Fig. 4. Potential surface (negative log potential) vs. pollutant in region 1 and region 2 for four different input rates to region 1. Parameters: M1 (pollution discharge rate in region 1) = 1.25, 1.5, 1.75, and 2; M2 (pollution discharge rate in region 2) = 0.75; c1 (decay rate in region 1) = 0.05; c2 (decay rate in region 2) = 0.1; D (transport rate between regions) = 0.1; s (maximum sequestration rate) = 0.5; m (the pollutant level at which sequestration is half the maximum rate) = 5; q (which determines the slope of f(P) near P) = 6. P stands for amount of pollutant, and f(P) scales the sequestration to the amount of pollutant.