Scientists say the atmospheric concentrations of such chemicals have peaked and are slowly decreasing.

The concentration in Oslo decreased somewhat from 1998 to 2008, however.

Therefore, as you heat the solution, the solute concentration decreases.

Once the gas is released into the atmosphere, its concentration decreases and it is no longer dangerous.

That's unusual because concentrations of those elements normally decrease with depth in this region.

Since 1980 the national concentration of SO in the ambient air has decreased by 83%.

The concentration of solids in the water has been decreasing since at least the 1990s.

After six hours has passed, the concentration of marijuana in the blood decreases significantly.

I'd guess the concentration decreases exponentially with distance from the surface.

CO concentration then decreases from about 0.08% to 0.04%, the ambient atmospheric level.