The vertical numbers on the left show the density of particles that are smaller than 2.5. The horizontal numbers are the 15-minute time averages through out the day. Take your finger and follow the green line to see how the pollution builds up at night. When you follow the red line for the weekend, you see the traffic bulge isn't there in the morning, but by 5:30 PM (17:30) the red line rises from the lowest level of the week to the highest level of the week, on the chart. The highest pollution occurs at late night around 11 PM. Weekends are higher that weekdays.
Here we see time-average curves which are compiled by taking the data collected over a period of about 3 months in the winter of 1992-93 and then separating the data into weekdays and Sundays-holidays. The averages each time period was generated for weekdays and days that were Sundays or holidays and were plotted in the graph. The most striking feature from this data is that the shape of the two curves were very similar. This indicates that the particulate production could not have been importantly influenced by traffic. There are no important rush hour peaks on the week ends such as would be expected on weekdays (Ott). Also the maginitude of the evening peak is in the Sunday-holiday curve suggesting a recreational activity such as sitting in front of a fire. Notice how the evening peak is later on weekdays indicating how the activity waits until after people arrive home.
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