On the weather page of the Mail Tribune there is an air quality index which shows the amount of particulates of the previous day. I keep a daily record of these findings. I am perplexed, however, by the different readings over the weekend. For example on one Saturday, Jan. 26, the reading was for 79, the next day it was 26, and then Monday it was 21. This happens every single weekend. Can you please find out and explain?

On the weather page of the Mail Tribune there is an air quality index which shows the amount of particulates of the previous day. I keep a daily record of these findings. I am perplexed, however, by the different readings over the weekend. For example on one Saturday, Jan. 26, the reading was for 79, the next day it was 26, and then Monday it was 21. This happens every single weekend. Can you please find out and explain?

— Louis J., Phoenix

Your conclusion piqued our interest, Louis, but we're not sure how you arrived at it. We got a printout of the January air quality index readings from the Oregon Department of Environmental Quality. On three of the weekends this month, your conclusion appears to hold water. But on Friday, Jan. 19, the reading hit 78, then spiked to 88 on Saturday and settled back to 77 on Sunday.

We asked John Becker with the DEQ to see if they had noticed any trends that would support your conclusion. He said the DEQ hasn't found any specific weekend pattern. He said the readings vary from day-to-day based on weather conditions, woodstove smoke and other human activities that add pollutants into the air. A storm front will blow through like it did last weekend clearing out the air in the valley, he said. Nights that are cold with stagnant air will drive up the pollutants because of woodstove smoke.

Anyway, Louis, keep checking those numbers. We would suggest tracking them for about a year to see if any real patterns emerge.

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