Aerosol pollution significantly influences the interaction between solar radiation and the earth's atmosphere and seriously threatens human health. Numerous studies have applied machine learning models such as Extreme Gradient Boosting (XGBoost) and Light Gradient Boosting Machine (LightGBM) to estimate aerosol-related parameters, including aerosol optical depth and particulate matter concentrations (e.g., PM2.5). However, current aerosol products primarily provide horizontal or spatially discontinuous vertical data, lacking comprehensive three-dimensional (3D) coverage. To address this gap, we developed the XGBoost-LightGBM-Wavelet (XLW) model, integrating XGBoost, LightGBM, and wavelet transforms to merge multisource data. This approach, for the first time, produced high-resolution, three-dimensional, full-coverage aerosol distribution data for China in 2015. The model outputs a dataset of aerosol spatial distribution with a horizontal resolution of 0.05 degrees, and 167 layers within 10 km in the vertical direction. The XLW model demonstrates excellent predictive ability, effectively filling gaps in aerosol distribution. It enhances signal continuity and strengthens lower-layer signals, closely matching ground LiDAR observations and providing a more accurate representation compared to the Cloud-Aerosol LiDAR and Infrared Pathfinder Satellite Observation (CALIPSO) data. The dataset accurately reveals the 3D distribution of aerosols, which is meaningful for a comprehensive study of aerosol distribution at different altitudes in various regions. At 300 m height above ground level, the most polluted regions are the North China Plain and the Yangtze River Delta region, with an average aerosol extinction coefficient (AEC) of 0.34 and 0.40 km(-1), respectively. As the height increases to 1 km, the average AEC notably decreases to 0.23 and 0.24 km(-1) in the North China Plain and the Yangtze River Delta. By 3 km, aerosol distribution becomes sparse over most regions of China. For the vertical variations of aerosol distributions in typical cities, in the North China Plain and Yangtze River Delta, aerosol concentrations consistently decrease from the near-surface to 4 km. However, in the Pearl River Delta, aerosol concentrations decrease consistently from 0 to 2 km, with relatively stable between 2 and 3 km. Above 4 km, aerosol concentrations are nearly negligible in all typical cities. The XLW model can accurately produce a high-resolution, 3D, full-coverage aerosol spatial distribution dataset, which is vital for conducting thorough studies on aerosol transport, aerosol radiative effects, and climate change.

Dioxins (including 2,3,7,8-tetrachlorodibenzo-p-dioxin, as Group 1 Carcinogen) in the atmosphere mainly originate from incomplete combustion during municipal solid waste (MSW) incineration. To significantly reduce dioxins emission from the MSW incineration industry, China has promulgated a set of ambitious plans regulating MSW-related pollution; however, the emission reduction potentials and concomitant environmental and health impacts associated with the implementation of these programs on a national scale remain unknown. Here, we use real measurements from official environmental impact assessment systems and continuous emissions monitoring systems (covering 96.6% of national MSW incinerators) to estimate unit-level dioxins emission and concomitant environmental and health impacts. We find that in 2018, 99.3% and 66.7% of Chinese incinerators met such concentration and temperature standards, respectively, controlling the total emissions to 19.6 g toxic equivalency quantity and maintaining carcinogenic and noncarcinogenic risks significantly below safety levels nationwide. Fully achieving both current standards and future regulations will reduce emissions and health risks by 67.7% and 62.6%, respectively, with waste sorting program contributing the majority. This study reveals substantial benefits from curbing MSW-related dioxins pollution and underscores the promise of ongoing management.

