Heterogeneous formation of HONO and its impacts on haze formation in the YRD region of China

2020 ◽  
Author(s):  
Jun Zheng ◽  
Xiaowen Shi ◽  
Yan Ma
Keyword(s):  
Heterogeneous Reaction ◽  
Particle Surface ◽  
Ground Surface ◽  
Yangtze River Delta ◽  
Heterogeneous Reactions ◽  
Atmospheric Oxidation ◽  
Industrial Zone ◽  
Particle Surface Area ◽  
Oxidation Capacity ◽  
The Yrd

<p>A suite of instruments were deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NO<sub>x</sub>= NO + NO<sub>2</sub>), carbon monoxide (CO), ozone (O<sub>3</sub>), volatile organic compounds (VOCs, including formaldehyde (HCHO)) and meteorological parameters near a typical industrial zone in Nanjing of the Yangtze River Delta region, China. High levels of HONO were detected using a wet chemistry-based method. HONO ranged from 0.03-7.04 ppbv with an average of 1.32 ±0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundreds of pptv on average, which cannot be explained by the homogeneous OH + NO reaction (P<sub>OH+NO</sub>) alone, especially during periods with high loadings of particulate matters (PM<sub>2.5</sub>). The HONO chemistry and its impact on atmospheric oxidation capacity in the study area were further investigated using a MCM-box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), followed by ozonolysis of alkenes (3.94×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), photolysis of O<sub>3</sub>(2.46×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>) and photolysis of HCHO (1.60×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), especially within the plumes originated from the industrial zone. The observed similarity between HONO/NO<sub>2</sub>and HONO in diurnal profiles strongly suggests that HONO in the study area was likely originated from NO<sub>2</sub>heterogeneous reactions. The averagenighttimeNO<sub>2</sub>to HONO conversion ratewas determined to be ~0.9% hr<sup>-1</sup>. Good correlation between nocturnal HONO/NO<sub>2</sub>and the products of particle surface area density (S/V) and relative humidity (RH), S/V×RH,supports the heterogeneous NO<sub>2</sub>/H<sub>2</sub>O reaction mechanism. The other HONO source, designated as P<sub>unknonwn</sub>, was about twice as much as P<sub>OH+NO </sub>on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO<sub>2</sub>may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO<sub>2</sub>on aerosol surfaces but heterogeneous NO<sub>2</sub>reactions on ground surface dominated nocturnal HONO production. Concurred elevated HONO and PM<sub>2.5</sub>levels strongly indicate that high HONO may increase the atmospheric oxidation capacity and further promote the formation of secondary aerosols, which may in turn synergistically boost NO<sub>2</sub>/HONO conversion by providing more heterogeneous reaction sites.</p>

scholarly journals Contribution of nitrous acid to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

2020 ◽  
Vol 20 (9) ◽  
pp. 5457-5475
Author(s):  
Jun Zheng ◽  
Xiaowen Shi ◽  
Yan Ma ◽  
Xinrong Ren ◽  
Halim Jabbour ◽  
...  
Keyword(s):  
Nitrous Acid ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Atmospheric Oxidation ◽  
Formation Mechanisms ◽  
The Yangtze River ◽  
Industrial Zone ◽  
Oxidation Capacity ◽  
The Yangtze River Delta

