Tropospheric HONO distribution and chemistry in the southeastern US

摘要: Abstract. Here we report the measurement results of nitrous acid (HONO) and a suite of relevant parameters on NCAR C-130 research aircraft in southeastern US during NOMADSS 2013 summer field study. The daytime HONO concentration ranged from low parts per trillion by volume (pptv) free troposphere (FT) to mostly within 5–15 pptv background planetary boundary layer (PBL). There was no discernible vertical gradient above lower flight altitude 300 m PBL, transport ground surface was not found be significant contributor tropospheric budget. The total situ source mean ( ± 1 SD) calculated as 53 ( 21) pptv h −1 during day. upper-limit contribution from NOx -related reactions 10 5) pptv h , the contribution photolysis particulate nitrate pNO3 ) 38 ( 23) pptv h based measured concentrations and median rate constant 2.0  ×  10 −4  s determined laboratory using ambient aerosol samples. The photolysis contributed less than 10 % primary OH source. However, recycling via equivalent to ∼  2.3  −6  mol m −2  h air column considerable supplementary the low- area. Up several tens were observed in power plant urban plumes day, produced situ from precursors including . Finally, there no observable accumulation nocturnal residual layer the nocturnal FT US, with an increase the HONO  ∕ ratio ≤  3  after sunset.