Beijing faces the challenge of high levels of ozone (O-3) pollution. In this study, the Weather Research and Forecasting model and Community Multiscale Air Quality model (CMAQ) were used to simulate atmospheric O-3 concentrations in Beijing. To investigate the formation mechanisms and source contributions of O-3 pollution in different regions of Beijing, process analysis and the integrated source apportionment method within the CMAQ were applied to O-3 concentrations in the summer of 2018. The process analysis results showed that vertical diffusion was the major contributor to O-3 concentrations at all receptor sites in Beijing, at > 65.94 mu g/(m(3)center dot hr). Gas-phase chemical reactions consumed a significant amount of O-3 in urban and inner suburban areas (> -5.57 mu g/(m(3)center dot hr)), while near-surface chemical reactions made positive contributions in outer suburban areas (> 4.72 mu g/(m(3)center dot hr)). The O-3 formation chemical reactions indicated that NO titration, which removes O-3 at night-time, mainly occurred in urban areas. The weaker chemical reactions occurring near the surface in outer suburbs suggested that suburban-area O-3 was produced in the upper atmospheric layers and was transported vertically to the lower layers. The O-3 source apportionment results showed that boundary contributions were the dominant contributor to O-3 pollution in Beijing (> 40%). The contribution of non-local emissions to O-3 levels was significantly greater in the outer suburbs than in urban and inner suburban areas due to topography. This study increases the understanding of the complex processes of O-3 formation in different areas of Beijing and informs the implementation of O-3 control plans. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

为研究不同污染水平下,O3浓度对气温升高的敏感程度,利用2018—2020年5—9月近地层O3日最大8 h平均浓度(O3-8 h浓度)和日最高地面气温(Tmax)数据,拟合O3-8 h浓度对Tmax变化的响应斜率(mO3-T),据此对比分析不同类型站点mO3-T的差异和O3污染特征.结果表明:①各站点O3-8 h浓度均随Tmax升高而增加,在24～36℃气温范围内该趋势最明显.②城区点mO3-T最高,高达10.6μg/(m3·℃);北部远郊区点和北部背景点mO3-T较低,低至5.2μg/(m3·℃);近郊区点与城区点的mO3-T相当.③总体看,北京市mO3-T较高,与O3污染高发地—美国加州南海岸地区20世纪90年代相当,说明目前北京市O3污染水平可能与该时期加州南海岸地区相近.④周末效应分析表明,北京市北部远郊区点和北部背景点的周末效应均高于主城区点,用mO3-T表征的周末效应能更显著地体现不同区域间的差异.研究显示,mO3-T能表征北京市的O3污染特征以及目前O3污染治理水平所处阶段.

随着我国重点区域空气质量水平的整体改善,新疆天山北坡的污染问题日显突出.为了探究当地低层大气稀释扩散能力的季节性差异及其对污染的影响,综合运用多种观测资料,对PM2.5污染和气象条件的季节性差异及二者之间的联系进行了系统分析,并利用区域空气质量模型开展数值试验,对低层大气稀释扩散能力进行了量化.结果表明:①天山北坡主要城市冬季(12月—翌年1月)和春夏季(5—8月)PM2.5浓度最大可相差10.8倍.对环流形势、地面气象要素、下垫面和低层大气层结等气象条件分析发现,低层大气稀释扩散能力是造成PM2.5浓度差异较大的首要外因.②天山北坡主要城市春夏季的低层大气稀释扩散能力远高于冬季,最高为冬季的4.9倍;稀释扩散能力的逐月变化表明,稀释扩散能力最强和最弱月份最大相差5.6倍.而同处北方的京津冀地区,春夏季与冬季最大相差2.0倍.研究显示,合理利用低层大气稀释扩散能力的季节性差异,施行系统性的错峰生产,竭力减少冬季大气污染物排放,将是改善天山北坡城市空气质量的有效途径.

大多数针对北京地区冬季重污染过程的研究侧重于气溶胶,关于该过程中雾的研究较少.利用北京南郊观象台L波段探空和地面气象观测资料,以及MODIS和VISSR卫星数据等,对2013年1月12—15日北京地区重污染期间的雾进行分析,发现4 d中共发生2次辐射雾和2次平流雾,每天的雾在类型、垂直分布、形成过程、层结等方面都完全不同:12日清晨为充分发展的辐射雾,辐射雾的生成和发展使近地层稳定层结转变为近中性;13日清晨为2层相连的高空平流雾,分别来自不同源地,平流雾的到来造成近地层雾的消散,也使低层大气扩散能力有所加强;14日清晨出现辐射雾,其发展仅限于初生阶段,生存时间仅约2 h,期间存在贴地逆温;15日清晨为加深的平流雾,较前1天夜间的平流雾,雾顶高度抬升约500 m.鉴于北京地区冬季重污染过程中,雾在形成过程、垂直结构和层结影响等方面呈现出的复杂和多变的状况,针对重污染期间雾层的研究,以及其在垂直扩散和辐射等方面的效应研究都有待加强.

