scholarly journals Summertime ozone formation in Xi'an and surrounding areas, China

2015 ◽  
Vol 15 (21) ◽  
pp. 30563-30608 ◽  
Author(s):  
T. Feng ◽  
N. Bei ◽  
R. Huang ◽  
J. Cao ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Control Strategies ◽  
Surface Wind ◽  
Temporal Variations ◽  
Anthropogenic Sources ◽  
Anthropogenic Emissions ◽  
Near Surface ◽  
Production Regime ◽  
High Concentrations ◽  
Surrounding Areas ◽  
Surface O3

Abstract. In the study, the ozone (O3) formation is investigated in Xi'an and surrounding areas, China using the WRF-CHEM model during the period from 22 to 24 August 2013 corresponding to a heavy air pollution episode with high concentrations of O3 and PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm). The WRF-CHEM model generally performs well in simulating the surface temperature and relative humidity compared to the observations and also reasonably reproduces the observed temporal variations of the surface wind speed and direction. The convergence formed in Xi'an and surrounding areas is favorable for the accumulation of pollutants, causing high concentrations of O3 and PM2.5. In general, the calculated spatial patterns and temporal variations of near-surface O3 and PM2.5 are consistent well with the measurement at the ambient monitoring stations. The simulated daily mass concentrations of aerosol constituents, including sulfate, nitrate, ammonium, elemental and organic carbon, are also in good agreement with the filter measurements. High aerosol concentrations in Xi'an and surrounding areas significantly decrease the photolysis frequencies and can reduce near-surface O3 concentrations by more than 50 μg m−3 (around 25 ppb) on average. Sensitivity studies show that the O3 production regime in Xi'an and surrounding areas is complicated, varying from NOx to VOC-sensitive chemistry. The industry emissions contribute the most to the O3 concentrations compared to the natural and other anthropogenic sources, but still do not play a determined role in the O3 formation. The complicated O3 production regime and high aerosol levels constitute a dilemma for O3 control strategies in Xi'an and surrounding areas. In the condition with high O3 and PM2.5 concentrations, decreasing various anthropogenic emissions cannot efficiently mitigate the O3 pollution, and a 50 % reduction of all the anthropogenic emissions only decreases near-surface O3 concentrations by less than 14 % during daytime. Further studies need to be performed for O3 control strategies considering manifest changes of the emission inventory and uncertainties of meteorological field simulations.

scholarly journals Summertime ozone formation in Xi'an and surrounding areas, China

2016 ◽  
Vol 16 (7) ◽  
pp. 4323-4342 ◽  
Author(s):  
Tian Feng ◽  
Naifang Bei ◽  
Ru-Jin Huang ◽  
Junji Cao ◽  
Qiang Zhang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Control Strategies ◽  
Dominant Role ◽  
Anthropogenic Sources ◽  
Anthropogenic Emissions ◽  
Industrial Emissions ◽  
Near Surface ◽  
Production Regime ◽  
Surrounding Areas ◽  
Surface O3

Abstract. In this study, the ozone (O3) formation in China's northwest city of Xi'an and surrounding areas is investigated using the Weather Research and Forecasting atmospheric chemistry (WRF-Chem) model during the period from 22 to 24 August 2013, corresponding to a heavy air pollution episode with high concentrations of O3 and PM2.5. The model generally performs well compared to measurements in simulating the surface temperature, relative humidity, and wind speed and direction, near-surface O3 and PM2.5 mass concentrations, and aerosol constituents. High aerosol concentrations in Xi'an and surrounding areas significantly decrease the photolysis frequencies and can reduce O3 concentrations by more than 50 µg m−3 (around 25 ppb) on average. Sensitivity studies show that the O3 production regime in Xi'an and surrounding areas is complicated, varying from NOx to VOC (volatile organic compound)-sensitive chemistry. The industrial emissions contribute the most to the O3 concentrations compared to biogenic and other anthropogenic sources, but neither individual anthropogenic emission nor biogenic emission plays a dominant role in the O3 formation. Under high O3 and PM2.5 concentrations, a 50 % reduction in all the anthropogenic emissions only decreases near-surface O3 concentrations by about 14 % during daytime. The complicated O3 production regime and high aerosol levels pose a challenge for O3 control strategies in Xi'an and surrounding areas. Further investigation regarding O3 control strategies will need to be performed, taking into consideration the rapid changes in anthropogenic emissions that are not reflected in the current emission inventories and the uncertainties in the meteorological field simulations.

