大肠杆菌在饱和砂质壤土中非平衡运移的CDE数学模型模拟

稳态、饱和条件下，以速度u=0．214cm min^-1和0．470cm min^-1进行混合置换实验，研究大肠杆菌在砂质壤土中的运移，并根据平衡与非平衡假设下，对流一弥散方程数学模型进行数值模拟。结果表明，含非平衡的双点吸附、且含有不可逆滞留项的模型能够较好地模拟大肠杆菌在砂质壤土中的运移。模拟和实验结果均表明，大肠杆菌的BTC（Breakthrough Curve穿透曲线）与示踪剂相比峰值明显降低，拖尾明显，且出现延迟，总的流出量也明显少于示踪剂；当水流速度由0．214cm min^-1增至0．470cm min^-1时。大肠杆菌BTC峰值由0．05增至0．2，且随速度的增加，滞留系数减小。

NON-EQUILIBRIUM TRANSPORT OF ESCHERICHIA COLI THROUGH SATURATED SANDY LOAM AND ITS SIMULATION WITH CDE MODEL

Transport of bacteria through subsurface environment was studied from different perspectives,including the fate of genetically engineered microorganisms in the environment,waste management,public health,microbially enhanced oil(recovery) and in-situ remediation of contaminated subsurface.The objective of this study was to investigate transport and sorption of bacteria in saturated sandy loam.Escherichia coli and Cl~(-1) tracer solution were introduced separately into saturated soil(columns) as a pulse function under steady water flow.A mathematical model based on one-dimensional convection-dispersion(equation)(CDE),including the local equilibrium assumption and non-equilibrium assumption,was formulated to describe(E.coli)'s transport.The CXTFIT program was used to fit mathematical solutions of different theoretical transport models,based upon the CDE,to experimental results.The results show transport of E.coli through sandy loam was well described by the(chemical) nonequilibrium two-sites model when a firstorder kinetic removal process was assumed.Bacteria were removed at a (significantly) greater rate than Cl~(-1) tracer.Breakthrough Curve(BTC) of E.coli was retarded and had a longer elution tailing(when) it was compared with that of Cl~(-1) tracer,and the relative concentration of E.coli at the peak of BTC was much lower than that of the tracer.The total breakthrough of E.coli was also much smaller than that of the tracer.The increase in flow velocity from 0.214 to 0.470 cm min~(-1) resulted in marked increase in E.coli from 0.05 to 0.2 at the peak of BTC,but decrease in(retention) coefficient.