Evaluating the impact of a carbon amendment in managed aquifer recharge site sediments on redox sensitive elements
Abstract
Aside from increasing water quantity, managed aquifer recharge (MAR) sites provide an opportunity for improving groundwater quality during infiltration of surface water. Natural subsurface conditions can be modified with a carbon amendment, such as wood chips or biochar, to influence redox chemistry in the subsurface. While carbon amendments have been shown to increase denitrification and reduce N loading, these amendments may also trigger mobilization of redox sensitive elements, particularly trace metals. We are assessing the influence of a carbon amendment on the leaching potential of redox sensitive elements in water with a series of batch and column experiments. Sediment cores were extracted from sites in central coastal California with sonic drilling technology, one from a current MAR site and the other from a potential MAR site, to depths up to 40 m below ground surface. Sediment was collected every 0.21 m and will be digested to measure the total bioavailable trace element content. Microcosm experiments will be conducted to assess the sediment's leaching potential under a carbon source (redwood chips) as compared to control experiments without an amendment. Columns in series, preceded with a carbon source and run concurrently with a control, will translate the findings from the microcosm experiments to the potential leaching of trace elements as water flows through sediment columns. Grain size analyses, total carbon and nitrogen, and X-ray diffraction data will provide further insight into the subsurface composition.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H43I2587S
- Keywords:
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- 1831 Groundwater quality;
- HYDROLOGYDE: 1848 Monitoring networks;
- HYDROLOGYDE: 1849 Numerical approximations and analysis;
- HYDROLOGYDE: 1871 Surface water quality;
- HYDROLOGY