Assessment of Cadmium Migration into Groundwater in Mae Sot District, Tak Province using Monte Carlo Technique

Abstract

Mae Sot is a district in Tak province that confronts Cd contamination within the area. The target organs for Cd exposure was kidneys and skeletal system which could lead to severe health effects such as renal dysfunction, osteoporosis, bone softening, Itai-Itai disease, and lung cancer. The intention of this study was to examine the sorption behavior of nine soil samples in the study area and applied Monte Carlo technique that would increase model efficiency for Cd migration in to the soil profile. Batch adsorption experiments were performed and fitted with the adsorption isotherms as follows: Linear, Langmuir, and Freundlich isotherms. Moreover, BCR sequential extraction was used to extract bioavailable Cd (BCR1+ BCR2), which used as model initial Cd concentration and Cd concentration in soil profile. HYDRUS-1D was used as a numerical modeling instrument to simulate Cd transportation in the soil profile, and MATLAB was used for Monte Carlo application in HYDRUS-1D. Furthermore, Nash and Sutcliffe model efficiency (NSE) was used to evaluated the numerical model in this study. Batch adsorption experiment showed that seven soil samples were fitted well with Freundlich adsorption isotherm (R2 between 0.957-0.984), while the other two soil samples (S1 and S2) were explained by Langmuir isotherm (R2 between 0.995-0.998). However, BCR sequential extraction from soil samples showed that only 2 soil samples (S4 and S5) can be detected Cd concentration in BCR1 and BCR2 Based on the application of Monte Carlo method in HYDRUS-1D (under the non-equilibrium condition), the result showed that the simulation results are lower than the experimental data with NSE values of 0.223 and -1.606 for S4 and S5, respectively.