【摘要】 为探究重非水相液体(DNAPL)在地下水中的运移和溶出行为,选取四氯乙烯(PCE)为代表,采用透射光法动态监测PCE在二维砂箱中的运移和分布,并以顶空气相色谱法监测其质量溶出,在此基础上通过乙醇冲洗来改变PCE分布,对比分析相应源区结构和溶出浓度的变化.结果表明:PCE的运移以垂向入渗为主,并伴随由毛细管力引起的横向迁移;污染源区面积和溶出浓度的变化具有明显一致性,均先迅速增大而后趋于平稳,由于泄露量小,70.7%的PCE以ganglia态残留在运移路径上.乙醇主要通过增溶作用改变污染源区结构,对PCE的空间展布影响弱,乙醇冲洗后ganglia态PCE占比增至99.6%,GTP值从2.4增至257.随着乙醇冲洗体积的增加,PCE源区面积从100cm~2减至50cm~2,对应溶出浓度从114mg/L减至12mg/L,二者呈较好的线性关系(R~2=0.76).此外,连续监测结果显示,在本研究的实验条件下,无论是否经过乙醇冲洗,PCE污染源区结构和其相应的质量溶出可以在一定时间内(至少16PVs)保持稳定.更多还原

【Abstract】 To investigate the migration and dissolution of dense non-aqueous phase liquid(DNAPL) in groundwater, tetrachloroethylene(PCE) was selected as the representative in this study. The migration and distribution process of PCE in a two-dimensional(2-D) sandbox were dynamically monitored by light transmission method, while the PCE dissolution was determined using headspace gas chromatograph. Ethanol flushing was then performed to alter the PCE distribution in the sandbox, and the corresponding changes in source zone architecture and dissolution concentration were analysed. Results showed that the migration of PCE was mainly downwards vertical infiltration, accompanied by lateral spreading caused by capillary force. During the migration process, the changes of the PCE source area and the dissolved concentration were obviously consistent, both of which increased rapidly and then stabilized. Due to the small amount of leakage, 70.7% of the PCE was trapped in the migration path and existent as discontinuous ganglia. Ethanol flushing changed the source zone architecture mainly via solubilization, while it exhibited a weak influence on the spatial distribution of PCE. After being flushed with ethanol, the percentage of ganglia PCE increased to 99.6%, and the GTP value increased from 2.4 to 257. With the increase of ethanol flushing volumes, the PCE source zone area decreased from 100 cm~2 to 50 cm~2 and the dissolved concentration decreased from 114 mg/L to 12 mg/L, and the two showed a good relationship(R~2=0.76). In addition, continuous monitoring results showed that in the current study, the source zone architecture and dissolution of PCE could remain stable for a certain period of time(at least 16 PVs), regardless of whether it was flushed with ethanol or not.更多还原