Daytime atmospheric oxidation chemistry is conventionally considered to be driven primarily by the OH radical, formed via photolytic sources. In this paper we examine how, during winter when ...photolytic processes are slow, chlorine chemistry can have a significant impact on oxidative processes in the urban boundary layer. Photolysis of nitryl chloride (ClNO2) provides a significant source of chlorine atoms, which enhances the oxidation of volatile organic compounds (VOCs) and the production of atmospheric pollutants.
We present a set of observations of ClNO2 and HONO made at urban locations in central England in December 2014 and February 2016. While direct emissions and in-situ chemical formation of HONO continue throughout the day, ClNO2 is only formed at night and is usually completely photolyzed by midday. Our data show that, during winter, ClNO2 often persists through the daylight hours at mixing ratios above 10–20 ppt (on average). In addition, relatively high mixing ratios of daytime HONO (>65 ppt) provide a strong source of OH radicals throughout the day.
The combined effects of ClNO2 and HONO result in sustained sources of Cl and OH radicals from sunrise to sunset, which form additional ozone, PAN, oxygenated VOCs, and secondary organic aerosol. We show that radical sources such as ClNO2 and HONO can lead to a surprisingly photoactive urban atmosphere during winter and should therefore be included in atmospheric chemical models.
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•High ClNO2 concentrations at sunrise cause it to persist until sunset above 10–20 ppt.•Daytime HONO accounts for over 90% of OH formation in the winter urban atmosphere.•Sustained sources of Cl and OH throughout the day enhance the oxidation of VOCs.•Production of O3 and secondary pollutants increases and continues into the afternoon.
Real-time profiling of mango ripening based on proton transfer reaction-time of flight-mass spectrometry (PTR–ToF–MS) of small molecular weight volatile organic compounds (VOCs), is demonstrated ...using headspace measurements of ‘Tommy Atkins’ mangoes. VOC metabolites produced during the ripening process were sampled directly, which enabled simultaneous and rapid detection of a wide range of compounds. Headspace measurements of ‘Keitt’ mangoes were also conducted for comparison. A principle component analysis of the results indicated that several mass channels were not only key to the ripening process but could also be used to distinguish between mango cultivars. The identities of 22 of these channels, tentatively speciated using contemporaneous GC–MS measurements of sorbent tubes, are rationalized through examination of the biochemical pathways that produce volatile flavour components. Results are discussed with relevance to the potential of headspace analysers and electronic noses in future fruit ripening and quality studies.
Acute cardiorespiratory breathlessness accounts for one in eight of all emergency hospitalizations. Early, noninvasive diagnostic testing is a clinical priority that allows rapid triage and ...treatment. Here, we sought to find and replicate diagnostic breath volatile organic compound (VOC) biomarkers of acute cardiorespiratory disease and understand breath metabolite network enrichment in acute disease, with a view to gaining mechanistic insight of breath biochemical derangements. We collected and analyzed exhaled breath samples from 277 participants presenting acute cardiorespiratory exacerbations and aged-matched healthy volunteers. Topological data analysis phenotypes differentiated acute disease from health and acute cardiorespiratory exacerbation subtypes (acute heart failure, acute asthma, acute chronic obstructive pulmonary disease, and community-acquired pneumonia). A multibiomarker score (101 breath biomarkers) demonstrated good diagnostic sensitivity and specificity (≥80%) in both discovery and replication sets and was associated with all-cause mortality at 2 years. In addition, VOC biomarker scores differentiated metabolic subgroups of cardiorespiratory exacerbation. Louvain clustering of VOCs coupled with metabolite enrichment and similarity assessment revealed highly specific enrichment patterns in all acute disease subgroups, for example, selective enrichment of correlated C5-7 hydrocarbons and C3-5 carbonyls in heart failure and selective depletion of correlated aldehydes in acute asthma. This study identified breath VOCs that differentiate acute cardiorespiratory exacerbations and associated subtypes and metabolic clusters of disease-associated VOCs.
