Effect of EGCG on Al, Fe and Mnin Yellow Soil Relative to Concentration and pH
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Supported by the National Natural Science Foundation of China(No.41371230)

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    Abstract:

    【Objective】Plant polyphenols may alter forms of the elements existing in soil through complexation.The study is oriented to explore effects of epigallocatechin gallate (EGCG) relative to concentration and pH and the interactions between its concentration and pH on soluble, free, amorphous and complex forms of Al, Fe and Mnin Yellow soil.【Method】A two-factor experiment laid out at random was carried out by extraction of the tested soils, of which each had 3 replicates. Firstly,soilwas collected from the 30~50 cm soil layer (surface)in a Yellow soilfield as a sample for test, air-driedand ground to pass through a 10-mesh nylon sieve.Then a total of 48 portions, 10 g each, were weighed out of the prepared soil sample and placed into 250 ml polyethylene bottles, respectively. Into the bottles, prepared EGCG solution was added, 100 mL each. Then the bottles were placed into a constant temperature oscillater for 24 h oscillationunder room temperature (25°C). At the end of the oscillation, the suspensions were filtered for extracts, which were then analyzed for soluble Al, Fe and Mn (Als, Fesand Mns). The second step was to have the remainders from filtration dried up in an oven at 60°Cfor 48 h and reground with an agate mortar to pass through a 60-mesh nylon sieve for determination of oxidized forms of Al, Fe and Mn.Free Al, Fe and Mn(Ald, Fedand Mnd), amorphous Al, Fe and Mn (Alo, Feo and Mno), complex Al, Fe and Mn (Alp, Fep and Mnp) were extracted by the dithionite-citrate-bicarbonate (DCB) method, acid ammonium oxalate (AAO) at pH=3 in the dark and Na-pyrophosphate(Na4P2O7) at pH=10, respectively. Contents of all the above-mentioned fractions of Al, Fe and Mn were determined with ICP-AES. 【Result】Concentration of the EGCG solution was found to have a very significant effect on the content of Als, Fes, Mns, Alp, Fep, Mnp, Alo or Feo in Yellow soil; and pH of the solution had a significant or extremely significant effect on the content of Als, Fes, Mns, Alo, Feoor Mno in Yellow soil, while the interaction between the two did on the content of Als, Fes, Mns, Alo, Alp or Mnd in Yellow soil. The addition of EGCG affected the elements both in content and in form, but their relative contents did not change much. In terms of content, the soluble forms displayed an order of Al>Fe>Mn, the freeforms, did an order of Fe>Al>Mn, and the amorphous and the complex forms both followed an order of Al>Fe>Mn. However, concentration of EGCG was not a factor affecting the content of Ald, Fed and Mnd, and neither was pH of EGCG affecting the content of Fed, Mnd, Alp, Fepand Mnp, while the interaction between the two did not have much effect on the content of Ald, Mnd, Feo, Mno, Fep and Mnd in Yellow soil. Correlations analyses show that Alo, Feo and Mno was closely related to Als Fes and Mns, respectively, which suggests that EGCG solution affects mobilization of the elements by changing their oxide forms, especially the amorphous ones and hence contents of the soluble ones . The more Alo in the soil, the more Als in soil solution, and all the same with Fe and Mn. On the other hand, pH of the EGCG solution was significantly and negatively related to Alsand Mns,which suggests thatreactivation of Al and Mn may lower pH of the extractant, posing a potentialrisk.【Conclusion】The study has further verified that the effect of EGCG solution on Al, Fe and Mn mobilization varies with its concentration and pH of the solution and interaction between the two. All the findings in this study may help orient the study on causes of soil acidification in tea gardens and serve as reference for prevention of plant Al/Mntoxication. It is, therefore, worthwhile to note when plant polyphenols are used to prevent Al/Mn toxicity, adequate attention should be given to control of soil acidification.

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ZHANG Junsi, YUAN Dagang, FU Hongyang, WENG Qian, WANG Changquan. Effect of EGCG on Al, Fe and Mnin Yellow Soil Relative to Concentration and pH[J]. Acta Pedologica Sinica,2017,54(4):905-916.

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History
  • Received:July 09,2016
  • Revised:January 15,2017
  • Adopted:February 16,2017
  • Online: April 28,2017
  • Published: