Impact of air transport and secondary formation on haze pollution in the Yangtze River Delta: In situ online observations in Shanghai and Nanjing

2020 ◽  
Author(s):  
Peng Sun
Keyword(s):  
Fine Particles ◽  
Eastern China ◽  
Northern China ◽  
Organic Aerosol ◽  
Photochemical Activity ◽  
Air Transport ◽  
Ozone Level ◽  
Haze Pollution ◽  
The Yrd ◽  
Pollution Episodes

<p>Despite frequent haze pollution in China in recent years, our knowledge of regional pollution episodes associated with air transport and synoptic weather systems is limited. In this study, we conducted two intensive campaigns simultaneously to measure the highly time-resolved chemical composition of fine particles (PM<sub>2.5</sub>) in suburban Shanghai and Nanjing during the winter of 2017 and the summer of 2018. The average PM<sub>2.5</sub> mass concentrations were 53.9 (65.7) µg m<sup>-3</sup> and 32.8 (37.3) µg m<sup>-3 </sup>in Shanghai (Nanjing) in winter and summer, respectively. In winter, extreme haze episodes were observed synchronously with enhanced contributions of nitrate at both sites and of low-volatile oxidized organic aerosol (LV-OOA) in Shanghai. Long-range transport from Northern China was demonstrated to play an important role in the episodes, which occurred simultaneously at both sites. Influenced by the cold fronts, Nanjing had a relatively longer pollution duration, whereas Shanghai exhibited faster PM increases. In summer, air masses passing though the city-clusters of the YRD were responsible for the pollution episodes. Low wind speeds, which favored the accumulation of primary aerosols, and strong photochemical activity indicated by high ozone level, which promoted the formation of secondary aerosols, resulted in elevated contributions of nitrate, Hydrocarbon-like organic aerosol (HOA) and semi-volatile oxidized organic aerosol (SV-OOA) to PM in Shanghai. In addition, a pollution episode dominated by increases of nitrate and organic aerosols was observed in Nanjing two days later despite the clean situation in Shanghai. Our results highlight the importance of regional or sub-regional emission control to mitigate haze pollution in city clusters, such as the YRD in Eastern China.</p>

scholarly journals Impacts of black carbon on the formation of advection-radiation fog during a haze pollution episode in eastern China

2019 ◽  
Author(s):  
Qiuji Ding ◽  
Jianning Sun ◽  
Xin Huang ◽  
Aijun Ding ◽  
Jun Zou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Eastern China ◽  
Vertical Mixing ◽  
Radiation Fog ◽  
Haze Event ◽  
Pollution Episode ◽  
Haze Pollution ◽  
Bc Aerosols ◽  
The Yrd ◽  
The Impact

Abstract. Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze event. The impact of aerosols on fog formation, yet to be revealed, can be critical in understanding and predicting of fog-haze event. In this study, we used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to investigate a heavy fog event during a multiday intense haze pollution episode in early December 2013 in the Yangtze River Delta (YRD) region in eastern China. Using the WRF-Chem model, we conducted four parallel numerical experiments to evaluate the roles of aerosol-radiation interaction (ARI), aerosol-cloud interaction (ACI), black carbon (BC) and none BC (non-BC) aerosols in the formation and maintenance of the heavy fog event. Only when the aerosols' feedback processes are considered can the model well capture the haze pollution and the fog event. We find that the ARI dominates this fog-haze episode while the effects of ACI are negligible. Our analyses shows that BC plays a more important role in fog formation than non-BC aerosols. The dome effect of BC leads to an increase of air moisture over the sea by reducing PBLH and weakening vertical mixing, thereby confining more water vapor in the near-surface layer. The strengthened daytime onshore flow by a cyclonic wind anomaly, induced by contrast temperature perturbation over land and sea, transports moister air to the YRD region, where the suppressed PBLH and weakened daytime vertical mixing maintain the high moisture level. Then the heave fog forms due to the surface cooling at night in this region. This study highlights the importance of anthropogenic emissions in the formation of advection-radiation fog in the polluted coastal areas.

scholarly journals Aerosol optical characteristics and their vertical distributions under enhanced haze pollution events: effect of the regional transport of different aerosol types over eastern China

2017 ◽  
Author(s):  
Tianze Sun ◽  
Huizheng Che ◽  
Bing Qi ◽  
Yaqiang Wang ◽  
Yunsheng Dong ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Condition ◽  
Dust Particles ◽  
Hygroscopic Growth ◽  
Emission Layer ◽  
Regional Transport ◽  
Haze Pollution ◽  
Fine Mode ◽  
The Yrd ◽  
Pollution Events