The rapid urbanization and industrialization of northern China in recent decades has resulted in poor air quality in major cities like
Beijing. Transport of air pollution plays a key role in ...determining the relative influence of local emissions and regional contributions to observed
air pollution. In this paper, dispersion modelling (Numerical Atmospheric Modelling Environment, NAME model) is used with emission inventories and
in situ ground measurement data to track the pathways of air masses arriving in Beijing. The percentage of time the air masses spent over specific
regions during their travel to Beijing is used to assess the effects of regional meteorology on carbon monoxide (CO), a good tracer of
anthropogenic emissions. The NAME model is used with the MEIC (Multi-resolution Emission Inventory for China) emission inventories to determine the
amount of pollution that is transported to Beijing from the immediate surrounding areas and regions further away. This approach captures the
magnitude and variability of CO over Beijing and reveals that CO is strongly driven by transport processes. This study provides a more
detailed understanding of relative contributions to air pollution in Beijing under different regional airflow conditions. Approximately 45 %
over a 4-year average (2013–2016) of the total CO pollution that affects Beijing is transported from other regions, and about half of this
contribution comes from beyond the Hebei and Tianjin regions that immediately surround Beijing. The industrial sector is the dominant emission
source from the surrounding regions and contributes over 20 % of the total CO in Beijing. Finally, using PM2.5 to determine
high-pollution days, three pollution classification types of pollution were identified and used to analyse the APHH winter campaign and the 4-year
period. The results can inform targeted control measures to be implemented by Beijing and the surrounding provinces to tackle air quality problems
that affect Beijing and China.
Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful analytical tool for both nontargeted and targeted analyses. However, there is a need for more integrated workflows for ...processing and managing the resultant high-complexity datasets. End-to-end workflows for processing GC×GC data are challenging and often require multiple tools or software to process a single dataset. We describe a new approach, which uses an existing underutilized interface within commercial software to integrate free and open-source/external scripts and tools, tailoring the workflow to the needs of the individual researcher within a single software environment. To demonstrate the concept, the interface was successfully used to complete a first-pass alignment on a large-scale GC×GC metabolomics dataset. The analysis was performed by interfacing bespoke and published external algorithms within a commercial software environment to automatically correct the variation in retention times captured by a routine reference standard. Variation in 1tR and 2tR was reduced on average from 8 and 16% CV prealignment to less than 1 and 2% post alignment, respectively. The interface enables automation and creation of new functions and increases the interconnectivity between chemometric tools, providing a window for integrating data-processing software with larger informatics-based data management platforms.
Ambient measurements of nitryl chloride (ClNO2) were
performed at a rural site in Germany, covering three periods in winter,
summer, and autumn 2019, as part of the JULIAC campaign (Jülich
...Atmospheric Chemistry Project) that aimed to understand the
photochemical processes in air masses typical of midwestern Europe.
Measurements were conducted at 50 m aboveground, which was mainly located
in the nocturnal boundary layer and thus uncoupled from local surface
emissions. ClNO2 is produced at night by the heterogeneous reaction of
dinitrogen pentoxide (N2O5) on chloride (Cl−) that contains
aerosol. Its photolysis during the day is of general interest, as it produces chlorine (Cl) atoms that react with different atmospheric trace gases to form radicals. The highest-observed ClNO2 mixing ratio
was 1.6 ppbv (parts per billion by volume; 15 min average) during the night of 20 September. Air masses reaching the measurement site either originated from long-range transport from the southwest and had an oceanic influence or circulated in the nearby region and were influenced by anthropogenic activities. Nocturnal maximum ClNO2 mixing ratios were around 0.2 ppbv if originating from long-range transport in nearly all seasons, while the values were higher, ranging from 0.4 to 0.6 ppbv for regionally influenced air. The chemical composition of long-range transported air was similar in all investigated seasons, while the regional air exhibited larger differences between the seasons. The N2O5 necessary for ClNO2 formation comes from the reaction of nitrate radicals (NO3) with nitrogen dioxide (NO2), where NO3
itself is formed by a reaction of NO2 with ozone (O3). Measured
concentrations of ClNO2, NO2, and O3 were used to quantify
ClNO2 production efficiencies, i.e., the yield of ClNO2 formation
per NO3 radical formed, and a box model was used to examine the
idealized dependence of ClNO2 on the observed nocturnal O3 and
NO2 concentrations. Results indicate that ClNO2 production
efficiency was most sensitive to the availability of NO2 rather than
that of O3 and increased with decreasing temperature. The average
ClNO2 production efficiency was highest in February and September, with values of 18 %, and was lowest in December, with values of 3 %. The average ClNO2 production efficiencies were in the range of 3 % and 6 % from August to November for air masses originating from long-range transportation. These numbers are at the high end of values reported in the literature, indicating the importance of ClNO2 chemistry in rural environments in midwestern Europe.
