scholarly journals Formation of Secondary Organic Aerosols by Germicidal Ultraviolet Light

Environments ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 17
Author(s):  
Eureka Choi ◽  
Zhongchao Tan ◽  
William Anderson
Keyword(s):  
Uv Light ◽  
Fine Particulate Matter ◽  
Particle Formation ◽  
Uv Exposure ◽  
Indoor Environments ◽  
Fine Particulate ◽  
Volatile Organic ◽  
Solar Uv ◽  
Commercial Environment ◽  
Number Of Particles

Ultraviolet (UV) light with a wavelength of 254 nm is known to be germicidal, and thus has been increasingly employed as a method of disinfection for indoor environments. Solar UV wavelengths (300 to 400 nm) are known to initiate the formation of secondary organic aerosol (SOA) particles from the photo-oxidation of volatile organic compounds (VOC) in the atmosphere, but germicidal wavelengths have not been extensively studied for indoor environments. In this work, toluene was exposed to 254 nm UV light in a laboratory photoreactor while varying the conditions of the air, the duration of UV exposure, and the duration of post-UV time. The number of particles formed in the fine particulate matter (PM2.5) size range was measured, and significant levels of particle formation were observed for UV exposure periods of as short as 5 min. The particle formation ranged from 2.4 × 106 particles/m3 for 5 min of UV exposure, to 163.2 × 106 particles/m3 for 15 min of UV exposure, for toluene concentrations in the range of 55 to 85 mg/m3. Particle formation was found to increase at a relative humidity of approximately 20% and higher. Variations in the initial number of particles present did not appear to have a significant effect on the particle formation, suggesting that nucleation was not a controlling factor under these conditions. However, tests in a commercial environment at much lower VOC concentrations and lower UV fluence rates showed no detectable PM2.5 formation, indicating that SOA formation during the intermittent use of germicidal UV may not significantly affect indoor air quality under normal conditions.

scholarly journals Formation of Secondary Organic Aerosols by Germicidal Ultraviolet Light

2018 ◽  
Author(s):  
Eureka Choi ◽  
Zhongchao Tan ◽  
William A. Anderson
Keyword(s):  
Uv Light ◽  
Fine Particulate Matter ◽  
Particle Formation ◽  
Uv Exposure ◽  
Indoor Environments ◽  
Fine Particulate ◽  
Volatile Organic ◽  
Solar Uv ◽  
Commercial Environment ◽  
Number Of Particles

Ultraviolet (UV) light with a wavelength of 254 nm has proven to be effective at inactivating microorganisms, and thus has been increasingly employed as a method of disinfection for indoor environments. Solar UV wavelengths (300 to 400 nm) are known to initiate the formation of secondary organic aerosol (SOA) particles from photo-oxidation of volatile organic compounds in the atmosphere, but germicidal wavelengths have not been extensively studied for indoor environments.  In this work, toluene was exposed to 254 nm UV light in a laboratory photoreactor, with varying conditions of the air, the duration of UV exposure, and the duration of post-UV time. The number of particles formed in the fine particulate matter (PM2.5) size range was measured, and significant levels of particle formation were observed for UV exposure periods of as short as 5 minutes. The particle formation ranged from 2.4x106 particles/m3 for 5 minutes of UV exposure, to 1449.8x106 particles/m3 for 15 minutes of UV exposure. Particle formation was found to increase with increasing concentrations of gas phase toluene, and at relative humidity of approximately 20% and higher. Variations in the initial number of particles present did not appear to have a significant effect on the particle formation, suggesting that nucleation was not a controlling factor. However, tests in a commercial environment showed no significant detectable PM2.5 formation, indicating that SOA formation during the intermittent use of germicidal UV may not significantly affect indoor air quality.

scholarly journals Anthropogenic enhancements to production of highly oxygenated molecules from autoxidation

