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Distribution of Organic Wastewater Contaminants Between Water and Sediment in Surface Waters of the United States

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Abstract:Trace concentrations of pharmaceuticals and other organic wastewater contaminants have been determined in the surface waters of Europe and the United States. A preliminary report of substantially higher concentrations of pharmaceuticals in sediment suggests that bottom sediment may be an important reservoir of pharmaceuticals discharged to surface water.

The U.S. Geological Survey undertook a systematic examination of bottom sediment collected from a dozen sites across the United States, in order to determine the range of compositions and concentrations of pharmaceuticals and other organic wastewater contaminants present in those sediments. Composite sediment samples were collected at one point upstream and two points downstream of a point source discharge. Surface water samples were collected concurrently at the same sites, as well as at the point discharge. The samples were shipped by overnight express and water samples were analyzed within 48 hours of receipt. Sediments were held frozen until extraction and analysis. Pharmaceuticals were extracted from filtered water samples by solid-phase extraction and the concentrated extract analyzed by high-performance liquid chromatography/mass spectrometry (HPLC/MS). Other organic wastewater contaminants were extracted from whole-water samples by continuous liquid-liquid extraction followed by gas chromatography/mass spectrometry (GC/MS; Kolpin and others, 2002). Sediments were extracted by accelerated solvent extraction and the extracts analysed by HPLC/MS (pharmaceuticals) or GC/MS (other wastewater constituents).

Preliminary results indicate that a wide range of pharmaceuticals and other wastewater constituents are present in sediments at concentrations substantially higher than in surface water. For example, caffeine, a highly water soluble contaminant, has estimated partitioning coefficient of 0.85, suggesting that concentrations should be higher in water than in sediment. However, the ratio observed for caffeine in environmental samples ranges between 4 and 136. Similarly, the predicted partitioning coefficient for trimethoprim is 8.2, while the observed partitioning coefficients range between 17 and 1,100. Also, as water and sediment concentrations increase, the observed partitioning coefficient more closely approaches the predicted partitioning coefficient. Further, pharmaceuticals were not detected in pore-water samples, suggesting that pharmaceuticals are intimately associated with the sediment phase. Taken together, these data suggest that sediments are potentially important reservoir for sequestering pharmaceuticals in surface water systems. Determining the mechanisms of association between water-soluble pharmaceuticals and sediment will be an important new area of research.
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Citation:Furlong, E. T., I. Ferrer, S. Glassmeyer, J. D. Cahill, S. D. Zaugg, S. L. Werner, D. W. Kolpin, and D. D. Kryak. Distribution of Organic Wastewater Contaminants Between Water and Sediment in Surface Waters of the United States. Presented at National Groundwater Association 3rd International Conference on Pharmaceuticals and Endocrine Disrupting Chemicals in Water, Minneapolis, MN, March 19-21, 2003.
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Contact: Mary P. O'Bryant - (919)-541-4871 or obriant.mary@epa.gov
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Division: Microbiological & Chemical Exposure Assessment Division
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Branch: Chemical Exposure Research Branch
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Product Type: Abstrct/Oral
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Presented: 03/19/2003
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Related Entries:
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Bullet Item Chemical Indicators of Human Fecal Contamination
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Last Updated on Monday, October 22, 2007
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