Can we close the long-term mass balance equation for pollutants in highway ponds?

The paper discusses the prospects of finding the long-term mass balance on basis of short-term simulations. A step in this process is to see to which degree the mass balance equation can be closed by measurements. Accordingly the total accumulation of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in eight Danish detention ponds only receiving runoff from highways have been measured. The result shows that the incoming mass of heavy metals from short-term runoff events is accumulated. This is not observable in the same magnitude for the toxic organic compounds. The results also show that the accumulation rates significantly depend on the relative pond area (defined as the pond area divided by the catchment area). The conclusion is that the investigation indicates that a combination of short- and long-term viewpoints can close the mass balance for highway ponds with an acceptable accuracy.