Emission Control Measures Research Articles

Long-Term Air Quality Study in Fairbanks, Alaska: Air Pollutant Temporal Variations, Correlations, and PM2.5 Source Apportionment

As one of the most polluted U.S. cities, Fairbanks was reclassified as a “serious” nonattainment area by the Environmental Protection Agency (EPA) in 2017 for its fine particulate matter (PM2.5) pollution. In this study, November 2013–May 2019 observations of criteria air pollutants (NO2, SO2, CO, O3, PM2.5, and inhalable particulate matter (PM10)) and meteorological parameters (temperature, wind speed, and relative humidity) in Fairbanks were used for temporal variation and correlation analysis, with positive matrix factorization (EPA PMF 5.0) adopted for further PM2.5 source identification. All pollutants exhibited obvious seasonal trends under the influence of climatology, topography, and human activity, while abnormal patterns likely resulted from occasional emission events such as wildfires. Primary and secondary pollutants performed distinctively under similar meteorological conditions due to different decisive factors. Identified PM2.5 sources included sulfate (32.7%), wood smoke (19.3%), gasoline (18.3%), nitrate (15.7%), diesel (9.2%), soil (3.8%), and road salt (1.0%). Compared with the 2005–2012 result, sulfate and nitrate contributions had increased, while wood smoke and diesel contributions had decreased, in which emission control measures as well as a change of sampling sites could play an important role. This systematic analysis offers reference for mitigation measures and pollution prediction. Meanwhile, further field investigation is required for conclusion validation and model improvement.

Identification of long-term evolution of ozone sensitivity to precursors based on two-dimensional mutual verification

Tropospheric ozone pollution has been continuously worsening in China during the past decade. Identification of long-term evolution of ozone sensitivity to precursors is essential to evaluating the impact of emission reduction measures on ozone pollution. Traditional observation-based model and 3-d numerical model are not suitable for analyzing long-term variation of ozone sensitivity to precursors. In this study, by transforming the conventional ozone isopleth plot into a VOCR isopleth plot in the functional space of NOx and ozone concentrations, we developed a novel approach to identify ozone sensitivity to precursors by simply using long-term monitoring data of ozone, NOx and temperature. This approach estimated ozone formation regimes (OFR) by ozone sensitivity to NOx and temperature separately, and the convergence of OFR serves as a way of mutual verification. We found that ozone formation was generally in the VOCR-limited or transitional regime in Shanghai, the largest metropolitan area in China. However, OFR was shifted to NOx-limited at Pudong station during 2017–19 due much to the stringent NOx emission control. OFR was also shifted to NOx-limited along with the increasing temperature. When temperature was over 30 °C, Shanghai was mostly in a NOx-limited OFR. This highlights that the NOx emission control measures need to be strengthened to reduce peak ozone levels more efficiently. Jinshan station exhibited a different trend with OFR shifted to VOCR-limited in 2017–19, which proved the effectiveness of VOCs emission control on petrochemical sector. However, OFR was shifted to NOx-limited when temperature was over 30 °C, suggesting more stringent VOCs emissions control should be targeted on days with higher temperature.

Transport and boundary layer interaction contribution to extremely high surface ozone levels in eastern China.

Vertical measurements of ozone (O3) within the 3000-m lower troposphere were obtained using an O3 lidar to investigate the contribution of the interactions between the transport and boundary layer processes to the surface O3 levels in urban Shanghai, China during July 23-28, 2017. An extremely severe pollution episode with a maximum hourly O3 mixing ratio of 160.4ppb was observed. In addition to enhanced local photochemical production, both downward and advection transport in the lower troposphere may have played important roles in forming the pollution episode. The O3-rich air masses in the lower free troposphere primarily originated from central China and the northern Yangtze River Delta (YRD) region. The downward transport of O3 from the lower free troposphere may have an average contribution of up to 49.1% to the daytime (09:00-16:00 local time) surface O3 in urban Shanghai during the pollution episode (July 23-26, 2017). As for the advection transport, large amounts of O3 were transported outward from Shanghai in the planetary boundary layer under the influence of southeasterly winds during the field study. In this condition, the boundary-layer O3 that was transported downward from the free troposphere in Shanghai could be transported back to the northern YRD region and accumulated therein, leading to the occurrence of severe O3 pollution events over the whole YRD region. Our results indicate that effective regional emission control measures are urgently required to mitigate O3 pollution in the YRD region.

