The contribution of stratosphere‐to‐troposphere transport to high surface ozone (O3) along the Colorado Front Range during spring of 1999 is examined using lidar and surface measurements. A deep ...tropopause fold brought ∼215 ppbv of O3 to within 1 km of the highest peaks in the Rocky Mountains on 6 May 1999. One‐minute average O3 mixing ratios exceeding 100 ppbv were subsequently measured at a surface site in Boulder, and daily maximum 8‐hour O3 concentrations greater or equal to the 2008 NAAQS O3 standard of 0.075 ppmv were recorded at 3 of 9 Front Range monitoring stations. Other springtime peaks in surface O3 are also shown to coincide with passage of upper level troughs and dry stable layers aloft. These results show that the stratospheric contribution to surface ozone is significant, and can lead to exceedance of the 2008 NAAQS O3 standards in a major U.S. metropolitan area.
The Indian megacity of Delhi suffers from some of the
poorest air quality in the world. While ambient NO2 and particulate
matter (PM) concentrations have received considerable attention in the city,
...high ground-level ozone (O3) concentrations are an often overlooked
component of pollution. O3 can lead to significant ecosystem damage and
agricultural crop losses, and adversely affect human health. During October 2018,
concentrations of speciated non-methane hydrocarbon volatile organic
compounds (C2–C13), oxygenated volatile organic compounds
(o-VOCs), NO, NO2, HONO, CO, SO2, O3, and photolysis rates,
were continuously measured at an urban site in Old Delhi. These observations
were used to constrain a detailed chemical box model utilising the Master
Chemical Mechanism v3.3.1. VOCs and NOx (NO + NO2) were varied
in the model to test their impact on local O3 production rates,
P(O3), which revealed a VOC-limited chemical regime. When only NOx
concentrations were reduced, a significant increase in P(O3) was
observed; thus, VOC co-reduction approaches must also be considered in
pollution abatement strategies. Of the VOCs examined in this work, mean
morning P(O3) rates were most sensitive to monoaromatic compounds,
followed by monoterpenes and alkenes, where halving their concentrations in
the model led to a 15.6 %, 13.1 %, and 12.9 % reduction in
P(O3), respectively. P(O3) was not sensitive to direct changes in
aerosol surface area but was very sensitive to changes in photolysis rates,
which may be influenced by future changes in PM concentrations. VOC and
NOx concentrations were divided into emission source sectors, as
described by the Emissions Database for Global Atmospheric Research (EDGAR) v5.0 Global Air Pollutant Emissions and EDGAR
v4.3.2_VOC_spec inventories, allowing for the
impact of individual emission sources on P(O3) to be investigated.
Reducing road transport emissions only, a common strategy in air pollution
abatement strategies worldwide, was found to increase P(O3), even when
the source was removed in its entirety. Effective reduction in P(O3)
was achieved by reducing road transport along with emissions from combustion
for manufacturing and process emissions. Modelled P(O3) reduced by
∼ 20 ppb h−1 when these combined sources were halved. This study
highlights the importance of reducing VOCs in parallel with NOx and PM
in future pollution abatement strategies in Delhi.
Dropwise condensation of water vapor from a naturally cooling, hot water reservoir onto a hydrophobic polymer film and a silanized glass slide was studied by direct observation and simulations. The ...observed drop growth kinetics suggests that smallest drops grow principally by the diffusion of water adsorbed on the substrate to the drop perimeter, while drops larger than about 50 μm in diameter grow principally by direct deposition from the vapor onto the drop surface. Drop coalescence plays a critical role in determining the drop-size distribution and stimulates the nucleation of new, small drops on the substrates. Simulations of drop growth incorporating these growth mechanisms provide a good description of the observed drop-size distribution. Because of the large role played by coalescence, details of individual drop growth make little difference to the final drop-size distribution. The rate of condensation per unit substrate area is especially high for the smallest drops and may help account for the high heat transfer rates associated with dropwise condensation relative to filmwise condensation in heat exchange applications.
