Characterisation of the Manchester Aerosol Chamber facility

Shao, Yunqi; Wang, Yu; Du, Mao; Voliotis, Aristeidis; Alfarra, M. R.; Turner, Susan; McFiggans, G.

doi:10.5194/amt-2021-147

Cited by 8 publications

(4 citation statements)

References 74 publications

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“…A detailed description on characterisation of MAC facility (e.g. controlling condition stability, gas/particle wall loss, auxiliary mechanism, aerosol formation capability) can be found in Shao et al (2021). Briefly, MAC consists of an 18 m 3 FEP Teflon bag supported by movable aluminium frames and runs as a batch reactor.…”

Section: Experiments Designmentioning

confidence: 99%

On the evolution of sub- and super-saturated water uptake of secondary organic aerosol in chamber experiments from mixed precursors

Wang

Voliotis

et al. 2021

Preprint

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Abstract. To better understand the chemical controls of sub- and super-saturated aerosol water uptake, we designed and conducted a series of chamber experiments to investigate the evolution of aerosol physicochemical properties during SOA formation from the photochemistry of single or mixed biogenic (α-pinene, isoprene) and anthropogenic (o-cresol) volatile organic compounds (VOCs) in the presence of ammonium sulphate seeds. During the six-hour experiments, the cloud condensation nuclei (CCN) activity at super-saturation of water (0.1 ~ 0.5 %), hygroscopic growth factor at 90 % RH, and non-refractory PM1 chemical composition were recorded concurrently. The hygroscopicity parameter κ was used to represent water uptake ability below and above water saturation, and the κ-Kӧhler approach was implemented to predict the CCN activity from the sub-saturated hygroscopicity. The sub- and super-saturated water uptake (in terms of κHTDMA and κCCN) were mainly controlled by the SOA mass fraction which depended on the SOA production rate of the precursors, and the SOA composition played a second-order role. For the reconciliation of κHTDMA and κCCN, the κHTDMA / κCCN ratio increased with the SOA mass fraction and this was observed in all investigated single and mixed VOC systems, independent of initial VOC concentrations and sources. For all VOC systems, the mean κHTDMA of aerosol particles was ~ 25 % lower than the κCCN at the beginning of the experiments with inorganic seeds. With the increase of condensed SOA on seed particles throughout the experiments, the discrepancy of κHTDMA and κCCN became weaker (down to ~ 0 %) and finally the mean κHTDMA was ~ 60 % higher than κCCN on average when the SOA mass fraction approached ~ 0.8. This is possibly attributable to the non-ideality of solutes at different RH or the different co-condensation of condensable organic vapours within the two instruments. As a result, the predicted CCN number concentrations from the κHTDMA and particle number size distribution were ~ 10 % lower than CCN counter measurement on average at the beginning, and further even turned to an overestimation of ~ 20 % on average when the SOA mass fraction was ~ 0.8. This chemical composition-dependent performances of κ-Kӧhler approach on CCN prediction can introduce a variable uncertainty in predicting cloud droplet numbers from the sub-saturated water uptake.

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Section: Experiments Designmentioning

confidence: 99%

On the evolution of sub- and super-saturated water uptake of secondary organic aerosol in chamber experiments from mixed precursors

Wang

Voliotis

et al. 2021

Preprint

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“…Since α-pinene frequently dominates the mass owing to its high yield, this may offset any o-cresol-derived high f44 in systems containing both α-pinene and o-cresol. Clearly a less coarse diagnostic of composition is required to interrogate the reasons for the observed differences, though Shao et al (2021a) spectra. First, there is an evident increase in the contribution of higher mass ions with time in the α-pinene single VOC system that is not observed in either the o-cresol single VOC system or their binary mixture.…”