Source apportionment of PM2.5 in the most polluted Central Plains Economic Region in China: Implications for joint prevention and control of atmospheric pollution

With continuous strengthening of emission control actions, the air quality in northern China during winter has been improved in recent years. However, the fine particulate matter (PM2.5) concentration remains high in the Central Plains Economic Region (CPER). The Nested Air Quality Prediction Modeling System coupled with an on-line source-tagged model was applied to investigate the source apportionment of primary and secondary PM2.5 in the most polluted area of China from November 2017 to March 2018. On average, local emissions represent the largest contributor to ambient PM2.5 levels, followed by transport from circumjacent cities at five receptors in northern CPER. Under high PM2.5 concentrations (more than 150 μg/m3), 60%–70% of the primary PM2.5 is freshly emitted on the current day, while the contribution of the current day, one day ago, and two or more days ago are comparable to secondary aerosols. The estimation of contributions based on distance shows that the contribution from regions within 200 km reaches more than 80% of the primary PM2.5, while the contribution from long-range transport within 200–500 km still accounts for more than 20% of the secondary PM2.5 at the receptor sites. These results indicate that control measures of primary particle emission should be effective to reduce the primary PM2.5 levels within local and nearby regions, and control measures of gas phase precursors one or more days in advance should be beneficial to surrounding regions within 500 km. The process analysis results of the change in PM2.5 mass over the northern part of the CPER during increased PM2.5 periods illustrate that the existing particle total transport is smaller than the secondary aerosol chemical production and primary aerosol emissions since the westerly and southerly net inputs are mostly offset by the large net outputs at the east boundary in both cases. This finding indicates that the ambient PM2.5 mass in a selected area is strongly affected by the upstream region; meanwhile, the PM2.5 in this area also spreads to the downstream region. Joint prevention and control measures that cooperate with upstream regions for both primary particles and gas phase precursor emissions are crucial for improving the air quality over polluted areas. As the emission control measures would lead to some economic losses, beneficiary downstream regions could reasonably provide certain economic compensation to upstream regions if emergency control measures are taken.

Vertical distributions of boundary-layer ozone and fine aerosol particles during the emission control period of the G20 summit in Shanghai, China

Vertical observations of ozone (O3) and fine aerosol particles (PM2.5) below 3000 m above ground level were made by an O3 lidar and two hexacopter unmanned aerial system (UAS) platforms to investigate vertical distributions of the boundary-layer O3 and PM2.5 and their effects on surface air quality. Field observations were conducted in Shanghai, China before, during, and after the G20 Summit (Hangzhou) from 23 August to 13 September 2016, when stringent emission control measures were implemented over the Yangtze River Delta region. The results show that surface O3 and PM2.5 concentrations increased evidently during the emission control period due to the significant contribution of transport. Different transport types including regional transport, recirculation transport, and long-range transport were captured in the three stages of the emission control period. Regional transport mainly occurred in the middle and upper boundary layer, leading to positive altitude dependence of the boundary-layer O3 and PM2.5. Recirculation transport mainly occurred in the lower boundary layer, leading to negative altitude dependence of the boundary-layer O3 and PM2.5. Long-range transport of O3 mainly occurred in the lower free troposphere, leading to positive altitude dependence of the boundary-layer O3. Under the influence of northeasterly winds, Shanghai exhibited considerable transport potential of pollutants to Hangzhou during the emission control period. The findings in this study could help to understand complex interactions between different transport types and variations in surface air pollutant concentrations, as well as provide important implications in making regional emission control measures in the future.

