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Hydrology, geochemistry, and microbiology data from meter-scale infiltration experiments exploring the impact of a woodchip soil amendment on nitrate removal during infiltration

Citation

Beganskas, Sarah et al. (2018), Hydrology, geochemistry, and microbiology data from meter-scale infiltration experiments exploring the impact of a woodchip soil amendment on nitrate removal during infiltration, v2, UC Santa Cruz Dash, Dataset, https://doi.org/10.7291/D14D4H

Abstract

We present results from field experiments linking hydrology, geochemistry, and microbiology during infiltration at a field site that is used for managed aquifer recharge (MAR). These experiments measured how a horizontal permeable reactive barrier (PRB) made of woodchips impacted subsurface nitrate removal and microbial ecology. Concentrations of dissolved organic carbon consistently increased in infiltrating water below the PRB, but not in un-amended native soil. The average nitrate removal rate in soils below the PRB was 1.5 g/m2/day NO3-N, despite rapid infiltration (up to 1.9 m/d) and a short fluid residence time within the woodchips (≤6 h). In contrast, 0.09 g/m2/day NO3-N was removed on average in native soil. Residual nitrate in infiltrating water below the PRB was enriched in δ15N and δ18O, with low and variable isotopic enrichment factors that are consistent with denitrification during rapid infiltration. Many putative denitrifying bacteria were significantly enhanced in the soil below a PRB; Methylotenera mobilis and genera Microbacterium, Polaromonas, and Novosphingobium had log2 fold-changes of +4.9, +5.6, +7.2, and +11.8, respectively. These bacteria were present before infiltration and were not enhanced in native soil. It appears that the woodchip PRB contributed to favorable conditions in the underlying soil for enhanced nitrate removal, quantitatively shifting soil microbial ecology. These results suggest that using a horizontal PRB could improve water quality during rapid infiltration for MAR.

Funding

UC Water Security and Sustainability Research Initiative, Award: UCOP Grant # 13941

Gordon and Betty Moore Foundation, Award: GBMF5595

U.S. Environmental Protection Agency, Award: Grant # 83599501

National Science Foundation Graduate Research Fellowship,

The Recharge Initiative,