Fossil fuel combustion, biomass burning and biogenic sources of fine carbonaceous aerosol in the Carpathian Basin

Abstract

Abstract. Fine-fraction aerosol samples were collected, and air pollutants and meteorological properties were measured in situ in the regional background environment of the Carpathian Basin, a suburban area and central part of its largest city, Budapest, in each season for a 1-year-long time interval. The samples were analysed for PM2.5 mass, organic carbon (OC), elemental carbon (EC), water-soluble OC (WSOC), radiocarbon, levoglucosan (LVG) and its stereoisomers, and some chemical elements. Carbonaceous aerosol species made up 36 % of the PM2.5 mass, with a modest seasonal variation and with a slightly increasing tendency from the regional background to the city centre (from 32 % to 39 %). A coupled radiocarbon-LVG marker method was applied to apportion the total carbon (TC = OC + EC) into contributions of EC and OC from fossil fuel (FF) combustion (ECFF and OCFF, respectively), EC and OC from biomass burning (BB) (ECBB and OCBB, respectively), and OC from biogenic sources (OCBIO). Fossil fuel combustion showed rather constant daily or monthly mean contributions (of 35 %) to the TC in the whole year in all atmospheric environments, while the daily contributions of BB and biogenic sources changed radically (from <2 % up to 70 %–85 %) at all locations and over the years. In October, the three major sources contributed equally to the TC in all environments. In January, it was the BB that was the major source, with a share of 70 % at all sites. The contributions from biogenic sources in January were the smallest. In April, FF combustion and biogenic sources were the largest two contributors at all locations with typical shares of 45 %–50 % each. In July, biogenic sources became the major source type with a monotonically increasing tendency (from 56 % to 72 %) from the city centre to the regional background. The share of BB was hardly quantifiable in July. The ECFF made up more than 90 % of EC in April and July, while in October and January, the contributions of ECBB were considerable. Biomass burning in winter and autumn offers the largest and most considerable potential for improving the air quality in cities as well as in rural areas of the Carpathian Basin.

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“…The trends, i.e. the smoothed curves over the 7 months, are in line with the distributions of the monthly median concentrations of the species at identical locations determined for several years (Salma et al, 2020b).…”

“…The latter process occurs as a daily phenomenon with a typical shape of its monthly occurrence frequency (Salma and Németh, 2019). This distribution changes in Budapest from year to year without any tendentious character (Salma et al, 2020b). Particles with a diameter from 25 to 100 nm (N 25-100 ) in cities are mainly emitted by incomplete combustion or consist of grown new particles by condensation, while the size fraction with a diameter from 100 to 1000 nm (N 100-1000 ) expresses physically and chemically aged particles; thus, they represent larger spatial extents (Salma et al, 2014;Mikkonen et al, 2020).…”

“…The higher O 3 concentration could partly be associated with the lower concentrations of NO. Ozone exhibits a strong seasonal dependency (Salma et al, 2020b). Lower concen- Figure 7.…”

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“…Thus, it can be regarded as an urban background site. The local sources comprise residential and household emissions including seasonal heating, exhaust of vehicle traffic and some industrial sources (Salma et al, 2017(Salma et al, , 2020a(Salma et al, , 2020b. Long-range transport of air masses can also play a role in shorter time intervals.…”

“…and N6-25 was significant (0.875) during the measurement year. The latter size fraction mainly contains freshly emitted particles from road vehicles in most of the time (Salma et al, 2017), which typically exhibit low hygroscopicity (Burkart et al, 2011;Rose et al, 2011;Enroth et al, 2018 former ratio was substantially lower (WSOC/OC ratios from 20 to 39 %), while the latter ratio was considerably larger (EC/OC ratios from 14-20%) in comparison with the aerosol that was already chemically aged or at regional or remote areas (Salma et al, 2007(Salma et al, , 2020a and references therein). All this implies that the average N30-1000,>70%/NCCN,1.0% ratio has to be extended or even preceded by the slope of the regression line and R of the two data sets as suggestive metrics for quality assurance.…”