紫云英水溶性有机物促进淹水土壤中五氯酚还原与铁还原

Dissolved Organic Matter from Chinese Milk Vetch(Astragalus sinicus L.)Enhances Pentachlorophenol Reductive Transformation and Iron Reduction in a Flooded Paddy Soil

以潜育水耕人为土为供试土壤,以不同的处理方式和培养时间下产生的紫云英水溶性有机物(DOM)为添加物(包括新鲜紫云英DOM、淹水腐解7 d和14 d紫云英DOM、好气腐解7 d和14 d紫云英DOM;800 mg C·L-1),研究了5种DOM作为有机碳源促进淹水土壤中五氯酚(PCP)还原转化与Fe(Ⅱ)累积的关系。结果表明,紫云英DOM在淹水6.5 d后均可显著促进PCP的还原(P<0.05),淹水2 d后显著促进了乙酸钠提取态Fe(Ⅱ)[Fe(Ⅱ)NaOAc]和乙酸钠+盐酸连续提取态Fe(Ⅱ)[Fe(Ⅱ)NaOAc+HCl]的累积(P0.05);多数情况下还可促进乙酸钠提取态Fe(Ⅲ)[Fe(Ⅲ)NaOAc]的累积;多元线性回归分析发现,PCP还原主要受Fe(Ⅱ)NaOAc+HCl影响其逐步回归模型为:PCP(mg·kg-1)=22.95-0.047Fe(Ⅱ)NaOAc+HC(lmg·kg-1)(R2=0.615,P<0.01)。因此,DOM促进了淹水土壤中PCP还原与铁还原,Fe(Ⅱ)累积是导致PCP还原转化的主要化学机制。

This study investigated the effects of dissolved organic matter（DOM）from green manure on pentachloropheno（lPCP）reductive transformation and Fe（Ⅲ）reduction under flooded soil conditions. Batch experiments were conducted to explore the kinetics of PCP reductive transformation and its relationship with Fe（Ⅱ）accumulation in a flooded paddy soil（Gleyi-Stagnic Anthrosol）amended with fresh or decomposed（continuously-flooded,CF or non-flooded,NF;7 and 14 d）DOM from Chinese milk vetch（Astragalus sinicus L.,CMV;800 mg C·L^-1）. The 5 treatments of CMV-derived DOM（CMV-DOM）significantly enhanced the reductive transformation of PCP and the accumulation of NaOAc-extractable or sequential NaOAc- and HCl-extractable Fe（Ⅱ）[Fe（Ⅱ）NaOAc ＋HCl] after 6.5 and 2 d of flooding,respectively（P〈0.05）. In most cases,the addition of CMV-DOM greatly increased NaOAc-extractable Fe（Ⅲ）owing to nonreductive dissolution. The relationship between reduction kinetics and selected environmental variables was examined by correlation analysis and regression analysis. Sequential NaOAc- and HCl- extractable Fe（Ⅱ）was found playing a vital role in PCP reductive transformation,and a stepwise regression model was established as follows：PCP（mg·kg^-1）=22.95-0.047Fe（Ⅱ）1NaOAc＋HC（lmg·kg^-1）（R^2=0.615,P〈0.01）. The results demonstrated that addition of CMV-DOM accelerated PCP reductive transformation and Fe（Ⅲ）reduction in the flooded paddy soil. In terms of soil chemistry,enhanced PCP reductive transformation in flooded paddy soil is attributable to generation of adsorbed Fe（Ⅱ）with high redox activity.