[CPEO-MEF] Perchlorate in the High-Texas plains

[Lenny Siegel <lsiegel@cpeo.org>]

Widespread Presence of Naturally Occurring Perchlorate in High Plains of 
Texas and New Mexico

Srinath Rajagopalan, Todd A. Anderson, Lynne Fahlquist, Ken A. 
Rainwater, Moira Ridley, and W. Andrew Jackson*

Environmental Science & Technology
Accepted March 10, 2006

Abstract:

Perchlorate (ClO4-) occurrence in groundwater has previously been linked 
to industrial releases and the historic use of Chilean nitrate 
fertilizers. However, recently a number of occurrences have been 
identified for which there is no obvious anthropogenic source. 
Groundwater from an area of 155 000 km2 in 56 counties in northwest 
Texas and eastern New Mexico is impacted by the presence of ClO4-. 
Concentrations were generally low (<4 ppb), although some areas are 
impacted by concentrations up to 200 ppb. ClO4- distribution is not 
related to well type (public water system, domestic, agricultural, or 
water-table monitoring) or aquifer (Ogallala, Edward Trinity High 
Plains, Edwards Trinity Plateau, Seymour, or Cenozoic). Results from 
vertically nested wells strongly indicate a surface source. The source 
of ClO4- appears to most likely be atmospheric deposition. Evidence 
supporting this hypothesis primarily relates to the presence of ClO4- in 
tritium-free older water, the lack of relation between land use and 
concentration distribution, the inability of potential anthropogenic 
sources to account for the estimated mass of ClO4-, and the positive 
relationship between conserved anions (e.g., IO3-, Cl-, SO4-2) and 
ClO4-. The ClO4- distribution appears to be mainly related to 
evaporative concentration and unsaturated transport. This process has 
led to higher ClO4- and other ion concentrations in groundwater where 
the water table is relatively shallow, and in areas with lower saturated 
thickness. Irrigation may have accelerated this process in some areas by 
increasing the transport of accumulated salts and by increasing the 
number of evaporative cycles. Results from this study highlight the 
potential for ClO4- to impact groundwater in arid and semi-arid areas 
through long-term atmospheric deposition.

For the original abstract or to download the entire article (NON-ES&T 
SUBSCRIBERS MUST PAY A FEE), go to
http://dx.doi.org/10.1021/es052155i



--


Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org

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