The Urban Environmental Gradient:  Anthropogenic Influences on the Spatial and Temporal Distributions of Lead and Zinc in Sediments

Abstract

Urban settings are a focal point for environmental contamination due to emissions from industrial and municipal activities and the widespread use of motor vehicles. As part of the National Water-Quality Assessment Program of the U.S. Geological Survey, streambedsediment and dated reservoir-sediment samples were collected from the Chattahoochee River Basin and analyzed for total lead (Pb) and zinc (Zn) concentrations. The sampling transect extends from northern Georgia, through Atlanta, to the Gulf of Mexico and reflects a steep gradient in population density from nearly 1000 people/ km 2 in the Atlanta Metropolitan Area to fewer than 50 people/ km 2 in rural areas of southern Georgia and northern Florida. Correlations among population density, traffic density, and total and anthropogenic Pb and Zn concentrations indicate that population density is strongly related to traffic density and is a predictor of Pb and Zn concentrations in the environment derived from anthropogenic activities. Differences in the distributions of total Pb and Zn concentrations along the urban-suburban-rural gradient from Atlanta to the Florida Panhandle are related to temporal and spatial processes. That is, with the removal of leaded gasoline starting in the late 1970s, peak Pb concentrations have decreased to the present. Conversely, increased vehicular usage has kept Zn concentrations elevated in runoff from population centers, which is reflected in the continued enrichment of Zn in aquatic sediments. Sediments from rural areas also contain elevated concentrations of Zn, possibly in response to substantial power plant emissions for the region, as well as vehicular traffic.

Risk assessment of metals in road-deposited sediment along an urban–rural gradient

“…The urbanesuburbanerural gradient pattern is common in the context of rapid urbanization in China, and strongly affects land use zoning, population density, the proportion of surfaces that are impervious, traffic density, energy consumption, street cleaning methods, and spatial distribution of manufacturers (Callender and Rice, 2000;Zhao et al, 2011). Previous studies indicated that the urbanerural gradient had an important effect on RDS amounts, grain size composition, metal types and concentrations associated with it (Rogge et al, 1993;Kupiainen et al, 2005;Kim and Sansalone, 2008;Thorpe and Harrison, 2008).…”

Monitoring Land-Use and Land-Cover Change in the Eastern Gulf Coastal Plain 3 using Multi- temporal Landsat imagery

“…As a result of population growth, urban areas have been increasing in the study area, and the urban expansion rate from 1996 to 2005 was much higher than that in the previous decades, indicating more intensive land conversions from forest, cropland and other land use types to urban areas. Much concern on negative impacts of urban expansion has been raised, special attention should be paid to quantifying urbanization-induced changes in water quality, hydrology and biodiversity in rivers and coastal areas [10,11,13].…”

“…High proportions of impervious surface lead to increasing nutrient and sediment loads to streams [11]. Urban developments were reported to increase heavy metals, bacteria loadings, temperatures and other nutrients in streams [12][13][14]. Forest plantation for commercial purposes could dramatically alter water cycling through enhancing evapotranspiration and deteriorate water quality through applications of chemical fertilizers and pesticides [15].…”

Understanding the relationship between heavy metals in road-deposited sediments and washoff particles in urban stormwater using simulated rainfall

“…The urban-suburban-rural gradient pattern is has been strongly affected by rapid urbanization in China, and in turn affects land use zoning, population density, proportion of impervious surfaces, traffic density, energy consumption, street cleaning methods, and spatial distribution of manufacturers [6,22]. Therefore, the urban-rural gradient could affect the amounts and proportions of different chemical fractions of heavy metals in RDS and washoff particles by influencing the particle size of RDS, the metals associated with RDS and the RDS washoff process.…”