n-Alkanes, the main component of diesel fuel, are common light non-aqueous phase liquids (LNAPLs) that threaten ecological security. The subsurface from vadose zone, through fluctuating zone, to saturated zone, is a critical multi-interface earth layer which significantly affects the biodegradation processes of n-alkanes. A pilot-scale diesel contaminated aquifer column experiment has been undertaken to investigate the variations of bacterial community and alkane monooxygenase (alkB) gene abundance in these zones due to water-table fluctuations. The n-alkanes formed a layer immediately above the water table, and when this was raised, they were carried upwards through the fluctuating zone into the vadose zone. Water content and n-alkanes component C10-C12 are main factors influencing bacterial community variation in the vadose zone, while C10-C12 is a key driving factor shaping bacterial community in the fluctuating zone. The most abundant bacterial phyla at all three zones were Proteobacteria, Firmicutes and Actinobacteria, but moisture-niche selection determined their relative abundance. The intermittent wetting cycle resulted in higher abundance of Proteobacteria, and lower abundance of Actinobacteria in the vadose and fluctuating zones in comparison to the control column with a static water-table. The abundances of the alkB gene variants were relatively uniform in different zones, probably because the bacterial populations harboring alkB gene are habituated to biogenic n-alkanes rather than responding to diesel fuel contamination. The variation in the bacterial populations with height due to moisture-niche selection had very little effect on the alkB gene abundance, possibly because numerous species in both phyla (Proteobacteria and Actinobacteria) carry an alkB gene variant. Nevertheless, the drop in the water table caused a short-term spike in alkB gene abundance in the saturated zone, which is most likely associated with transport of solutes or colloids from the fluctuating zone to bacteria species in the saturated zone, so a fluctuating water table could potentially increase n-alkane biodegradation function.

正构烷烃是柴油燃料的主要成分，是常见的轻质非水相液体 (LNAPL)，对生态安全构成威胁。渗流带、脉动带、饱和带的地下是影响正构烷烃生物降解过程的关键多界面土层。已经进行了中试规模的柴油污染含水层柱实验，以研究细菌群落和烷烃单加氧酶（ alkB) 由于地下水位波动，这些区域的基因丰度。正构烷烃在地下水位正上方形成一层，当水位升高时，它们被向上携带通过波动区进入渗流区。含水量和正构烷烃组分C10-C12是影响包气带细菌群落变化的主要因素，而C10-C12是形成波动带细菌群落的关键驱动因素。所有三个区域中最丰富的细菌门是变形菌门、厚壁菌门和放线菌门，但水分生态位选择决定了它们的相对丰度。间歇性润湿循环导致变形菌的丰度较高，而变形菌的丰度较低。与具有静态地下水位的对照柱相比，渗流和波动区域中的放线菌。alkB基因变异体的丰度在不同区域相对一致，可能是因为携带alkB基因的细菌种群习惯于生物正构烷烃，而不是对柴油燃料污染作出反应。由于水分生态位选择导致的细菌种群高度变化对alkB基因丰度的影响非常小，这可能是因为两个门（变形杆菌门和放线菌门）中的许多物种都携带alkB基因变体。然而，地下水位的下降导致了短期的飙升饱和区的alkB基因丰度，这很可能与溶质或胶体从波动区向饱和区细菌物种的运输有关，因此波动的地下水位可能会增加正构烷烃的生物降解功能。