scholarly journals Seasonal characteristics of atmospheric peroxyacetyl nitrate (PAN) in a coastal city of Southeast China: Explanatory factors and photochemical effects

2021 ◽  
Author(s):  
Taotao Liu ◽  
Gaojie Chen ◽  
Jinsheng Chen ◽  
Lingling Xu ◽  
Mengren Li ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Formation Rate ◽  
Additive Model ◽  
Meteorological Conditions ◽  
Photochemical Reactions ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution ◽  
Explanatory Factors ◽  
Seasonal Characteristics ◽  
Intensive Observation

Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical pollution can redistribute NOx and modulate O3 production. Coupled with the observation-based model (OBM) and a generalized additive model (GAM), the intensive observation campaigns were conducted to reveal the pollution characteristics of PAN and its impact on O3, the contributions of influencing factors to PAN formation were also quantified in this paper. The F-values of GAM results reflecting the importance of the influencing factors showed that ultraviolet radiation (UV, F-value = 60.64), Ox (Ox = NO2+O3, 57.65), and air temperature (T, 17.55) were the main contributors in the PAN pollution in spring, while the significant effects of Ox (58.45), total VOCs (TVOCs, 21.63) and T (20.46) were found in autumn. The PAN formation rate in autumn was 1.58 times higher than that in spring, relating to the intense photochemical reaction and meteorological conditions. Without considering the transformation of peroxyacetyl radical (PA) and PAN, acetaldehyde contributed to the dominant production of PA (46 ± 4 %), followed by methylglyoxal (28 ± 3 %) and radical cycling (19 ± 3 %). The PAN formation was highly VOC-sensitive, and sufficient NOx (compared with VOCs abundance) would not be the limited factor for atmospheric photochemistry. PAN could promote or inhibit O3 formation under high or low ROx levels, respectively. The PAN promoting O3 formation mainly occurred during the periods of 11:00–16:00 (local time) when the favorable meteorological conditions (high UV and T) stimulated the photochemical reactions to offer ROx radicals, which accounted for 17 % of the whole monitoring periods in spring and 31 % in autumn. In this study, the formation mechanism of PAN and its effect on ozone were identified, which might be helpful to improve the scientific understanding of photochemical pollution in coastal areas.

scholarly journals Analysis of influencing factors on soil Zn content using generalized additive model

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Yan Jiang ◽  
Wen-Wu Gao ◽  
Jin-Ling Zhao ◽  
Qian Chen ◽  
Dong Liang ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Zn Content ◽  
Soil Zn

scholarly journals OMI-observed HCHO in Shanghai, China during 2010–2019 and ozone sensitivity inferred by improved HCHO / NO<sub>2</sub> ratio

2021 ◽  
Author(s):  
Danran Li ◽  
Shanshan Wang ◽  
Ruibin Xue ◽  
Jian Zhu ◽  
Sanbao Zhang ◽  
...  
Keyword(s):  
Control Strategies ◽  
Photochemical Reactions ◽  
Anthropogenic Source ◽  
Ozone Monitoring Instrument ◽  
Temporal And Spatial Distribution ◽  
Vertical Column ◽  
Ozone Sensitivity ◽  
Seasonal Characteristics ◽  
Long Term Observation ◽  
And Control

Abstract. In recent years, satellite remote sensing has been increasingly used in the long-term observation of ozone (O3) precursors and its formation regime. In this work, formaldehyde (HCHO) data from Ozone Monitoring Instrument (OMI) were used to analyse the temporal and spatial distribution of HCHO vertical column densities (VCDs) in Shanghai from 2010 to 2019. HCHO VCDs exhibited the highest value in summer and the lowest in winter, the high-VCD concentrated in western Shanghai. Temperature largely influence HCHO by affecting the biogenic emissions and photochemical reactions, and industry was the major anthropogenic source. The satellite observed formaldehyde to nitrogen dioxide ratio (FNRSAT) reflects that the O3 formation regime had significant seasonal characteristics and gradually manifested as transitional ozone formation regime dominated in Shanghai. The uneven distribution in space was mainly reflected as the higher FNRSAT and surface O3 concentration in rural area. To compensate the shortcoming of FNRSAT that it can only characterize O3 formation around satellite overpass time, correction of FNRSAT was implemented with hourly surface FNR and O3 data. After correction, O3 formation regime showed the trend moving towards VOC-limited in both time and space, and regime indicated by FNRSAT can better reflect O3 formation for a day. This study can help us better understand HCHO characteristics and O3 formation regime in Shanghai, and also provide a method to improve FNRSAT for characterizing O3 formation in a day, which will be significant for developing O3 prevention and control strategies.

scholarly journals Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998–2002

2004 ◽  
Vol 4 (3) ◽  
pp. 3535-3563
Author(s):  
H. Vehkamäki ◽  
M. Dal Maso ◽  
T. Hussein ◽  
R. Flanagan ◽  
A. Hyvärinen ◽  
...  
Keyword(s):  
Growth Rate ◽  
Biological Activity ◽  
Gas Phase ◽  
Formation Rate ◽  
Particle Formation ◽  
Meteorological Conditions ◽  
Air Masses ◽  
Atmospheric Particle ◽  
Starting Time ◽  
Finnish Lapland

