Climate and N flux data for Saddle, 1992 - 1995.

Atmospheric gaseous nitric acid (HNO3) plus particulate matter nitrate (NO3) and ammonium (NH4) concentrations were being measured at the Saddle site on an approximately biweekly basis during the winter and on a weekly to twice-weekly basis from April through September. These N species are the dominant contributors to atmospheric N loading at the Saddle site alpine tundra. A 47-mm filter pack with a teflon front filter for NO3 and NH4 collection followed by a nylon filter for HNO3 collection is used to sample the ambient air for 3 to 6 hr. Subsequent colorimetry analysis, performed at the MRS Kiowa Laboratory, is used to obtain the mass of HNO3, NO3, and NH4 on each filter. Air concentrations are then determined by dividing masses by the volume of air sampled.