Seasonality of the Airborne Ambient Soot Predominant Emission Sources Determined by Raman Microspectroscopy and Thermo-Optical Method

Natalia Zioła,Krzysztof Klejnowski,Barbara Mathews,Kamila Banasik,Mariola Jabłońska,Janusz Janeczek,Barbara Błaszczak

doi:10.3390/atmos12060768

Natalia Zioła, Krzysztof Klejnowski + Show 5 more

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https://doi.org/10.3390/atmos12060768

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Abstract

Raman microspectroscopy and thermo-optical-transmittance (TOT) method were used to study airborne ambient soot collected at the suburban air monitoring station in southern Poland during the residential heating (January-February) and non-heating (June–July) seasons of 2017. Carbonaceous material constituted on average 47.2 wt.% of PM2.5 during the heating season and 26.9 wt.% in the non-heating season. Average concentrations of OC (37.5 ± 11.0 μg/m3) and EC (5.3 ± 1.1 μg/m3) during the heating season were significantly higher than those in the non-heating season (OC = 2.65 ± 0.78 μg/m3, and EC = 0.39 ± 0.18 μg/m3). OC was a chief contributor to the TC mass concentration regardless of the season. All Raman parameters indicated coal combustion and biomass burning were the predominant sources of soot in the heating season. Diesel soot, which is structurally less ordered than soot from other sources, was dominant during the non-heating season. The D1 and G bands area ratio (D1A/GA) was the most sensitive Raman parameter that discriminated between various soot sources, with D1A/GA > 1 for diesel soot, and less than 1 for soot from coal and wood burning. Due to high daily variability of both TOT and Raman spectroscopy data, single-day measurements can be inconclusive regarding the soot source apportionment. Long-time measurement campaigns are recommended.

Highlights

Carbonaceous matter (CM) is a common and important component of atmospheric aerosols, and accounts for 20–50% of the total aerosol mass [1]
The mass concentration of PM2.5 collected during the heating season ranged from
Raman parameters can reliably be used for distinguishing between diesel soot and soot from coal and wood combustion in ambient air samples

Summary

Introduction

Carbonaceous matter (CM) is a common and important component of atmospheric aerosols, and accounts for 20–50% of the total aerosol mass [1]. CM consists of primary carbon-rich particles and of both primary and secondary organic compounds [2]. The primary carbon-rich particles are interchangeably called soot, black carbon (BC), or elemental carbon (EC). The term elemental carbon refers to thermally-refractory carbon and should be used only in conjunction with chemical or thermo-optical analyses [3,4,5]. Black carbon is a descriptive term of light-absorbing CM in atmospheric aerosol [6] that should be used only in reference to optical properties of CM. BC is the strongest light absorber per unit mass of all atmospheric aerosol species [7]. BC should not be confused with carbon black, which is an industrial carbon material widely used in numerous applications [8]

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