水田土壤富里酸组分的结构表征及对多环芳烃芘的吸附特征

本文依次用pH4．8、pH7．0及pH11．0的通用缓冲液、水和乙醇，梯度淋洗吸附富里酸的XAD-8树脂，根据其不同解离程度及亲水性质将富里酸细分为5个组分（包括3个亲水性组分和2个疏水性组分）；利用元素分析、红外光谱和核磁共振等分析方法确定各组分的理化特征，并研究各组分对特定多环芳烃（芘）的吸附特性。结果表明，按照淋洗次序，后分离的组分其羧基碳含量低于先分离的组分，烷基碳含量则高于后者；芘在被水和乙醇淋洗出的两种组分上的吸附等温线体现出良好的线性；组分中的烷基组分对吸附有促进作用，相反，羧基和羰基不利于芘的吸附，表明梯度淋洗分组方法对研究芘与富里酸的作用机理是十分有效的。

Structural Characterization and Pyrene Binding Properties of the Fulvic Acid Fractions by pH Gradients from Paddy Soils

Five fulvic acid（FA ）fractions from two paddy soils（side-bleached paddy soil, SBP and waterlogged paddy soil, WP）were first obtained through elution of FA from XAD-8 resin with sequential eluents （pH 4.8, pH 7.0, and pH 11.0 buffering solutions, water, and ethanol ）, and were characterized by elemental analysis, Fourier-transform infrared（FT-IR）spectroscopy and cross-polarization magic-angle spinning ）3C nuclear magnetic resonance（CP-MAS 13C-NMR ）spectroscopy. The results were consistent among the methods used, suggesting that the later eluted fractions （eluted with water or ethanol）in the sequential elution contained lower carboxyl C, and higher alkyl C than the earlier ones. Through the batch experiment of pyrene sorption to FA fractions, linear isotherms were observed from the fractions eluted with water and ethanol （FAwater, FAethanol）, whereas non-linear isotherms were shown on the fractions eluted with pH4.8 and pH7.0 buffering solutions （FApH4.8, FApH7.0）. Besides, the C-normalized distribution coefficients （Koc）had the positive correlation with the contents of alkyl C, but the negative correlation with the contents of carboxyl and carbonyl C. At last, we founded that the FAweter and FAehtanol had the maximum adsorption of pyrene. These results proved that carboxyl and carbonyl C of FA reduced the binding of pyrene and possibly other PAHs, whereas the aliphatic moieties of soil FA enhanced the binding. We concluded that the fractionation of soil FA was a useful way in understanding the mechanisms of the sorption of pyrene to mobile soil FA.