scholarly journals Widespread and Persistent Ozone Pollution in Eastern China

2016 ◽  
Author(s):  
Guohui Li ◽  
Naifang Bei ◽  
Junji Cao ◽  
Jiarui Wu ◽  
Xin Long ◽  
...  
Keyword(s):  
Control Strategies ◽  
Action Plan ◽  
Eastern China ◽  
Pollution Prevention ◽  
Temporal Variations ◽  
Anthropogenic Sources ◽  
Daily Maximum ◽  
Ozone Pollution ◽  
Near Surface ◽  
Model Studies

Abstract. Rapid growth of industrialization, transportation, and urbanization has caused increasing emissions of ozone (O3) precursors recently, enhancing the O3 formation in Eastern China. We show here that Eastern China has experienced widespread and persistent O3 pollution from April to September in 2015 based on the O3 observations in 223 cities. The observed maximum 1-h O3 concentrations exceed 200 μg m−3 in almost all the cities, 400 μg m−3 in more than 25 % of the cities, and even 800 μg m−3 in six cities in Eastern China. The average daily maximum 1-h O3 concentrations are more than 160 μg m−3 in 45 % of the cities, and the 1-h O3 concentrations of 200 μg m−3 have been exceeded on over 10 % of days from April to September in 129 cities. A widespread and severe O3 pollution episode from 22 to 28 May 2015 in Eastern China has been simulated using the WRF-CHEM model to evaluate the O3 contribution of biogenic and various anthropogenic sources. The model generally performs reasonably well in simulating the temporal variations and spatial distributions of near-surface O3 concentrations. Using the factor separate approach, sensitivity studies have indicated that the industry source plays the most important role in the O3 formation, and constitutes the culprit of the severe O3 pollution in Eastern China. The transportation source contributes considerably to the O3 formation, and the O3 contribution of the residential source is not significant generally. The biogenic source provides a background O3 source, and also plays an important role in the south of Eastern China. Further model studies are needed to comprehensively investigate O3 formation for supporting the design and implementation of O3 control strategies, considering rapid changes of emissions inventories and photolysis caused by the "Atmospheric Pollution Prevention and Control Action Plan", released by the Chinese State Council in 2013.

scholarly journals Widespread and persistent ozone pollution in eastern China during the non-winter season of 2015: observations and source attributions

2017 ◽  
Vol 17 (4) ◽  
pp. 2759-2774 ◽  
Author(s):  
Guohui Li ◽  
Naifang Bei ◽  
Junji Cao ◽  
Jiarui Wu ◽  
Xin Long ◽  
...  
Keyword(s):  
Control Strategies ◽  
Action Plan ◽  
Eastern China ◽  
Winter Season ◽  
Pollution Prevention ◽  
Temporal Variations ◽  
Anthropogenic Sources ◽  
Daily Maximum ◽  
Ozone Pollution ◽  
Near Surface

