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Supplemental material, sj-docx-3-dhj-10.1177_20552076231180973 for Towards multimodal boosting of motivation for fall-preventive physical activity in seniors: An iterative development evaluation study by Å. Revenäs, L. Ström, A. Cicchetti and M. Ehn in DIGITAL HEALTH

Supplemental material, sj-docx-5-dhj-10.1177_20552076231180973 for Towards multimodal boosting of motivation for fall-preventive physical activity in seniors: An iterative development evaluation study by Å. Revenäs, L. Ström, A. Cicchetti and M. Ehn in DIGITAL HEALTH

Supplemental material, sj-docx-2-dhj-10.1177_20552076231180973 for Towards multimodal boosting of motivation for fall-preventive physical activity in seniors: An iterative development evaluation study by Å. Revenäs, L. Ström, A. Cicchetti and M. Ehn in DIGITAL HEALTH

Supplemental material, sj-docx-1-dhj-10.1177_20552076231180973 for Towards multimodal boosting of motivation for fall-preventive physical activity in seniors: An iterative development evaluation study by Å. Revenäs, L. Ström, A. Cicchetti and M. Ehn in DIGITAL HEALTH

Supplemental material, sj-docx-4-dhj-10.1177_20552076231180973 for Towards multimodal boosting of motivation for fall-preventive physical activity in seniors: An iterative development evaluation study by Å. Revenäs, L. Ström, A. Cicchetti and M. Ehn in DIGITAL HEALTH

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Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOₓ) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOₓ. We show that NOₓ suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOₓ. By illustrating how NOₓ affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOₓ level in forest regions around the globe.

The climate impact of deforestation depends on the relative strength of several biogeochemical and biogeophysical effects. In addition to affecting the exchange of carbon dioxide (CO2) and moisture with the atmosphere and surface albedo, vegetation emits biogenic volatile organic compounds (BVOCs) that alter the formation of short-lived climate forcers (SLCFs), which include aerosol, ozone and methane. Here we show that a scenario of complete global deforestation results in a net positive radiative forcing (RF; 0.12Wm-2) from SLCFs, with the negative RF from decreases in ozone and methane concentrations partially offsetting the positive aerosol RF. Combining RFs due to CO2, surface albedo and SLCFs suggests that global deforestation could cause 0.8 K warming after 100 years, with SLCFs contributing 8% of the effect. However, deforestation as projected by the RCP8.5 scenario leads to zero net RF from SLCF, primarily due to nonlinearities in the aerosol indirect effect.

The formation of secondary particles in the atmosphere accounts for more than half of global cloud condensation nuclei. Experiments at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber have underlined the importance of ions for new particle formation, but quantifying their effect in the atmosphere remains challenging. By using a novel instrument setup consisting of two nanoparticle counters, one of them equipped with an ion filter, we were able to further investigate the ion-related mechanisms of new particle formation. In autumn 2015, we carried out experiments at CLOUD on four systems of different chemical compositions involving monoterpenes, sulfuric acid, nitrogen oxides, and ammonia. We measured the influence of ions on the nucleation rates under precisely controlled and atmospherically relevant conditions. Our results indicate that ions enhance the nucleation process when the charge is necessary to stabilize newly formed clusters, i.e., in conditions in which neutral clusters are unstable. For charged clusters that were formed by ion-induced nucleation, we were able to measure, for the first time, their progressive neutralization due to recombination with oppositely charged ions. A large fraction of the clusters carried a charge at 1.5 nm diameter. However, depending on particle growth rates and ion concentrations, charged clusters were largely neutralized by ion–ion recombination before they grew to 2.5 nm. At this size, more than 90 % of particles were neutral. In other words, particles may originate from ion-induced nucleation, although they are neutral upon detection at diameters larger than 2.5 nm. Observations at Hyytiälä, Finland, showed lower ion concentrations and a lower contribution of ion-induced nucleation than measured at CLOUD under similar conditions. Although this can be partly explained by the observation that ion-induced fractions decrease towards lower ion concentrations, further investigations are needed to resolve the origin of the discrepancy., published version, peerReviewed

SSCI-VIDE+CARE+MRV:DLI:STO:FBO:SPR:CGO; International audience; Oxidation of volatile organic compound (VOC) leads to the formation of an extensive variety of oxygenated VOCs (OVOCs), with some of them being capable of forming and growing aerosols. Recently, the identification of the formation of highly oxygenated organic molecules (HOM) using chemical ionization mass spectrometer (CIMS) represents both an atmospheric science and instrumental breakthrough. The CIMS allows the detection of a wide range of OVOCs. It is usually used with medium to high resolution (from 4000 to 14000) time-of-flight (TOF) mass analyzers providing extensive chemical information for the identification of key compounds. However, for complex mixtures, these mass analyzers can display overlapping ion signals therefore increasing measurement uncertainties. The goal of this work was to overcome this mass resolution limitation by coupling an Orbitrap mass spectrometer (resolution of 140 000 at m/z 200), to a nitrate-ion-based (NO3-) CI source, known to be highly selective and sensitive towards atmospheric reactive species (including HOM). We analyzed the OVOC generated from two well-known systems (alpha-pinene and limonene ozonolysis) and evaluated the impact of various experimental conditions on the MS signal. The ultra-high resolving power of the CI-Orbitrap allows an unambiguous identification of all ions while the medium to high resolution TOF mass analyzers do not allow this ion separation and provides more uncertain information. The use of the MS² feature provided novel and useful structural information that could help identifying key compounds. In conclusion, this new analytical instrument can give a better understanding of the formation and fate of atmospheric reactive species.