Abstract. The climatological variation of aerosol properties and the planetary boundary layer (PBL) during 2013–2015 over the Yangtze River Delta (YRD) region were investigated by employing ground-based Microwave Pulse Lidar (MPL) and CE-318 sun-photometer observations. Combining MODIS and CALIPSO satellite products, enhanced haze pollution events affected by different types of aerosol over the YRD region were analyzed through vertical structures, spatial distributions, backward trajectories, and the Potential Source Contribution Function (PSCF) model. The results show that aerosols in the YRD are dominated by fine-mode particles, except in March. The aerosol optical depth (AOD) in June and September is higher due to high single scattering albedo (SSA) from hygroscopic growth, but is lower in July and August due to wet deposition from precipitation. The PBL height (PBLH) is greater (means ranging from 1.23 to 1.84 km) and more variable in the warmer months of March to August, due to the stronger diurnal cycle and exchange of heat. Northern fine-mode pollutants are brought to the YRD at a height of 1.5 km. The SSA increases blocking the radiation to the surface, and cooling the surface, thereby weakening turbulence, lowering the PBL, and in turn accelerating the accumulation of pollutants, creating a feedback to the cooling effect. Originated from the deserts in Xinjiang and Inner Mongolia, long-range transported dust masses are seen at heights of about 2 km over the YRD region with an SSA440 nm below 0.84, which heat air and upraise PBL, accelerating the diffusion of dust particles. Regional transport from biomass burning spots to the south of the YRD region bring mixed aerosol particles at a height below 1.5 km, resulting in an SSA440 nm below 0.89. During the winter, the accumulation of local emission layer is facilitated by stable weather condition, staying within the PBL even below 0.5 km.

scholarly journals Chemical characterization of aerosols at the summit of Mountain Tai in Central East China

2011 ◽  
Vol 11 (14) ◽  
pp. 7319-7332 ◽  
Author(s):  
C. Deng ◽  
G. Zhuang ◽  
K. Huang ◽  
J. Li ◽  
R. Zhang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Fine Particles ◽  
Eastern China ◽  
Chemical Characterization ◽  
Northern China ◽  
Water Soluble ◽  
World Heritage Site ◽  
High Concentration ◽  
Central Eastern ◽  
The Impact

Abstract. PM2.5 and TSP samples were collected at the summit of Mountain Tai (MT) (1534 m a.s.l.) in spring 2006/2007 and summer 2006 to investigate the characteristics of aerosols over central eastern China. For comparison, aerosol samples were also collected at Tazhong, Urumqi, and Tianchi in Xinjiang in northwestern China, Duolun and Yulin in northern China, and two urban sites in the megacities, Beijing and Shanghai, in 2007. Daily mass concentrations of TSP and PM2.5 ranged from 39.6–287.6 μg m−3 and 17.2–235.7 μg m−3 respectively at the summit of MT. Averaged concentrations of PM2.5 showed a pronounced seasonal variation with higher concentration in summer than spring. 17 water-soluble ions (SO42−, NO3−, Cl−, F−, PO43−, NO2−, CH3COO−, CH2C2O42−, C2H4C2O42−, HCOO−, MSA, C2O42−, NH4+, Ca2+, K+, Mg2+, Na+), and 19 elements of all samples were measured. SO42−, NO3−, and NH4+ were the major water-soluble species in PM2.5, accounting for 61.50 % and 72.65 % of the total measured ions in spring and summer, respectively. The average ratio of PM2.5/TSP was 0.37(2006) and 0.49(2007) in spring, while up to 0.91 in summer, suggesting that aerosol particles were primarily comprised of fine particles in summer and of considerable coarse particles in spring. Crustal elements (e.g., Ca, Mg, Al, Fe, etc.) showed higher concentration in spring than summer, while most of the pollution species (SO42−, NO3−, K+, NO2−, NH4+, Cl−, organic acids, Pb, Zn, Cd, and Cr) from local/regional anthropogenic emissions or secondary formation presented higher concentration in summer. The ratio of Ca/Al suggested the impact of Asian dust from the western deserts on the air quality in this region. The high concentration of K+ in PM2.5 (4.41 μg m−3) and its good correlation with black carbon (r = 0.90) and oxalic acid (r = 0.87) suggested the severe pollution from biomass burning, which was proved to be a main source of fine particles over central eastern China in summer. The contribution of biomass burning to the fine particle at MT accounted for 7.56 % in spring and 36.71 % in summer, and even reached to 81.58 % on a day. As and Pb were two of the most enriched elements. The long-range transport of aerosols spread the heavy pollution from coal-mining/coal-ash to everywhere over China. Anthropogenic air-pollution was evidently rather severe at MT, though it has been declared by UNESCO to be a World Heritage site.

