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Abstract. Primary biological aerosol particles (PBAPs) are ubiquitous in the atmosphere and constitute ∼ 30 % of atmospheric aerosol particle mass in sizes > 1 µm. PBAP components, such as bacteria, fungi and pollen, may affect the climate by acting as cloud-active particles, thus having an effect on cloud and precipitation formation processes. In this study, size-segregated aerosol samples (< 1.0, 1-2.5, 2.5-10 and > 10 µm) were collected in boreal forest (Hyytiälä, Finland) during a 9-month period covering all seasons and analysed for free amino acids (FAAs), DNA concentration and microorganism (bacteria, Pseudomonas and fungi). Measurements were performed using tandem mass spectrometry, spectrophotometry and qPCR, respectively. Meteorological parameters and statistical analysis were used to study their atmospheric implication for results. Distinct annual patterns of PBAP components were observed, late spring and autumn being seasons of dominant occurrence. Elevated abundances of FAAs and bacteria were observed during the local pollen season, whereas fungi were observed at the highest level during autumn. Meteorological parameters such as air and soil temperature, radiation and rainfall were observed to possess a close relationship with PBAP abundances on an annual scale.

Abstract. In this study, a thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) method following sorbent tube sampling was developed for the determination of monoterpenes (MTs), sesquiterpenes (SQTs) and diterpenes (DTs) in gas-phase samples. The analytical figures of merit were determined, and the method performance was tested by conducting experiments related to, for example, sampling recovery, storage stability and ozone reactivity. The limit-of-quantification values were 13–518 pg (0.5–9.3 pptv), intermediate precision was in the range of 3 %–10 % and the expanded measurement uncertainty was in the range of 16 %–55 % for terpenes. The sampling recoveries of terpenes were approximately within 100±20 % with different inlet lines (15 m long Teflon and 1 m long heated stainless steel) and branch enclosure cuvette (6 L Teflon bag) tested. Ozone is an important factor causing losses of the studied compounds during sampling. Therefore, losses of terpenes upon ozone exposure were studied and the reaction rate coefficients were estimated. The ozone reaction rate coefficient (kO3) of ent-kaurene was experimentally estimated to be 2 orders of magnitude greater than the respective literature kO3 value, demonstrating the potential underestimation of DT contribution to atmospheric reactivity. The preliminary comparison between offline- and online-mode TD–GC–MS sampling and analysis revealed that diterpenes and oxygenated sesquiterpenes are lost in excessive amounts in online-mode sampling, hindering the online-mode applicability for the quantitative analysis of these compounds. A few applications to real samples were tested to identify DTs potentially emitted by boreal forest tree species. In dynamic headspace samples of pine needles and spruce twigs heated to 60 ∘C, five DTs and 13 DTs could be detected in emissions, respectively. The semi-quantitatively estimated emission rates of DTs were roughly 1 to 3 orders of magnitude lower than those of MTs and SQTs. Similarly, in spruce branch enclosure emissions from a living tree, six DTs were detected once the enclosure was heated to ca. 60 ∘C. In summary, the developed analytical procedure was demonstrated to be applicable for the analysis of MTs, SQTs and DTs. In addition, DTs could be detected in needles, twigs and branch enclosure emissions; however, high temperatures were required to promote the emissions and for obtaining detectable concentrations.

Abstract. In this study, we present results from 12 years of black carbon (BC) measurements at 14 sites around the Helsinki metropolitan area (HMA) and at one background site outside the HMA. The main local sources of BC in the HMA are traffic and residential wood combustion in fireplaces and sauna stoves. All BC measurements were conducted optically, and therefore we refer to the measured BC as equivalent BC (eBC). Measurement stations were located in different environments that represented traffic environment, detached housing area, urban background, and regional background. The measurements of eBC were conducted from 2007 through 2018; however, the times and the lengths of the time series varied at each site. The largest annual mean eBC concentrations were measured at the traffic sites (from 0.67 to 2.64 µg m−3) and the lowest at the regional background sites (from 0.16 to 0.48 µg m−3). The annual mean eBC concentrations at the detached housing and urban background sites varied from 0.64 to 0.80 µg m−3 and from 0.42 to 0.68 µg m−3, respectively. The clearest seasonal variation was observed at the detached housing sites where residential wood combustion increased the eBC concentrations during the cold season. Diurnal variation in eBC concentration in different urban environments depended clearly on the local sources that were traffic and residential wood combustion. The dependency was not as clear for the typically measured air quality parameters, which were here NOx concentration and mass concentration of particles smaller that 2.5 µm in diameter (PM2.5). At four sites which had at least a 4-year-long time series available, the eBC concentrations had statistically significant decreasing trends that varied from −10.4 % yr−1 to −5.9 % yr−1. Compared to trends determined at urban and regional background sites, the absolute trends decreased fastest at traffic sites, especially during the morning rush hour. Relative long-term trends in eBC and NOx were similar, and their concentrations decreased more rapidly than that of PM2.5. The results indicated that especially emissions from traffic have decreased in the HMA during the last decade. This shows that air pollution control, new emission standards, and a newer fleet of vehicles had an effect on air quality.