CHIANG RAI – Scientists at the Synchrotron Light Research Institute have used advanced techniques to check the water in Chiang Rai’s Kok River. Their findings show that the amount of dissolved arsenic is below the safety limit set by Thai authorities.
The results suggest that the river water can be treated and used safely in homes and daily life.
Dr Sutthipong Wannapaiboon, a lead scientist at the institute, explained the process. Researchers received water samples collected by Chiang Rai Rajabhat University from different points along the Kok River, from the Phaya Mengrai Bridge to where the river meets the Mekong.
The team also studied water from the river’s branches (the Korn and Lao rivers), and took extra samples where the Kok joins the Mekong, both before and after their meeting.
There had been earlier reports of arsenic levels in the Kok River above safety standards. To get a clearer picture, the Synchrotron Institute checked what form the arsenic was in. This matters because different forms have different health risks.
Scientists separated the river samples into clear water and solid particles, then used a new method called Total Reflection X-Ray Fluorescence (TXRF), set up at their 7.2W beamline, to measure trace elements. This equipment can detect arsenic at levels as low as 1 part per billion, making it much more sensitive than traditional XRF tools.
Testing with Synchrotron-based TXRF revealed that the dissolved arsenic in filtered Kok River water is well below regulatory limits for surface water.
The suspended particles had higher arsenic, but after checking with X-ray Absorption Spectroscopy (XAS), most of this arsenic was found as arsenate (As(V)), which is more stable and less toxic than arsenite (As(III)). Normal water treatment methods can remove arsenate from suspended solids during filtration.
Further support for the research came from the National Science and Technology Development Agency, which worked with NIDA, RMUTL, and Mae Fah Luang University. The team sampled soil and sediment from 40 sites along the Kok River.
While they found some arsenic, about 84 percent was in the less harmful arsenate form. Only around 16 percent was the more toxic arsenite.
Dr Sutthipong summed up the findings. The tests using synchrotron light provided clear evidence that the dangerous, easily dissolved arsenic in the Kok River stays within limits set by authorities.
Most of the arsenic in river sediment is the less harmful type, and standard processes can remove it. These results give people living in Chiang Rai peace of mind and offer clear direction for future water treatment plans.
