Long-Term Composition Dynamics of PAH-Containing NAPLs and Implications for Risk Assessment

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• 作者：Catherine A. Peters ; Christopher D. Knightes ; and Derick G. Brown
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：December 15, 1999
• 年：1999
• 卷：33
• 期：24
• 页码：4499 - 4507
• 全文大小：135K
• 年卷期：v.33,no.24(December 15, 1999)
• ISSN：1520-5851

文摘

Subsurface contaminants such as coal tar, creosote,diesel fuel, and other petroleum-derived materials typicallyexist as very complex chemical mixtures. Risk assessmentis useful for site management if a single metric canrepresent the composition-dependent risk profile of themixture. This paper examines the factors governing humanhealth risk assessment for multicomponent nonaqueousphase liquids (NAPLs) containing polycyclic aromatichydrocarbons (PAHs). A model is presented describingthe interdependence of the dissolution rates of individualcompounds and the shifts in the NAPL composition that occurdue to the large differences in aqueous solubilities. Themodel also accounts for solidification of the less solubleNAPL constituents. Thirty-year numerical simulations describecomposition dynamics for natural environmental processesas well as three remediation processes: pump-and-treat, bioremediation, and solvent extraction. Carcinogenicrisk due to ingestion of contaminated groundwater atthe source is estimated, and its dependence on contaminantremoval and NAPL composition shifts is described.When composition dynamics are slow, a compound likenaphthalene has great potential to contribute to risk becauseit may persist in groundwater. When there is significantdepletion of the lower molecular weight compounds, the riskis dominated by contributions from compounds such asbenzo[a]pyrene. Remediation technologies have the greatestpotential for risk reduction if they are effective in removingthe more carcinogenic, high molecular weight compounds.Because PAHs can contribute to risk for different reasonsand because of the interdependence of their behaviors,compositional approaches lead to better risk predictions forPAHs than simple lumped metrics such as total petroleumhydrocarbon (TPH).