Department of Civil Engineering, University of Toronto, Toronto, Ontario, Canada.
Environ Sci Technol. 2012 Sep 18;46(18):9987-94. doi: 10.1021/es301721f. Epub 2012 Aug 28.
The effects of fracture characteristics, specific discharge, and ionic strength on microsphere transport in variable-aperture dolomite rock fractures were studied in a laboratory-scale system. Fractures with different aperture distributions and mineral compositions were artificially created in two dolomite rock blocks. Transport tests were conducted with bromide and carboxylate-modified latex microspheres (20, 200, and 500 nm diameter). Under overall unfavorable attachment conditions, there was significant retention of the 20 nm microsphere and minimal retention of the 500 nm microsphere for all conditions examined. Aperture variability produced significant spatial variation in colloid transport. Flushing with low ionic strength solution (1 mM) following microsphere transport at 12 mM ionic strength solution produced a spike in effluent microsphere concentrations, consistent with retention of colloids in secondary energy minima. Surface roughness and charge heterogeneity effects may have also contributed to the effect of microsphere size on retention. Matrix diffusion influenced bromide transport but was not a dominant factor in transport for any microsphere size. Calibrated one-dimensional, two-site kinetic model parameters for colloid transport in fractured dolomite were sensitive to the physical and chemical properties of both the fractured dolomite and the colloids, indicating the need for mechanistic modeling for accurate prediction.
在实验室规模的系统中研究了裂缝特征、比流量和离子强度对变孔径白云岩岩缝中微球运移的影响。在两块白云岩岩块中人工制造了具有不同孔径分布和矿物成分的裂缝。用溴化物和羧酸改性的乳胶微球（20、200 和 500nm 直径）进行了运移试验。在总体不利附着条件下，对于所有检查的条件，20nm 微球有明显的滞留，而 500nm 微球的滞留最小。孔径变化导致胶体运移存在显著的空间变化。在用 12mM 离子强度溶液进行微球运移后，用低离子强度溶液（1mM）冲洗会导致出水中微球浓度的峰值，这与胶体在二次能量最小值中的滞留一致。表面粗糙度和电荷非均质性效应也可能导致微球尺寸对保留的影响。基质扩散影响溴化物的运移，但对任何微球尺寸的运移都不是主要因素。白云岩裂缝中胶体运移的校准一维双位动力学模型参数对裂缝白云岩和胶体的物理化学性质均敏感，表明需要进行机械模型化以进行准确预测。
