Sources and atmospheric processing of size segregated aerosol particles revealed by stable carbon isotope ratios and chemical speciation

Abstract

Size-segregated aerosol particles were collected during winter sampling campaigns at a coastal (55°37' N, 21°03'E) and an urban (54°64' N, 25°18' E) site. Organic compounds were thermally desorbed from the samples at different temperature steps ranging from 100 °C to 350 °C. The organic matter (OM) desorbed at each temperature step is analysed for stable carbon isotopes using an isotope ratio mass spectrometer (IRMS) and for individual organic compounds using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-MS). The OM desorbed at temperatures <200 °C was classified as less refractory carbon and the OM desorbed at temperatures between 200 °C and 350 °C was classified as more refractory carbon. At the coastal site, we identified two distinct time periods. The first period was more frequently influenced by marine air masses than the second time period, which was characterized by Easterly wind directions and continental air masses. During the first period OM contained a large fraction of hydrocarbons and had a carbon isotopic signature typical of liquid fossil fuels in the region. Organic mass spectra provide strong evidence that shipping emissions are a significant source of OM at this coastal site. The isotopic and chemical composition of OM during the second period at the coastal site was similar to the composition at the urban site. There was a clear distinction in source contribution between the less refractory OM and the more refractory OM at these sites. According to the source apportionment method used in this study, we were able to identify fossil fuel burning as predominant source of the less refractory OM in the smallest particles (D < 0.18 μm), and biomass burning as predominant source of the more refractory OM in the larger size range (0.32 < D < 1 μm).

Stable carbon and nitrogen isotope ratio in PM1 and size segregated aerosol particles over the Baltic Sea

“…δ 13 C-TC of PM 1 varied from -27.5 to -26.2‰ with an average of -26.8±0.5‰. The mean δ 13 C observed over the Baltic Sea is comparable to that determined in several urban and anthropogenically influenced locations in Europe [16,17,42,43]. The minimum δ 13 C value (-27.5±0.2‰) was observed on 11-12 November (F2) when the lowest TC concentration and the western outflow was prevailing (Fig.…”

“…The stable carbon isotope ratio (δ 13 C) of carbonaceous aerosol was used in a number of studies to identify and apportion main pollution sources [12][13][14][15][16][17][18]. The stable carbon isotope ratio was also used to quantify aerosol particles of marine origin [19,20].…”

High contributions of fossil sources to more volatile organic aerosol

“…In some recent studies, a thermal desorption approach has been used for analysis of filter samples at lower and higher temperatures as an indicator of volatility (Holzinger et al, 2013;Lopez-Hilfiker et al, 2014Timkovsky et al, 2015;Masalaite et al, 2017Masalaite et al, , 2018. Even though the desorption temperature is not a direct measure of the particle volatility, OC desorbed from the filter at lower temperature tends to be more volatile, whereas the less volatile (i.e., more refractory) OC tends to be desorbed at higher temperatures.…”

“…The relative contributions from fossil and nonfossil sources to OC can be dependent on the volatility. For example, recent studies during winter in Lithuania have shown that vehicular sources are associated with OC fractions desorbed at lower temper-atures, while biomass burning (as a nonfossil source) contributes more strongly to less volatile OC fractions desorbed at higher temperatures (Masalaite et al, 2017(Masalaite et al, , 2018.…”

Chemical characterization and source apportionment of size-segregated aerosol in the port-city of Venice (Italy)

“…The relative contribution of the fifth factor (7%) was higher to that previously reported for shipping emissions to PM 1 (Figure S11), suggesting finally a mixed source of shipping plus industrial emission. This factor was extracted only in the fine-nano particle run, that is coherent to the fact that fossil fuel combustion dominated the production of aerosol in the fine mode (Masalaite et al, 2018). PMF selected solutions showed some mixed sources, probably due to the variability of the datasets, constituted of aerosol of twelve different size ranges.…”