The REgents PARk and Tower Environmental Experiment (REPARTEE) comprised two campaigns in London in October 2006 and October/November 2007. The experiment design involved measurements at a heavily ...trafficked roadside site, two urban background sites and an elevated site at 160-190 m above ground on the BT Tower, supplemented in the second campaign by Doppler lidar measurements of atmospheric vertical structure. A wide range of measurements of airborne particle physical metrics and chemical composition were made as well as measurements of a considerable range of gas phase species and the fluxes of both particulate and gas phase substances. Significant findings include (a) demonstration of the evaporation of traffic-generated nanoparticles during both horizontal and vertical atmospheric transport; (b) generation of a large base of information on the fluxes of nanoparticles, accumulation mode particles and specific chemical components of the aerosol and a range of gas phase species, as well as the elucidation of key processes and comparison with emissions inventories; (c) quantification of vertical gradients in selected aerosol and trace gas species which has demonstrated the important role of regional transport in influencing concentrations of sulphate, nitrate and secondary organic compounds within the atmosphere of London; (d) generation of new data on the atmospheric structure and turbulence above London, including the estimation of mixed layer depths; (e) provision of new data on trace gas dispersion in the urban atmosphere through the release of purposeful tracers; (f) the determination of spatial differences in aerosol particle size distributions and their interpretation in terms of sources and physico-chemical transformations; (g) studies of the nocturnal oxidation of nitrogen oxides and of the diurnal behaviour of nitrate aerosol in the urban atmosphere, and (h) new information on the chemical composition and source apportionment of particulate matter size fractions in the atmosphere of London derived both from bulk chemical analysis and aerosol mass spectrometry with two instrument types.
The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout California in May, June, and July of 2010. The study was organized to address ...issues simultaneously relevant to atmospheric pollution and climate change, including (1) emission inventory assessment, (2) atmospheric transport and dispersion, (3) atmospheric chemical processing, and (4) cloud‐aerosol interactions and aerosol radiative effects. Measurements from networks of ground sites, a research ship, tall towers, balloon‐borne ozonesondes, multiple aircraft, and satellites provided in situ and remotely sensed data on trace pollutant and greenhouse gas concentrations, aerosol chemical composition and microphysical properties, cloud microphysics, and meteorological parameters. This overview report provides operational information for the variety of sites, platforms, and measurements, their joint deployment strategy, and summarizes findings that have resulted from the collaborative analyses of the CalNex field study. Climate‐relevant findings from CalNex include that leakage from natural gas infrastructure may account for the excess of observed methane over emission estimates in Los Angeles. Air‐quality relevant findings include the following: mobile fleet VOC significantly declines, and NOx emissions continue to have an impact on ozone in the Los Angeles basin; the relative contributions of diesel and gasoline emission to secondary organic aerosol are not fully understood; and nighttime NO3 chemistry contributes significantly to secondary organic aerosol mass in the San Joaquin Valley. Findings simultaneously relevant to climate and air quality include the following: marine vessel emissions changes due to fuel sulfur and speed controls result in a net warming effect but have substantial positive impacts on local air quality.
Key Points
An overview of the multi‐platform, multi‐agency CalNex field study in 2010
A synthesis of CalNex research to date
Emphasis on policy‐relevant conclusions linking climate and air quality issues
In the traditional clinical research model, patients are typically involved only as participants. However, there has been a shift in recent years highlighting the value and contributions that ...patients bring as members of the research team, across the clinical research lifecycle. It is becoming increasingly evident that to develop research that is both meaningful to people who have the targeted condition and is feasible, there are important benefits of involving patients in the planning, conduct, and dissemination of research from its earliest stages. In fact, research funders and regulatory agencies are now explicitly encouraging, and sometimes requiring, that patients are engaged as partners in research. Although this approach has become commonplace in some fields of clinical research, it remains the exception in clinical pain research. As such, the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials convened a meeting with patient partners and international representatives from academia, patient advocacy groups, government regulatory agencies, research funding organizations, academic journals, and the biopharmaceutical industry to develop consensus recommendations for advancing patient engagement in all stages of clinical pain research in an effective and purposeful manner. This article summarizes the results of this meeting and offers considerations for meaningful and authentic engagement of patient partners in clinical pain research, including recommendations for representation, timing, continuous engagement, measurement, reporting, and research dissemination.
We describe a highly sensitive and specific multiplex PCR, based on capsular loci and the species specific apxIV gene, that unequivocally differentiates serovar 3, 6, and 8 Actinobacillus ...pleuropneumoniae strains that are cross-reactive in conventional immunological tests.
The dissolution of liquids with low mutual solubility is typically slow. However, drops of sparingly soluble, low-density, low-surface-tension liquids often dissolve rapidly on water due to surface ...tension instabilities and gradients. We report observations of the motion and dissolution of drops of aliphatic alcohols of a wide range of alkyl chain lengths as they dissolve in water. The alcohol drops are rendered visible by adding small amounts of iodine or other dyes. These drops display dewetting instabilities, fragmentation, fingering, and oscillation. As the length of the alcohol carbon chain increases from n = 4 to n = 9, dissolution slows dramatically. The roles of alcohol solubility and water surface area in promoting rapid dissolution are discussed.
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