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High concentrations of particulate matter (PM 2.5 ) and frequent air pollution episodes in Beijing have attracted widespread attention. This paper utilizes data from the new air pollution network in China to examine the current spatial and temporal variability of PM 2.5 at 12 monitoring sites in Beijing over a recent 2-year period (April 2013 to March 2015). The long term (2-year) average concentration was 83 μg m −3 , well above Chinese and international standards. Across the region, annual average concentrations varied by 20 μg m −3 (25% of the average level), with lower levels in suburban areas compared to periurban and urban areas, which had similar concentrations. The spatial variation in PM 2.5 concentrations was associated with several land use and economic variables, including the fraction of vegetated land and building construction activity, which together explained 71% of the spatial variation. Daily air quality was characterized as “polluted” (above 75 μg m −3 ) on 36–47% of days, depending on site. There were 77 pollution episodes during the study period (defined as two or more consecutive days with Beijing-wide 24-hour average concentrations over 75 μg m −3 ), and 2 to 5 episodes occurred each month, including summer months. The longest episode lasted 9 days and daily concentrations exceeded 450 μg m −3 . Daily PM 2.5 levels were autocorrelated (r lag1 = 0.516) and associated with many meteorological variables, including barometric pressure, relative humidity, hours of sunshine, surface and ambient temperature, precipitation and scavenging coefficient, and wind direction. Parsimonious models with meteorological and autoregressive terms explained over 60% of the variation in daily PM 2.5 levels. The first autoregressive term and hours of sunshine were the most important variables in these models, however, the latter variable is PM 2.5 -dependent and thus not an explanatory variable. The present study can serve as a baseline to compare the improved air quality in Beijing expected in future years. [ABSTRACT FROM AUTHOR]

Abstract: As a pioneer in controlling vehicle emissions within China, Beijing released the Clean Air Action Plan 2013–2017 document in August 2013 to improve its urban air quality. It has put forward this plan containing the most stringent emission control policies and strategies to be adopted for on-road vehicles of Beijing. This paper estimates the historic and future trends and uncertainties in vehicle emissions of Beijing from 1998 to 2020 by applying a new emission factor model for the Beijing vehicle fleet (EMBEV). Our updated results show that total emissions of CO, THC, NO x and PM2.5 from the Beijing vehicle fleet are 507 (395–819) kt, 59.1 (41.2–90.5) kt, 74.7 (54.9–103.9) kt and 2.69 (1.91–4.17) kt, respectively, at a 95% confidence level. This represents significant reductions of 58%, 59%, 31% and 62%, respectively, relative to the total vehicle emissions in 1998. The past trends clearly posed a challenge to NOx emission mitigation for the Beijing vehicle fleet, especially in light of those increasing NO x emissions from heavy-duty diesel vehicles (HDDVs) which have partly offset the reduction benefit from light-duty gasoline vehicles (LDGVs). Because of recently announced vehicle emission controls to be adopted in Beijing, including tighter emissions standards, limitations on vehicle growth by more stringent license control, promotion of alternative fuel technologies (e.g., natural gas) and the scrappage of older vehicles, estimated vehicle emissions in Beijing will continue to be mitigated by 74% of CO, 68% of THC, 56% of NO x and 72% of PM2.5 in 2020 compared to 2010 levels. Considering that many of the megacities in China are facing tremendous pressures to mitigate emissions from on-road vehicles, our assessment will provide a timely case study of significance for policy-makers in China. [Copyright &y& Elsevier]

