Emissions leakage embodied in inter-provincial trade brings unexpected air quality and health benefits.

Inter-provincial trade can bring "emission leakage", and consequently influence the air quality and public health. However, there has been a lack of systematic research on air pollution and public health related to emission leakage embodied in inter-provincial trade of China. Here, we systematically evaluated for the first time the influence of emission leakage on national air pollution and related premature deaths in 2012 of China. Unexpected opposite influences of emission leakage on emission and air quality/public health were discovered. Emission leakage embodied in inter-provincial trade in 2012 of China led to an increase of 1.4 % to 4.8 % in national air pollutant emissions, but a decrease of 1.5 % (-0.8 µg·m-3) in population-weighted concentration of PM2.5, while avoiding 1.1 % (-1.4 × 104 people) of premature deaths. Therefore, to reveal the intrinsic mechanism of this opposite influences, we proposed two coefficients, the Concentration per unit primary PM2.5 emission (CPE, unit: µg·m-3/t) and the Death per unit primary PM2.5 emission (DPE, unit: people/t), to characterize the response of air quality and health to emission leakage embodied in inter-provincial trade. Statistical analysis indicated that both the above coefficients showed significant negative correlation (P < 0.05) with provincial PM2.5 emissions changes. The findings offer a means of adjustment and its related evaluation parameters for the emission transfer caused by inter-provincial trade, thereby contributing to further improvement environmental and health benefits through inter-provincial trade.

The impacts of ship emissions on ozone in eastern China.

Tropospheric ozone (O3), which is one of the main pollutants impeding air quality compliance, has received considerable attention in China. As maritime transportation continues to expand, the effect of ship emissions on air quality is becoming increasingly important. In this study, the Weather Research and Forecast model (WRF), the Community Multiscale Air Quality model (CMAQ), and the integrated process rate (IPR) module provided in the CMAQ are applied to evaluate the impacts of ship emissions on O3 concentration at a national scale in China, including the spatiotemporal characteristics and influencing pathways. Ship emissions can increase or decrease O3 concentrations, with varying effects in different seasons and regions. In the winter, spring, and fall, ship emissions were predicted to decrease O3 concentrations in most areas, whereas in the summer, they increase the O3 concentration, even in regions far away from the coastline, thus adversely affecting the Yangtze River Delta (YRD) and Pearl River Delta (YRD). Additionally, owing to differences in the emissions of volatile organic compounds and nitrogen oxides, the northern and southern regions of the YRD respond differently to ship emissions. Additionally, the influence of ship emissions on the diurnal variation of O3 in the summer was investigated, where significant differences were indicated between cities. The IPR was used to investigate the individual processes contributing to changes in the O3 concentration caused by ship emissions. The transport process appears to be the primary contributor to O3 production, whereas chemistry and dry deposition played key roles in O3 loss. This study provides an in-depth insight into the impacts of ship emissions on O3 in China, which can facilitate the formulation of corresponding environmental policies.

Emission and influences of non-road mobile sources on air quality in China, 2000-2019.

Non-road mobile sources (NRMS) are potential important contributors to air pollution in China. However, their extreme impact on air quality had been seldom studied. In this study, the emission inventory of NRMS in mainland China during 2000-2019 was established. Then, the validated WRF-CAMx-PSAT model was applied to simulate the contribution to the atmospheric PM2.5, NO3-, and NOx. Results showed that emissions increased rapidly since 2000 and reached a peak in 2014-2015, with an annual average change rate (AACR) of 8.7-10.0%; after then, the emissions were relatively stable (AACR, -1.4-1.5%). The modeling results indicated that NRMS has become a crucial contributor to the air quality in China: from 2000 to 2019, the contribution to PM2.5, NOx, and NO3- significantly increased by 131.1%, 43.9%, and 61.7%; and for NOx, the contribution ratio in 2019 reached 24.1%. Further analysis showed that the reduction (-0.8% and -0.5%) of the NOx and NO3- contribution ratios was much lower than that (-4.8%) of NOx emissions from 2015 to 2019, implying that the control of NRMS lagged behind the national overall pollution control level. The contribution ratio of agricultural machinery (AM) and construction machinery (CM) to PM2.5, NOx, NO3- in 2019 was 2.6%, 11.3%, 8.3% and 2.5%, 12.6%, 6.8%, respectively. Although the contribution was much lower, the contribution ratio of civil aircraft had the fastest growth (202-447%). Moreover, an interesting phenomenon was that AM and CM had opposite contribution sensitivity characteristics for air pollutants: CM had a higher Contribution Sensitivity Index (CSI) for primary pollutants (e.g., NOx), ∼1.1 times that of AM; while AM had a higher CSI for secondary pollutants (e.g., NO3-), ∼1.5 times that of CM. This work can provide a deeper understanding for the environmental impact of NRMS emissions and for the control strategy formulation of NRMS.

