Difference ◽  
Path Integral Method

Abstract. A new, path-integral method is presented for apportioning the concentrations of pollutants predicted by a photochemical model to emissions from different sources. A novel feature of the method is that it can apportion the difference in a species concentration between two simulations. For example, the anthropogenic ozone increment, which is the difference between a simulation with all emissions present and another simulation with only the background (e.g., biogenic) emissions included, can be allocated to the anthropogenic emission sources. The method is based on an existing, exact mathematical equation. This equation is applied to relate the concentration difference between simulations to line or path integrals of first-order sensitivity coefficients. The sensitivities describe the effects of changing the emissions and are accurately calculated by the decoupled direct method. The path represents a continuous variation of emissions between the two simulations, and each path can be viewed as a separate emission-control strategy. The method does not require auxiliary assumptions, e.g., whether ozone formation is limited by the availability of volatile organic compounds (VOCs) or nitrogen oxides (NOx), and can be used for all the species predicted by the model. A simplified configuration of the Comprehensive Air Quality Model with Extensions (CAMx) is used to evaluate the accuracy of different numerical integration procedures and the dependence of the source contributions on the path. A Gauss–Legendre formula using three or four points along the path gives good accuracy for apportioning the anthropogenic increments of ozone, nitrogen dioxide, formaldehyde, and nitric acid. Source contributions to these increments were obtained for paths representing proportional control of all anthropogenic emissions together, control of NOx emissions before VOC emissions, and control of VOC emissions before NOx emissions. There are similarities in the source contributions from the three paths but also differences due to the different chemical regimes resulting from the emission-control strategies.

scholarly journals Spatial and temporal changes of the ozone sensitivity in China based on satellite and ground-based observations

2021 ◽  
Vol 21 (9) ◽  
pp. 7253-7269
Author(s):  
Wannan Wang ◽  
Ronald van der A ◽  
Jieying Ding ◽  
Michiel van Weele ◽  
Tianhai Cheng
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Eastern China ◽  
Ground Level ◽  
Nox Emissions ◽  
Transitional Regime ◽  
Ground Level Ozone ◽  
Ozone Sensitivity ◽  
Rural And Remote Areas ◽  
Surface O3

Abstract. Ground-level ozone (O3) pollution has been steadily getting worse in most parts of eastern China during the past 5 years. The non-linearity of O3 formation with its precursors like nitrogen oxides (NOx= NO + NO2) and volatile organic compounds (VOCs) are complicating effective O3 abatement plans. The diagnosis from space-based observations, i.e. the ratio of formaldehyde (HCHO) columns to tropospheric NO2 columns (HCHO / NO2), has previously been proved to be highly consistent with our current understanding of surface O3 chemistry. HCHO / NO2 ratio thresholds distinguishing O3 formation sensitivity depend on regions and O3 chemistry interactions with aerosol. To shed more light on the current O3 formation sensitivity over China, we have derived HCHO / NO2 ratio thresholds by directly connecting satellite-based HCHO / NO2 observations and ground-based O3 measurements over the major Chinese cities in this study. We find that a VOC-limited regime occurs for HCHO / NO2 < 2.3, and a NOx-limited regime occurs for HCHO / NO2 > 4.2. The HCHO / NO2 between 2.3 and 4.2 reflects the transition between the two regimes. Our method shows that the O3 formation sensitivity tends to be VOC-limited over urban areas and NOx-limited over rural and remote areas in China. We find that there is a shift in some cities from the VOC-limited regime to the transitional regime that is associated with a rapid drop in anthropogenic NOx emissions, owing to the widely applied rigorous emission control strategies between 2016 and 2019. This detected spatial expansion of the transitional regime is supported by rising surface O3 concentrations. The enhanced O3 concentrations in urban areas during the COVID-19 lockdown in China indicate that a protocol with simultaneous anthropogenic NOx emissions and VOC emissions controls is essential for O3 abatement plans.

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