Effects of Inorganic Salts on the Phase Separation of Partially Miscible Solutes.

Partially miscible solutions with a lower critical solution temperature have promising applications in the field of physical chemistry. To better guide the utilization of these solutions in practice, we conduct an in-depth study about the phase separation behavior of the solution added with inorganic salts. The addition of the inorganic salts into the solution is found to consequently reduce the phase separation temperature. The variation of concentrations of inorganic salts does not notably affect the mass fraction of the separation. Moreover, the addition of inorganic salts in the solutions at lower mass fractions improves the separation mass fraction, while the addition of inorganic salts decreases the separation mass fraction at the mass fractions above 30%. It sheds light on selecting the proper mass fractions and inorganic salt concentrations. Furthermore, we explore the phase separation behavior of mixed solutions under different inorganic salt additions by means of a high-speed camera. The phase separation behavior under different inorganic salt systems shows a similar trend. However, calcium ions and Fe3+ ions in the solutions can greatly decrease the rate of droplet coalescence and result in an increase in phase separation. For better regulating the solutions with a lower critical solution temperature through inorganic salts, sodium chloride or potassium chloride is recommended with an appropriate concentration.

Phosphorylation of Oligopeptides: Design of Ultra-Hydrophilic Zwitterionic Peptides for Anti-Fouling Detection of Nucleic Acids in Saliva.

The construction of low-fouling biosensors for assaying biomarkers in complex biological samples remains a challenge, and the key limitation is the lack of effective anti-fouling materials. Inspired by the biomimetic process of protein phosphorylation, we herein designed a new phosphorylated peptide modified with the dihydrogen phosphate (-PO4H2) group, which significantly increased the hydrophilicity and anti-fouling capability of the peptide when compared with natural and normal peptides. Molecular simulation (MS) illustrated that, compared with the -COOH and -NH2 groups, the -PO4H2 group formed the most numbers of hydrogen bonds and stronger hydrogen bonds with water molecules. As a result, the PO4H2-oligopeptide was proved by MS to be able to attract the greatest number of water molecules, so as to form a compact layer of H2O to resist further adsorption of nonspecific biomolecules. The modification of electrodes with the designed PO4H2-oligopeptides, in addition to the adoption of neutral peptide nucleic acids (PNAs) as the sensing probes, ensured the fabrication of anti-fouling electrochemical biosensors capable of detecting nucleic acids in complex saliva. The constructed anti-fouling biosensor was able to detect the nucleic acid of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in undiluted saliva, with a wide linear response range (0.01 pM-0.01 µM) and a low limit of detection (LOD) of 3.4 fM (S/N = 3). The phosphorylation of oligopeptides offers an effective strategy to designing ultra-hydrophilic peptides suitable for the construction of promising anti-biofouling biosensors and bioelectronics.

Present Knowledge and Future Perspectives of Atmospheric Emission Inventories of Toxic Trace Elements: A Critical Review.

Toxic trace elements (TEs) can pose serious risks to ecosystems and human health. However, a comprehensive understanding of atmospheric emission inventories for several concerning TEs has not yet been developed. In this study, we systematically reviewed the status and progress of existing research in developing atmospheric emission inventories of TEs focusing on global, regional, and sectoral scales. Multiple studies have strengthened our understanding of the global emission of TEs, despite attention being mainly focused on Hg and source classification in different studies showing large discrepancies. In contrast to those of developed countries and regions, the officially published emission inventory is still lacking in developing countries, despite the fact that studies on evaluating the emissions of TEs on a national scale or one specific source category have been numerous in recent years. Additionally, emissions of TEs emitted from waste incineration and traffic-related sources have produced growing concern with worldwide rapid urbanization. Although several studies attempt to estimate the emissions of TEs based on PM emissions and its source-specific chemical profiles, the emission factor approach is still the universal method. We call for more extensive and in-depth studies to establish a precise localization national emission inventory of TEs based on adequate field measurements and comprehensive investigation to reduce uncertainty.

