Binding of natural humic matter to polycyclic aromatic hydrocarbons in rivers of the Southeastern United States

The binding constants (Koc) of four polycyclic aromatic hydrocarbons (PAH) were determined for sedimentary fulvic and humic acids and the dissolved organic carbon (DOC) of five rivers in Georgia, USA. The log Koc for the PAH ranged: anthracene, 4.63-5.57; phenanthrene, 4.58-5.62; pyrene, 4.90-5.65; benzo(a)pyrene, 3.48-5.20. Log Koc values for the PAH compounds with riverine DOC were very similar for all rivers and more closely resembled those of sedimentary humic acids than the fulvic acids. The molecular size distribution of the riverine DOC indicates that >75% of the DOC occurs in size fractions >10,000 daltons. Despite similarities in Koc, there appear to be inter-river differences in the distribution of PAH among molecular size classes of the DOC, which have ramifications for water quality both in rivers and estuaries.