Abstract: Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and almucantar retrievals (single scattering albedo (SSA) and aerosol size distribution) from 2005–2009 in Beijing and Kanpur are used to analyze differences and similarities in aerosol optical properties over these two regions. The examination of monthly mean AOD (440 nm) shows that maximum and minimum values occurred in summer and winter, respectively, for Beijing, while the range in AOD in Kanpur was lower. Precipitation in both Beijing and Kanpur peaked in summer; however, the columnar water vapor (CWV) exhibited a high correlation with AOD in Beijing (R 2 = 0.79) but had a weak relationship with AOD in Kanpur (R 2 = 0.13). The Angstrom exponent (α, 440–870 nm) generally increased linearly as the fine mode fraction (FMF) of AOD (500 nm) increased for FMF < 90% in both regions, with a high correlation of R 2 > 0.96. However a clear decrease in α for FMF > 90% found in Beijing is not shown distinctly in Kanpur, and is mainly due to the higher aerosol loading in this FMF bin at Beijing (AOD at 440 nm > 2.2) which results in a stronger coagulation of fine mode particles. Bimodal seasonally-averaged size distributions reveals similar aerosol mixtures composed of fine pollution particles and coarse dust particles in both regions. The analysis of spectral SSA as a function of α is emphasized in this paper. The average SSA at 440 nm in both regions shows a similar low dynamic range of ∼0.03 for α < 1.4. The obvious increase in SSA at 440 nm for α > 1.4 in both regions can be attributed to a higher FMF leading to fine mode coagulation. However, the distinctly smaller increase in Kanpur suggests that fine mode aerosols at Beijing are less absorbing than those at Kanpur. The visibly lower SSA at 675 nm at Kanpur compared to that at Beijing for α > 0.4 is due to a larger find-coarse mode separation radius of ∼0.76 μm in Beijing versus a value lower than ∼0.58 μm in Kanpur. Another reason lies in the weaker absorption by fine mode aerosols in Beijing. The distinctly lower near-infrared SSA in Kanpur when α < 1.4, compared to Beijing, may be attributed to lower aerosol concentrations in all α bins, resulting in less aggregation of absorbing black carbon particles on coarse particles in Kanpur. The classification of aerosol properties shows that the AOD accumulation mode in all seasons, even including spring, in Beijing and in post-monsoon and winter seasons in Kanpur can be attributed to fine particle coagulation or hygroscopic growth; during pre-monsoon and monsoon seasons in Kanpur, it is due to coarse mode particle accumulation or cloud contamination. [Copyright &y& Elsevier]

Abstract: Valuation of health effects of air pollution is becoming a critical component of the performance of cost–benefit analysis of pollution control measures, which provides a basis for setting priorities for action. Beijing has focused on control of transport emission as vehicular emissions have recently become an important source of air pollution, particularly during Olympic games and Post-games. In this paper, we conducted an estimation of health effects and economic cost caused by road transport-related air pollution using an integrated assessment approach which utilizes air quality model, engineering, epidemiology, and economics. The results show that the total economic cost of health impacts due to air pollution contributed from transport in Beijing during 2004–2008 was 272, 297, 310, 323, 298 million US$ (mean value), respectively. The economic costs of road transport accounted for 0.52, 0.57, 0.60, 0.62, and 0.58% of annual Beijing GDP from 2004 to 2008. Average cost per vehicle and per ton of PM10 emission from road transport can also be estimated as 106 US $/number and 3584 US $ t−1, respectively. These findings illustrate that the impact of road transport contributed particulate air pollution on human health could be substantial in Beijing, whether in physical and economic terms. Therefore, some control measures to reduce transport emissions could lead to considerable economic benefit. [Copyright &y& Elsevier]

Abstract: Traffic congestion and air pollution were two major challenges for the planners of the 2008 Olympic Games in Beijing. The Beijing municipal government implemented a package of temporary transportation control measures during the event. In this paper, we report the results of a recent research project that investigated the effects of these measures on urban motor vehicle emissions in Beijing. Bottom–up methodology has been used to develop grid-based emission inventories with micro-scale vehicle activities and speed-dependent emission factors. The urban traffic emissions of volatile organic compounds (VOC), carbon monoxide (CO), nitrogen oxides (NOx) and particulate matter with an aerodynamic diameter of 10 μm or less (PM10) during the 2008 Olympics were reduced by 55.5%, 56.8%, 45.7% and 51.6%, respectively, as compared to the grid-based emission inventory before the Olympics. Emission intensity was derived from curbside air quality monitoring at the North 4th Ring Road site, located about 7 km from the National Stadium. Comparison between the emission intensity before and during the 2008 Olympics shows a reduction of 44.5% and 49.0% in daily CO and NOx emission from motor vehicles. The results suggest that reasonable traffic system improvement strategies along with vehicle technology improvements can contribute to controlling total motor vehicle emissions in Beijing after the Olympic Games. [Copyright &y& Elsevier]

This paper presents a novel method for quantification of the total emission of gases from area sources using the mobile mini-DOAS (Differential Optical Absorption Spectroscopy) instrument, a ground based optical remote sensing technique. The presented method has been applied to measure the emission of SO2 and NO2 from the city of Beijing, P.R. China, on a time scale of approximately 2h. The measurements have been performed during two field campaigns, in April and in August 2005. The estimated emission of NO2 is roughly the same during the two field campaigns with an average emission of 189tonsd−1 during April and 174tonsd−1 during August. The estimated emission of SO2 varies greatly between the two periods, with an average emission of 293tonsd−1 during April and 52tonsd−1 during August. [Copyright &y& Elsevier]

Abstract: Mercury concentrations in size fractions of airborne particulate matter obtained from urban and suburban sites in Beijing in 2003 and 2004 are presented in this paper. The average concentrations of total particulate mercury were 1.18±0.82ngm−3 with a range of 0.18–3.51ngm−3at the urban site and 0.68±0.62ngm−3 with a range of 0.13–2.40ngm−3 at the suburban site. This is much higher than what is found in Europe and Northern America. The results implie that significant anthropogenic sources in Beijing contribute to the concentration of particulate mercury in air and therefore, to the mercury deposition in this region. There are clear seasonal variations in concentration of particulate mercury with highest concentrations in winter at urban and suburban sites. This illustrates the important contribution from coal burning to particulate mercury during the heating season. The mercury concentration in each size fraction of airborne particulates was closely related to its size range. The highest mercury concentration was found in the size fraction less than 1.1μm with average concentrations of 0.59±0.50 and 0.29±0.26ngm−3 at the urban and suburban sites, respectively. The mercury in this size fraction accounts for 45.7±9.5% and 41.9±8.2% of the total particulate mercury, respectively. This implies that a large fraction of the particulate mercury in this area can be transported long range before it becomes deposited. Based on the concentrations of size-fractionated particulate mercury in ambient air, the dry deposition fluxes of mercury were estimated to 407μgm−2 a−1 at the urban site and 270μgm−2 a−1 at the suburban site. More than 90% of the deposition flux came from particles larger than 1.1μm despite a substantial fraction of the Hg found in particles less than 1.1μm. [Copyright &y& Elsevier]

Himawari-8, a new generation geostationary satellite, with the Advanced Himawari Imager (AHI) providing Full Disk observation with high temporal resolution (10 min) exhibits prominent advantage in monitoring aerosols over East Asia region. The AHI has 16 channels from 0.46 to 13.3 to capture visible and infrared spectral data. In this paper, we developed a regional algorithm to retrieve the Aerosol Optical Depth (AOD) over Beijing area based on the AHI visible and short-wave infrared (SWIR) data from June to August 2016. The AHI surface reflectance at 0.46, 0.64, 0.86 and 2.3 μm channel was obtained using the lowest gas-corrected reflectance based on the three-month top of the atmosphere (TOA) data. The algorithm employed superposing technique and linear regression to iteratively train the AHI surface reflectance, and built optimal surface reflectance relationships between visible and SWIR bands with three Normalized Difference Vegetation Index (NDVI) classifications over Beijing area. Based on these surface reflectance relationships, the AHI AOD data were retrieved through the radiation transmission function. The AOD products from the AErosol RObotic NETwork (AERONET) ground measurement, the MODerate resolution Imaging Spectroradiometer (MODIS) and the Japan Aerospace Exploration Agency (JAXA) official AHI were used to evaluate the performance of our AOD retrievals. At diurnal scale, more than 66% of AHI AOD retrievals fell within the EE in the afternoon, which indicated that these retrievals could capture the regional aerosol variability over Beijing area. In contrast, the AHI JAXA AOD product significantly overestimated aerosol loadings. The low AOD biases (13:00–16:00) under low aerosol conditions from our retrieval algorithm demonstrated that the AHI surface reflectance assumptions are available. However, AHI retrievals in XiangHe overestimated AOD under high aerosol conditions, which indicated that the urban aerosol model is inappropriate over this site. In addition, our AHI AOD algorithm was only applied over Beijing area in the summer of 2016. The retrieval time-independence in this algorithm has not been estimated in fall and winter when NDVI is lower. Future study will investigate this surface algorithm at larger temporal and spatial scales. • A regional AHI aerosol retrieval algorithm over Beijing area is developed. • Our new AHI AOD product performs better than the JAXA AOD product. • The AHI assumed surface reflectance relationship performs well over Beijing area. • The single urban aerosol model is inappropriate over Beijing area. [ABSTRACT FROM AUTHOR]