水稻土中铁氧化还原循环的光照水分效应

水稻土中铁的氧化还原循环与CO2和CH4排放关系密切。采用恒温厌氧培养试验分别在黑暗、光照条件下研究了不同水分状况对水稻土中铁氧化还原过程、水溶性碳含量及CO2和CH4排放的影响。结果表明,水分和光照是调控土壤铁氧化还原过程及其耦合的碳转化过程的关键环境因子。避光时增加含水量缩短铁还原最大速率出现的时间,促进CH4排放。光照条件下含水量小于50%时增加含水量可促进亚铁的再氧化,大于50%时则抑制了亚铁的再氧化。避光时增加含水量可增加体系的水溶性无机碳含量(WSIC),WSIC与CH4的排放存在显著正相关关系。光照可显著降低体系的WSIC,降低幅度随含水量的增加而增大。在含水量25%～200%范围内,光照可使CO2和CH4排放量分别降低95.80%和96.08%。

Effect of illumination and water condition on iron redox cycle in paddy soil

Samples of paddy soil were prepared into slurry with different water content and then incubated anaerobically at a constant temperature for exploration of effects of water content on redox of iron in the soil under dark and illumination, respectively. Water soluble carbon in the soil, CO2 and CH4 emission amount were analyzed at the end of the incubation for relationship among water content, illumination, anaerobic redox process of iron and carbon transformation in the paddy soil. Results showed that water content and illumination are key environmental factors regulating geomicrobiological cycling of iron and the coupled carbon transformation. The period max iron reduced velocity appeared was cut down, and CH4 emission was promoted with increasing water content under dark. Ferrous iron re-oxidation was promoted by increasing water content under illumination when water content is less than 50%, and inhibitive effect appears while water content exceeded. Water soluble inorganic carbon (WSIC) increased with increasing water content under dark, and a significant relationship between WSIC and CH4 emission was observed. WSIC decreased dramatically while the soil was illuminated and the decreasing amplitude increased with increasing water content. CO2 and CH4 emission was significantly inhibited when illumination last for the whole incubation with water content varied from 25% to 200%, with decreasing amplitude of 95.80% for CO2 and of 96.08% for CH4, respectively.