Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments

Using 15N stable isotope as a tracer to quantify N transformation rates in isotope-enrichment experiments improves understanding of the N cycle in various ecosystems. However, measuring 15N-nitrate (15NO3−) in small volumes of water for these experiments is a major challenge due to the inconvenience...

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Autores principales:	Xianbiao Lin, Kaijun Lu, Amber K. Hardison, Zhanfei Liu, Xin Xu, Dengzhou Gao, Jun Gong, Wayne S. Gardner
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	REOX/MIMS 15NO3− Gross nitrification Gross NO3− immobilization Isotope dilution method Ecology QH540-549.5
Acceso en línea:	https://doaj.org/article/b563f395770146ff884966fb2f5cc8e0
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spelling	oai:doaj.org-article:b563f395770146ff884966fb2f5cc8e02021-12-01T04:50:10ZMembrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments1470-160X10.1016/j.ecolind.2021.107639https://doaj.org/article/b563f395770146ff884966fb2f5cc8e02021-07-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S1470160X21003046https://doaj.org/toc/1470-160XUsing 15N stable isotope as a tracer to quantify N transformation rates in isotope-enrichment experiments improves understanding of the N cycle in various ecosystems. However, measuring 15N-nitrate (15NO3−) in small volumes of water for these experiments is a major challenge due to the inconvenience of preparing samples by traditional techniques. We developed a “REOX/MIMS” method by applying membrane inlet mass spectrometry (MIMS) to determining 15NO3− concentrations in a small volumes of water from isotope-enrichment experiments after converting the dissolved inorganic N to N2. The nitrates (NO3− + NO2−) were reduced to NH4+ with zinc powder, and the ammonium (NH4+) was then oxidized to N2 by hypobromite iodine solution. The resulting 29N2 and 30N2 were measured via MIMS. This optimized protocol provides a sensitive (~0.1 μM) and precise (relative standard deviation = 0.1–4.37%) approach to quantify 15NO3− concentrations (0.1–500 µM) in water samples over a wide range of salinities (0–35‰) and in 2 M KCl solution with excellent calibration curves (R2 ≥ 0.9996, p < 0.0001). The method was combined with 15NO3− isotope-enrichment incubation experiments to measure gross nitrification and gross NO3− immobilization rates in various ecosystems. It was rapid, accurate, and cost-effective. Future applications of this efficient approach will inform scientists, modelers and decision makers about mechanisms, sources, fates, and effects of NO3− delivered to or produced in numerous aquatic and terrestrial ecosystems.Xianbiao LinKaijun LuAmber K. HardisonZhanfei LiuXin XuDengzhou GaoJun GongWayne S. GardnerElsevierarticleREOX/MIMS15NO3−Gross nitrificationGross NO3− immobilizationIsotope dilution methodEcologyQH540-549.5ENEcological Indicators, Vol 126, Iss , Pp 107639- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	REOX/MIMS 15NO3− Gross nitrification Gross NO3− immobilization Isotope dilution method Ecology QH540-549.5
spellingShingle	REOX/MIMS 15NO3− Gross nitrification Gross NO3− immobilization Isotope dilution method Ecology QH540-549.5 Xianbiao Lin Kaijun Lu Amber K. Hardison Zhanfei Liu Xin Xu Dengzhou Gao Jun Gong Wayne S. Gardner Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
description	Using 15N stable isotope as a tracer to quantify N transformation rates in isotope-enrichment experiments improves understanding of the N cycle in various ecosystems. However, measuring 15N-nitrate (15NO3−) in small volumes of water for these experiments is a major challenge due to the inconvenience of preparing samples by traditional techniques. We developed a “REOX/MIMS” method by applying membrane inlet mass spectrometry (MIMS) to determining 15NO3− concentrations in a small volumes of water from isotope-enrichment experiments after converting the dissolved inorganic N to N2. The nitrates (NO3− + NO2−) were reduced to NH4+ with zinc powder, and the ammonium (NH4+) was then oxidized to N2 by hypobromite iodine solution. The resulting 29N2 and 30N2 were measured via MIMS. This optimized protocol provides a sensitive (~0.1 μM) and precise (relative standard deviation = 0.1–4.37%) approach to quantify 15NO3− concentrations (0.1–500 µM) in water samples over a wide range of salinities (0–35‰) and in 2 M KCl solution with excellent calibration curves (R2 ≥ 0.9996, p < 0.0001). The method was combined with 15NO3− isotope-enrichment incubation experiments to measure gross nitrification and gross NO3− immobilization rates in various ecosystems. It was rapid, accurate, and cost-effective. Future applications of this efficient approach will inform scientists, modelers and decision makers about mechanisms, sources, fates, and effects of NO3− delivered to or produced in numerous aquatic and terrestrial ecosystems.
format	article
author	Xianbiao Lin Kaijun Lu Amber K. Hardison Zhanfei Liu Xin Xu Dengzhou Gao Jun Gong Wayne S. Gardner
author_facet	Xianbiao Lin Kaijun Lu Amber K. Hardison Zhanfei Liu Xin Xu Dengzhou Gao Jun Gong Wayne S. Gardner
author_sort	Xianbiao Lin
title	Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
title_short	Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
title_full	Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
title_fullStr	Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
title_full_unstemmed	Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments
title_sort	membrane inlet mass spectrometry method (reox/mims) to measure 15n-nitrate in isotope-enrichment experiments
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/b563f395770146ff884966fb2f5cc8e0
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Membrane inlet mass spectrometry method (REOX/MIMS) to measure 15N-nitrate in isotope-enrichment experiments

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