An optimized tracer-based approach for estimating organic carbon emissions from biomass burning in Ulaanbaatar, Mongolia

Jayant Nirmalkar,Jinsang Jung,Tsatsral Batmunkh

doi:10.5194/acp-20-3231-2020

Abstract

Abstract. The impact of biomass burning (BB) on atmospheric particulate matter of <2.5 µm diameter (PM2.5) at Ulaanbaatar, Mongolia, was investigated using an optimized tracer-based approach during winter and spring 2017. Integrated 24 h PM2.5 samples were collected on quartz-fiber filters using a 30 L min−1 air sampler at an urban site in Ulaanbaatar. The aerosol samples were analyzed for organic carbon (OC) and elemental carbon (EC), anhydrosugars (levoglucosan, mannosan, and galactosan), and water-soluble ions. OC was found to be the predominant species, contributing 64 % and 56 % to the quantified aerosol components in PM2.5 in winter and spring, respectively. BB was identified as a major source of PM2.5, followed by dust and secondary aerosols. Levoglucosan ∕ mannosan and levoglucosan ∕ K+ ratios indicate that BB in Ulaanbaatar mainly originated from the burning of softwood. Because of the large uncertainty associated with the quantitative estimation of OC emitted from BB (OCBB), a novel approach was developed to optimize the OC ∕ levoglucosan ratio for estimating OCBB. The optimum OC ∕ levoglucosan ratio in Ulaanbaatar was obtained by regression analysis between OCnon-BB (OCtotal–OCBB) and levoglucosan concentrations that gives the lowest coefficient of determination (R2) and slope. The optimum OC ∕ levoglucosan ratio was found to be 27.6 and 18.0 for winter and spring, respectively, and these values were applied in quantifying OCBB. It was found that 68 % and 63 % of the OC were emitted from BB during winter and spring, respectively. This novel approach can also be applied by other researchers to quantify OCBB using their own chemical measurements. In addition to OCBB, sources of OCnon-BB were also investigated through multivariate correlation analysis. It was found that OCnon-BB originated mainly from coal burning, vehicles, and vegetative emissions.

Highlights

Organic aerosol (OA) contributes a significant fraction (10 %–90 %) of atmospheric particulate matter (PM), which can affect human health and air quality (Jimenez et al, 2009; Maenhaut et al, 2011; Fu et al, 2012; Allan et al, 2014; Chen et al, 2018)
biomass burning (BB) was identified as a major source of the quantified aerosol components in PM2.5 in Ulaanbaatar, Mongolia, during the winter and spring of 2017 based on principal component analysis (PCA)
For the determination of OC emitted from BB (OCBB), the fuel type must be identified, and levoglucosan / mannosan and levoglucosan / K+ ratios obtained from previous studies and our on-site measurements were used for this purpose

Summary

Introduction

Organic aerosol (OA) contributes a significant fraction (10 %–90 %) of atmospheric particulate matter (PM), which can affect human health and air quality (Jimenez et al, 2009; Maenhaut et al, 2011; Fu et al, 2012; Allan et al, 2014; Chen et al, 2018). Biomass burning (BB) is a major source of organic carbon (OC) in PM2.5 (PM with aerodynamic diameter ≤ 2.5 μm), and it may become more significant in the future as air-quality regulations restrict other anthropogenic emissions (Davy et al, 2011; Allan et al, 2014; Sullivan et al, 2019). Levoglucosan is produced from the pyrolysis of cellulose at temperatures of > 300 ◦C

Methods

Results

Conclusion