Articles | Volume 15, issue 22
https://doi.org/10.5194/bg-15-7025-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-15-7025-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
22 Nov 2018
Research article |
| 22 Nov 2018
| 22 Nov 2018
Export flux of unprocessed atmospheric nitrate from temperate forested catchments: a possible new index for nitrogen saturation
Fumiko Nakagawa
Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Yusuke Obata
Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Kenta Ando
Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Naoyuki Yamashita
Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata-shi, Niigata 950-2144, Japan
present address: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan
Tatsuyoshi Saito
Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata-shi, Niigata 950-2144, Japan
present address: Niigata Prefectural Institute of Public Health and Environmental Sciences, 314-1 Sowa, Nishi-ku, Niigata-Shi, Niigata 950-2144,
Japan
Shigeki Uchiyama
Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata-shi, Niigata 950-2144, Japan
present address: Ministry of Agriculture, Forestry and Fisheries, 1-2-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8950, Japan
Masayuki Morohashi
Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata-shi, Niigata 950-2144, Japan
Hiroyuki Sase
Asia Center for Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata-shi, Niigata 950-2144, Japan
Related authors
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Masaaki Chiwa, Tamao Kasahara, and Ken'ichi Shinozuka
Biogeosciences, 20, 753–766, https://doi.org/10.5194/bg-20-753-2023, https://doi.org/10.5194/bg-20-753-2023, 2023
Short summary
Short summary
By monitoring the concentration and Δ17O of stream nitrate in three forested streams, the new nitrogen saturation index of forested catchments (Matm/Datm ratio) was estimated. We found that (1) the unprocessed atmospheric nitrate in our studied forested stream (FK1 catchment) was the highest ever reported in forested streams; (2) the Matm/Datm ratio can be used as a robust index for evaluating nitrogen saturation in forested catchments as the Matm/Datm ratio is independent of the precipitation.
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Hiroyuki Sase, Masayuki Morohashi, and Hiroki Yotsuyanagi
Biogeosciences, 19, 3247–3261, https://doi.org/10.5194/bg-19-3247-2022, https://doi.org/10.5194/bg-19-3247-2022, 2022
Short summary
Short summary
Excessive leaching of nitrate from forested catchments during storm events degrades water quality and causes eutrophication in downstream areas. Thus, tracing the source of nitrate increase during storm events in forested streams is important for sustainable forest management. Based on the isotopic compositions of stream nitrate, including Δ17O, this study clarifies that the source of stream nitrate increase during storm events was soil nitrate in the riparian zone.
Hao Xu, Urumu Tsunogai, Fumiko Nakagawa, Keiichi Sato, and Hiroshi Tanimoto
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-1099, https://doi.org/10.5194/acp-2021-1099, 2022
Revised manuscript not accepted
Short summary
Short summary
Using triple oxygen isotopic composition (Δ17O) of ozone as a new tracer, we estimated the absolute concentrations of stratospheric ozone supplied through stratosphere-troposphere transport in the troposphere. We observed the diurnal variations in the Δ17O of ozone, which could have affected studies (field measurements, atmospheric modeling) using Δ17O to constrain atmospheric chemical paths. Our study provides an important basis for a better understanding of ozone behavior in the troposphere.
David M. Nelson, Urumu Tsunogai, Dong Ding, Takuya Ohyama, Daisuke D. Komatsu, Fumiko Nakagawa, Izumi Noguchi, and Takashi Yamaguchi
Atmos. Chem. Phys., 18, 6381–6392, https://doi.org/10.5194/acp-18-6381-2018, https://doi.org/10.5194/acp-18-6381-2018, 2018
Short summary
Short summary
Atmospheric nitrate may be produced locally and/or come from upwind regions. To address this issue we measured oxygen and nitrogen isotopes of wet and dry nitrate deposition at nearby urban and rural sites. Our results suggest that, relative to nitrate in wet deposition in urban environments and wet and dry deposition in rural environments, nitrate in dry deposition in urban environments results from local NOx emissions more so than wet deposition, which is transported longer distances.
