Nitrogen Isotopic Composition of Coal-Fired Power Plant NO_x: Influence of Emission Controls and Implications for Global Emission Inventories

摘要

Despite the potential use of δ~(15)N as a tracer of NO_x source contributions, prior documentation of δ~(15)N of various NO_x emission sources is exceedingly limited. This manuscript presents the first measurements of the nitrogen isotopic composition of NO_x (δ~(15) N-NO_x) emitted from coal-fired power plants in the U.S. at typical operating conditions with and without the presence of selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR) technology. To accomplish this, a novel method for collection and isotopic analysis of coal-fired stack NO_x emission samples was developed based on modifications of a historic U.S. EPA stack sampling method. At the power plants included in this study, large differences exist in the isotopic composition of NO_x emitted with and without SCRs and SNCRs; further the isotopic composition of power plant NO, is higher than that of other measured NO_x emission sources confirming its use as an environmental tracer. These findings indicate that gradual implementation of SCRs at power plants will result in an industry-wide increase in δ~(15)N values of NO_x and NO-y oxidation products from this emission source.