| Abstract
| - Urban settings are a focal point for environmentalcontamination due to emissions from industrial andmunicipal activities and the widespread use of motorvehicles. As part of the National Water-Quality AssessmentProgram of the U.S. Geological Survey, streambed-sediment and dated reservoir-sediment samples werecollected from the Chattahoochee River Basin and analyzedfor total lead (Pb) and zinc (Zn) concentrations. Thesampling transect extends from northern Georgia, throughAtlanta, to the Gulf of Mexico and reflects a steepgradient in population density from nearly 1000 people/km2 in the Atlanta Metropolitan Area to fewer than 50 people/km2 in rural areas of southern Georgia and northernFlorida. Correlations among population density, trafficdensity, and total and anthropogenic Pb and Zn concentrationsindicate that population density is strongly related totraffic density and is a predictor of Pb and Zn concentrationsin the environment derived from anthropogenic activities.Differences in the distributions of total Pb and Znconcentrations along the urban−suburban−rural gradientfrom Atlanta to the Florida Panhandle are related totemporal and spatial processes. That is, with the removalof leaded gasoline starting in the late 1970s, peak Pbconcentrations have decreased to the present. Conversely,increased vehicular usage has kept Zn concentrationselevated in runoff from population centers, which is reflectedin the continued enrichment of Zn in aquatic sediments.Sediments from rural areas also contain elevatedconcentrations of Zn, possibly in response to substantialpower plant emissions for the region, as well as vehiculartraffic.
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