scholarly journals Simulations of Sulfate-Nitrate-Ammonium (SNA) aerosols during the extreme haze events over Northern China in October 2014

2016 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Jerome Fast ◽  
Junmei Ban
Keyword(s):  
Relative Humidity ◽  
Observational Data ◽  
Heterogeneous Reaction ◽  
Northern China ◽  
Reaction Rates ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Emission Rates ◽  
Oxidation Rates ◽  
The North

Abstract. Extreme haze events have occurred frequently over China in recent years. Although many studies have investigated the formation mechanisms associated with PM2.5 for heavily polluted regions in China based on observational data, adequately predicting peak PM2.5 concentrations is still challenging for regional air quality models. In this study, we evaluate the performance of one configuration of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and use the model to investigate the sensitivity of heterogeneous reactions on simulated peak sulfate, nitrate, and ammonium concentrations in the vicinity of Beijing during four extreme haze episodes in October 2014 over the North China Plain. The highest observed PM2.5 concentration of 469 μg m-3 occurred in Beijing. Comparisons with observations show that the model reproduced the temporal variability in PM2.5 with the highest PM2.5 values on polluted days (defined as days in which observed PM2.5 is greater than 75 μg m-3), but predictions of sulfate, nitrate, and ammonium were too low on days with the highest observed concentrations. Observational data indicate that the sulfur/nitric oxidation rates are strongly correlated with relative humidity during periods of peak PM2.5; however, the model failed to reproduce the highest PM2.5 concentrations due to missing heterogeneous reactions. As the parameterizations of those reactions is not well established yet, estimates of SO2-to-H2SO4 and NO2/NO3-to-HNO3 reaction rates that depend on relative humidity were applied which improved the simulation of sulfate, nitrate, and ammonium enhancement on polluted days in terms of both concentrations and partitioning among those species. Sensitivity simulations showed that the extremely high heterogeneous reaction rates and also higher emission rates than those reported in the emission inventory were likely important factors contributing to those peak PM2.5 simulations.

scholarly journals Simulations of sulfate–nitrate–ammonium (SNA) aerosols during the extreme haze events over northern China in October 2014

2016 ◽  
Vol 16 (16) ◽  
pp. 10707-10724 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Jerome Fast ◽  
Junmei Ban
Keyword(s):  
Relative Humidity ◽  
Observational Data ◽  
Heterogeneous Reaction ◽  
Northern China ◽  
Reaction Rates ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Emission Rates ◽  
Oxidation Rates ◽  
The North

Abstract. Extreme haze events have occurred frequently over China in recent years. Although many studies have investigated the formation mechanisms associated with PM2.5 for heavily polluted regions in China based on observational data, adequately predicting peak PM2.5 concentrations is still challenging for regional air quality models. In this study, we evaluate the performance of one configuration of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and use the model to investigate the sensitivity of heterogeneous reactions on simulated peak sulfate, nitrate, and ammonium concentrations in the vicinity of Beijing during four extreme haze episodes in October 2014 over the North China Plain. The highest observed PM2.5 concentration of 469 µg m−3 occurred in Beijing. Comparisons with observations show that the model reproduced the temporal variability in PM2.5 with the highest PM2.5 values on polluted days (defined as days in which observed PM2.5 is greater than 75 µg m−3), but predictions of sulfate, nitrate, and ammonium were too low on days with the highest observed concentrations. Observational data indicate that the sulfur/nitric oxidation rates are strongly correlated with relative humidity during periods of peak PM2.5; however, the model failed to reproduce the highest PM2.5 concentrations due to missing heterogeneous/aqueous reactions. As the parameterizations of those heterogeneous reactions are not well established yet, estimates of SO2-to-H2SO4 and NO2/NO3-to-HNO3 reaction rates that depend on relative humidity were applied, which improved the simulation of sulfate, nitrate, and ammonium enhancement on polluted days in terms of both concentrations and partitioning among those species. Sensitivity simulations showed that the extremely high heterogeneous reaction rates and also higher emission rates than those reported in the emission inventory were likely important factors contributing to those peak PM2.5 concentrations.

