EVOLUTION OF ALKYL NITRATES WITH AIR-MASS AGE

Alkyl nitrates (RONO(2)) and alkanes (RH) were measured at Scotia, Pen nsylvania, in 1988 and at the Kinterbish Wildlife Area, Alabama, in 19 92. A simple kinetic analysis was developed to relate the two species' concentrations based on the analytical solution of two sequential fir st-order reactions using OH chemistry, RONO(2) photolysis, and assumin g peroxy radicals (ROO) + NO as the source of RONO(2). The analysis pr edicts an increase in RONO(2)/RH ratio with time. The C-4 and C-5 seco ndary alkyl nitrate/alkane ratios vary in a manner consistent with ROO + NO chemistry as their only source and photolysis and OK reaction as their only sinks. Comparison of ambient measurements of these compoun ds with predictions indicate that measured air masses experienced phot ochemical processing times consistent with alkyl nitrate evolution tim es between 0.1 and 5 days. The relationships of ethyl nitrate, n-propy l nitrate and 2-propyl nitrate ratios to their parent alkanes all indi cate additional sources of RONO(2), probably of a photochemical nature . Decomposition of larger alkoxy radicals are discussed as one possibl e source of smaller ROO radicals.