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

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• 作者：Srinath Rajagopalan ; Todd A. Anderson ; Lynne Fahlquist ; Ken A. Rainwater ; Moira Ridley ; and W. Andrew Jackson
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：May 15, 2006
• 年：2006
• 卷：40
• 期：10
• 页码：3156 - 3162
• 全文大小：415K
• 年卷期：v.40,no.10(May 15, 2006)
• ISSN：1520-5851

文摘

Perchlorate (ClO₄^-) occurrence in groundwater haspreviously been linked to industrial releases and thehistoric use of Chilean nitrate fertilizers. However, recentlya number of occurrences have been identified for whichthere is no obvious anthropogenic source. Groundwater froman area of 155 000 km² in 56 counties in northwestTexas and eastern New Mexico is impacted by the presenceof ClO₄^-. Concentrations were generally low (<4 ppb),although some areas are impacted by concentrations upto 200 ppb. ClO₄^- distribution is not related to well type (publicwater system, domestic, agricultural, or water-tablemonitoring) or aquifer (Ogallala, Edward Trinity High Plains,Edwards Trinity Plateau, Seymour, or Cenozoic). Resultsfrom vertically nested wells strongly indicate a surface source.The source of ClO₄^- appears to most likely be atmosphericdeposition. Evidence supporting this hypothesis primarilyrelates to the presence of ClO₄^- in tritium-free older water,the lack of relation between land use and concentrationdistribution, the inability of potential anthropogenic sourcesto account for the estimated mass of ClO₄^-, and thepositive relationship between conserved anions (e.g., IO₃^-,Cl^-, SO₄^-2) and ClO₄^-. The ClO₄^- distribution appears tobe mainly related to evaporative concentration andunsaturated transport. This process has led to higherClO₄^- and other ion concentrations in groundwater wherethe water table is relatively shallow, and in areas withlower saturated thickness. Irrigation may have acceleratedthis process in some areas by increasing the transportof accumulated salts and by increasing the numberof evaporative cycles. Results from this study highlightthe potential for ClO₄^- to impact groundwater in arid and semi-arid areas through long-term atmospheric deposition.