Study on Black Liquor Low-temperature Gasification in Fluidized Bed by Eulerian Multiphase Computationally Fluid Dynamics Modeling

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Weiling Li ◽  
Wenqi Zhong ◽  
Baosheng Jin ◽  
Rui Xiao ◽  
Yingjuan Shao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fluidized Bed ◽  
Reaction Rate ◽  
Solid Phase ◽  
Heterogeneous Reaction ◽  
Black Liquor ◽  
Molar Fraction ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Heterogeneous Reactions

Abstract A three-dimensional Eulerian multiphase based computational model was developed to simulate the black liquor gasification processes in a fluidized bed gasifier (FBG) at low temperature. The standard k-e model and kinetic theory of granular model were used to simulate the gas phase and solid phase, respectively. Black liquor pyrolysis, homogeneous reactions and heterogeneous reactions were taken into account in chemical model. The reaction rates of homogeneous and heterogeneous reaction were determined by Arrhenius–Eddy dissipation reaction rate and kinetic reaction rate. Simulations were carried out at four different operating conditions, i.e. reactor temperature was kept at 550 degree centigrade or 600 degree centigrade, and nitrogen or air was used as fluidizing medium. The calculated results were in well agreement with the experiment used as calibration. Base on the simulation, gas-sold flow patterns and gas species molar fraction distributions were obtained, the relationship of gas composition profiles with the temperature and the fluidizing media were discussed.

Seasonal effects of additional HONO sources and the heterogeneous reactions of N2O5 on nitrate in the North China Plain

2020 ◽  
Author(s):  
Yu Qu ◽  
Junling An
Keyword(s):  
North China Plain ◽  
North China ◽  
Heterogeneous Reaction ◽  
Heterogeneous Reactions ◽  
Seasonal Effects ◽  
Weather Research And Forecasting ◽  
The North ◽  
The North China Plain ◽  
Four Seasons ◽  
Hydrolysis Of

<p>We coupled the heterogeneous hydrolysis of N<sub>2</sub>O<sub>5</sub> into the newly updated Weather Research and Forecasting model with Chemistry (WRF-Chem) to reveal the relative importance of the hydrolysis of N<sub>2</sub>O<sub>5</sub> and additional nitrous acid (HONO) sources for the formation of nitrate during high PM<sub>2.5</sub> events in the North China Plain (NCP) in four seasons. The results showed that additional HONO sources produced the largest nitrate concentrations in winter and negligible nitrates in summer, leading to a 10% enhancement of a PM<sub>2.5</sub> peak in southern Beijing and a 15% enhancement in southeastern Hebei in winter. In contrast, the hydrolysis of N<sub>2</sub>O<sub>5</sub> produced high nitrate in summer and low nitrate in winter, with the largest contribution of nearly 20% for a PM<sub>2.5</sub> peak in southeastern Hebei in summer. During PM<sub>2.5 </sub>explosive growth events, the additional HONO sources played a key role in nitrate increases in southern Beijing and southwestern Hebei in winter, whereas the hydrolysis of N<sub>2</sub>O<sub>5 </sub>contributed the most to a rapid increase in nitrate in other seasons. HONO photolysis produced more hydroxyl radicals, which were greater than 1.5 μg m<sup>-3</sup> h<sup>-1</sup> in the early explosive stage and led to a rapid nitrate increase at the southwestern Hebei sites in winter, while the heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> contributed greatly to a significant increase in nitrate in summer. The above results suggest that the additional HONO sources and the heterogeneous hydrolysis of N<sub>2</sub>O<sub>5</sub> contributed the most to nitrate formation in NCP in winter and summer, respectively.</p>

scholarly journals Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China

2016 ◽  
Vol 2 (12) ◽  
pp. e1601530 ◽  
Author(s):  
Yafang Cheng ◽  
Guangjie Zheng ◽  
Chao Wei ◽  
Qing Mu ◽  
Bo Zheng ◽  
...  
Keyword(s):  
Northern China ◽  
Reaction Rates ◽  
Reactive Nitrogen ◽  
Sulfate Production ◽  
The North ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Haze Pollution ◽  
Neutralizing Capacity ◽  
Particle Pollution

Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. Sulfate is a major component of fine haze particles. Record sulfate concentrations of up to ~300 μg m−3 were observed during the January 2013 winter haze event in Beijing. State-of-the-art air quality models that rely on sulfate production mechanisms requiring photochemical oxidants cannot predict these high levels because of the weak photochemistry activity during haze events. We find that the missing source of sulfate and particulate matter can be explained by reactive nitrogen chemistry in aerosol water. The aerosol water serves as a reactor, where the alkaline aerosol components trap SO2, which is oxidized by NO2 to form sulfate, whereby high reaction rates are sustained by the high neutralizing capacity of the atmosphere in northern China. This mechanism is self-amplifying because higher aerosol mass concentration corresponds to higher aerosol water content, leading to faster sulfate production and more severe haze pollution.

