Thermally Released Arsenic in Porewater from Sediments in the Cold Lake Area of Alberta, Canada

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• 作者：Muhammad Babar Javed ; Tariq Siddique
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：March 1, 2016
• 年：2016
• 卷：50
• 期：5
• 页码：2191-2199
• 全文大小：405K
• ISSN：1520-5851

文摘

Elevated arsenic (As) in aquifers in close proximity to in situ oil sands extraction in the Cold Lake area, Alberta, Canada is attributed to high temperature steam (∼200 °C) injected into oil sands deposits to liquefy bitumen. Heat propagated from hot injection wells alters physicochemical properties of the surrounding sediments and associated porewater. Seven sediments from four different cores drilled up to ∼300 m depth collected from different locations in the area were used to study the thermal effect (∼200 °C) on As distribution in the sediments and its release into porewater. Sediments were moistened with synthetic aquifer or deionized water according to the moisture regimes present in aquitard, aquifer and fractured zones. Heat application greatly released As in the porewater (500–5200 and 1200–6600 μg L^–1) from aquifer and fractured sediments, respectively. Mass balance of As chemical fractionation showed that ∼89–100% of As in porewater was released from exchangeable and specifically adsorbed As in the sediments. Heat application also altered As distribution in the sediments releasing As from exchange surfaces and amorphous Fe oxides to soluble As fraction. The results provide great insight into As release mechanisms warranting development of strategies to mitigate groundwater As contamination during industrial operation.