Carbon emission assessment and control measures for coal mining in China

Coal is the most important primary energy in China. Although the proportion of coal in China's total energy consumption continues to decline it will still be the main energy in China for a long time in the future. As the largest contributor to China's greenhouse gas emissions, the energy conservation and emission reduction of coal industry will be the most critical step for China to cope with global climate change and solve environmental problems at present and in the future for a long time. The object of this study was coal mining in China. Life cycle assessment (LCA) was used to quantify carbon emissions in whole process of coal mining, including mining, ventilation, drainage, power consumption, transportation, and post-mining activities. The analysis result shows that the carbon emissions of producing tons of coal are 164.403 kg of carbon dioxide equivalent per ton. The analysis further emphasizes that the methane contributes the most, accounting for 62.21% of the total emissions, and plays an important role in the full life cycle of coal mining. Therefore, it presents a potential to mitigate the environmental impact of coal mining, and its main task is to recover and recycle methane. Based on the technical level, this study puts forward the low-carbon development countermeasures for coal enterprises. Then the technical system of methane emission control and utilization is constructed from three aspects: coal-bed methane development, gas extraction, and utilization and gas utilization. Finally, a trinity resource utilization system of coal mine gas is constructed. This study hopes to help practitioners to realize the importance of coal mine methane to the coal mining process. If the efficient resource utilization of methane be realized, it could not only save energy and reduce emissions in coal enterprises, but also promote the safety production of coal mines and improve the economic benefits of coal mines. It is also of great significance for optimizing China's energy structure, realizing low-carbon transformation, and safeguarding China's strategic energy security.

Health benefits of on-road transportation pollution control programs in China

China started to implement comprehensive measures to mitigate traffic pollution at the end of 1990s, but the comprehensive effects, especially on ambient air quality and public health, have not yet been systematically evaluated. In this study, we analyze the effects of vehicle emission control measures on ambient air pollution and associated deaths attributable to long-term exposures of fine particulate matter (PM2.5) and O3 based on an integrated research framework that combines scenario analysis, air quality modeling, and population health risk assessment. We find that the total impact of these control measures was substantial. Vehicular emissions during 1998-2015 would have been 2-3 times as large as they actually were, had those measures not been implemented. The national population-weighted annual average concentrations of PM2.5 and O3 in 2015 would have been higher by 11.7 μg/m3 and 8.3 parts per billion, respectively, and the number of deaths attributable to 2015 air pollution would have been higher by 510 thousand (95% confidence interval: 360 thousand to 730 thousand) without these controls. Our analysis shows a concentration of mortality impacts in densely populated urban areas, motivating local policymakers to design stringent vehicle emission control policies. The results imply that vehicle emission control will require policy designs that are more multifaceted than traditional controls, primarily represented by the strict emission standards, with careful consideration of the challenges in coordinated mitigation of both PM2.5 and O3 in different regions, to sustain improvement in air quality and public health given continuing swift growth in China's vehicle population.

Optimization of a volatile organic compound control strategy in an oil industry center in Canada by evaluating ozone and secondary organic aerosol formation potential

Volatile organic compounds (VOCs) play a vital role in the formation of photochemical smog and haze in large urban environments. Previous source apportionment studies have focused on the contribution of different sources to VOC concentration with a view to pinpointing the major culprits for effective emission mitigation. However, different VOC sources may have different ozone (O3) and secondary organic aerosol (SOA) formation potentials. From a control perspective, it would be more rational to consider the role of individual VOC sources in secondary pollution; therefore, here, we propose a tiered source identification method that considers the formation potentials of O3 and SOA, which we applied in Calgary, Alberta, a site under the influence of multiple competing VOC sources. The pollution characteristics, secondary pollutant formation potential, and geographical origin of VOC sources were investigated over a five-year period. Seven major sources were identified using the positive matrix factorization (PMF) model, among which vehicle exhausts and solid fuel combustion were the dominant VOC sources responsible for O3 (60%) and SOA (63%) formation. Combustion of both liquid fuel (gasoline and diesel) and solid fuel (wood and coal) has exceeded the contribution of oil and gas production and become the top contributor to O3 and aerosol pollution in Calgary. This finding is consistent with the significant reduction (32.2–99.8%) in oil and gas production in Calgary over the period of 2013–2017. The source apportionment results show that the primary VOC source has shifted from conventional oil and gas extraction to a mixture of vehicle exhausts and oil and gas extraction, indicating the effectiveness of emission control measures taken in the energy sectors. Moreover, regionally transported VOCs from combustion sources in southeastern British Columbia have greatly increased the VOC level and secondary pollutant formation in Calgary. To effectively alleviate secondary pollution problems, the performance of joint pollution control measures has been suggested by the governments of both Alberta and British Columbia. These findings reveal that the tiered source identification strategy combining the traditional receptor model with socioeconomic factors, emission inventory, and source region analysis is a robust and promising tool for the interpretation of source apportionment results and optimization of secondary pollution control.

