Liu Lihua, Endo Satoshi, Eberhardt Christina, Grathwohl Peter, Schmidt Torsten C
Center for Applied Geoscience (ZAG), University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany.
Environ Toxicol Chem. 2009 Aug;28(8):1578-84. doi: 10.1897/08-276.1. Epub 2009 Mar 23.
Coal tar aged in a large-scale, artificial aquifer experiment for five years was subsequently investigated for leaching behavior of polycyclic aromatic hydrocarbons (PAHs). After five years, the initially liquid coal tar had solidified and formed segregated particles with a grain size similar to that of the sandy aquifer material. The composition of the aged coal tar (ACT) with regard to PAHs was remarkably different from that of the original bulk coal tar (BCT), because most of the low-molecular-weight compounds had been depleted. Equilibrium aqueous-phase concentrations of 17 PAHs leaching from the aquifer material containing the ACT were measured from consecutive equilibration steps at increasing temperatures of between 25 and 100 degrees C using accelerated solvent extraction. The results showed 2- to 5,000-fold lower concentrations than those from BCT, indicating dramatic changes of dissolution behavior of PAHs from coal tar after the five-year aging period. Predictions based on Raoult's law with the subcooled liquid solubilities substantially overestimated the equilibrium aqueous-phase concentrations of the PAHs from ACT, whereas the estimations were reasonable if the solid solubilities were employed instead. The enthalpies of phase transfer from ACT to water were determined based on the van't Hoff equation. The resulting values agreed with the dissolution enthalpies of pure solid rather than subcooled liquid PAHs.
在一项大规模人工含水层实验中老化了五年的煤焦油，随后对其多环芳烃（PAHs）的浸出行为进行了研究。五年后，最初呈液态的煤焦油已经固化，并形成了与砂质含水层物质粒径相似的分离颗粒。老化煤焦油（ACT）中PAHs的组成与原始块状煤焦油（BCT）的组成显著不同，因为大多数低分子量化合物已经耗尽。使用加速溶剂萃取法，在25至100摄氏度的升高温度下，通过连续平衡步骤测量了从含有ACT的含水层物质中浸出的17种PAHs的平衡水相浓度。结果表明，其浓度比BCT低2至5000倍，表明经过五年老化期后，煤焦油中PAHs的溶解行为发生了显著变化。基于拉乌尔定律并使用过冷液体溶解度进行的预测大大高估了ACT中PAHs的平衡水相浓度，而如果使用固体溶解度进行估算则较为合理。基于范特霍夫方程确定了ACT向水的相转移焓。所得值与纯固体而非过冷液体PAHs的溶解焓一致。
