Heavy metal ions in the soil samples were extracted by acid mixture (1N HCl/1N H2SO4) according to
Perkins (1970). Concentrations of Cd, Cr, Pb, Cu, Ni, and Zn in the extractants were then determined by
atomic absorption spectrophotometry (GBC AVANTA).
Current situation of cadmium-polluted paddy soil, rice
and soybean in the Mae Sot District, Tak Province,
Thailand