Key emergency response technologies for abrupt air pollution accidents in China.

Abrupt air pollution accidents can endanger people's health and destroy the local ecological environment. The appropriate emergency response can minimize the harmful effects of accidents and protect people's lives and property. This paper provides an overview of the key emergency response technologies for abrupt air pollution accidents around the globe with emphasis on the major achievements that China has obtained in recent years. With decades of effort, China has made significant progress in emergency monitoring technologies and equipment, source estimation technologies, pollutant dispersion simulation technologies and others. Many effective domestic emergency monitoring instruments (e.g., portable DOAS/FT-IR systems, portable FID/PID systems, portable GC-MS systems, scanning imaging remote sensing systems, and emergency monitoring vehicles) had been developed which can meet the demands for routine emergency response activities. A monitoring layout technique combining air dispersion simulation, fuzzy comprehensive evaluation, and a post-optimality analysis was proposed to identify the optimal monitoring layout scheme under the constraints of limited monitoring resources. Multiple source estimation technologies, including the forward method and the inversion method, have been established and evaluated under various scenarios. Multi-scale dynamic pollution dispersion simulation systems with high temporal and spatial resolution were further developed. A comprehensive emergency response platform integrating database support, source estimation, monitoring schemes, fast monitoring of pollutants, pollution predictions and risk assessment was developed based on the technical idea of "source identification - model simulation - environmental monitoring" dynamic interactive feedback. It is expected that the emergency response capability for abrupt air pollution accidents will gradually improve in China.

Atmospheric environment monitoring technology and equipment in China: A review and outlook.

Accurate monitoring of the atmospheric environment and its evolution are important for understanding the sources, chemical mechanisms, and transport processes of air pollution and carbon emissions in China, and for regulatory and control purposes. This study gives an overview of atmospheric environment monitoring technology and equipment in China and summarizes the major achievements obtained in recent years. China has made great progress in the development of atmospheric environment monitoring technology and equipment with decades of effort. The manufacturing level of atmospheric environment monitoring equipment and the quality of products have steadily improved, and a technical & production system that can meet the requirements of routine monitoring activities has been initiated. It is expected that domestic atmospheric environment monitoring technology and equipment will be able to meet future demands for routine monitoring activities in China and provide scientific assistance for addressing air pollution problems.

Impact of fireworks burning on air quality during the Spring Festival in 2021-2022 in Linyi, a central city in the North China Plain.

