Kinetic Characterization Of Reductive Reactivity Of Iron(Ⅲ) Oxides In Sediments Of The East China Sea

Iron is sensitive metallic elements in redox, the content and morphology of ironoxide in marine sediments play an important role in the circulation of carbon, sulfur,phosphorus and other trace elements. In order to understand a more nuanced pictureof reactivity and kinetic manner of iron(Ⅲ) oxides and the change of morphology ofiron oxide kinetic experiments and reactive continuum model were combined tocharacterize reductive reactivity of iron(Ⅲ) oxides in surface and core sediments ofthe East China Sea. Three kinetic parameters, i.e., theoretical amounts of reactiveiron(Ⅲ) oxides (m0), apparent rate constants (k’), and heterogeneity of reactivity)(, were obtained by fitting kinetic data to the reactive continuum model.(1)The results show that m0values in the surface sediments are within a narrowrange (26.14~60.51mol/g). The normalized initial rates (J/m0=k’), whichcharacterize the kinetic behavior of highly reactive iron(Ⅲ) oxides, are also within anarrow range, with the highest initial rate being only7.25times the lowest. But theheterogeneity of reductive reactivity of iron(Ⅲ) oxides in the surface sedimentsdisplays a wide range of variability. The kinetic rates after90%dissolution ofiron(Ⅲ) oxides are2~4orders of magnitude lower than the initial rates. Thevalues of m0, k’, and for the core of0702decrease with depth, and displaygenerally good linear relationships between each other, which could be attributed todiagenetic cycling of iron in the sediments. However, no correlations among m0, k’and were observed in the surface sediments and the core0802. In comparison withtraditional chemical extraction methods, the reactive continuum model allows a morenuanced picture of reactivity and kinetic manner of iron(Ⅲ) oxides.(2)The kinetic parameters theoretical amounts of bioavailability reactive iron(Ⅲ)oxides (m0), were obtained by the surface sediments in buffered ascorbate-citratesolution (pH7.5). The results show that a high spatial correlation between m0values in the surface sediments and FeT、Fe(Ⅲ)HR、FePRS、FeHR. Values of pH can not lead thekinetic parameters m0and k’ obtained by the different sediments to high or low.In thesame sediments the kinetic parameter m0is high when the values of pH is low.(3)The results show that three kinetic parameters, i.e., theoretical amounts ofreactive iron(Ⅲ) oxides (m0), apparent rate constants (k’), and heterogeneity ofreactivity (), were all fall at different degree with redox treatment time after time.Three kinetic parameters will keep steadily when redox times were enough. It must beproduced some iron(Ⅲ) oxides that are different at specific surface area,mineralogyand crystallinity.