The goal of this project is to derive national emission magnitudes based on multi-year observational records at nine continental U.S. sites for trace gases such as methane, nitrous oxide, sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), chlorofluorocarbons (CFCs), and carbon monoxide (CO) via a recently developed technique for deriving regional emission magnitudes of trace gases via co-measurements of atmospheric 14CO2. That initial data analysis focused on emission estimates for the northeastern US based on results from two aircraft profiling sites over multiple years. Although the distribution of sampling locations is currently extensive and should provide a representative estimate of total US emissions for these gases, the project will add measurements at one additional site in the northeastern US to ensure that emissions from this high-emission region are accurately characterized. The 14C-based estimates for the entire US will be compared to estimates from multiple data-based and model-based approaches commonly used for deriving regional-to-continental-scale emissions of these trace gases. The assessment of different top-down estimation techniques proposed here is presently lacking for non-CO2 trace gas emissions, but is needed for quantifying limitations and biases known to be associated with many of the techniques currently in use in the atmospheric science community.