Effects Of EGCG On Mobilization And Migration Of Al, Fe And Mn In Soil

Polyphenols existed in soil will affect the soil chemical behavior of Al,Fe,Mn.In order to study the influence of tea polyphenols on soil mineral elements,we carried out the extraction experiment and intermittent leaching experiment.Extraction experiments were performed to study the effect of tannic acid,EGCG and citric acid in concentration or pH on the activation of Al,Fe and Mn in Yellow Earth.The effect of relative to concentration and pHof EGCG onthe migrationof Al,Fe and Mnwas stuied.Results showed that(a)the mobilized contents of soluble and exchangeable Al,Fe and Mn in Yellow Earth increased with increasing of tannic acid,EGCG and citric acidconcentration.When tannic acid concentration was<1.00 mmol/L,and EGCG concentration was in 0.00-5.00 mmol/L,and tannic acid concentration was<0.75 mmol/L,the soluble/exchangeable ofAl,Fe andMn in Yellow Earth was<1,which meant thatAl,Fe and Mndistributed on soil exchange points at this circumstance;(b)the contents of soluble Al,Fe and exchangeable Mn increased with increasing tannic acid pH,especially when pH>4,soluble Al and Fe were sensitive to the situation.The contents of soluble and exchangeable Fe decreased with increasing in EGCG and citric acid pH.At,the soluble/exchangeable ofAl and Fe<1 at pH<5.0 and 4.0,respectively,which meant that Al and Femainly distributed onsoil exchange points under these circumstances;the soluble/exchangeable ofMnwas<1 when pH was in 3.0-6.0,which meant that Mn mainly distributed on soil exchange points;(c)the mobilization ability of citric acid to soluble Al was stronger than that of polyphenols,and polyphenols had a greater effect to soluble and exchangeable Mn than citric acid under the influence of concentration or pH.It was suggested that the reductive dissolution of the polyphenol with Mn had a special significance for the Mn activation.The effects of polyphenols and citric acid on soluble or exchangeable Al,Fe and Mn were in the order Al>Fe>Mn;(d)concentration,pH and relative to concentration and pH of EGCG had a significant effect on Al_s,Fe_s,Mn_s and Al_o in Yellow Earth.EGCG,whose concentration was 5.00 mmol/L and pH was 3.5,would help the increase of the amount of Al_s and Mn_s.The change of the amorphous oxide content affected by EGCG had an influence on the soluble state,affecting the elements activation.However,it was possible to cause soil acidification when the activated amount of Al and Mn increased to a certain extent.Contents of Al,Fe and Mn oxides in soils leached by EGCG were studied at different concentration or relative to concentration and pH via an intermittent leaching way.Results showed that(a)EGCG had a greater effect on Al in Yellow Earth than that in Purplish Soil,and the mobilized amount of Fe and Mn in Purplish Soil was greater than that in Yellow Earth.Aloand Alp were the main way of Al migration in Yellow Earth,and FeO had an important effect on Fe migration in Purplish Soil.As to Mn migration in Purplish Soil,Mndwas the main way.The content of elements in Yellow Earth affected by EGCG was in the order of Al>Fe>Mn,which was in the order of Fe>Mn>Al in Purplish Soil.It was suggested that EGCG plays an important role in the migration of Fe and Mn in Purplish Soil;(b)under the action of EGCG,as A1B1(0.00 mmol/L+pH3.5),A2B2(0.25 mmol/L+pH4.5)and A3B2(1.00 mmol/L+pH4.5),the migration amount of elements was in the order of Al>Mn>Fe,and Al>Fe>Mn was the order at other treatments.EGCG relative to concentration and pH had a different effect on the migration of Al,Fe and Mn.However,the migration amount of Al and Fe in Yellow Earth was 180.24 mg/L and 41.15 mg/L,respectively,which was highest in all treatments.That is to say,EGCG relative to high-concentration and high-pH help the migration of Al and Fe in Yellow Earth.The migration amount of Mn in Yellow Earth was 4.50 mg/L with the help of EGCG relative to high-concentration and low-pH,which meant that the migration of Mn in perennial tea garden soil might be stronger;(c)complexation to A1 with EGCG relative to median-concentration and high-pH or high-concentration and high-pH was stronger than the proton-effect.The migration of Al was mainly affected by the proton-effect under the influence of EGCG relative to low-concentration and pH,at which the proton-effect was stronger than complexation all the time.The migration of Fe is the synthetical result of the proton-effect and reduction,and so on,at low concentration.In summary,EGCG relative to high-concentration and low-pH raise the mobilization and migration of Mn,and the amorphous oxide content of Al,Fe and Mn had an important impact on the mobilization and migration of them under the leaching.