Biocide testing using particles with controlled surface properties (Artificial sediments)

Sediments may play an important role in the accumulation of contaminants by benthic organisms. This work uses artificial particles to model natural sy stems and to provide a way of predicting bioavailability from sediment/cont aminant interactions. The artificial particles used were a range of high pe rformance liquid chromatography resins and a dimethylditallow ammonium-exch anged clay. The bioavailability of 2,4-dichlorophenol on these particles to the midge larva Chironomus riparius was compared with that from sand and a natural sediment. The experiments were designed so that water uptake and a ccumulation due to the ingestion of particles could be distinguished. The r esults show that very strong or very weak electrostatic interactions of the contaminant with the particles results in little accumulation of the conta minant via ingestion. When the contaminant is weakly bound to the particles by van der Waals forces, the contaminant can be released from the ingested particles. In these experiments, this occurred when the contaminant-partic le interaction was hydrophobic, and it is under these conditions that 2,4-d ichlorophenol was most bioavailable.