Capturing CO2 from ambient air - David Keith

periodic switching of the spray on and off. This allowed better separation of the spray signal from background
variation and from absorption by the wetted walls. Additionally, the magnitude of the spray signal
in some of these trials was much smaller, 4–15 ppm instead of the 20–40 ppm of earlier trials. Multiple
measurements were required to separate the signal from background noise. Figure B.10 shows data from
a typical trial. Substantial subjective judgment is used in choosing the bounds of each averaging period.
Bounds are chosen to exclude transient effects of when the spray is switched or point of measurement is
changed and to exclude regions of noise or otherwise incoherent signal. Each switching cycle is analyzed
by an average over at least one “spray on” region and one “spray off” region. The difference between a
each pair of averages is taken to be an independent measurement for purposes of estimating uncertainty
bounds. Sometimes multiple averages are drawn for one region because significant drift is visible. Averages
are paired to be close in time and to avoid effects of visible drift. Data where noise or drift renders
peaks incoherent are discarded.
This document, including figures and associated data analysis, was created entirely with free software,
notably L Y X, LATEX, Grace, and Linux.
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