Linking nitrate removal, carbon cycling, and mobilization of geogenic trace metals during infiltration for managed recharge.

We present results from a series of laboratory column studies investigating the impacts of infiltration dynamics and the addition of a soil-carbon amendment (wood mulch or almond shells) on water quality during infiltration for flood-managed aquifer recharge (flood-MAR). Recent studies suggest that nitrate removal could be enhanced during infiltration for MAR through the application of a wood chip permeable reactive barrier (PRB). However, less is understood about how other readily available carbon sources, such as almond shells, could be used as a PRB material, and how carbon amendments could impact other solutes, such as trace metals.

Soil characteristics and redox properties of infiltrating water are determinants of microbial communities at managed aquifer recharge sites.

In this study, we conducted a meta-analysis of soil microbial communities at three, pilot-scale field sites simulating shallow infiltration for managed aquifer recharge (MAR). We evaluated shifts in microbial communities after infiltration across site location, through different soils, with and without carbon-rich amendments added to test plots. Our meta-analysis aims to enable more effective MAR basin design by identifying potentially important interactions between soil physical-geochemical parameters and microbial communities across several geographically separate MAR basins.

Enhanced cycling of nitrogen and metals during rapid infiltration: Implications for managed recharge.

We present results from a series of plot-scale field experiments to quantify physical infiltration dynamics and the influence of adding a carbon-rich, permeable reactive barrier (PRB) for the cycling of nitrogen and associated trace metals during rapid infiltration for managed aquifer recharge (MAR). Recent studies suggest that adding a bio-available carbon source to soils can enhance denitrification rates and associated N load reduction during moderate-to-rapid infiltration (≤1 m/day). We examined the potential for N removal during faster infiltration (>1 m/day), through coarse and carbon-poor soils, and how adding a carbon-rich PRB (wood chips) affects subsurface redox conditions and trace metal mobilization.