Publications by authors named "David C Doughty"

3 Publications

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Shielding of viruses such as SARS-Cov-2 from ultraviolet radiation in particles generated by sneezing or coughing: Numerical simulations of survival fractions.

J Occup Environ Hyg 2021 Jul 21:1-15. Epub 2021 Jul 21.

DEVCOM Army Research Laboratory, Adelphi, Maryland.

SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations within the particle. Previously, we demonstrated shielding in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to extend that work to survival fractions of virions (i.e., fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. Here, the survival fraction () of a set of individual virions illuminated with a UV fluence (, in J/m) is assumed described by () = exp(), where is the UV inactivation rate constant (m/J). The average survival fraction () of the simulated virions in a group of particles is calculated using the energy absorbed by each virion in the particles. The results show that virions within particles of dried respiratory fluids can have larger than do individual virions. For individual virions, and virions within 1-, 5-, and 9-µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the = 0.00005, 0.0155, 0.22, and 0.28, respectively, when  10. The decrease to <10, <10, 0.077, and 0.15, respectively, for  = 100. Results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the . These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important to effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the . The results suggest the need for measurements of the of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.
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http://dx.doi.org/10.1080/15459624.2021.1939877DOI Listing
July 2021

Viruses such as SARS-CoV-2 can be partially shielded from UV radiation when in particles generated by sneezing or coughing: Numerical simulations.

J Quant Spectrosc Radiat Transf 2021 Mar 24;262:107489. Epub 2020 Dec 24.

Auburn University, Auburn, AL, USA.

UV radiation can inactivate viruses such as SARS-CoV-2. However, designing effective UV germicidal irradiation (UVGI) systems can be difficult because the effects of dried respiratory droplets and other fomites on UV light intensities are poorly understood. Numerical modeling of UV intensities inside virus-containing particles on surfaces can increase understanding of these possible reductions in UV intensity. We model UV intensities within spherical approximations of virions randomly positioned within spherical particles. The model virions and dried particles have sizes and optical properties to approximate SARS-CoV-2 and dried particles formed from respiratory droplets, respectively. In 1-, 5- and 9-µm diameter particles on a surface, illuminated by 260-nm UV light from a direction perpendicular to the surface, 0%, 10% and 18% (respectively) of simulated virions are exposed to intensities less than 1/100 of intensities in individually exposed virions (i.e., they are partially shielded). Even for 302-nm light (simulating sunlight), where absorption is small, 0% and 11% of virions in 1- and 9-µm particles have exposures 1/100 those of individually exposed virions. Shielding is small to negligible in sub-micron particles. Results show that shielding of virions in a particle can be reduced by illuminating a particle either from multiple widely separated incident directions, or by illuminating a particle rotating in air for a time sufficient to rotate through enough orientations. Because highly UV-reflective paints and surfaces can increase the angular ranges of illumination and the intensities within particles, they appear likely to be useful for reducing shielding of virions embedded within particles.
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http://dx.doi.org/10.1016/j.jqsrt.2020.107489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7836904PMC
March 2021

Demonstration of a mobile Flux Laboratory for the Atmospheric Measurement of Emissions (FLAME) to assess emissions inventories.

J Environ Monit 2009 Feb 11;11(2):259-68. Epub 2008 Dec 11.

Via Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, 418 Durham Hall (0246), Blacksburg, VA 24061, USA.

The advancement of air quality science and the development of effective air quality management plans require accurate estimates of emissions. In response to the need for new approaches to quantifying emissions, we have designed a mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME) that uses eddy covariance for the direct measurement of anthropogenic emissions at the neighborhood scale. To demonstrate the FLAME's capabilities, we have deployed it in the Huntington-Ashland region at the borders of Ohio, Kentucky and West Virginia. This area routinely experiences high ozone and fine particulate matter (PM(2.5)) concentrations and is home to a significant amount of industrial activity, including coal storage and transport. Experiments focused on carbon dioxide (CO(2)), nitrogen oxides (NO(x)) and fine particulate matter (PM(2.5)). Spikes in CO(2) and NO(x) concentrations were correlated with the passage of trains and barges through the FLAME's footprint. Calculated barge emission factors ranged from 49 to 76 kg NO(x) tonne(-1) fuel and agreed well with previously published values. Fluxes measured at three sites in the town of Worthington were mainly positive. They ranged between -6.5 to 29 mg m(-2) s(-1) for CO(2) and -9.7 x 10(-5) to 9.1 x 10(-5) mg m(-2) s(-1) for PM(2.5). We illustrate how the measurements can be compared to emissions inventories on a per capita basis for greenhouse gases and countywide for other pollutants. The results show that a mobile eddy covariance system can be used successfully to measure fluxes of multiple pollutants in a variety of settings. This alternative method for estimating emissions can be a useful tool for assessing uncertainties in emissions inventories and for improving their accuracy.
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http://dx.doi.org/10.1039/b810798jDOI Listing
February 2009
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