scholarly journals Haze Optical Properties from Long-Term Ground-Based Remote Sensing over Beijing and Xuzhou, China

2018 ◽  
Vol 10 (4) ◽  
pp. 518 ◽  
Author(s):  
Kai Qin ◽  
Luyao Wang ◽  
Jian Xu ◽  
Husi Letu ◽  
Kefei Zhang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Global Climate ◽  
Complex Refractive Index ◽  
Eastern China ◽  
Single Scattering ◽  
Dust Particles ◽  
Haze Pollution

Aerosol haze pollution has had a significant impact on both global climate and the regional air quality of Eastern China, which has a high proportion of high level pollution days. Statistical analyses of aerosol optical properties and direct radiative forcing at two AERONET sites (Beijing and Xuzhou) were conducted from 2013 to 2016. Results indicate: (1) Haze pollution days accounted for 26% and 20% of days from 2013 to 2016 in Beijing and Xuzhou, respectively, with the highest proportions in winter; (2) The averaged aerosol optical depth (AOD) at 550 nm on haze days were about 3.7 and 1.6 times greater than those on clean days in Beijing and Xuzhou, respectively. At both sites, the maximum AOD occurred in summer; (3) Hazes were dominated by fine particles at both sites. However, as compared to Xuzhou, Beijing had larger coarse mode AOD and higher percentage of small α. This data, together with an analysis of size distribution, suggests that the hazes in Beijing were more susceptible to coarse dust particles than Xuzhou; (4) During hazes in Beijing, the single scattering albedo (SSA) is significantly higher when compared to clean conditions (0.874 vs. 0.843 in SSA440 nm), an increase much less evident in Xuzhou. The most noticeable differences in both SSA and the imaginary part of the complex refractive index between Beijing and Xuzhou were found in winter; (5) In Beijing, the haze radiative forcing produced an averaged cooling effect of −113.6 ± 63.7 W/m2 at the surface, whereas the averaged heating effect of 77.5 ± 49.7 W/m2 within the atmosphere was at least twice as strong as clean days. In Xuzhou, such a radiative forcing effect appeared to be much smaller and the difference between haze and clean days was insignificant. Derived from long-term observation, these findings are more significant for the improvement of our understanding of haze formation in China and the assessment of its impacts on radiative forcing of climate change than previous short-term case studies.

scholarly journals The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

2018 ◽  
Vol 18 (2) ◽  
pp. 1419-1436 ◽  
Author(s):  
Bingliang Zhuang ◽  
Tijian Wang ◽  
Jane Liu ◽  
Huizheng Che ◽  
Yong Han ◽  
...  
Keyword(s):  
Optical Properties ◽  
Physical Properties ◽  
Yangtze River ◽  
Eastern China ◽  
Yangtze River Delta ◽  
River Delta ◽  
Transfer Model ◽  
Size Distributions ◽  
Haze Pollution ◽  
The Yrd

Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only  ∼  4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dust- and black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m−2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m−2) at the TOA. Similarly, the coarse-mode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

scholarly journals Characterization of atmospheric trace gases and particle matters in Hangzhou, China

2017 ◽  
Author(s):  
Gen Zhang ◽  
Honghui Xu ◽  
Bing Qi ◽  
Rongguang Du ◽  
Ke Gui ◽  
...  
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Fine Particles ◽  
Trace Gases ◽  
Photochemical Pollution ◽  
Seasonal Scale ◽  
Haze Pollution ◽  
Synoptic Conditions ◽  
The Yrd ◽  
Local Emissions

