OH, HO.sub.2, and RO.sub.2 radical chemistry in a rural forest environment: measurements, model comparisons, and evidence of a missing radical sink

The hydroxyl (OH), hydroperoxy (HO.sub.2 ), and organic peroxy (RO.sub.2) radicals play important roles in atmospheric chemistry. In the presence of nitrogen oxides (NO.sub.x ), reactions between OH and volatile organic compounds (VOCs) can initiate a radical propagation cycle that leads to the production of ozone and secondary organic aerosols. Previous measurements of these radicals under low-NO.sub.x conditions in forested environments characterized by emissions of biogenic VOCs, including isoprene and monoterpenes, have shown discrepancies with modeled concentrations.