典型荧光示踪剂在包气带中的迁移、吸附特性

Migration,adsorption characteristics of typical fluorescent tracer in vadose zone

为研究荧光示踪剂在包气带土壤中的迁移-吸附特性,指导填埋场渗漏检测过程的示踪剂选择、投加和采样.采用土柱实验、参数反演手段,研究3种典型荧光示踪剂在包气带中的吸附、滞后和穿透规律,确定其迁移表征方法、表征参数和最佳模型.结果表明:在土壤有机碳相对较高和较低时,分别可用非线性平衡和线性平衡模型准确拟合罗丹明B在其中的穿透数据,而非线性平衡模型同时准确拟合了荧光素和荧光素钠在两种有机碳土壤中的穿透数据.基于最优反演模型,在低有机碳土壤中示踪剂迁移参数为:罗丹明B、荧光素和荧光素钠的分配系数分别为84.99,1.80,1.48cm^3/g,滞后因子分别为393.27,8.18,7.81,吸附容量分别为6.14×10^-3,0.15×10^-3,0.14×10^-3mg/g,均出现罗丹明B>荧光素>荧光素钠的顺序.荧光素钠在包气带中迁移时固相吸附浓度最小、迁移速率最快、吸附消耗量最小,建议在进行填埋场渗漏示踪中选用.

Adsorption and transport properties of the fluorescent tracer in vadose zone soil system were investigated to guide the choice,addition,sampling of tracer during landfill leakage detection process.To determine the characterization method,characterization parameters and best model of tracers,soil column experiments and parameter inversion method were used to study the law of adsorption,retention,and breakthrough of 3 typical fluorescent tracers in vadose zone soil.Results showed that in higher and lower organic carbon soil,Rhodamine B breakthrough data by soil were fitted well with the Non-Linear Equilibrium(NE)model and the Linear Equilibrium(LE)model respectively,but breakthrough data of fluorescein and Sodium fluorescein were fitted well with NE model.Based on the best inversion model,the tracer migration parameters in lower organic carbon soil were:The distribution coefficients of Rhodamine B,Fluorescein,and Sodium fluorescein were respectively 84.99,1.80,1.48 cm^3/g;The retardation factors of them were respectively 393.27,8.18,7.81;The adsorption capacity of them were respectively 6.14×10^-3,0.15×10^-3,0.14×10^-3 mg/g.It was shown that the three parameters of tracers were ranked in descending order as follows:Rhodamine B>fluorescein>Sodium fluorescein.Sodium fluorescein showed the properties of least adsorption concentration,the fastest migration rate,the least adsorption capacity when transported at vadose zone in our study,we recommend to use Sodium fluorescein as a conservative tracer during landfill leakage tracing.