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| Kinetics of Fluoride Release from a Tea Garden Soil Under Different Concentrations of Citric Acid |
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| KeyWord:citric acid; tea garden soil; fluorine fractions; kinetics |
| Author Name | Affiliation | | YING Hao | School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China | | ZHANG Xian-chen | Key laboratory of Tea Biochemical and Biological Technology, Ministry of Education, Anhui Agricultural University, Hefei 230036, China | | GAO Hong-jian | School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China
Key laboratory of Tea Biochemical and Biological Technology, Ministry of Education, Anhui Agricultural University, Hefei 230036, China | | WAN Xiao-chun | Key laboratory of Tea Biochemical and Biological Technology, Ministry of Education, Anhui Agricultural University, Hefei 230036, China |
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| Abstract: |
| Citric acid is one of organic acids excreted by tea plants. Here, the effects of citric acid on F forms and partition between solid and solution phases in a tea garden soil were investigated using a kinetic method. Soil solution pH and electric conductivity decreased with increasing reaction time. Release of F from the soil was quick at the beginning and then slowed down. Concentrations of F in soil solution were higher from 0 to 6 h than from 6 h to 10 h. Kinetic process of F release from tea garden soil fitted the first-order reaction kinetics and Elovich, diffusion and double constant equations as well, with all the coefficients of determination（R2） greater than 0.91. Amount of free F and total F in soil solution increased with increasing concentrations of citric acid. Amount of Al-F complexes released during the first two hours were greater under high than under low concentrations of citric acid. During the first 1 hour, AlF3 was the main form of Al-F complexes, accounting for 90% of the total F released from the tea garden soil. With increasing reaction time, however, amount of AlF+2 released from the tea garden soil increased and finally surpassed AlF3. High concentrations of citric acid promoted F release from the soil and facilitated the conversion of Al-F complexes into AlF2+ and AlF+2. These results provide insights into the chemistry of high F accumulation in tea tree plants from soils. |
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