Direct quantification of OH recycling rates from a comprehensive measurement suite during the BEACHON-ROCS field campaign

In the past few years, unexpectedly higher hydroxyl radical levels have been reported from several field studies conducted in regions where BVOCs contribute a dominant portion of the chemical loss of OH. Considering the fast reaction rates of BVOC with OH, the processes controlling inside canopy oxidation of BVOCs and their impacts on regional photochemistry need to be revisited. The chemical mechanisms governing OH chemistry is of interest not only to the atmospheric chemistry but also to the biogeochemistry community due to the biosphere-atmosphere coupling through BVOCs and OH. One of the main hypotheses to explain higher levels of OH in BVOC dominated regions is the recycling of OH from the reactions of HO2 with organic peroxy radicals. Especially, peroxy radicals from isoprene oxidation by OH have been speculated to yield 2-3 OH molecules. However, no mechanistic chemical explanation has been postulated. During the BEACHON-ROCS field campaign in August 2010, a comprehensive instrumentation suite including OH, HO2, RO2, VOCs, NOx, CO, OH reactivity etc was deployed at the Manitou Forest Observatory (Woodland Park, CO). The data set provides us with an unique opportunity to constrain production and loss rates of OH so that we can directly deduce OH recycling rates from HO2. We will present the measurement dataset and calculated recycling rates and discuss their potential impacts on the oxidation capacity inside a forest canopy especially in context of a 2-methyl-3-butene-2-ol and monoterpene dominated ecosystem.