The impact of nitrogen oxides (NOx = NO + NO2) on new particle formation (NPF) and on photochemical ozone production from real plant volatile organic compound (BVOC) emissions was studied in a laboratory setup. At high NOx conditions ([BVOC] / [NOx] < 7, [NOx] > 23 ppb) new particle formation was suppressed. Instead, photochemical ozone formation was observed resulting in higher hydroxyl radical (OH) and lower nitrogen monoxide (NO) concentrations. When [NO] was reduced back to levels below 1 ppb by OH reactions, NPF was observed. Adding high amounts of NOx caused NPF to be slowed by orders of magnitude compared to analogous experiments at low NOx conditions ([NOx] ~300 ppt), although OH concentrations were higher. Varying NO2 photolysis enabled showing that NO was responsible for suppression of NPF. This suggests that peroxy radicals are involved in NPF. The rates of NPF and photochemical ozone production were related by power law dependence with an exponent approaching −2. This exponent indicated that the overall peroxy radical concentration must have been similar when NPF occurred. Thus, permutation reactions of first-generation peroxy radicals cannot be the rate limiting step in NPF from monoterpene oxidation. It was concluded that permutation reactions of higher generation peroxy-radical-like intermediates limit the rate of new particle formation. In contrast to the strong effects on the particle numbers, the formation of particle mass was substantially less sensitive to NOx concentrations. If at all, yields were reduced by about an order of magnitude only at very high NOx concentrations.

Measurements on the composition of nanometer-sized atmospheric particles are the key to understand which vapors participate in the secondary aerosol formation processes. Knowledge on these processes is crucial in assessing the climatic effects of secondary aerosol formation. We present data of >2 nm particle concentrations and their water-affinity measured with the Condensation Particle Counter Battery (CPCB) at a boreal forest site in Hyytiälä, Finland, during spring 2006. The data reveal that during new particle formation events, the smallest particles activate for growth at clearly smaller sizes in water than in butanol vapor. However, even at 2–4 nm, there are days when the particles seem to be less hygroscopic than ammonium sulfate or sulfuric acid, which are often referred to as the most likely compounds present in atmospheric nucleation. This observation points to the possible presence of water-soluble organics, even at the very first steps on particle formation. The water-affinity of the particles decreases with size, indicating that the vapors that participate in the first steps of the particle formation and growth are more hygroscopic than the vapors contributing to the later stages of the growth. This suggests that the relative role of less hygroscopic organics in atmospheric particle growth increases as a function of particle size.

It has been postulated that secondary organic particulate matter plays a pivotal role in the early growth of newly formed particles in forest areas. The recently detected class of extremely low volatile organic compounds (ELVOC) provides the missing organic vapours and possibly contributes a~significant fraction to atmospheric SOA. ELVOC are highly oxidized multifunctional molecules (HOM), formed by sequential rearrangement of peroxy radicals and subsequent O2 addition. Key for efficiency in early particle growth is that formation of HOM is induced by one attack of the oxidant (here O3) and followed by an autoxidation process involving molecular oxygen. Similar mechanisms were recently observed and predicted by quantum mechanical calculations e.g. for isoprene. To assess the atmospheric importance and therewith the potential generality, it is crucial to understand the formation pathway of HOM.To elucidate the formation path of HOM as well as necessary and sufficient structural prerequisites of their formation we studied homologues series of cycloalkenes in comparison to two monoterpenes. We were able to directly observe highly oxidized multifunctional peroxy radicals with 8 or 10 O-atoms by an Atmospheric Pressure interface High Resolution Time of Flight Mass Spectrometer equipped with a NO3−-Chemical Ionization (CI) source. In case of O3 acting as oxidant the starting peroxy radical is formed on the so called vinylhydroperoxide path. HOM peroxy radicals and their termination reactions with other peroxy radicals, including dimerization, allowed for analysing the observed mass spectra and narrow down the likely formation path. As consequence we propose that HOM are multifunctional percarboxylic acids; with carbonyl-, hydroperoxy-, or hydroxy-groups arising from the termination steps. We figured that aldehyde groups facilitate the initial rearrangement steps. In simple molecules like cyloalkenes autoxidation was limited to both terminal C-atoms and two further C-atoms in the respective α-positions. In more complex molecules containing tertiary H-atoms or small constraint rings even higher oxidation degree were possible, either by simple H-shift of the tertiary H-atom or by initialisation of complex ring-opening reactions.

Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of the reaction of stabilized Criegee intermediates (sCIs) with SO2, atmospheric oxidation processes were thought to be dominated by a few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulfuric acid (H2SO4). The measured total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) /k(sCI + SO2), was determined at relative humidities of 10 and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0–2.4) × 1012 molecules cm−3 and nearly independent of the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster with the organic acids than with SO2; k(sCI + acid) / k(sCI + SO2) = (2.8 ± 0.3) for formic acid, and k(sCI + acid) / k(sCI + SO2) = (3.4 ± 0.2) for acetic acid. This finding indicates that sCIs can play a role in the formation and loss of other atmospheric constituents besides SO2.