| The process of iron oxidation and reduction is an important characteristic of paddy slurry. Especially, the process of iron reduction has not only an important effect on the basic attribute of paddy slurry but also an unusual significance in the way of soil environment chemistry. Iron oxide, as an electron acceptor, may promote to reduce organic matter in the paddy slurry, competitively restrain the change from organic matter to methane, and have an important effect on the let of methane in the paddy slurry. 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. Among the different electron acceptors, the difference of the ability of oxidation and reduction decide the direction of electron transfer. Making use of the characteristic of electron competition, as a valid way, may remove or reduce soil contamination.My experiment chooses some representative paddy slurries as the specimen of experiment from four provinces. Through the experiment of constant temperature incubation under airtight, I study the effect of adding three organic matter of EDTA, fulvic acid and sodium acetate, and the electron acceptors of NO3-, SO42- and Cr(VI) on iron reduction in the paddy slurries. At the same time, I also compare these factors of affecting iron reduction such as the water quantity and temperature. I may obtain these primary results as follows:1. Comparing the ability of iron reduction on the four paddy slurries, the reduction ability of Jilin and Guangdong soil is bigger more than that of other soil, while Jiangxi soil is the least. This suggests that different soils have different quantity of iron oxide that is easy to be reduced, and the different dgree of iron oxide that is used by the microbe. Through the experiment of adding iron oxide, we find that Fe (II) quantity is obviously increased in the four soils, which make clear that the soil has the stronger ability of microbial reduction.2. When the temperature rises, both the quantity and speed of iron reduction is largely promoted. Among the four soils, the temperature has the biggest effect on Jilin soil. Following the ratio of water and soil rising, whether iron oxide is added, or not, which can obviously promote iron reduction.3. After adding these electron acceptors such as NO3-,SO42- and Cr (VI) , NO3- and Cr (VI) can obviously restrain the function of iron reduction, while SO42- doesn't have anobvious effect on iron reduction. NO- reduction may straightly compete the electron provider, while Cr (VI) reduction is through the way that consume Fe(II) in the soil. So iron reduction may reduce Cr (VI) as a valid way in the soil.4. After adding some organic matters such as fulvic acid and sodium acetate, the iron reduction of Jilin and Guangdong soil is obviously increased, and the function of sodium acetate was more than that of fulvic acid. While in the Sichuan and Jiangxi soil the addition of fulvic acid and sodium acetate gave rise to the influence of the iron reduction that was not different to the contrast, this suggests that the kind of organic matters have an obvious effect on iron reduction in the different soils.5. The methane production is different in the soil, and adding iron oxide has an obvious effect on the let of greenhouse gas. Under the condition of flooded incubation, the ability of methanogenesis was Sichuan paddy > Jiangxi paddy > Jilin paddy > Guangdong paddy. Adding iron oxide may restrain the production of Cm and CO2.6. The quantity of N2O production in the Guangdong soil is more than that in other soils. In the Jilin, Sicuan and Jiangxi soils, N2O is immediately disappearing in the two days, while the let pinnacle of methane, in the Guangdong soil, may go on for seven days. This suggests that soil quality has an obvious effect on the N2O production.
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