原子力显微镜表征土壤中的纳米胶体

以平均粒径和多分散性指数为参数、采用原子力显微镜(AFM)表征了不同地区三种土壤纳米胶体的粒径与形貌,研究了pH及重金属离子对纳米胶体粒径和形貌的影响。结果表明,江苏九华(JH-4)土壤纳米胶体主要为形状规则的黏土矿物粒子,并部分被有机质包裹或覆盖,平均粒径为21.5nm(n=98),多分散性程度高(PI=1.9);浙江富阳(FY-1)土壤纳米胶体主要是无规则形状的有机质包裹的粒子,平均粒径为20.3nm(n=133),多分散性程度高(PI=2.0);江西德兴(DX-9)土壤纳米胶体主要是球状或近球状的无机粒子,平均粒径为56.3nm(n=147),多分散性程度较低(PI=1.3)。pH及重金属铜离子的存在对纳米胶体粒径和形貌会产生或分散或团聚的影响,这种影响可能与土壤纳米胶体的电荷性质、有机质含量等因素有关,形貌变化较为复杂。这种复杂性对理解和研究胶体在环境过程中的行为具有指导意义。

Characterization of soil nano-colloidal particles by atomic force microscopy

Nanocolloids in three Chinese soils were studied with the aid of atomic force microscopy (AFM), and their mean diameter and polydispersity index (PI) were used as parameter to characterize their particle size and morphology. Nanocolloids of JH-4 soil (from Jiuhua, Jiangsu Province) are mainly composed of clay mineral particles of regular sharp, with a mean diameter of 21.5 nm (n=98) and PI of 1.9. The particles are partially coated with colloidal organic matter. Similarly, nanocolloids of FY-1 soil (from Fuyang, Zhejiang Province) have a mean diameter of 20.3 nm (n=133) and a PI of 2.0 though they are irregular in shape and almost completely coated with colloidal organic matter. In contrast, nanocolloids of DX-9 soil (from Dexin, Jiangxi Province) are much larger in mean diameter being 56.3 nm (n=147), but lower in PI being 1.3, spherical and rod in shape, and less coated by colloidal organic matter. Nanocolloidal morphology varies significantly with pH: declining pH coagulates nanocolloids whereas rising pH disperses them. Adding Cu²⁺ to the nanocolloids also coagulates them. These morphological changes may be related to such properties of the nanocolloids as electrical charge and organic matter content. Knowledge on size and shape of nanocolloids and effects of pH and heavy metal ions on them may help understand the roles of nanocolloids in facilitating movement and transport of metal contaminants in soil and water environment.