Abstract. Rapid growth of industrialization, transportation, and urbanization has caused increasing emissions of ozone (O3) precursors recently, enhancing the O3 formation in eastern China. We show here that eastern China has experienced widespread and persistent O3 pollution from April to September 2015 based on the O3 observations in 223 cities. The observed maximum 1 h O3 concentrations exceed 200 µg m−3 in almost all the cities, 400 µg m−3 in more than 25 % of the cities, and even 800 µg m−3 in six cities in eastern China. The average daily maximum 1 h O3 concentrations are more than 160 µg m−3 in 45 % of the cities, and the 1 h O3 concentrations of 200 µg m−3 have been exceeded on over 10 % of days from April to September in 129 cities. Analyses of pollutant observations from 2013 to 2015 have shown that the concentrations of CO, SO2, NO2, and PM2.5 from April to September in eastern China have considerably decreased, but the O3 concentrations have increased by 9.9 %. A widespread and severe O3 pollution episode from 22 to 28 May 2015 in eastern China has been simulated using the Weather Research and Forecasting model coupled to chemistry (WRF-CHEM) to evaluate the O3 contribution of biogenic and various anthropogenic sources. The model generally performs reasonably well in simulating the temporal variations and spatial distributions of near-surface O3 concentrations. Using the factor separation approach, sensitivity studies have indicated that the industry source plays the most important role in the O3 formation and constitutes the culprit of the severe O3 pollution in eastern China. The transportation source contributes considerably to the O3 formation, and the O3 contribution of the residential source is not significant generally. The biogenic source provides a background O3 source, and also plays an important role in the south of eastern China. Further model studies are needed to comprehensively investigate O3 formation for supporting the design and implementation of O3 control strategies, considering rapid changes of emission inventories and photolysis caused by the Atmospheric Pollution Prevention and Control Action Plan released by the Chinese State Council in 2013.

scholarly journals Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

2017 ◽  
Author(s):  
Camilla Andersson ◽  
Heléne Alpfjord ◽  
Lennart Robertson ◽  
Per Erik Karlsson ◽  
Magnuz Engardt
Keyword(s):  
Transport Model ◽  
Linear Trend ◽  
Surface Ozone ◽  
Vegetation Indices ◽  
High Sensitivity ◽  
Anthropogenic Emissions ◽  
Data Sets ◽  
Chemistry Transport Model ◽  
Near Surface ◽  
Surface O3

Abstract. We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O3) concentrations for the period 1990–2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using data assimilation. The reanalysis data sets show improved performance than the original CTM when compared to independent observations. In one of the reanalyzes we included all available hourly near-surface O3 observations, whilst in the other we carefully selected time-consistent observations in order to avoid introducing artificial trends. Based on the second reanalysis we investigated statistical aspects of the near-surface O3 concentration, focusing on the linear trend over the 24 year period. We show that high near-surface O3 concentrations are decreasing and low O3 concentrations are increasing, which is mirrored by observed improvement of many health and vegetation indices (apart from those with a low threshold). Using the chemistry-transport model we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three processes: change in hemispheric background, meteorology and anthropogenic emissions (Swedish and other European). The rising low concentrations of near-surface O3 in Sweden are caused by a combination of all three processes, whilst the decrease in the highest O3 concentrations is caused by O3 precursor emissions reductions. While studying the relative impact of anthropogenic emissions changes, we identified systematic differences in the modelled trend compared to observations that must be caused by incorrect trends in the utilised emissions inventory or by too high sensitivity of our model to emissions changes.

scholarly journals Simulations of organic aerosol concentrations during springtime in the Guanzhong Basin, China

2016 ◽  
Vol 16 (15) ◽  
pp. 10045-10061 ◽  
Author(s):  
Tian Feng ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Zhenxing Shen ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Surface Ozone ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Basis Set ◽  
Near Surface ◽  
Guanzhong Basin ◽  
Surrounding Areas ◽  
Background Area

Abstract. The organic aerosol (OA) concentration is simulated in the Guanzhong Basin, China from 23 to 25 April 2013 utilizing the WRF-CHEM model. Two approaches are used to predict OA concentrations: (1) a traditional secondary organic aerosol (SOA) module; (2) a non-traditional SOA module including the volatility basis-set modeling method in which primary organic aerosol (POA) is assumed to be semivolatile and photochemically reactive. Generally, the spatial patterns and temporal variations of the calculated hourly near-surface ozone and fine particle matters agree well with the observations in Xi'an and surrounding areas. The model also yields reasonable distributions of daily PM2.5 and elemental carbon (EC) compared to the filter measurements at 29 sites in the basin. Filter-measured organic carbon (OC) and EC are used to evaluate OA, POA, and SOA using the OC ∕ EC ratio approach. Compared with the traditional SOA module, the non-traditional module significantly improves SOA simulations and explains about 88 % of the observed SOA concentration. Oxidation and partitioning of POA treated as semivolatile constitute the most important pathway for the SOA formation, contributing more than 75 % of the SOA concentrations in the basin. Residential emissions are the dominant anthropogenic OA source, constituting about 50 % of OA concentrations in urban and rural areas and 30 % in the background area. The OA contribution from transportation emissions decreases from 25 % in urban areas to 20 % in the background area, and the industry emission OA contribution is less than 6 %.

