Dust aerosol is an important atmospheric component due to its ice nucleating ability, which affects cloud phase and precipitation. Arizona Test Dust (ATD) is often used as a proxy for environmental dust aerosol in laboratory studies. In this work, we examine how the ice nucleating behavior of ATD is altered with different solution phase and dry aging processes under several conditions. We find that ATD ice nucleating ability is degraded in significant ways under most conditions, including aging for less than a day in deionized water or NaCl solution. Additional studies are detailed for processing in acidic solutions, salt solutions, peroxide treatment, heat treatment, and protease enzyme treatment. We find evidence of warm-temperature ice nucleating particles that share the analytically characteristic attributes of organic ice nucleators but are heat stable beyond the normal range for organic materials. We hypothesize that this is due to binding and stabilization of organic materials at the mineral surface.

BackgroundTobacco companies are offering cigarettes with ‘concept’ descriptor names that suggest sensation and/or flavour properties (eg, Marlboro ‘Velvet Fusion’). Little has been known about the identities and levels of flavour chemicals in such cigarettes.MethodsThirty-three filter cigarette variants from 27 packs (including two sampler packs with four variations each) from Canada and Mexico were analysed (rod + filter) for 177 flavour chemicals plus triacetin, a filter plasticiser and possible flavourant. Five brands of US mentholated filter cigarettes were also analysed.ResultsTwenty-seven of the 33 cigarettes (all were Mexican variants) were categorised as ‘menthol-plus’: significant menthol (3.0–11.9 mg/cigarette), plus varying amounts (0.32–3.4 mg/cigarette) of total other flavour chemicals (TOFCs) (excludes triacetin). For 10 of the 27, TOFCs >1.0 mg/cigarette. For 7 of the 27, the TOFCs profile was categorised as containing total fruit flavour compounds (TFFCs) >1.0 mg/cigarette. One Mexican variant was categorised as ‘menthol-only’ (TOFCs ≤0.15 mg/cigarette). All menthol-plus and menthol-only cigarettes contained one or two optional-crush capsules in their filters (crushed prior to analysis). All five Canadian brand variants were ‘non-flavoured’. All five US brand variants were ‘menthol-only’.ConclusionsAll but one of the ‘concept’ descriptor cigarettes from Mexico were ‘menthol-plus’. While the Canadian cigarettes complied with Canada’s flavour chemical ban, concept descriptors on the packs may increase appeal. Given the scale of the problem posed by menthol alone, health officials seeking to decrease the appeal of smoked tobacco should examine the extent to which ‘concept descriptor’ cigarettes using ‘menthol-plus’ flavour profiling together with artful descriptors are furthering the problem of smoked tobacco.

In electronic cigarettes (“electronic nicotine delivery systems”, ENDS), mixtures of propylene glycol (PG) and/or glycerol (GL; aka “vegetable glycerin”, VG) with nicotine are vaporized to create a nicotine-containing aerosol. For a given composition, the temperature required to boil the liquid at 1 atmosphere must be at least somewhat greater than the boiling point (BP). The use of ENDS is increasing rapidly worldwide, yet the BP characteristics of the PG + GL system have been characterized as the mixtures; here we re-do this, but significantly, also study the effects of added water and nicotine. BP values at 1 atmosphere pressure were measured over the full binary composition range. Fits based on the Gibbs–Konovalov theorem provide BP as a function of composition (by mole-percent, by weight-percent, and by volume-percent). BPs of PG + GL mixtures were then tested in the presence of additives such as water (2.5 and 5 mol% added) and nicotine (3 mol%). Water was found to decrease the BP of PG + GL mixtures significantly at all compositions tested, and nicotine was found to decrease the BP of PG + GL mixtures containing ~75 GL: 25 PG (by moles) or more. The effect of added water (5, 10, and 15 mol% added) on electronic cigarette degradation production (some aldehydes and formaldehyde hemiacetals) was examined and found to have no significant impact on solvent (PG or GL) degradation for the particular device used.

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Incubation length and hatching asynchrony are integral elements of the evolved reproductive strategies of birds. We examined intra- and interpopulation variation in both traits for Eastern Kingbird (Tyrannus tyrannus) populations from New York (NY), Kansas (KS), and Oregon (OR) and found that both incubation length and hatching asynchrony were not repeatable among females, after controlling for a repeatable trait, clutch size. Instead, incubation length and clutch size were influenced by ambient temperature and precipitation. Incubation length exhibited the same median (15 days) and range (13–17 days) at all sites. Model selection results indicated that incubation periods for the smallest and largest clutches were longer in NY than KS when rain was frequent throughout incubation, in replacement nests, and likely when ambient temperatures were low during egg-laying. Full hatching usually required 2 days (but up to 3), with synchronous hatching associated with small clutch sizes, short incubation periods, frequent rain during the egg-laying period, and low ambient temperatures during the first half of incubation. Nestling starvation was uncommon (5–9% of nestlings monitored) and not associated with greater hatching asynchrony. These results indicate that while clutch size, a repeatable female trait, contributed to variation in incubation length and hatching asynchrony in Eastern Kingbirds, weather was a greater source of variation, especially for incubation length.