Environmental pollution
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Environmental pollution · Nov 2016
Overestimation of on-road air quality surveying data measured with a mobile laboratory caused by exhaust plumes of a vehicle ahead in dense traffic areas.
The unintended influence of exhaust plumes emitted from a vehicle ahead to on-road air quality surveying data measured with a mobile laboratory (ML) at 20-40 km h-1 in dense traffic areas was investigated by experiment and life-sized computational fluidic dynamics (CFD) simulation. The ML equipped with variable sampling inlets of five columns by four rows was used to measure the spatial distribution of CO2 and NOx concentrations when following 5-20 m behind a sport utility vehicle (SUV) as an emitter vehicle equipped with a portable emission monitoring system (PEMS). The PEMS measured exhaust gases at the tailpipe for input data of the CFD simulations. ⋯ If the height of the ML inlet is lower than 2 m and the ML travels within 20 m behind a SUV and a sedan ahead at 20 km h-1, the overestimation should be considered by as much as 200 ppb in NOx and 80 ppm in CO2. Following a bus should be avoided if possible, because effect of exhaust plumes from a bus ahead could not be negligible even when the distance between the bus and the ML with the inlet height of 2 m, was more than 40 m. Recommendations are provided to avoid the unintended influence of exhaust plumes from vehicles ahead of the ML during on-road measurement in urban dense traffic conditions.
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Environmental pollution · Jan 2016
Origin of inorganic and organic components of PM2.5 in subway stations of Barcelona, Spain.
The present work assesses indoor air quality in stations of the Barcelona subway system. PM2.5 concentrations on the platforms of 4 subway stations were measured during two different seasons and the chemical composition was determined. A Positive Matrix Factorization analysis was performed to identify and quantify the contributions of major PM2.5 sources in the subway stations. ⋯ Subway PM2.5 source comprised emissions from rails, wheels, catenaries, brake pads and pantographs. The subway source showed different chemical profiles for each station, but was always dominated by Fe. Control actions on the source are important for the achievement of better air quality in the subway environment.
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Environmental pollution · Sep 2014
Ozone levels in European and USA cities are increasing more than at rural sites, while peak values are decreasing.
Ground-level ozone (O3) levels are usually lower in urban centers than nearby rural sites. To compare trends in O3 levels during the period 1990-2010, we obtained monitoring data from paired urban and rural sites from the European Environment Agency and the US Environmental Protection Agency. ⋯ The overall trend was for convergence between urban and rural O3 data. Ozone levels exceeded the criteria established for the protection of human and vegetation health at both urban and rural sites.
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Environmental pollution · Jan 2014
Influential parameters on particle concentration and size distribution in the mainstream of e-cigarettes.
Electronic cigarette-generated mainstream aerosols were characterized in terms of particle number concentrations and size distributions through a Condensation Particle Counter and a Fast Mobility Particle Sizer spectrometer, respectively. A thermodilution system was also used to properly sample and dilute the mainstream aerosol. Different types of electronic cigarettes, liquid flavors, liquid nicotine contents, as well as different puffing times were tested. ⋯ The total particle number concentration peak (for 2-s puff), averaged across the different electronic cigarette types and liquids, was measured equal to 4.39 ± 0.42 × 10(9) part. cm(-3), then comparable to the conventional cigarette one (3.14 ± 0.61 × 10(9) part. cm(-3)). Puffing times and nicotine contents were found to influence the particle concentration, whereas no significant differences were recognized in terms of flavors and types of cigarettes used. Particle number distribution modes of the electronic cigarette-generated aerosol were in the 120-165 nm range, then similar to the conventional cigarette one.
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Environmental pollution · Nov 2013
Have the short-term mortality effects of particulate matter air pollution changed in Australia over the period 1993-2007?
The author investigates whether the mortality effect of particulate matter air pollution (PM10) has changed in Australia over the period 1993-2007. This period corresponds to an era of increasing Government intervention aimed at improving air quality and, as a result, a potential decrease in the toxicity of PM10. Evidence is found that the mortality effect of PM10 has declined in both Brisbane and Sydney. ⋯ We speculate that one possible reason for this decline could be a reduction in the toxicity of PM10. A difference between this study and a similar United States study is that PM10 concentrations have not been declining in Australia. This means that the observed decline in the mortality effect of PM10 is not an artefact of a declining PM10 concentration.