While
several scientific studies have linked PM2.5 to
decreased lung function, there is still some degree of uncertainty
regarding which particulate physicochemical properties are most harmful.
We followed a panel of 57 healthy schoolchildren (857 person-days)
to investigate the associations between a wide variety of PM2.5 and lung function in Heshan, China in 2016 for three periods. We
monitored the daily concentrations of mass, chemical composition,
size, number, surface area, and volume of particulate mixture. Associations
of lung function with various particle metrics were estimated using
generalized estimating equations and unconstrained distributed lag
models. Random forest model was used to compare the relative importance
of exposure metrics. Immediate (lag 0) associations of PM2.5 and carbonaceous aerosols with reduced FEV1 and MMEF,
and accumulation-mode particles with FEV1 were found. Slightly
delayed (lag 1, 2) effects on PEF were particularly prominent for
Aitken-mode particles. Possible cumulative (lags 0–2) effects
of PM2.5 and carbonaceous aerosols on PEF and Aitken-mode
particles on FEV1, MMEF, and PEF were observed. This study
provides comprehensive evidence that the physicochemical properties
of particulate mixtures are associated with reduced lung function
in children. Organic carbon (OC) may be an important risk factor for
the decreased lung function related to PM exposure.
Water-soluble ions such as sulfate may have great impacts on atmospheric pollution. To determine the deposition effect of PM 2.5 sulfates, the major PM 2.5 constituents, in the forest canopy in Beijing, China, an investigation was carried out in an urban forest, Olympic Forest Park, and a suburban forest, Jiufeng National Forest Park. We measured the vertical distributions of sulfate by using monitoring towers in the two forests at the same times in March and May 2013. Sulfate (SO 4 2− )was predominant in all PM 2.5 water-soluble inorganic ions, with a proportion >40%. The vertical concentration of SO 4 2− increased with height, and the average sulfate concentration in Olympic ForestPark was higher than that in Jiufeng National Forest Park. Results also revealed that meteorological conditions had significant impacts on both the sulfate concentration and the deposition velocity. In winter, the deposition of SO 4 2− through the canopy was not obvious in the two forest parks, which was quite the opposite in spring. The deposition velocity in the daytime was higher than that in the nighttime in both Olympic Forest Park (0.9 ± 1.0 cm/s vs. 0.4 ± 0.3 cm/s) and Jiufeng National Forest Park (1.3 ± 1.2 cm/s vs. 0.8 ± 0.8 cm/s). While Jiufeng National Forest Park turned out to have a higher average sulfate deposition velocity than Olympic Forest Park.
Each year, according to Chinese and European statistics, there are many serious injuries and even fatalities of travelers into subway transit stations. Consequently, it becomes more and more important for transit authorities to evaluate these facilities (platform, gates, stairs, escalators, etc.) under critical traffic conditions, such as rush hours or emergency situations. The purpose of this paper is to review existing research results, develop the main Framework of station capacity assessment and finally point out the key issues of subway station capacity assessment.
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