Carbon Isotopic Analysis of Atmospheric Carbonyls Via Cysteamine Derivatization

Isotopic effects of carbonyls were investigated using the simulation reactions of carbonyls with the cysteamine derivatization. Furthermore, variations of carbon isotopic for three dominant carbonyls including formaldehyde, acetaldehyde, and acetone in the roadside air of Nanning were measured using a developed method. It was found that there was a small difference in delta C-13 values (0.04 to 0.50 parts per thousand) between the calculated and measured carbonyl derivatives, indicating that no effects on the carbon isotopic fractionation occurred in the simulation reactions of carbonyls with cysteamine. The subsequent ambient air measurements showed that delta C-13 values of formaldehyde, acetaldehyde, and acetone were - 36.02 to - 31.18 parts per thousand, - 35.35 to - 32.01 parts per thousand, and - 30.45 to - 29.09 parts per thousand, respectively. Formaldehyde, acetaldehyde and acetone in the air were all enriched in the early afternoon by round 0.5-6 parts per thousand in C-13 compared to other sampling durations, which caused likely due to the contribution from positive photo-oxidation production of hydrocarbons. Finally, it was revealed that all the measured delta C-13 values (- 36.02 to - 29.09 parts per thousand) were in the range of the forecasted delta C-13 values (- 43.00 to - 26.00 parts per thousand) in terms of C-13 mass balance of carbonyls and their hydrocarbon precursors, indirectly confirming such positive productions in the air.

Automated summary

Through simulation reactions, it was found that there were no carbon isotopic fractionation effects in carbonyls with cysteamine. Carbon isotopic variations of formaldehyde, acetaldehyde, and acetone in roadside air of Nanning were measured, showing enrichment in the early afternoon. The measured delta C-13 values indirectly confirmed the positive photo-oxidation production of hydrocarbons in the air.