The management of fireworks has been strengthened during the Spring Festival in 2022 compared with that in 2021 in Linyi, a central city in the North China Plain. Online measurements of the chemical components of PM2.5 were conducted during the Spring Festival in 2021-2022 to assess the influence of fireworks burning (FB) on air quality. Remarkable achievements have been made in improving air quality during FB period (FBP) in 2021-2022 attributing to the stringent regional emission reduction measures, fireworks control, and favorable meteorological conditions with the concentrations of PM2.5, water-soluble ions, and carbonaceous aerosols decreasing by 73.6%, 78.8%, and 73.5%, respectively. The PM2.5 concentrations increased by 96.3% during FBP compared with those during non-FB period (NFBP) in 2021, while the opposite phenomenon was observed in 2022 with PM2.5 concentrations decreasing by 56.2% because of the favorable meteorological condition during FBP in 2022. As indicators of FB, the Cl-, K+, and Mg2+ concentrations showed an increasing trend during FBP compared with that during NFBP, both in 2021 and 2022, but had little effect on other components. The contribution of FB to PM2.5 decreased from 68.4% in 2021 to 15.7% in 2022 based on the relative ratio method, indicating the various measures conducted by all districts and counties in Linyi helped achieve near zero fireworks emissions by 2022. Besides, the contribution of FB to PM2.5 showed a straight-line upward trend from 19:00 on New Year's Eve, reached its peak (76.1%) at 3:00 on Lunar New Year's Day, while the highest value was only 35.0% during FBP in 2022, indicating the implementation of fireworks ban measures in Linyi achieved a good effect on pollution peak cutting. This study has emphasized the necessity of FB restricting during special holidays.

Ozone pollution in the plate and logistics capital of China: Insight into the formation, source apportionment, and regional transport.

As the logistics and plate capital of China, the sources and regional transport of O3 in Linyi are different from those in other cities because of the significant differences in industrial structure and geographical location. Twenty-five ozone pollution episodes (OPEs, 52 days) were identified in 2021, with a daily maximum 8-h moving average O3 concentration (O3-MDA8) of 184.5 ± 22.5 µg/m3. Oxygenated volatile organic compounds (OVOCs) and aromatics were the dominant contributors to ozone formation potential (OFP), with contributions of approximately 23.5-52.7% and 20.0-40.8%, respectively, followed by alkenes, alkanes, and alkynes. Formaldehyde, an OVOC with high concentrations emitted from the plate industry and vehicles, contributed the most to OFP (22.7 ± 5.5%), although formaldehyde concentrations only accounted for 9.4 ± 2.7% of the total non-methane hydrocarbon (NMHC) concentrations. The source apportionment results indicated that the plate industry was the dominant O3 contributor (27.0%), followed by other sources (21.6%), vehicle-related sources (18.0%), solvent use (16.9%), liquefied petroleum gas (LPG)/natural gas (NG) (8.8%), and combustion sources (7.7%). Therefore, there is an urgent need to control the plating industry in Linyi to mitigate O3 pollution. The backward trajectory, potential source contribution function (PSCF), and concentration weighted trajectory (CWT) models were used to identify the air mass pathways and potential source areas of air pollutants during the OPEs. O3 pollution was predominantly affected by air masses that originated from eastern and local regions, while trajectories from the south contained the highest O3 concentrations (207.0 µg/m3). The potential source area was from east and south Linyi during the OPEs. Therefore, it is critical to implement regional joint prevention and control measures to lower O3 concentrations.

A coupled framework for estimating pollutant emissions from open burning of specific crop residue: A case study for wheat.

Crop residue open burning is considered to be one of the main sources of pollutant emissions from rural areas. It is necessary to accurately establish an emissions inventory of specific crops which could reflect the specific spatiotemporal distribution characteristics of crop residue burning emissions. However, the information for emission estimation of specific crop in each province and year is seriously data-deficient, resulting in a large uncertainty in the emissions inventory. In this study, taking the open burning of wheat residue as an example, we propose a framework for estimating pollutant emissions for specific crop residue by combining phenological information, land use data, field investigation/statistical data, and fire detection information. The wheat residue open burning proportion (OBP) and the corresponding pollutant emissions were estimated for each province in mainland China from 2003 to 2019. The national average OBP and emissions of wheat crop residue open burning first increased and then decreased during this period, with the peak in 2012. The gridded spatial distribution showed that high-emission areas were mainly concentrated in central-eastern China, and the emission areas gradually shifted from south to north from April to September. The change of daily emissions from large-scale concentrated emissions to small-scale emissions demonstrated that straw open burning prohibition policies were effective in reducing the annual emissions and peak daily emissions. This study provides a promising method for the combination of data from multiple sources to estimate open burning of crop residues. The method can be used to obtain accurate and detailed emissions data to support research into biomass burning and the development of targeted mitigation strategies.