Urumu Tsunogai, Takanori Miyauchi, Takuya Ohyama, Daisuke D. Komatsu, Fumiko Nakagawa, Yusuke Obata, Keiichi Sato, and Tsuyoshi Ohizumi
Biogeosciences, 13, 3441–3459, https://doi.org/10.5194/bg-13-3441-2016, https://doi.org/10.5194/bg-13-3441-2016, 2016
Short summary
Short summary
We quantified the influence of changes in land use and population density between each catchment area on the fate of atmospheric nitrate, by determining the areal distribution and seasonal variation in stable isotopic compositions of nitrate for more than 30 streams within a same watershed. We found that the absolute concentrations of atmospheric nitrate were almost the same between the streams irrespective to the changes in land use and population density.
Weitian Ding, Urumu Tsunogai, and Fumiko Nakagawa
Biogeosciences, 21, 4717–4722, https://doi.org/10.5194/bg-21-4717-2024, https://doi.org/10.5194/bg-21-4717-2024, 2024
Short summary
Short summary
Past studies have used the Δ17O of stream nitrate to estimate the gross nitrification rates (GNRs) in each forested catchment by approximating the Δ17O value of soil nitrate to be equal to that of stream nitrate. Based on inference and calculation of measured data, we found that this approximation resulted in an overestimated GNR. Therefore, it is essential to clarify and verify the Δ17O NO3− values in forested soils and streams before applying the Δ17O values of stream NO3− to GNR estimation.
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Masaaki Chiwa, Tamao Kasahara, and Ken'ichi Shinozuka
Biogeosciences, 20, 753–766, https://doi.org/10.5194/bg-20-753-2023, https://doi.org/10.5194/bg-20-753-2023, 2023
Short summary
Short summary
By monitoring the concentration and Δ17O of stream nitrate in three forested streams, the new nitrogen saturation index of forested catchments (Matm/Datm ratio) was estimated. We found that (1) the unprocessed atmospheric nitrate in our studied forested stream (FK1 catchment) was the highest ever reported in forested streams; (2) the Matm/Datm ratio can be used as a robust index for evaluating nitrogen saturation in forested catchments as the Matm/Datm ratio is independent of the precipitation.
Weitian Ding, Urumu Tsunogai, and Fumiko Nakagawa
Biogeosciences Discuss., https://doi.org/10.5194/bg-2022-236, https://doi.org/10.5194/bg-2022-236, 2023
Revised manuscript not accepted
Short summary
Short summary
Past studies used the Δ17O of stream nitrate to estimate GNR in each forested catchment. However, the GNR estimated from the Δ17O of stream nitrate using the equations was more than six times the actual GNR in our simulated calculation for a forested catchment. As a result, it must be essential to clarify/verify the distribution of the Δ17O values of NO3− in forested soils before applying the Δ17O values of stream NO3− to estimate GNR.
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Hiroyuki Sase, Masayuki Morohashi, and Hiroki Yotsuyanagi
Biogeosciences, 19, 3247–3261, https://doi.org/10.5194/bg-19-3247-2022, https://doi.org/10.5194/bg-19-3247-2022, 2022
Short summary
Short summary
Excessive leaching of nitrate from forested catchments during storm events degrades water quality and causes eutrophication in downstream areas. Thus, tracing the source of nitrate increase during storm events in forested streams is important for sustainable forest management. Based on the isotopic compositions of stream nitrate, including Δ17O, this study clarifies that the source of stream nitrate increase during storm events was soil nitrate in the riparian zone.
Hao Xu, Urumu Tsunogai, Fumiko Nakagawa, Keiichi Sato, and Hiroshi Tanimoto
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-1099, https://doi.org/10.5194/acp-2021-1099, 2022
Revised manuscript not accepted
Short summary
Short summary
Using triple oxygen isotopic composition (Δ17O) of ozone as a new tracer, we estimated the absolute concentrations of stratospheric ozone supplied through stratosphere-troposphere transport in the troposphere. We observed the diurnal variations in the Δ17O of ozone, which could have affected studies (field measurements, atmospheric modeling) using Δ17O to constrain atmospheric chemical paths. Our study provides an important basis for a better understanding of ozone behavior in the troposphere.
