Hong Lei, Luthy Richard G
Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305-4020, USA.
Environ Toxicol Chem. 2007 Mar;26(3):394-405. doi: 10.1897/06-200r.1.
Lampblack-impacted soils at former oil-gas plant sites in California, USA, were characterized to assess the sorption of polycyclic aromatic hydrocarbons (PAHs) and the concentration-dependent effects of a residual oil tar phase on sorption mechanism and availability of PAHs. Nuclear magnetic resonance spectroscopy demonstrated similar aromaticity for both lampblack carbon and the oil tar phase, with pronounced resonance signals in the range of 100 to 150 ppm. Scanning-electron microscopic images revealed a physically distinct oil tar phase, especially at high concentrations in lampblack, which resulted in an organic-like film structure when lampblack particles became saturated with the oil tar. Sorption experiments were conducted on a series of laboratory-prepared lampblack samples to systematically evaluate influences of an oil tar phase on PAH sorption to lampblack. Results indicate that the sorption of PAHs to lampblack exhibits a competition among sorption phases at low oil tar contents when micro- and mesopores are accessible. When the oil tar content increases to more than 5 to 10% by weight, this tar phase fills small pores, reduces surface area, and dominates PAH sorption on lampblack surface. A new PAH partitioning model, Kd = KLB-C(1 - ftar)alpha + ftarKtar (alpha = empirical exponent), incorporates these effects in which the control of PAH partitioning transits from being dominated by sorption in lampblack (KLB-C) to absorption in oil tar (Ktar), depending on the fraction of tar (ftar). This study illustrates the importance of understanding interactions among PAHs, oil tar, and lampblack for explaining the differences in availability of PAHs among site soils and, consequently, for refining site-specific risk assessment and establishing soil cleanup levels.
对美国加利福尼亚州前油气厂场地受油烟影响的土壤进行了表征，以评估多环芳烃（PAHs）的吸附以及残留油焦油相对吸附机制和PAHs有效性的浓度依赖性影响。核磁共振光谱表明，油烟碳和油焦油相具有相似的芳香性，在100至150 ppm范围内有明显的共振信号。扫描电子显微镜图像显示存在物理上不同的油焦油相，尤其是在油烟中高浓度时，当油烟颗粒被油焦油饱和时会形成类似有机膜的结构。对一系列实验室制备的油烟样品进行了吸附实验，以系统评估油焦油相对PAHs吸附到油烟上的影响。结果表明，当微孔和中孔可及且油焦油含量较低时，PAHs对油烟的吸附表现出吸附相之间的竞争。当油焦油含量增加到超过5%至10%（重量）时，该焦油相填充小孔，减小表面积，并主导PAHs在油烟表面的吸附。一个新的PAH分配模型，Kd = KLB-C(1 - ftar)alpha + ftarKtar（alpha = 经验指数），纳入了这些影响，其中PAH分配的控制从以油烟吸附（KLB-C）为主转变为以油焦油吸收（Ktar）为主，这取决于焦油分数（ftar）。本研究说明了理解PAHs、油焦油和油烟之间相互作用对于解释场地土壤中PAHs有效性差异的重要性，因此对于完善特定场地风险评估和确定土壤清理水平也很重要。
