Getting the dirt on soil
The U.S. Geological Survey has released a set of maps depicting the distribution of selected chemical elements and minerals in soils across the country.
click image to zoomU.S. Geological SocietySample map: Note higher lead levels in the northeastern U.S. Understanding the composition of soil is important for a variety of reasons. Specialists in agriculture and food safety find soil data useful because soil is the source of most biologically active trace elements that reach humans through the food chain. Public health specialists need to understand soil pathways for human exposure to potentially toxic elements. Regulators and resource managers use soil data to identify contamination, assess the risks to ecosystems and human health from contamination, and to set remediation goals. The maps and data sets serve as a starting point for future research in a variety of fields.
Soils play a key role for the Earth’s life support system in a number of ways such as determining human health and ecosystem integrity. They are required for supporting food production and needed for water storage and groundwater recharge. Soils are critical in the natural cycling of carbon and essential nutrients.
According to Dave Smith, the USGS scientist who led this project, “These data and maps are not designed to provide detailed soil information about what might be in your backyard. Rather they put your backyard into a national context so you can know the general range of element concentrations that are in soils from your part of the country.”
This USGS project delineates national-scale patterns and variations in elemental composition for soils. This new study provides a more complete understanding of natural variability for the nation’s soils than has ever been available.
To produce the maps, about 40 people collected thousands of soil samples from more than 4,800 sites throughout the conterminous U.S. from 2007 to 2010. For each site, they collected three samples from the surface down to about three feet. In total, scientists analyzed more than 14,000 soil samples for 45 elements and nearly 10,000 samples for major minerals.
The USGS data sets for soil geochemistry and mineralogy provide a baseline for the amount and distribution of chemical elements and minerals against which scientists can measure future changes from natural processes or human activities.
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