Abstract. The Yangtze River Delta (YRD) is one of the most densely populated regions in China with severe air quality issues, which has not been fully understood. Thus, in this study, based on one-year (2013) continuous measurement at a National Reference Climatological Station (NRCS, 30.22° N, 120.17° E, 41.7 m a.s.l.) in the center of Hangzhou in the YRD, we investigated the seasonal characteristics, interspecies relationships, and the local emissions and the regional potential source contributions of trace gases (including O3, NOx, NOy, SO2 and CO) and particulate matters (PM2.5 and PM10). Results revealed severe two-tier air pollution (photochemical and haze pollution) occurred in this region, with frequent exceedances in O3 (38 days) and PM2.5 (62 days). O3 and PM2.5 both exhibited distinct seasonal variations with reversed patterns: O3 reaching a maximum in warm seasons (May and July) but PM2.5 in cold seasons (November to January). The overall results from interspecies correlation indicated a strong local photochemistry favoring the O3 production under a volatile organic compound (VOC)-limited regime, whereas it moved towards an optimum O3 production zone during warm seasons, accompanying with a formation of secondary fine particles under high O3. The emission maps of PM2.5, CO, NOx, and SO2 demonstrated that local emissions were both significant for these species on seasonal scale. The contributions from the regional transports among inland cities (Zhejiang, Jiangsu, Anhui, and Jiangxi Province) on seasonal scale were further confirmed to be crucial to air pollution at NRCS site by using the backward trajectories simulations. Air masses transported from Yellow Sea, East Sea, and South Sea were also found to be highly relevant to the elevated pollutants, especially for NOx and O3. Case studies of photochemical pollution (O3) and haze (PM2.5) episodes both suggested the combined importance of local atmospheric photochemistry and synoptic conditions during the accumulation (related with anticyclones) and dilution process (related with cyclones). This study supplements a general picture of the air pollution state in the YRD region, specifically elucidates the role of local emission and regional transport, and interprets the physical and photochemical processes during haze and photochemical pollution episodes. Moreover, this work suggests that cross-regional control measures are crucial to improve air quality in the YRD region, and further emphasizes the importance of local thermally induced circulation on air quality.

scholarly journals Impacts of water partitioning and polarity of organic compounds on secondary organic aerosol over eastern China

2020 ◽  
Vol 20 (12) ◽  
pp. 7291-7306
Author(s):  
Jingyi Li ◽  
Haowen Zhang ◽  
Qi Ying ◽  
Zhijun Wu ◽  
Yanli Zhang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Air Quality ◽  
Organic Compounds ◽  
Activity Coefficients ◽  
Secondary Organic Aerosol ◽  
Eastern China ◽  
Organic Aerosol ◽  
Water Mixture ◽  
Water Partitioning ◽  
The Yrd

Abstract. Secondary organic aerosol (SOA) is an important component of fine particular matter (PM2.5). Most air quality models use an equilibrium partitioning method along with the saturation vapor pressure (SVP) of semivolatile organic compounds (SVOCs) to predict SOA formation. However, the models typically assume that the organic particulate matter (OPM) is an ideal mixture and ignore the partitioning of water vapor to OPM. In this study, the Community Multiscale Air Quality model (CMAQ) is updated to investigate the impacts of water vapor partitioning and nonideality of the organic–water mixture on SOA formation during winter (January) and summer (July) of 2013 over eastern China. The updated model treats the partitioning of water vapor molecules into OPM and uses the universal functional activity coefficient (UNIFAC) model to estimate the activity coefficients of species in the organic–water mixture. The modified model can generally capture the observed surface organic carbon (OC) with a correlation coefficient R of 0.7 and the surface organic aerosol (OA) with the mean fractional bias (MFB) and mean fractional error (MFE) of −0.28 and 0.54, respectively. SOA concentration shows significant seasonal and spatial variations, with high concentrations in the North China Plain (NCP), central China, and the Sichuan Basin (SCB) regions during winter (up to 25 µg m−3) and in the Yangtze River Delta (YRD) during summer (up to 16 µg m−3). In winter, SOA decreases slightly in the updated model, with a monthly averaged relative change of 10 %–20 % in the highly concentrated areas, mainly due to organic–water interactions. The monthly averaged concentration of SOA increases greatly in summer, by 20 %–50 % at the surface and 30 %–60 % in the whole column. The increase in SOA is mainly due to the increase in biogenic SOA in inland areas and anthropogenic SOA in coastal areas. As a result, the averaged aerosol optical depth (AOD) is increased by up to 10 %, and the cooling effect of aerosol radiative forcing (ARF) is enhanced by up to 15 % over the YRD in summer. The aerosol liquid water content associated with OPM (ALWorg) at the surface is relatively high in inland areas in winter and over the ocean in summer, with a monthly averaged concentration of 0.5–3.0 and 5–7 µg m−3, respectively. The hygroscopicity parameter κ of OA based on the κ–Köhler theory is determined using the modeled ALWorg. The correlation of κ with the O:C ratio varies significantly across different cities and seasons. Analysis of two representative cities, Jinan (in the NCP) and Nanjing (in the YRD), shows that the impacts of water partitioning and nonideality of the organic–water mixture on SOA are sensitive to temperature, relative humidity (RH), and the SVP of SVOCs. The two processes exhibit opposite impacts on SOA in eastern China. Water uptake increases SOA by up to 80 % in the organic phase, while including nonunity activity coefficients decreases SOA by up to 50 %. Our results indicate that both water partitioning into OPM and the activity coefficients of the condensed organics should be considered in simulating SOA formation from gas–particle partitioning, especially in hot and humid environments.

