solinst ltdo levelogger dissolved oxygen do dissolved oxygen levelogger optical fluorescence optical flourescence dissolved oxygen measurements dissolved oxygen datalogging image
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solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image

Assessing the transport and fate of MTBE
amended petroleum hydrocarbons in the UK Chalk aquifer

G P Wealthall, S F Thornton and D N Lerner
Groundwater Protection and Restoration Group, University of Sheffield, UK
www.sheffield.ac.uk/gprg

 solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image
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solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image
solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image

| 1. Intoduction | 2. Site Characteristics | 3. The Chalk Aquifer | 4. Fracture Network Characteristics |
| 5. Hydrogeology | Source Term | 6. Dissolved Phase Plume | 7. Conclusions | Full Paper |
solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image

The Chalk aquifer can be conceptualised as a dual-porosity system, with flow and transport occurring primarily in a pervasive high-transmissivity fracture network, and the bulk of groundwater being stored in the low-transmissivity porous matrix:
  • The aquifer consists of 99% calcium carbonate (CaCO3), with occasional marl and flint layers, but very low mineral oxide (MnO2, Fe(OH)3) content
  • The aquifer matrix has high porosity (ca. 30-45%) but low effective permeability, and the matrix pore water is essentially immobile
  • The matrix is dissected by sets of fractures, which contribute only 1% of the aquifer porosity, but which have very high permeability and dominate groundwater flow
  • The primary dilution mechanism is diffusion into the matrix. Reversible contaminant diffusion profiles result from the exchange of contaminants between the fractures and the matrix
  • Degradation of pollutants in the matrix, is at present, poorly understood.

solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image
solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image
solinst the chalk aquifer chalk aquifer dual porosity systems high transmissivity fracture networks low transmissivity porous matrix aquifer matrix reversible contaminant diffusion image
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