Geochemical Triggers of Arsenic Mobilization during Managed Aquifer Recharge

详细信息    查看全文

• 作者：Sarah Fakhreddine ; Jessica Dittmar ; Don Phipps ; Jason Dadakis ; Scott Fendorf
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：July 7, 2015
• 年：2015
• 卷：49
• 期：13
• 页码：7802-7809
• 全文大小：360K
• ISSN：1520-5851

文摘

Mobilization of arsenic and other trace metal contaminants during managed aquifer recharge (MAR) poses a challenge to maintaining local groundwater quality and to ensuring the viability of aquifer storage and recovery techniques. Arsenic release from sediments into solution has occurred during purified recycled water recharge of shallow aquifers within Orange County, CA. Accordingly, we examine the geochemical processes controlling As desorption and mobilization from shallow, aerated sediments underlying MAR infiltration basins. Further, we conducted a series of batch and column experiments to evaluate recharge water chemistries that minimize the propensity of As desorption from the aquifer sediments. Within the shallow Orange County Groundwater Basin sediments, the divalent cations Ca²⁺ and Mg²⁺ are critical for limiting arsenic desorption; they promote As (as arsenate) adsorption to the phyllosilicate clay minerals of the aquifer. While native groundwater contains adequate concentrations of dissolved Ca²⁺ and Mg²⁺, these cations are not present at sufficient concentrations during recharge of highly purified recycled water. Subsequently, the absence of dissolved Ca²⁺ and Mg²⁺ displaces As from the sediments into solution. Increasing the dosages of common water treatment amendments including quicklime (Ca(OH)₂) and dolomitic lime (CaO路MgO) provides recharge water with higher concentrations of Ca²⁺ and Mg²⁺ ions and subsequently decreases the release of As during infiltration.