Estimating air pollutant emissions from crop residue open burning through a calculation of open burning proportion based on satellite-derived fire radiative energy.

Crop residue open burning has substantial negative effects on air quality, human health, and climate change, and accurate and timely estimates of its air pollutant emissions are essential. Open burning proportion (OBP) is the key parameter in estimating the emission from the crop residue open burning by bottom-up method. However, the OBP is mainly obtained by field investigation, which consumes much time, manpower and financial resources, leading to the OBP data deficient seriously. In this study, the significant logarithmic relations were found between OBP and fire radiative energy (FRE), and then the FRE-based OBP estimation models were developed for different regions of China. The comparison between the FRE-based OBP and the field-investigated OBP illustrated the reliability of the developed models (r = 0.71, NMB = -8% and NME = 25%). The OBPs of different municipalities/provinces in mainland China from 2003 to 2018 were further calculated. The results showed that the estimated OBP variation exhibited fluctuating upward trend with annual mean growth rate of 3.7% from 2003 to 2014, while dramatically decreased with annual mean reduction rate of 5.9% from 2014 to 2018. The estimation accuracy of emission from open biomass burning can also be can be significantly improved by basing on the year-specific OBP, compared with the calculation based on fixed OBP. The annual PM2.5 emissions would decrease 4.5%-25.9% and increase 6.6%-30.7% in the scenarios of a fixed OBP during 2003-2014 and 2014-2018, respectively. The developed models complemented the severely missing OBP data of mainland China for the first time. By combining the advantages of bottom-up approach and FRE method, the proposed FRE-based models can avoid their disadvantages, and can help to get more accurately and timely emissions from crop residue open burning.

Improving source inversion performance of airborne pollutant emissions by modifying atmospheric dispersion scheme through sensitivity analysis combined with optimization model.

Estimating accurately airborne pollutant emissions source information (source strength and location) is important for achieving effective air pollution management or adequate emergency responses to accidents. Inversion method is one of the useful tools to identify the source parameters. The atmospheric dispersion scheme has been proven to be the key to determining the source inversion performance by influencing the accuracy of the dispersion models. Modifying the atmospheric dispersion scheme is an important potential method to improve the inversion performance, but this has not been studied previously. To fill this gap, a novel approach for parameter sensitivity analysis combined with an optimization method was proposed to improve the source inversion performance by optimizing empirical scheme. The dispersion coefficients σy and σz of the typical BRIGGS scheme under different atmospheric dispersion conditions were optimized and used for air pollutant dispersion and source inversion. The results showed that the prediction performance of the air pollutant concentrations was greatly improved with statistical indices |FB| and NMSE decreased by 0.22 and 2.07, respectively; FAC2 and R increased by 0.10, and 0.08, respectively. For source inversion, the results of the significance analysis suggested that the accuracy in the source strength and location parameter (x0) were both significantly improved by ∼271% (relative deviation reduced from 60.0% to 16.2%) and ∼121% (absolute deviation reduced from 27.6 to 12.5 m). The improvement of source strength inversion accuracy was more significant under unstable atmospheric conditions (stability class A, B, and C); the mean absolute relative deviation was reduced by 97.5%. These results can help to obtain more accurate source information and to provide reliable reference for air pollution managements or emergency response to accidents. This study provides a novel and versatile approach to improve estimation performance of pollutant emission sources and enhances our understanding of source inversion.

Improved estimation of rural residential coal emissions considering coal-stove combinations and combustion modes.

