Solute transport and retention in fractured rock

Antti Poteri

Research output: Book/ReportReportProfessional

Abstract

This work reviews and compiles the analysis of tracer tests that were performed in the Äspö Hard Rock Laboratory in Sweden over a period of several years. The tracer tests were carried out in fractured rock at a depth of about 400 metres below the ground surface. The experimental programme progressed from a simple flow path in a single fracture to multiple flow paths through a network of fractures. The modelling of the tracer tests on different scales shows that matrix diffusion is an important retention process of solute transport in fractured rock. The tracer breakthrough curves show indications of the diffusive mass exchange between mobile and immobile zones, although in many cases in situ tracer tests should be performed under boundary conditions that favour advective solute transport. The analysis of the flow paths in a single fracture and in a network of fractures indicates that an increase in the complexity of the flow field and extending flow paths over several fractures does not introduce new retention processes. The same retention processes that are applicable for a single fracture can be applied over longer pathways that are composed of several different fractures. Modelling the tracer tests on a block scale indicates that this is the case even when the hydraulic structures along the flow path are geologically of different origin. Ultimately, the retention properties are governed by the average properties along the flow path. The main outcome of the study is that the assessment of in situ solute retention properties requires adequate information on the immobile zones and flow paths. The heterogeneity of the immobile zone retention properties affects the effective tracer retention properties. The retention properties estimated for a given tracer test set-up cannot be directly transferred to another flow field without considering how the changes in the flow field will affect the contributions of the different immobile zones to the overall retention.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages148
ISBN (Electronic)978-951-38-7262-5
ISBN (Print)978-951-38-7263-2
Publication statusPublished - 2009
MoE publication typeNot Eligible

Publication series

NameVTT Tiedotteita - Research Notes
PublisherVTT
No.2464
ISSN (Print)1455-0865
ISSN (Electronic)1235-0605

Fingerprint

solute transport
tracer
rock
flow field
hydraulic structure
breakthrough curve
hard rock
modeling
test
solute
boundary condition
matrix

Keywords

  • solutes
  • transport
  • retention
  • flow path
  • bedrock
  • fractured rock
  • rock matrix
  • porosity
  • tracer tests
  • modelling
  • matrix diffusion

Cite this

Poteri, A. (2009). Solute transport and retention in fractured rock. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 2464
Poteri, Antti. / Solute transport and retention in fractured rock. Espoo : VTT Technical Research Centre of Finland, 2009. 148 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2464).
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Poteri, A 2009, Solute transport and retention in fractured rock. VTT Tiedotteita - Meddelanden - Research Notes, no. 2464, VTT Technical Research Centre of Finland, Espoo.

Solute transport and retention in fractured rock. / Poteri, Antti.

Espoo : VTT Technical Research Centre of Finland, 2009. 148 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2464).

Research output: Book/ReportReportProfessional

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AB - This work reviews and compiles the analysis of tracer tests that were performed in the Äspö Hard Rock Laboratory in Sweden over a period of several years. The tracer tests were carried out in fractured rock at a depth of about 400 metres below the ground surface. The experimental programme progressed from a simple flow path in a single fracture to multiple flow paths through a network of fractures. The modelling of the tracer tests on different scales shows that matrix diffusion is an important retention process of solute transport in fractured rock. The tracer breakthrough curves show indications of the diffusive mass exchange between mobile and immobile zones, although in many cases in situ tracer tests should be performed under boundary conditions that favour advective solute transport. The analysis of the flow paths in a single fracture and in a network of fractures indicates that an increase in the complexity of the flow field and extending flow paths over several fractures does not introduce new retention processes. The same retention processes that are applicable for a single fracture can be applied over longer pathways that are composed of several different fractures. Modelling the tracer tests on a block scale indicates that this is the case even when the hydraulic structures along the flow path are geologically of different origin. Ultimately, the retention properties are governed by the average properties along the flow path. The main outcome of the study is that the assessment of in situ solute retention properties requires adequate information on the immobile zones and flow paths. The heterogeneity of the immobile zone retention properties affects the effective tracer retention properties. The retention properties estimated for a given tracer test set-up cannot be directly transferred to another flow field without considering how the changes in the flow field will affect the contributions of the different immobile zones to the overall retention.

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Poteri A. Solute transport and retention in fractured rock. Espoo: VTT Technical Research Centre of Finland, 2009. 148 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2464).