Characterization of photochemical losses of volatile organic compounds and their implications for ozone formation potential and source apportionment during summer in suburban Jinan, China.

Volatile organic compounds (VOCs) undergo substantial photochemical losses during their transport from emission sources to receptor sites, resulting in serious implications for their source apportionment and ozone (O3) formation. Based on the continuous measurements of VOCs in suburban Jinan in August 2022, the effects of photochemical losses on VOC source contributions and O3 formation were evaluated in this study. The observed and initial concentrations of total VOCs (TVOC) were 12.0 ± 5.1 and 16.0 ± 7.4 ppbv, respectively. Throughout the observation period, alkenes had the most prominent photochemical losses (58.2%), followed by aromatic hydrocarbons (23.1%), accounting for 80.6% and 6.9% of the total losses, respectively. During high O3 episodes, the photochemical loss of VOCs was 6.9 times higher than that during the cleaning period. Alkene losses (exceeding 67.3%), specifically losses of isoprene, propylene, ethylene, and n-butene, dominated the total losses of VOCs during the O3 increase period. Eight sources of VOCs were identified by positive matrix factorization (PMF) based on the observed and initial concentration data (OC-PMF and IC-PMF, respectively). Concentrations of all emission sources in the OC-PMF were underestimated by 2.4%-57.1%. Moreover, the contribution of each emission source was over- or underestimated compared with that in case of the IC-PMF. The contributions of biogenic and motor vehicle exhaust emissions were underestimated by 5.3 and 2.8 percentage points, respectively, which was associated with substantial oxidation of the emitted high-reactive species. The contributions of coal/biomass burning and natural gas were overestimated by 2.4 and 3.9 percentage points, respectively, which were related to the emission of low-reactive species (acetylene, ethane, and propane). Based on our results, the photochemical losses of VOCs grossly affect their source apportionment and O3 formation. Thus, photochemical losses of VOCs must be thoroughly accounted to establish a precise scientific foundation for air-pollution control strategies.

Atomistic Insights into the Effect of Functional Groups on the Adsorption of Water by Activated Carbon for Heat Energy Storage.

Adsorption heat storage holds great promise for solar energy applications. The development of new adsorbent materials is currently the research focus in this area. The present work designs several activated carbon models with different functional groups, including -OH, -NH2, -COOH, and -SO3H, and explores the influence of functional groups' categories and numbers on the water adsorption capacity of the activated carbon using the GCMC method. The adsorption mechanism between functional groups and water molecules is analyzed using density functional theory. The results show that the functional groups could significantly improve the water adsorption capacity of activated carbon due to the hydrogen bond between functional groups and water molecules. In the scope of this paper, under low pressure, the activated carbon with -SO3H exhibits the best adsorption capacity, followed by the activated carbon with -COOH. Under low and medium pressure, increasing the number of -SO3H functional groups could increase the water adsorption capacity; however, when the pressure is high, increasing the functional group numbers might decrease the water adsorption capacity. As the temperature increases, the water adsorption capacity of activated carbons decreases, and the activated carbon with -SO3H is proven to have excellent application prospects in heat energy storage.

Predicting the effective thermal conductivity of unfrozen soils with various water contents based on artificial neural network.

The effective thermal conductivity of soils is a crucial parameter for many applications such as geothermal engineering, environmental science, and agriculture and engineering. However, it is pretty challenging to accurately determine it due to soils' complex structure and components. In the present study, the influences of different parameters, including silt content (msi), sand content (msa), clay content (mcl), quartz content (mqu), porosity, and water content on the effective thermal conductivity of soils, were firstly analyzed by the Pearson correlation coefficient. Then different artificial neural network (ANN) models were developed based on the 465 groups of thermal conductivity of unfrozen soils collected from the literature to predict the effective thermal conductivity of soils. Results reveal that the parameters ofmsi,msa,mcl, andmquhave a relatively slight influence on the effective thermal conductivity of soils compared to the water content and porosity. Although the ANN model with six parameters has the highest accuracy, the ANN model with two input parameters (porosity and water content) could predict the effective thermal conductivity well with acceptable accuracy andR2= 0.940. Finally, a correlation of the effective thermal conductivity for different soils was proposed based on the large number of results predicted by the two input parameters ANN-based model. This correlation has proved to have a higher accuracy without assumptions and uncertain parameters when compared to several commonly used existing models.

