| Abstract: | In this study, the kinetics of soil organic matter (SOM) dissolution from soil samples in different states of moisture was investigated, using a continuous extraction method. The investigation distinguished three processes of SOM dissolution. They include an initial, fast process (probably hydrophilic dissolved organic matter) and two slow, rate limited processes, which probably correspond to hydrophobic dissolved organic matter (DOM). The second process indicates a slow, continuous release of DOM, whereas the third process is determined by a power law. The rate of the third process strongly depends on temperature and state of moisture. It is diffusion limited, with the diffusion control probably being located in the solid soil organic matter. This was explained by a gel structure, which slowly forms in the hydrating SOM and allows diffusion of mobile particles of SOM. The results show the importance of considering the moisture state of SOM for the kinetics of DOM dissolution. |
