scholarly journals North China Plain as a hot spot of ozone pollution exacerbated by extreme high temperatures

2021 ◽  
Author(s):  
Pinya Wang ◽  
Yang Yang ◽  
Huimin Li ◽  
Lei Chen ◽  
Ruijun Dang ◽  
...  
Keyword(s):  
High Temperature ◽  
North China Plain ◽  
North China ◽  
Transport Model ◽  
Hot Spot ◽  
Large Population ◽  
Atmospheric Condition ◽  
Pollutant Emission ◽  
Chemical Production ◽  
Extreme High Temperature

Abstract. A large population in China has been increasingly exposed to both severe ozone (O3) pollution and extreme heat under global warming. Here, the spatiotemporal characteristics of coupled extremes in surface O3 and heat (OPCs) over China are investigated using surface observations, a process-based chemical transport model (GEOS-Chem), and multi-model simulations from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). North China Plain (NCP, 37–41° N; 114–120° E) is identified as a hot spot of OPCs, where more than half of the O3 pollution days are accompanied by high temperature extremes. OPCs over NCP exceed 40 days during 2014–2019, exhibiting an increasing trend. Both O3 concentrations and temperatures are elevated during OPCs compared to O3 pollution days occurring individually (OPIs). Therefore, OPCs impose more severe health impacts to human than OPIs, but the stronger health effects are mainly driven by the higher temperatures. GEOS-Chem simulations further reveal that enhanced chemical production resulting from hot and stable atmospheric condition under anomalous weather pattern primarily contributes to the exacerbated O3 levels during OPCs. In the future, CMIP6 projections suggest increased occurrences of OPCs over NCP in the middle of this century, but by the end of this century, OPCs may decrease or increase depending on the pollutant emission scenarios. However, for all future scenarios, extreme high temperature will play an increasingly important role in modulating O3 pollution in a warming climate.

scholarly journals A typical weather pattern for the ozone pollution events in North China

2019 ◽  
Author(s):  
Cheng Gong ◽  
Hong Liao
Keyword(s):  
North China ◽  
Transport Model ◽  
Lower Troposphere ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Ozone Pollution ◽  
Chemical Production ◽  
Weather Pattern ◽  
Pollution Events

Abstract. Ground-level observations, reanalyzed meteorological fields and a 3-D global chemical and transport model (GEOS-Chem) were applied in this study to investigate ozone (O3) pollution events (OPEs) in North China (36.5° N–40.5° N, 114.5° E–119.5° E) during 2014–2017. Ozone pollution days (OPDs) were defined as days with maximum daily averaged 8-h (MDA8) concentrations over North China larger than 160 μg m−3, and OPEs were defined as periods with 3 or more consecutive OPDs. Observations showed that there were 167 OPDs and 27 OPEs in North China during 2014–2017, in which 123 OPDs and 21 OPEs occurred in May–July. We found that OPEs in North China occurred under a typical weather pattern with high daily maximum temperature (Tmax), low relative humidity (RH), anomalous southerlies and divergence in the lower troposphere, an anomalous high-pressure system at 500 hPa and an anomalous downward air flow from 500 hPa to the surface. Under such a weather pattern, chemical production of O3 was high between 800 and 900 hPa, which was then transported downward to enhance O3 pollution at the surface. A standardized index I_OPE was defined by applying four key meteorological parameters, including Tmax, RH, meridional winds at 850 hPa (V850) and zonal winds at 500 hPa (U500). I_OPE can capture approximately 80 % of the observed OPDs and OPEs, which has implications for forecasting OPEs in North China.

scholarly journals Atmospheric reactivity and oxidation capacity during summer at a suburban site between Beijing and Tianjin

2020 ◽  
Vol 20 (13) ◽  
pp. 8181-8200
Author(s):  
Yuan Yang ◽  
Yonghong Wang ◽  
Putian Zhou ◽  
Dan Yao ◽  
Dongsheng Ji ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Transport Model ◽  
Oh Radicals ◽  
Chemical Transport Model ◽  
Oxidation Capacity ◽  
The North ◽  
The North China Plain ◽  
Atmospheric Reactivity ◽  
Suburban Site

