20% of farmland soil in Chiang Rai river basins exceeds arsenic limits

Chiang Rai — A survey released on October 10 found that 20% of tested agricultural soil in the Kok, Sai, and Ruak river basins has arsenic levels exceeding the Department of Land Development's standard, while 50% requires monitoring. Director Parinyanon Thongkham stated that over 200 samples were collected from depths of 15-20 cm, near rivers (100-2000m from banks), to assess contamination in agricultural areas.

Soil is classified as green (<14mg/kg), yellow (14-25mg/kg, requiring monitoring), or red (>25mg/kg, exceeding standard). Preliminary results show 20% red, 50% yellow, and 30% green. Authorities plan regular follow-up sampling in red and yellow zones. Farmers in high-risk areas are advised to avoid growing food crops, particularly leaf or fruit-producing ones, and consider alternative crops like energy crops.

Experts urge clearer contamination maps, compensation for farmers, and transparency in soil testing results. They also caution against mixing contaminated soil into cement products and stress the need for continuous monitoring and safe processing of contaminated materials into construction materials.