Thesis (M.Sc.) - Asian Institute of Technology, 2003

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science.

In Thailand Ron Phibun, Ron Phibun sub strict, Nakhon Si Thammat province is the place where arsenic contamination has occurred and been reported. Arsenic was generated from the process of refinery and dumped into dredging site and river. It is estimated that arsenic contamination in Ron Phibun has become wide-spread throughout these dumping sites. Besides highly contaminated groundwater was detected from the tube well near by the first patient home. According to the research result the average arsenic content in soil and surface water of dumping sites was about 500 mg/kg(ppm), with maximum value at 5309mg/kg(ppm), and 1.85 mg/l(ppm) respectively. The chemical species of arsenic are particularly important in the sediment-water phases. Change in sediment environment, i.e., a transition from anaerobic to aerobic conditions, which refers to oxidation and reduction potential (ORP), or vice versa, and pH, may involve a change in chemical species, and thereby alter the environmental arsenic behavior such as speciation and solubility (Masscheleyn, et al., 1991). Grafe, et al., (2001) concluded that the presence of dissolved organic carbon(DOC) may compete with arsenic for adsorption on mineral surface, hence increasing its potential bioavailability. This study defines the comprehensive interrelation between arsenic remobilization and corresponding environmental factors and provides the scientific information to the decision makers.