• Journal of Soil and Groundwater Environment
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• v.11 no.4
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• pp.48-56
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• 2006

Using a continuous injection tracer test at a multi-soil layer deposit, the difference of hydrodynamic dispersions in unsaturated and saturated zones were analyzed through breakthrough curves of Rhodamine WT, linear regression of concentration versus time, concentration variation rates versus time, and concentration ratio according to the distance from injection well. As a result of continuous injection tracer test, the difference of the maximum concentrations of Rhodamine WT in unsaturated and saturated zones were 13-15 times after 160 hours, and the increased rate of concentration versus time in unsaturated zone was about 10 times higher than in saturated zone. The fluctuation of Rhodamine WT breakthrough curve and concentration variation rate with time in saturated zone were larger than in unsaturated zone. Rhodamine WT concentration ratio with the distance from the injection well in saturation zone was linearly decreased faster than in unsaturated zone, and the elapsed time necessary for the concentration ratio less than 2 was longer in saturation zone. The differences resulted from the lower concentration and slower hydrodynamic dispersion of Rhodamine WT at the saturation zone of the multi-soil layer deposit, in which groundwater flow significantly flow and aquifer materials have high hydraulic heterogeneity. Effective porosity, longitudinal and transverse dispersivities were estimated $10.19{\sim}10.50%,\;0.80{\sim}1.98m$ and $0.02{\sim}0.04m$, respectively. The field longitudinal dispersivity is over 12 times larger than the laboratory longitudinal dispersivity by the scale-dependent effect.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.168-171
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• 2003

연속주입추적자시험이 실시된 현장사이트의 규모는 4.5m$\times$4.5m$\times$6.0m 정도이다. 시험 사이트내에서 실시된 추적자시험은 주입공(Pl)에서 Rhodamine WT 50ppm 용액을 1.8$\ell$/min의 주입율로 6일 동안 연속적으로 주입함과 동시에 관측공(P2, P3, Il, I2, I3)에서 일정한 시간간격으로 지하수를 채수하여 추적자농도를 산출하였다. 시험결과, 지하수면 하부를 포함하는 관측공(P2, P3)의 최대추적자농도는 초기주입농도의 10% 정도이며, 지하수면 상부에 위치한 지하수공(Il, I2, I3)들에서의 최대추적자농도는 초기농도의 75% 정도로서 추적자의 농도차이가 상대적으로 매우 크게 나타났다. 본 연구에서는 자유면대수층내에서 포화대를 포함한 관측공과 비포화대만을 포함한 관측공에서의 수리분산특성에 대해 비교.분석한 결과, 오염물이 연속적으로 토양에 유입되는 경우 비포화대 구간에서는 이류기작에 의한 농도희석이 거의 없으므로 오염물농도가 매우 클 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.231-238
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• 2008

A column testing device capable of measuring the electrical resistivity of soil at 3 different locations was developed to verify applicability of bulk electrical conductivity (BEC) breakthrough curves in monitoring contaminant transport. Tracer injection tests were conducted with three different types of saturated sands to obtain average linear velocities and longitudinal hydrodynamic dispersion coefficients based on BEC breakthrough curves and effluent solute breakthrough curves. Comparative analysis of transport parameters obtained from curve fitting the results into the analytical solutions confirmed the validity of resistance measurements in estimating time-continuous resident solute concentration. Under the assumption that a linear relationship exists between ${\sigma}_{sat}-{\sigma}_w-C$, the BEC breakthrough curves are able to effectively reduce the laborious and time-consuming processes involved in the conventional method of sampling and analysis. In order to reduce possible uncertainties in analyzing the BEC breakthrough curves, it was recommended that resistance measurements take place nearby the effluent boundary. In addition, a sufficient electrical contrast or difference in the electrical conductivity of the influent and the saturating solution is required to conduct reliable analysis.