Reactix is a Python package for simulating reactive transport of chemical species suitable for one-dimensional systems with advection, dispersion and kinetic reactions. Reaction kinetics can be defined flexibly in plain Python. The package combines a finite volume discretization in space with advanced ODE solvers from diffrax for efficient time integration.

Reactix is built on the JAX ecosystem which provides automatic differentiation, making the models fully differentiable. This enables the use of gradient-based methods for sensitivity analysis and uncertainty quantification. The package integrates seamlessly with PyMCfor Bayesian modeling and parameter estimation.

Consider using Reactix if you…

• want to easily implement models with custom reaction kinetics,
• can reasonably simplify the system to one spatial dimension (e.g., column experiment, groundwater transport along a flow line),
• want to quantify parameter uncertainty with Bayesian methods,
• like to script your model in Python instead of using graphical interfaces or input files.

Reactix might not be the right choice if…

• your model needs to be 2-D or 3-D,
• the system involves a lot of equilibrium chemical reactions (like in PHREEQC),
• you want to couple groundwater flow and transport simulations.

This project is still under development. While most features are implemented by now, the API may still change, and documentation is largely missing at this point. The folder notebooks contains Jupyter notebooks that illustrate usage. If you are interested in trying out the package, feel free to reach out with any questions.

For questions about this project, please open an issue or contact Anna Störiko (a.storiko@tudelft.nl).