David M. Nelson, Urumu Tsunogai, Dong Ding, Takuya Ohyama, Daisuke D. Komatsu, Fumiko Nakagawa, Izumi Noguchi, and Takashi Yamaguchi
Atmos. Chem. Phys., 18, 6381–6392, https://doi.org/10.5194/acp-18-6381-2018, https://doi.org/10.5194/acp-18-6381-2018, 2018
Short summary
Short summary
Atmospheric nitrate may be produced locally and/or come from upwind regions. To address this issue we measured oxygen and nitrogen isotopes of wet and dry nitrate deposition at nearby urban and rural sites. Our results suggest that, relative to nitrate in wet deposition in urban environments and wet and dry deposition in rural environments, nitrate in dry deposition in urban environments results from local NOx emissions more so than wet deposition, which is transported longer distances.
Urumu Tsunogai, Takanori Miyauchi, Takuya Ohyama, Daisuke D. Komatsu, Fumiko Nakagawa, Yusuke Obata, Keiichi Sato, and Tsuyoshi Ohizumi
Biogeosciences, 13, 3441–3459, https://doi.org/10.5194/bg-13-3441-2016, https://doi.org/10.5194/bg-13-3441-2016, 2016
Short summary
Short summary
We quantified the influence of changes in land use and population density between each catchment area on the fate of atmospheric nitrate, by determining the areal distribution and seasonal variation in stable isotopic compositions of nitrate for more than 30 streams within a same watershed. We found that the absolute concentrations of atmospheric nitrate were almost the same between the streams irrespective to the changes in land use and population density.
U. Tsunogai, D. D. Komatsu, T. Ohyama, A. Suzuki, F. Nakagawa, I. Noguchi, K. Takagi, M. Nomura, K. Fukuzawa, and H. Shibata
Biogeosciences, 11, 5411–5424, https://doi.org/10.5194/bg-11-5411-2014, https://doi.org/10.5194/bg-11-5411-2014, 2014
F. Nakagawa, A. Suzuki, S. Daita, T. Ohyama, D. D. Komatsu, and U. Tsunogai
Biogeosciences, 10, 3547–3558, https://doi.org/10.5194/bg-10-3547-2013, https://doi.org/10.5194/bg-10-3547-2013, 2013
Related subject area
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Elise D. Rivett, Wenjuan Ma, Nathaniel E. Ostrom, and Eric L. Hegg
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Many different processes produce nitrous oxide (N2O), a potent greenhouse gas. Measuring the ratio of heavy and light nitrogen isotopes (15N/14N) for the non-exchangeable central and outer N atoms of N2O helps to distinguish sources of N2O. To accurately calculate the position-specific isotopic preference, we developed an expansion of the widely used Rayleigh model. Application of our new model to simulated and experimental data demonstrates its improved accuracy for analyzing N2O synthesis.
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Assessing the net carbon (C) budget of the Amazon entails considering the magnitude and timing of C absorption and losses through respiration (transit time of C). Radiocarbon-based estimates of the transit time of C in the Amazon Tall Tower Observatory (ATTO) suggest a doubling of the transit time from 6 ± 2 years and 18 ± 5 years (October 2019 and December 2021, respectively). This variability indicates that only a fraction of newly fixed C can be stored for decades or longer.
Nestor Gaviria-Lugo, Charlotte Läuchli, Hella Wittmann, Anne Bernhardt, Patrick Frings, Mahyar Mohtadi, Oliver Rach, and Dirk Sachse
Biogeosciences, 20, 4433–4453, https://doi.org/10.5194/bg-20-4433-2023, https://doi.org/10.5194/bg-20-4433-2023, 2023
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We analyzed how leaf wax hydrogen isotopes in continental and marine sediments respond to climate along one of the strongest aridity gradients in the world, from hyperarid to humid, along Chile. We found that under extreme aridity, the relationship between hydrogen isotopes in waxes and climate is non-linear, suggesting that we should be careful when reconstructing past hydrological changes using leaf wax hydrogen isotopes so as to avoid overestimating how much the climate has changed.
