Chitsan Lin, Sheng-Yu Chen Department of Marine Environmental Engineering, National Kaohsiung Marine University, Kaohsiung 81157, Taiwan / 05 / 25 1

Outline  Introduction  Model Overview  Results and Discussion  Conclusions 2

Introduction 3

In recent years, there are more and more soil and groundwater pollution sites are shown up. It is not easy to reduce pollution, especial pollutant in the groundwater. Therefore, the goal of the study is to simulate pollutant transportation to understand pollutant track in the groundwater. 4

The contaminated site is in Renwu District of Kaohsiung City, southern Taiwan. study site plant A plant B Renwu Taiwan Site 5

Results of the soil texture investigation indicate there is silt layer between 0-3 meters (depth), sand mixed clay or silt between 3-12 meters, and clay layer under 12 meters. 6

The goal of this study is to simulate the transportation of 1,2-dichloroethane in groundwater. MODFLOW → groundwater flow MT3DMS → contaminants transfer combine 7

Model Overview 8

MODFLOW MODFLOW is the U.S. Geological Survey modular finite- difference flow model, which is a computer code that solves the groundwater flow equation. The program is used by hydrogeologists to simulate the flow of groundwater through aquifers.  K xx,K yy,K zz : hydraulic Conductivity (LT -1 )  H : Hydraulic head (L)  W : Volumetric Flux (T -1 )  S s : Specific Storage (L -1 )  t : time 9

MT3DMS MT3D is one of the widely used three-dimensional groundwater contaminants transfer model software, after MT3D was greatly expanded and improved, modified the procedure re-named the MT3DMS.  C : the concentration of contaminants dissolved in groundwater (ML -3 )  D ij : the dispersion coefficient tensor (L 2 T -1 )  v i : flow velocity in the aquifer (LT -1 )  q s : the volume flux of the solute (T -1 )  θ : effective porosity of the aquifer  C s : the concentrations of sources or sinks (ML -3 )  is a parameter to adjust chemical reaction during the transport (ML -3 T -1 )  t : time 10

Results and Discussion 11

The simulation of steady-state groundwater flow plant B plant A groundwater flow  The initial condition of groundwater level to simulate Steady-state groundwater flow is according the average groundwater level in  Steady-state groundwater dispersion after simulating and calibrating is to be the initial condition to simulate temporary-state groundwater flow. 12

The simulation of steady-state groundwater flow  The maximal error of simulated groundwater level is m  Average error : m  The average absolute error : m  RMS error : m  Pearson correlation coefficient is

1,2-Dichloroethane pollution transport simulation results  Pollutants : 1,2-dichloroethane  Simulated situations : sources of pollution continued to leak  Simulated times : 1975 ~ 2010  Half life of 1,2-dichloroethane : 100 ~ 360 days  Assume that the pollution leakage rate plant A (1990) : kg/day plant B (1975) : kg/day  Result : the longest distance of transportation is 500 meters plant B plant A 2010 Unit ： mg/L 14

Conclusions 15

Estimated 1,2-dichloroethane discharge into the groundwater was about kg/day for plant B, and of kg/day for that of plant A. Assuming the half-life of 1,2-dichloroethane in the groundwater environment is 360 days, the simulated result shows longest distance of transportation is 500 meters from the source. 16

As a summary, our research indicate these two models can assist remedial engineers to define the scope of pollution and to estimate the total quantity of the contaminant. 17

Department of Marine Environmental Engineering, National Kaohsiung Marine University 18