Atmospheric Vanadium Emission Inventory from Both Anthropogenic and Natural Sources in China.

Vanadium is a strategically important metal in the world, although sustained exposure under high vanadium levels may lead to notable adverse impact on health. Here, we leverage a bottom-up approach to quantitatively evaluate vanadium emissions from both anthropogenic and natural sources during 1949-2017 in China for the first time. The results show that vanadium emissions increased by 86% from 1949 to 2005 to a historical peak value and then gradually decreased to 12.9 kt in 2017. With the effective implementation of air pollution control measures, vanadium emissions from anthropogenic sources decreased sharply after 2011. During 2011-2017, about half of vanadium emissions came from coal and oil combustion. In addition, industrial processes and natural sources also cannot be ignored, with the total contributions of more than 24%. The high levels of vanadium emissions were mainly distributed throughout the North China Plain and the eastern and coastal regions, especially in several urban agglomerations. Furthermore, the comprehensive evaluation by incorporating contrastive analysis, Monte Carlo approach, and GEOS-Chem simulation shows that vanadium emissions estimated in this study were reasonable and acceptable. The findings of our study provide not only a scientific foundation for investigating the health effects of vanadium but also useful information for formulating mitigation strategies.

Significant but Spatiotemporal-Heterogeneous Health Risks Caused by Airborne Exposure to Multiple Toxic Trace Elements in China.

Airborne trace elements (TEs) pose a notable threat to human health due to their toxicity and carcinogenicity, whereas their exposures and associated health risks in China remain unclear. Here, we present the first nationwide assessment of spatiotemporal exposure to 11 TEs in China by coupling a bottom-up emission inventory with a modified CMAQ model capable of TE simulation. Associated health risks of 11 TEs are then evaluated using a set of risk assessment models. Our results show that the CMAQ model could reasonably reproduce the spatiotemporal variations of 11 TEs in China compared to observations. We find significant but spatiotemporal-heterogeneous cancer risks associated with high-level exposure of TEs in China. Gridded cell concentrations of hexavalent chromium, arsenic, and nickel in eastern and central China usually exceed China's air quality standard limits, resulting in significant cancer risks that affected over 85% of the entire population in China in 2015. National annual mean population-weighted concentrations of 11 TEs decrease by 9.8-35.6% from 2012 to 2015, largely attributed to emission reduction from coal combustion. Our study provides critical insights for policymakers to implement stricter measures to alleviate health burdens and benefit relevant epidemiological research on airborne TEs.

Non-Negligible Stack Emissions of Noncriteria Air Pollutants from Coal-Fired Power Plants in China: Condensable Particulate Matter and Sulfur Trioxide.

In this study, we investigated the emission characteristics of condensable particulate matter (CPM) and sulfur trioxide (SO3) simultaneously through ammonia-based/limestone-based wet flue gas desulfurization (WFGD) from four typical coal-fired power plants (CFPPs) by conducting field measurements. Stack emissions of filterable particulate matter (FPM) all meet the Chinese ultralow emission (ULE) standards, whereas CPM concentrations are prominent (even exceed 10 mg/Nm3 from two CFPPs). We find that NH4+ and Cl- increase markedly through the ammonia-based WFGD, and SO42- is generally the main ionic component, both in CPM and FPM. Notably, the occurrence of elemental Se in FPM and CPM is significantly affected by WFGD. Furthermore, the established chemical profiles in FPM and CPM show a distinct discrepancy. In CPM, the elemental S mainly exists as a sulfate, and the metallic elements of Na, K, Mg, and Ca mainly exist as ionic species. Our results may indicate that not all SO3 are included in CPM and they co-exist in stack plume. With the substantial reduction of sulfur dioxide (SO2), S distributed in SO3, CPM, and FPM becomes non-negligible. Finally, the emission factors of CPM and SO3 under typical ULE technical routes fall in the ranges of 74.33-167.83 and 48.76-86.30 g/(t of coal) accordingly.

