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| Cu2+ adsorption of tea plantation soil micro-aggregates with low molecular weight organic acids |
| Received:August 30, 2016 |
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| KeyWord:low molecular weight organic acids;soil aggregates;Cu2+;adsorption |
| Author Name | Affiliation | E-mail | | LI Xin-yu | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | XIA Jian-guo | College of Resources, Sichuan Agricultural University, Chengdu 611130, China | xiajianguo@126.com | | LI Lin-jia | College of Resources, Sichuan Agricultural University, Chengdu 611130, China | | | SONG Cheng-yuan | College of Resources, Sichuan Agricultural University, Chengdu 611130, China | |
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| Abstract: |
| The effect of different low molecular weight organic acids(citric, malic, and oxalic acid) on copper(Cu2+) adsorption in soil aggregates from a tea plantation in Mengshan was determined. Results indicate that the Cu2+ adsorption capacity of regular and of different-sized fractions of soil aggregates increased as Cu2+ concentration increased. However, this effect was limited and eventually decreased as the amount of low molecular weight organic acids added went beyond a maximum effective amount. Factors such as surface area, ferric oxide availability, cation exchange capacity, and presence of organic matter influence Cu2+ adsorption. Cu2+ adsorption is also affected by soil aggregate size wherein adsorption diminished as soil aggregate size increased:(<0.002 mm) > 0.053~0.002 mm > original soil > 2~0.25 mm > 0.25~0.053 mm. The isothermal adsorption process was fitted to three equations, namely, Langmuir, Freundlich, and Temkin. The equations were used to fit, resulting in a significant level(P<0.05), with the Langmuir equation showing the best fit. Low molecular weight organic acids not only have a promoting effect but also an inhibitory effect on Cu2+ soil adsorption. Cu2+ adsorption is promoted at a concentration of 0~1 mmol·L-1 for citric acid and malic acid and 0~0.1 mmol·L-1 for oxalic acid. However, at a concentration of > 1 mmol·L-1 for citric acid and malic acid and > 0.1 mmol·L-1 for oxalic acid, Cu2+ adsorption is inhibited. Adsorption capacity reached maximum when the concentration of citric acid and malic acid was 0.5 mmol·L-1. Different organic acids with different concentrations, as well as soil aggregate size, affect the Cu2+ adsorption of soil aggregates. |
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