Obesity and its co-morbidities, such as fatty liver disease, are increasingly prevalent worldwide health problems. Intestinal microorganisms have emerged as critical factors linking diet to host ...physiology and metabolic function, particularly in the context of lipid homeostasis. We previously demonstrated that deletion of the cytoplasmic lipid drop (CLD) protein Perilipin-2 (Plin2) in mice largely abrogates long-term deleterious effects of a high fat (HF) diet. Here we test the hypotheses that Plin2 function impacts the earliest steps of HF diet-mediated pathogenesis as well as the dynamics of diet-associated changes in gut microbiome diversity and function. WT and perilipin-2 null mice raised on a standard chow diet were randomized to either low fat (LF) or HF diets. After four days, animals were assessed for changes in physiological (body weight, energy balance, and fecal triglyceride levels), histochemical (enterocyte CLD content), and fecal microbiome parameters. Plin2-null mice had significantly lower respiratory exchange ratios, diminished frequencies of enterocyte CLDs, and increased fecal triglyceride levels compared with WT mice. Microbiome analyses, employing both 16S rRNA profiling and metagenomic deep sequencing, indicated that dietary fat content and Plin2 genotype were significantly and independently associated with gut microbiome composition, diversity, and functional differences. These data demonstrate that Plin2 modulates rapid effects of diet on fecal lipid levels, enterocyte CLD contents, and fuel utilization properties of mice that correlate with structural and functional differences in their gut microbial communities. Collectively, the data provide evidence of Plin2 regulated intestinal lipid uptake, which contributes to rapid changes in the gut microbial communities implicated in diet-induced obesity.
As the emissions of anthropogenic volatile organic compounds (VOCs) are reduced through regulatory measures and improved control technologies, biogenic VOCs could gain in importance in terms of ...reactivity, especially in urban areas. Here we investigate a 12 year record of non‐methane hydrocarbons (NMHCs) in central London and the importance of biogenics (in the form of isoprene) for ozone formation through the contribution to OH reactivity. Significant reductions in NMHCs were observed from 1998 through 2009 at an urban traffic site (−13% per year) and suburban background site (−5% per year) in London. Total isoprene levels decreased similarly and the relative contribution of isoprene to the total NMHC OH reactivity did not change. Furthermore, a dataset for Paris showed strong similarities to the data from London, which would indicate that these results are not limited to London. Interestingly, a rural site to the east of London, Harwell, showed similar contributions of isoprene to the total NMHC reactivity, which may indicate the need for measurements of other biogenic species, such as monoterpenes, in some areas to reliably capture the importance of biogenics in the region. These results would indicate that the influence of biogenic isoprene in London, and likely other low isoprene emitter urban areas have a long way to go before the importance of biogenic VOCs equals or exceeds that of anthropogenic contributions.
Key Points
Anthropogenic NMHCs have been reduced significantly over the past decade
Isoprene's importance for O3 formation has not increased despite HC reductions
Monitoring isoprene only as a proxy for biogenic influence may not be sufficient
Summary
Exposure to particulate matter (PM), a major component of air pollution, is associated with exacerbation of chronic respiratory disease, and infectious diseases such as community‐acquired ...pneumonia. Although PM can cause adverse health effects through direct damage to host cells, our previous study showed that PM can also impact bacterial behaviour by promoting in vivo colonization. In this study we describe the genetic mechanisms involved in the bacterial response to exposure to black carbon (BC), a constituent of PM found in most sources of air pollution. We show that Staphylococcus aureus strain USA300 LAC grown in BC prior to inoculation showed increased murine respiratory tract colonization and pulmonary invasion in vivo, as well as adhesion and invasion of human epithelial cells in vitro. Global transcriptional analysis showed that BC has a widespread effect on S. aureus transcriptional responses, altering the regulation of the major virulence gene regulators Sae and Agr and causing increased expression of genes encoding toxins, proteases and immune evasion factors. Together these data describe a previously unrecognized causative mechanism of air pollution‐associated infection, in that exposure to BC can increase bacterial colonization and virulence factor expression by acting directly on the bacterium rather than via the host.
Air quality and climate are often treated as separate science and policy areas. Air quality encompasses the here-and-now of pollutant emissions, atmospheric transformations and their direct effect on ...human and ecosystem health. Climate change deals with the drivers leading to a warmer world and the consequences of that. These two science and policy issues are inexorably linked via common pollutants, such as ozone (methane) and black carbon. This short review looks at the new scientific evidence around so-called "short-lived climate forcers" and the growing realisation that a way to meet short-term climate change targets may be through the control of "air quality" pollutants. None of the options discussed here can replace reduction of long-lived greenhouse gases, such as CO2, which is required for any long-term climate change mitigation strategy. An overview is given of the underlying science, remaining uncertainties, and some of the synergies and trade-offs for addressing air quality and climate in the science and policy context.
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