Aloft Transport of Haze Aerosols to Xuzhou, Eastern China: Optical Properties, Sources, Type, and Components

Abstract

Rapid industrialization and urbanization have caused frequent haze pollution episodes during winter in eastern China. Considering that the vertical profile of the aerosol properties changes significantly with altitude, investigating aerosol aloft information via satellite remote sensing is essential for studying regional transport, climate radiative effects, and air quality. Through a synergic approach between lidar, the AErosol RObotic NETwork sunphotometer observations, and WRF-Chem simulations, several transboundary aloft transport events of haze aerosols to Xuzhou, eastern China, are investigated in terms of source, type, and composition and the impact on optical properties. Upper-air aerosol layers are short-lived tiny particles that increase the total aerosol optical depth (AOD). The aloft aerosols not only play a critical role during the haze event, enhancing the scattering of aerosol particles significantly but also cause a rise in the AOD and the Ångström exponent (AE), which increases the proportion of fine particles, exacerbating the pollution level near the surface. Based on the model simulation results, our study highlights that the transported aloft aerosols lead to the rapid formation of secondary inorganic substances, such as secondary sulfates, nitrates, and ammonium salts, which strongly contribute to haze event formation. Moreover, the results provide evidence that the haze frequency events associated with polluted dust outbreaks were higher for 2014–2015 winter. A closer analysis shows that the advected dust layers over Xuzhou originated from Inner Mongolia and the Xinjiang Uygur Autonomous Region. The study of the occurrence frequency, height, thickness, and optical properties of aloft anthropogenic haze in China will further deepen our understanding and provide a strong basis to assess aerosol impact on transport and the Earth–atmosphere radiative balance.

Aerosol Vertical Structure and Optical Properties during Two Dust and Haze Episodes in a Typical Valley Basin City, Lanzhou of Northwest China

“…Ref. [16] uncovered that the maximum of σ, VDR, AOD 500 , AE 440-870nm and FMF in Xuzhou were 1.0 km −1 , 0.10 ± 0.01, 0.68 ± 0.26, 1.30 ± 0.12 and 0.81 ± 0.09, respectively, during heavy haze event, which were comparable to the results of this study. From Figure 11, we could see that the mass concentrations of surface six air pollutants and ratio of PM 2.5 /PM 10 increased strikingly from 30 December 2020 to 2 January 2021, and reached a highest value at 13:00 on 2 January, then suddenly decrease since 14:00 on 2 January, which was coincident with the aerosol vertical profiles and variations of spectral AOD behaviors.…”

“…And the maximum σ changed from 0.50 km −1 on 31 December 2020 to 0.60 km −1 on 1 January and 0.68 km −1 on 2 January 2021, whereas the VDR value remained stably at 0.03~0.12 throughout the haze pollution process. This directly demonstrated that the fine-mode and spherical aerosol particles were predominant during the heavy haze period [14,16]. Diverse gaseous precursors emitted by human activities were firmly trapped in PBL under calm and stable thermal inversion layer and hard to spread out, which readily generated different types of aerosol particles through various complex liquid phase chemical reactions or photochemical reactions.…”

“…Sun et al [15] examined the aerosol optical characteristics and vertical distributions under enhanced haze pollution events in Yangtze River Delta region during 2013-2015 by using micro-pulse lidar and sun-photometer observations and elucidated the effect of regional transport of different aerosol types over eastern China. Qin et al [16] investigated several transboundary aloft transport events of haze aerosols to Xuzhou, eastern China, through a synergic approach and highlighted that the transported aloft aerosols led to the rapid formation of secondary inorganic substances, which strongly contributed to haze event formation. Huang et al [17] provided observational evidences on aloft aerosol and planetary boundary layer (PBL) interaction and its impact on pollution aggravation.…”

A Case Study for an Assessment of Fire Station Selection in the Central Urban Area

“…This model can be used to maximize the coverage of demand points when the number of facilities is limited. The collective coverage model and the maximum coverage model consider various factors that influence the layout of fire stations and incorporate constraint conditions [32]. To maximize the coverage of fire stations, Equations ( 4)-( 7) are applied:…”

Characterizing Dust and Biomass Burning Events from Sentinel-2 Imagery

“…Shifting the focus to another major atmospheric issue, dust, primarily from the Sahara, poses a distinct challenge in aerosol monitoring. It significantly impacts air quality, sunlight exposure, and ecosystems [7,13,14]. Sentinel-3, equipped with the Ocean and Land Color Instrument (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR), provides important information for identifying and monitoring dust events.…”