Article (Scientific journals)
Multi-species measurements of nitrogen isotopic composition reveal the spatial constraints and biological drivers of ammonium attenuation across a highly contaminated groundwater system
Wells, Naomi S.; Hakoun, Vivien; Brouyère, Serge et al.
2016In Water Research, 98, p. 363-375
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Keywords :
ammonium attenuation; groundwater; industrial pollution; nitrate reduction; nitrite reduction; stable isotopes
Abstract :
[en] Groundwater under industrial sites is characterised by heterogeneous chemical mixtures, making it difficult to assess the fate and transport of individual contaminants. Quantifying the in-situ biological removal (attenuation) of nitrogen (N) is particularly difficult due to its reactivity and ubiquity. Here a multi-isotope approach is developed to distinguish N sources and sinks within groundwater affected by complex industrial pollution. Samples were collected from 70 wells across the two aquifers underlying a historic industrial area in Belgium. Below the industrial site the groundwater contained up to 1000 mg Nl-1 ammonium (NH4 +) and 300 mg N l-1 nitrate (NO3-), while downgradient concentrations decreased to ~1 mg l-1 DIN ([DIN] = [NH4+-N] + [NO3--N] + [NO2--N]). Mean δ1534 N-DIN increased from ~2‰ to +20‰ over this flow path, broadly confirming that biological N attenuation drove the measured concentration decrease. Multi-variate analysis of water chemistry identified two distinct NH4+ sources (δ15N-NH4+ from -14‰ and +5‰) within the contaminated zone of both aquifers. Nitrate dual isotopes co-varied (δ15 N: -3‰ - +60‰; δ18O: 0‰ - +50‰) within the range expected for coupled nitrification and denitrification of the identified sources. The fact that δ15N-NO2- values were 50‰ to 20‰ less than δ15N-NH4+ values in 40 the majority of wells confirmed that nitrification controlled N turnover across the site. However, the fact that δ15N-NO2- was greater than δ15N-NH4+ in wells with the highest [NH4+] shows that an autotrophic NO2- reduction pathway (anaerobic NH4+ oxidation or nitrifier-denitrification) drove N attenuation closest to the contaminant plume. This direct empirical evidence that both autotrophic and heterotrophic biogeochemical processes drive N attenuation in contaminated aquifers demonstrates the power of multiple N isotopes to untangle N cycling in highly complex systems.
Disciplines :
Geological, petroleum & mining engineering
Earth sciences & physical geography
Author, co-author :
Wells, Naomi S.;  Helmholtz Centre for Environmental Research - UFZ Leipzig > Department of Catchment Hydrology
Hakoun, Vivien ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Brouyère, Serge  ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Knoeller, Kay;  Helmholtz Centre for Environmental Research – UFZ Leipzig > Department of Catchment Hydrology
Language :
English
Title :
Multi-species measurements of nitrogen isotopic composition reveal the spatial constraints and biological drivers of ammonium attenuation across a highly contaminated groundwater system
Publication date :
July 2016
Journal title :
Water Research
ISSN :
0043-1354
Publisher :
Pergamon Press, Oxford, United Kingdom
Volume :
98
Pages :
363-375
Peer reviewed :
Peer Reviewed verified by ORBi
European Projects :
FP7 - 265063 - ADVOCATE - Advancing Sustainable In Situ Remediation for Contaminated Land and Groundwater
Funders :
DG RDT - Commission Européenne. Direction Générale de la Recherche et de l'Innovation [BE]
CE - Commission Européenne [BE]
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