Study on emissions of volatile organic compounds from a typical coking chemical plant in China

Coking chemical industry associated with high energy consumption and high pollution emits significant amount of volatile organic compounds (VOCs) to atmosphere, but is often ignored. This article reports a new study on emissions of VOCs from a typical coking chemical plant. Results show that about 70 species of VOCs including alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons and oxygenates are detected, naphthalene and benzene could be used as the emission markers. Compared to coking stage, gas purifying stage is found to have 4 times more total concentrations of VOCs, in which condensing and blasting process is found to be the largest contributor with 77% ozone formation potential (OFP) contribution. Emission control measures currently used are insufficient and inefficient to reduce VOCs to meet regulatory emission standards. Further, by using a proposed integrated emission factor of 2.652 g/kg coke, the coking chemical industry in China was estimated to account for about 7.8–20% of total historical industrial VOCs emissions, and about 1241 Gg of VOCs were emitted in 2019. A large proportion is emitted from the northern China with a distinctive spatial distribution. Shanxi, Hebei, Shandong, and Shannxi provinces are the top four emitters. It is suggested that more stringent and efficient measures should be taken on the coking chemical industry, not just on the coking processes, but also on the gas purifying processes.

Estimations of Long-Term nss-SO42- and NO3- Wet Depositions over East Asia by Use of Ensemble Machine-Learning Method.

Wet deposition of non-sea-salt sulfate (nss-SO42-) and nitrate (NO3-), derived from anthropogenic emissions of SO2 and NOx, exerts adverse effects on ecosystems. In this work, an ensemble back-propagation neural network was proposed to estimate the long-term wet depositions of nss-SO42- (2005-2017) and NO3- (2001-2014) over East Asia in 10 km resolution. The R2 values for the 10-fold cross-validation of annual wet depositions of nss-SO42- and NO3- were 0.90 and 0.85, respectively. The hotspots of the wet deposition of these two acidic species span southwestern, central, and eastern China. The molar ratio of NO3- to nss-SO42- increased in 10 out of 12 analyzed East Asian countries from 2005 to 2014, which indicates that the acidity in rainwater shifts from the sulfur type to nitrogen type over most of the regions. The wet deposition on the four ecosystems (forest, grassland, cropland, and freshwater body) was also analyzed. Results showed that the nss-SO42- wet deposition on 25.5% of freshwater bodies in 2015 and NO3- wet deposition on 21.7% of grassland in 2014 exceeded the ecosystem empirical critical loads (25 kg/ha sulfate and 2 kg N/ha) in East Asia. Thus, more stringent and regionally collaborative sulfur and nitrogen emission-control measures are urgently needed to protect the ecosystem of East Asia.

Decadal Trends of Speciated Non‐methane Hydrocarbons in Taipei

AbstractSelected non‐methane hydrocarbons (NMHCs) obtained from long‐term operation of the Photochemical Assessment Monitoring Stations (PAMS) in Taipei allowed for the assessment of the effectiveness of emission control measures on ozone precursors from 2007 to 2016. Despite the very pronounced diurnal and seasonal cycles of all the 51 target compounds, almost all species showed various degrees of declining trends over the decade. When dividing the 51 compounds into five groups of alkanes, alkenes, ethyne, aromatics, and isoprene, the decadal trends are assessed as −0.7 ± 0.8, −0.3 ± 0.1, −0.02 ± 0.14, −1.9 ± 1.2, and − 0.09 ± 0.02 ppbC year−1, respectively. Meanwhile, as evidenced by multiple NMHC ratios as effective indicators of atmospheric photochemical conditions, a trend of gradual lessening in the degree of photochemistry over time was noticed. Air masses in Taipei are suggested to be increasingly more contributed by local emissions and less affected by mixing with transboundary or long‐range transported influences.

