123 research outputs found
Development of a detailed chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons
In-vehicle exposure to NO2 and PM2.5:A comprehensive assessment of controlling parameters and reduction strategies to minimise personal exposure
Vehicles are the third most occupied microenvironment, other than home and workplace, in developed urban areas. Vehicle cabins are confined spaces where occupants can mitigate their exposure to on-road nitrogen dioxide (NO2) and fine particulate matter (PM2.5) concentrations. Understanding which parameters exert the greatest influence on in-vehicle exposure underpins advice to drivers and vehicle occupants in general. This study assessed the in-vehicle NO2 and PM2.5 levels and developed stepwise general additive mixed models (sGAMM) to investigate comprehensively the combined and individual influences of factors that influence the in-vehicle exposures. The mean in-vehicle levels were 19 ± 18 and 6.4 ± 2.7 μg/m3 for NO2 and PM2.5, respectively. sGAMM model identified significant factors explaining a large fraction of in-vehicle NO2 and PM2.5 variability, R2 = 0.645 and 0.723, respectively. From the model's explained variability on-road air pollution was the most important predictor accounting for 22.3 and 30 % of NO2 and PM2.5 variability, respectively. Vehicle-based predictors included manufacturing year, cabin size, odometer reading, type of cabin filter, ventilation fan speed power, window setting, and use of air recirculation, and together explained 48.7 % and 61.3 % of NO2 and PM2.5 variability, respectively, with 41.4 % and 51.9 %, related to ventilation preference and type of filtration media, respectively. Driving-based parameters included driving speed, traffic conditions, traffic lights, roundabouts, and following high emitters and accounted for 22 and 7.4 % of in-vehicle NO2 and PM2.5 exposure variability, respectively. Vehicle occupants can significantly reduce their in-vehicle exposure by moderating vehicle ventilation settings and by choosing an appropriate cabin air filter
Investigation of vehicle cold start primary NO2 emissions inferred from ambient monitoring data in the UK and their implications for urban air quality
NO2 levels inside vehicle cabins with pollen and activated carbon filters::A real world targeted intervention to estimate NO2 exposure reduction potential
Traffic related nitrogen dioxide (NO2) poses a serious environmental and health risk factor in the urban environment. Drivers and vehicle occupants in general may have acute exposure to NO2 levels. In order to identify key controllable measures to reduce vehicle occupant's exposure, this study measures NO2 exposure inside ten different vehicles under real world driving conditions and applies a targeted intervention by replacing previously used filters with new standard pollen and new activated carbon cabin filters. The study also evaluates the efficiency of the latter as a function of duration of use. The mean in-vehicle NO2 exposure across the tested vehicles, driving the same route under comparable traffic and ambient air quality conditions, was 50.8 ± 32.7 μg/m3 for the new standard pollen filter tests and 9.2 ± 8.6 μg/m3 for the new activated carbon filter tests. When implementing the new activated carbon filters, overall we observed significant (p < 0.05) reductions by 87 % on average (range 80 - 94.2 %) in the in-vehicle NO2 levels compared to the on-road concentrations. We further found that the activated carbon filter NO2 removal efficiency drops by 6.8 ± 0.6 % per month; showing a faster decay in removal efficiency after the first 6 months of use. These results offer novel insights into how the general population can control and reduce their exposure to traffic related NO2. The use and regular replacement of activated carbon cabin air filters represents a relatively inexpensive method to significantly reduce in-vehicle NO2 exposure
60 years of UK visibility measurements:Impact of meteorology and atmospheric pollutants on visibility
Reduced visibility is an indicator of poor air quality. Moreover, degradation
in visibility can be hazardous to human safety; for example, low visibility
can lead to road, rail, sea and air accidents. In this paper, we explore the
combined influence of atmospheric aerosol particle and gas characteristics,
and meteorology, on long-term visibility. We use visibility data from eight
meteorological stations, situated in the UK, which have been running since
the 1950s. The site locations include urban, rural and marine environments.<br><br>
Most stations show a long-term trend of increasing visibility, which is
indicative of reductions in air pollution, especially in urban areas.
Additionally, the visibility at all sites shows a very clear dependence on
relative humidity, indicating the importance of aerosol hygroscopicity on the
ability of aerosol particles to scatter radiation. The dependence of
visibility on other meteorological parameters, such as wind speed and wind
direction, is also investigated. Most stations show long-term increases in
temperature which can be ascribed to climate change, land-use changes (e.g.
urban heat island effects) or a combination of both; the observed effect is
greatest in urban areas. The impact of this temperature change upon local
relative humidity is discussed.
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To explain the long-term visibility trends and their dependence on
meteorological conditions, the measured data were fitted to a newly developed
light-extinction model to generate predictions of historic aerosol and gas
scattering and absorbing properties. In general, an excellent fit was
achieved between measured and modelled visibility for all eight sites. The
model incorporates parameterizations of aerosol hygroscopicity, particle
concentration, particle scattering, and particle and gas absorption. This new
model should be applicable and is easily transferrable to other data sets
worldwide. Hence, historical visibility data can be used to assess trends in
aerosol particle properties. This approach may help constrain global model
simulations which attempt to generate aerosol fields for time periods when
observational data are scarce or non-existent. Both the measured visibility
and the modelled aerosol properties reported in this paper highlight the
success of the UK's Clean Air Act, which was passed in 1956, in cleaning the
atmosphere of visibility-reducing pollutants.</p
Kinetics of stabilised Criegee intermediates derived from alkene ozonolysis: reactions with SO2, H2O and decomposition under boundary layer conditions
The removal of SO2in the presence ofcis-but-2-ene and ozone exhibits a strong dependence on the water vapour concentration.</p
Development of a detailed chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons
Evidence for renoxification in the tropical marine boundary layer
We present 2 years of NOx observations from the Cape Verde Atmospheric Observatory located in the tropical Atlantic boundary layer. We find that NOx mixing ratios peak around solar noon (at 20-30pptV depending on season), which is counter to box model simulations that show a midday minimum due to OH conversion of NO2 to HNO3. Production of NOx via decomposition of organic nitrogen species and the photolysis of HNO3 appear insufficient to provide the observed noontime maximum. A rapid photolysis of nitrate aerosol to produce HONO and NO2, however, is able to simulate the observed diurnal cycle. This would make it the dominant source of NOx at this remote marine boundary layer site, overturning the previous paradigm according to which the transport of organic nitrogen species, such as PAN, is the dominant source. We show that observed mixing ratios (November-December 2015) of HONO at Cape Verde (∼ 3.5pptV peak at solar noon) are consistent with this route for NOx production. Reactions between the nitrate radical and halogen hydroxides which have been postulated in the literature appear to improve the box model simulation of NOx. This rapid conversion of aerosol phase nitrate to NOx changes our perspective of the NOx cycling chemistry in the tropical marine boundary layer, suggesting a more chemically complex environment than previously thought
Ambient air quality monitoring for healthcare settings
Key messages 1. Air quality monitoring at healthcare sites can help understand exposure levels, identify local pollution sources, and inform targeted actions to reduce staff and patient exposure to poor air quality. 2. Air pollutant levels may be measured using diffusion tubes (nitrogen dioxide) and air quality sensors (particulate matter). 3. Appropriate planning and technical support/expert advice for healthcare site monitoring can help ensure that the air quality data generated are useful and usable
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