Abstract. Hydroxyl (OH) radicals, nitrate (NO3) radicals and ozone (O3) play central roles in the troposphere because they control the lifetimes of many trace gases that result from anthropogenic and biogenic origins. To estimate the air chemistry, the atmospheric reactivity and oxidation capacity were comprehensively analyzed based on a parameterization method at a suburban site in Xianghe in the North China Plain from 6 July 2018 to 6 August 2018. The total OH, NO3 and O3 reactivities at the site varied from 9.2 to 69.6, 0.7 to 27.5 and 3.3×10-4 to 1.8×10-2 s−1 with campaign-averaged values of 27.5±9.7, 2.2±2.6 and 1.2±1.7×10-3 s−1 (± standard deviation), respectively. NOx (NO+NO2) was by far the main contributor to the reactivities of the three oxidants, with average values of 43 %–99 %. Alkenes dominated the OH, NO3 and O3 reactivities towards total nonmethane volatile organic compounds (NMVOCs), accounting for 42.9 %, 77.8 % and 94.0 %, respectively. The total OH, NO3 and O3 reactivities displayed similar diurnal variations with the lowest values during the afternoon but the highest values during rush hours, and the diurnal profile of NOx appears to be the major driver for the diurnal profiles of the reactivities of the three oxidants. A box model (a model to Simulate the concentrations of Organic vapors, Sulfuric Acid and Aerosols; SOSAA) derived from a column chemical transport model was used to simulate OH and NO3 concentrations during the observation period. The calculated atmospheric oxidation capacity (AOC) reached 4.5×108 moleculescm-3s-1, with a campaign-averaged value of 7.8×107 moleculescm-3s-1 dominated by OH (7.7×107 moleculescm-3s-1, 98.2 %), O3 (1.2×106 moleculescm-3s-1, 1.5 %) and NO3 (1.8×105 moleculescm-3s-1, 0.3 %). Overall, the integration of OH, NO3 and O3 reactivities analysis could provide useful insights for NMVOC pollution control in the North China Plain. We suggest that further studies, especially direct observations of OH and NO3 radical concentrations and their reactivities, are required to better understand trace gas reactivity and AOC.

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.

scholarly journals Rapid SO<sub>2</sub> emission reductions significantly increase tropospheric ammonia concentrations over the North China Plain

2018 ◽  
Vol 18 (24) ◽  
pp. 17933-17943 ◽  
Author(s):  
Mingxu Liu ◽  
Xin Huang ◽  
Yu Song ◽  
Tingting Xu ◽  
Shuxiao Wang ◽  
...  
Keyword(s):  
Gas Phase ◽  
North China Plain ◽  
North China ◽  
Transport Model ◽  
Lower Troposphere ◽  
Nox Emissions ◽  
So2 Emission ◽  
Emission Reductions ◽  
The North ◽  
The North China Plain

Abstract. The North China Plain has been identified as a significant hotspot of ammonia (NH3) due to extensive agricultural activities. Satellite observations suggest a significant increase of about 30 % in tropospheric gas-phase NH3 concentrations in this area during 2008–2016. However, the estimated NH3 emissions decreased slightly by 7 % because of changes in Chinese agricultural practices, i.e., the transition in fertilizer types from ammonium carbonate fertilizer to urea, and in the livestock rearing system from free-range to intensive farming. We note that the emissions of sulfur dioxide (SO2) have rapidly declined by about 60 % over the recent few years. By integrating measurements from ground and satellite, a long-term anthropogenic NH3 emission inventory, and chemical transport model simulations, we find that this large SO2 emission reduction is responsible for the NH3 increase over the North China Plain. The simulations for the period 2008–2016 demonstrate that the annual average sulfate concentrations decreased by about 50 %, which significantly weakens the formation of ammonium sulfate and increases the average proportions of gas-phase NH3 within the total NH3 column concentrations from 26 % (2008) to 37 % (2016). By fixing SO2 emissions of 2008 in those multi-year simulations, the increasing trend of the tropospheric NH3 concentrations is not observed. Both the decreases in sulfate and increases in NH3 concentrations show highest values in summer, possibly because the formation of sulfate aerosols is more sensitive to SO2 emission reductions in summer than in other seasons. Besides, the changes in NOx emissions and meteorological conditions both decreased the NH3 column concentrations by about 3 % in the study period. Our simulations suggest that the moderate reduction in NOx emissions (16 %) favors the formation of particulate nitrate by elevating ozone concentrations in the lower troposphere.

