The Behavior of the Hydroxyl and Hydroperoxyl Radicals During TexAQS2000

Biogenic emissions strongly influence the behavior of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) in a forest that is distant from urban areas. The mixing ratios of OH and HO2 and the OH reactivity were measured as part of the multi-investigator study, PROPHET2000, which took place at the University of Michigan Biological Station near Pellston Michigan in June and July 2000. Both OH and HO2 show diurnal behavior, although HO2 and especially OH are greater that expected at night. The OH reactivity is highly variable from day to day, with values ranging from 20 s^-1 during some days to 2 s^-1 at night. This strong diurnal variation was not seen in Nashville in summer 1999, where nighttime OH reactivity tended to be greater during the night than during the day. OH, HO2, and the OH reactivity all appear to correlate with O3 and temperature, both day and night. The implications of these observations will be discussed.