The Contamination of lead in Pattani river simulation by water analysis simulation program (WASP) version 6.2

Abstract

Lead contamination in Pattani River has been a topic of discussion over the past ten years. The source of lead in upstream section of the river is a group of abandoned tin mines in Bannangsta district, Yala Province. During the rainy season of every year, lead in the form of galena (PbS) is washed off from waste rock and sludge in the lagoon and into the upstream portion of Pattani River. The Water Quality Analysis Simulation Program (WASP 6.2) was selected to predict long-term distributions of the contaminant. A conceptual model of the lead contamination in the river was created. A simple scenario study demonstrated the high accuracy of the model. In the real contamination scenario, the predicted concentration was calibrated with the observed concentrations that were taken by the Department of Health from 1990-2000 and the Pollution Control Department in 2002. Statistical measures indicated a good fit between the predicted and observed concentrationwith the root mean square errors (RMSE) at about 0.014 mg/l. A strong correlation was found at three of the segments : in Bannangsta district and Muang district of Yala province, and Muang district of Pattani province. Advection, as determined by total stream flow, was identified as the major process that affects the distribution of total lead in the river. In application studies, it was found that waste loading should be reduced by about 10-30% in order to keep the total lead concentration at background levels normally found in the river. In addition, reducing the upstream flow was found to increase that total lead concentration. Thus, the level of upstream flow in the river is of concern and must be monitored, especially during the low-flow season