Abstract. A suite of instruments was deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO), ozone (O3), volatile organic compounds (VOCs – including formaldehyde, HCHO) and meteorological parameters near a typical industrial zone in Nanjing in the Yangtze River Delta (YRD) region of China from 1 to 31 December 2015. High levels of HONO were detected using a wet-chemistry-based method. HONO ranged from 0.03 to 7.04 ppbv with an average of 1.32±0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundred parts per trillion by volume (pptv) on average, which cannot be explained by the homogeneous OH + NO reaction (POH+NO) and primary emissions (Pemission), especially during periods with high particulate matter (PM2.5) loadings. HONO chemistry and its impact on the atmospheric oxidation capacity in the study area were further investigated using a Master Chemical Mechanism (MCM) box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×106 molec. cm−3 s−1), followed by the ozonolysis of alkenes (3.94×106 molec. cm−3 s−1), the photolysis of O3 (2.46×106 molec. cm−3 s−1) and the photolysis of HCHO (1.60×106 molec. cm−3 s−1) during the campaign period, especially within plumes that originated from the industrial zone. Model simulations indicated that heterogeneous chemistry played an important role in HONO formation. The average nighttime NO2 to HONO conversion rate was determined to be ∼0.8 % h−1. A good correlation between nocturnal HONO∕NO2 and the product of particle surface area density (S∕V) and relative humidity (RH), S/V⋅RH, supports the heterogeneous NO2∕H2O reaction mechanism. The other HONO source, designated as Punknonwn, was about twice as high as POH+NO on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO2 may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO2 on aerosol surfaces, whereas heterogeneous NO2 reactions on the ground surface dominated nocturnal HONO production. Our study indicated that an elevated PM2.5 level during haze events can promote the conversion of NO2 to HONO by providing more heterogeneous reaction sites, thereby increasing the atmospheric oxidation capacity, which may further promote the formation of secondary air pollutants. Highlights: High levels of HONO, with an average of 1.32±0.92 ppbv, were observed near one of the largest industrial zones in the YRD region of China. HONO photolysis and alkene ozonolyses contributed the most to OH production and, hence, the atmospheric oxidation capacity. High loading of PM2.5 provided additional reaction surfaces for HONO formation. Heterogeneous formation mechanisms were the most important daytime HONO sources and were further enhanced by sunlight.

scholarly journals Contribution of HONO to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

2019 ◽  
Author(s):  
Jun Zheng ◽  
Xiaowen Shi ◽  
Yan Ma ◽  
Xinrong Ren ◽  
Halim Jabbour ◽  
...  
Keyword(s):  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Atmospheric Oxidation ◽  
The Yangtze River ◽  
Industrial Zone ◽  
Delta Region ◽  
Oxidation Capacity ◽  
Yangtze River Delta Region ◽  
The Yangtze River Delta

Abstract. A suite of instruments were deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO), ozone (O3), volatile organic compounds (VOCs, including formaldehyde (HCHO)) and meteorological parameters near a typical industrial zone in Nanjing of the Yangtze River Delta region, China. High levels of HONO were detected using a wet chemistry-based method. HONO ranged from 0.03–7.04 ppbv with an average of 1.32 ± 0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundreds of pptv on average, which cannot be explained by the homogeneous OH + NO reaction (POH+NO) alone, especially during periods with high loadings of particulate matters (PM2.5). The HONO chemistry and its impact on atmospheric oxidation capacity in the study area were further investigated using a MCM-box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×106 molecules cm−3 s−1), followed by ozonolysis of alkenes (3.94×106 molecules cm−3 s−1), photolysis of O3 (2.46×106 molecules cm−3 s−1) and photolysis of HCHO (1.60×106 molecules cm−3 s−1), especially within the plumes originated from the industrial zone. The observed similarity between HONO/NO2 and HONO in diurnal profiles strongly suggests that HONO in the study area was likely originated from NO2 heterogeneous reactions. The average nighttime NO2 to HONO conversion rate was determined to be ~ 0.9 % hr−1. Good correlation between nocturnal HONO/NO2 and the products of particle surface area density (S/V) and relative humidity (RH), S/V·RH, supports the heterogeneous NO2/H2O reaction mechanism. The other HONO source, designated as Punknonwn, was about twice as much as POH+NO on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO2 may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO2 on aerosol surfaces but heterogeneous NO2 reactions on ground surface dominated nocturnal HONO production. Concurred elevated HONO and PM2.5 levels strongly indicate that high HONO may increase the atmospheric oxidation capacity and further promote the formation of secondary aerosols, which may in turn synergistically boost NO2/HONO conversion by providing more heterogeneous reaction sites.

Predicting the ignition of crown fuels above a spreading surface fire. Part II: model evaluation

2006 ◽  
Vol 15 (1) ◽  
pp. 61 ◽  
Author(s):  
Miguel G. Cruz ◽  
Bret W. Butler ◽  
Martin E. Alexander
Keyword(s):  
Particle Surface ◽  
Lower Boundary ◽  
Ground Surface ◽  
Volume Ratio ◽  
Fuel Particle ◽  
Particle Surface Area ◽  
Surface Fire ◽  
Fuel Layer ◽  
Model Predictions ◽  
A Minor

A crown fuel ignition model (CFIM) describing the temperature rise and subsequent ignition of the lower portion of tree crowns above a spreading surface fire was evaluated through a sensitivity analysis, comparison against other models, and testing against experimental fire data. Results indicate that the primary factors influencing crown fuel ignition are those determining the depth of the surface fire burning zone and the vertical distance between the ground/surface fuel strata and the lower boundary of the crown fuel layer. Intrinsic crown fuel properties such as fuel particle surface area-to-volume ratio and foliar moisture content were found to have a minor influence on the process of crown fuel ignition. Comparison of model predictions against data collected in high-intensity experimental fires and predictions from other models gave encouraging results relative to the validity of the model system.

scholarly journals Acyl peroxy nitrate measurements during the photochemical smog season in Beijing, China

2011 ◽  
Vol 11 (3) ◽  
pp. 10265-10303 ◽  
Author(s):  
Z. Xu ◽  
J. Zhang ◽  
G. Yang ◽  
M. Hu
Keyword(s):  
Particle Surface ◽  
Heterogeneous Reactions ◽  
Anthropogenic Sources ◽  
World Health ◽  
Photochemical Smog ◽  
Particle Surface Area ◽  
Mixing Ratios ◽  
Total Particle ◽  
Health Organization ◽  
Beijing China

Abstract. In situ measurements of acyl peroxy nitrates (PANs), including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN), were conducted using a gas chromatography-electron capture detector (GC-ECD) system during the photochemical smog season in Beijing, China. The maximum mixing ratios were 17.81, 2.48, and 0.27 ppbv for PAN, PPN, and MPAN, respectively. During the measurement period, PAN levels twice exceeded the maximum recommended mixing ratio established by the World Health Organization (WHO). Average ratios of PAN/PPN, PAN/MPAN, and PPN/MPAN were 7.41, 47.65, and 6.91, respectively. The average ratio of PAN/O3 (0.15) in Beijing was significantly higher than those in other areas studied. The frequencies of PANs showed both Gaussian and Weibull modes of distribution. Wind direction was closely related to PAN variation. Anthropogenic sources played an important role in PAN formation, as estimated from PPN and MPAN levels. Relative humidity (RH) and total particle surface area were related with the heterogeneous reactions of PANs with surface concentrations of particulate matter ≤10 μm in diameter.

scholarly journals Modeling the impact of heterogeneous reactions of chlorine on summertime nitrate formation in Beijing, China

2019 ◽  
Vol 19 (10) ◽  
pp. 6737-6747 ◽  
Author(s):  
Xionghui Qiu ◽  
Qi Ying ◽  
Shuxiao Wang ◽  
Lei Duan ◽  
Jian Zhao ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Particle Surface ◽  
Heterogeneous Reactions ◽  
Sensitivity Analyses ◽  
Uptake Coefficient ◽  
Transport Models ◽  
Nitrate Concentrations ◽  
The Impact ◽  
Beijing China ◽  
Significant Underestimation