Rural residential coal combustion (RRCC) has detrimental effects on air quality, climate, and human health. There are large uncertainties regarding emissions from RRCC owing to the lack of consideration of several key factors (e.g. combination modes of coal and stoves, combustion modes, and high temporal resolution). In this study, we provided a new estimation framework for RRCC emissions through a case study in the Beijing-Tianjin-Hebei (BTH) region, China. The emission estimations were improved according to four aspects, namely (1) coal-specific and stove-specific coal consumption was calculated based on face-to-face field interviews of 6700 valid volunteers/households covering 288 villages in 50 counties; (2) the influences of combustion modes (flaming and smoldering modes) on emissions were considered; (3) emissions of different fuel-stove combinations were estimated based on coal, stove, and combustion mode-specific RRCC consumption and localised emission factors; and (4) a method for emission estimation with high temporal resolution (1 h) was developed. The results indicated that RRCC emitted 413.6 kt SO2, 55.7 kt NOx, 5717.3 kt CO, 149.4 kt VOCs, 167.1 kt PM2.5, 18.2 kt EC, 32.5 kt OC, and 8.2 kt NH3 in 2016. The combination of bituminous coal and an advanced coal stove was the most significant contributor (20.7-71.8%) to various pollutant emissions. Coal combusted under the flaming mode contributed to most (81.9%) of the total coal consumption, and thus emitted the majority (50.8-99.8%) of pollutants, except for VOCs. Meanwhile, that under the smoldering mode only accounted for 18.1% of the total consumption, but contributed 49.2% and 74.7% of the CO and VOCs emissions, respectively. Two clear emission peaks occurred at approximately 7:00-9:00 and 18:00-20:00. The detailed coal consumption and emissions with high temporal and spatial resolution can provide sound data for further research on rural environmental issues and scientific support to pollution control strategies.

Air pollution episodes during the COVID-19 outbreak in the Beijing-Tianjin-Hebei region of China: An insight into the transport pathways and source distribution.

Although anthropogenic emissions decreased, polluted days still occurred in the Beijing-Tianjin-Hebei (BTH) region during the initial outbreak of the coronavirus disease (COVID-19). Analysis of the characteristics and source distribution of large-scale air pollution episodes during the COVID-19 outbreak (from 23 January to April 8, 2020) in the BTH region is helpful for exploring the efficacy of control measures and policy making. The results indicated that the BTH region suffered two large-scale air pollution episodes (23-28 January and 8-13 February), which were characterized by elevated PM2.5, SO2, NO2, and CO concentrations, while the O3 concentration decreased by 1.5%-33.9% (except in Shijiazhuang, where it increased by 16.6% during the second episode). These large-scale air pollution episodes were dominated by unfavorable meteorological conditions comprising a low wind speed and increased relative humidity. The transport pathways and source distribution were explored using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT), potential source contribution function (PSCF), and concentration weighted trajectory (CWT) models. The air pollution in the BTH region was mainly affected by local emission sources during the first episode, which contributed 51.6%-60.6% of the total trajectories in the BTH region with a PM2.5 concentration ranging from 146.2 µg/m3 to 196.7 µg/m3. The short-distance air masses from the southern and southwestern areas of the BTH region were the main transport pathways of airflow arriving in the BTH region during the second episode. These contributed 51.9%-57.9% of the total trajectories and originated in Hebei, Henan, central Shanxi, and Shaanxi provinces, which were the areas contributing the most to the PM2.5 level and exhibited the highest PSCF and CWT values. Therefore, on the basis of local emission reduction, enhancing regional environmental cooperation and implementing a united prevention and control of air pollution are effective mitigation measures for the BTH region.

Impact of rural residential coal combustion on air pollution in Shandong, China.

