河床含水系统对单环芳烃净化特征室内模拟

Application of Riverbed Quiferous System to Indoor Simulation of Decontamination of Aromatic Hydrocarbons

为了模拟长期排污河流中单环芳烃在地表水-地下水系统迁移转化规律以及不同含水介质和水动力条件对单环芳烃的净化特征,室内土柱实验采用3种有代表性的天然砂土为研究对象,以生活污水模拟纳污河流,实验历时5个月.单环芳烃的自然净化作用主要发生在河床底下0.4m内,垂直向下单环芳烃各组分浓度呈由高到低的分布特征;粗砂对苯、甲苯和单环芳烃总量(TBETX)总净化率分别为32.06%、21.39%和27.13%;中砂1分别为76.26%、81.40%、87.99%;中砂2分别为68.94%、74.41%、81.69%,这表明,河流污染初期河床底含水介质完全饱水,含水介质颗粒尺寸越大,对单环芳烃的净化率就越低,单环芳烃容易迁移进入地下水中;随着时间的延长,河床底部淤泥层不断增加,砂层中的水流处于非饱和状态,淤泥层和含水介质系统对单环芳烃的净化能力较饱水流时大,单环芳烃不容易迁移进入地下水.

In the five-month indoor earth-column experiment, three representative kinds of natural sand are analyzed, and the refluxes of domestic sewage are used to simulate the contaminated river flow. This indoor experiment aims at both the simulation of the migration and transfer law of aromatic hydrocarbons in the surface water-underground water system in a longterm drainage river and that of the impacts of different aquiferous media and hydrodynamic conditions on the decontamination of aromatic hydrocarbons. Aromatic hydrocarbons in column decrease gradually with the flow direction, where the natural decontamination occurs at 0. 4 m of the surface layer. Total decontamination ratios of benzene, toluene and total aromatic hydrocarbons （TBETX） in the coarse sand is 32. 06%, 21.39% and 27. 13%, respectively; in the first kind of the medium sand is 76.26%, 81. 40% and 87. 99%, respectively;in the second kind of the medium sand is 68. 94%, 74. 41% and 81.69 %, respectively. All these results indicate that the hydrous medium in the riverbed is perfectly saturated in the early period of the contamination of the river, where the greater the size of the hydrous medium, the lower the decontamination rate of the aromatic hydrocarbons. In this case, the aromatic hydrocarbons migrate easily into the underground water systen; As times went by, the silt seams in the riverbed became thicker and thicker till unsaturated flow moves into the sand. However, when the decontamination rate of aromatic hydrocarbons in the silt seams and hydrous medium system is greater than that in the saturated water flow, the aromatic hydrocarbons will not easily migrate into the corresponding underground water system.