Mutagen Pollution: River Plume & Mutation-Frequency Simulator

Discharge Source

Discharge rate Q 55

River flow velocity v 0.9 m/s

Turbulent mixing D 0.18 m²/s

Degradation rate k 0.012 /s

Live Readouts

Peak conc.

0.0 mg/L

Elapsed

0 s

Mean mutation freq.

0.0 %

Max mutation freq.

0.0 %

Clean water (C ≈ 0)

Moderate exposure

Peak plume concentration

Organism, low mutation load

Organism, high mutation load

How it works

A mutagenic effluent (e.g. a nitrosamine or alkylating industrial byproduct) enters the river at a fixed point and is carried, spread and broken down as it travels downstream. The concentration field C(x,y,t) solved on the grid each frame follows the 2‑D advection–diffusion–decay equation:

∂C/∂t = D·∇²C − v·∂C/∂x − k·C + S(x,y)

D = turbulent mixing coefficient (m²/s)
v = mean flow velocity (m/s)
k = degradation rate — photolysis + microbial breakdown (1/s)
S = continuous point source at the discharge cell

Sixteen sentinel organisms are anchored downstream. Each integrates the local concentration it swims through into a cumulative dose, then converts that dose into a mutation frequency via the linear no-threshold (LNT) dose–response model used to read out Ames-test and other short-term mutagenicity assays:

dose_i(t) = ∫ C(x_i, y_i, τ) dτ   (cell-hours of exposure)

MF_i(t) = MF₀ + α · dose_i(t)

MF₀ = spontaneous background mutation frequency
α   = mutagenic potency slope of the compound

Discharge rate Q — source strength at the pipe outfall; higher Q raises the plume's peak concentration and everything downstream of it.
Flow velocity v — how fast the river carries the plume; faster flow thins the plume but shortens each organism's contact time per unit distance.
Turbulent mixing D — lateral/longitudinal spreading; higher D dilutes the plume faster but widens the exposed corridor.
Degradation rate k — how quickly the mutagen itself breaks down chemically or biologically, shrinking the effective dose reaching the far bank.
Organism spheres shift from green to red as their individual mutation frequency rises — the same dose–response logic environmental toxicologists use to set safe discharge limits.

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