Observations of HONO at the South Pole during ANTCI

Observations of nitrous acid (HONO) at the South Pole taken during the Antarctic Troposphere Chemistry Investigation (ANTCI) are presented. ANTCI took place in November and December of 2003. The photofragmentation/laser-induced fluorescence (PF-LIF) technique was used to measure atmospheric HONO 10 meters above the surface. HONO is photo fragmented at 355 nm and the generated OH radical is probed at 282nm to excited state; the excited state OH fluorescence at 309 nm is detected by photomultiplier tube. This technique is both highly sensitive and specific for the detection of HONO. The system is calibrated by standard addition every 3 hours and verified by UV/VIS differential optical absorption spectroscopy. Calculated HONO concentrations using a simple steady state photochemical model are compared with the measurements and the difference is clarified.