Rural residential coal combustion (RRCC) for household heating is a potentially important source of air pollution. However, little research has been done on the environmental impacts of RRCC. This study therefore investigated the impacts of RRCC on air pollution based on detailed household heating data obtained from intensive face-to-face interviews in Shandong province, China. The total contributions and specific contributions of coal, stoves, and coal-stove combinations to air pollution were simulated using the WRF-CAMx-PSAT model. The RRCC for heating had a considerable impact on air pollution, contributing 36.1, 9.1, and 16.1% of atmospheric SO2, NOx, and PM2.5 in winter, respectively. Different coal-stove combinations had different impacts on air pollution and mitigation efficiencies. The combination of bituminous coal and advanced coal stoves was the dominant contributor to air pollution, comprising 60.3-68.8% of the total RRCC contribution to different air pollutants. Sensitivity analyses indicated that bituminous coal burnt in a traditional stove had the highest mitigation efficiency (0.67 µg·m-3/10 kt) for atmospheric PM2.5 pollution, 4.1 times higher than that of anthracite briquette coal burnt in advanced coal stoves. Moreover, although RRCC is a near-surface emission source, it contributed considerably to regional pollution. Non-local RRCC emissions accounted for 21.8-74.6, 15.5-72.3, and 35.3-79.9% of the total contribution to SO2, NOx, and PM2.5 in different cities, respectively. The findings of this study improve understanding on the environmental impacts of rural emissions and can provide scientific support for the formulation of effective air pollution mitigation strategies.

Influence of Phosphorus Slag on Physical and Mechanical Properties of Cement Mortars.

Influences of phosphorus slag from 10% to 50% (by mass) on the setting time and the water requirement of the normal consistency of cement pastes, flowability, resistance to carbonation, and the compressive strength of cement mortars were investigated. The physical activation by improving fineness and the chemical activation by adding the chemical activator were evaluated by the compressive strength of cement mortars with 30% by mass of phosphorus slag. Hydration heat, X-ray diffraction, and scanning electron microscopy were used to study the microstructure of cement pastes and mortars with 30% by mass of phosphorus slag and the chemical activator. Results showed that the setting time of cement pastes was delayed by phosphorus slag from 10% to 50%. Phosphorus slag had nearly no effects on the water requirement of the normal consistency of cement pastes and the flowability of cement mortars. The resistance to carbonation of cement mortars was decreased by phosphorus slag from 10% to 50% according to the acceleration carbonation. The compressive strength of cement mortars was also decreased by phosphorus slag from 10% to 50% and the low activity of phosphorus slag was concluded based on compressive strength of cement mortars. The effect of the chemical activator on the compressive strength of cement mortars with 30% by mass of phosphorus slag was better than improving fineness of phosphorus slag from 300 m2/kg to 450 m2/kg. Both hydration heat and cement hydrates were inhibited by phosphorus slag and could be partly compensated by the chemical activator. Loose morphology and propagations of microcracks were found in cement pastes and mortars with 30% by mass of phosphorus slag.

The impact of ship emissions on nitrogen and sulfur deposition in China.

A large amount of NOX and SO2 emitted from ships may elevate atmospheric N and S and eventually aggravate the deposition of N and S. The understanding of N and S deposition due to ship emissions is still limited, especially for China because it has a long coastline, busy shipping routes, and several large ports. To fill this gap, a comprehensive air quality model was employed in this study to quantify the contributions of ship emissions to N and S deposition on a national scale in China. Both the spatial and temporal variations of N and S deposition, as well as the major N and S species from ship traffic, were investigated. The results indicate that ship emissions contributed significantly to the deposition of N and S, especially in coastal and offshore areas, where the largest ship contribution to both N and S deposition could exceed 15 kg·ha-1·yr-1. For N deposition, ship emissions caused an increase in the total N deposition, not only in port areas and along shipping routes but also far inland, with evident seasonal variations. The contribution from dry N deposition was evidently larger than wet N deposition, especially over the coastal areas. S deposition, however, was generally higher along shipping routes but exhibited distinct seasonal variations. The total S deposition was dominated by dry deposition, especially over offshore areas. Ship-caused dry S deposition occurred mainly in offshore areas, while wet S deposition could be found over wider inland regions and inland waterways, although with a markedly smaller magnitude.

Trends in ammonia emissions from light-duty gasoline vehicles in China, 1999-2017.

