The determination of highly time-resolved and source-separated black carbon emission rates using radon as a tracer of atmospheric dynamics

Abstract

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.

The impact of temperature inversions on black carbon and particle mass concentrations in a mountainous area

“…An additional control parameter, whether the MH is below or above the Tabor hill, was a comparison between eBC mass concentrations at the Retje station and at the rural background station on the Tabor hill. As shown also in the study of Gregorič et al (2020), higher concentrations in terrain depression than on the top of the hill indicate a MH below the altitude of the hill site.…”

The use of radon as a tracer for air quality assessment: a case study in Bratislava, Slovakia

“…During the daytime the MLH is thermally driven, reaching its maximum of ~ 1350 m in spring and summer, ~ 950 m in autumn and ∼ 650m in winter, respectively. Overall, these results are in good agreement with the typical diurnal cycle of MLH obtained in previous studies employing various methods of MLH retrieval, including the same method that was applied in the present study (e.g., [24,29,37]).…”

“…For the determination of MLH, a box model based on outdoor radon was originally developed by Fontan et al [22]. This model was further improved upon by Sesana et al and Vecchi et al [23,24], and was employed in many other studies [25][26][27][28][29]. The results were found to be in good agreement with those obtained by other, more conventional methods, such as sodar and lidar.…”

PM Dimensional Characterization in an Urban Mediterranean Area: Case Studies on the Separation between Fine and Coarse Atmospheric Aerosol

“…In Figure 2a the temporal trends mass concentrations measured by APS are reported for some size channels in 0.5-3.5 µ m. Figure 2b,c show for the same time interval the temporal trends of radioactivity associated to short lived decay products of radon and of CO an measurement of natural radioactivity represents a useful tool to infer informa dynamic evolution of the PBL mixing height. Furthermore, 222 Rn is a natura radioactive gas from soil ground emitted gas, and for a given geographical regio sion rate is constant in the regional scale of some kilometers [46,47]; it does n…”

“…The measurement of natural radioactivity represents a useful tool to infer information on the dynamic evolution of the PBL mixing height. Furthermore, 222 Rn is a natural occurring radioactive gas from soil ground emitted gas, and for a given geographical region its emission rate is constant in the regional scale of some kilometers [46,47]; it does not undergo any chemical transformation. Therefore, 222 Rn and its short-lived decay products concentrations merely depend on the degree of atmospheric dilution, namely on PBL mixing height and on the presence of advective conditions [48,49].…”