TY - JOUR
T1 - Nitrate transformation and immobilization in particulate organic matter incubations
T2 - Influence of redox, iron and (a)biotic conditions
AU - Kizewski, Fiona R.
AU - Kaye, Jason P.
AU - Martínez, Carmen Enid
N1 - Funding Information:
This project was funded by the NSF (Grant No. 0816668) and by the Agriculture and Food Research Initiative (AFRI, grant no. 2016-67019-25265/project accession no. 1009565) from the USDA National Institute of Food and Agriculture to CEM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors thank Dr. Benesi and Dr. Hatzakis for their assistance with NMR data collection and Dr. Govere for his assistance with DOC analyses.
Publisher Copyright:
© 2019 Kizewski et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PY - 2019/6/1
Y1 - 2019/6/1
N2 - Nitrate can be reduced to other N inorganic species via denitrification and incorporated into organic matter by immobilization; however, the effect of biotic/abiotic and redox condition on immobilization and denitrification processes from a single system are not well documented. We hypothesize nitrate (NO3 -) transformation pathways leading to the formation of dissolved- and solid-phase organic N are predominantly controlled by abiotic reactions, but the formation of soluble inorganic N species is controlled by redox condition. In this study, organic matter in the form of leaf compost (LC) was spiked with 15NO3 - and incubated under oxic/anoxic and biotic/abiotic conditions at pH 6.5. We seek to understand how variations in environmental conditions impact NO3 - transformation pathways through laboratory incubations. We find production of NH4 + is predominantly controlled by redox whereas NO3 - conversion to dissolved organic nitrogen (DON) and immobilization in solid-phase N are predominantly controlled by abiotic processes. Twenty % of added 15N-NO3 - was incorporated into DON under oxic conditions, with abiotic processes accounting for 85% of the overall incorporation. Nitrogen immobilization processes resulted in N concentrations of 4.1–6.6 μg N (g leaf compost)-1, with abiotic processes accounting for 100% and 66% of the overall (biotic+abiotic) N immobilization under anoxic and oxic conditions, respectively. 15N-NMR spectroscopy suggests 15NO3 - was immobilized into amide/aminoquinones and nitro/ oxime under anoxic conditions. A fraction of the NH4 + was produced abiotically under anoxic conditions (~10% of the total NH4 + production) although biotic organic N mineralization contributed to most of NH4 + production. Our results also indicate Fe(II) did not act as an electron source in biotic-oxic incubations; however, Fe(II) provided electrons for NO3 - reduction in biotic-anoxic incubations although it was not the sole electron source. It is clear that, under the experimental conditions of this investigation, abiotic and redox processes play important roles in NO3 - transformations. As climatic conditions change (e.g., frequency/intensity of rainfall), abiotic reactions that shift transformation pathways and N species concentrations from those controlled by biota might become more prevalent.
AB - Nitrate can be reduced to other N inorganic species via denitrification and incorporated into organic matter by immobilization; however, the effect of biotic/abiotic and redox condition on immobilization and denitrification processes from a single system are not well documented. We hypothesize nitrate (NO3 -) transformation pathways leading to the formation of dissolved- and solid-phase organic N are predominantly controlled by abiotic reactions, but the formation of soluble inorganic N species is controlled by redox condition. In this study, organic matter in the form of leaf compost (LC) was spiked with 15NO3 - and incubated under oxic/anoxic and biotic/abiotic conditions at pH 6.5. We seek to understand how variations in environmental conditions impact NO3 - transformation pathways through laboratory incubations. We find production of NH4 + is predominantly controlled by redox whereas NO3 - conversion to dissolved organic nitrogen (DON) and immobilization in solid-phase N are predominantly controlled by abiotic processes. Twenty % of added 15N-NO3 - was incorporated into DON under oxic conditions, with abiotic processes accounting for 85% of the overall incorporation. Nitrogen immobilization processes resulted in N concentrations of 4.1–6.6 μg N (g leaf compost)-1, with abiotic processes accounting for 100% and 66% of the overall (biotic+abiotic) N immobilization under anoxic and oxic conditions, respectively. 15N-NMR spectroscopy suggests 15NO3 - was immobilized into amide/aminoquinones and nitro/ oxime under anoxic conditions. A fraction of the NH4 + was produced abiotically under anoxic conditions (~10% of the total NH4 + production) although biotic organic N mineralization contributed to most of NH4 + production. Our results also indicate Fe(II) did not act as an electron source in biotic-oxic incubations; however, Fe(II) provided electrons for NO3 - reduction in biotic-anoxic incubations although it was not the sole electron source. It is clear that, under the experimental conditions of this investigation, abiotic and redox processes play important roles in NO3 - transformations. As climatic conditions change (e.g., frequency/intensity of rainfall), abiotic reactions that shift transformation pathways and N species concentrations from those controlled by biota might become more prevalent.
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U2 - 10.1371/journal.pone.0218752
DO - 10.1371/journal.pone.0218752
M3 - Article
C2 - 31276538
AN - SCOPUS:85069268263
VL - 14
JO - PLoS One
JF - PLoS One
SN - 1932-6203
IS - 7
M1 - e0218752
ER -