scholarly journals Impacts of biogenic and anthropogenic emissions on summertime ozone formation in the Guanzhong Basin, China

2018 ◽  
Vol 18 (10) ◽  
pp. 7489-7507 ◽  
Author(s):  
Nan Li ◽  
Qingyang He ◽  
Jim Greenberg ◽  
Alex Guenther ◽  
Jingyi Li ◽  
...  
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Anthropogenic Sources ◽  
Air Pollution Control ◽  
Near Surface ◽  
Source Contributions ◽  
Surface Measurements ◽  
Individual Source ◽  
Guanzhong Basin ◽  
The Impact

Abstract. This study is the first attempt to understand the synergistic impact of anthropogenic and biogenic emissions on summertime ozone (O3) formation in the Guanzhong (GZ) Basin where Xi'an, the oldest and the most populous city (with a population of 9 million) in northwestern China, is located. Month-long (August 2011) WRF-Chem simulations with different sensitivity experiments were conducted and compared with near-surface measurements. Biogenic volatile organic compounds (VOCs) concentrations was characterized from six surface sites among the Qinling Mountains, and urban air composition was measured in Xi'an city at a tower 100 ma.s. The WRF-Chem control experiment reasonably reproduced the magnitudes and variations of observed O3, VOCs, NOx, PM2.5, and meteorological parameters, with normalized mean biases for each parameter within ±21 %. Subsequent analysis employed the factor separation approach (FSA) to quantitatively disentangle the pure and synergistic impacts of anthropogenic and/or biogenic sources on summertime O3 formation. The impact of anthropogenic sources alone was found to be dominant for O3 formation. Although anthropogenic particles reduced NO2 photolysis by up to 60 %, the anthropogenic sources contributed 19.1 ppb O3 formation on average for urban Xi'an. The abundant biogenic VOCs from the nearby forests promoted O3 formation in urban areas by interacting with the anthropogenic NOx. The calculated synergistic contribution (from both biogenic and anthropogenic sources) was up to 14.4 ppb in urban Xi'an, peaking in the afternoon. Our study reveals that the synergistic impact of individual source contributions to O3 formation should be considered in the formation of air pollution control strategies, especially for big cities in the vicinity of forests.

scholarly journals Impacts of Biogenic Emissions on Summertime Ozone Formation in the Guanzhong Basin, China

2018 ◽  
Author(s):  
Nan Li ◽  
Qingyang He ◽  
Jim Greenberg ◽  
Alex Guenther ◽  
Junji Cao ◽  
...  
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Northwest China ◽  
Anthropogenic Sources ◽  
Biogenic Emissions ◽  
Air Pollution Control ◽  
Near Surface ◽  
Source Contributions ◽  
Guanzhong Basin ◽  
The Impact