The Beijing area experienced daily ozone increases after the Belt and Road Forum in May 2017, with the maximum hourly O-3 peak exceeding 400 mu g/m(3). The high O-3 event was analyzed by using observed data and model simulations. Results indicated that the local photochemistry was the major driver boosting O-3 formation for northern suburban sites and regional transport in the late afternoon made another peak in O-3 diurnal variation for urban sites. A prominent VOC-limited sensitivity regime was dominant in the Beijing area, even over suburban areas far away from the Beijing urban center. The rapid increase in VOCs emissions from both biogenic and anthropogenic sources under high air temperatures provided the needed VOCs for O-3 formation, resulting in a dramatic O-3 increase after the summit. It was also found that PM2.5 experienced steady daily increases after the summit, leading to a gradual decrease in the UV radiation measured at the ground; however, O-3 showed a dramatically increasing trend, in contrast to the expectation that the high-level PM2.5 would restrain the O-3 formation by the theoretical deduction in the O-3 and aerosol interaction. The results suggest that the abrupt change in emissions during the study period overwhelmed the effects of the O-3 and aerosol interaction. Such temporary changes in emissions should be considered in mitigation strategies of O-3 control.

The provision of climate services for assessing and governing environmental problems such as poor air quality requires interactions between scientists and decision-makers. Air quality information services in China mainly focus on the coming days to weeks. However, users may benefit from air quality information on climate time-scales—from months to decades; hereafter air quality climate services. We focused on key decision-makers and stakeholders that are users of air quality climate services and conducted five workshops with these identified users to ascertain their priorities for air quality climate services, and the reasoning behind these priorities. We also conducted a choice-based conjoint experiment via an online survey distributed amongst regional and local Climate Centres and Environmental Monitoring Centres to assess quantitatively the decision-makers' needs. The results from the workshops and the survey showed that the needs for air quality climate services by users in China mainly relate to seasonal forecasting of winter haze events (PM2.5 levels and/or the meteorological conditions conducive to the dispersion of the air pollution); there is also some interest in long-term projections of haze under climate change and a growing interest in ozone pollution in summer. Spatial relevance is perceived to be important to regional and city-level stakeholders who prefer information on the city-level, whilst national-wide information is important for national government agencies. A high level of reliability of forecasts was needed for uptake. The findings on the needs for air quality climate services by potential users can support researchers and policy-makers in developing the scientific capacity and providing tailored and effective air quality climate services in China.

基于CAMx模型的PSAT颗粒物源示踪技术,对2016年济南都市圈PM2.5污染、区域传输规律及行业贡献进行了定量分析.结果表明:从PM2.5年均来源贡献率看,济南市本地排放约占50％,来自济南都市圈总贡献率约占75％.圈内城市间相互贡献明显,最高达13％.夏季,本地贡献最大,区域传输中鲁东地区对研究区域影响最高,为24％;受冬季季风影响,来自京津冀方向的区域传输增多,最高达24％.目前,对济南都市圈PM2.5贡献较大的污染源为工业锅炉、钢铁、扬尘源、化工、冶金、建材行业和机动车,有针对性地削减上述污染源排放,可达到快速、有效降低PM2.5浓度的目的.

