Mobilization of Naturally Occurring Perchlorate Related to Land-Use Change in the Southern High Plains, Texas

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• 作者：Bridget R. Scanlon ; Robert C. Reedy ; W. Andrew Jackson ; Balaji Rao
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：December 1, 2008
• 年：2008
• 卷：42
• 期：23
• 页码：8648-8653
• 全文大小：285K
• 年卷期：v.42,no.23(December 1, 2008)
• ISSN：1520-5851

文摘

Perchlorate (ClO₄⁻) reservoirs that accumulated in semiarid unsaturated zones, similar to chloride (Cl⁻), can contaminate underlying aquifers if they are mobilized. The purpose of this study was to evaluate ClO₄⁻ mobilization related to land-use change from natural to agricultural ecosystems in the southern High Plains (SHP, USA), where large ClO₄⁻ concentrations (≤60 μg/L) are found in the underlying Ogallala aquifer. Boreholes were drilled and sampled beneath natural ecosystems (3 boreholes) and beneath nonirrigated (rainfed, 7 boreholes) agricultural ecosystems. Large ClO₄⁻ reservoirs (361−934 g ClO₄⁻/ha; peaks 47−111 μg ClO₄⁻/L pore water), that accumulated for up to 30,000 yr under natural ecosystems, are being displaced to depths of 2.2 to >9.2 m in sampled boreholes under rainfed agriculture by increased drainage/recharge. High correlations between ClO₄⁻ and Cl⁻ under natural areas (r = 0.81) and rainfed agricultural areas (r = 0.88) indicate that accumulation and mobilization of ClO₄⁻ can be predicted from Cl⁻ data. Minimal analysis of ClO₄⁻ (e.g., two points, minimum and maximum Cl⁻ concentrations in each profile) can be used to predict ClO₄⁻ inventories to within 9% of estimates based on detailed sampling. A pooled linear regression model based on all data in this study (99 points) predicts ClO₄⁻ inventories to within 19% of measured inventories. Continued mobilization of pre-existing unsaturated zone ClO₄⁻ reservoirs (361−934 g/ha) could increase the current groundwater ClO₄⁻ values by a further 8−21 μg/L in the SHP.