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Severe outdoor haze pollution has brought about associated public health impacts for China in recent years. Haze pollution therefore has become one of the most serious environmental problems in China. To alleviate this, the government issued its National Air Pollution Control NACAP (NAPCAP) in 2013 containing pollution reduction targets for 2017 and beyond. However, there are doubts whether these targets can be achieved. This paper examines this issue by modeling the statistical relationship between PM 2.5 concentration and air pollutant emissions (SO 2 , NO x , etc.), together with wind and neighboring transfer impacts at the city level, to identify ways of calculating intended maximum emission levels in the Beijing-Tianjin-Hebei area. The results indicate that local air pollutant emissions, lagged PM 2.5 concentrations, wind speed, and PM 2.5 concentrations in adjacent areas have a significant impact on PM 2.5 concentrations in the Beijing-Tianjin-Hebei area. The 2017 haze concentration control targets could not be achieved through the current NAPCAP plan, with PM 2.5 concentration levels in many locations being predicted as between two and three times those targeted. However, the 2017 concentration target can be fulfilled given the pollutant reduction rates of NAPCAP plus Enhanced Measures of Air Pollution Control for Beijing-Tianjin-Hebei region (EMAPC) under the same wind conditions as 2016. There are large deviations between the simulation and monitor values of PM 2.5 concentration when it is less windy, and the simulation value of most cities are generally lower than the monitor values. The unsuccessful implementation of pollutant reduction measures and inaccuracy of the monitor data are two possible reasons to explain the relatively large deviations involved. Finally, some preliminary institutional causes of haze pollution and solutions for its control in the Beijing-Tianjin-Hebei area are discussed. [ABSTRACT FROM AUTHOR]

Along with China's modern industrialization, challenges on smog crisis are raising dramatically in the past decade. The sources of municipal smog are multiple and complex, one of which is construction dust emission due to the rapid urbanization. In literature, there are studies focusing on the end-pipe treatment of construction dust; however, very little research has been conducted from the perspective of dust mitigation in developing countries. To fill in this research gap, this paper investigates the current situation of construction dust prevention and control in China, with the aim of providing insights for mitigating dust pollution caused by the construction industry. Through a combination of the content analysis, on-site observation, questionnaire survey and interviews with experienced professionals, a total of 11 related regulations are thoroughly reviewed, and the main sources of construction dust production are identified. A case study is further presented to demonstrate the prevailing dust control measures on site. Recommendations are proposed in order to increase the awareness of related stakeholders, including formulation of targeted regulations, establishment of an appropriate charging scheme, development of a feasible monitoring system, and enhancement of training and dissemination. [ABSTRACT FROM AUTHOR]

Abstract: Air pollution problems caused from the development of infrastructures are getting serious, in which air flow is reduced and heat is trapped among high-rise buildings. In order to mitigate these problems, various methods have been developed in previous studies. Extensive green roof has been identified as one of the most important means to mitigate these problems and implement sustainable development principles in the building features. Governments world-wide have been introducing various policies and regulations for promoting extensive green roof particularly for building projects. However, the existing buildings in many large cities such as Hong Kong display few extensive green roof features. Hong Kong is one of the most densely populated cities with many high-rise buildings. This paper examines the major barriers encountered in promoting extensive green roof systems for the existing buildings in Hong Kong. Case study approach is adopted to investigate how and why the barriers can hinder the implementation of extensive green roof features. Research results show that lack of promotion and incentives from governments and the increase maintenance cost are identified as the top barriers to the implementation. The paper concludes by providing further suggestions and actions that can help mitigate these existing barriers. [Copyright &y& Elsevier]

