Li Zhengkai, Wrenn Brian A
Environmental Engineering Science Program, Washington University, One Brookings Drive, Campus Box 1180, St. Louis, MO 63130, USA.
Water Res. 2004 Nov;38(18):3859-68. doi: 10.1016/j.watres.2004.07.010.
Biodegradation of vegetable oil in freshwater sediments exhibits self-inhibitory characteristics when it occurs under methanogenic conditions but not under iron-reducing conditions. The basis of the protective effect of iron was investigated by comparing its effects on oil biodegradation rate and the toxicity of oil-amended sediments to those of clay and calcium, which reduce the toxicity of oil-derived long-chain fatty acids by adsorption and precipitation, respectively. Kinetic parameters for an integrated mixed-second-order model were estimated by nonlinear regression using cumulative methane production as the response variable and used to compare the effects of the three treatment factors on the rate of oil biodegradation. Ferric hydroxide was the only factor that significantly (P<0.05) increased the rate of methane production from canola oil, whereas calcium significantly reduced the oil biodegradation rate. Measurement of sediment toxicity using the Microtox Solid-Phase Test showed that inhibitory products formed within 5 days of oil addition, but the sediment toxicity decreased over time as the extent of oil mineralization increased. None of the other amendments significantly reduced the toxicity of oil-containing sediments. Since ferric hydroxide stimulated the rate of oil biodegradation without affecting the toxicity of oiled sediments, it must operate through a mechanism that is different from those previously described for clay and calcium.
植物油在淡水沉积物中的生物降解在产甲烷条件下会表现出自我抑制特性，但在铁还原条件下则不会。通过比较铁对油生物降解速率以及油污染沉积物对粘土和钙的毒性的影响，研究了铁的保护作用的基础，粘土和钙分别通过吸附和沉淀降低油衍生的长链脂肪酸的毒性。使用累积甲烷产量作为响应变量，通过非线性回归估计了综合混合二级模型的动力学参数，并用于比较三个处理因素对油生物降解速率的影响。氢氧化铁是唯一显著（P<0.05）提高菜籽油甲烷产生速率的因素，而钙则显著降低了油的生物降解速率。使用微毒性固相试验测量沉积物毒性表明，添加油后5天内形成了抑制产物，但随着油矿化程度的增加，沉积物毒性随时间降低。其他改良剂均未显著降低含油沉积物的毒性。由于氢氧化铁刺激了油的生物降解速率，而不影响油污沉积物的毒性，因此其作用机制必定与先前描述的粘土和钙的作用机制不同。
