Nitrous acid (HONO) during polar spring in Barrow, Alaska: A net source of OH radicals?

HONO concentrations between ≤ 0.4 pptv (DL) and ∼500 pptv were measured. The very high concentrations observed on several days were caused by local direct emissions and were highly correlated with the NOx and CO data.

When only "clean days" were considered, average HONO concentrations varied between ≤ 0.4 - 10 pptv. Average HONO/NOx and HONO/NOy ratios of ∼6% and ∼1% were observed, respectively, in good agreement with other remote LOPAP measurement data, but lower than measured in most other polar regions by other methods. The strong correlation between sharp peaks of OH and HONO during daytime, which was not observed for any other measured radical precursor, suggested that HONO photolysis was a major source of OH radicals in Barrow.