资源环境科技发展态势分析平台

Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic gamma-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from gamma-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following gamma-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield = 4(+1/3) %, total ON yield = 14(+3/-2) %, and SOA yield <= 10% under atmospherically relevant particle mass loadings, similar to those for alpha-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and gamma-terpinene hydroxy nitrates can be reliably simulated from alpha-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of gamma-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography-mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest.