Dynamics of carbon dioxide (CO2) emissions following the wetting of dry soil have been widely studied in field and laboratory settings. Nonmethane volatile organic compounds (VOCs) are also emitted from soil following a rain event and are evident from the characteristic smell of wet soil. Few studies have documented VOC emissions before and after soil rewetting. Soil emissions were studied using a dynamic flux chamber system purged with VOC‐free air, with identification and quantification of emissions performed by gas chromatography/mass spectrometry. All soils exhibited a rewetting‐induced pulse of VOC emissions, with VOC emissions 14 times higher (on average) in the few hours after rewetting compared to moist soils 2 days after rewetting. This VOC rewetting pulse mirrored the CO2 rewetting pulse (the so‐called “Birch Effect”) but was shorter in duration. Average VOC emissions were 5.0 ± 2.0% of CO2 emissions (molar C equivalent) and increased with increasing soil organic matter content (ρ = 0.40, ρ = 0.99 with one soil excluded). The amounts and types of VOCs varied with time since rewetting and across the five studied soil types, though acetone and small hydrocarbons were the dominant compounds emitted from all soils. Some of the VOCs emitted are likely important mediators of microbial activities and relevant to atmospheric chemical dynamics. Soil VOC emissions, similar to CO2 emissions, are strongly affected by rewetting events, and it is important to consider these rewetting dynamics when modeling soil and ecosystem VOC emissions and understand their relevance to terrestrial ecosystem functioning and atmospheric processes.

Soil microbes produce an immense diversity of metabolites, including volatile organic compounds (VOCs), which can shape the structure and function of microbial communities. VOCs mediate a multitude of microbe-microbe interactions, including antagonism. Despite their importance, the diversity and functional relevance of most microbial volatiles remain uncharacterized. We assembled a taxonomically diverse collection of 48Actinobacteriaisolated from soil and airborne dust and surveyed the VOCs produced by these strains on two different medium typesin vitrousing gas chromatography-mass spectrometry (GC-MS). We detected 126 distinct VOCs and structurally identified approximately 20% of these compounds, which were predominately C1to C5hetero-VOCs, including (oxygenated) alcohols, ketones, esters, and nitrogen- and sulfur-containing compounds. Each strain produced a unique VOC profile. While the most common VOCs were likely by-products of primary metabolism, most of the VOCs were strain specific. We observed a strong taxonomic and phylogenetic signal for VOC profiles, suggesting their role in finer-scale patterns of ecological diversity. Finally, we investigated the functional potential of these VOCs by assessing their effects on growth rates of both pathogenic and nonpathogenic pseudomonad strains. We identified sets of VOCs that correlated with growth inhibition and stimulation, information that may facilitate the development of microbial VOC-based pathogen control strategies.IMPORTANCESoil microbes produce a diverse array of natural products, including volatile organic compounds (VOCs). Volatile compounds are important molecules in soil habitats, where they mediate interactions between bacteria, fungi, insects, plants, and animals. We measured the VOCs produced by a broad diversity of soil- and dust-dwellingActinobacteria in vitro. We detected a total of 126 unique volatile compounds, and each strain produced a unique combination of VOCs. While some of the compounds were produced by many strains, most were strain specific. Importantly, VOC profiles were more similar between closely related strains, indicating that evolutionary and ecological processes generate predictable patterns of VOC production. Finally, we observed that actinobacterial VOCs had both stimulatory and inhibitory effects on the growth of bacteria that represent a plant-beneficial symbiont and a plant-pathogenic strain, information that may lead to the development of novel strategies for plant disease prevention.

Nonmethane hydrocarbons have been used as tracers in research on emissions and atmospheric oxidation chemistry. This research investigates source region mixing ratio trends of the nonmethane hydrocarbons i‐butane, n‐butane, i‐pentane, and n‐pentane, and the (i/n) isomeric ratios of these compounds between 2001 and 2015. Data collected at Photochemical Assessment Monitoring Stations, mandated by the U.S. Environmental Protection Agency in ozone nonattainment areas, and data collected at Global Greenhouse Gas Reference Network sites within the National Oceanic and Atmospheric Administration network, and analyzed at the Institute of Arctic and Alpine Research at the University of Colorado‐Boulder, were examined. Among all considered species, linear regression analyses on concentration time series had negative slopes at 81% of sites, indicating predominantly declining butane and pentane atmospheric concentrations. Mostly negative slopes (78% of sites) were found for the (i/n) butane and pentane isomeric ratios, including all six and seven statistically significant (i/n) butane and pentane trends, respectively. Over the ~15 year investigation period and averaged over all sites, total relative changes were ~30 and 45% for the (i/n) ratios of butanes and pentanes, respectively, with a relative increase in the prominence of the n‐isomers. Most likely causes include changing isomeric ratios in gasoline sector emissions, and increasing influence of oil and natural gas industry emissions. Changes in concentrations and isomeric ratios depend on proximity of contributing emission sources to measurement sites.

Background Preliminary studies have shown that respiratory–swallow training (RST) is a successful treatment for oropharyngeal head and neck cancer patients with refractory dysphagia. Refining the RST protocol with automated analysis software to provide real-time performance feedback has the potential to improve accessibility, reproducibility, and translation to diverse clinical settings. Method An automated software program for data acquisition and analysis developed to detect swallows, determine respiratory phase, calculate lung volume at the onset of the swallow, and provide real-time performance feedback was tested for feasibility in a small cohort of healthy adults. Outcome Measures Percent difference in swallow detection and accuracy of real-time performance feedback of respiratory phase and lung volume at swallowing onset between the automated software and the manual gold standard method were determined. Results The automated software program accurately detected the onset of the swallow on 91% of the swallows completed during the training trials. Feedback of respiratory phase and lung volume was accurate on 94% of the trials in which the swallow was accurately detected. Conclusions This novel, automated, and real-time RST software successfully detected the onset of the swallow, respiratory phase, and lung volume at swallow onset and provided appropriate real-time performance feedback with a high degree of accuracy in healthy adults. The software has the potential to improve the accessibility, efficiency, and translation of RST to diverse patient populations.