Potassium: A Tracer for Biomass Burning in Beijing?

Jinting Yu; Caiqing Yan; Yue Liu; Xiaoying Li; Tian Zhou; Mei Zheng

doi:10.4209/aaqr.2017.11.0536

Potassium: A Tracer for Biomass Burning in Beijing?

$(a) Average source contribution, (b) time series of mass concentration of K, and (c) time series of mass fractions of dust, coal combustion and biomass burning to K along with the total PM2.5 concentration across the four seasons. The size of each pie is proportional to the average concentration of K during that season.$

Jinting Yu, Caiqing Yan, Yue Liu, Xiaoying Li, Tian Zhou, Mei Zheng

SKL-ESPC and BIC-ESAT, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China

Received: November 29, 2017
Revised: June 6, 2018
Accepted: June 7, 2018
Download Citation: ||https://doi.org/10.4209/aaqr.2017.11.0536

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Cite this article:
Yu, J., Yan, C., Liu, Y., Li, X., Zhou, T. and Zheng, M. (2018). Potassium: A Tracer for Biomass Burning in Beijing?. Aerosol Air Qual. Res. 18: 2447-2459. https://doi.org/10.4209/aaqr.2017.11.0536

HIGHLIGHTS

Major sources of K in Beijing (coal, biomass burning, and dust) are quantified.
Coal combustion is a major source of K (45–69%) especially during winter haze.
Biomass burning will be overestimated when using K as a sole tracer.

ABSTRACT

Potassium (K) is an important component of fine particulate matter (PM_2.5) and has been widely used as a tracer for biomass burning around the world. However, this may not be true in Beijing, where the sources of K are much more complicated. The aim of this research is to investigate whether K can be applied as a sole tracer for biomass burning in Beijing. From 2015 to 2016, the concentrations of K across the four seasons were measured by an Xact 625 monitor, which uses X-ray fluorescence, and the concentrations of K⁺ during two seasons were measured by an in-situ Gas and Aerosol Composition (IGAC), which uses ion chromatography. It was found that the ratios of K/K⁺ and K⁺/PM_2.5 were close to that of coal combustion, and K exhibited good correlations with trace metals associated with coal combustion (e.g., Pb, As, Se, and Zn). The ratios of K/Pb during the peak of the haze episodes were very stable (around 15.70), suggesting the influence of a major but consistent source. Therefore, it was clear that coal combustion was one of the major sources of K in Beijing. To estimate the major source contributions to K, the ratios of K/Ca and K/Pb were used to represent dust and coal combustion, respectively. From this study, coal combustion was the major source of K (45–69%), followed by biomass burning and dust. However, a seasonality effect was observed, with the highest source contributions coming from coal combustion in winter (69%), biomass burning in autumn (49%), and dust in spring (19%). This research shows that biomass burning would be overestimated in Beijing using K as a sole tracer, since coal is also a major source of the latter.

Keywords: K; Tracer; Source; Biomass burning; Coal combustion.