scholarly journals Spatio-Temporal Characteristics and Obstacle Factors of the Urban-Rural Integration of China’s Shrinking Cities in the Context of Sustainable Development

2021 ◽  
Vol 13 (8) ◽  
pp. 4203
Author(s):  
Bin Du ◽  
Ying Wang ◽  
Jiaxin He ◽  
Wai Li ◽  
Xiaohong Chen
Keyword(s):  
Sustainable Development ◽  
Economic Efficiency ◽  
Formation Mechanisms ◽  
Shrinking Cities ◽  
The Sustainable Development ◽  
Factors Affecting ◽  
Temporal Characteristics ◽  
The North ◽  
Urban Rural ◽  
Spatio Temporal

Based on the fundamental concept of sustainable development, this study empirically analyzes the spatio-temporal characteristics, formation mechanisms and obstacle factors of the urban-rural integration of shrinking cities in China, from 2008 to 2018. The conclusions are as follows: the overall level of the urban-rural integration of shrinking cities in China is low; the internal differences of urban-rural integration are also small, and the changes are slow. Next, the space difference is high in the east and low in the west, high in the south and low in the north. Moreover, differences exist among different levels of urban agglomerations. Urban economic efficiency, urban resources and environment, urban social equity and rural economic efficiency are the main factors affecting the urban-rural integration of shrinking cities in China. Urban and rural economic efficiency are the two most prominent shortcomings that restrict the urban-rural integration of shrinking cities. The spatial resistance mode of each city is more than the two-system resistance; the main resistance of shrinking cities with a higher level of urban-rural integration also comes from the non-economic field. This study expands the research scope that up till now has ignored the discussion of urban-rural issues in the research of shrinking cities at home and abroad, and provides practical guidance for the sustainable development of shrinking cities in China.

scholarly journals Potential Evapotranspiration Reduction and Its Influence on Crop Yield in the North China Plain in 1961–2014

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Wanlin Dong ◽  
Chao Li ◽  
Qi Hu ◽  
Feifei Pan ◽  
Jyoti Bhandari ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Crop Yield ◽  
North China Plain ◽  
North China ◽  
Potential Evapotranspiration ◽  
The North ◽  
The North China Plain ◽  
Sunshine Hours ◽  
Humidity Index

Climate change has caused uneven changes in hydrological processes (precipitation and evapotranspiration) on a space-temporal scale, which would influence climate types, eventually impact agricultural production. Based on data from 61 meteorological stations from 1961 to 2014 in the North China Plain (NCP), the spatiotemporal characteristics of climate variables, such as humidity index, precipitation, and potential evapotranspiration (ET0), were analyzed. The sensitivity coefficients and contribution rates were applied to ET0. The NCP has experienced a semiarid to humid climate from north to south due to the significant decline of ET0 (−13.8 mm decade−1). In the study region, 71.0% of the sites showed a “pan evaporation paradox” phenomenon. Relative humidity had the most negative influence on ET0, while wind speed, sunshine hours, and air temperature had a positive effect on ET0. Wind speed and sunshine hours contributed the most to the spatiotemporal variation of ET0, followed by relative humidity and air temperature. Overall, the key climate factor impacting ET0 was wind speed decline in the NCP, particularly in Beijing and Tianjin. The crop yield in Shandong and Henan provinces was higher than that in the other regions with a higher humidity index. The lower the humidity index in Hebei province, the lower the crop yield. Therefore, potential water shortages and water conflict should be considered in the future because of spatiotemporal humidity variations in the NCP.

Development of homogeneous/heterogeneous reaction in flow based through non-Darcy Forchheimer medium

2017 ◽  
Vol 16 (05) ◽  
pp. 1750045 ◽  
Author(s):  
Tasawar Hayat ◽  
Faisal Shah ◽  
Ahmed Alsaedi ◽  
Muhammad Ijaz Khan
Keyword(s):  
Magnetic Parameter ◽  
Heterogeneous Reaction ◽  
Phase Changes ◽  
Heterogeneous Reactions ◽  
Medium Effect ◽  
Effect Of Temperature ◽  
Temperature Phase ◽  
Surface Thermodynamics ◽  
Isothermal Model ◽  
Physical Quantities

The objective here is to analyze the influence of homogeneous and heterogeneous reactions in flow induced by convectively heated sheet with nonlinear velocity and variable thickness. Porous medium effect is characterized by Darcy–Forchheimer consideration. A simple isothermal model of homogeneous–heterogeneous reactions is used to regulate the temperature of stretched surface. Thermodynamics processes of homogeneous–heterogeneous reactions analyze the effect of temperature phase changes. Resulting problems are computed for the convergent solutions of velocity, temperature and concentration. Analysis for the influential variables on the physical quantities is graphically examined. Our computed results interpret that velocity field decays for larger magnetic parameter while temperature field enhances for higher estimation of Biot number.

