PARENT SESSION
SA6 - Sorption of Hydrophobic Pollutants
Chair: Koelmans, Albert Bart¹, ¹ P.O. Box 8080, Wageningen, Wageningen, The Netherlands
8:00 AM to 12:00 PM - Sunday, 17 November 2002
Room Ballroom B

(060) Algal Biofilm Uptake of Micro-Organic Contaminants in an Artificial Riverine Environment.

Allan, Ian^*,1,2, House, Alan¹, Carter, Joy³, Parker, Andrew², Warren, Nicola², ¹ Centre for Ecology and Hydrology Dorset, Dorchester, Dorset, United Kingdom² University of Reading, Reading, United Kingdom³ University of Derby, Derby, United Kingdom

ABSTRACT- Previous monitoring of rivers entering the Humber estuary in the North-East of England revealed a wide distribution of several micro-organic contaminants in river sediments of the most-contaminated rivers i.e. the Aire and Calder. Consequently, four compounds exhibiting a broad range of physico-chemical characteristics, including simazine, lindane, nonylphenol and cis/trans Permethrin, were selected for more detailed transport studies using replicate fluvarium channels containing natural river sediment (River Calder) and flowing overlying water. The fate of these organic chemicals was studied simultaneously during two 6-week channel experiments with one experiment run in the dark with no biofilm development while the second one was carried out under natural light conditions, allowing growth of a natural algal and bacterial biofilm at the interface between bulk water and a 50 mm-deep bed of sediment. Sediment reworking by a natural assemblage of oligochaete worms was also observed. The fate and transport of organic compounds is explained by analysing their distribution in the various phases of the system, including the overlying water, bulk sediment vertically sectioned at a relatively fine depth resolution, interstitial waters and algal biofilm. Combining observations of development of the system with the distribution of the diverse compounds illustrates interdependence between key processes and the compounds fate and distribution. Differences in penetration into the sediment layer reflect compounds hydrophobicity with permethrin concentrated in the top 4 mm, while simazine diffuses to a depth of over 30 mm deep. Degradation of simazine in the water allows the development of an algal biofilm and hence the subsequent high sorption of permethrin (i.e. 1035-3379 g kg^-1 dry weight), nonylphenol (~512 g kg^-1 dry weight) and lindane (~978 g kg^-1 dry weight). Thus, comparison with bulk sediment and pore-water concentration depth-profiles, addresses the potential significance of those, sorbed or bio-accumulated, in the biofilm in the assessment of bioavailability of hydrophobic contaminants to benthic fauna i.e. fish, invetebrates, microbial communities or other river inhabitants.

Key words: micro-organic contaminants, river sediments, biofilm, concentration-depth profiles