Solute transport and retention in fractured rock

Antti Poteri

    Research output: Book/ReportReport

    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

    SeriesVTT Tiedotteita - Meddelanden - Research Notes
    Number2464
    ISSN1235-0605

    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/ReportReport

    TY - BOOK

    T1 - Solute transport and retention in fractured rock

    AU - Poteri, Antti

    PY - 2009

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    N2 - 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.

    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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    KW - retention

    KW - flow path

    KW - bedrock

    KW - fractured rock

    KW - rock matrix

    KW - porosity

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    KW - modelling

    KW - matrix diffusion

    M3 - Report

    SN - 978-951-38-7263-2

    T3 - VTT Tiedotteita - Meddelanden - Research Notes

    BT - Solute transport and retention in fractured rock

    PB - VTT Technical Research Centre of Finland

    CY - Espoo

    ER -

    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).