Temporal and Spatial Distribution Characteristics of PM2.5 in Chongqing Urban Areas

To explore the diurnal and seasonal characteristics of PM25, hourly PM25 concentration data ol It tixed monitoring sites in Chongqing urban area were collected continuously from June 2014 to May 2015. The result showed that: (1) the seasonal concentration of PM2.5 in different seasons decreased in the order of winter, autumn, spring and summer (P < 0.05), which were 100.2 microg x m(-3), 66.1 microg x m(-3), 45.9 microg x m(-3) and 33.4 microg x m(-3), respectively. (2) Monthly average concentrations of PM2.5 showed a single-peak curve, and the peaks of which occurred in January (P < 0.05, 120.8 microg x m(-3)). (3) For the whole year, daily variation of PM2.5 showed a jaggies curve. (4) Diurnal average concentrations of PM2.5 showed an obviously bimodal curve in winter, autumn and spring, hut it was less obvious in summer. (5) Daily PM25 concentration was significantly positively correlated with SO2, NO2 and CO (P < 0.01), indicating that the concentrations of SO2, NO2 and CO had a significant impact on the concentration of