scholarly journals Wintertime photochemistry in Beijing: Observations of RO<sub>x</sub> radical concentrations in the North China Plain during the BEST-ONE campaign

2018 ◽  
Author(s):  
Zhaofeng Tan ◽  
Franz Rohrer ◽  
Keding Lu ◽  
Xuefei Ma ◽  
Birger Bohn ◽  
...  
Keyword(s):  
New York ◽  
Primary Production ◽  
North China Plain ◽  
North China ◽  
Oxidative Capacity ◽  
Oh Radicals ◽  
Peroxy Radicals ◽  
The North ◽  
The North China Plain ◽  
Secondary Pollutants

Abstract. The first wintertime in-situ measurements of hydroxyl (OH), hydroperoxy (HO2) and organic peroxy (RO2) radicals (ROx = OH + HO2 + RO2) in combination with observations of total reactivity of OH radicals, kOH in Beijing are presented. The field campaign “Beijing winter finE particle STudy – Oxidation, Nucleation and light Extinctions” (BEST-ONE) was conducted at the suburban site Huairou near Beijing from January to March 2016. It aimed to understand oxidative capacity during wintertime and to elucidate the secondary pollutants formation mechanism in the North China Plain (NCP). OH radical concentrations at noontime ranged from 2.4 × 106 cm−3 in severely polluted air (kOH ~ 27 s−1) to 3.6 × 106 cm−3 in relatively clean air (kOH ~ 5 s−1). These values are nearly two-fold larger than OH concentrations observed in previous winter campaign in Birmingham, Tokyo, and New York City. During this campaign, the total primary production rate of ROx radicals was dominated by the photolysis of nitrous acid accounting for 46 % of the identified primary production pathways for ROx radicals. Other important radical sources were alkene ozonolysis (28 %) and photolysis of oxygenated organic compounds (24 %). A box model was used to simulate the OH, HO2 and RO2 concentrations based on the observations of their long-lived precursors. The model was capable of reproducing the observed diurnal variation of the OH and peroxy radicals during clean days with a factor of 1.5. However, it largely underestimated HO2 and RO2 concentrations by factors up to 5 during pollution episodes. The HO2 and RO2 observed-to-modeled ratios increased with increasing NO concentrations, indicating a deficit in our understanding of the gas-phase chemistry in the high NOx regime. The OH concentrations observed in the presence of large OH reactivities indicate that atmospheric trace gas oxidation by photochemical processes can be highly effective even during wintertime, thereby facilitating the vigorous formation of secondary pollutants.

scholarly journals Wintertime photochemistry in Beijing: observations of RO<sub><i>x</i></sub> radical concentrations in the North China Plain during the BEST-ONE campaign

2018 ◽  
Vol 18 (16) ◽  
pp. 12391-12411 ◽  
Author(s):  
Zhaofeng Tan ◽  
Franz Rohrer ◽  
Keding Lu ◽  
Xuefei Ma ◽  
Birger Bohn ◽  
...  
Keyword(s):  
New York ◽  
Primary Production ◽  
North China Plain ◽  
North China ◽  
Oxidative Capacity ◽  
Oh Radicals ◽  
Peroxy Radicals ◽  
The North ◽  
The North China Plain ◽  
Secondary Pollutants

Abstract. The first wintertime in situ measurements of hydroxyl (OH), hydroperoxy (HO2) and organic peroxy (RO2) radicals (ROx=OH+HO2+RO2) in combination with observations of total reactivity of OH radicals, kOH in Beijing are presented. The field campaign “Beijing winter finE particle STudy – Oxidation, Nucleation and light Extinctions” (BEST-ONE) was conducted at the suburban site Huairou near Beijing from January to March 2016. It aimed to understand oxidative capacity during wintertime and to elucidate the secondary pollutants' formation mechanism in the North China Plain (NCP). OH radical concentrations at noontime ranged from 2.4×106cm-3 in severely polluted air (kOH∼27s-1) to 3.6×106cm-3 in relatively clean air (kOH∼5s-1). These values are nearly 2-fold larger than OH concentrations observed in previous winter campaigns in Birmingham, Tokyo, and New York City. During this campaign, the total primary production rate of ROx radicals was dominated by the photolysis of nitrous acid accounting for 46 % of the identified primary production pathways for ROx radicals. Other important radical sources were alkene ozonolysis (28 %) and photolysis of oxygenated organic compounds (24 %). A box model was used to simulate the OH, HO2 and RO2 concentrations based on the observations of their long-lived precursors. The model was capable of reproducing the observed diurnal variation of the OH and peroxy radicals during clean days with a factor of 1.5. However, it largely underestimated HO2 and RO2 concentrations by factors up to 5 during pollution episodes. The HO2 and RO2 observed-to-modeled ratios increased with increasing NO concentrations, indicating a deficit in our understanding of the gas-phase chemistry in the high NOx regime. The OH concentrations observed in the presence of large OH reactivities indicate that atmospheric trace gas oxidation by photochemical processes can be highly effective even during wintertime, thereby facilitating the vigorous formation of secondary pollutants.

scholarly journals NH<sub>3</sub>-promoted hydrolysis of NO<sub>2</sub> induces explosive growth in HONO

