Spatial and Temporal Variability of the PM_(2.5)/PM_(10) Ratio in Wuhan, Central China

Gang Xu ； Limin Jiao ； Boen Zhang ； Suli Zhao ； Man Yuan ； Yanyan Gu ； Jiafeng Liu ； Xin Tang

《Aerosol and Air Quality Research》 17卷3期 (2017/03) Pp. 741-751

https://doi.org/10.4209/aaqr.2016.09.0406

摘要

Fine particles (PM_(2.5)) and coarse particles (PM_(2.5-10)) are generally produced by different sources, so the PM_(2.5)/PM_(10) ratio reveals characteristics of particle pollution. The ratio can be used to characterize the underlying atmospheric processes and evaluate historical PM_(2.5) pollution in absence of direct measurements. However, application of the ratio needs its varying pattern because PM concentrations change significantly at time and space. Hourly PM_(2.5) and PM_(10) observations at nine monitoring sites in urban area (Urban-sites) and one remote Background-site in Wuhan in 2013-2015 were collected to investigate both long-term, short-term temporal variation and spatial distribution, spatial disparity of the ratio at a city scale. The results show that annual average PM_(2.5)/PM_(10) ratio is 0.62 at Urban-sites and 0.68 at Background-site with apparent seasonal, monthly and daily variations. The ratio reaches the maximum in winter because of stable atmospheric conditions. There are apparent night-day differences of daily variation of the ratio, which increases at night in all seasons in consequence of temperature inversion and declines in the daytime with a moderate rise in the afternoon. We find obvious spatial gradients of the ratio that gradually increases from urban core to urban fringe and to suburban. This study provides further insights to the spatio-temporal variability of PM_(2.5)/PM_(10) ratio. The evidence indicates that the variability of PM_(2.5)/PM_(10) should be noticed in its applications.

關鍵字

Air pollution ； Particulate matter ； Ratio ； Spatio-temporal variability ； China