Recent advances in detection of NH3 and HNO3 on short timescales suitable for eddy covariance flux measurements
Authors
Scott C Herndon — Aerodyne Research, Inc.
Mark Stuart Zahniser — Aerodyne Research, Inc.
John B Nowak — Aerodyne Research, Inc.
Rob Roscioli — Aerodyne Research, Inc.
Category
General Topics – Aerosol
Description
Ammonia and nitric acid play important roles in aerosol, cloud, and OH chemistry. Accurately measuring these species' concentrations on a fast timescale has historically been complicated due to their tendency to slowly and irreversibly interact with instrument surfaces. Here we present recent efforts aimed at mitigating these effects using new inlet technologies. First, an inlet that combines an inertial impactor with a pressure drop across a critical orifice provides particle removal without a traditional filter. This approach is used to reduce instrumental time responses for NH3 and HNO3 to the order of 3-15 seconds. Second, a further reduction in time response is achieved by entraining functionalized perfluoroalkane vapor into the inlet sampling stream. This "active passivation" method is used to achieve time responses of ~0.5 seconds for both NH3 and HNO3, and is found to be applicable to a variety of inlet designs. These technologies enable fast time response sampling suitable for eddy covariance flux measurements.
