对几种典型土壤中粘粒级有机-矿质复合体的初步表征

Preliminary Characterization of Clay Organo-Mineral Aggregates Isolated from Different Typical Soils

采用超声分散法提取了江西红壤、黑龙江黑土和北京潮土等3种典型土壤的粘粒级有机-矿质复合体,分别用傅立叶转换红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜-X射线能谱(SEM-EDS)以及固态核磁共振(NMR)等方法对提取的有机-矿质复合体进行了表征。结果表明,黑土复合体具有最高的有机质含量和最大的阳离子交换容量。3种复合体的主要矿物成分均为石英,但红壤复合体还含有云母与闪石等成分,而黑土和潮土复合体主要还包括长石和方解石成分。对NMR不同化学位移域的谱峰积分得到3种粘粒级复合体有机碳的组成比例,红壤复合体中脂类C的含量最高,黑土复合体中烷氧基C的含量最高,而潮土中烷氧基C、脂类C以及芳香族C的含量相差不多。

Clay organo-mineral aggregates were isolated from different soils in China including red soil, black soil and fluvo-aquic soil by ultrasonic dispersion in water followed by sedimentation. The physico-chemical properties of organo-mineral aggregates were determined and the clay fractions were characterized jointly with Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and nuclear magnetic resonance （NMR） spectrometry. It was found that clay fraction of black soil had the highest soil organic matter content and greatest cation exchange capacity. XRD patterns showed that quartz was the dominant mineral in all kinds of clays. Clay of red soil also consisted of mica, amphibole and trace amount of chlorite, while the mineral assemblage of black soil consisted of feldspar, calcite and trace amount of mica and chlorite. The mineral in clay of fluvo-aquic soil was mica, feldspar, calcite and dolomite. From FTIR spectra, the result can be reached that mineral components from red soil are mainly kaolinites while those from black soil and fluvoaquic soil are mainly montmorillonites. The results of FTIR spectra were coincident with those of XRD. The SEM images indicated that all clays were sheet-like, amorphous aggregates. The surface of fluvo-aquic soil was roughest, while clay of red soil showed relatively clean surface than others. Results of SEM-EDS revealed that silicon was the dominant constituent element, which was consistent with above results. The information from NMR indicated that the content of aliphatic C of red soil was highest, while the content of o-alkyl C was the most in clay of black soil, furthermore, the content of aliphatic, o-alkyl and aromatic C levels were similar in clay of fluvo-aquic soil.