Intercomparison of equivalent black carbon (eBC) and elemental carbon (EC) concentrations with three-year continuous measurement in Beijing, China

Xiaomeng Liu; Mei Zheng; Yue Liu; Yali Jin; Junyi Liu; Boya Zhang; Xi Yang; Yazhen Wu; Tianle Zhang; Yaxin Xiang; Baoxian Liu; Caiqing Yan

doi:10.1016/j.envres.2022.112791

Intercomparison of equivalent black carbon (eBC) and elemental carbon (EC) concentrations with three-year continuous measurement in Beijing, China

Environ Res. 2022 Jun:209:112791. doi: 10.1016/j.envres.2022.112791. Epub 2022 Jan 29.

Authors

Xiaomeng Liu¹, Mei Zheng², Yue Liu¹, Yali Jin¹, Junyi Liu¹, Boya Zhang¹, Xi Yang¹, Yazhen Wu¹, Tianle Zhang¹, Yaxin Xiang¹, Baoxian Liu³, Caiqing Yan⁴

Affiliations

¹ State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
² State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China. Electronic address: mzheng@pku.edu.cn.
³ Beijing Key Laboratory of Airborne Particulate Matter Monitoring Technology, Beijing Municipal Environmental Monitoring Center, Beijing, 100048, China.
⁴ Environment Research Institute, Shandong University, Qingdao, 266237, China. Electronic address: cyan0325@sdu.edu.cn.

PMID: 35101394
DOI: 10.1016/j.envres.2022.112791

Abstract

Due to the lack of black carbon (BC) measurement data in some cases, elemental carbon (EC) is often used as a surrogate of BC, with a simple assumption that they are interchangeable. Such assumption will inevitably lead to uncertainties in radiative forcing estimation and health impact assessment. In order to quantitatively and systematically evaluate the relationship between BC and EC as well as factors responsible for their difference, 3-year collocated equivalent BC (eBC) and EC measurements with 1-h resolution were performed in Beijing, China continuously from 2016 to 2019. EBC concentration was measured by the multi-wavelength aethalometer (AE-33) based on optical analysis, while EC concentration was determined by semi-continuous OC/EC analyzer with thermal-optical method. The results showed that around 90% of eBC concentration was higher than that of EC, with average difference between eBC and EC as 1.21 μg m^-3 (accounting for 33% of average eBC in Beijing). EBC and EC concentrations exhibited strong correlation (r = 0.90) during the whole study period, but the slopes (or eBC/EC ratio) and correlation coefficients varied across seasons (spring: 1.67 and 0.94; summer: 0.91 and 0.65; fall: 1.15 and 0.88; winter: 1.09 and 0.91, respectively). Based on the information from shell/core ratios by Single Particle Soot Photometer (SP2), source apportionment results by positive matrix factorization model, and chemical composition of PM_2.5, the differences between eBC and EC concentrations were found to be primarily related to BC aging process and secondary components as evidenced by strong positive correlation with secondary species (e.g., secondary organic carbon and nitrate). This study provided seasonal specific conversion factors of eBC and EC in Beijing and helpful reference for other areas, which will contribute new knowledge of carbonaceous aerosol and reduce uncertainty in assessing future climate change and health studies of BC.

Keywords: BC aging; Black carbon; Elemental carbon; Intercomparison; Secondary species; eBC/EC ratio.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Beijing
Carbon / analysis
China
Environmental Monitoring / methods
Particulate Matter / analysis
Seasons
Soot* / analysis

Substances

Aerosols
Air Pollutants
Particulate Matter
Soot
Carbon