2018 ◽  
Author(s):  
Wanyun Xu ◽  
Ye Kuang ◽  
Chunsheng Zhao ◽  
Jiangchuan Tao ◽  
Gang Zhao ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Ph Value ◽  
Primary Source ◽  
Field Measurements ◽  
Oh Radicals ◽  
The North ◽  
The North China Plain ◽  
First Time ◽  
Hydrolysis Of

Abstract. The study of atmospheric nitrous acid (HONO), which is the primary source of OH radicals, is crucial to atmospheric photochemistry and heterogeneous chemical processes. The heterogeneous NO2 chemistry under haze conditions was pointed out to be one of the missing sources of HONO on the North China Plain, producing sulfate and nitrate in the process. However, controversy exists between various proposed mechanisms, mainly debating on whether SO2 directly takes part in the HONO production process and what roles NH3 and the pH value play in it. In this paper, never before seen explosive HONO production (maximum rate: 16 ppb/hour) was reported and evidence was found for the first time in field measurements during fog episodes (usually with pH > 5) and haze episodes under high relative humidity (usually with pH 

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 Parameterized reactivity of hydroxy radical, ozone, nitrate radical and atmospheric oxidation capacity during summer at a suburban site between Beijing and Tianjin

2019 ◽  
Author(s):  
Yuan Yang ◽  
Yonghong Wang ◽  
Dan Yao ◽  
Dongshen Ji ◽  
Jie sun ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Oxidative Capacity ◽  
Oh Radicals ◽  
The North ◽  
Direct Observations ◽  
No3 Radical ◽  
Diurnal Profile ◽  
Suburban Site ◽  
Loss Rates

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 resulted from anthropogenic and biogenic origins. To estimate the self-cleaning capacity of the atmosphere, the reactivities of OH, NO3 and O3 was comprehensively analyzed for the first time 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 reactivity, ROHtotal, NO3 reactivity, RNO3total, and O3 reactivity, RO3total, at the site varied from 8.5 s−1 to 68.1 s−1, 0.7 s−1 to 27.5 s−1, and 3.3 × 10−4 s−1 to 1.8 × 10−2 s−1 with campaign-averaged values of 25.6 ± 9.7 s−1, 2.2 ± 2.6 s−1 and 1.2 ± 1.7 × 10-3 s−1 (± standard deviation), respectively. NOx (NO + NO2) were by far the main contributors to the ROHtotal, RNO3total and RO3total, with average values of 47, 99 and 99 %, respectively. Isoprene dominated the OH and NO3 reactivity towards TVOCs (ROHTVOCs and RNO3TVOCs), accounting for 40 % and 77 %, respectively. However, alkenes dominated the O3 reactivity towards TVOCs (RO3TVOCs), representing 66 % of RO3total. ROHtotal, RNO3total and RO3total displayed a similar diurnal variation with the lowest during the afternoon and the highest during rush hours, and the diurnal profile of NOx appears to be the major driver for the diurnal profiles of ROHtotal, RNO3total and RO3total. The calculated atmospheric oxidative capacity (AOC) was up to 4.4 × 108 molecules cm−3 s−1 with campaign-averaged values of 3.1 × 107 molecules cm−3 s−1 dominated by OH radicals (2.9 × 107 molecule cm−3 s−1, 95 %), O3 (1.2 × 106 molecule cm−3 s−1, 4 %) and NO3 radicals (1.7 × 105 molecule cm−3 s−1, 1 %). The reaction with OH radicals was the dominant volatile organic compounds (VOCs) loss except for trans-2-butene, cis-2-butene, trans-2-pentene, propylene, 1-butene, 1-pentene, 1-hexene, acetone and styrene, where the reaction with O3 was more important for their loss rates. Compared with anthropogenic hydrocarbons, the oxidation by the NO3 radical was more important for the nighttime integral of isoprene loss rates. Overall, the present study may provide some useful suggestions for VOC pollution control in the Xianghe and North China Plain. To better understanding the trace gas reactivity and AOC, further studies, especially direct observations of the OH and NO3 radical concentrations and their reactivities, are required.

scholarly journals Comparison of multiple models for estimating gross primary production using remote sensing data and fluxnet observations

2015 ◽  
Vol 368 ◽  
pp. 75-80
Author(s):  
S. Wang ◽  
X. Mo
Keyword(s):  
Primary Production ◽  
Crop Production ◽  
North China Plain ◽  
North China ◽  
Gross Primary Production ◽  
Remote Sensing Data ◽  
Growing Season ◽  
The North ◽  
The North China Plain ◽  
Eddy Covariance Measurements

Abstract. In this study, gross primary production (GPP) estimated from a temperature and greenness (TG) model, a greenness and radiation (GR) model, a vegetation photosynthesis model (VPM), and a MODIS product have been compared with eddy covariance measurements in cropland during 2003–2005. Results showed that the determination coefficients (R2) between fluxnet GPP and estimated GPP were all greater than 0.74, indicating that all these models offered reliable estimates of GPP. We also found that the VPM-based GPP estimates performed a bit better (R2 is 0.82, and RMSE is 16.75 gC m−2 (8 day)−1) than other models, mainly due to its comprehensive consideration of the stresses from light, temperature and water. The actual GPP was overestimated in the non-growing season and underestimated in the growing season by MOD_GPP. The validation confirms that the above three models may be used to estimate crop production in the North China Plain, but there are still significant uncertainties.

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