Abstract. We have identified 147 clear 8 nm diameter particle formation events at the SMEAR I station in Värriö, northern Finland during calendar years 1998–2002. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different gas phase species concentrations and pre-existing particle concentrations as well as various meteorological conditions. Most of the events occurred during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8 nm particle formation rates were around 0.1/cm3s, and they were uncorrelated with growth rates that vary between 0.5 and 10 nm/h. The air masses, which had clearly elevated sulphur dioxide concentrations above 1.6 ppb came, as expected, from the direction of Nikel and Monschegorsk smelteries. Only 15 formation events can be explained by the pollution plume from these sources.

Statistical modelling of combined ozone-temperature events in Europe

2020 ◽  
Author(s):  
Sally Jahn ◽  
Elke Hertig
Keyword(s):  
Human Health ◽  
Air Temperature ◽  
Statistical Modelling ◽  
Meteorological Conditions ◽  
Photochemical Reactions ◽  
Air Pollutant ◽  
Urban Traffic ◽  
Ozone Formation ◽  
Regional Patterns ◽  
Wide Range

&lt;p&gt;Air pollution as well as high air temperature both pose a large risk to human health in Europe. High temperature levels are associated with an exceptionally high mortality rate, only representing the extreme end of a wide range of possible health effects. Tropospheric ozone, a secondary air pollutant, is primarily built by photochemical reactions under solar radiation with the involvement of precursor gases including nitrogen oxides, carbon monoxide, methane, and non-methane volatile organic compounds. Due to the specific characteristics of ozone formation, high levels of ozone and temperature often coincide, posing an even intensified threat to human health.&lt;/p&gt;&lt;p&gt;The current scientific work focuses on the co-occurrence of these two health stressors as well as their underlying meteorological conditions. A subset of European ozone (AirBase_v8, EEA) and temperature (ECA&amp;D) stations is selected for analysis based on individual station locations and data coverage. Taking into account different settings of air substances concentrations (urban, outer conurbation area, rural regions), these stations are classified and grouped by station type and area type resulting in five distinct station classes: urban traffic, urban background, suburban background, rural background and rural industrial.&lt;/p&gt;&lt;p&gt;Maximum daily 8-hour average ozone values (MDA8O3, EEA), observed daily maximum air temperatures (TX, ECA&amp;D) and meteorological variables (from ERA5, ECMWF) form the data basis for model building. Current thresholds and extreme definitions e.g. based on WHO air quality guidelines or high percentiles (75&lt;sup&gt;th&lt;/sup&gt; and 90&lt;sup&gt;th&lt;/sup&gt;) are examined and discussed to describe elevated levels of these variables and to finally define combined ozone-temperature events.&lt;/p&gt;&lt;p&gt;Possible regional patterns as well as disparities between urban and rural areas regarding the specific settings for ozone formation as well as varying meteorological mechanisms for the occurrence of combined ozone-temperature events are closely examined. The methodological focus is primary on statistical modelling, the application and comparison of varying multivariate statistical approaches and different machine learning methods, e.g. various regression analyses using shrinkage methods or random forests. Consequently, statistical models are generated to analyse the influence of meteorological conditions on the occurrence of combined ground-level ozone and temperature events along with the identification of primary key factors (e.g. ozone persistence or larger-scale air temperature and wind conditions) at each specific location.&lt;/p&gt;&lt;p&gt;Furthermore, frequency and intensity changes of combined ozone-temperate events in the scope of global warming are assessed. Thus, projections of these co-occurring events under the constraints of ongoing climate change until the end of the 21st century are analysed by integrating projections of general circulation models into the statistical modelling process.&lt;/p&gt;

scholarly journals Dynamics of the Typhoon Haitang Related High Ozone Episode over Hong Kong

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaolin Wei ◽  
Ka-se Lam ◽  
Chunyan Cao ◽  
Hui Li ◽  
Jiajia He
Keyword(s):  
Hong Kong ◽  
Air Quality ◽  
Dynamic Process ◽  
Meteorological Conditions ◽  
Photochemical Reactions ◽  
Physical Factors ◽  
Photochemical Smog ◽  
Pearl River Delta Region ◽  
Local Circulation ◽  
Ozone Episode

It has been previously established that photochemical smog occurring in the Pearl River Delta Region (PRD) was associated with stagnant meteorological conditions. However, the photochemical smog (17 July to 20 July 2005) induced by typhoon Haitang was associated with moderate wind speed and nonstagnant meteorological conditions. The dynamic process of this ozone episode was studied using an integrated numerical model, that is, a mesoscale meteorological model and Community Multiscale Air Quality (CMAQ) model. Model performance has been evaluated using both ground-based meteorological and air quality observations. Analysis of simulated wind fields and ozone budget has been performed. This dynamic process is summarized into three physical factors. First, the westerly wind placed Hong Kong directly downwind of the PRD emissions. Second, the convergence of wind flow stimulated a vertical local circulation near the surface layer. This recirculation allowed primary and secondary pollutants to accumulate. Third, the conditions of high air temperature and low humidity resulted in active photochemical reactions. These combined effects resulted in the formation of high ozone in this episode.

