They are formed byatmospheric photochemistry reaction, and could product OH radical, alkyl radical, ozone,carboxylic acid peroxyacetyl nitrates by atmospheric photochemistry reaction.

羰基化合物既是大气光化学反应的产物，又能通过光化学反应生成羧酸、羟基自由基、臭氧和过氧乙酰硝酸酯。