PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM076) Dissolved organic matter in natural freshwaters: Comparative sorption, desorption and bioavailability of benzo[a]pyrene and 3,4,3′,4′–tetrachlorobiphenyl.
Akkanen, Jarkko1, Kukkonen, Jussi1, 1 University of Joensuu, Joensuu, Finland
ABSTRACT- Association with dissolved natural organic matter (DOM) has major implications for transport, fate and effects of many polluntans. However, stability of the interaction between pollutant and DOM is still in many ways unknown. Sorption of hydrophobic compound to DOM has been assumed to be rapid i.e. to reach equilibrium even in minutes. It has also been assumed that the sorption to DOM is reversible. The latter refers to the fact that sorption is simply a phase partitioning phenomena. However, most of the work, in which these assumptions are based, has been done with isolated humic fractions with polycyclic aromatic hydrocarbons. To test and challenge these assumptions we compared the behavior of two model compounds, benzo[a]pyrene (BaP) and 3,4,3′,4′–tetrachloropiphenyl (TCBP) in natural freshwaters containing DOM. Sorption of the model compounds was determined by the equilibrium dialysis and desorption was estimated with the Tenax-extraction method. The effects of DOM on bioavailability of the model compounds to Daphnia magna was also tested. We are presenting some differences and similarities in the speciation of the model compounds under the test conditions. For example, there was different features in sorption the model compounds and this partly reflected to the bioavailability of the compounds. Sorption of TCBP achieved equilibrium slower and was lower than that of BaP. There were also some differences in desorption, but both appeared to follow biphasic desorption kinetics, including a fast desorbing fraction, but also a significant desorption resistant fraction.
Key words: organic contaminant, DOM, sorption, desorption