Review Version 9 CT Enhancements • Species element: • Can accept either decay rates or half-lives • Can be exported to, or imported from, Excel • Source element: • Acts as a Container • “Associated Cells” are now automatic • New Advective Transfer options:
Discuss User Issues • How can I apply a boundary condition to a pathway element? • How can I use the Source element to represent a complex engineered barrier system?
Pipe or Cell? • Generally, use Pipe elements only for steady-state flow systems!
Pipe Pathway Strengths & Limitations • Strengths • Exact solution to very complex physical system • Limitations • Cannot apply solubility limits within pathway. • Species are discharged from a pathway based on the properties of the pathway at the time the species (or their parents) entered it. • “Looping” reaction chains are not permitted • e.g., A B and B A
Cell Pathway Strengths & Limitations • Strengths • Flexibility • Stability & accuracy • Limitations • Tedious to construct networks • Numerical dispersion • α ~ L/2N
What are Partition Coefficients? • Defined as the ratio of the species’ concentration in medium X to its concentration in the reference fluid. • Useful concepts: • A sorbing solid with mass M is equivalent to a volume of water = M Kd • The retardation factor for a system, even a complex system: • Total Equivalent Volume / Flowing Volume
Fluids, Reference Fluids, Cloned Fluids • Fluids normally have specified partition factors. This gives them an implied solubility limit. • If you choose to specify solubilities for a fluid, you get implied partition factors. • If you clone a reference fluid, the partition factors = 1 and the solubilities can be different (if you use a link).