scholarly journals Black carbon and wavelength-dependent aerosol absorption in the North China Plain based on two-year aethalometer measurements

2016 ◽  
Vol 142 ◽  
pp. 132-144 ◽  
Author(s):  
L. Ran ◽  
Z.Z. Deng ◽  
P.C. Wang ◽  
X.A. Xia
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
The North ◽  
Aerosol Absorption ◽  
The North China Plain

scholarly journals Vertical profiles of black carbon measured by a micro-aethalometer in summer in the North China Plain

2016 ◽  
Vol 16 (16) ◽  
pp. 10441-10454 ◽  
Author(s):  
Liang Ran ◽  
Zhaoze Deng ◽  
Xiaobin Xu ◽  
Peng Yan ◽  
Weili Lin ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Ground Level ◽  
Early Morning ◽  
Vertical Profiles ◽  
Large Variability ◽  
Field Campaign ◽  
The North ◽  
The North China Plain

Abstract. Black carbon (BC) is a dominant absorber in the visible spectrum and a potent factor in climatic effects. Vertical profiles of BC were measured using a micro-aethalometer attached to a tethered balloon during the Vertical Observations of trace Gases and Aerosols (VOGA) field campaign, in summer 2014 at a semirural site in the North China Plain (NCP). The diurnal cycle of BC vertical distributions following the evolution of the mixing layer (ML) was investigated for the first time in the NCP region. Statistical parameters including identified mixing height (Hm) and average BC mass concentrations within the ML (Cm) and in the free troposphere (Cf) were obtained for a selected dataset of 67 vertical profiles. Hm was usually lower than 0.2 km in the early morning and rapidly rose thereafter due to strengthened turbulence. The maximum height of the ML was reached in the late afternoon. The top of a full developed ML exceeded 1 km on sunny days in summer, while it stayed much lower on cloudy  days. The sunset triggered the collapse of the ML, and a stable nocturnal boundary layer (NBL) gradually formed. Accordingly, the highest level Cm was found in the early morning and the lowest was found in the afternoon. In the daytime, BC was almost uniformly distributed within the ML and significantly decreased above the ML. During the field campaign, Cm averaged about 5.16 ± 2.49 µg m−3, with a range of 1.12 to 14.49 µg m−3, comparable with observational results in many polluted urban areas such as Milan in Italy and Shanghai in China. As evening approached, BC gradually built up near the surface and exponentially declined with height. In contrast to the large variability found both in Hm and Cm, Cf stayed relatively unaffected through the day. Cf was less than 10 % of the ground level under clean conditions, while it amounted to half of the ground level in some polluted cases. In situ measurements of BC vertical profiles would hopefully have an important implication for accurately estimating direct radiative forcing by BC and improving the retrieval of aerosol optical properties by remote sensing in this region.

Influence of size and mixing state on the wet scavenging of black carbon aerosol in the North China Plain

2020 ◽  
Author(s):  
Xihao Pan ◽  
Nan Ma ◽  
Yaqing Zhou ◽  
Shaowen Zhu ◽  
Long Peng ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Mixing State ◽  
Radiation Fog ◽  
The North ◽  
The North China Plain ◽  
Positive Direct ◽  
Scavenging Efficiency

<p>Black carbon (BC) is the most important light-absorbing species in the atmosphere and has a strong positive direct radiative forcing. In-cloud scavenging is the major way to wash out BC from the atmosphere. Understanding the connection between its physico-chemical properties and scavenging efficiency is therefore a key to evaluate its lifetime, atmospheric burden and spatial distribution. During an intensive field campaign conducted in the North China Plain in 2019, a ground-based counterflow virtual impactor was utilized to separate fog droplets in radiation fog events. BC mass and mixing state of fog droplet residues were online measured with a single particle soot photometer (SP2). In a strong radiation fog event with visibility of about 50 m, more than 20% fog droplets are found to contain a BC core. BC scavenging efficiency is found to be strongly determined by its diameter and mixing state. Driven by different mechanisms, higher scavenging efficiencies up to 10% are observed for larger and smaller BC particles, and the minimum efficiency is found at BC diameter of 120 nm. For large core (>120 nm) BC-containing particles, the scavenging efficiency increases significantly with coating thickness (CT), from about 10% for CT<100 nm to 80% for CT>300 nm. Chemical composition may also be a key parameter influencing the scavenging of BC. Based on the observation of 3 fog events, parameterizations of BC scavenging efficiency are also given in this study.</p>

