Detection of Persistent Organic Pollutants in the Mississippi Delta Using Semipermeable Membrane Devices

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Abstract

Persistent organic pollutants (POPs) are hazardous chemicals, with moderate to low volatility, that resist degradation and tend to accumulate in living tissues. Their persistence in various media facilitates their transport over long distances to remote regions where they have never been used. They have been found to present risks to human health and the environment in polar and other regions. In February 1997, a United Nations Environmental Program Governing Council Decision identified 12 specific POPs (aldrin, chlordane, DDT, dieldrin, dioxins, endrin, furans, heptachlor, hexachlorobenzene, mirex, polychlorinated biphenyls, and toxaphene) for which international action was deemed necessary to protect human health and the environment.

Semipermeable membrane devices (SPMDs) passively accumulate hydrophobic organic compounds when placed in an aquatic environment. They consist of a low-density polyethylene (LDPE) lay-flat membrane filled with 1 gram of a high molecular weight lipid, triolein, that cannot diffuse through the membrane. The LDPE membrane mimics a biological membrane in its ability to allow selective diffusion of organic compounds. After the deployment period, SPMDs are retrieved from the stream, dialyzed, cleaned up with gel permeation chromatography and silica gel, and analyzed using gas chromatography/mass spectrometry (GC/MS) or gas chromatography/electron capture (GC/ECD) techniques.

From SPMDs placed in five Mississippi Delta streams in 1996 and 1997, the POPs aldrin, chlordane, DCPA, DDT, dieldrin, endrin, heptachlor, hexachlorobenzenes, mirex, nonachlor, and toxaphene were detected. In addition, two insecticides still in use, the organophosphate chlorpyriphos and the organochlorine endosulfan, were detected. Two low-solubility herbicides not detected commonly in surface water, pendimethalin and trifluralin, also were detected.

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Zimmerman, L.R., Thurman, E.M., and Bastian, K.C., 1999, Detection of persistent organic pollutants in the Mississippi Delta using semipermeable membrane devices, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the technical meeting, Charleston, South Carolina, March 8-12, 1999, volume 2 of 3--Contamination of hydrologic systems and related ecosystems: U.S. Geological Survey Water-Resources Investigations Report 99-4018B, p. 367-378.

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