2019 ◽  
Vol 116 (14) ◽  
pp. 6641-6646 ◽  
Author(s):  
Havala O. T. Pye ◽  
Emma L. D’Ambro ◽  
Ben H. Lee ◽  
Siegfried Schobesberger ◽  
Masayuki Takeuchi ◽  
...  
Keyword(s):  
Fine Particulate Matter ◽  
Peroxy Radicals ◽  
Dominant Component ◽  
Fine Particulate ◽  
Biogenic Voc ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Climate Interactions ◽  
Urban Plume

Atmospheric oxidation of natural and anthropogenic volatile organic compounds (VOCs) leads to secondary organic aerosol (SOA), which constitutes a major and often dominant component of atmospheric fine particulate matter (PM2.5). Recent work demonstrates that rapid autoxidation of organic peroxy radicals (RO2) formed during VOC oxidation results in highly oxygenated organic molecules (HOM) that efficiently form SOA. As NOxemissions decrease, the chemical regime of the atmosphere changes to one in which RO2autoxidation becomes increasingly important, potentially increasing PM2.5, while oxidant availability driving RO2formation rates simultaneously declines, possibly slowing regional PM2.5formation. Using a suite of in situ aircraft observations and laboratory studies of HOM, together with a detailed molecular mechanism, we show that although autoxidation in an archetypal biogenic VOC system becomes more competitive as NOxdecreases, absolute HOM production rates decrease due to oxidant reductions, leading to an overall positive coupling between anthropogenic NOxand localized biogenic SOA from autoxidation. This effect is observed in the Atlanta, Georgia, urban plume where HOM is enhanced in the presence of elevated NO, and predictions for Guangzhou, China, where increasing HOM-RO2production coincides with increases in NO from 1990 to 2010. These results suggest added benefits to PM2.5abatement strategies come with NOxemission reductions and have implications for aerosol–climate interactions due to changes in global SOA resulting from NOxinteractions since the preindustrial era.

scholarly journals Changes in outdoor air pollution due to COVID-19 lockdowns differ by pollutant: evidence from Scotland

2020 ◽  
Vol 77 (11) ◽  
pp. 798-800 ◽  
Author(s):  
Ruaraidh Dobson ◽  
Sean Semple
Keyword(s):  
Air Pollution ◽  
Motor Vehicle ◽  
Fine Particulate Matter ◽  
Personal Exposure ◽  
Indoor Environments ◽  
Similar Data ◽  
Outdoor Air ◽  
Fine Particulate ◽  
Hourly Data ◽  
The Impact

ObjectivesTo examine the impact of COVID-19 lockdown restrictions in March/April 2020 on concentrations of nitrogen dioxide (NO2) and ambient fine particulate matter (PM2.5) air pollution measured at roadside monitors across Scotland by comparing data with previous years.MethodsPublicly available data of PM2.5 concentrations from reference monitoring systems at sites across Scotland were extracted for the 31-day period immediately following the imposition of lockdown rules on 23 March 2020. Similar data for 2017, 2018 and 2019 were gathered for comparison. Mean period values were calculated from the hourly data and logged values compared using pairwise t-tests. Weather effects were corrected using meteorological normalisation.ResultsNO2 concentrations were significantly lower in the 2020 lockdown period than in the previous 3 years (p<0.001). Mean outdoor PM2.5 concentrations in 2020 were much lower than during the same period in 2019 (p<0.001). However, despite UK motor vehicle journeys reducing by 65%, concentrations in 2020 were within 1 µg/m3 of those measured in 2017 (p=0.66) and 2018 (p<0.001), suggesting that traffic-related emissions may not explain variability of PM2.5 in outdoor air in Scotland.ConclusionsThe impact of reductions in motor vehicle journeys during COVID-19 lockdown restrictions may not have reduced ambient PM2.5 concentrations in some countries. There is also a need for work to better understand how movement restrictions may have impacted personal exposure to air pollutants generated within indoor environments.

scholarly journals A Prototype Sensor for In Situ Sensing of Fine Particulate Matter and Volatile Organic Compounds

