There is increased interest in addressing adverse ecosystem effects associated with nitrogen deposition through the secondary National Ambient Air Quality Standards (NAAQS).  The NAAQS structure raises interesting challenges in bridging ambient and deposition space while imposing some constraints on biologically active forms of nitrogen that may not explicitly be considered a NAAQS specie.   This presentation explores two “NAAQS” bridging constructs – transference ratios and the delineation of particulate ammonium contribution to wet deposition – through a series of three dimensional spatial analyses across a variety of Federal Class 1 and Ecoregion Level 3 areas based on a time series of 2002 -2012 CMAQ air quality simulations that underpin the TDEP deposition surfaces.   These analyses are used to better understand the limits of using surface level indicators, associated with ground based monitoring systems, intended to capture processes through the entire atmospheric column.