PARTITIONING OF POLYCHLORINATED DIOXINS AND FURANS BETWEEN WATER, SEDIMENTS AND BIOTA IN LAKE MESOCOSMS

The partitioning and bioavailability of C-14-1,3,6,8-TCDD (TCDD), octachlorodioxin (OCDD), and H-3-2,3,7,8-TCDF were studied in lake water and natural sediments using limnocorrals (5 m dia, 2 m depth) located in the littoral zone of small Canadian shield lakes. The PCDD/F's were associated almost entirely with particulates or with dissolved organic carbon (DOC) in the water column and in sediment pore waters. Most of the TCDF on particulates in the water column was associated with the 0.22-1.0-mu-m size fraction and lowest concentrations with particles >20-mu-m. Highest bioavailability indices (conc'n organism lipid/conc'n organic carbon) were achieved for organisms filtering or ingesting organic particles (mussels, chironomids) and those consuming benthic organisms (crayfish, suckers).