DATABASE: Scanning the Sediments

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Science  23 Jan 2004:
Vol. 303, Issue 5657, pp. 443
DOI: 10.1126/science.303.5657.443a

Whether you want to know phosphorus concentrations in east Texas streams or sodium levels in swamps near Miami, check out the National Geochemical Survey, a massive new database from the U.S. Geological Survey (USGS). The collection houses measurements of more than 60 elements—including arsenic, aluminum, lead, titanium, and phosphorus—at sites around the country. Such data can help everyone from geologists hunting for mineral deposits, to environmental scientists looking at pollution from farms and sewage plants that spurs algal blooms.

The database, which will eventually hold at least one sample for every 289 square kilometers (an area about two-thirds the size of Washington, D.C.), is about 70% complete. Most of the data come from streambed sediments, which can reflect even lower levels in soils because they receive runoff from a wide area. A set of maps highlights regional and national trends. This image, for example, shows levels across the United States of arsenic, a naturally occurring carcinogen that can taint drinking water. (Pink indicates the highest values, gray the lowest.) You can also obtain county averages or download figures for each sampling site. USGS plans to complete the survey by 2006.

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