Conclusions
The results demonstrate the stability of residual cyanides and low potential of cyanide to be released into the environment, especially tailings deposited in TSF for a period of time. Strong metal cyanide complexes especially iron cyanide complexes are predominantly presented in the tailings although there are lesser pro-portion of CNFree and CNWAD which are un-stable forms because they can volatilize and undergo biodegradation through natural cya-nide attenuation processes. The pH of the tailings is neutral to slightly alkaline which is unfavourable to strong cyanide complexes dis-sociation. From the results of NAG test, tailings have a low to non-acid forming potential to generate high acidity to dissociate strong metal cyanide complexes and release free cyanide, which is its most toxic form. CNT concentra-tions in tailings are very low compared to Thai Environmental Regulations of Soil Quality Standards, indicating that it is not environ-mentally significant.