Environmental geochemistry significance of organic phosphorus: An insight from its adsorption on iron oxides

Iron oxides in suspended particulate matter or bottom sediments can remove P from natural waters via sorption, rendering it unavailable for biological uptake. In this work, three dissolved OP compounds, were selected as adsorbents to investigate their adsorption behavior on two typical iron oxides. The results showed that the formation of nonprotonated and protonated bidentate complexes were the dominant mechanisms in the initial stage (∼10 min) and the following stage (10-1440 min) during the adsorption process, respectively, in which the formation of protonated bidentate complex is the dominant mechanism in the whole adsorption process. Moreover, the adsorption density of P compounds on iron minerals increased with the temperature increase, indicating the endothermic and spontaneous of the adsorption process; pH presented negative effects on the adsorption of P-compounds on both hematite and goethite. Low molecular weight acid (LMWOAs) suppressed the adsorption of P compounds and the inhibitory effects increased with the number of carboxyl groups and the molecular size increasing. On the basis of this work, it can be deduced that P level will be largely elevated in water column from the WLSH-like lakes due to that the alkalization of water, the flourish of macrophyte and the icebound effects presented negative effects on P adsorption towards Fe oxyhydroxides in sediments. This work helps to interpret the knowledge linkage regarding the factors driving OP compounds behavior and bioavailability in lake ecosystem.