scholarly journals Modeling Ozone Source Apportionment and Performing Sensitivity Analysis in Summer on the North China Plain

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 992
Author(s):  
Yujing Zhang ◽  
Yuncheng Zhao ◽  
Jie Li ◽  
Qizhong Wu ◽  
Hui Wang ◽  
...  
Keyword(s):  
Air Quality ◽  
Source Apportionment ◽  
North China Plain ◽  
North China ◽  
Transport Model ◽  
Fine Particulate Matter ◽  
Hebei Province ◽  
Chemical Transport Model ◽  
The North ◽  
The North China Plain

In recent years, air quality issues due to fine particulate matter have been sufficiently treated. However, ozone (O3) has now become the primary pollutant in summer on the North China Plain (NCP). In this study, a three-dimensional chemical transport model (the Nested Air Quality Prediction Model System, NAQPMS) coupled with an online source apportionment module was applied to investigate the sources of O3 pollution over the NCP. Generally, the NAQPMS adequately captured the observed spatiotemporal features of O3 during the period of July 1st to August 31st in 2017 on the NCP. The results of the source apportionment indicated that the contributions of local emissions and transport from the NCP accounted for the largest proportion of O3, with magnitudes of 25% and 39%, respectively. Compared with those in the average monthly results, the local contribution and regional transport during O3 episodes on the NCP increased by 7% and 10%, respectively. Based on sensitivity tests, two thresholds of the sensitivity indicator P(H2O2)/P(HNO3) were detected, at 0.08 and 0.2. Ozone formation in the urban sites of Beijing, Tianjin, and the southern part of Hebei Province was controlled by VOCs, while the other sites were mainly controlled by NOX. Biogenic emissions contributed approximately 18% to O3 formation in July in the southwestern part of Hebei Province.

Analysis of Extreme Temperature Events in North China Based on EMD Method

2013 ◽  
Vol 295-298 ◽  
pp. 854-858 ◽  
Author(s):  
Xiao Ying Chen ◽  
Yi Min Zhu ◽  
Lin Lin Xia ◽  
Wei Xing Zhang
Keyword(s):  
High Temperature ◽  
Temperature Variation ◽  
North China ◽  
Southern Oscillation ◽  
Extreme Temperature ◽  
Temporal Variations ◽  
Mode Decomposition ◽  
Extreme High Temperature ◽  
Spatio Temporal ◽  
Emd Method

The spatio-temporal variations of extreme temperature in North China during 1954-2008 are analyzed based on Empirical Mode Decomposition (EMD) method. The results show that the interannual-to-interdecadal variabilities of extreme temperature in North China. 3-4 years and 7-8 years interannual variabilities as well as a decreasing trend are dominant while 15 years oscillation takes second place in the extreme low temperature variation. Meanwhile, 3-4 year interannual variabilities are dominant while 6-7 years, 14-15 years 40 years oscillation as well as an increasing trend takes second place in the extreme high temperature variation. 3-4 years interannual variabilities of both extreme low and high temperature are closely related to El Nino-Southern Oscillation (ENSO), while interdecadal variabilities and trend of extreme temperature are obviously associated with the Pacific Decadal Oscillation (PDO). Besides, PDO plays an important role on interdecadal modulation of interannual to decadal variabilities of extreme temperature in North China.

scholarly journals Spatiotemporal Variations and Uncertainty in Crop Residue Burning Emissions over North China Plain: Implication for Atmospheric CO2 Simulation

2021 ◽  
Vol 13 (19) ◽  
pp. 3880
Author(s):  
Yu Fu ◽  
Hao Gao ◽  
Hong Liao ◽  
Xiangjun Tian
Keyword(s):  
Air Quality ◽  
Biomass Burning ◽  
Crop Residue ◽  
North China Plain ◽  
North China ◽  
Transport Model ◽  
Spatial Uncertainty ◽  
Burned Area ◽  
Crop Residue Burning ◽  
The Impact