Three years of measurement of PM2.5 with 5-min time resolution was conducted from 2005 to 2007 in urban and rural environments in Beijing to study the seasonal and diurnal variations in PM2.5 concentration. Pronounced seasonal variation was observed in the urban area, with the highest concentrations typically observed in the winter and the lowest concentrations generally found in the summer. In the rural area, the maximum in PM2.5 concentration usually appeared during the spring, followed by a second maximum in the summer, while the minimum generally occurred in the winter. Significant diurnal variations in PM2.5 concentration were observed in both urban and rural areas. In the urban area, the PM2.5 concentration displays a bimodal pattern, with peaks between 7:00 and 8:00 a.m. and between 7:00 and 11:00 p.m. The minimum generally appears around noon. The morning peak is attributed to enhanced anthropogenic activity during rush hours. The decreases of boundary layer height and wind speed in the afternoon companying with increased source activity during the afternoon rush hour result in the highest PM2.5 concentration during evening hours. In the rural area, the PM2.5 concentration shows a unimodal pattern with a significant peak between 5:00 and 11:00 p.m. The seasonal and diurnal variations in PM2.5 concentration in the urban area are mostly dominated by the seasonal and diurnal variability of boundary layer and source emissions. The year-to-year variability of rainfall also has an important influence on the seasonal variation of PM2.5 in the urban area. The seasonal and diurnal wind patterns are more important factors for PM2.5 variation in the rural area. Southerly winds carry pollutants emitted in southern urban areas northward and significantly enhance the PM2.5 concentration level in the rural area. [Copyright &y& Elsevier]

Numerous studies have examined the correlation between economic growth and air pollution, but few focuses on the nexus between environmental regulation and <2.5 μm (PM 2.5) fine particle matter. Using Spatial Durbin Model (SDM) and Spatial Two-stage Least Squares (2SLS) methods to analyze 277 Chinese cities over the period 2002–2010, this paper finds inverted U-shaped relationships between PM 2.5 concentration and formal/informal environmental regulations for the whole and eastern and western regions. By removing the depression year of 2008, regulation effect on pollution strengthened, indicating that the main task for local governments in crisis is to avoid GDP decline rather than official promotion. Further, green technological innovation and industrial structure optimization induced by environmental regulation is shown to be beneficial for haze pollution mitigation. Some policy recommendations are proposed in conclusion. • The Spatial Models are used to examine the effect of regulation on the PM 2.5 of 277 Chinese cities during 2002–2010. • An inverted U-shaped relationship is found for the nexus. • Eastern and western China generally has an inverted U-shaped relationship. • Technical innovation and industrial structure are confirmed to be important mechanisms. [ABSTRACT FROM AUTHOR]

Abstract North China Plain (NCP) is one of heavily polluted regions that is characterized by a mixture of a myriad of anthropogenic and natural aerosols. A substantial spatial and temporal variations of aerosols and their compositions there poses a good testbed for the validation of model simulations. Aerosol optical depth (AOD) and PM 2.5 (particulate matter with aerodynamic diameter < 2.5 μm) concentration products from the Modern Era Retrospective-Analysis for Research and Applications, version 2 (MERRA-2) are evaluated using available independent ground-based in situ and remote sensing products in the NCP. The comparison of MERRA-2 aerosol species to the observations is also performed. Although several satellite and ground-based AOD products are assimilated into the MERRA-2, MERRA-2 AOD is systematically smaller than independent sunphotometer measurements. The biases range from 0.09 (13%) in the summer to 0.17 (33%) in the spring and show little spatial dependence. Daytime AOD variations are captured by the MERRA-2, although MERRA-2 has relatively lower AOD. MERRA-2 produces lower PM 2.5 concentration relative to surface measurements in all seasons except in summer. The largest bias is found in the winter (44 μgm−3). On the contrary, summer MERRA-2 PM 2.5 is close to surface-measured PM 2.5 (with bias of 0.4 μgm−3). MERRA-2 was unable to reproduce diurnal PM 2.5 variation. Evaluation of MERRA-2 aerosol species in the winter of 2014 suggests that MERRA-2 could not keep track of dramatic day-to-day variation of aerosols and their species. Potential causes for this deficiency may include a lack of nitrate aerosols (accounting for 20% of PM 2.5 concentrations during heavily polluted days). This fault cannot be remedied by assimilation of satellite AODs because they are often missing. Highlights • MERRA-2 underestimates AOD but produces consistent daytime variation as sunphotometer data. • MERRA-2 produces extremely lower PM 2.5 concentration relative to surface measurements in the winter. • Assimilation of satellite AOD cannot remedy MERRA-2 PM 2.5 error associated with lack of nitrate simulation. • Missing satellite AOD product during haze episodes needs further consideration. [ABSTRACT FROM AUTHOR]

