Discussion Topic Background Ozone

It was accepted for a number of years in the atmospheric chemistry community that so-called "background" ozone was typically around 30-40 ppb. However, starting in the mid-1980's, a number of researchers examined the literature of a century earlier, shortly after ozone was discovered by Schonbein in 1839, and discovered several series of ozone measurements that had been made at different locations in the troposphere. Some of the papers describing this research include the papers by Bojkov (1986), Volz and Kley (1988), and Anfossi et al. (1991).

Some Points for Discussion a. What techniques were used for measuring ozone in the nineteenth century? What were the likely interferences and/or parameters that could affect the results and how serious were they likely to be?

b. At what locations were measurements made for a period of years?

c. Given the potential interferences, what are the typical levels of tropospheric 03 in the nineteenth century?

d. Given typical tropospheric 03 levels today, discuss possible causes for the increase.

e. Name as many impacts as you can think of that might be associated with this increase in 03 on a global basis. Be sure to include effects on the chemistry of the atmosphere as well as effects on health, global change, etc.

f. Some of the ozone levels reported in these papers are in mPa. What is 1 mPa in the more commonly used units of ppb? (See Chapter 2 for a discussion of units and conversions.)

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