Budgets for nocturnal VOC oxidation by nitrate radicals aloft during the 2006 Texas Air Quality Study

Nighttime oxidation by either O₃ or NO₃ removes these VOCs. This paper presents a regional analysis of nighttime P-3 flights during the 2006 Texas Air Quality Study (TexAQS) to quantify the loss rates and budgets for both NO₃ and highly reactive VOC.

Mixing ratios and production rates of NO₃ were large, up to 400 parts per trillion by volume (pptv) and 1-2 parts per billion by volume (ppbv) per hour, respectively. Budgets for NO₃ show that it was lost primarily to reaction with VOCs, with the sum of anthropogenic VOCs (30-54%) and isoprene (10-50%) being the largest contributors. Indirect loss of NO₃ to N₂O₠hydrolysis was of lesser importance (14-28%) but was the least certain due to uncertainty in the aerosol uptake coefficient for N₂O₠.