It's urgent to clarify the quantitative relationship between declining fine−particle (PM 2.5) concentrations and increasing ozone (O 3) levels as ozone pollution is increasingly severe in China. Here, we analyze the ground–based data of aerosol optical properties, particulates, and gaseous pollutants collected in a simultaneous observation in Kunming, locate in the Yunnan–Guizhou Plateau, from June 2014 to May 2017. The data exhibit slightly rising levels of PM 2.5 , O 3 , and carbon monoxid (CO), declining AOD (aerosol optical depth) but increasing AE (Angstrom exponent). Both the seasonal PM 2.5 and CO concentrations were low in the wet season and high in the dry season. The seasonal ozone levels and AE almost increased monotonically while the seasonal AOD decreased wavelike. Overall, the maximum daily 8 h average (MDA8) O 3 concentrations positively related to PM 2.5 concentrations with temperature>22 °C, RH<45%, and AOD<1.0 in the wet season. Generally, MDA8 O 3 concentrations didn't fluctuate with PM 2.5 concentrations in the dry season. High SSA (single scattering albedo) corresponded to high MDA8 O 3 concentrations and low SSA corresponded to low MDA8 O 3 concentrations in the wet season. However, lower SSA values in the dry season were observable. Most high MDA8 O 3 concentrations (>100 μg m−3) in the wet season occurred with AE at 1.0–1.5. High MDA8 O 3 concentrations (>100 μg m−3) in dry season appeared with an AE range of ~0.75–1.75. Low MDA8 O 3 concentrations occurred with AOD>2.0 and RH>75%, despite T>20 °C. The biomass−burning/urban aerosols were dominant (71.11% in the wet season and 74.40% in the dry season). The PSCF (Potential Source Contribution Function) results revealed the air pollutants from inside and outside China will have great impacts on the pollutant levels in Kunming besides the local emissions. Particularly, the severe pollution in India may aggravate Kunming's air pollution. • High SSA corresponded to high MDA8 O 3 concentrations and positive MDA8 O 3 − PM 2.5 relations were observable with SSA>0.95. • Most high MDA8 O 3 concentrations (>100 μg m−3) in the wet season occurred with AE at 1.0–1.5. • Biomass−burning/urban aerosols were dominant, accounting for over 70% of the whole aerosol types. • The air pollutants from outside China may have an important impact on the pollutant levels in Kunming. [ABSTRACT FROM AUTHOR]

