NO(y) removal from the Cumberland Power Plant Plume

Airborne measurements were performed in the plume of the Cumberland Power Plant during August 1998 using a highly sensitive SO₂ instrument. The measurements confirmed previous suggestions that NO_y species are removed from the plume at a faster rate than SO₂. The differential removal rate (the difference between loss rate of NO_y and that of SO₂) was estimated to be 0.06 h^-1. This value implies that the NO_y loss rate is in the range of 0.09-0.14 h^-1. The application of a mathematical argument, based on the convolution integral, enabled improved synchronization of the data from the SO₂ and NO_y instruments. Examination of the synchronized data revealed that the concentration ratio of SO₂ and NO_y varies across the plume. Near the source it is higher at the wings of the plume, while in the core of the plume it is similar to the ratio at the release point. Two possible explanations of the observations are discussed: conversion to non-measurable NO_y species, and in-plume loss of NO_y (as HNO₃) via dry deposition.