Migration and Emission Characteristics of Ammonia/Ammonium through Flue Gas Cleaning Devices in Coal-Fired Power Plants of China.

To investigate the up-to-date migration and emission characteristics of NH3/NH4+ in coal-fired power plants (CFPPs) after implementing ultralow emission retrofitting, typical air pollution control devices (APCDs) in CFPPs, including flue gas denitrification, dust collectors, combined wet flue gas desulfurization (WFGD), and wet precipitators are involved in field measurements. The results show that most of the excessive injected and/or unreacted ammonia from the flue gas denitrification system, whether selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR), is converted into particle-bound NH4+ (>91%), and the rest (less than 9%) is carried by flue gas in the form of gaseous NH3, with a concentration value of 0.15-0.54 mg/(N m3) at the denitrification outlet. When passing through dust collectors, particle-bound NH4+ concentration decreases substantially along with the removal of particle matter. In WFGD, the dissolution and volatilization effects affect the gaseous ammonia concentration, which decreases when using limestone slurry and a 20% solution of ammonia as a desulfurization agent, while liquid ammonia solution with a high concentration (99.8%) may cause the flue gas NH3 concentration to increase considerably by 13 times. Particle-bound NH4+ concentration is mainly influenced by the relative strength of desulfurization slurry scouring and flue gas carrying effects and increases 2.84-116 times through ammonia-based WFGD. Furthermore, emission factors of NH3 for combinations of APCDs are discussed.

Effects of Wet Flue Gas Desulfurization and Wet Electrostatic Precipitators on Emission Characteristics of Particulate Matter and Its Ionic Compositions from Four 300 MW Level Ultralow Coal-Fired Power Plants.

To achieve ultralow-emission (ULE) standards, wet electrostatic precipitators (WESP) installed downstream from wet flue gas desulfurization (WFGD) have been widely used in Chinese coal-fired power plants (CFPPs). We conducted a comprehensive field test study at four 300 MW level ULE CFPPs, to explore the impact of wet clean processing (WFGD and WESP) on emission characteristics of three size fractions of particulate matter (PM: PM2.5, PM10-2.5, and PM>10) and their ionic compositions. All these CFPPs are installed with limestone-based/magnesium-based WFGD and followed by WESP as the end control device. Our results indicate that particle size distribution, mass concentration of PM, and ionic compositions in flue gas change significantly after passing WFGD and WESP. PM mass concentrations through WFGD are significantly affected by the relative strength between desulfur slurry scouring and flue gas carrying effects. Concentrations of ions in PM increase greatly after passing WFGD; especially, SO42- in PM2.5, PM10-2.5, and PM>10 increase on average by about 1.4, 3.9, and 8.3 times, respectively. However, WESP before the stack can effectively reduce final PM emissions and their major ionic compositions. Furthermore, emission factors (kg/(t of coal)) of PM for different combinations of air pollution control devices are presented and discussed.

Atmospheric emission characteristics and control policies of five precedent-controlled toxic heavy metals from anthropogenic sources in China.

A bottom-up inventory of atmospheric emissions of five precedent-controlled toxic heavy metals (HMs), including mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd), and chromium (Cr), from primary anthropogenic sources in China is established for the period 2000­2010. Total emissions of HMs demonstrate a gradually ascending trend along with the increase of coal consumption and industrial production, which are estimated at approximately 842.22 t for Hg, 4196.31 t for As, 29272.14 t for Pb, 795.29 t for Cd, and 13715.33 t for Cr for 2010. Coal combustion is found to be the primary source of HMs emissions. Owing to the dramatic differences of coal use by industrial and power sectors among provinces, spatial allocation performs remarkably uneven characteristics, and spatial distribution features are demonstrated by allocating the emissions into 0.5° × 0.5° grid cells with GDP and population as surrogate indexes. Further, HMs emissions from specified anthropogenic sources under three different control scenarios for the target year 2015 are projected, and collaborative and specialized control strategies are proposed to meet the demand of emission reduction goals of different regions. In the future, a whole processes control management system will be the most effective way for control of HMs.