With a rapid increase in air traffic, aviation has become an increasingly important contributor to anthropogenic air pollutants (particularly nitrogen oxides (NOx)) over China. This study provides the first overall estimation of the aviation emissions from all civil airports in mainland China as well as the associated contribution to ambient air quality. First, aircraft emissions (NOx, sulfur dioxide (SO2), carbon monoxide (CO), hydro-carbons (HC), particulate matter (PM2.5 and PM10), volatile organic carbons (VOCs) and black carbon (BC)) during landing and take-off cycles (below 3 km) are estimated for both recent (2000-2016) and future (2020) scenarios. Second, the corresponding environmental impacts are measured by the Comprehensive Air Quality Model with extensions (CAMx). The results have insightful policy implications for China's aviation planning. (1) Generally, China's aviation emissions and their effect on air quality have been and will continue to increase. (2) Among species, NOx dominated China's aircraft emissions in terms of both emission amount and environmental impact, while PM2.5 generated an extensive influence. (3) With respect to spatial distribution, the air quality effect was highly concentrated at emission-intense airports that served economic zones and/or tourist spots.

针对低空急流(Low-Level Jet,LLJ)这种与空气污染等现象密切相关的天气现象,综述了低空急流的定义、日变化特征、季节性变化特征,以及包括惯性振荡理论、地形的热力和动力作用、天气系统强迫等低空急流的形成和发展机制,总结国内外开展的低空急流数值模拟及其在大气污染源排放污染物的输送、扩散中的影响等研究成果,提出了下一步应开展低空急流的选取标准及其与空气污染学科的交叉研究,并开展适宜本地区低空急流数值模拟的参数化方案和小尺度研究等建议.

Aerosol Vertical Structure (AVS) retrieved from CALIOP was used to resolve contradictory seasonality between MODIS aerosol optical depth (AOD) data and surface PM2.5 over the Northern China Plain (NCP). CALIOP level 2 data was used to determine seasonally averaged day and night time AVS during 2011-2015 at wavelengths of 532 and 1064 nm. Results showed that the AVS differed markedly between seasons. It was the most complex during summer days at 532 nm, when a nose like peak was apparent between 500 and 1000 m. This structure was attributed to strong aerosol hygroscopic growth, and accounted for approximately 40% of column AOD. The lowest section of AVS at 532 nm which is important for surface PM2.5 showed the highest during winter, an improved seasonality compared to column AOD; however, discrepancies were apparent during other seasons. Conversely, AVS at 1064 tun was virtually identical to observed PM2.5, implying that coarse particulates are more representative of PM2.5 in the NCP as compared to fine particulates. Thus, MODIS AOD at 550 nm may not be a good proxy for surface PM2.5 retrieval. Using CALIOP active detection, day and night time AOD were obtained, and showed that seasonality was more reasonable at night as compared to during the day. Comparisons of reconstructed daytime CALIOP AOD with MODIS AOD and AERONET AOD implied that winter AOD over the NCP was not as low as indicated by MODIS AOD.

The 5-year (2011-2015) spaceborne lidar CALIOP (cloud-aerosol lidar with orthogonal polarization) data were aggregated to obtain a seasonal three-dimensional (3-D) distribution of aerosols over the Northern Pacific (NP). Superior to the Moderate-resolution Imaging Spectroradiometer (MODIS) product, which provided only the bulk Aerosol Optical Depth (AOD), the vertical high-resolution Aerosol Extinction Coefficient (AEC) obtained from the CALIOP product enabled us to determine the AOD for the prescribed layers. By integrating the AEC at the prescribed height interval, the AOD beneath and above 2 km was obtained to characterize the aerosol loading in the surface layer (SL) and the free troposphere (FT), respectively. The AOD in the SL and FT present different seasonal variation patterns over the NP. The SL AOD exhibited the highest level in the winter, which was caused by sea salt emissions driven by the strongest winds. However, a much higher FT AOD occurred over the NP in the springtime compared with that of other seasons, indicating that the most significant transpacific transport occurred in the springtime, mainly in the FT. Fine resolution aerosol distributions in cross section along a transpacific direction were extracted from the CALIOP product as well. Along the cross section, aerosol loading was most abundant below 2 km for all the seasons. However, the detectable aerosol layer may extend to 10 kin high in the springtime, which is much higher than that in the other seasons, and the aerosol layers below and above 2 km were separated over the remote NP. The CALIOP data demonstrated that dust plays a role in aloft aerosol transport. In terms of aerosol transport in the FT, an 8-fold decrease in the FT AOD occurred during the journey from East Asia to the Eastern Pacific in the summer, which was the sharpest decrease compared with the smallest one, which has 3-fold decrease occurred in the spring. Aerosol transport in the FT contributed 19% of the AOD over western North America (NA) in the spring, which was much higher than that in other seasons, and the aloft aerosol transport between 2 and 4 kin high corresponded to a fine PM concentration of 1-2 mu g m(-3) as a contributor to air quality over western NA.