Ralf Conrad and Peter Claus
Biogeosciences, 20, 3625–3635, https://doi.org/10.5194/bg-20-3625-2023, https://doi.org/10.5194/bg-20-3625-2023, 2023
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Alessandro Zanchetta, Linda M. J. Kooijmans, Steven van Heuven, Andrea Scifo, Hubertus A. Scheeren, Ivan Mammarella, Ute Karstens, Jin Ma, Maarten Krol, and Huilin Chen
Biogeosciences, 20, 3539–3553, https://doi.org/10.5194/bg-20-3539-2023, https://doi.org/10.5194/bg-20-3539-2023, 2023
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Carbonyl sulfide (COS) has been suggested as a tool to estimate carbon dioxide (CO2) uptake by plants during photosynthesis. However, understanding its sources and sinks is critical to preventing biases in this estimate. Combining observations and models, this study proves that regional sources occasionally influence the measurements at the 60 m tall Lutjewad tower (1 m a.s.l.; 53°24′ N, 6°21′ E) in the Netherlands. Moreover, it estimates nighttime COS fluxes to be −3.0 ± 2.6 pmol m−2 s−1.
Joel T. Bostic, David M. Nelson, and Keith N. Eshleman
Biogeosciences, 20, 2485–2498, https://doi.org/10.5194/bg-20-2485-2023, https://doi.org/10.5194/bg-20-2485-2023, 2023
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Land-use changes can affect water quality. We used tracers of pollution sources and water flow paths to show that an urban watershed exports variable sources during storm events relative to a less developed watershed. Our results imply that changing precipitation patterns combined with increasing urbanization may alter sources of pollution in the future.
Robin Havas, Christophe Thomazo, Miguel Iniesto, Didier Jézéquel, David Moreira, Rosaluz Tavera, Jeanne Caumartin, Elodie Muller, Purificación López-García, and Karim Benzerara
Biogeosciences, 20, 2405–2424, https://doi.org/10.5194/bg-20-2405-2023, https://doi.org/10.5194/bg-20-2405-2023, 2023
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Dissolved organic carbon (DOC) is a reservoir of prime importance in the C cycle of both continental and marine systems. It has also been suggested to influence the past Earth climate but is still poorly characterized in ancient-Earth-like environments. In this paper we show how DOC analyses from modern redox-stratified lakes can evidence specific metabolic reactions and environmental factors and how these can help us to interpret the C cycle of specific periods in the Earth's past.
Robin Havas, Christophe Thomazo, Miguel Iniesto, Didier Jézéquel, David Moreira, Rosaluz Tavera, Jeanne Caumartin, Elodie Muller, Purificación López-García, and Karim Benzerara
Biogeosciences, 20, 2347–2367, https://doi.org/10.5194/bg-20-2347-2023, https://doi.org/10.5194/bg-20-2347-2023, 2023
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We describe the C cycle of four modern stratified water bodies from Mexico, a necessary step to better understand the C cycle of primitive-Earth-like environments, which were dominated by these kinds of conditions. We highlight the importance of local external factors on the C cycle of these systems. Notably, they influence the sensitivity of the carbonate record to environmental changes. We also show the strong C-cycle variability among these lakes and their organic C sediment record.
Yifan Ma, Kuanbo Zhou, Weifang Chen, Junhui Chen, Jin-Yu Terence Yang, and Minhan Dai
Biogeosciences, 20, 2013–2030, https://doi.org/10.5194/bg-20-2013-2023, https://doi.org/10.5194/bg-20-2013-2023, 2023
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We distinguished particulate organic carbon (POC) export fluxes out of the nutrient-depleted layer (NDL) and the euphotic zone. The amount of POC export flux at the NDL base suggests that the NDL could be a hotspot of particle export. The substantial POC export flux at the NDL base challenges traditional concepts that the NDL was limited in terms of POC export. The dominant nutrient source for POC export fluxes should be subsurface nutrients, which was determined by 15N isotopic mass balance.