Atmospheric emission inventory of hazardous trace elements from China's coal-fired power plants--temporal trends and spatial variation characteristics.

Coal-fired power plants are the important sources of anthropogenic atmospheric releases of various hazardous trace elements (HTE) because a large quantity of emissions can cause wide dispersion and possible long-distance transportation. To obtain the temporal trends and spatial variation characteristics of various HTE discharged from coal-fired power plants of China, a multiple-year comprehensive emission inventory of HTE including Hg, As, Se, Pb, Cd, Cr, Ni, and Sb has been established for the period 2000-2010. Thanks to the cobenefit removal effects of conventional particulate matter/sulfur dioxide/nitrogen oxides (PM/SO2/NOx) control devices, emissions of these 8 toxic elements have shown a gradual decline since the peak in 2006. The total emissions of Hg, As, Se, Pb, Cd, Cr, Ni, and Sb are substantial and are estimated at about 118.54, 335.45, 459.4, 705.45, 13.34, 505.03, 446.42, and 82.33 tons (t), respectively, in 2010. Shandong, Jiangsu, Shanxi, and Hebei always rank among the top ten provinces with the highest emissions. Further, future emissions for 2015 and 2020 are projected with scenario analysis. Advanced technologies and integrated management strategies to control HTE are in great need.

A comprehensive global inventory of atmospheric Antimony emissions from anthropogenic activities, 1995-2010.

Antimony (Sb) and its compounds are considered as global pollutants due to their health risks and long-range transport characteristics. A comprehensive global inventory of atmospheric antimony emissions from anthropogenic activities during the period of 1995-2010 has been developed with specific estimation methods based on the relevant data available for different continents and countries. Our results indicate that the global antimony emissions have increased to a peak at about 2232 t (t) in 2005 and then declined gradually. Global antimony emissions in 2010 are estimated at about 1904 t (uncertainty of a 95% confidence interval (CI): -30% ∼ 67%), with fuel combustion as the major source category. Asia and Europe account for about 57% and 24%, respectively, of the global total emissions, and China, the United States, and Japan rank as the top three emitting countries. Furthermore, global antimony emissions are distributed into gridded cells with a resolution of 1° × 1°. Regions with high Sb emissions are generally concentrated in the Southeastern Asia and Western Europe, while South Africa, economically developed regions in the eastern U.S., and Mexico are also responsible for the high antimony emission intensity.

The Influence of Reinforced Fibers and Opacifiers on the Effective Thermal Conductivity of Silica Aerogels.

Fiber-particle-reinforced silica aerogels are widely applied in thermal insulation. Knowing their effective thermal conductivity (ETC) and radiative characteristics under high temperatures is necessary to improve their performance. This article first analyzes the radiation characteristics of silica aerogels doped with opacifier particles and reinforced fibers, and then a universal model is established to predict the ETC. Furthermore, the impacts of different parameters of opacifier particles and reinforced fibers on the thermal insulation performance of silica aerogels are investigated. The results indicate that SiC exhibits comparatively strong absorption characteristics, making it a good alternative for opacifiers to improve thermal insulation performance under high temperatures. For the given type and volume fraction of opacifier particles, there exists an optimal diameter and volume fraction to achieve the best insulation performance of silica aerogel under a certain temperature. Considering that SiO2 fibers exhibit a limited extinction capability and higher conductive thermal conductivity under high temperatures, for fiber-particle-reinforced silica aerogels, it is beneficial for their insulation performance to reduce the fiber volume fraction when the required mechanical properties are satisfied.

High spatiotemporal resolution ammonia emission inventory from typical industrial and agricultural province of China from 2000 to 2020.