Ammonia (NH3) emitted from motor vehicles is a by-product of measures taken to reduce emissions of other pollutants (e.g. NOx and CO) and has potentially important environmental impacts. NH3 levels can be impacted by various emission standards. However, there is a lack of investigations of the influences from the implementation of different vehicular emission standards on long-term changes in NH3 emissions. To fill this gap, we estimated the inter-annual NH3 emissions of light-duty gasoline vehicles (LDGVs) under different emission standards (State 0 to State V) from 1999 to 2017 and investigated the emission change characteristics under the rapidly developing Chinese economy. Results showed that the NH3 emissions from LDGVs had a sharp, 42-fold increase (from 1.8Gg to 77.9Gg). However, NH3 emissions per capita have begun to decrease with increases in socioeconomic development, presenting an inverted U-shaped tendency as a function of per capita GDP. Further exploration indicated that the decline in emission factors, as determined by upgrades in emission standards, was the decisive factor in promoting the downward trend in per capita emissions. This suggests that continuously upgrading emission standards has offset the increase in NH3 emissions due to the rapid growth of motor vehicles. Quantitative scenario analysis showed a two-stage impact of emission standards on NH3 emissions: emissions would decrease 77% (48%-90% for different years) if State I and State II were not implemented; while if none of standards were upgraded (State III to State V), NH3 emissions would increase 118% (13%-224% for different years), 2-6 times the impacts from the growth of vehicle population and the decline of vehicle kilometres traveled. The data and findings in this study can provide scientific support for understanding air pollution in urban areas and for formulating further vehicle pollution mitigation measures in China and other countries.

[Characteristics of PM2.5 Pollution and the Efficiency of Concentration Control During a Red Alert in the Beijing-Tianjin-Hebei Region, 2016].

The Beijing-Tianjin-Hebei (BTH) region experienced a heavy pollution episode in December 2016. Beijing and Tianjin issued a red alert from 20:00 December 16 to 24:00 December 21, while every city in Hebei Province (except Zhangjiakou, Chengde, and Qinhuangdao) issued a red alert from 00:00 December 16 to 18:00 December 22. In order to study the process of heavy pollution and the effect of implementing emergency measures, pollutant concentrations, meteorological conditions, air mass transmission and region transmission, and control effects were analyzed based on environmental monitoring data and simulation. Mean PM2.5 concentrations during the heavy pollution episode in each city all exceeded 200 µg·m-3 and the peak value of hourly averaged concentration (834.5 µg·m-3) occurred in Handan. The meteorological conditions during the heavy pollution episode restricted the diffusion of pollutants, with low pressure and air mass transmission exacerbating the problem. The mean fraction of PM2.5 concentrations in local emissions was 47.1%, but this differed between cities due to variable meteorological conditions. The average reduction of PM2.5 concentrations was 27.6%, indicating that the implementation of a red alert measure was effective. If the emergency measures had been implemented a few days earlier, a greater reduction ratio would have been achieved; a 4.4% greater average reduction in PM2.5 concentrations would have occurred if the measures were implemented two days earlier, while taking action three or more days in advance would not have achieved significant improvement.

A framework for investigating the air quality variation characteristics based on the monitoring data: Case study for Beijing during 2013-2016.

In this study, an analysis framework based on the regular monitoring data was proposed for investigating the annual/inter-annual air quality variation and the contributions from different factors (i.e., seasons, pollution periods and airflow directions), through a case study in Beijing from 2013 to 2016. The results showed that the annual mean concentrations (MC) of PM2.5, SO2, NO2 and CO had decreased with annual mean ratios of 7.5%, 28.6%, 4.6% and 15.5% from 2013 to 2016, respectively. Among seasons, the MC in winter contributed the largest fractions (25.8%~46.4%) to the annual MC, and the change of MC in summer contributed most to the inter-annual MC variation (IMCV) of PM2.5 and NO2. For different pollution periods, gradually increase of frequency of S-1 (PM2.5, 0~75 µg/m3) made S-1 become the largest contributor (28.8%) to the MC of PM2.5 in 2016, it had a negative contribution (-13.1%) to the IMCV of PM2.5; obvious decreases of frequencies of heavily polluted and severely polluted dominated (44.7% and 39.5%) the IMCV of PM2.5. For different airflow directions, the MC of pollutants under the south airflow had the most significant decrease (22.5%~62.5%), and those decrease contributed most to the IMCV of PM2.5 (143.3%), SO2 (72.0%), NO2 (55.5%) and CO (190.3%); the west airflow had negative influences to the IMCV of PM2.5, NO2 and CO. The framework is helpful for further analysis and utilization of the large amounts of monitoring data; and the analysis results can provide scientific supports for the formulation or adjustment of further air pollution mitigation policy.

