2012 International Conference on Environmental Quality Concern, Control and Conservation Simulation of Chlorinated Solvents Transport in the Groundwater Contamination Site Chitsan Lin, Sheng-Yu Chen Department of Marine Environmental Engineering, National Kaohsiung Marine University, Kaohsiung 81157, Taiwan. 2012 / 05 / 25
Outline • Introduction • Model Overview • Results and Discussion • Conclusions
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.
The contaminated site is in Renwu District of Kaohsiung City, southern Taiwan. Taiwan Site Renwu study site plant A plant B
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.
The goal of this study is to simulate the transportation of 1,2-dichloroethane in groundwater. • MODFLOW →groundwater flow • MT3DMS →contaminants transfer combine
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. • Kxx,Kyy,Kzz : hydraulic Conductivity (LT-1) • H : Hydraulic head (L) • W : Volumetric Flux (T-1) • Ss : Specific Storage (L-1) • t : time
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) • Dij : the dispersion coefficient tensor (L2T-1) • vi : flow velocity in the aquifer (LT-1) • qs : the volume flux of the solute (T-1) • θ : effective porosity of the aquifer • Cs : the concentrations of sources or sinks (ML-3) • is a parameter to adjust chemical reaction during the transport (ML-3T-1) • t : time
The simulation of steady-state groundwater flow • The initial condition of groundwater level to simulate Steady-state groundwater flow is according the average groundwater level in 2010. • Steady-state groundwater dispersion after simulating and calibrating is to be the initial condition to simulate temporary-state groundwater flow. groundwater flow plant A plant B
The simulation of steady-state groundwater flow • The maximal error of simulated groundwater level is 0.363 m • Average error : 0.072 m • The average absolute error : 0.164 m • RMS error : 0.191m • Pearson correlation coefficientis 0.9338
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) : 19.04 kg/day • plant B (1975) : 11.90 kg/day • Result : the longest distance of transportation is 500 meters 2010 plant A plant B Unit：mg/L
Estimated 1,2-dichloroethane discharge into the groundwater was about 11.90 kg/day for plant B, and of 19.04 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.
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.
Department of Marine Environmental Engineering, National Kaohsiung Marine University Thanks for your attention