Sensors ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 265 ◽  
Author(s):  
Chee-Loon Ng ◽  
Fuu-Ming Kai ◽  
Ming-Hui Tee ◽  
Nicholas Tan ◽  
Harold Hemond
Keyword(s):  
Particulate Matter ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Fine Particulate Matter ◽  
Fine Particulate ◽  
Volatile Organic ◽  
In Situ Sensing

scholarly journals Health & Environmental Impact of Ultraviolet Radiation Exposure used in Currency Sanitizer

2021 ◽  
Vol 9 (VI) ◽  
pp. 1695-1697
Author(s):  
Er. S. K. Mude
Keyword(s):  
Uv Light ◽  
Aluminum Foil ◽  
Hazardous Materials ◽  
Uv Exposure ◽  
Uv Disinfection ◽  
Volatile Organic ◽  
Light Rays ◽  
Ultraviolet Radiation Exposure ◽  
Uv C ◽  
By Products

Many of the ultraviolet (UV) sources used emit high intensities of UV light, capable of producing painful eye and skin burns. This paper provides information about the hazards associated with UV exposure and the safety precautions to take when working with these sources. Ultraviolet (UV) disinfection technology has existed for many years, but chemicals are still very prominent in disinfection applications today. UV disinfection does, however, provide many benefits over chemical options. It cannot be overdosed, and does not produce by-products, toxins, or volatile organic compound (VOC) emissions. It does not require the storage of hazardous materials and will not affect smell or taste in water and food disinfection applications. In addition, UV light is known to kill more waterborne microbes than chlorination. UV-C currency sanitizer is a fluid less device which can be used to perform the disinfection of various bacteria and viruses, it is based on UV-C light technology. It provides a portable ultraviolet disinfecting device for currency notes which comprises an acrylic case. The light is arranged in the top and bottom and inner layer coated with aluminum foil to increase the utilization of light rays.

scholarly journals Field evaluation of a low-cost indoor air quality monitor to quantify exposure to pollutants in residential environments

2018 ◽  
Vol 7 (1) ◽  
pp. 373-388 ◽  
Author(s):  
Alejandro Moreno-Rangel ◽  
Tim Sharpe ◽  
Filbert Musau ◽  
Gráinne McGill
Keyword(s):  
Particulate Matter ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Low Cost ◽  
Fine Particulate Matter ◽  
Total Volatile ◽  
Fine Particulate ◽  
Volatile Organic ◽  
Temporal And Spatial ◽  
Total Volatile Organic Compounds

Abstract. Measurements of temporal and spatial changes to indoor contaminant concentrations are vital to understanding pollution characteristics. Whilst scientific instruments provide high temporal resolution of indoor pollutants, their cost and complexity make them unfeasible for large-scale projects. Low-cost monitors offer an opportunity to collect high-density temporal and spatial data in a broader range of households. This paper presents a user study to assess the precision, accuracy, and usability of a low-cost indoor air quality monitor in a residential environment to collect data about the indoor pollution. Temperature, relative humidity, total volatile organic compounds (tVOC), carbon dioxide (CO2) equivalents, and fine particulate matter (PM2.5) data were measured with five low-cost (“Foobot”) monitors and were compared with data from other monitors reported to be scientifically validated. The study found a significant agreement between the instruments with regard to temperature, relative humidity, total volatile organic compounds, and fine particulate matter data. Foobot CO2 equivalent was found to provide misleading CO2 levels as indicators of ventilation. Calibration equations were derived for tVOC, CO2, and PM2.5 to improve sensors' accuracy. The data were analysed based on the percentage of time pollutant levels that exceeded WHO thresholds. The performance of low-cost monitors to measure total volatile organic compounds and particulate matter 2.5 µm has not been properly addressed. The findings suggest that Foobot is sufficiently accurate for identifying high pollutant exposures with potential health risks and for providing data at high granularity and good potential for user or scientific applications due to remote data retrieval. It may also be well suited to remote and larger-scale studies in quantifying exposure to pollutants.

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