重非水相液体与水相界面面积的二维实验研究

Experimental analysis of DNAPL-water interfacial areas in a two-dimensional flow cell

多孔介质中重非水相液体(Dense Non-Aqueous Phase Liquid,DNAPL)与水相的界面面积是影响DNAPL在地下水中溶解速率的关键参数。本文通过二维均质砂箱实验,运用界面分配示踪法和体积分配示踪法分别测定DNAPL与水相的界面面积(单位介质体积内的面积,Anw)和DNAPL饱和度(Sn),并研究两者之间的相关关系。使用C_(18)H_(29)NaO_3S(SDBS)作为界面分配示踪剂,Alcohol(2,4-Dimethyl-3-Pentanol)作为体积分配示踪剂,CaBr_2作为保守示踪剂。利用Fe2+催化的Na_2S_2O_8对DNAPL进行原位氧化修复,改变Anw和Sn。结果表明,通过定量(用孔隙体积数PV值衡量)加入Na_2S_2O_8,Anw由206cm^2逐渐降为37cm^2,下降速率约为14cm^2/PV;Sn由1.34%逐渐降为0.33%,下降速率约为0.1%/PV;Anw和Sn之间具有良好的线性关系(Anw=146×Sn,R2=0.987)。此关系可用于估算多孔介质中DNAPL与水相之间的界面面积。对实验影响因素的分析表明,孔隙度的增大(变化率为20.7%)使示踪剂穿透曲线出现肩现象和拖尾现象,导致保守示踪剂的保留时间增加5.6%,界面面积减小6.8%。

The interracial area between dense Non-Aqueous Phase Liquid （DNAPL） and water in porous media is a key parameter determining the dissolution rate of DNAPL in groundwater. In the present study, the specific DNAPL-water interracial area （Anw） and DNAPL saturation （Sn） were respectively measured by using interracial partitioning and bulk partitioning tracer tests in a homogeneous two-dimensional flow cell. The relationship between Anw and Sn was also analyzed. C18 H29 NaO3S （SDBS）, Alcohol （2, 4-DimethyF3- Pentanol）, and CaBr2 were used as the interracial partitioning tracer, bulk partitioning tracer, and nonreactive tracer, respectively. Fe2＋ activated persulfate was used for in situ chemical oxidation （ISCO） remediation, to change Anw and Sn with increased pore volumes （PV） of persulfate. The results showed that, Anw decreased from 206 emz to 37 cm2 by the rate of 14 cm2/PV and Sn decreased from 1.34% to 0. 33% by the rate of 0. 1%/PV. The observed interracial area decreased linearly with the decreasing of the NAPL saturation （Amw= 146 X Sn, R2 =0. 987）, which can be used as a simple method to estimate the interracial area between NAPL and water in porous media. The analysis of impacts showed that, the breakthrough curves of tracers exhibited shoulder and tailing because of the increase of porosity with the variation rate 20. 7%. As a result, the retention time of nonreactive tracers increased 5.6%, while the interracial area decreased 6.8%.