A US expert in the rehabilitation of contaminated environments is currently in Chiang Rai province to advise and share his experience with Thai counterparts on how to cope with toxic substances being discharged into the Kok and Sai rivers by mining activities in Myanmar, which are flowing into Thailand.
The US expert, Professor Danny Reible of Texas Tech University, conducted a field trip to the Kok and Sai rivers in Chiang Rai and Chiang Mai provinces, accompanied by Dr Thanaphol Penrat of the Thailand Science, Research and Innovation (TSRI) office, and Dr Suebsakun Kidnukorn of Mae Fah Luang University.
Dr Thanaphol said the most important step in stopping cross-border pollution is containing the problem at its source in Myanmar. While this has yet to be done, he said it is necessary to reduce contamination and the accumulation of pollutants in farmland in Chiang Mai and Chiang Rai.
He said previous soil sample tests in Mae Sai district, Chiang Rai, show that contamination remains within safe standards and that vegetables and fruit are still safe for consumption. However, he warned this may change if toxic substances continue to be carried downstream into Thailand.
Dr Thanaphol proposed building dikes to block sediments, citing the Sai River as an example and suggesting the approach could also be applied to the Kok River and other tributaries.
Dr Reible said that if discharges from mining operations cannot be addressed at the source, the problem could be difficult to resolve in Thailand, especially if water flow is strong.
He said it is important first to determine whether most toxic substances are suspended in the water or have settled in sediments, noting that sediments are comparatively easier to manage.
Meanwhile, Dr Suebsakun pointed out that if it can be proven the contaminants originate from mining operations, the Myanmar and Chinese governments should be involved in addressing the problem.
According to the Pollution Control Department, water samples collected between May 19 and 22 from 22 locations in Chiang Rai and Chiang Mai—including the Kok, Sai, Ruak and Mekong rivers—show that water quality does not meet standards, with arsenic levels exceeding 0.010 mg/L. Levels of other heavy metals such as cadmium, nickel, chromium, zinc and mercury remain within acceptable limits.
