TOXICANT-LOADING CONCEPT FOR ORGANIC CONTAMINANTS IN LAKES

The analysis focuses on a steady-state budget model. To simplify the analysis, the mechanisms of decay and diffusive sediment feedback are ignored. These omissions result in a lower-bound representation of the net loss rate that is dependent on three processes: sorption, volatilization, and sediment resuspension. In order to investigate the interaction of these processes, the net loss rate is mapped on a space defined by sorption and volatilization dimensions. On this space, three zones are identified. The air zone contains substances that sorb weakly, are highly insoluble, and would exhibit high removal rates due to volatilization. At the other extreme, the water zone, substances that sorb weakly and are soluble have low removal rates because they are not subject to sedimentation or volatilization. The third area, the sediment zone, is populated by strong sorbers that are primarily governed by sediment resuspension. Among the organic priority pollutants, the halogenated aliphatics and most of the monocyclic aromatics reside in the air zone and should experience rapid purging. A significant number of pesticides, phenols, phthalate esters and nitrosamines fall in the water and sediment zones. These could represent problem compounds from the perspective of a weak assimilative capacity.