Table 1.

Laboratory Experiments on GA Sulfate Formation and Precursors

Experiment Casesa	Add H2O2	Reaction Time Before Making Aerosols	UV Radiation	Acidic Aerosols	Number Fraction of Generated Aerosols is Acidic	Number Fraction of Acid Aerosols Containing m/z 155	Relative Peak Area at m/z 155 in Acidic Particles	Acid Particle Mode Diameters (µm)
A. Glyoxal + NH4HSO4 + H2SO4	no	<1 h	no	yes	0.17	0	0	0.5
B. Glyoxal + NH4HSO4 + H2SO4	no	4 days	no	yes	0.47	0.01	2 × 10−4	0.6 (82%) and 1.8 (18%)
C. Glyoxal + NH4HSO4 + H2SO4	no	<6 h	5 h		0.54	0.03	3 × 10−4	0.6 (80%) and 2.0 (20%)
D. Glyoxal + NH4HSO4 + H2SO4	no	6 days	5 h	yes	0.68	0.11	3.5 × 10−4	1 (23%) and 2.3 (78%)
E. Glycolic acid + NH4HSO4 + H2SO4	no	1 day	no	yes	0.90	0.28	1.5 × 10−3	0.6 (44%) and 2.0 (56%)
F. Glycolic acid + NH4HSO4 + H2SO4	yes	New (<2 h)	75 min	yes	0.69	0.53	6 × 10−3	0.6 (10%) and 2.0 (90%)
G. Glycolic acid + (NH4)2SO4 + H2SO4	yes	New (<2 h)	40 min	Less acidic pH = 3	0.1	0.02	8 × 10−4	distributed between 0.5 and 2.0
H. Glycolic acid + NH4HSO4 + H2SO4	yes	1 day	75 min	yes	0.91	0.41	3 × 10−3	1.6

^aThe solutions were exposed to lab light in the daytime after they were made.