Improved estimation of air pollutant emissions from landing and takeoff cycles of civil aircraft in China.

Civil aircraft emissions during landing and takeoff (LTO) are important air pollutant sources, but have been given insufficient attention in China. Accurate estimation of these emissions is limited by a lack of important parameters, such as detailed flight information and the dynamic time in climb and approach modes during LTO that are dependent on mixing layer height (MLH). We developed a flight-time/flight-height relationship using real-time height information in Aircraft Meteorological Data Relay data, and then calculated the actual time for each flight in those two modes based on the actual MLH from meteorological observation. Hourly emissions of civil aircraft were then estimated based on the database of each flight. Total emissions of NOx, CO, SO2, HC and PM from LTO cycles of domestic flights in China during 2015 were 37.78 Gg, 30.25 Gg, 12.00 Gg, 2.38 Gg and 0.75 Gg, respectively. Substantial monthly, daily and hourly variations of emissions due to the flight schedule as well as MLH were calculated. Large differences were found between the new estimation and emissions calculated based on traditional method. Compared with the emissions estimated based on default parameter obtained from International Civil Aviation Organization, the average difference of annual emission among airports with new estimation for various pollutants was approximately 30.3% in climb mode and 81.4% in approach mode; compared with the emissions estimated based on the method proposed by China National Guide, the average difference of annual emission among airports were 37.4% (NOx), 8.4% (CO), 73.1% (HC) and 58.1% (PM) during LTO process. The monthly airport-specific emissions per LTO were also proposed. These can provide necessary and meaningful support for the revision of the values in National Guide.

The impact of ship emissions on PM2.5 and the deposition of nitrogen and sulfur in Yangtze River Delta, China.

Ship emissions contribute significantly to the deterioration of air quality, while their impacts on ambient PM2.5 and depositions have not been comprehensively evaluated. This is especially true for China because it has a long coastline, busy shipping routes and many large ports. To fill this gap, this study applied the SMOKE/WRF/CMAQ modeling system to quantifying the impacts of ships on PM2.5 compositions, annual and seasonal contribution to PM2.5 as well as the wet and dry deposition of nitrogen and sulfur compounds over the land areas in YRD region for 2014. The results showed that 4.0% of annual PM2.5 concentrations over the land areas could be explained by ship emissions and the largest contribution could reach up to 35.0% in port areas. Temporally, the contribution to PM2.5 exhibited an obviously seasonal variation. The highest contribution was predicted in autumn (6.2%), followed by summer (5.4%), spring (3.6%) and winter (1.2%) for the land areas. Spatially, the contribution reached up to 13.6% along the coastline and dropped to 2.1% 300 km inland. As for the impacts on PM2.5 components, the primary components were relatively small and increased mainly along the shipping routes and the Yangtze River, whereas the secondary components played a more important role in both water and land areas. The sulfur deposition due to ship emissions was occurred generally along the shipping routes and was dominated by the dry SO2 deposition. The nitrogen depositions, on the contrary, was observed not only along the shipping routes but also extend to wide land areas. Further investigation revealed that ship emissions have caused an evident increase of dry nitrogen deposition in NO2 and HNO3, while a slight decrease in NH3 over YRD region. These results indicated that comprehensive regulations of ship emissions are required considering their adverse effects on the ambient concentration of PM2.5 and the deposition of sulfur and nitrogen.