Both PM 2.5 and visibility are important physical parameters to measure the air pollution condition. This paper first provided a new normalization approach for the relationship between PM 2.5 and visibility in heavy pollutant region, which realized a mathematical calculation for two different physical parameters based on non-dimensional data process (also called Min-Max normalization). The normalization relationship showed a power function (y = axb) with high correlation coefficients. The inflection points of the maximum power function curvature composed the theoretical threshold range of PM 2.5 for improving or deteriorating the visibility. In the case city of north China, the threshold range of PM 2.5 was 112–121 μg·m−3 corresponding to the visibility range 4.5–5.9 km. Within the threshold range, the mean concentration of main pollutant components was 106 μg·m−3. The mean extinction coefficient, b ext of 743.5 Mm−1, was mainly contributed by organic matter (34%), ammonium nitrate (19%), ammonium sulfate (18%) and elemental carbon (13%). When PM 2.5 was below the range, the visibility increased significantly with the slow decrease of PM 2.5. When PM 2.5 exceeded the range, the visibility reduced seriously due to the saturated extinction contribution of the main pollutants. The new normalization approach theoretically revealed the significance of threshold and how to improve visibility by controlling PM 2.5 at different pollution stages. Unlabelled Image • A new normalization approach was first applied to establish the mathematical relationship of PM 2.5 and visibility. • The normalization mathematical relationship was a power function with high correlation coefficients. • The maximum curvature of the function composed the theoretical threshold of PM 2.5 to improve or deteriorate visibility. • The extinction coefficients of aerosol components were quite different at different pollution stages. • The threshold range has guiding significance how to control PM 2.5 for the blue sky in heavy polluted cities. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) play key roles in the formation of particulate matter (PM) and oxidants and hence enhance the summertime air pollution. With data analysis from various field observations (urban station: Haidian, HD; suburb station: Changping, CP; regional background station: Shangdianzi, SDZ) in June 2011, we found that the mean O 3 concentrations throughout the observation period can be arranged in order: SDZ＞CP＞HD. The mean PM concentrations can be arranged in order: HD＞CP＞SDZ. The mean concentration of total VOCs at HD was close to that at CP, but much higher than that at SDZ. Oxygenated volatile organic compounds (OVOCs) made the largest portion of VOCs (~40%) at the three stations, followed by alkanes and alkenes. Good positive correlations between the concentrations of PM and O x (=O 3 ＋NO 2) at high air temperature (≥30 °C at HD and CP; ≥28 °C at SDZ) and low RH (≤60%) were found in the daytime (07:00–18:00 LT). However, the PM concentrations were partly negatively correlated with O x at lower temperatures (≤26 °C at HD and CP; ≤22 °C at SDZ) and higher RH (≥80%). The PM concentrations were found either positively (HD and CP) or negatively (SDZ) correlated with aromatics at high temperature and low RH. The aging degree of air masses at the three stations can be arranged in order: SDZ＞CP＞HD. This can qualitatively explain the different PM−aromatics correlations. Our data suggested the other groups of VOCs may promote the increase of PM concentrations unless the PM levels become higher than 140 μg m−3 under humid conditions. This study confirms the importance of VOCs in the formation of summertime PM and oxidants over Beijing. Image 1 • Parallel photochemical formations of PM and O 3 caused positive PM-O x correlations. • Positive PM-aromatics correlations were found at HD and CP, but negative at SDZ. • OVOCs made the largest portion of VOCs (~40%) in the high ozone episode. • VOCs may promote the increase of summertime PM concentrations under humid conditions. [ABSTRACT FROM AUTHOR]

Surface particulate matter with an aerodynamic diameter of <2.5 μm (PM2.5) and column-integrated aerosol optical depth (AOD) exhibits substantial diurnal, daily, and yearly variabilities that are regionally dependent. The diversity of these temporal variabilities in urban and rural areas may imply the inherent mechanisms. A novel time-series analysis tool developed by Facebook, Prophet, is used to investigate the holiday, seasonal, and inter-annual patterns of PM2.5 and AOD at a rural station (RU) and an urban station (UR) in Beijing. PM2.5 shows a coherent decreasing tendency at both stations during 2014–2018, consistent with the implementation of the air pollution action plan at the end of 2013. RU is characterized by similar seasonal variations of AOD and PM2.5, with the lowest values in winter and the highest in summer, which is opposite that at UR with maximum AOD, but minimum PM2.5 in summer and minimum AOD, but maximum PM2.5 in winter. During the National Day holiday (1–7 October), both AOD and PM2.5 holiday components regularly shift from negative to positive departures, and the turning point generally occurs on October 4. AODs at both stations steadily increase throughout the daytime, which is most striking in winter. A morning rush hour peak of PM2.5 (7:00–9:00 local standard time (LST)) and a second peak at night (23:00 LST) are observed at UR. PM2.5 at RU often reaches minima (maxima) at around 12:00 LST (19:00 LST), about four hours later (earlier) than UR. The ratio of PM2.5 to AOD (η) shows a decreasing tendency at both stations in the last four years, indicating a profound impact of the air quality control program. η at RU always begins to increase about 1–2 h earlier than that at UR during the daytime. Large spatial and temporal variations of η suggest that caution should be observed in the estimation of PM2.5 from AOD. [ABSTRACT FROM AUTHOR]

