This exploratory project involves development and initial field testing of a new instrument employing the LOng Path Absorption Photometry (LOPAP) method to measure nitrous and nitric acids in air. Both acids are oxidation products of nitrogen oxides. Nitrous acid is thought to be, under some conditions, a significant source of hydroxyl radical, the most important atmospheric oxidant. Deposition of nitric acid is responsible for much of the removal of oxidized inorganic nitrogen from the troposphere. Field testing during a multi-investigator study focusing on biogenic emissions and their effects on atmospheric chemistry in Blodgett Forest, California in summer 2009 (BEARPEX-09) will include investigation of potential interferences in the measurements via side-by-side comparison with a method based on a different principle. Previous field intercomparisons of nitrous acid measurement methods in high-altitude and polar environments yielded differing results, suggesting that measurement artifacts exist and that they may be site dependent. The large array of data for other trace gases and aerosol composition to be obtained during BEARPEX will allow detailed examination of possible HONO measurement artifacts and their causes in the very different forest environment. Broader impacts will include better understanding of the chemistry of these two acids and, in turn, better understanding of atmospheric oxidation chemistry and radical budgets. One graduate and two undergraduate students will be trained through participation in the project. This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
