4.7 Article

Experimental investigations on scale-dependent dispersivity in three-dimensional heterogeneous porous media

Journal

ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Volume 28, Issue 18, Pages 23336-23348

Publisher

SPRINGER HEIDELBERG
DOI: 10.1007/s11356-020-12316-4

Keywords

Laboratory experiments; Heterogeneity; Dispersivity; Scale effects; Porous media; Sand tank

Funding

  1. National Key Research and Development Program of China [2018YFC1800900]
  2. Program for Jilin University (JLU) Science and Technology Innovative Research Team [2019TD-35]
  3. National Natural Science Foundation of China [41772253, 41972249, 51774136]
  4. Natural Science Foundation of Hebei Province of China [D2017508099]
  5. Program of Education Department of Hebei Province [QN219320]
  6. Engineering Research Center of Geothermal Resources Development Technology and Equipment, Ministry of Education, China

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The relationship between scale-dependent dispersivity and heterogeneous sedimentary structures was investigated through tracer experiments in a three-dimensional sand tank. Results showed differences in scale dependence and behavior of dispersivities in individual facies columns and heterogeneous porous media, indicating varying patterns with increasing transport distances.
The relationship between the scale-dependent dispersivity and heterogeneous sedimentary structures is investigated through conducting non-reactive tracer experiments in a three-dimensional heterogeneous sand tank. The heterogeneous porous media consists of three sedimentary facies of silty, fine, and medium sands collected from the west of the Songnen Plain, China. Moreover, several corresponding individual facies soil columns were constructed for comparison. A conservative tracer was continuously injected from an upstream source. The effective parameters were estimated by inverse modeling of a one-dimensional transport model. The results show that the scale dependence of the estimated dispersivities was discovered in the individual facies column (with relatively weaker effect) and the heterogeneous porous media (with more significant effect). With increasing transport distances, the dispersivities of the individual facies tend to reach an asymptotic value, while those of the heterogeneous media increase continuously. Furthermore, the results show that a power function can describe the relationship between effective dispersivities and transport distances. The exponent of the function is greater than one for the heterogeneous media, but less than one for the individual facies. The results also indicate that the dispersion plume is macroscopically dominated by the distribution of facies. The heterogeneity of hydraulic conductivity causes the variations of flow velocity, which further enhances the scale dependence of dispersivities. The tracer experiment in heterogeneous media provides the fundamental insight into the understanding of contaminant transport processes.

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