HR: 0830h
AN: A11F-0047 [PDF]
TI: The role of dew in controlling HONO surface-air exchange during the night and in the morning
AU: He, Y
EM: Yihe@Wadsworth.Org
AF: School of Public Health/SUNY at Albany, Empire State Plaza, Albany, NY 12201 United States
AU: Hou, J
EM: jianhou@wadsworth.org
AF: School of Public Health/SUNY at Albany, Empire State Plaza, Albany, NY 12201 United States
AU: * Zhou, X
EM: zhoux@wadsworth.org
AF: School of Public Health/SUNY at Albany, Empire State Plaza, Albany, NY 12201 United States
AU: * Zhou, X
EM: zhoux@wadsworth.org
AF: Wadsworth Center/NYSDOH, Empire State Plaza, Albany, NY 12201 United States
AB:
The presence of dew on surfaces may significantly influence temporal distributions of water-soluble species, such as HONO, in
the atmospheric boundary layer. Our ambient HONO measurements at several rural sites suggest that wet ground surfaces act
as a sink for ambient HONO during the late night and in the early morning, reserving the trend of nighttime HONO
accumulation. When dew evaporates in the morning, part of the trapped nitrite is released into the overlying atmosphere,
contributing to the high-than-expected HONO concentrations despite of its effective photolysis. Here we present several new
evidences to support the hypothesis that dew on ground surfaces is a sink and a temporary reservoir for atmospheric HONO.
First, vertical HONO gradient measurement over a forested site indicates that HONO exchange between canopy surface and the
overlying air is closely coupled with air relative humidity. Secondly, a temperature-controlled flow reaction experiment
mimicking dew formation and evaporation shows an efficient loss of gas-phase HONO when surface is moist and a fast release of
HONO into the gas-phase when surface is dry. And thirdly, samples from washing tree leaves contain significant amount of
nitrite when moist during early morning and little nitrite when dry in either morning or other time of the day. Atmospheric
implications of our observations will be discussed in details.
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting