CHEMISTRY OF DRINKING WATER OF NORTHERN THAILAND

Southeast Asia has some of the most contaminated drinking water in the world, tainted by arsenic (As) as well as other heavy metals and organic compounds. In some areas of the Bengal Aquifer System of Bangladesh, 21.4% of deaths are related to As, approximately the same as the U.S. death rate due to cancer. This study focuses on the drinking water chemistry of the Chaing Rai region, with particular emphasis on As concentrations. Thirty-three samples were taken for chemical analyses; 3 were well water samples and 30 were surface water samples. Electrical conductivity, salinity, pH, and redox potential were measured in the field at each sampling location. Initial results of geochemical analyses indicate that these water sources do not have dangerously high concentrations of As, with 7 samples showing less than 0.024 mg/L of As. The amounts of As in the samples tested were less than the World Health Organization standard in this country, which is 0.050 mg/L. Because of the mountainous terrain in the hill tribes’ villages where the water was tested, the people do not use as much groundwater as they do surface water. The surface water does not have the same opportunities as groundwater to become contaminated by As. The well water did show much higher redox potential and a lower pH than the average surface water sample. Understanding why this water is clean may be helpful in finding clean water for other parts of Southeast Asia.