Diffusion in Relatively Homogeneous Sand Columns: A Scale-Dependent or Scale-Independent Process?

Entropy

Yong Zhang¹  Hongxia Xu²  Xueyan Lv² 

[1] Division of Hydrologic Sciences, Desert Research Institute, Las Vegas, NV 89119, USA;State Key Laboratory of Pollution Control and Resource Reuse, Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; E-Mails:

关键词: fractional dynamics;    fractional-derivative models;    scale;    homogeneous;   

DOI  :  10.3390/e15104376

来源: mdpi

【 摘 要 】

Solute transport through homogeneous media has long been assumed to be scale-independent and can be quantified by the second-order advection-dispersion equation (ADE). This study, however, observed the opposite in the laboratory, where transport of CuSO breakthrough curves. Results show that the tempering parameter in the TS-FADE model generally decreases with an increase of the column length (probably due to the higher probability of long retention processes), while the time index (which is a non-local parameter) remains stable for the uniformly packed columns. Transport in sand columns filled with relatively homogeneous silica sand, therefore, is scale-dependent, and the resultant transient sub-diffusion can be quantified by the TS-FADE model.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.