As a typical industrial and agricultural province, Shandong is one of China's most seriously air-polluted regions. One comprehensive ammonia emission inventory with a high spatial resolution (1 km × 1 km) for 136 county-level administrative divisions in Shandong from 2000 to 2020 is developed based on county-level activity data with the corrected and updated emission factors of seventy-seven subcategories. Annual ammonia emissions decrease from 1003.3 Gg in 2000 to 795.9 Gg in 2020, with an annual decrease rate of 1.2 %. Therein, the ammonia emissions associated with livestock and farmland ecosystems in 2020 account for 50.8 % and 32.9 % of the provincial total ammonia emission, respectively. Laying hen and wheat are the livestock and crop with the highest ammonia emissions, accounting for 23.3 % and 36.3 % of ammonia emissions from livestock and the application of synthetic fertilizers, respectively. Furthermore, waste treatment, humans and vehicles are the top three ammonia emission sources in urban areas, accounting for 5.0 %, 4.7 % and 1.3 % of total ammonia emissions, respectively. The spatial distribution of grids with high ammonia emissions is consistent with the distribution of intensive farms. Significant emission intensity areas mainly concentrate in western Shandong (e.g., Caoxian of Heze, Qihe of Dezhou, Yanggu of Liaocheng, Liangshan of Jining) due to the large area of arable land and the high levels of agricultural activity. Overall, prominent seasonal variability characteristics of ammonia emission are observed. Ammonia emissions tend to be high in summer and low in winter, and the August to January-emission ratio is 5.6. The high temperature and fertilization for maize are primarily responsible for Shandong's increase in ammonia emissions in summer. Finally, the validity of the estimates is further evaluated using uncertainty analysis and comparison with previous studies. This study can provide information to determine preferentially effective PM2.5 control strategies.

Impact of greening trends on biogenic volatile organic compound emissions in China from 1985 to 2022: Contributions of afforestation projects.

The rapid expansion of green areas in China has enhanced carbon sinks, but it also presents challenges regarding increased biogenic volatile organic compound (BVOC) emissions. This study examines the impact of greening trends on BVOC emissions in China from 1985 to 2001 and from 2001 to 2022, focusing on evaluating long-term trends in BVOC emissions within eight afforestation project areas during these two periods. Emission factors for 62 dominant tree species and provincial Plant Functional Types were updated. The BVOC emission inventories were developed for China at a spatial resolution of 27 km × 27 km using the Model of Emissions of Gases and Aerosols from Nature. The national BVOC emissions in 2018 were estimated at 54.24 Tg, with isoprene, monoterpenes, sesquiterpenes, and other BVOC contributing 26.94 Tg, 2.29 Tg, 0.44 Tg, and 24.57 Tg, respectively. Over the past 37 years, BVOC emissions experienced a slow growth rate of 1.7 % (0.79 Tg) during 1985-2001, followed by a significant increase of 12 % (6 Tg) from 2001 to 2022. BVOC emissions in the eight afforestation project areas increased by 2 % and 20 % during the two periods. From 2001 to 2022, at the regional scale, the Shelterbelt program for the middle reaches of the Yellow River area exhibited the largest rate of increase (43 %) in BVOC emissions. The Shelterbelt program for the upper and middle reaches of the Yangtze River made the most largest contribution (45 %) to the national increase in BVOC emissions. Afforestation projects have shifted towards planting more broadleaf trees than needleleaf trees from 2001 to 2022, and there also showed a change from herbaceous plants to broadleaf trees. These trends have led to higher average emission factors for vegetation, resulting in increased BVOC emissions. It underscores the importance of considering BVOC emissions when evaluating afforestation initiatives, emphasizing the need to balancing ecological benefits with potential atmospheric consequences.

Nitrogen oxides emissions from thermal power plants in china: current status and future predictions.

