渗透系数级差对污染物在低渗透透镜体中的迁移影响研究

利用二维模拟槽研究非均质含水层中渗透系数级差对低渗透透镜体内污染物迁移的影响,确定不同渗透系数级差下污染物在透镜体中的波及效率和去除效率,建立低渗透透镜体内波及/去除效率、入渗/反冲时间和渗透系数级差三者之间的定量关系.结果表明：在污染过程中,污染物的迁移速度随渗透系数级差的增大而减小;在0.5m/d的地下水流速下,当渗透系数级差从3增大至52时,污染物波及效率达到100%所需要的时间从8h上升至360h;污染物的波及效率Z与入渗时间t成正相关关系与渗透系数级差K_mn呈负相关关系,其函数关系为Z=（109.623/K_mn²+1.035/K_mn+0.447）t.在模拟抽出处理的过程中,污染物的去除速度随渗透系数级差的增大而减小;当渗透系数级差从3增大至52时,污染物的去除效率达到100%所需的时间从13h升高至480h;污染物在透镜体中的去除效率Z'与反冲时间t和渗透系数级差K_mn的函数关系为Z'=（54.999/K_mn²+6.605/K_mn+0.098）t.对比两个过程可发现,污染物在非均质含水层中的污染和修复过程在时间方面呈现出不可逆性.随着渗透系数级差的增大,污染和去除过程中低渗透透镜体内波及/去除效率达100%的时间差值从5h逐渐增大至120h,"拖尾"效应越来越明显.

Study on the influence of contrasts of hydraulic conductivity on the migration of contaminants in low-permeability lens

Two-dimensional chambers were used to study the influence of permeability on the pollutant migration in the low-permeability lens of heterogeneous aquifer, and the spreading and removal efficiency of contaminant was calcuated. Also, a quantitative relationship between the spreading/removal efficiency, the contrasts of hydraulic conductivity and the time was established as a consquence. Results showed that the dye's migration speed got slower as the contrast of hydraulic conductivity increased, and the time of getting 100% dye's spreading efficiency increased from 8 to 360 hours when the contrasts of hydraulic conductivity increased from 3 to 52 at a natural groundwater flow rate of 0.5m/d. The spread efficiency of the pollutant is positively correlated with the time but negatively correlated with the contrasts of hydraulic conductivity, and the function could be expressed as:Z=(109.623/K_mn²+1.035/K_mn+0.447)t. Then water was injected to flush the dye at the same flow rate of 0.5m/d to simulate the Pump-and-Treat Technique to remediate the contaminant. Results showed that the larger of the contrast of hydraulic conductivity, the faster of the removal rate. When the contrast of hydraulic conductivity increased from 3 to 52, the removal time dye increased from 13 to 480 hours, and the fuction of the spreading/removal efficiency with cont-rasts of hydraulic conductivity and time could be expressed as:Z'=(54.999/K_mn²+6.605/K_mn+0.098)t. Comparing the two processes, it can be found that the pollution and remediation process of the contaminant in the heterogeneous aquifer is irreversible in terms of time.Under the same conditions, the entry rate of the dye was always lager than the removal rate, and the time difference increased gradually from 5 to 120 hours with the increase of the contrast of hydraulic conductivity, which means the tailing effect becoming more and more obvious.