Sorption of very hydrophobic organic Compounds (VHOCs) on dissolved humic organic matter (DOM). 2. Measurement of sorption and application of a Flory-Huggins concept to interpret the data

Sorption phenomena of very hydrophobic compounds (VHOCs, log K-OW > 5) on d issolved humic organic matter (DOM) are overwhelmingly based on partitionin g processes. In this respect, DOM is very similar to "rubbery" soil/sedimen t OM. To exclude system adsorption effects, the DOM sorption coefficients ( K-DOM) Of VHOCs were determined using a dynamic approach based on the VHOCs ' aqueous solubility enhancement in the presence of DOM. Partition coeffici ents are strongly correlated to the analytes' K-OW across the alkane, PAH, and PCB groups under study. These three "families" are regarded to be good models of hydrophobic partitioning. On the basis of a uniform one-parameter concept characterizing sorption on amorphous polymers, Hildebrand solubili ty parameters of amorphous polymeric sorbents, including DOM, and of sorbat es can be calculated on the basis of partition coefficients. Likewise, part ition coefficients can be estimated using Hildebrand solubility parameters. Literature-based partition coefficients on DOM fit very well in this unive rsal one-parameter concept. On using our own sorption data of PAHs, PCBs, a nd alkanes on DOM, an almost identical solubility parameter for the DOM pol ymer under study is obtained. The concept is also very useful in understand ing both waterborne and airborne bioconcentration processes, which are cons idered to be partitioning phenomena.