Spatial and temporal variation of ambient carbonaceous aerosol in Ireland and strategies for effective monitoring of source contributions

The concentration, size and composition of atmospheric aerosols determines their impact on health and climate. These parameters are highly variable and inherently linked with source, seasonality and geographical location. In this study, a suite of instruments was deployed to quantitatively investigate the properties of ambient carbonaceous aerosol at six unique locations around Ireland. Source apportionment analysis was performed for the identification of dominant sources contributing to the ambient carbonaceous aerosol in each environment. This work serves to highlight the spatial and temporal variability of ambient carbonaceous aerosol in Ireland. Aethalometer data exhibited significant spatial variability of black carbon (BC). The lowest concentrations were recorded at regional background sites, while the highest concentrations were recorded in populous, urban settings. The aethalometer source apportionment model was used to demonstrate spatial variability of contributions from dominant sources. The temporal variability of carbonaceous aerosol was explored through data collected during long-term monitoring campaigns in Dublin and Enniscorthy. Strong seasonal variation in equivalent black carbon (eBC) was evident, particularly in locations strongly influenced by solid fuel burning for residential heating. Furthermore, approximately 40% and 72% of total eBC measured during winter at University College Dublin and Enniscorthy, respectively, was attributed to solid fuel combustion. Strong diurnal trends were observed in each location, however the absolute concentration was seasonally dependent. A pronounced evening peak, attributed to solid fuel combustion emissions, was observed at the majority of sampling sites during the winter months. Urban areas also had a morning peak consistent with rush hour and was attributed to the influence of traffic-related emissions. Novel data collected at several unique environments as part of three individual long-term monitoring campaigns, demonstrated the ubiquitous nature of carbonaceous aerosol, particularly BC, in Ireland and the associated impact on local air quality. Despite the negative implications on human health, air quality and climate, BC is not regulated or routinely monitored in Ireland. This research outlines the potential benefits of establishing an extensive, national BC monitoring network, including the collection of real-time data to inform vital air pollution mitigation policies

Intercomparison and characterization of 23 Aethalometers under laboratory and ambient air conditions: procedures and unit-to-unit variabilities

Aerosolized black carbon is monitored worldwide 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 qualitychecked and ensured conditions to generate data which are reliable and comparable temporally and geographically. In this study, we report the results from the largest characterization and intercomparison of filter-based absorption photometers, the Aethalometer model AE33, belonging to several European monitoring networks. Under controlled laboratory conditions, a total of 23 instruments measured mass concentrations of black carbon from three wellcharacterized aerosol sources: synthetic soot, nigrosin particles, and ambient air from the urban background of Leipzig, Germany. The objective was to investigate the individual performance of the instruments and their comparability; we analyzed the response of the instruments to the different aerosol sources and the impact caused by the use of obsolete filter materials and the application of maintenance activities. Differences in the instrument-to-instrument variabilities from equivalent black carbon (eBC) concentrations reported at 880 nm were determined before maintenance activities (for soot measurements, average deviation from total least square regression was-2.0% and the range-16% to 7 %; for nigrosin measurements, average deviation was 0.4% and the range-15% to 17 %), and after they were carried out (for soot measurements, average deviation was-1.0% and the range-14% to 8 %; for nigrosin measurements, the average deviation was 0.5%and the range-12%to 15 %). The deviations are in most of the cases explained by the type of filter material employed by the instruments, the total particle load on the filter, and the flow calibration. The results of this intercomparison activity show that relatively small unit-to-unit variability of AE33-based particle light absorbing measurements is possible with wellmaintained instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to ensure high quality and comparable black carbon (BC) measurements among international observational networks. © 2021 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License

Intercomparison and characterization of 23 Aethalometers under laboratory and ambient air conditions : procedures and unit-to-unit variabilities

Aerosolized black carbon is monitored worldwide 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 quality-checked and ensured conditions to generate data which are reliable and comparable temporally and geographically. In this study, we report the results from the largest characterization and intercomparison of filter-based absorption photometers, the Aethalometer model AE33, belonging to several European monitoring networks. Under controlled laboratory conditions, a total of 23 instruments measured mass concentrations of black carbon from three well-characterized aerosol sources: synthetic soot, nigrosin particles, and ambient air from the urban background of Leipzig, Germany. The objective was to investigate the individual performance of the instruments and their comparability; we analyzed the response of the instruments to the different aerosol sources and the impact caused by the use of obsolete filter materials and the application of maintenance activities. Differences in the instrument-to-instrument variabilities from equivalent black carbon (eBC) concentrations reported at 880 nm were determined before maintenance activities (for soot measurements, average deviation from total least square regression was -2.0% and the range -16% to 7 %; for nigrosin measurements, average deviation was 0.4% and the range -15% to 17 %), and after they were carried out (for soot measurements, average deviation was 1:0% and the range -14% to 8 %; for nigrosin measurements, the average deviation was 0.5% and the range -12% to 15 %). The deviations are in most of the cases explained by the type of filter material employed by the instruments, the total particle load on the filter, and the flow calibration. The results of this intercomparison activity show that relatively small unit-to-unit variability of AE33-based particle light absorbing measurements is possible with well-maintained instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to ensure high quality and comparable black carbon (BC) measurements among international observational networks.Peer reviewe