Visibility can be used as a highly relevant visual indicator of the air pollution level. Published data on the correlations between visibility and health outcomes are very limited in China, and the health effects of slight haze on the human body have not been clarified. A semi-parametric generalized additive model (GAM) was used to assess the acute health effects of visibility on respiratory–cardiovascular mortality in Beijing, China. The correlation between visibility and PM 2.5 as well as the contributions of PM 2.5 to the health effects of visibility were analysed. Stratification model was employed to investigate the health effects of slight haze. The mortality risk of impaired visibility on the current exposure day peaked and was statistically significant for all the mortality outcomes. Every 1 km decrease in visibility corresponded to a 0.78% (95% CI: 0.62–0.95%) increase in total respiratory mortality and 0.54% (95% CI: 0.45–0.61%) increase in total cardiovascular mortality. Older people (age ≥65) were at a higher risk than the younger age group under impaired visibility. PM 2.5 had a negative logarithmic relationship relative to visibility. After adjustment for PM 2.5 , the risk estimates for both respiratory and cardiovascular mortality reduced. Short-term exposure to low visibility was significantly associated with increased respiratory and cardiovascular mortality in Beijing. The health risk of impaired visibility was particularly high, even in slight haze. The hazardous effects of visibility can be partially attributed to the effects of PM 2.5. These results can provide useful reference for relevant agencies to determine whether an adjustment to the haze warning level is warranted. Our findings indicate that visibility can be used as an alternative indicator for air quality assessments if air pollution data are insufficient or not available, particularly in developing countries. Image 1 • Studies on association between visibility and health outcomes are rare in China. • Exposure to impaired visibility is significantly related to increased mortality. • Health effects of impaired visibility can be partially explained by PM 2.5. • Health risk of impaired visibility is intense, even in slight haze. [ABSTRACT FROM AUTHOR]

Visibility has been continuously and stably observed for more than half a century, while particulate matter with an aerodynamic diameter ≤ 2.5 μm (PM 2.5) was not introduced to the national monitoring system in China until 2013. It is a scientific issue as to whether visibility can be used as an alternative to assess the health risks of air pollution in periods and areas without pollutant monitoring data. A generalized additive model (GAM) was adopted to estimate the impacts of seasonal changes in visibility on mortality in Beijing, China. Moreover, we estimated the contributions of particulate matter in the health effects of visibility by adjusting for dry extinction coefficient (β dryext) and PM 2.5 in the model, respectively. We found that the acute health impacts of visibility varied by season, with the highest risks in winter. For respiratory mortality, the effect estimates per 1 km decrease in visibility were 0.40% (95% CI: 0.17–0.62%) in spring, 0.10% (95% CI: −0.14–0.34%) in summer, 0.27% (95% CI: 0.09–0.45%) in autumn, and 0.62% (95% CI: 0.38–0.85%) in winter. For cardiovascular mortality, the effect estimates per 1 km decrease in visibility were 0.20% (95% CI: 0.08–0.31%) in spring, 0.16% (95% CI: 0.04–0.27%) in summer, 0.25% (95% CI: 0.13–0.37%) in autumn, and 0.24% (95% CI: 0.13–0.35%) in winter. The seasonal pattern of health impacts related to visibility reflected the seasonal variations in the characteristics of air pollution emission sources and meteorological conditions that are unfavorable for pollutant dispersion. Particulate matter, particularly PM 2.5 , made significant contributions to the health impacts of visibility. The results indicated that controlling pollutant emissions in winter would be of significant importance to improve air quality and mitigate the health hazard of air pollution in Beijing. Our study also provides further evidence on the feasibility of using visibility to assess the health impacts of particulate matter pollution. Unlabelled Image • Visibility is considered as a significant indicator of the air pollution level. • Link between seasonal variations in visibility and mortality is poorly studied. • Health risks of visibility varied by season in Beijing, with highest risk in winter. • Particulate matter plays a significant role in the health impacts of visibility. [ABSTRACT FROM AUTHOR]

