Water Research, 01 October 2018, Vol.142, pp.373-382
Nitrogen fate and transport through contaminated groundwater systems, where N is both ubiquitous and commonly limits pollutant attenuation, must be re-evaluated given evidence for new potential microbial N pathways. We addressed this by measuring the isotopic composition of dissolved inorganic N (DIN = NH , NO , and NO ) and N functional gene abundances ( , , , ) from 20 to 38 wells across an NH , hydrocarbon, and SO contaminated aquifer. In-situ N attenuation was confirmed on three sampling dates (0, +6, +12 months) by the decreased [DIN] (4300 - 40 μM) and increased δ N-DIN (5‰–33‰) over the flow path. However, the assumption of negligible N attenuation within the plume was complicated by the presence of alternative electron acceptors (SO , Fe ), both oxidizing and reducing functional genes, and N oxides within this anoxic zone. Active plume N cycling was corroborated using an NO dual isotope based model, which found the fastest (∼10 day) NO turnover within the N and electron donor rich central plume. Findings suggest that N cycling is not always O limited within chemically complex contaminated aquifers, though this cycling may recycle the N species rather than attenuate N.
Contaminated Groundwater ; Stable Isotopes ; Nitrite ; Chemolithotrophic N Cycling ; Biodegradation ; Nitrate Dual Isotopes ; Engineering
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