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Direct Measurements of HO x Radicals in the Marine Boundary Layer: Testing the Current Tropospheric Chemistry Mechanism
Author(s) -
Kanaya Yugo,
Akimoto Hajime
Publication year - 2002
Publication title -
the chemical record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.61
H-Index - 78
eISSN - 1528-0691
pISSN - 1527-8999
DOI - 10.1002/tcr.10019
Subject(s) - radical , troposphere , chemistry , atmospheric chemistry , ozone , boundary layer , photodissociation , photochemistry , hydroxyl radical , daytime , atmospheric sciences , meteorology , environmental chemistry , organic chemistry , thermodynamics , geology , physics
OH and HO 2 radicals, atmospheric detergents, and the reservoir thereof, play central roles in tropospheric chemistry. In spite of their importance, we had no choice but to trust their concentrations predicted by modeling studies based on known chemical processes. However, recent direct measurements of these radicals have enabled us to test and revise our knowledge of the processes by comparing the predicted and observed values of the radical concentrations. We developed a laser‐induced fluorescence (LIF) instrument and successfully observed OH and HO 2 at three remote islands of Japan (Oki Island, Okinawa Island, and Rishiri Island). At Okinawa Island, the observed daytime level of HO 2 agreed closely with the model estimates, suggesting that the photochemistry at Okinawa is well described by the current chemistry mechanism. At Rishiri Island, in contrast, the observed daytime level of HO 2 was consistently much lower than the calculated values. We proposed that iodine chemistry, usually not incorporated into the mechanism, is at least partly responsible for the discrepancy in the results. At night, HO 2 was detected at levels greater than 1 pptv at all three islands, suggesting the presence of processes in the dark that produce radicals. We showed that ozone reactions with unsaturated hydrocarbons, including monoterpenes, could significantly contribute to radical production. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 199–211, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10019