Previous studies of the residents' willingness to pay (WTP) for air quality improvement are likely suffering various endogeneity biases. Exploiting the unique opportunity of a recent quasi-experiment operation of the world's first SFT (Smog Free Tower) in China's northwestern city Xi'an, this paper reliably calibrates local residents' WTP for less exposure to haze by analyzing the price responses of housings in the neighborhoods of SFT. The hedonic regression is applied in the DID (difference-in-difference) setting, with further assistances of the PSM (propensity score matching) method, quantile regression and placebo test. The regression results consistently suggest that housing price responded positively to the installment of the SFT, and the impact estimates are closely centered around 4%. The study also indicates high-priced housings response much more to the operation of the SFT than cheap-priced housings, suggesting uneven distribution of welfare gains of air quality improvement. A cost-benefit analysis of the SFT project indicates that the economic benefits of this project far outweigh the costs involved. The paper concludes with discussions of policy implications of this paper for environment governance. • Exploiting the unique opportunity of the world's first Smog Free Tower in Xi'an, this paper calibrates local residents' willing to pay to less exposure to haze. • The hedonic regression is applied in the DID setting, with further assistance of the PSM method, quantile regressions and placebo tests. • The regression results suggest that housing price responded positively to the installment of the SFT, and the impact estimates are around 4%. • High-priced housings response more to SFT than cheap-priced housings, suggesting uneven distribution of welfare gains of air quality improvement. • A cost-benefit analysis of the SFT indicates that the economic benefits of this project far outweigh the costs involved. [ABSTRACT FROM AUTHOR]

Spatiotemporal patterns of global air pollution are of great significance to environmental management and public health. Studies have revealed the changes in the concentration of dust and sea-salt removed fine particulate matter (PM 2.5) pollution (DSRPP). However, the spatial characteristics of DSRPP on multiple scales remain unclear. Therefore, we combined the latest global estimates of the PM 2.5 dataset and landscape metrics to investigate the spatiotemporal patterns of DSRPP across global and national scales from 2000 to 2016. We found that the area of DSRPP increased from 1,146,800 km2 to 3,929,800 km2 between 2000 and 2016, a factor of 2.43. The DSRPP became more structurally fragmented and geometrically complex, with the patch density and the landscape shape index of DSRPP increasing by 133.3% and 24.5%, respectively. More than 90% of the DSRPP were concentrated in the middle income countries, especially in India and China. Specifically, the DSRPP in China exhibited a sprawling process before 2007 but a dissipating process after 2007 under the great efforts of the Chinese government in mitigating air pollution, while DSRPP in India remained an aggregation trend. The potential threat to public health posed by the DSRPP increased over time. Populations living in the areas with the DSRPP increased by 141.2% from 2000 to 2016 due to the deterioration of air quality and demographic change. Thus, we suggest that effective actions should be taken to control the main sources of anthropogenic emissions and mitigate the negative effects of DSRPP on public health in the future, especially in the middle income countries such as China and India. Image 1 • The area of global DSRPP increased by a factor of 2.43 from 2000 to 2016. • The global DSRPP became more spatially fragmented and complex from 2000 to 2016. • China's DSRPP sprawled before 2007 but dissipated thereafter through emission control. • The threat of global DSRPP to public health increased over time. [ABSTRACT FROM AUTHOR]