Samples of raw coal, fly ash and bottom ash have been collected from a Chinese power plant together with laboratory ash obtained by ashing of the coal under 850 degrees C. Comparative-leaching experiments were carried out on each fraction under various pH conditions. A mathematical model for leaching of trace elements has been developed and leaching intensity (I,) has been calculated for each element. The results show that pH of the solution, leaching time, and particularly, properties and occurrence of the elements, have a strong influence on leaching behavior.