DETERMINATION OF DIELDRIN BINDING TO DISSOLVED ORGANIC MATERIAL IN SEDIMENT PORE-WATER USING A REVERSE-PHASE SEPARATION TECHNIQUE

The objective of our study was to examine the partitioning of dieldrin in sediment interstitial (pore) water. Clean sediments obtained from three northeastern Minnesota lakes, Airport Pond (AP), Pequaywan (PQ) Lake, and West Bearskin (WB) Lake, were spiked with dieldrin at five d ifferent concentrations. Pore water was isolated by centrifugation, an d a reverse-phase C-18 column technique was used to separate freely di ssolved dieldrin from dissolved organic carbon (DOC)-bound dieldrin. R esults showed DOC-bound dieldrin was generally >30% when pore-water DO C concentrations were >20 mg/L. Pore-water DOC partition coefficients (K-DOC) were determined for AP, PQ Lake, and WB Lake using the ratio o f the DOC-bound chemical concentration (normalized to DOC) to the free ly dissolved chemical concentration. The individual partition coeffici ents wee compared by one-way analysis of variance. Statistical analysi s revealed that K-DOC values were not significantly different. This su ggests that under our experimental procedures, K-DOC values are not si gnificantly different among pore waters obtained from the three northe astern Minnesota lake sediments. A pooled K-DOC was was calculated usi ng least-squares regression and compared to the mean of all individual K-DOC values. The K-DOC is best represented for this region by a pool ed log(10) K-DOC value of 4.43. Our observed K-DOC was compared to K-D OC values predicted from published KDOC and Kow (octanol/water partiti on coefficient) relationships. Our observed value was in close agreeme nt with predicted values.