HR: 08:48h
AN: H41K-04    [Abstracts]
TI: Natural Perchlorate and Climate-An Imperfect Relationship
AU: * Orris, G J
EM: greta@usgs.gov
AF: U.S. Geological Survey, 520 N. Park Ave., Ste. 355, Tucson, AZ 85719, United States
AU: Jackson, W A
EM: Andrew.Jackson@coe.ttu.edu
AF: Civil Engineering, Texas Tech University, MS 41023, Lubbock, TX 79409, United States
AU: Harvey, G J
EM: Gregory.Harvey@wpafb.af.mil
AF: U.S. Air Force, 1801 10th St., Bldg. 8, Suite 200 Area B, Wright-Patterson A A, OH 45433USA,
AU: Betancourt, J
EM: jlbetanc@usgs.gov
AF: Desert Laboratory, U.S. Geological Survey, 1675 W. Anklam Rd., Tucson, AZ 85719, United States
AB: The distribution of natural perchlorate has a strong climatic link; this is not unexpected given that perchlorate forms in the upper atmosphere and is transported to the earth's surface through wet and dry precipitation. Occurrences of high levels of natural perchlorate in plants, soils, sediments, and some water tend to be correlated with varying degrees of aridity. The processes that are known to concentrate perchlorate are restricted to, or work more efficiently, in dry climates. Processes in more temperate climates, such as dissolution and mobilization, work against perchlorate accumulations. Studies to date have shown that plants and soils that occur in both arid and more temperate environments tend to contain more perchlorate in the arid settings. The association of natural perchlorate with dry climates can be found in both modern settings and in pre-industrial materials such as rodent middens and sediments that are thousands to millions of years old. Nevertheless, there are exceptions to this relationship; perchlorate has been found in unexpectedly high concentrations in plants, soils/sediments, and water where the climate would indicate relatively low concentrations and there is no identifiable source of anthropogenic perchlorate. Other natural processes seem to contribute to accumulations of perchlorate. In some places, unexpectedly high perchlorate levels are spatially associated with contemporaneous volcanism that may have contributed perchlorate. Other indirect evidence indicates that some plants may manufacture their own perchlorate under conditions that are not yet fully understood. As with most phenomena in nature, the occurrence and concentration of perchlorate in the environment is complex and that complexity offers many avenues for future research into areas as diverse as processes of formation and concentration and human exposure pathways.
DE: 1105 Quaternary geochronology
DE: 1813 Eco-hydrology
DE: 1833 Hydroclimatology
DE: 1852 Plant uptake
DE: 1865 Soils (0486)
SC: Hydrology [H]
MN: 2007 Fall Meeting