植物多酚与低分子量有机酸联合作用对紫色土铁形态分布的影响

植物多酚(PP)和低分子量有机酸(LMWOA)对土壤铁形态转化有重要影响。以酸性、中性和石灰性紫色土为研究对象,采用不完全随机区组试验,用2种PP(即表没食子儿茶素没食子酸酯(EGCG)和芦丁)和2种LMWOA(即柠檬酸和草酸)溶液浸提供试土壤,测定其可溶铁(Fes)、游离铁(Fed)、活性铁(Feo)、络合铁(Fep)含量,探讨了PP与LMWOA对紫色土铁形态分布的影响。结果表明:PP与LMWOA各自单独作用均能使酸性紫色土Fes增加、中性紫色土Fes减少;对于石灰性紫色土,PP会促进其Fes增加,而LMWOA作用相反。EGCG与LMWOA联合作用,在酸性和石灰性紫色土上均表现为LMWOA通过促使本应转化为Fes的转化为Fep而掩蔽EGCG对铁的溶解作用;芦丁与LMWOA联合作用,在酸性紫色土铁的溶解上表现为协同效应,在石灰性紫色土上则表现为LMWOA会抑制芦丁对铁的溶解作用;对于中性紫色土,PP与LMWOA联合作用可促进Fed向Fes转化而削弱PP对铁溶解的抑制作用。

Effects of Plant Polyphenols and Low Molecular Weight Organic Acids on Iron Speciation in Purplish Soil

Plant polyphenol (PP) and low molecular weight organic acid (LMWOA) have important effects on the transformation of iron fraction in soil. In this study, acidic, neutral, and calcareous purplish soils were used as research objects. Incomplete randomized block experiments were performed using two kinds of PPs (ie, epigallocatechin gallate (EGCG) and rutin) and two LMWOAs (ie, Citric acid and oxalic acid). After the solution was leached, soluble iron (Fes), free Fe oxides (Fed), amorphous Fe oxides (Feo), and organic-bound Fe (Fep) were measured to investigate the effect of PPs and LMWOAs on the iron transformation of purplish soil. The results showed that both PP and LMWOA could increase the iron Fes content of acid purplish soil, making Fes of neutral purplish soil decrease. For calcareous purplish soil, PP promoted the increase of Fes, and LMWOA decreased the Fes content. When EGCG and LMWOAs were combined, acidic and calcareous purplish soils all show that LMWOAs will weaken the EGCG"s promoting effect on soil Fes by promoting the partial iron that should be transformed into Fes to be transformed into Fep. When rutin is used in combination with LMWOAs, The synergistic effect was observed in acid purplish soil. LMWOAs in calcareous purplish soil would inhibit the promotion of rutin on soil Fes. In neutral purplish soil, the combined action of PPs and LMWOAs can reduce the inhibition of soil Fes when it acts alone by promoting the conversion of soil Fed to Fes.