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1. Toward a molecular understanding of the surface composition of atmospherically relevant organic particles

   https://doi.org/10.1073/pnas.2209134119  

   Qin, Y.; Wingen, L. M.; Finlayson-Pitts, B. J. (August 2022, Proceedings of the National Academy of Sciences)

   Many mass spectrometry methods using various ionization sources provide bulk composition of airborne particles, but little is known about the surface species that play a major role in determining their physicochemical properties that impact air quality, climate, and health. The present work shows that the composition of surface layers of atmospherically relevant submicron organic particles can be probed without the use of an external ionization source. Solid dicarboxylic acid particles are used as models, with glutaric acid being the most efficient at generating ions. Coating with small diacids or products from α-pinene ozonolysis demonstrates that ions are ejected from the surface, providing surface molecular characterization of organic particles on the fly. This unique approach provides a path forward for elucidating the role of the surface in determining chemical and physical properties of particles, including heterogeneous reactions, particle growth, water uptake, and interactions with biological systems. 

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2. Chemistry and Human Exposure Implications of Secondary Organic Aerosol Production from Indoor Terpene Ozonolysis

   https://doi.org/10.1126/sciadv.abj9156  

   Rosales, C.M.F.; Jiang, J.; Lahib, A.; Bottorff, B.P.; Reidy, E.K.; Kumar, V.; Tasoglou, A.; Huber, H.; Dusanter, S.; Tomas, A.; et al (January 2022, Science advances)

   Surface cleaning using commercial disinfectants, which has recently increased during the coronavirus disease 2019 pandemic, can generate secondary indoor pollutants both in gas and aerosol phases. It can also affect indoor air quality and health, especially for workers repeatedly exposed to disinfectants. Here, we cleaned the floor of a mechanically ventilated office room using a commercial cleaner while concurrently measuring gas-phase precursors, oxidants, radicals, secondary oxidation products, and aerosols in real time; these were detected within minutes after cleaner application. During cleaning, indoor monoterpene concentrations exceeded outdoor concentrations by two orders of magnitude, increasing the rate of ozonolysis under low (<10 ppb) ozone levels. High number concentrations of freshly nucleated sub–10-nm particles (≥105 cm−3) resulted in respiratory tract deposited dose rates comparable to or exceeding that of inhalation of vehicle-associated aerosols. 

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3. Cleaning Effect of Bubbles Impacting Tilted Walls Under Acoustic Waves

   https://doi.org/10.1115/FEDSM2022-86897  

   Hooshanginejad, Alireza; Sheppard, Timothy J.; Manyalla, Janeth; Jaicks, John; Jung, Sunghwan (August 2022, Proceedings of the ASME 2022 Fluids Engineering Division Summer Meeting)

   Abstract The motion of bubbles near walls is ubiquitous for cleaning purposes in natural and industrial systems. Shear stress induced by bubbles on the surface is used to remove particles or bacteria adhering to the surface. In this study, we investigate the cleaning effect of bubbles on a surface coated with a protein soil solution with and without the presence of an acoustic wave transducer at a single frequency. In addition, we test different drying times for the coated surfaces before conducting the cleaning tests. Our results show that the best bubble cleaning effect occurs for the shortest drying time of the coating and an acoustic wave of 100 Hz. 

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4. Residual impacts of a wildland urban interface fire on urban particulate matter and dust: a study from the Marshall Fire

   https://doi.org/10.1007/s11869-023-01376-3  

   Silberstein, Jonathan M.; Mael, Liora E.; Frischmon, Caroline R.; Rieves, Emma S.; Coffey, Evan R.; Das, Trupti; Dresser, William; Hatch, Avery C.; Nath, Jyotishree; Pliszka, Helena O.; et al (January 2023, Air Quality, Atmosphere & Health)

   The impacts of wildfires along the wildland urban interface (WUI) on atmospheric particulate concentrations and composition are an understudied source of air pollution exposure. To assess the residual impacts of the 2021 Marshall Fire (Colorado), a wildfire that predominantly burned homes and other human-made materials, on homes within the fire perimeter that escaped the fire, we performed a combination of fine particulate matter (PM2.5) filter sampling and chemical analysis, indoor dust collection and chemical analysis, community scale PurpleAir PM2.5 analysis, and indoor particle number concentration measurements. Following the fire, the chemical speciation of dust collected in smoke-affected homes in the burned zone showed elevated concentrations of the biomass burning marker levoglucosan (medianlevo = 4147 ng g−1), EPA priority toxic polycyclic aromatic hydrocarbons (median Σ16PAH = 1859.3 ng g−1), and metals (median Σ20Metals = 34.6 mg g−1) when compared to samples collected in homes outside of the burn zone 6 months after the fire. As indoor dust particles are often resuspended and can become airborne, the enhanced concentration of hazardous metals and organics within dust samples may pose a threat to human health. Indoor airborne particulate organic carbon (median = 1.91 μg m−3), particulate elemental carbon (median = .02 μg m−3), and quantified semi-volatile organic species in PM2.5 were found in concentrations comparable to ambient air in urban areas across the USA. Particle number and size distribution analysis at a heavily instrumented supersite home located immediately next to the burned area showed indoor particulates in low concentrations (below 10 μg m−3) across various sizes of PM (12 nm–20 μm), but were elevated by resuspension from human activity, including cleaning. 

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5. How to Stick the Landing: Kangaroo Rats Use Their Tails to Reorient during Evasive Jumps Away from Predators

   https://doi.org/10.1093/icb/icab043  

   Schwaner, M Janneke; Freymiller, Grace A; Clark, Rulon W; McGowan, Craig P (May 2021, Integrative and Comparative Biology)

   Synopsis Tails are widespread in the animal world and play important roles in locomotor tasks, such as propulsion, maneuvering, stability, and manipulation of objects. Kangaroo rats, bipedal hopping rodents, use their tail for balancing during hopping, but the role of their tail during the vertical evasive escape jumps they perform when attacked by predators is yet to be determined. Because we observed kangaroo rats swinging their tails around their bodies while airborne following escape jumps, we hypothesized that kangaroo rats use their tails to not only stabilize their bodies while airborne, but also to perform aerial re-orientations. We collected video data from free-ranging desert kangaroo rats (Dipodomys deserti) performing escape jumps in response to a simulated predator attack and analyzed the rotation of their bodies and tails in the yaw plane (about the vertical-axis). Kangaroo rat escape responses were highly variable. The magnitude of body re-orientation in yaw was independent of jump height, jump distance, and aerial time. Kangaroo rats exhibited a stepwise re-orientation while airborne, in which slower turning periods corresponded with the tail center of mass being aligned close to the vertical rotation axis of the body. To examine the effect of tail motion on body re-orientation during a jump, we compared average rate of change in angular momentum. Rate of change in tail angular momentum was nearly proportional to that of the body, indicating that the tail reorients the body in the yaw plane during aerial escape leaps by kangaroo rats. Although kangaroo rats make dynamic 3D movements during their escape leaps, our data suggest that kangaroo rats use their tails to control orientation in the yaw plane. Additionally, we show that kangaroo rats rarely use their tail length at full potential in yaw, suggesting the importance of tail movement through multiple planes simultaneously. 

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