RESEARCH ON EFFECTS
OF SEDIMENT BIOGEOCHEMISTRY ON THE ENVIRONMENTAL
FATE AND PERSISTENCE
OF POLYCHLORINATED BIPHENYLS (PCBs)
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GENERAL INFORMATION ON PCBs
Polychlorinated biphenyls (PCBs), 209 compounds formerly
manufactured and used in liquid mixtures as insulation in electric equipment, are
toxic pollutants that persist in the environment. PCBs have contaminated a number of major
rivers and coastal waters of the
Commercial PCB mixtures comprised 209 different PCB compounds which are defined by the position and number of chlorines attached to the biphenyl structure. Figure 1 depicts biphenyl (left) and two polychlorinated biphenyls. Each PCB compound is characterized by a unique bioavailability, toxicity, and environmental persistence.
Figure 1. Biphenyl and polychlorinated biphenyl
structures. Ortho, para,
and meta
positions are identified on the biphenyl.
The middle compound
is 2,3,3’,4,4’,5,5’
heptachlorobiphenyl, and the compound on the right is
3,4’ dichlorobiphenyl.
Figure 2 shows the numbering system for naming individual PCB compounds, or congeners.
Figure 2.
Numbering system for PCB congeners.
The connection between the phenyl rings involves the 1 and 1' carbons. The 2, 2', 6 and 6' positions are termed ortho, the 3, 3', 5, and 5' positions
are meta, and the 4 and 4' positions
are para.
Additional information about PCBs, including their toxicity, physical-chemical properties, occurrence in the environment, and effects on aquatic ecosystems is provided via the links given below.
CDC-ATSDR information on toxicity of PCBs
EPA information on Hudson River Superfund Site
EPA Great Lakes Interagency Task Force
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