Peroxyacetyl nitrate ($\mathrm{C}{\mathrm{H}}_3\mathrm{C}(\mathrm{O})\mathrm{OON}{\mathrm{O}}_2$)

An organic nitrogen reservoir formed by association of a peroxyacetyl radical with nitrogen dioxide. Thermal dissociation can release reactive nitrogen again; its temperature sensitivity helps distinguish transport through cool air from rapid recycling in warmer air.