Sorption and chemical reactions of PAHs with dissolved humic substances and related model polymers

Sorption coefficients measured for PAHs on dissolved humic substances by SP ME and FQT were found to be inevitably different and method-dependent - SPM E provides activity-based and FQT concentration-based sorption coefficients . Poly(acrylic acid) esters as well-defined model polymers were used in sorpt ion experiments, leading to the conclusion that short aliphatic chains are more effective in binding PAHs than aromatic moieties. FQT was inappropriat e to measure sorption coefficients for the interaction of pyrene with poly( acrylic acid) esters but the experiments revealed a characteristic shift in the fluorescence spectrum. Using pyrene as a probe for the molecular envir onment in the sorbed state, the observed spectral shift indicated a highly hydrophobic microenvironment. The empirical relationships between Ig K-DOC and Ig K-OW were generalized o n the basis of a modified Flory-Huggins concept. Introducing only one sorbe nt-specific parameter, the solubility parameter delta (DOM), the calculatio n of sorption coefficients became possible for a wide range of HOCs using f undamental data readily available from the literature. Long-term experiments showed that reactive PAHs (such as acenaphthylene and 9-methyl-anthracene) are able to react with HAs under strictly abiotic and anoxic conditions, whereas less reactive PAHs (such as naphthalene and dih ydroanthracene) do not form bound residues. The HA reveals two functions in the interaction, behaving as a reaction partner and as a protecting ligand .