Inter-comparison Characterization of Nitrous Acid Measurements by IBBCEAS and LOPAP

Gaseous nitrous acid (HONO) is a relatively active nitrogen oxides in the atmosphere. In this work, the incoherent broadband cavity-enhanced absorption spectroscopy (IB-BCEAS) and long path absorption photometer (LOPAP) was both used to measure HONO. The measurement results were compared and verified. Under a variety of different relative humidity (RH = 0, 28, 54, 69%), flow rate (flow rate = 2, 4, 6, 8 LPM) and NO
₂
concentration (NO
₂
= 50, 80, 100 ppbV), LOPAP and IBBCEAS simultaneously measured the HONO to characterize the uncertainty and relationship between the two instruments. The results showed uptake of NO
₂
produced HONO by the extractive tubing surface of IBBCEAS instrument. The measured concentration of IBBCEAS needs to correct the influence of the tubing. And the LOPAP instrument could have positive HONO readings while high NO
₂
were introduced. The IBBCEAS and LOPAP instruments were highly consistent in measuring HONO.