scholarly journals Aerosol optical characteristics and their vertical distributions under enhanced haze pollution events: effect of the regional transport of different aerosol types over eastern China

2018 ◽  
Vol 18 (4) ◽  
pp. 2949-2971 ◽  
Author(s):  
Tianze Sun ◽  
Huizheng Che ◽  
Bing Qi ◽  
Yaqiang Wang ◽  
Yunsheng Dong ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Conditions ◽  
Dust Particles ◽  
Hygroscopic Growth ◽  
Emission Layer ◽  
Regional Transport ◽  
Haze Pollution ◽  
Fine Mode ◽  
The Yrd ◽  
Pollution Events

Abstract. The climatological variation of aerosol properties and the planetary boundary layer (PBL) during 2013–2015 over the Yangtze River Delta (YRD) region were investigated by employing ground-based Micro Pulse Lidar (MPL) and CE-318 sun-photometer observations. Combining Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite products, enhanced haze pollution events affected by different types of aerosol over the YRD region were analyzed through vertical structures, spatial distributions, backward trajectories, and the potential source contribution function (PSCF) model. The results show that aerosols in the YRD are dominated by fine-mode particles, except in March. The aerosol optical depth (AOD) in June and September is higher due to high single scattering albedo (SSA) from hygroscopic growth, but it is lower in July and August due to wet deposition from precipitation. The PBL height (PBLH) is greater (means ranging from 1.23 to 1.84 km) and more variable in the warmer months of March to August, due to the stronger diurnal cycle and exchange of heat. Northern fine-mode pollutants are brought to the YRD at a height of 1.5 km. The SSA increases, blocking the radiation to the surface, and cooling the surface, thereby weakening turbulence, lowering the PBL, and in turn accelerating the accumulation of pollutants, creating a feedback to the cooling effect. Originated from the deserts in Xinjiang and Inner Mongolia, long-range transported dust masses are seen at heights of about 2 km over the YRD region with an SSA440 nm below 0.84, which heat air and raise the PBL, accelerating the diffusion of dust particles. Regional transport from biomass-burning spots to the south of the YRD region bring mixed aerosol particles at a height below 1.5 km, resulting in an SSA440 nm below 0.89. During the winter, the accumulation of the local emission layer is facilitated by stable weather conditions, staying within the PBL even below 0.5 km.

scholarly journals INVESTIGATING ALOFT AEROSOLS OVER CENTRAL-EASTERN CHINA USING CALIPSO MEASUREMENTS

2018 ◽  
Vol XLII-3/W5 ◽  
pp. 83-88
Author(s):  
J. Zou ◽  
K. Qin ◽  
J. Xu ◽  
X. Han
Keyword(s):  
North China ◽  
Rapid Development ◽  
Eastern China ◽  
Yangtze River Delta ◽  
Anthropogenic Source ◽  
Anthropogenic Aerosols ◽  
The North ◽  
Haze Pollution ◽  
Central Eastern ◽  
The Yrd

<p><strong>Abstract.</strong> The rapid development of China in the last decade has brought about serious environmental problems, among which the air quality has attracted much attention. Especially in the winter, haze events with PM<sub>2.5</sub> as the primary pollutant frequently occur, which has a huge strike on people's health. Such cumulative anthropogenic aerosols at surface over haze pollution regions could be lifted upwards by vertical turbulent mixing forming elevated haze layers that subsequent transport to distant regions. This paper attempts to analyze layer top altitude, ratio of anthropogenic source and optical properties by counting events occurring in aloft aerosols layer. CALIPSO satellite instruments are used for statistical analysis by screening layer data over central-eastern China from 2007 to 2016. In the most economically active and polluted areas of China, the North China Plain (NCP) and the Yangtze River Delta (YRD) are compared to analyze trend variations over ten years. Results shows that the frequency of occurrence of aloft layer in South China are higher than in North China, indicating that heat has a strong lifting effect on the planetary boundary layer (PBL). Further, the NCP has a unique high frequency value at 2.5<span class="thinspace"></span>km, while the YRD has two peaks, 3.5<span class="thinspace"></span>km and 2 km respectively. Moreover, in the past five years in the NCP (2011&amp;ndash;2016) and YRD (2012&amp;ndash;2016) regions, the anthropogenic source of pollutants dominated by smoke showed a downward trend year by year. In addition, monthly proportion of smoke and polluted dust are analyzed in NCP and YRD winter. Finally, the volume depolarization ratio is almost distributed within 0.2, indicating that the shape of the particles is irregular. The particulate color ratio has a sharp peak near 0.4&amp;ndash;0.7 suggesting that smaller particles dominate the size distribution during the winter months.</p>

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