Wintertime nitrate formation pathways in the north China plain: Importance of N2O5 heterogeneous hydrolysis

Strict emission control measures have been implemented in the North China Plain (NCP) to improve air quality since 2013. However, heavy particulate matter (PM) pollution still frequently occurs in the region especially during wintertime, and the nitrate contribution to fine PM (PM2.5) has substantially increased in recent several years. Nitrate aerosols, which are formed via nitric acid (HNO3) to balance inorganic cations in the particle phase, have become a major fraction of PM2.5 during wintertime haze events in the NCP. HNO3 is mainly produced through homogeneous (NO2+OH, NO3+VOCs) and heterogeneous pathways (N2O5 heterogeneous hydrolysis) in the atmosphere, but the contribution of the two pathways to the nitrate formation remains elusive. In this study, the Weather Research and Forecasting model with Chemistry (WRF-Chem) was applied to simulate a heavy haze episode from 16 to December 31, 2016 in the North China Plain, and the source-oriented method (SOM) and brute force method (BFM) were both used to evaluate contributions of the heterogeneous pathway to the nitrate formation. The results demonstrated that the near-surface nitrate contributions of the heterogeneous pathway were about 30.8% based on the BFM, and 51.6% based on the SOM, indicating that the BFM might be subject to underestimating importance of the heterogeneous pathway to the nitrate formation. The SOM simulations further showed that the heterogeneous pathway dominated the nighttime HNO3 production in the planetary boundary layer, with an average contribution of 83.0%. Although N2O5 was photolytically liable during daytime, the heterogeneous N2O5 hydrolysis still contributed 10.1% of HNO3, which was caused by substantial attenuation of incident solar radiation by clouds and high PM2.5 mass loading. Our study highlighted the significantly important role of N2O5 heterogeneous hydrolysis in the nitrate formation during wintertime haze days.

Effect of emission control measures on ozone concentrations in Hangzhou during G20 meeting in 2016

The effect of emission control measures on ozone (O3) concentrations in Hangzhou during G20 (The Group of Twenty Finance Ministers and Central Bank Governors) meeting during 24 August to 6 September of 2016 was evaluated using the nested version of a global chemical transport model. During G20, observed concentrations of PM10, PM2.5, SO2, NO2, and CO were all below national air quality standards, whereas those of MDA8 O3 were above national standard (with an averaged value of 160.2 μg m−3) but had a decreasing trend. Model sensitivity studies show that, MDA8 O3 concentrations in Hangzhou during G20 were reduced by 11.3 μg m−3 (6.8%), 14.8 μg m−3 (8.9%), and 19.5 μg m−3 (11.7%) with emission control measures in the core area, Zhejiang province, and the Yangtze River Delta (YRD) region, respectively, indicating that control measures were the most effective when carried out jointly in YRD. Considering the ratios of NOx to VOCs during G20, Hangzhou and most areas of Zhejiang province were in transitional regime; reductions in either NOx or VOCs could reduce O3 concentrations. We also quantified how sensitive O3 concentrations respond to emission reductions in sectors of industry, power, residential and transportation in the whole of YRD during G20. The removal of emissions in industry and transportation sectors would lead to the largest reductions of 17.6 μg m−3 (10.5%) and 12.3 μg m−3 (7.4%) in MDA8 O3 concentrations in Hangzhou during G20, respectively. This study has important implications for the control of high O3 levels in eastern China.

Fine Dust and Sustainable Supply Chain Management in Port Operations: Focus on the Major Cargo Handled at the Dry Bulk Port

Local residents living adjacent to ports are directly affected by the fine dust generated from the port operations. There is a need to prepare detailed measures according to cargo type given the high correlation between the types of dust-producing cargo primarily managed at ports and local industries. This study attempts to establish the attributes of the cargo handled at ports and the relationship between supply chains built for local key industries and the air quality of the local community. It aims to ascertain which cargo needs managing preemptively at the local level, based on the major cargo types handled in a port. A correlation analysis and Granger causality test were performed to investigate the causality between the factor of cargo and fine dust concentrations. The results in this study indicate the necessity for intensive management of scrap metal cargo among the major cargo handled at the target port, which confirms the large effect of management on fine dust reduction, as well as on reduction efficiency. The results suggest requirements to expand the regulations on the emissions of supply chains by cargo type, not by industry type. Additionally, it is required to minimize the blind spots of management and form an eco-friendly supply chain by introducing green technology. The preparation of emission control measures is also necessary. The findings provide useful insights for the sustainable operations of the local supply chain around the target port and will help the strategic agenda for future improvement.

