Influences Of Al3+、Fe3+、Cu2+ and Zn2+ On Dissolved Soil Organic Matters Sorption By Ferrihydrite.

Dissolved organic matters (DOM) can modify the surface properties of the soil minerals and regulate indirectly the mobility and bioavailability of organic and inorganic contaminants. On the other hand, intimate associations of soil minerals with DOM may protect these organic molecules against biodegradation, influencing indirectly the biogeochemical carbon cycle in soils. These reactions can be modified by the presence of multivalent metal cations because of the formation of stable metal-organic complexes. In the study, the sorption/desorption of DOMs, derived from two peat soils of Changhua (CHA) and Yangminshan (YS), on the surfaces of ferrihydrite as influenced by specific multivalent cations, such as Al, Fe, Cu, and Zn, were examined. Results showed that low concentrations (i.e., 0.1 mM) of metals were not capable of increasing CHA- and YS-DOM sorption by ferrihydrite. Besides, no discernible increases of YS-DOM sorption were observed with the addition of higher concentrations of foreign metals due probably to the presence of high concentrations of Fe and Al in the pristine YS-DOM (provide Fe and Al concentrations in YS-DOM with the units of mg/g or mg/g C here) However, a significant increase of CHA-DOM sorption was observed with an increase of the metal concentration up to 1 mM, particularly in the system with Fe³⁺ and Al³⁺. The formations of insoluble metal-DOM complexes with a higher metal/C ratio may be responsible for the increase of DOM sorption on ferrihydrite surfaces. The Fe/Al cations exhibited not only the higher enhancements of DOM sorption but also a greater inhibition of DOM desorption from ferrihydrite.