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摘要
Studies of climate change increasingly recognize the diverse influences exerted by monoterpenes in the atmosphere, including roles in particulates, ozone: formation, and oxidizing potential. Measurements of key= monoterpenes suggest. atmospheric mole fractions ranging from low pinol/mol (parts-pertrillion; ppt) to nmol/mol (parts-per,billion; ppb), depending on location and compound. To accurately etablisli the mole fraction trends, assess the role of manoteipenes.in atmospheric chemistry,' and relate measurement records from many laboratories and researchers, it is essential to have good calibration standards. The feasibility of preparing well characterized, stable gas cylinder : standards for monoterpenes at the nmol/mol level was previously, tested using treated (Aculife IV) aluminum gas cylinders at NIST Results for 4 of the 11 monoterpenes, monitored versus an internal 'standard of benzene, indicated stability in these treated aluminum gas cylinders for over 6 months and projected long-term (years) stability. However, the mole fraction of the key monoterpene,beta-pinene decreased, while the mole fractions of alpha-pinene, D-limonene (R-(+)-limonene), p-cymene, and camphene (a terpene not present in the initial gas Mixture) increased, indicating a chemical transformation of beta-pinene to these species. A similar pattern of decreasing mole fraction was observed in alpha-pinene where growth of o-limonene, p-cymene, and camphene has been observed in treated gas cylinders prepared With a mixture of just alpha-pinene and benzene as the internal standard. The current research discusses the testing of other cylinders and treatments for the potential of long-term stability of monoterpenes in a gas mixture. In this Current study, a similar pattern Of decreasing mole fraction; although somewhat improved short-term stability; was observed for fi-pinene and alpha-pinene,with growth of o,limonene, p=cyrriene, and camphene, in nickel-plated carbon steel cylinders.,beta-Pinene and alpha-pinene showed excellent stability at over. 6 months. in aluminum cylinders treated with a different process (ExperiS) than used in the original study.
- 出版日期2013-5-7