Theoretical analysis of SWCNT- MWCNT/H2O hybrid flow over an upward/downward moving rotating disk

2021 ◽  
pp. 239779142098028
Author(s):  
R.J. Punith Gowda ◽  
R. Naveenkumar ◽  
J.K. Madhukesh ◽  
B.C. Prasannakumara ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Heterogeneous Reaction ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Heterogeneous Reactions ◽  
Hybrid Nanofluid ◽  
Boundary Constraints ◽  
Wide Range ◽  
Contraction Parameter ◽  
Dimensional Parameters ◽  
Source Sink

The flow-through various disk movement has wide range of applications in manufacturing processes like, computer storage equipment’s, rotating machines, electronic and various types of medical equipment’s. Inspired from these applications, here we scrutinised the consequences of homogeneous-heterogeneous reactions and uniform heat source/sink on the three-dimensional (3D) hybrid SWCNT-MWCNT’s flow on time dependent moving upward/downward rotating disk. The renowned innovation of this paper is the application of the hybrid nanofluid made up of SWCNT and MWCNT’s. Heat generation/absorption effect for the disk that does not move up or down creates a dual flow on the disk. Alternatively, the rotation and upright motion of the disk creates a 3D flow on the surface which has not been considered in the open literature. The modelled PDE’s are reduced in to ODE’s by opting suitable similarity variables and boundary constraints. Here, we used RKF-45 method to obtain the numerical approximations by adopting shooting technique. The analysis of rate of heat transfer is done through graphs. Further, change in velocity, thermal and concentration profiles for various non-dimensional parameters are deliberated briefly and illustrated with the help of suitable plots. The results reveal that, the, rise in values of homogeneous and heterogeneous reaction parameters improve the rate of reaction which results in reduction of the distribution rate and diminishes the concentration gradient. An increase in expansion/contraction parameter enhances the velocity and thermal gradients.

Seasonal Analysis of Air-Sea CO2 Flux Variability in the North Atlantic and the Southern Ocean 

2021 ◽  
Author(s):  
Paridhi Rustogi ◽  
Peter Landschuetzer ◽  
Sebastian Brune ◽  
Johanna Baehr
Keyword(s):  
Southern Ocean ◽  
Observational Data ◽  
North Atlantic ◽  
Seasonal Variability ◽  
Max Planck ◽  
Regional Patterns ◽  
Atlantic Basin ◽  
North Atlantic Basin ◽  
The North ◽  
The North Atlantic

<p>Understanding the variability and drivers of air-sea CO<span><sub>2</sub></span> fluxes on seasonal timescales is critical for resolving the ocean carbon sink's evolution and variability. Here, we investigate whether discrepancies in the representation of air-sea CO<span><sub>2</sub></span> fluxes on a seasonal timescale accumulate to influence the representation of CO<span><sub>2</sub></span> fluxes on an interannual timescale in two important ocean CO<span><sub>2 </sub></span>sink regions – the North Atlantic basin and the Southern Ocean. Using an observation-based product (SOM-FFN) as a reference, we investigate the representation of air-sea CO<span><sub>2</sub></span> fluxes in the Max Planck Institute's Earth System Model Grand Ensemble (MPI-ESM GE). Additionally, we include a simulation based on the same model configuration, where observational data from the atmosphere and ocean components is assimilated (EnKF assimilation) to verify if the inclusion of observational data alters the model state significantly and if the updated modelled CO<span><sub>2 </sub></span>flux values better represent observations.</p><p>We find agreement between all three observation-based and model products on an interannual timescale for the North Atlantic basin. However, the agreement on a seasonal timescale is inconsistent with discrepancies as large as 0.26 PgC/yr in boreal autumn in the North Atlantic. In the Southern Ocean, we find little agreement between the three products on an interannual basis with significant seasonal discrepancies as large as 1.71 PgC/yr in austral winter. However, while we identify regional patterns of dominating seasonal variability in MPI-GE and EnKF, we find that the SOM-FFN cannot demonstrate robust conclusions on the relevance of seasonal variability in the Southern Ocean. In turn, we cannot pin down the problems for this region.</p>

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