不同土地利用方式下土壤腐殖质作为胞外电子穿梭体的持续能力分析

由于腐殖质的氧化还原活性官能团可以在连续的缺氧和有氧交替中将电子从微生物可持续地传递到氧气，土地利用方式可以影响土壤腐殖质的电子转移能力，但土地利用方式是否会影响土壤腐殖质作为胞外电子穿梭体的持续能力尚不明晰.选取水稻地、葡萄园和杨梅园的土壤，采用微生物还原和氧气氧化的循环周期试验，评估土壤中胡敏酸(HA)和富里酸(FA)作为胞外电子穿梭体的持续能力对不同土地利用方式土壤的响应.结果表明:土壤腐殖质作为胞外电子穿梭体的持续能力在Shewanella oneidensis MR-1和Shewanella putrefaciens 200两种微生物体系下并无明显差异，但在水稻地、葡萄园和杨梅园间具有显著差异.水稻地、葡萄园和杨梅园土壤中HA作为胞外电子穿梭体的持续能力分别为75.9%、80.5%和72.1%，FA作为胞外电子穿梭体的持续能力分别为58.2%、62.2%和62.9%.该结果可能是由不同土地利用方式下土壤腐殖质的组成、分解和转化过程以及微生物电子供体碳源驱动的动力学过程差异造成的.研究显示，不同土地利用方式下腐殖质作为胞外电子穿梭体的持续能力具有显著差异，且HA作为胞外电子穿梭体的持续能力明显强于FA，可通过环境调控措施形成HA，以实现土壤污染物的降解转化. 

Sustainability of Soil Humic Substances as Extracellular Electron Shuttle in Different Types of Land Use

The redox-active functional groups of soil humic substances (HS) can continuously transfer electrons from microorganisms to oxygen in continuous anoxic and aerobic alternations. Therefore, HS is essential for regulating the methane cycle in the temporary anoxic system. Land-use types could affect the electron transferability of soil HS. However, it remains unclear whether the land-use types would affect the sustainability of HS as the extracellular electron shuttle. In this study, we combined the cycle test of microbial reduction and oxygen re-oxidation to evaluate the response of soil humic acid (HA) and fulvic acid (FA) sustainability as the extracellular electron shuttle to different types of land use. The results showed that HS sustainability as the extracellular electron shuttle did not differ significantly between Shewanella oneidensis MR-1 and Shewanella putrefaciens 200 microbial systems, although significant differences could be observed among the land-use types of paddy (ST), grapevine (PT), and myrica rubra (YM). The HA sustainability as an extracellular electronic shuttle in ST, PT, and YM was 75.9%, 80.5% and 72.1%, respectively. The FA sustainability as an extracellular electronic shuttle was 58.2%, 62.2% and 62.9%, respectively. These results might be due to different types of land use, resulting in different soil HS composition, decomposition, and transformation processes, and different dynamic processes driven by microbial electron donor carbon sources. Our results showed that the sustainability of soil HS as an extracellular electronic shuttle was significantly different among the different types of land use, and HA sustainability as an extracellular electronic shuttle was obviously greater than that of FA. Therefore, the degradation and transformation of soil pollutants could be achieved by improving the environmental control measures to form HA.