scholarly journals Retrieval of Urban Aerosol Optical Depth from Landsat 8 OLI in Nanjing, China

2021 ◽  
Vol 13 (3) ◽  
pp. 415
Author(s):  
Yangyang Jin ◽  
Zengzhou Hao ◽  
Jian Chen ◽  
Dong He ◽  
Qingjiu Tian ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Absolute Error ◽  
Meteorological Conditions ◽  
Landsat 8 ◽  
Landsat 8 Oli ◽  
Large Area ◽  
The North ◽  
Deep Blue ◽  
Seasonal Characteristics

Aerosol is an essential parameter for assessing the atmospheric environmental quality, and accurate monitoring of the aerosol optical depth (AOD) is of great significance in climate research and environmental protection. Based on Landsat 8 Operational Land Imager (OLI) images and MODIS09A1 surface reflectance products under clear skies with limited cloud cover, we retrieved the AODs in Nanjing City from 2017 to 2018 using the combined Dark Target (DT) and Deep Blue (DB) methods. The retrieval accuracy was validated by in-situ CE-318 measurements and MOD04_3K aerosol products. Furthermore, we analyzed the spatiotemporal distribution of the AODs and discussed a case of high AOD distribution. The results showed that: (1) Validated by CE-318 and MOD04_3K data, the correlation coefficient (R), root mean square error (RMSE), and mean absolute error (MAE) of the retrieved AODs were 0.874 and 0.802, 0.134 and 0.188, and 0.099 and 0.138, respectively. Hence, the combined DT and DB algorithms used in this study exhibited a higher performance than the MOD04_3K-obtained aerosol products. (2) Under static and stable meteorological conditions, the average annual AOD in Nanjing was 0.47. At the spatial scale, the AODs showed relatively high values in the north and west, low in the south, and the lowest in the center. At the seasonal scale, the AODs were highest in the summer, followed by spring, winter, and autumn. Moreover, changes were significantly higher in the summer than in the other three seasons, with little differences among spring, autumn, and winter. (3) Based on the spatial and seasonal characteristics of the AOD distribution in Nanjing, a case of high AOD distribution caused by a large area of external pollution and local meteorological conditions was discussed, indicating that it could provide extra details of the AOD distribution to analyze air pollution sources using fine spatial resolution like in the Landsat 8 OLI.

scholarly journals Measurement report: Fast photochemical production of peroxyacetyl nitrate (PAN) over the rural North China Plain during haze events in autumn

2021 ◽  
Vol 21 (23) ◽  
pp. 17995-18010
Author(s):  
Yulu Qiu ◽  
Zhiqiang Ma ◽  
Ke Li ◽  
Mengyu Huang ◽  
Jiujiang Sheng ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Cold Season ◽  
Rural Site ◽  
Dominant Factor ◽  
Urban Region ◽  
Chemical Production ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution ◽  
Acetaldehyde Oxidation

Abstract. Photochemical pollution over the North China Plain (NCP) is attracting much concern. We usually view peroxyacetyl nitrate (PAN) as the second most important photochemical pollutant featuring high mixing ratios during warm seasons. Our observations at a background site in the NCP identified high PAN concentrations, even during haze events in autumn. The substantial increasing ratios of PAN, by 244 % and 178 %, over the morning hours (08:00–12:00 local time) on 20 and 25 October 2020 were 10.6 and 7.7 times larger than those on clean days. Polluted days are characterized by higher temperature, higher humidity, and anomalous southerly winds compared with clean days. Enhanced local photochemistry has been identified as being the dominant factor that controls the PAN increase in the morning at the rural site, as the time when prevailing wind turns to a southerly wind is too late to promote direct transport of PAN from the polluted urban region. By removing the effect of direct transport of PAN, we provide a quantitative assessment of net PAN chemical production rate of 0.45 ppb h−1 for the mornings of polluted days, also demonstrating the strong local photochemistry. Using observations and calculated photolysis rates, we find that acetaldehyde oxidation by hydroxyl radical (OH) is the primary pathway of peroxyacetyl radical formation at the rural site. Acetaldehyde concentrations and production rates of HOx (HOx= OH + HO2) on polluted days are 2.8 and 2 times as large as those on clean days, leading to a remarkable increase in PAN in the morning. Formaldehyde (HCHO) photolysis dominates the daytime HOx production, thus contributing to fast photochemistry of PAN. Our observational results suggest the cause of a rapid increase in PAN during haze events in autumn at a rural site of the NCP and provide evidence of important role of HCHO photolysis in secondary pollutants at lower nitrogen oxide emissions. This highlights the urgency of carrying out strict volatile organic compound controls over the NCP during the cold season and not just in summer.

Sign in / Sign up

Export Citation Format

Share Document