Abstract. 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), which differ in pollution sources
and topography. The atmospheric dynamics was quantified using the
atmospheric radon (222Rn) concentration to determine the mixing layer
height for periods of thermally driven planetary boundary layer evolution.
The black carbon emission rate was determined using an improved box model
taking into account boundary layer depth and a horizontal advection term,
describing the temporal and spatial exponential decay of black carbon
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, respectively. Overall black carbon 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. Different daily dynamics of biomass burning and traffic
emissions was responsible for slightly higher contribution of biomass
burning to measured black carbon concentration, compared to the fraction of
its emission rate. Coupling the high-time-resolution measurements of black
carbon 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.