土壤微团聚体中氧化铁的异化还原能力

Potential of dissimilatory iron(Ⅲ) reduction in the soil microaggregate

选取有代表性的吉林、湖南、四川和广东4个省份的水稻土,采用超声波分散提取不同粒级的微团聚体,通过30℃恒温厌氧培养,测定培养过程中Fe( )产生量的变化。结果表明,不同土壤中铁还原程度大小与土壤的地带性分布有一定关系,吉林和四川水稻土中铁还原量大,而湖南和广东水稻土中铁还原量较小;对不同大小的微团聚体来说,除广东水稻土外,不同大小的微团聚体之间的铁还原程度均表现为:<0.001mm的微团聚体(14～35mg/g)>0.001～0.05mm的微团聚体(5～15mg/g)>0.05～0.25mm的微团聚(<6mg/g);不同组分中的铁还原主要由盐酸可溶性氧化铁的数量决定,不同土壤及不同团聚体中铁还原差异主要是由不同组分中氧化铁的化学形态决定。对于广东水稻土,其<0.001mm和0.05～0.25mm的微团聚体中的有机质数量可能是限制铁还原的关键因素。

The typical paddy soil samples from four different provinces:Jilin,Hunan,Sichuang,and Guangdong were dispersed in ultrasonic bath,and then collected the different sized aggregate which were incubated as slurries at 30 ℃ under anoxic condition.Acid extractable ferric iron concentration in the soil slurries was determined during the incubation.The results suggested,in different soils,the potential of iron(Ⅲ) reduction was in relation to district distribution of soil.Fe(Ⅱ) production in Jilin and Sichuang is bigger than Hunan and Guangdong paddy soils.In regard to different sizes,except Guangdong paddy soil,the extent of iron(Ⅲ) reduction followed:<0.001 mm soil microaggregate (14-35 mg/g) >001-0.05 mm soil microaggregate (5-15 mg/g) >0.05-0.25 mm soil microaggregate (<6 mg/g).These differences were decided by the iron oxide solubility in hydrochloric acid.In the different soils and soil aggregates,the form of iron oxide in different constituents mainly decided the difference of iron reduction.In regard to Guangdong paddy soil,its amount of organic matter in <0.001 mm soil microaggregate and 0.05-0.25 mm soil microaggregate may be the key limiting factor for the iron(Ⅲ) reduction.