Novel Instruments for in Situ Continuous Rn-222 Measurement in Groundwater and the Application to River Bank Infiltration

详细信息    查看全文

• 作者：B. S. Gilfedder ; H. Hofmann ; I. Cartwright
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：January 15, 2013
• 年：2013
• 卷：47
• 期：2
• 页码：993-1000
• 全文大小：404K
• 年卷期：v.47,no.2(January 15, 2013)
• ISSN：1520-5851

文摘

There is little known about the short-term dynamics of groundwater鈥搒urface water exchange in losing rivers. This is partly due to the paucity of chemical techniques that can autonomously collect high-frequency data in groundwater bores. Here we present two new instruments for continuous in situ ²²²Rn measurement in bores for quantifying the surface water infiltration rate into an underlying or adjacent aquifer. These instruments are based on ²²²Rn diffusion through silicone tube membranes, either wrapped around a pole (MonoRad) or strung between two hollow end pieces (OctoRad). They are combined with novel, robust, low-cost Geiger counter ²²²Rn detectors which are ideal for long-term autonomous measurement. The down-hole instruments have a quantitative response time of about a day during low flow, but this decreases to <12 h during high-flow events. The setup was able to trace river water bank infiltration during moderate to high river flow during two field experiments. Mass-balance calculations using the ²²²Rn data gave a maximum infiltration rate of 2 m d^鈥?. These instruments offer the first easily constructible system for continuous ²²²Rn analysis in groundwater, and could be used to trace surface water infiltration in many environments including rivers, lakes, wetlands, and coastal settings.