Clémence Paul, Clément Piel, Joana Sauze, Nicolas Pasquier, Frédéric Prié, Sébastien Devidal, Roxanne Jacob, Arnaud Dapoigny, Olivier Jossoud, Alexandru Milcu, and Amaëlle Landais
Biogeosciences, 20, 1047–1062, https://doi.org/10.5194/bg-20-1047-2023, https://doi.org/10.5194/bg-20-1047-2023, 2023
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To improve the interpretation of the δ18Oatm and Δ17O of O2 in air bubbles in ice cores, we need to better quantify the oxygen fractionation coefficients associated with biological processes. We performed a simplified analogue of the terrestrial biosphere in a closed chamber. We found a respiration fractionation in agreement with the previous estimates at the microorganism scale, and a terrestrial photosynthetic fractionation was found. This has an impact on the estimation of the Dole effect.
Adam Francis, Raja S. Ganeshram, Robyn E. Tuerena, Robert G. M. Spencer, Robert M. Holmes, Jennifer A. Rogers, and Claire Mahaffey
Biogeosciences, 20, 365–382, https://doi.org/10.5194/bg-20-365-2023, https://doi.org/10.5194/bg-20-365-2023, 2023
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Climate change is causing extensive permafrost degradation and nutrient releases into rivers with great ecological impacts on the Arctic Ocean. We focused on nitrogen (N) release from this degradation and associated cycling using N isotopes, an understudied area. Many N species are released at degradation sites with exchanges between species. N inputs from permafrost degradation and seasonal river N trends were identified using isotopes, helping to predict climate change impacts.
Mohamed Ayache, Jean-Claude Dutay, Kazuyo Tachikawa, Thomas Arsouze, and Catherine Jeandel
Biogeosciences, 20, 205–227, https://doi.org/10.5194/bg-20-205-2023, https://doi.org/10.5194/bg-20-205-2023, 2023
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The neodymium (Nd) is one of the most useful tracers to fingerprint water mass provenance. However, the use of Nd is hampered by the lack of adequate quantification of the external sources. Here, we present the first simulation of dissolved Nd concentration and Nd isotopic composition in the Mediterranean Sea using a high-resolution model. We aim to better understand how the various external sources affect the Nd cycle and particularly assess how it is impacted by atmospheric inputs.
Marta Santos-Garcia, Raja S. Ganeshram, Robyn E. Tuerena, Margot C. F. Debyser, Katrine Husum, Philipp Assmy, and Haakon Hop
Biogeosciences, 19, 5973–6002, https://doi.org/10.5194/bg-19-5973-2022, https://doi.org/10.5194/bg-19-5973-2022, 2022
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Terrestrial sources of nitrate are important contributors to the nutrient pool in the fjords of Kongsfjorden and Rijpfjorden in Svalbard during the summer, and they sustain most of the fjord primary productivity. Ongoing tidewater glacier retreat is postulated to favour light limitation and less dynamic circulation in fjords. This is suggested to encourage the export of nutrients to the middle and outer part of the fjord system, which may enhance primary production within and in offshore areas.
Marlene Dordoni, Michael Seewald, Karsten Rinke, Kurt Friese, Robert van Geldern, Jakob Schmidmeier, and Johannes A. C. Barth
Biogeosciences, 19, 5343–5355, https://doi.org/10.5194/bg-19-5343-2022, https://doi.org/10.5194/bg-19-5343-2022, 2022
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Organic matter (OM) turnover into dissolved inorganic carbon (DIC) was investigated by means of carbon isotope mass balances in Germany's largest water reservoir. This includes a metalimnetic oxygen minimum (MOM). Autochthonous particulate organic carbon (POC) was the main contributor to DIC, with rates that were highest for the MOM. Generally low turnover rates outline the environmental fragility of this water body in the case that OM loads increase due to storm events or land use changes.
Frédérique M. S. A. Kirkels, Hugo J. de Boer, Paulina Concha Hernández, Chris R. T. Martes, Marcel T. J. van der Meer, Sayak Basu, Muhammed O. Usman, and Francien Peterse
Biogeosciences, 19, 4107–4127, https://doi.org/10.5194/bg-19-4107-2022, https://doi.org/10.5194/bg-19-4107-2022, 2022
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The distinct carbon isotopic values of C3 and C4 plants are widely used to reconstruct past hydroclimate, where more C3 plants reflect wetter and C4 plants drier conditions. Here we examine the impact of regional hydroclimatic conditions on plant isotopic values in the Godavari River basin, India. We find that it is crucial to identify regional plant isotopic values and consider drought stress, which introduces a bias in C3 / C4 plant estimates and associated hydroclimate reconstructions.