Characterizing the ratio of nitrate to sulfate in ambient fine particles of urban Beijing during 2018–2019

Abstract A variety of legislative actions for air quality improvement have been conducted in China since 2013, and the emission control measures have achieved remarkable reduction in severe haze frequency. The composition of the fine particles may change along with the improved air quality, and thus may induce distinct environmental and climate effects in future. In this study, a very recent long-term dataset (2018–2019) of non-refractory chemical composition measured by a quadrupole aerosol chemical speciation monitor (Q-ACSM) observed in urban Beijing is applied to investigate the changes in ratio of nitrate (NO3−) to sulfate (SO42−) in PM2.5 (particulate matter with diameters of less than 2.5 μm). We show that the ratio of NO3− to SO42− varies seasonally, with a maximum in winter (1.6 ± 1.2) and a minimum in summer (0.7 ± 1.0). Compared with results from earlier studies showing a continuous increase in the ratio of NO3− to SO42− since 1999, a decline in the ratio is found during the period of 2018–2019. This is partially associated with an attenuated nitrate formation likely due to reduced nitrogen oxides emissions since 2016 in China. Our results suggest that the strict reduction control measures in place serve only to improve SO42− pollution in winter but not in summer when high SO42− levels are still observed. SO42− and NO3− concentrations during study periods together comprise 37–53% of PM2.5, presenting significant role in dominating the levels of PM2.5. In addition, we show that the ratio of NO3−/SO42− in warm seasons generally increases with increasing relative humidity (RH) due to enhanced NO3− hydrolysis formation, but with a maximum value of only ~1.0 that is pulled down by the high levels of sulfate in summer, while the dependence of the ratios on RH is more pronounced in cold seasons when multiple factors (regional transportation, planetary boundary layer, PBL and sources of sulfate, etc.) can impact nitrate levels. We finally characterize two typical processes that lead to the rapid accumulation of nitrate in the atmosphere over urban Beijing: the regional transportation and PBL variations, which is found driving heavy haze in cold seasons, and the hydrolysis formation and partitioning of NO3− that tends to impact the diurnal patterns of nitrate in warm seasons.

Worsening urban ozone pollution in China from 2013 to 2017 – Part 1: The complex and varying roles of meteorology

Abstract. China has suffered from increasing levels of ozone pollution in urban areas despite the implementation of various stringent emission reduction measures since 2013. In this study, we conducted numerical experiments with an up-to-date regional chemical transport model to assess the contribution of the changes in meteorological conditions and anthropogenic emissions to the summer ozone level from 2013 to 2017 in various regions of China. The model can faithfully reproduce the observed meteorological parameters and air pollutant concentrations and capture the increasing trend in the surface maximum daily 8 h average (MDA8) ozone (O3) from 2013 to 2017. The emission-control measures implemented by the government induced a decrease in MDA8 O3 levels in rural areas but an increase in urban areas. The meteorological influence on the ozone trend varied by region and by year and could be comparable to or even more significant than the impact of changes in anthropogenic emissions. Meteorological conditions can modulate the ozone concentration via direct (e.g., increasing reaction rates at higher temperatures) and indirect (e.g., increasing biogenic emissions at higher temperatures) effects. As an essential source of volatile organic compounds that contributes to ozone formation, the variation in biogenic emissions during summer varied across regions and was mainly affected by temperature. China's midlatitude areas (25 to 40∘ N) experienced a significant decrease in MDA8 O3 due to a decline in biogenic emissions, especially for the Yangtze River Delta and Sichuan Basin regions in 2014 and 2015. In contrast, in northern (north of 40∘ N) and southern (south of 25∘ N) China, higher temperatures after 2013 led to an increase in MDA8 O3 via an increase in biogenic emissions. We also assessed the individual effects of changes in temperature, specific humidity, wind field, planetary boundary layer height, clouds, and precipitation on ozone levels from 2013 to 2017. The results show that the wind field change made a significant contribution to the increase in surface ozone over many parts of China. The long-range transport of ozone and its precursors from outside the modeling domain also contributed to the increase in MDA8 O3 in China, especially on the Qinghai–Tibetan Plateau (an increase of 1 to 4 ppbv). Our study represents the most comprehensive and up-to-date analysis of the impact of changes in meteorology on ozone across China and highlights the importance of considering meteorological variations when assessing the effectiveness of emission control on changes in the ozone levels in recent years.

