Environmental Health - Toxic Substances Hydrology Program
USGS scientists and their colleagues have unexpectedly found large concentrations of nitrate in desert subsoils. This previously overlooked accumulation of nitrogen is surprising because desert ecosystems are known to have become adapted to a lack of nitrogen. However, the nitrate recently found is within a few meters of land surface and below the biologically active root zone. Contrary to conventional wisdom, small amounts of naturally occurring nitrate appear to have been leaching from soil layers and accumulating for thousands of years in the unsaturated zones of arid regions. Scientists are concerned about this high level (thousands of kilograms per hectare) of nitrate because
This finding built upon an understanding of how water moves in deserts-an understanding that scientists are advancing at the USGS's Amargosa Desert Research Site. Working at the site, scientists discovered that deserts in the southwest have been drying out since the ice age.
Walvoord, M.A., Phillips, F.M., Stonestrom, D.A., Evans, R.D., Hartsough, P.C., Newman, B.D., and Striegl, R.G., 2003, A reservoir of nitrate beneath desert soils: Science, v. 302, no. 7, p. 1021-1024
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