A Thermodynamic Approach for Modeling Partitioning of Semivolatile Organic Compounds on Atmospheric Particulate Matter: Humidity Effects

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• 作者：Myoseon Jang and Richard M. Kamens
• 刊名：Environmental Science & Technology
• 出版年：1998
• 出版时间：May 1, 1998
• 年：1998
• 卷：32
• 期：9
• 页码：1237 - 1243
• 全文大小：102K
• 年卷期：v.32,no.9(May 1, 1998)
• ISSN：1520-5851

文摘

Humidity effects on the gas/particle partitioning of thedifferent types of semivolatile organic compounds (SOCs)in the organic layer of wood soot, diesel soot, andsecondary aerosols were studied in outdoor environmentalchambers. Experimental partitioning coefficients,K_p, ofdifferent SOCs were measured using outdoor Teflon filmchambers and compared to theoretical K_p valuescalculatedwith the aid of activity coefficients and vapor pressures.Athermodynamic model based on group contribution methodswas used to estimate SOC activity coefficients in theliquid organic layer of different atmospheric particles.Theequilibrated water content in the organic phase of chemically different particles was estimated from the activitycoefficient of water in the particle's organic liquid andtheambient relative humidity (RH). It was found thatpredictedSOC activity coefficients(ⁱnals/esthag/32/i09/eqn/es970773we10001.gif">)for diesel soot particleswere not a strong function of RH. There was, however,adramatic change inⁱnals/esthag/32/i09/eqn/es970773we10002.gif">on wood soot particles forhydrophobic compounds such as alkanes and polycyclicaromatic hydrocarbons with changing RH. For polarSOCs, such as n-alkanoic acids and substitutedphenolson wood soot particles,ⁱnals/esthag/32/i09/eqn/es970773we10003.gif">did not change withincreasing RH. Similar behavior to wood soot particleswasobserved forⁱnals/esthag/32/i09/eqn/es970773we10004.gif">on secondary aerosols from the reaction of hars/alpha.gif" BORDER=0>-pinene with O₃. It was concluded thathumidityeffect on partitioning was most significant forhydrophobiccompounds in polar aerosols.