【摘要】 采用重力沉降法,根据司笃克斯(Stokes,1945)定律结合分速离心法提取两种粒径等级的自然土壤胶体样品。利用美国EPA批处理实验方法,进行一系列实验室静态吸附、解吸实验,并获取相应的动力学解离/沉积曲线以及热力学等温平衡解吸/吸附曲线。通过对土壤胶体释放/沉积速率、解离效率和解吸因数等行为因子的定量解析,描述自然土壤胶体的释放、稳定、沉积/分配动力学和热力学行为,考察土壤水溶液pH/离子强度、胶体粒径因素对土壤胶体释放、分配沉积行为的影响。实验结果表明,环境溶液pH的增大及离子强度的减小对土壤胶体的稳定和释放起促进作用,但对胶体向土壤颗粒中的沉积过程是不利的。pH和离子强度条件能够改变土壤胶体表面带电荷状态,改变土壤胶体与土壤介质表面吸附排斥作用力的大小,提高或降低土壤胶体与介质表面的碰撞接触效率,从而表现出土壤胶体在土壤介质中的沉积分配行为上的变化。粒径大小对土壤胶体的释放沉积行为影响明显。大粒径土壤胶体颗粒较小粒径颗粒更容易向土壤介质表面分配沉积。由此可知,土壤介质对土壤胶体持有和吸附的能力是与胶体颗粒粒径大小密切相关的,这主要是因为颗粒粒径大小能够有效的影响胶体颗粒与介质表面间的反应能量。土壤胶体沉积分配动力学曲线揭示,土壤胶体向土壤介质的分配过程是一个动态变化过程,土壤介质对土壤胶体的持留吸纳能力随时间而逐渐减弱。分配系数被证实是表征和分析土壤胶体沉积分配过程受环境物理化学因素影响的有效过程因子。更多还原

【Abstract】 Natural soil colloids of two sizes were chosen as the model colloid to study the effects of ionic strength and pH on the release and deposition behaviors of the natural colloids in the subsurface.The classic gravity sedimentation method coupled with a centrifuge method was employed for the colloid retraction and the particle size classifications.The batch experiments were conducted as a function of ionic strength,pH and particle sizes,and a series of colloidal release/deposition dynamic and thermodynamic curves were obtained.The indicators of colloidal environmental behaviors were further calculated and analyzed,including the release/deposition rate coefficients,the release efficiencies and the partition constants.The great effects of soil solution chemistry on soil colloid generation and deposition were detected.The release capacity and the stability of soil colloids were substantially enhanced with the increase of pH and the decrease of ionic strength,and a prohibited deposition behavior was observed at the same conditions.These can be explained employing the electrical double layer theory that the diffusion layer thickness and the surface charge state generally govern the release,stability and deposition behaviors of the colloidal particles.pH and ionic strength are able to change the surface charge of soil colloids,hence cause the change of attachment efficiencies and represented a remarkable impact on colloid release/deposition behaviors.Besides the pH and ionic strength,the particle size was also found to have a significant effect on the soil colloid deposition kinetics.Large colloidal particles(5 μm) had a much more preferential access to the adsorption points of soil matrix surface compared with the smaller ones(2 μm).In the particle-collector interaction energy theory,particles of smaller size generally have the larger attachment energy barriers which result in greater retard for them to get attached to the soil surfaces.Moreover,a decreasing by time adsorption capability of soil grains and a kinetic(time)-dependent deposition/partition of soil colloids were obtained in the deposition kinetic profiles.The partition coefficients calculated from the kinetic profiles were confirmed to be able to well describe and evaluate the soil colloids deposition behaviors,which is consistent with the results in the previous reported studies.更多还原