STUDY ON THE ACTIVATION PROCESS OF IRON OXIDES IN SOIL
Chen Jiafang, He Qun Shao Zongchen(Institute of Soil Science, Academia Sinica, Nanjing)
The present paper deals firstly with the indexes of activation of iron oxides in soil on the basis of the data from previous paper and reference literatures. It is considered that the change of activity of iron oxides in soil may be summarized as activation and aging. Though the change is not a reversible reaction, the aged iron oxides can be activated by the action of organic matter and atmospheric factor. It is also considered that mineralogical patterns can not reflect quantitatively the change of activity of iron oxides; however, it can be estimated quantitatively to a certain degree by the content of amorphous iron oxides.The possible pathways of activation of iron oxides in soil are then discussed. Synthetic iron oxides and incubated soil samples were used for the experiment. The results showed that there was positive correlation between the content of amorphous iron oxides and amount of hydroxy released from synthetic iron oxides with a correlation coefficient of 0.81 (n=10), and the pH value of the systeta of synthetic iron oxides-water was correlated negatively with the degree of activation of iron oxides (r=-0.956, n=10). However, the soil samples are more complex as shown in Fig. 1 and 2. In addition to reduction and hydrolysis, the equations 2 to 5 in the present paper may be considered as the possible pathways of activation of iron oxides in soil.