Mass-based mixing state of black carbon measured by a tandem CPMA-SP2 system in wintertime in the North China Plain

2020 ◽  
Author(s):  
Shaowen Zhu ◽  
Nan Ma ◽  
Xihao Pan ◽  
Wenlin Dong ◽  
Jiangchuan Tao ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Data Retrieval ◽  
Particle Mass ◽  
Radiative Properties ◽  
Mass Analyzer ◽  
Mixing State ◽  
The North ◽  
The North China Plain

<p>Black carbon (BC) is the most important light absorbing component in the atmosphere and has significant impacts on the climate, environment and public health. Its effects depend not only on its spatial-temporal distribution, but also on its physico-chemical characteristics. Mixing state is one of the most important properties of BC and strongly determines its hygroscopicity and radiative properties. During an intensive field campaign conducted in the North China Plain in winter 2018, mass-based mixing state of BC-containing particles were online measured with a Centrifugal Particle Mass Analyzer and Single Particle Soot Photometer (CPMA-SP2) tandem system. This technique directly provides the mass ratio of non-refractory coating matter to BC core (M<sub>R</sub>) in individual particles and does not require to assume the density, morphology and refractive index of BC core and coating in data retrieval, therefore has lower uncertainly compared with leading-edge fit technique. In our measurement, the mean number fraction of uncoated (M<sub>R</sub>=0), thin coated (0<M<sub>R</sub><3) and thick coated (M<sub>R</sub>≥3) BC-containing particle during the campaign were respectively ~10%, ~35% and ~55%, indicating the strong aging process of BC-containing particle in the North China Plain. The median value of M<sub>R</sub> was much higher in polluted days than clean days, for example, the median value of M<sub>R</sub> with a particle mass of 8.56 fg (~220 nm in diameter) for polluted and clean days were ~3.2 and ~1.6, respectively. The mixing state of BC-containing particles obtained by different methods were also compared and evaluated.</p>

scholarly journals Measurement report: Source and mixing state of black carbon aerosol in the North China Plain: implications for radiative effect

2020 ◽  
Vol 20 (23) ◽  
pp. 15427-15442
Author(s):  
Qiyuan Wang ◽  
Li Li ◽  
Jiamao Zhou ◽  
Jianhuai Ye ◽  
Wenting Dai ◽  
...  
Keyword(s):  
Air Quality ◽  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiative Effect ◽  
Mixing State ◽  
The North ◽  
The North China Plain

Abstract. Establishment of the sources and mixing state of black carbon (BC) aerosol is essential for assessing its impact on air quality and climatic effects. A winter campaign (December 2017–January 2018) was performed in the North China Plain (NCP) to evaluate the sources, coating composition, and radiative effects of BC under the background of emission reduction. Results showed that the sources of liquid fossil fuels (i.e., traffic emissions) and solid fuels (i.e., biomass and coal burning) contributed 69 % and 31 % to the total equivalent BC (eBC) mass, respectively. These values were arrived at by using a combination of multi-wavelength optical approach with the source-based aerosol absorption Ångström exponent values. The air quality model indicated that local emissions were the dominant contributors to BC at the measurement site. However, regional emissions from NCP were a critical factor for high BC pollution. A single-particle aerosol mass spectrometer identified six classes of elemental carbon (EC)-containing particles. They included EC coated by organic carbon and sulfate (52 % of total EC-containing particles); EC coated by Na and K (24 %); EC coated by K, sulfate, and nitrate (17 %); EC associated with biomass burning (6 %); pure-EC (1 %); and others (1 %). Different BC sources exhibited distinct impacts on the EC-containing particles. A radiative transfer model showed that the amount of detected eBC can produce an atmospheric direct radiative effect of +18.0 W m−2 and a heating rate of 0.5 K d−1. This study shows that reductions of solid fuel combustion-related BC may be an effective way of mitigating regional warming in the NCP.

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