Abstract. This study is the first attempt to understand the synergistic impact of anthropogenic and biogenic emissions on summertime ozone (O3) formation in the Guanzhong (GZ) basin where Xi’an, the oldest and the most populous city (with a population of 9 million) in the northwest China, is located. Month-long (August 2011) WRF-Chem simulations with different sensitivity experiments were conducted and compared with near-surface measurements. Biogenic volatile organic compounds (VOCs) concentrations were characterized from 6 surface sites among the Qinling Mountains, and urban air composition was measured in the Xi’an city at a tower 100 m above the surface. The WRF-Chem control experiment reasonably reproduced the magnitudes and variations of observed O3, VOCs, NOx, PM2.5 and meteorological parameters, with normalized mean biases for each parameter within ±21 %. Subsequent analysis employed the factor separation approach (FSA) to quantitatively disentangle the pure and synergistic impacts of anthropogenic and/or biogenic sources on summertime O3 formation. The impact of anthropogenic sources alone was found to be dominant for O3 formation. Although anthropogenic particles reduced NO2 photolysis by up to 60 %, the anthropogenic sources contributed 19.1 ppb O3 formation on average for urban Xi’an. The abundant biogenic VOCs from the nearby forests promoted O3 formation in urban areas by interacting with the anthropogenic NOx. The calculated synergistic contribution (from both biogenic and anthropogenic sources) was up to 14.4 ppb in urban Xi’an, peaking in the afternoon. Our study reveals that the synergistic impact of individual source contributions to O3 formation should be considered in the formation of air pollution control strategies, especially for big cities in the vicinity of forests.

scholarly journals Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

2017 ◽  
Vol 17 (22) ◽  
pp. 13869-13890 ◽  
Author(s):  
Camilla Andersson ◽  
Heléne Alpfjord ◽  
Lennart Robertson ◽  
Per Erik Karlsson ◽  
Magnuz Engardt
Keyword(s):  
Transport Model ◽  
Linear Trend ◽  
Surface Ozone ◽  
Vegetation Indices ◽  
High Sensitivity ◽  
Anthropogenic Emissions ◽  
Data Sets ◽  
Near Surface ◽  
The Impact ◽  
Surface O3

Abstract. We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O3) concentrations for the period 1990–2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using retrospective variational data analysis. The reanalysis data sets show improved performance over the original CTM when compared to independent observations. In one of the reanalyses, we included all available hourly near-surface O3 observations, whilst in the other we carefully selected time-consistent observations. Based on the second reanalysis we investigated statistical aspects of the distribution of the near-surface O3 concentrations, focusing on the linear trend over the 24-year period. We show that high near-surface O3 concentrations are decreasing and low O3 concentrations are increasing, which is reflected in observed improvement of many health and vegetation indices (apart from those with a low threshold). Using the CTM we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three factors: change in hemispheric background concentrations, meteorology and anthropogenic emissions. The rising low concentrations of near-surface O3 in Sweden are caused by a combination of all three factors, whilst the decrease in the highest O3 concentrations is caused by European O3 precursor emissions reductions. While studying the impact of anthropogenic emissions changes, we identified systematic differences in the modeled trend compared to observations that must be caused by incorrect trends in the utilized emissions inventory or by too high sensitivity of our model to emissions changes.

Recurrence Characteristics Analysis of Near-Surface Wind Speed Signal with Different Sampling Frequencies

2014 ◽  
Vol 599-601 ◽  
pp. 1605-1609 ◽  
Author(s):  
Ming Zeng ◽  
Zhan Xie Wu ◽  
Qing Hao Meng ◽  
Jing Hai Li ◽  
Shu Gen Ma
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Recurrence Plot ◽  
Sampling Frequency ◽  
Near Surface ◽  
Gas Leakage ◽  
Time Period ◽  
Characteristics Analysis ◽  
Quantification Analysis

The wind is the main factor to influence the propagation of gas in the atmosphere. Therefore, the wind signal obtained by anemometer will provide us valuable clues for searching gas leakage sources. In this paper, the Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are applied to analyze the influence of recurrence characteristics of the wind speed time series under the condition of the same place, the same time period and with the sampling frequency of 1hz, 2hz, 4.2hz, 5hz, 8.3hz, 12.5hz and 16.7hz respectively. Research results show that when the sampling frequency is higher than 5hz, the trends of recurrence nature of different groups are basically unchanged. However, when the sampling frequency is set below 5hz, the original trend of recurrence nature is destroyed, because the recurrence characteristic curves obtained using different sampling frequencies appear cross or overlapping phenomena. The above results indicate that the anemometer will not be able to fully capture the detailed information in wind field when its sampling frequency is lower than 5hz. The recurrence characteristics analysis of the wind speed signals provides an important basis for the optimal selection of anemometer.

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