Abstract. Comprehensive chlorine heterogeneous chemistry is incorporated into the Community Multiscale Air Quality (CMAQ) model to evaluate the impact of chlorine-related heterogeneous reaction on diurnal and nocturnal nitrate formation and quantify the nitrate formation from gas-to-particle partitioning of HNO3 and from different heterogeneous pathways. The results show that these heterogeneous reactions increase the atmospheric Cl2 and ClNO2 level (∼ 100 %), which further affects the nitrate formation. Sensitivity analyses of uptake coefficients show that the empirical uptake coefficient for the O3 heterogeneous reaction with chlorinated particles may lead to the large uncertainties in the predicted Cl2 and nitrate concentrations. The N2O5 uptake coefficient with particulate Cl− concentration dependence performs better in capturing the concentration of ClNO2 and nocturnal nitrate concentration. The reaction of OH and NO2 in the daytime increases the nitrate by ∼15 % when the heterogeneous chlorine chemistry is incorporated, resulting in more nitrate formation from HNO3 gas-to-particle partitioning. By contrast, the contribution of the heterogeneous reaction of N2O5 to nitrate concentrations decreases by about 27 % in the nighttime, when its reactions with chlorinated particles are considered. However, the generated gas-phase ClNO2 from the heterogeneous reaction of N2O5 and chlorine-containing particles further reacts with the particle surface to increase the nitrate by 6 %. In general, this study highlights the potential of significant underestimation of daytime concentrations and overestimation of nighttime nitrate concentrations for chemical transport models without proper chlorine chemistry in the gas and particle phases.

scholarly journals Enhanced sulfate formation through SO<sub>2</sub>+NO<sub>2</sub> heterogeneous reactions during heavy winter haze in the Yangtze River Delta region, China

2019 ◽  
Author(s):  
Ling Huang ◽  
Jingyu An ◽  
Bonyoung Koo ◽  
Greg Yarwood ◽  
Rusha Yan ◽  
...  
Keyword(s):  
Air Quality ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
Heterogeneous Reactions ◽  
Ammonia Emissions ◽  
The Yangtze River ◽  
Uptake Mechanism ◽  
Sulfate Formation ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Rapid sulfate formation is recognized as key characteristics of severe winter haze in China. However, air quality models tend to underestimate sulfate formation during heavy haze periods and heterogeneous formation pathways have been proposed as promising mechanisms to reduce gaps between observation and model simulation. In this study, we implemented a reactive SO2 uptake mechanism through the SO2+NO2 heterogeneous reactions in the Comprehensive Air Quality Model with extensions (CAMx) to improve simulation of sulfate formation in the Yangtze River Delta (YRD) region for the first time. Parameterization of the SO2+NO2 heterogeneous reactions is based on observations in Beijing and considered both impact of relative humidity and aerosol pH on sulfate formation. Ammonia is reported to be critical for the formation of secondary inorganic aerosols and estimation of ammonia emissions is usually associated with large uncertainties. Sensitivity tests were conducted to evaluate the importance of the SO2+NO2 heterogeneous reactions as well as ammonia emissions on modelled sulfate concentrations during a period with several heavy haze episodes in the YRD region. Base case model results show large underestimation of sulfate concentrations by 36 % under polluted conditions in the YRD region. Adding the SO2+NO2 heterogeneous reactions or doubling ammonia emissions alone leads to slight model improvement (~ 6 %) on simulated sulfate concentrations in the YRD region. However, model performance significantly improved when both the SO2+NO2 heterogeneous reactions and doubled ammonia emissions were included in the simulation: predicted sulfate concentrations during polluted periods increased from 23.1 µg m−3 in the base scenario to 29.1 µg m−3 (representing an increase of 26 %). Aerosol pH is crucial for the SO2+NO2 heterogeneous reactions and our calculated aerosol pH is always acidic and increased by 0.7 with doubled ammonia emissions. Modelling results also show that this reactive SO2 uptake mechanism enhanced sulfate simulations by 1 to 5 µg m−3 for the majority of eastern and central part of China, with more than 20 µg m−3 increase of sulfate concentrations over the north-eastern plateau. These findings suggest that the SO2+NO2 heterogeneous reactions could be important for sulfate formation in the YRD region as well as other parts of China. In addition, ammonia emissions need to be carefully estimated. More studies are needed to improve the parameterization of the SO2+NO2 heterogeneous reactions based on local data further evaluate this mechanism in other regions. Substantial efforts are needed to improve the accuracy of ammonia emissions inventory.

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