The three speciations(water extract, adsorption and organic speciations) of Cu, Zn, Fe and Mn in geo-chemical samples were determined by fuzzy cluster-artificial neural network(FC-ANN) method coupled with atomic absorption spectrometry. A back-propagation artificial neural network with one input node and three export nodes was constructed, which could forecaste three speciations of heavy metals simultaneously. In the learning sample set, the three speciations of each element were allowed to change in a wide concentration range and the accuracy of the analysis was apparently increased via the learning sample set optimized with the help of the fuzzy cluster analysis. The average relative errors of the three speciations of Cu, Zn, Fe or Mn from 100 geo-chemical samples were less than 5%. The relative standard deviations of the three speciations of each of four heavy metals were 0.008%―4.43%.
