The pollution characteristics of PM10 and PM2.5 during summer and winter in Beijing, Suning and Islamabad

To understand the atmospheric particulate pollution characteristics of cities in different sizes and regions, PM10 and PM2.5 were simultaneously collected in three cities: Beijing, China, Islamabad, Pakistan and Suning, China, in summer (2016) and winter (2017), respectively. The associated species including carbonaceous, metal elements and water soluble ions were analyzed. Both PM10 and PM2.5 concentrations in winter are higher than those in summer in three cities. In Beijing, OM, NH4NO3 and (NH4)(2)SO4 are the main components, the PM2.5/PM10 ratio is the highest among three cities, and the NO3-/SO42- ratio is lower than that in Islamabad in winter, suggesting that coal-fired process contributed more in Beijing. In Islamabad, the main components of PM10 and PM2.5 are crust and OM. The average concentrations of both Ca and Na in PM10 are higher than those in Beijing and Suning, indicating that the soil dust may be one of main air pollution sources in Islamabad. The concentrations of OC in both PM10 and PM2.5 in Islamabad are in relatively high level in summer, which indicates that more secondary organic aerosols are formed in summer in Islamabad. The highest PM10 and PM2.5 concentrations occur in Suning and the chemical composition of PM2.5 in Suning is similar to that in Beijing whether it is summer or winter, and the proportion of EC in Suning is higher than that in the other two cities in both PM10 and PM2.5, which are attributed to atmospheric pollutants transport from the surrounding cities and the diesel vehicle emission.