To cope with the need in response to heavy pollution,a quick method to assess the quantified effects of countermeasures was developed based on numerical air quality model and adjusted according to PM2.5 measurement.By takingdifferent distribution plans of PM2.5 component and response coefficients,several results could be obtained.Thus,a range of effects for countermeasures was formed.By applying the methodology,a suite of quantified assessment of vehicle usage limit was implemented for countermeasure,which was the most frequently used in response to heavy pollution.The methodology developed could obtain the quantified effects of countermeasures in a rapid way,and provide technique support in time for management agency.

大气化学机理是空气质量模型中重要的组成部分,是研究大气化学过程的重要手段和方法.综述了碳键机理(CBM)、区域大气化学机理(RACM)和加州大气污染研究中心机理(SAPRC)3类常用归纳化学机理的发展历程,比较了各化学机理在物种集总方式、物种数和化学反应数等方面的差异,介绍了各类大气化学机理最新版本的更新及在空气质量模型中的应用情况.对不同大气化学机理在空气质量模型中应用的比较进行了分析和总结,讨论了导致不同大气化学机理模拟结果差异的原因,并对空气质量模型中不同大气化学机理的选择和应用提出了建议.

A suite of aircraft measurements was conducted over the Gulf of Tonkin, located downwind to the east of Mainland Southeast Asia (MSE), between March 23rd and April 6th, 2015. To the best of our knowledge, this campaign of 11 flights (totaling 34.4 h) was the first in-flight measurement over the region. Measurements of sulfur dioxide, nitrogen oxides, ozone, carbon monoxide, black carbon and the particulate scattering coefficient were recorded at approximately 1 500 m (low level) and 3 000 m (high level). Significantly higher measurements of black carbon, carbon monoxide and ozone in the high level on March 23rd and April 5th and 6th were directly related to biomass burning in the MSE and were comparable to severe pollution events at the surface. Similarly, relatively low pollutant concentrations were observed at both altitudes between March 23rd and April 5th. A combined analysis of the measurements with meteorology and satellite data verified that the plumes captured at 3 000 m were attributed to transport in the high altitude originating from biomass burning in northern MSE. Furthermore, each plume captured by the measurements in the high level corresponded to heavy regional air pollution caused by biomass burning in northern MSE. In addition, relatively low levels of the measured pollutants corresponded to relatively light pollution levels in MSE and its adjacent areas. Taken together, these results indicated that aircraft measurements were accurate in characterizing the variation in transport and pollutant levels. During the most active season of biomass burning in MSE, pollutant emissions and their regional impact could vary on an episodic basis. Nonetheless, such concentrated emissions from biomass burning is likely to lead to particularly high atmospheric-loading of pollutants at a regional level and, depending on weather conditions, has the potential of being transported over considerably longer distances. Further investigation of the short-term impacts of such concentrations therefore appears prudent.

Vertical distribution of aerosol extinction coefficient (AEC) representing aerosol concentration level was investigated using satellite observation obtained by CALIOP over Jing-Jin-Ji (JJJ) area during 2011-2015.Results showed that vertical distribution of AEC had a distinct seasonal variability,especially below 2 km in altitude.Aerosol optical depth (AOD) integrated from full-layer AEC also varied significantly with seasons.AOD was much higher in summer (0.7) than that in other seasons,which was substantially influenced by ambient relative humidity.However,the opposite characteristic of low-layer AEC was observed below 500 m with the highest value of 0.65 km-1 in winter and smaller ones in spring and summer.There was a remarkably difference of low-layer AEC between day and night in summer and autumn with the maximum of 0.65 km-1 after midnight,which was 2.5 times in the early afternoon.The large day-night discrepancy of low-layer relative humidity was the major cause for the contrast of extinction coefficient.Zonal vertical distribution of AEC cross section through JJJ area showed that the level of aerosol concentration was higher in low-layer over south part of the region in summer night,while in other seasons,no obvious south-north differences were observed.

