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 different concentrations. Pore water was isolated by centrifugation, and a reverse-phase C 18 column technique was used to separate freely dissolved dieldrin from dissolved organic carbon (DOC)-bound dieldrin. Results showed DOC-bound dieldrin was generally >30% when pore-water DOC concentrations were >20 mg/L. Pore-water DOC partition coefficients (K DOC ) were determined for AP, PQ Lake, and WB Lake using the ratio of the DOC-bound chemical concentration (normalized to DOC) to the freely dissolved chemical concentration. The individual partition coefficients were compared by one-way analysis of variance. Statistical analysis revealed that K DOC values were not significantly different. This suggests that under our experimental procedures, K DOC values are not significantly different among pore waters obtained from the three northeastern Minnesota lake sediments. A pooled K DOC was calculated using 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 pooled log 10 K DOC value of 4.43. Our observed K DOC was compared to K DOC values predicted from published K DOC and K ow w (octanol/water partition coefficient) relationships. Our observed value was in close agreement with predicted values