Nitrate transformation and immobilization in particulate organic matter incubations

Influence of redox, iron and (a)biotic conditions

Fiona R. Kizewski, Jason Philip Kaye, Carmen Enid Martínez

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Article numbere0218752
JournalPloS one
Volume14
Issue number7
DOIs
StatePublished - Jan 1 2019

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Particulate Matter
yard waste composts
Immobilization
Nitrates
Biological materials
Oxidation-Reduction
dissolved organic nitrogen
Iron
electrons
nitrates
iron
Electron sources
anaerobic conditions
denitrification
Nitrogen
Denitrification
soil organic matter
oximes
Electrons
rain intensity

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

Cite this

@article{7647e2baeaae41a2b2e34a47b7ef6009,
title = "Nitrate transformation and immobilization in particulate organic matter incubations: Influence of redox, iron and (a)biotic conditions",
abstract = "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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Nitrate transformation and immobilization in particulate organic matter incubations : Influence of redox, iron and (a)biotic conditions. / Kizewski, Fiona R.; Kaye, Jason Philip; Martínez, Carmen Enid.

In: PloS one, Vol. 14, No. 7, e0218752, 01.01.2019.

Research output: Contribution to journalArticle

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 Philip

AU - Martínez, Carmen Enid

PY - 2019/1/1

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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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