Increasing emissions of nitrogen oxides (NOx) over the Chinese mainland have been of great concern due to their adverse impacts on regional air quality and public health. To explore and obtain the temporal and spatial characteristics of NOx emissions from thermal power plants in China, a unit-based method is developed. The method assesses NOx emissions based on detailed information on unit capacity, boiler and burner patterns, feed fuel types, emission control technologies, and geographical locations. The national total NOx emissions in 2010 are estimated at 7801.6 kt, of which 5495.8 kt is released from coal-fired power plant units of considerable size between 300 and 1000 MW. The top provincial emitter is Shandong where plants are densely concentrated. The average NOx-intensity is estimated at 2.28 g/kWh, markedly higher than that of developed countries, mainly owing to the inadequate application of high-efficiency denitrification devices such as selective catalytic reduction (SCR). Future NOx emissions are predicted by applying scenario analysis, indicating that a reduction of about 40% by the year 2020 can be achieved compared with emissions in 2010. These results suggest that NOx emissions from Chinese thermal power plants could be substantially mitigated within 10 years if reasonable control measures were implemented effectively.

Phase Equilibrium Studies in the Geothermal Energy Development: The Effect of Hydrogen Bond on the Multi-Component Fluid.

Geothermal energy has become an emerging resource with both large reserves and environmental friendliness and is playing an increasingly important role in the current energy transition progress. In this paper, a thermodynamically consistent NVT flash model is developed to consider the effect of hydrogen bond on the phase equilibrium states of multi-component fluid to resolve the challenges of the special thermodynamic characteristic of water as the main working fluid. In order to provide practical suggestions to the industry, a number of possible effects have been investigated on the phase equilibrium states, including the hydrogen bond, environmental temperature, and fluid compositions. The calculated phase stability and phase splitting results can provide thermodynamic foundations for the establishment of the multi-component multi-phase flow model and also help optimize the development process to control the phase transitions for a number of engineering purposes.

High spatiotemporal resolution vehicular emission inventory in Beijing-Tianjin-Hebei and its surrounding areas (BTHSA) during 2000-2020, China.

One comprehensive emission inventory of CO, HC, NOX, PM10, PM2.5, BC, CH4, CO2 and N2O with high spatial resolution (0.01° × 0.01°) for 58 cities in Beijing-Tianjin-Hebei and its surrounding areas (BTHSA) during 2000-2020 are developed by using COPERT model and ArcGIS methodology. The results show that vehicular emissions of CO, HC, NOX, PM10, PM2.5, BC and CH4 have begun to decrease or slow their growth rates in recent years due to the implementation of measures to control vehicular emissions. However, vehicular emissions of CO2 increase rapidly due to little fuel economy improvement. Besides, the usage of selective catalytic reduction (SCR) systems by heavy duty truck (HDT) is the main factor impacting the growth trend of vehicular N2O emissions since 2017. By 2020, vehicular emissions of CO, HC, NOX, PM10, PM2.5, BC, CO2, CH4 and N2O are estimated at about 1.65 Mt, 0.35 Mt, 1.39 Mt, 87.44 kt, 55.06 kt, 15.57 kt, 527.71 Mt, 36.20 kt and 8.56 kt, respectively. Therein, China III, IV, IV and IV passenger cars (PCs) are the predominated models for vehicular emissions of CO, HC, CH4 and CO2, accounting for 19.59-28.26 % of the total vehicular emission of corresponding pollutant. Nevertheless, the major contributors of vehicular emissions of NOX, PM10, PM2.5, BC and N2O are China III (29.64 %), III (18.03 %), III (22.81 %), III (42.16 %) and V (22.28 %) HDTs, respectively. The gridded vehicular emissions vary significantly, with emissions of CO, HC, CH4 and CO2 being mainly concentrated in central urban areas of cities (e.g., Beijing, Tangshan, Zhengzhou, Tianjin, Qingdao, Jinan). Nevertheless, the grids with high vehicular emissions of NOX, PM10, PM2.5, BC and N2O are mainly distributed along the expressway and the suburban roads of cities (e.g., Linyi, Tangshan, Jining, Weifang, Shijiazhuang, Tianjin, Baoding). Finally, multi-year uncertainties of vehicular emission inventory are discussed.