American Association for Aerosol Research - Abstract Submission

AAAR 39th Annual Conference
October 18 - October 22, 2021

Virtual Conference

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The Determination of Source-separated Black Carbon Emission Rates Using Radon as a Tracer of Atmospheric Dynamics

ASTA GREGORIČ, Luka Drinovec, Janja Vaupotič, Irena Jezek, Matic Ivančič, Janja Tursic, Griša Močnik, Aerosol d.o.o.

     Abstract Number: 304
     Working Group: Carbonaceous Aerosol

Abstract
Black carbon (BC) is known as a good indicator of primary emissions. However, atmospheric conditions play an important role in the magnitude and time evolution of ambient BC concentrations, which makes it difficult to reliably quantify the intensity of sources.

We present a new method for the determination of the source-specific black carbon emission rates. The methodology was applied in two different environments: an urban location in Ljubljana and a rural one in the Vipava valley (Slovenia, Europe). The atmospheric dynamics was quantified using the atmospheric radon (222Rn) concentration to determine the mixing layer height (MLH) for periods of thermally driven planetary boundary layer evolution. The BC emission rate was determined using an improved box model taking into account MLH and a horizontal advection term, describing the temporal and spatial exponential decay of BC concentration. The rural Vipava valley is impacted by a significantly higher contribution to black carbon concentration from biomass burning during winter (60 %) in comparison to Ljubljana (27 %). Daily averaged black carbon emission rates in Ljubljana were 210 ± 110 and 260 ± 110 µgm−2h−1 in spring and winter 2016/17, respectively. Overall BC emission rates in Vipava valley were only slightly lower compared to Ljubljana: 150 ± 60 and 250 ± 160  µgm−2h−1 in spring and winter, respectively. The yearly trend of BC emission rates, including the CoViD-19 lockdown period, for Ljubljana location will be presented.

Coupling the high-time-resolution measurements of BC concentration with atmospheric radon concentration measurements can provide a useful tool for direct, highly time-resolved measurements of the intensity of emission sources. Source-specific emission rates can be used to assess the efficiency of pollution mitigation measures over longer time periods, thereby avoiding the influence of variable meteorology.