Yang Yu, Hunter Wesley, Tao Shu, Gan Jay
Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, China.
Environ Sci Technol. 2009 Mar 15;43(6):1852-7. doi: 10.1021/es802966z.
Microbial degradation is the most important removal process for hydrophobic organic compounds (HOCs) in soil or sediment, and chemical availability is often a governing factor. However, the availability of HOCs in the sorbed forms is still a topic of debate. In this study, we applied rigorous kinetics analysis to the relationship between the freely dissolved concentration (Cfree) of phenanthrene (PHE) measured by polydimethylsiloxane (PDMS) fibers and its degradation by a PAH degrading bacterium PYR-1 under a range of soil conditions. In solutions of soils with varying organic carbon (OC) contents, Cfree of PHE decreased from 28.63 +/- 2.15 to 0.79 +/- 0.04 microg L(-1) when the soil OC content changed from 0.23 to 7.1%. Correlation analysis between Cfree and PHE mineralization rates revealed that the bacterium quickly exhausted the PHE pool available for equilibrium distribution, including Cfree and the reversibly sorbed fraction, after which the sequestered pool was utilized. In addition, unlike changes in Cfree, degradation rates of total PHE only varied by a factor of 1.6-2.1 over the same soil OC range. Regression analysis using a multivariate relationship showed that soil OC content and porosity properties such as soil surface area had a compounded effect on the microbial availability of PHE in these soils. The kinetics analysis using Cfree, as proposed in this study, may be applied to other HOCs to gain a better understanding of microbial availability under various conditions.
微生物降解是土壤或沉积物中疏水性有机化合物（HOCs）最重要的去除过程，化学有效性通常是一个关键因素。然而，吸附态HOCs的有效性仍是一个有争议的话题。在本研究中，我们对聚二甲基硅氧烷（PDMS）纤维测定的菲（PHE）自由溶解浓度（Cfree）与其在一系列土壤条件下被多环芳烃降解菌PYR-1降解之间的关系进行了严格的动力学分析。在有机碳（OC）含量不同的土壤溶液中，当土壤OC含量从0.23%变化到7.1%时，PHE的Cfree从28.63±2.15微克/升降至0.79±0.04微克/升。Cfree与PHE矿化率之间的相关性分析表明，该细菌迅速耗尽了可用于平衡分布的PHE库，包括Cfree和可逆吸附部分，之后才利用被隔离的库。此外，与Cfree的变化不同，在相同的土壤OC范围内，总PHE的降解率仅变化了1.6 - 2.1倍。使用多元关系的回归分析表明，土壤OC含量和孔隙率特性（如土壤表面积）对这些土壤中PHE的微生物有效性具有复合效应。本研究提出的使用Cfree进行的动力学分析可应用于其他HOCs，以更好地了解各种条件下的微生物有效性。