Large uncertainty exists in the estimations of greenhouse gases and aerosol emissions from crop residue burning, which could be a key source of uncertainty in quantifying the impact of agricultural fire on regional air quality. In this study, we investigated the crop residue burning emissions and their uncertainty in North China Plain (NCP) using three widely used methods, including statistical-based, burned area-based, and fire radiative power-based methods. The impacts of biomass burning emissions on atmospheric carbon dioxide (CO2) were also examined by using a global chemical transport model (GEOS-Chem) simulation. The crop residue burning emissions were found to be high in June and followed by October, which is the harvest times for the main crops in NCP. The estimates of CO2 emission from crop residue burning exhibits large interannual variation from 2003 to 2019, with rapid growth from 2003 to 2012 and a remarkable decrease from 2013 to 2019, indicating the effects of air quality control plans in recent years. Through Monte Carlo simulation, the uncertainty of each estimation was quantified, ranging from 20% to 70% for CO2 emissions at the regional level. Concerning spatial uncertainty, it was found that the crop residue burning emissions were highly uncertain in small agricultural fire areas with the maximum changes of up to 140%. While in the areas with large agricultural fire, i.e., southern parts of NCP, the coefficient of variation mostly ranged from 30% to 100% at the gridded level. The changes in biomass burning emissions may lead to a change of surface CO2 concentration during the harvest times in NCP by more than 1.0 ppmv. The results of this study highlighted the significance of quantifying the uncertainty of biomass burning emissions in a modeling study, as the variations of crop residue burning emissions could affect the emission-driven increases in CO2 and air pollutants during summertime pollution events by a substantial fraction in this region.

scholarly journals The influence of natural and anthropogenic secondary sources on the glyoxal global distribution

2008 ◽  
Vol 8 (16) ◽  
pp. 4965-4981 ◽  
Author(s):  
S. Myriokefalitakis ◽  
M. Vrekoussis ◽  
K. Tsigaridis ◽  
F. Wittrock ◽  
A. Richter ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Transport Model ◽  
Hot Spot ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Chemical Production ◽  
Secondary Sources ◽  
Voc Oxidation ◽  
Primary Emissions ◽  
The Impact

Abstract. Glyoxal, the smallest dicarbonyl, which has recently been observed from space, is expected to provide indications on volatile organic compounds (VOC) oxidation and secondary aerosol formation in the troposphere. Glyoxal (CHOCHO) is known to be mostly of natural origin and is produced during biogenic VOC oxidation. However, a number of anthropogenically emitted hydrocarbons, like acetylene and aromatics, have been positively identified as CHOCHO precursors. The present study investigates the contribution of pollution to the CHOCHO levels by taking into account the secondary chemical formation of CHOCHO from precursors emitted from biogenic, anthropogenic and biomass burning sources. The impact of potential primary land emissions of CHOCHO is also investigated. A global 3-dimensional chemistry transport model of the troposphere (TM4-ECPL) able to simulate the gas phase chemistry coupled with all major aerosol components is used. The secondary anthropogenic contribution from fossil fuel and industrial VOCs emissions oxidation to the CHOCHO columns is found to reach 20–70% in the industrialized areas of the Northern Hemisphere and 3–20% in the tropics. This secondary CHOCHO source is on average three times larger than that from oxidation of VOCs from biomass burning sources. The chemical production of CHOCHO is calculated to equal to about 56 Tg y−1 with 70% being produced from biogenic hydrocarbons oxidation, 17% from acetylene, 11% from aromatic chemistry and 2% from ethene and propene. CHOCHO is destroyed in the troposphere primarily by reaction with OH radicals (23%) and by photolysis (63%), but it is also removed from the atmosphere through wet (8%) and dry deposition (6%). Potential formation of secondary organic aerosol through CHOCHO losses on/in aerosols and clouds is neglected here due to the significant uncertainties associated with the underlying chemistry. The global annual mean CHOCHO burden and lifetime in the model domain are estimated to be 0.02 Tg (equal to the global burden seen by SCIAMACHY over land for the year 2005) and about 3 h, respectively. The model results are compared with satellite observations of CHOCHO columns. When accounting only for the secondary sources of CHOCHO in the model, the model underestimates CHOCHO columns observed by satellites. This is attributed to an overestimate of CHOCHO sinks or a missing global source of about 20 Tg y−1. Using the current primary emissions of CHOCHO from biomass burning together with the anthropogenic combustion sources of about 7 Tg y−1 leads to an overestimate by the model over hot spot areas.

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