Section: Chemical Compositionmentioning

confidence: 99%

Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds

Voliotis

Wang

et al. 2022

Preprint

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Abstract. A comprehensive investigation of the photochemical secondary organic aerosol (SOA) formation and transformation in mixtures of anthropogenic (o-cresol) and biogenic (α-pinene and isoprene) volatile organic compound (VOC) precursors in the presence of NOx and inorganic seed particles was conducted. Initial iso-reactivity was used to enable direct comparison across systems, adjusting the initial reactivity of the systems towards the assumed dominant oxidant (OH). Comparing experiments conducted in single precursor systems at various initial reactivity levels (referenced to a nominal base case VOC reactivity) and their binary and ternary mixtures, we show that the molecular interactions from the mixing of the precursors can be investigated and discuss limitations in their interpretation. The observed average SOA yields in descending order were found for the α-pinene (32 ± 7 %), α-pinene/o-cresol (28 ± 9 %), α-pinene at ½ initial reactivity (21 ± 5 %), α-pinene/isoprene (16 ± 1 %), α-pinene at ⅓ initial reactivity (15 ± 4 %), o-cresol (13 ± 3 %), α-pinene/o-cresol/isoprene (11 ± 4%), o-cresol at ½ initial reactivity (11 ± 3 %), o-cresol/isoprene (6 ± 2 %) and isoprene systems (0 ± 0 %). We find a clear suppression of the SOA yield from α-pinene when it is mixed with isoprene, whilst the addition of isoprene to o-cresol may enhance the mixture’s SOA formation potential, however, the difference was too small to be unequivocal. The α-pinene/o-cresol system yield appeared to be increased compared to that calculated based on the additivity, whilst in the α-pinene/o-cresol/isoprene system the measured and predicted yield were comparable. However, in mixtures where more than one precursor contributes to the SOA mass it is unclear whether changes in the SOA formation potential are attributable to physical or chemical interactions, since the reference basis for the comparison is complex. Online and offline chemical composition and SOA particle volatility, water uptake and “phase” behaviour measurements that were used to interpret the SOA formation and behaviour are introduced and detailed elsewhere.

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“…The Manchester Aerosol Chamber (MAC) is a purpose-built chamber comprising an 18m 3 FEP Teflon bag in an air-conditioned enclosure and a high-volume clean air filling system incorporating a series of trace gas and particulate scrubbers. See Shao et al (2021) [75] for details Control of pollutant concentrations was maintained through timed injection of the engine exhaust and the clean air, ensuring similar chemical composition between participants. Cycling between air mix conditions was facilitated by full computer control and monitoring of all necessary chamber conditions.…”

Section: Atmospheric Chambermentioning

confidence: 99%

Acute Diesel Exhaust Exposure Causes a Delayed Reduction in Cognitive Control

Faherty

Delgado-Saborit

Alfarra

et al. 2021

Preprint

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Urban residents are frequently exposed to high levels of traffic-derived air pollution for short time periods, often (but not exclusively) during commuting. Although chronic air pollution exposure and health effects, including neurological effects on children and older adults, are known to be correlated, causal effects of acute pollution exposure on brain function in healthy young adults remain sparsely investigated. Neuroinflammatory accounts suggest effects could be delayed by several hours and could affect attention, especially in social contexts. Using a controlled atmosphere chamber, we exposed 81 healthy young adults to either diluted diesel exhaust (equivalent to polluted roadside environments) or clean air for one hour. Half of each group immediately completed a selective attention task to assess cognitive control; remaining participants completed the task after a 4-hour delay. Cognitive control was significantly poorer after diesel versus clean air exposure for those in the delay but not immediate test condition, suggesting an inflammatory basis for this acute negative effect of air pollution on cognition. These findings provide the first experimental evidence that acute diesel exposure, comparable to polluted city streets, causes a negative effect on cognitive control several hours later. These findings may explain commuter mental fatigue and support clean-air initiatives.

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Characterisation of the Manchester Aerosol Chamber facility

Cited by 8 publications

References 74 publications

On the evolution of sub- and super-saturated water uptake of secondary organic aerosol in chamber experiments from mixed precursors

On the evolution of sub- and super-saturated water uptake of secondary organic aerosol in chamber experiments from mixed precursors

Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds

Acute Diesel Exhaust Exposure Causes a Delayed Reduction in Cognitive Control

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