Ozonolysis of a-phellandrene - Part 2 : Compositional analysis of secondary organic aerosol highlights the role of stabilized Criegee intermediates

The molecular composition of secondary organic aerosol (SOA) generated from the ozonolysis of α-phellandrene is investigated for the first time using high pressure liquid chromatography coupled to high-resolution Quadrupole-Orbitrap tandem mass spectrometry. In total, 21 prominent products or isomeric product groups were identified using both positive and negative ionisation modes, with potential formation mechanisms discussed. The aerosol was found to be composed primarily of polyfunctional first- and second-generation species containing one or more carbonyl, acid, alcohol and hydroperoxide functionalities, with the products significantly more complex than those proposed from basic gas-phase chemistry in the companion paper (Mackenzie-Rae et al., 2017a). Mass spectra show a large number of dimeric products are also formed. Both direct scavenging evidence using formic acid, and indirect evidence from double bond equivalency factors, suggests the dominant oligomerisation mechanism is the bimolecular reaction of stabilised Criegee intermediates (SCIs) with non-radical ozonolysis products. Saturation vapour concentration estimates suggest monomeric species cannot explain the rapid nucleation burst of fresh aerosol observed in chamber experiments, hence dimeric species are believed to be responsible for new particle formation, with detected first- and second-generation products driving further particle growth in the system. Ultimately, identification of the major constituents and formation pathways of α-phellandrene SOA leads to a greater understanding of the atmospheric processes and implications of monoterpene emissions and SCIs, especially around Eucalypt forests regions where α-phellandrene is primarily emitted

Mycoplasma pneumoniae infections, 11 countries in Europe and Israel, 2011 to 2016

Background: Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia, with large epidemics previously described to occur every 4 to 7 years. Aim: To better understand the diagnostic methods used to detect M. pneumoniae; to better understand M. pneumoniae testing and surveillance in use; to identify epidemics; to determine detection number per age group, age demographics for positive detections, concurrence of epidemics and annual peaks across geographical areas; and to determine the effect of geographical location on the timing of epidemics. Methods: A questionnaire was sent in May 2016 to Mycoplasma experts with national or regional responsibility within the ESCMID Study Group for Mycoplasma and Chlamydia Infections in 17 countries across Europe and Israel, retrospectively requesting details on M. pneumoniae-positive samples from January 2011 to April 2016. The Moving Epidemic Method was used to determine epidemic periods and effect of country latitude across the countries for the five periods under investigation. Results: Representatives from 12 countries provided data on M. pneumoniae infections, accounting for 95,666 positive samples. Two laboratories initiated routine macrolide resistance testing since 2013. Between 2011 and 2016, three epidemics were identified: 2011/12, 2014/15 and 2015/16. The distribution of patient ages for M. pneumoniae-positive samples showed three patterns. During epidemic years, an association between country latitude and calendar week when epidemic periods began was noted. Conclusions: An association between epidemics and latitude was observed. Differences were noted in the age distribution of positive cases and detection methods used and practice. A lack of macrolide resistance monitoring was noted

Computational investigation into the gas-phase ozonolysis of the conjugated monoterpene α-phellandrene

Reaction with ozone is a major atmospheric sink for α-phellandrene, a monoterpene found in both indoor and outdoor environments, however experimental literature concerning the reaction is scarce. In this study, high-level G4(MP2) quantum chemical calculations are used to theoretically characterise the reaction of ozone with both double bonds in α-phellandrene for the first time. Results show that addition of ozone to the least substituted double bond in the conjugated system is preferred. Following addition, thermal and chemically activated unimolecular reactions, including the so-called hydro-peroxide and ester or 'hot' acid channels, and internal cyclisation reactions, are characterised to major first generation products. Conjugation present in α-phellandrene allows two favourable Criegee intermediate reaction pathways to proceed that have not previously been considered in the literature; namely a 1,6-allyl resonance stabilised hydrogen shift and intramolecular dioxirane isomerisation to an epoxide. These channels are expected to play an important role alongside conventional routes in the ozonolysis of a-phellandrene. Computational characterisation of the potential energy surface thus provides insight into this previously unstudied system, and will aid future mechanism development and experimental interpretation involving α-phellandrene and structurally similar species, to which the results are expected to extend