Carbon Emission Efficiency in the Construction Industry and Its Carbon Emission Control Measures: A Case Study of Henan Province, China

Carbon Emission Efficiency in the Construction Industry and Its Carbon Emission Control Measures: A Case Study of Henan Province, China

Spatial–temporal variations and process analysis of O<sub>3</sub> pollution in Hangzhou during the G20 summit

Abstract. Serious urban ozone (O3) pollution was observed during the campaign of 2016 G20 summit in Hangzhou, China, while other pollutants had been significantly reduced by the short-term emission control measures. To understand the underlying mechanism, the Weather Research Forecast with Chemistry (WRF-Chem) model is used to investigate the spatial and temporal O3 variations in Hangzhou from 24 August to 6 September 2016. The model is first successfully evaluated and validated for local and regional meteorological and chemical parameters by using the ground and upper-air level observed data. High ozone concentrations, temporally during most of the daytime emission control period and spatially from the surface to the top of the planetary boundary layer, are captured in Hangzhou and even the whole Yangtze River Delta region. Various atmospheric processes are further analyzed to determine the influential factors of local ozone formation through the integrated process rate method. Interesting horizontal and vertical advection circulations of O3 are observed during several short periods, and the effects of these processes are nearly canceled out. As a result, ozone pollution is mainly attributed to the local photochemical reactions that are not obviously influenced by the emission reduction measures. The ratio of reduction of Volatile Organic Compounds (VOCs) to that of NOx is a critical parameter that needs to be carefully considered for future alleviation of ozone formation. In addition, the vertical diffusion from the upper-air background O3 also plays an important role in shaping the surface ozone concentration. These results provide insight into urban O3 formation in Hangzhou and support the Model Intercomparison Study Asia Phase III (MICS-Asia Phase III).

Global Sulfur Dioxide Emissions and the Driving Forces.

The presence of sulfur dioxide (SO2) in the air is a global concern because of its severe environmental and public health impacts. Recent evidence from satellite observations shows rapid changes in the spatial distribution of global SO2 emissions, but such features are generally missing in global emission inventories that use a bottom-up method due to the lack of up-to-date information, especially in developing countries. Here, we rely on the latest data available on emission activities, control measures, and emission factors to estimate global SO2 emissions for the period 1960-2014 on a 0.1° × 0.1° spatial resolution. We design two counterfactual scenarios to isolate the contributions of emission activity growth and control measure deployment on historical SO2 emission changes. We find that activity growth has been the major factor driving global SO2 emission changes overall, but control measure deployment is playing an increasingly important role. With effective control measures deployed in developed countries, the predominant emission contributor has shifted from developed countries in the early 1960s (61%) to developing countries at present (83%). Developing countries show divergency in mitigation strategies and thus in SO2 emission trends. Stringent controls in China are driving the recent decline in global emissions. A further reduction in SO2 emissions would come from a large number of developing nations that currently lack effective SO2 emission controls.

Impact of emission reduction on aerosol-radiation interaction during heavy pollution periods over Beijing-Tianjin-Hebei region in China

In December 2015, the Beijing-Tianjin-Hebei (BTH) region experienced several episodes of heavy air pollution. The government immediately issued emergency control measures to reduce the pollution, which provided a good opportunity to explore the impact of emission reduction on aerosol-radiation interaction. In this study, four tests were conducted, including the base1 simulation with emission reduction and aerosol-radiation interaction on, the base2 simulation with emission reduction and aerosol-radiation interaction off, the scenario1 simulation without emission reduction and aerosol-radiation interaction on and the scenario2 simulation without emission reduction and aerosol-radiation interaction off. We find that the aerosol-radiation interaction decreased the downward shortwave radiation and the temperature at 2 m, reduced the planetary boundary layer height (PBLH) in the region, and increased the relative humidity at 2 m, which is favorable for pollution accumulation. Our results revealed that the interaction effect due to emission reductions increased downward shortwave radiation by an average of 0–5 W/m2, leading to increase in surface temperature of 0–0.05°C, increase in the daytime mean PBL high of 0–8 m, and decrease in daytime mean relative humidity at 2 m of 0.5%. We found that if there were aerosol-radiation interaction, it would enhance the effectiveness of emission control measures on air pollution control. The enhance of PM2.5 (particulate matter less than 2.5 µm), PM10 (particulate matter less than 10 µm), and NO2 (nitrogen dioxide) emission reduction effects reached 7.62%, 6.90%, 11.62%, respectively, over this region.