A key mechanism that couples anthropogenic emissions with biogenic emissions is the effect of NOx on organic nitrates (ON) and biogenic secondary organic aerosols (SOA) formation. The overall goal is to establish a fundamental and quantitative understanding of the formation mechanisms, yields, gas-particle partitioning, and fates of ON and SOA from monoterpenes under all oxidation pathways (ozonolysis, photooxidation, and nitrate radical oxidation). Specific objectives are 1) to investigate formation mechanisms and quantify ON yields from ozonolysis, OH, and NO3 oxidation of monoterpenes, 2) to quantify the rates and extents of hydrolysis of particle-phase ON generated from different oxidation pathways, 3) to systematically evaluate the photochemical fates of gas-phase and particle-phase ON, and 4) to obtain closure of reactive oxidized nitrogen species in chamber experiments to achieve a quantitative understanding of the roles of ON species in NOx cycling. A series of laboratory chamber experiments will be conducted to investigate ON and SOA formation from ?�-pinene and ?�-pinene oxidations. We will systematically investigate the effects of various factors on ON formation and fates: relative humidity, seed type and particle acidity, hydrolysis, and photochemical aging (h?� reaction). The changes in gas and aerosol composition, aerosol chemical and physical properties will be continuously monitored by a suite of analytical instruments surrounding the chamber facility. The proposed study will provide fundamental, comprehensive, and quantitative insights into monoterpene organic nitrogen chemistry. We expect the results from this study to significantly transform our understanding of the roles of ON in NOx cycling, ozone and SOA formation. Results from this study will not only contribute to the interpretation of ambient observations, but will also provide the much-needed fundamental data for improved parameterizations of ON and SOA formation from BVOC oxidations in models, facilitating more accurate predictions of the control of ON over NOx cycling, ozone, and OA as NOx emissions continue to change in the future.