The Beijing-Tianjin-Hebei (BTH) region experiences severe haze episodes throughout the year, and especially during the winter heating season. Residential combustion of coal has increasing been cited as a possible source for the PM2.5 pollution that causes the haze episodes. To investigate these claims, a WRF-CMAQ system is used to reproduce the regional haze episodes observed during December 2015. The contribution of residential coal combustion to PM2.5 concentrations in the BTH region is quantified using the Brute Force approach. Across the region, residential coal combustion contributed 46% of the monthly averaged PM2.5 concentration (3% each from Beijing and Tianjin and 40% from Hebei Province). During the haze episodes, the contribution varied between 30 and 57%. At the city scale, the contribution ranged from 22 to 58% averaged across the month and 15–65% during the haze episodes. Langfang was the city that was the most affected by residential coal combustion in the BTH region. The large contribution to air pollution in Tianjin and Beijing from households in Hebei Province suggests that regional control measures are required.

By aggregating MODIS (moderate-resolution imaging spectroradiometer) AOD (aerosol optical depth) and OMI (ozone monitoring instrument) UVAI (ultra violet aerosol index) datasets over 2010–2014, it was found that peak aerosol loading in seasonal variation occurred annually in spring over the Gulf of Tonkin (17–23°N, 105–110°E). The vertical structure of the aerosol extinction coefficient retrieved from the spaceborne lidar CALIOP (cloud-aerosol lidar with orthogonal polarization) showed that the springtime peak AOD could be attributed to an abrupt increase in aerosol loading between altitudes of 2 and 5km. In contrast, aerosol loading in the low atmosphere (below 1km) was only half of that in winter. Wind fields in the low and high atmosphere exhibited opposite transportation patterns in spring over the Gulf of Tonkin, implying different sources for each level. By comparing the emission inventory of anthropogenic sources with biomass burning, and analyzing the seasonal variation of the vertical structure of aerosols over the Northern Indo-China Peninsula (NIC), it was concluded that biomass burning emissions contributed to high aerosol loading in spring. The relatively high topography and the high surface temperature in spring made planetary boundary layer height greater than 3km over NIC. In addition, small-scale cumulus convection frequently occurred, facilitating pollutant rising to over 3km, which was a height favoring long-range transport. Thus, pollutants emitted from biomass burning over NIC in spring were raised to the high atmosphere, then experienced long-range transport, leading to the increase in aerosol loading at high altitudes over the Gulf of Tonkin during spring.

In order to investigate long-range transport of the air pollution in the East Asia, air pollutants, including SO2, NOx, CO, and O3, were observed by aircraft measurement over the coastal and offshore area of Yellow Sea of China in April 2011. NOx and SO2 seemed to become moderate in recent years, and the concentrations during the whole observations ranged from 0.49 to 9.57 ppb and from 0.10 to 16.02 ppb, respectively. The high concentrations of CO were measured with an average value of 0.98 ppm. The measured O3 average concentration was 76.25 ppb, which showed a higher level comparing with the results from some previous studies. Most of the results for the concentration values generally followed the typical characteristic of vertical and spatial distribution, which were “low altitude > high altitude” and “land/coastal > sea,” respectively. Transport of polluted air mass from the continent to the aircraft measurement area was confirmed in some days during the observation by the meteorological analysis, while the measurement results supposed to represent the background level of the pollutants in rest days. Additionally, some small-scale air pollution plumes were observed. Significant positive correlations between NOx and SO2 indicated that these two species originated from the same region. On the other hand, good positive correlations between NOx and O3 found during 2-day flight suggested that the O3 formation was probably under “NOx-limited” regime in these days.