The pollution levels of BTEX and carbonyls under haze and non-haze days in Beijing, China

Abstract

The North China Plain including Beijing is frequently suffering from serious haze days in recent years. To best recognize the influence of haze days on regional air quality, the pollution levels of deleterious gases of BTEX (benzene, toluene, ethylbenzene, m,p-xylene and o-xylene) and carbonyls (formaldehyde, acetaldehyde and acetone) under haze and non-haze days were contrastively investigated during the period of September 2008-August 2010 in Beijing. In comparison with non-haze days, remarkable enhancement of BTEX and the carbonyls under haze days in winter was found, with enhancement factors of 1.9-5.7 for BTEX and of 1.5-4.2 for the carbonyls. Whereas the enhancement factors for both BTEX (1.0-3.0) and the carbonyls (1.2-1.9) under haze days in summer were relatively small. The ratios of each BTEX to CO under both haze days and non-haze days exhibited a minimal value in the afternoon, whereas maximal values for the ratios of the carbonyls to CO were usually found in the afternoon. The ratios of each BTEX to CO were extremely greater under haze days than those under non-haze days in winter, but no evident difference was found in summer. The ratios of each carbonyl under both haze days and non-haze days in summer were at least a factor of 2 greater than those in winter and only enhancement of the ratios under haze days was found in winter. The remarkably higher ratios of ethylbenzene to m,p-xylene under haze days than non-haze days in both winter and summer revealed high reactivity of photochemical reactions initiated by OH radicals under haze days.

Hierarchical electrospun nanofibers treated by solvent vapor annealing as air filtration mat for high-efficiency PM2.5 capture

“…The burning smoke contained PM2.5 above 270 µg m −3 , and the smoke had a very complex composition that included CO, CO 2 , and certain volatile organic compounds, such as benzene, alcohols, amines, phenols, and long-chain hydrocarbons [49][50][51][52][53]. This smoke had a composition similar to that of common haze, so it can be used as a model to simulate haze in the laboratory [54,55]. The current environmental PM2.5 concentration was recorded, and then the nanofiber mat was fixed with a rubber band on the PM2.5 mask filtration efficiency measuring device, with count data collected every 5 s with a total test time of 90 s. To ensure the accuracy of the results, each sample was tested 5 times and averaged.…”

Contribution of Hydroxymethane Sulfonate to Ambient Particulate Matter: A Potential Explanation for High Particulate Sulfur During Severe Winter Haze in Beijing

“…HMS would also form in aerosol water; however, since aerosol liquid water content is usually multiple orders of magnitude less than cloud liquid water content, formation of HMS in aerosol water should be insignificant as long as clouds occasionally appear. The high levels of HCHO necessary for HMS formation have been observed in Beijing in winter (Y. Zhang et al, ; Rao et al, ). For example, mean HCHO in winter 2014 was 5.51 ± 3.90 ppb, with peak concentrations of 14–17 ppb (Rao et al, ).…”

Aromatic Hydrocarbons in Urban and Suburban Atmospheres in Central China: Spatiotemporal Patterns, Source Implications, and Health Risk Assessment

“…Toluene, C 8 and C 9 AHs were also observed to be the lowest in summer. Ambient AH levels strongly depend on meteorological conditions [70][71][72]. It was found that the wind speed in summer was much higher (p < 0.01) compared to other seasons and the boundary layer height was relatively high in summer (Table S3).…”