Transport modeling of cadmium contaminated suspended sediment and bed load in Mae Tao Creek, Thailand

Abstract

Mae Tao Creek, Mae sot district, Tak Province is contaminated with high cadmium levels. Stream sediment include bed load and suspended sediment are the main process of cadmium transport in Mae Tao Creek. This research was focused on cadmium transport via bed load and suspended sediment during the wet and dry seasons in Mae Tao Creek. Cadmium concentration of bed load and suspended sediment and grain size distribution of bed load at 10 monitoring station along Mat Tao Creek were quantified in the wet and dry seasons. MIKE 11, suggested as an appropriate model for study area, was used to model the channel flow from amount of rainfall, one-dimensional transport in the creek, and calculate sediment transport by water flow. The time series of water depth from May 2010 to February 2011 were used to calibrate the channel flow. The reliability of hydrodynamic results was evaluated based on the correlation coefficient (CC) and root mean square error (RMSE). The CC and RMSE value obtained during this study are 0.85 and 0.06 meter respectively. The hydrodynamic results were inputted into the ST module to obtain the rate of bed load and suspended sediment transport. Finally, the sediment transport results and measured cadmium concentrations were calculated to estimate the cadmium transport in the area. From the results, cadmium transport out of Mae Tao Creek during from May 2010 to February 2011 was approximately 20.74 kg. Moreover, the spread of cadmium contamination depended on creek discharge and mainly occurred during wet season. Moreover, suspended sediment was a dominant process of cadmium transport in Mae Tao Creek in both the wet and dry seasons.