Digangi JP, Henry SB, Kammrath A, Boyle ES, Kaser L, Schnitzhofer R, Turnipseed A, Park J-H, Weber RJ, Hornbrook RS, et al. Observations of glyoxal and formaldehyde as metrics for the anthropogenic impact on rural photochemistry. Atmospheric Chemistry and Physics Discussions. 2012;12:9529–9543.