Quantification of the Soot-Water Distribution Coefficient of PAHs Provides Mechanistic Basis for Enhanced Sorption Observations

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• 作者：Thomas D. Bucheli and Ö ; rjan Gustafsson
• 刊名：Environmental Science & Technology
• 出版年：2000
• 出版时间：December 15, 2000
• 年：2000
• 卷：34
• 期：24
• 页码：5144 - 5151
• 全文大小：95K
• 年卷期：v.34,no.24(December 15, 2000)
• ISSN：1520-5851

文摘

There is an increasing recognition of the necessity toconsider the heterogeneity of geosorbents, and in particularthe condensed carbon facies fraction, to improveprediction of hydrophobic pollutant phase speciation.Field observations of much elevated organic-carbonnormalized distribution coefficients (K_oc) of PAHs-relativeto predictions from bulk organic-matter partitioning models-have been suggested to be explainable by soot sorption. Toafford testing of this hypothesis, we here report on the soot-water distribution coefficients (K_sc) for a series of PAHs(naphthalene (NP), fluorene (FL), phenanthrene (PH), andpyrene (PY)) using diesel particulate matter (NIST standardreference material SRM-1650) as model soot sorbent.Specifically adapted batch and column experiments yieldedaverage log K_sc values of 5.23, 5.40, 5.82, and 6.59 (batch)and 4.63, 6.03, 6.62, and 7.03 (column) for NP, FL, PH,and PY, respectively (all data in [L_w/kg_sc]). The obtainedvalues are 35-250 times higher than respective K_oc predictionsand are considerably closer to theoretically estimated soot-water distribution coefficients. Our data are among thehighest solid-water distribution coefficients of anenvironmentally relevant sorbent ever reported and lenddirect empirical support of active soot sorption as a viableexplanation to the enhanced PAH partitioning. Sorptionkinetics on the hours-days time scale and similarity of externalgeometric and BET surface areas suggest that interactionsites are largely restricted to the outer surface of thesoot. The constrained K_sc values facilitate prediction ofspeciation and bioavailable exposures of PAHs in aquaticand sedimentary environments.