| Ferric oxide is the most abundant metal oxide, and it is very important in oxidization- reduction of soil and in soil-shaped process. Inundation is an in important factor in accelerating the invert of ferric oxide conformation. After inundation, microbe can use outside Fe(Ⅲ) as its electron acceptor, oxygenation its matrix(electron donor), thereby Fe(Ⅲ) deoxidize to Fe(Ⅱ).This process go by the name of dissimilatory reduction. It can affect availability of nutrients such as N,P,K and Si in the soil directly, and it is important to degradation of organic pollutant, Iron reduction is likely to a new available approach of soil decontamination. Therefore, the process is turned into a hotspot issue of soil environmental chemistry that studied the significance of dissimilatory reduction.The degree of iron reduction is restrained by the different electron acceptor and provider in the paddy slurry. Through adding organic matter, one way can increase the quantity of electron, at the same time, another way can change the ability of iron combination and dissolution. Making use of the characteristic of electron competition, as a valid way, may remove or reduce soil contamination.In this study, the soil samples were used in which red-oxy-reaction periodically occurred. The characteristics of iron reduction in different soil samples and different sized aggregates were investigated by flooding incubation in sealed vials at fixed temperature under airtight condition. We also investigated the differences of iron reduction in intact soil and organic exhausted paddy soil sample by adding acetate, propaniate and glucoses as electron donors and the differences of acetate, propaniate and glucose utilities in the dissimilatory iron reduction by microorganism from different soil samples, providing some scientific data and suggestion in dissimilatory iron reduction and its related environmental effects. The five paddy soil samples were collected from JiLin, HuNan, SiChuan, JiangXi, GuangDong.The main results in this study were showed as the following:1. The equilibrium concentrations of accumulative Fe(II) were differed from these soil samples, which were correlated with microorganism groups, labile iron oxidizes, other electron acceptors and electron donor spices. The accumulative Fe(II) in stable phase were different in these soil samples and followed the order: sample 1 (JL)> sample 3 (SC)>sample 5 (GD)> sample 4 (JX).2. Iron reducing rates were distinct in different phase of these soils. No obvious initial phase were found in sample(JL) and sample(SC), maybe for the reasons of higher incubation temperature(30℃). Microbial activities in JX and GD paddy soil samples showed an apparent initial phase. In the rapid reducing phase, the observed mean reducing rates were in the order of sample3(SC)>sample4(JX)>sample1(JL)>sample5(GD). In the stable phase of iron reduction, the mean reducing rates were no notable differences in all samples, but sample5(GD), and the higher reducing rate in sample5(GD) maybe the result of a higher content of Fe(III) oxides in it.3. The differences in different soil samples and different soil microaggregate were mainly determined by Fe(III) oxides forms, organic matter microbial groups and activities. The degree of iron reduction in different sized aggregates of all but GD paddy soils followed the similar order: (<0.001mm aggregates)>0.001～0.05mm aggregates)>0.05～0.25mm) aggregates. Iron reduction in the aggregates with the size of less than 0.001mm and 0.05 to 0.25mm in GD soil sample were limited by the availability of organic matter.4. The microbial iron reduction in the flooding soil were limited by the availability of electron donor as well as the electron acceptor. Iron reduction were notable stimulated by the addition of organic acid. Glucose showed a more significant stimulation with the addition of Fe(III) oxides. In the organic exhausted paddy soils, addition of acetate and propaniate stimulate the iron reduction in the beginning period but not in the stable period compared to...
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