3. The hourly data were averaged according to the time of the day to provide 24-value patterns, which give information about a type of sources: mobile sources tend to peak during rush hours, i.e., morning and evening peaks during weekdays, industrial sources during office hours, and secondary pollutants react pollutants react differently with respect to the solar radiation. The hourly data were also average according to the month to provide 12-value seasonal patterns, which gives information about the type of sources: urban sources tend to increase at winter time due to residential heating systems, whereas industrial sources usually do not. In this step, the t-test and correlation analysis were used to confirm significant variations of CAPs.