Intra-regional transport of black carbon between the south edge of North China Plain and Central China during winter haze episodes

Abstract

<p><strong>Abstract.</strong> Black carbon (BC), from the incomplete combustion sources (mainly fossil fuel, biofuel and open biomass burning), is chemically inertness and optical absorbance in the atmosphere. It has significant impacts on global climate, regional air quality, and human health. During the transportation, its physical-chemical characteristics, optical properties and sources would change dramatically. To investigate the BC properties (i.e., mass concentration, sources and optical properties) during the intra-regional transport between the south edge of North China Plain (SE-NCP) and Central China (CC), simultaneous observations of BC at a megacity (Wuhan, WH) in CC, three borderline cities (Xiangyang, XY, Suixian, SX and Hong'an, HA, distributing from the west to east) between SE-NCP and CC and a city (Luohe, LH) in SE-NCP were conducted during the typical winter haze episodes. Using Aethalometer, the highest equivalent BC (eBC) mass concentrations and aerosol absorption coefficients (σ<sub>abs</sub>) were found in the city (LH) at SE-NCP, followed by the borderline cities (XY, SX and HA) and megacity (WH). The levels, sources, optical properties (i.e., σ<sub>abs</sub> and absorption Ångström exponent, AAE) and geographic origins of eBC were different between clean and pollution episodes. Compared to clean days, the higher eBC levels (increased by 26.4–163 %) and σabs (increased by 18.2–236 %) were found during pollution episodes due to more combustion of fossil fuel (contributing for 51.1–277 %), supported by the decreased AAE (by 7.40–12.7 %). Non-parametric wind regression (NWR) and concentration-weighted trajectory (CWT) results showed that the geographic origins of biomass burning (BC<sub><i>bb</i></sub>) and fossil fuel (BC<sub><i>ff</i></sub>) combustion derived BC were different. Based on cluster analysis of trajectories, air parcels from south direction dominated for border sites during clean days, with contributions of 46.0–58.2 %, while trajectories from the northeast had higher contributions (37.5–51.2 %) during pollution episodes. At the SE-NCP site (LH), transboundary influences from south direction (CC) exhibited more frequent impact (with the air parcels from this direction contributed 47.8 % of all the parcels) on the ambient eBC levels during pollution episodes. At WH, eBC was mainly from the northeast transport route during the whole observation period. Two transportation cases showed that from upwind to downwind direction, the mass concentrations of eBC, BC<sub><i>bb</i></sub> and BC<sub><i>ff</i></sub> all increased, while AAE decreased. This study highlighted that intra-regional prevention and control for dominated sources of specific sites should be considered to improve the regional air quality.</p>

Variation in Concentration and Sources of Black Carbon in a Megacity of China During the COVID‐19 Pandemic

“…Harrison et al (2013) reminded that estimates of woodsmoke from Aethalometer data were sensitive to choice of AAE. Here, we applied the optimal combination of AAE ff = 1.0 and AAE bb = 2.0 to quantify BC source apportionment (Sandradewi, Prévôt, Szidat, et al, 2008; Zheng et al, 2019). Figure S8 presents the relative contribution of biomass burning to the total BC ( f bb ) on weekdays.…”

Trans‐Regional Transport of Haze Particles From the North China Plain to Yangtze River Delta During Winter

“…The concentration‐weighted trajectory (CWT) analysis based on backward trajectory can be employed to estimate the contribution of air pollutants from different regions (H. Zheng et al., 2019). Before the CWT analysis, air mass backward trajectory needs to be calculated.…”

“…These haze pollution events profoundly affect human health, such as respiratory system and heart (Lelieveld et al., 2020); climate, such as temperature and precipitation (Suzuki & Takemura, 2019); and ecosystem, such as growth of plankton in remote ocean areas (Li, Xu, et al., 2017). Although the Chinese government has adopted a series of control measures (e.g., the 12th Five‐Year Plan for Air Pollution Control in Key Areas and Air Pollution Prevention and Control Action Plan), some regional haze pollution events still occur in winter owing to adverse meteorological conditions (e.g., low wind speed and high relative humidity (RH)), relatively high emissions from household heating, vehicle exhausts, and industry activities, regional or long‐range transport of air pollutants, and secondary aerosol formation (J. Liu et al., 2016; X. Pan et al., 2019; Shao et al., 2019; Yao et al., 2018; F. Zhang et al., 2020; Zhang, Liu, Xu, et al., 2020; G. J. Zheng et al., 2015; H. Zheng et al., 2019; Zhong et al., 2019).…”

Importance of meteorology in air pollution events during the city lockdown for COVID-19 in Hubei Province, Central China

“…Recently, Hubei has increasingly suffered from haze pollution ( Wang et al, 2014 ; Tan et al, 2015 ; Xu et al, 2017 ; Gao et al, 2019 ). Several studies concerning the air pollution in this region have been conducted ( Zhang et al, 2015 ; Zheng et al, 2019 ; Bai et al, 2020 ). Generally, the changes of air pollutants are highly dependent on their emissions and meteorological conditions ( Tie et al, 2017 ; Xu et al, 2016 ; An et al, 2019 ).…”