The impact of traffic on air quality in Ireland: insights from the simultaneous kerbside and suburban monitoring of submicron aerosols

To evaluate the impact of traffic on urban air quality, the chemical composition of submicron aerosols (PM1) and sources of organic aerosol (OA) were simultaneously investigated at a kerbside site in the Dublin city center and a residential site in suburban Dublin (similar to 5 km apart) from 4 September to 9 November in 2018. Through the detailed comparison of a 1-week nonheating period from 10 to 17 September and a 1-week heating period from 27 October to 4 November, black carbon (BC) was found to be the most dominant component (38%-55% or 5.6-7.1 mu gm(-3)) of PM1 at the kerbside, while OA was the most important (46%-64% of PM1 or 1.0-8.1 mu g m(-3)) at the residential site. The daily and weekly cycle of BC at the kerbside during the nonheating 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 and the effects of wind speed and wind direction. As a result of vehicular emissions and the street canyon effect, the kerbside increment (from the urban background) ratio of up to 25 : 1 was found for BC during the nonheating 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 16%-28% (0.9-1.0 mu g m(-3); upper limit for traffic due to the additional heating source of hydrocarbon-like OA - HOA) of OA at the kerbside associated with vehicular emissions, with higher contributions from cooking (18 %-36% or 1.2 mu g m(-3)), solid fuel burning (38% or 2.4 mu g m(-3); resolved only during the heating period), and oxygenated OA (29 %-37% or 1.2-1.9 mu g m(-3)). At the residential site, solid fuel burning contributed to 60% (4.9 mu g m(-3)) of OA during the heating period, while oxygenated OA (OOA) accounted for almost 65% (0.6 mu g m(-3)) of OA during the nonheating period. Based on simultaneous investigations of PM1 at different urban settings (i.e., residential versus kerbside), this study highlights the temporal and spatial variability of sources within the Dublin city center and the need for additional aerosol characterization 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

Entomological assessment of hessian fabric transfluthrin vapour emanators for protecting against outdoor-biting Aedes aegypti in coastal Tanzania

Background: A low technology emanator device for slowly releasing vapour of the volatile pyrethroid transfluthrin was recently developed in Tanzania that provides robust protection against night biting Anopheles and Culex vectors of malaria and filariasis for several months. Here these same emanator devices were assessed in Dar es Salaam city, as a means of protection against outdoor-biting Aedes (Stegomia) aegypti, the most important vector of human arboviruses worldwide, in parallel with similar studies in Haiti and Brazil. Methods: A series of entomological experiments were conducted under field and semi-field conditions, to evaluate whether transfluthrin emanators protect against wild Ae. aegypti, and also compare the transfluthrin responsiveness of Ae. aegypti originating from wild-caught eggs to established pyrethroid-susceptible Ae. aegypti and Anopheles gambiae colonies. Preliminary measurements of transfluthrin vapour concentration in air samples collected near treated emanators were conducted by gas chromatography-mass spectrometry. Results: Two full field experiments with four different emanator designs and three different transfluthrin formulations consistently indicated negligible reduction of human landing rates by wild Ae. aegypti. Under semi-field conditions in large cages, 50 to 60% reductions of landing rates were observed, regardless of which transfluthrin dose, capture method, emanator placement position, or source of mosquitoes (mildly pyrethroid resistant wild caught Ae. aegypti or pyrethroid-susceptible colonies of Ae. aegypti and An. gambiae) was used. Air samples collected immediately downwind from an emanator treated with the highest transfluthrin dose (15g), contained 12 to 19 μg/m3 transfluthrin vapour. Conclusions: It appears unlikely that the moderate levels of pyrethroid resistance observed in wild Ae. aegypti can explain the modest-to-undetectable levels of protection exhibited. While potential inhalation exposure could be of concern for the highest (15g) dose evaluated, 3g of transfluthrin appears sufficient to achieve the modest levels of protection that were demonstrated entomologically. While the generally low levels of protection against Aedes reported here from Tanzania, and from similar entomological studies in Haiti and Brazil, are discouraging, complementary social science studies in Haiti and Brazil suggest end-users perceive valuable levels of protection against mosquitoes. It therefore remains unclear whether transfluthrin emanators have potential for protecting against Aedes vectors of important human arboviruses