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Airborne black carbon particles are monitored in many networks to quantify its impact on air quality and climate. Given its importance, measurements of black carbon mass concentrations must be conducted with instruments operating in a quality checked and assured conditions to generate reliable and comparable data. According to WMO (World Meteorological Organization) and GAW (Global Atmosphere Watch), intercomparisons against a reference instrument are a crucial part of quality controls in measurement activities (WMO, 2016). The WMO-GAW World Calibration Centre for Aerosol Physics (WCCAP) carried out several instrumental comparison and calibration workshops of absorption photometers in the frame of ACTRIS (European Research Infrastructure for the observation of Aerosol, Clouds and Trace Gases) and the COST Action COLOSSAL (Chemical On-Line cOmpoSition and Source Apportionment of fine aerosoL) in January and June 2019. The experiments were conducted to intercompare filter-based particle light absorption photometers, specifically aethalometers AE33 (Magee Scientific), which are operated by research institutions, universities or governmental entities across Europe. The objective was to investigate the individual performance of 23 instruments and their comparability, using synthetic aerosols in a controlled environment and ambient air from the Leipzig urban background. The methodology and results of the intercomparison are presented in this work. The observed instrument-to-instrument variabilities showed differences that were evaluated, before maintenance activities (average deviation from total least square regression: 1.1%, range: -6% to 16%, for soot measurements; average deviation: 0.3%, range: -14% to 19%, for nigrosin measurements), and after they were carried out (average deviation: 0.4%, range: -8% to 14%, for soot measurements; average deviation: 1.1%, range: -15% to 11%, for nigrosin measurements). The deviations are in most of the cases explained by the filter material, the total particles load on the filter, the performance of the flow systems and previous flow check and calibrations carried out with non-calibrated devices. The results of this intensive intercomparison activity show that relatively small unit-to-unit uncertainties of AE33-based particle light absorbing measurements are possible with functioning instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to assure high quality and comparable BC measurements among international observational networks. [ABSTRACT FROM AUTHOR]

To evaluate the impact of traffic on urban air quality, the chemical composition and sources of submicron aerosols (PM1) were simultaneously investigated at a kerbside site in Dublin city centre and a residential site in sub-urban Dublin (~ 5 km apart) from 4 September to 9 November in 2018. Through the detailed comparison of one-week non-heating period in early September and heating period in late October, black carbon (BC) was found to be the most dominant component (38-55 % or 5.6-7.1 μg m-3) of PM1 at the kerbside while organic aerosol (OA) was the most important (46-63 % of PM1 or 1.0-8.7 μg m-3) at the residential site. The daily and weekly cycle of BC at the kerbside during non-heating period pointed to the major source of vehicular emissions, consistent with that for nitrogen oxides (NOx). However, traffic emissions were found to have a minor impact on air quality at the residential site due to its distance from traffic sources, as well as the effects of wind speed and wind direction. As a result of vehicular emissions and the street canyon effect, the kerbside increment (from urban background) ratio of up to 25 : 1 was found for BC during the non-heating period, but reduced to 10 : 1 during the heating period due to the additional sources of solid fuel burning impacting the air quality at both sites simultaneously. OA source analysis shows only 18-27 % (0.9-1.2 μg m-3) of OA at the kerbside associated with vehicular emissions, with higher contributions from cooking (18-36 % or ~ 1.2 μg m-3), solid fuel burning (~ 33 % or ~ 2.1 μg m-3), and oxygenated OA (31-37 % or 1.2-2.0 μg m-3). At the residential site, solid fuel burning contributed to approximately 50 % (2.7 μg m-3) of OA during the heating period, while oxygenated OA accounted for almost 65 % (0.5 μg m-3) of OA during the non-heating period. Based on simultaneous investigation of PM1 at different urban settings (i.e. residential vs kerbside), this study highlights temporal and spatial variability of sources within Dublin city centre and the need for additional aerosol characterisation studies to improve targeted mitigation solutions for greater impact on urban air quality. Moreover, traffic and residential heating may hold different implications for health and climate as indicated by the significant increment of BC at the kerbside and the large geographic impact of OA from residential heating at both the kerbside and residential sites. [ABSTRACT FROM AUTHOR]

A sensitive analytical method has been developed and validated for the determination of 16 polyfluorinated alkyl substances (PFAS) in fine airborne particulate matter (PM 2.5 ) using on-line solid phase extraction (SPE) coupled with liquid chromatography (LC) - negative electrospray ionisation high resolution mass spectrometry (-) ESI-HRMS. On-line SPE allows simultaneous sample clean-up from interfering matrices and lower limits of detection (LODs) by injecting a large volume of sample into the LC system without compromising chromatographic efficiency and resolution. The method provides LODs in the range 0.08-0.5 pg/mL of sample extract allowing detection of selected PFAS in aerosol particles at low fg/m 3 level and showed good tolerance to the considered PM matrix. The validated method was applied for analysis of PFAS in ambient PM 2.5 samples collected at two urban locations in Ireland, i.e., Enniscorthy and Dublin. Several PFAS were observed above the detection limit, including perfluorobutyrate (PFBA), perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (L-PFBS) and perfluorononanoic acid (PFNA), as well as fluorotelomer sulfonates: 4:2 FTS, 6:2 FTS and 8:2 FTS. The results indicate that some toxic PFAS, such as PFOS and PFOA, are still detected in the environment despite being phased out from production and subject to restricted use in the EU and USA for more than two decades. Observation of fluorotelomer sulfonates (4:2 FTS, 6:2 FTS and 8:2 FTS, which are used as alternatives for legacy PFOA and PFOS) in ambient PM 2.5 samples raises a concern about their persistence in the atmosphere and impact on human health considering emerging evidence that they could have similar health endpoints as PFOA and PFOS. To our knowledge, this is the first study to identify PFAS in ambient PM 2.5 at urban locations in Ireland and also the first study to detect 4:2 and 8:2 fluorotelomer sulfonates in atmospheric aerosol particles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)