Mhlangabezi Mdutyana, Tanya Marshall, Xin Sun, Jessica M. Burger, Sandy J. Thomalla, Bess B. Ward, and Sarah E. Fawcett
Biogeosciences, 19, 3425–3444, https://doi.org/10.5194/bg-19-3425-2022, https://doi.org/10.5194/bg-19-3425-2022, 2022
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Nitrite-oxidizing bacteria in the winter Southern Ocean show a high affinity for nitrite but require a minimum (i.e., "threshold") concentration before they increase their rates of nitrite oxidation significantly. The classic Michaelis–Menten model thus cannot be used to derive the kinetic parameters, so a modified equation was employed that also yields the threshold nitrite concentration. Dissolved iron availability may play an important role in limiting nitrite oxidation.
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Hiroyuki Sase, Masayuki Morohashi, and Hiroki Yotsuyanagi
Biogeosciences, 19, 3247–3261, https://doi.org/10.5194/bg-19-3247-2022, https://doi.org/10.5194/bg-19-3247-2022, 2022
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Excessive leaching of nitrate from forested catchments during storm events degrades water quality and causes eutrophication in downstream areas. Thus, tracing the source of nitrate increase during storm events in forested streams is important for sustainable forest management. Based on the isotopic compositions of stream nitrate, including Δ17O, this study clarifies that the source of stream nitrate increase during storm events was soil nitrate in the riparian zone.
Nicolas Séon, Romain Amiot, Guillaume Suan, Christophe Lécuyer, François Fourel, Fabien Demaret, Arnauld Vinçon-Laugier, Sylvain Charbonnier, and Peggy Vincent
Biogeosciences, 19, 2671–2681, https://doi.org/10.5194/bg-19-2671-2022, https://doi.org/10.5194/bg-19-2671-2022, 2022
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We analysed the oxygen isotope composition of bones and teeth of four marine species possessing regional heterothermies. We observed a consistent link between oxygen isotope composition and temperature heterogeneities recorded by classical methods. This opens up new perspectives on the determination of the thermoregulatory strategies of extant marine vertebrates where conventional methods are difficult to apply, but also allows us to investigate thermophysiologies of extinct vertebrates.
Yuwei Liu, Guofeng Zhu, Zhuanxia Zhang, Zhigang Sun, Leilei Yong, Liyuan Sang, Lei Wang, and Kailiang Zhao
Biogeosciences, 19, 877–889, https://doi.org/10.5194/bg-19-877-2022, https://doi.org/10.5194/bg-19-877-2022, 2022
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We took the water cycle process of soil–plant–atmospheric precipitation as the research objective. In the water cycle of soil–plant–atmospheric precipitation, precipitation plays the main controlling role. The main source of replenishment for alpine meadow plants is precipitation and alpine meltwater; the main source of replenishment for forest plants is soil water; and the plants in the arid foothills mainly use groundwater.
Roberto Velázquez-Ochoa, María Julia Ochoa-Izaguirre, and Martín Federico Soto-Jiménez
Biogeosciences, 19, 1–27, https://doi.org/10.5194/bg-19-1-2022, https://doi.org/10.5194/bg-19-1-2022, 2022
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Our research is the first approximation to understand the δ13C macroalgal variability in one of the most diverse marine ecosystems in the world, the Gulf of California. The life-form is the principal cause of δ13C macroalgal variability, mainly taxonomy. However, changes in habitat characteristics and environmental conditions also influence the δ13C macroalgal variability. The δ13C macroalgae is indicative of carbon concentration mechanisms and isotope discrimination during carbon assimilation.
Raquel F. Flynn, Thomas G. Bornman, Jessica M. Burger, Shantelle Smith, Kurt A. M. Spence, and Sarah E. Fawcett
Biogeosciences, 18, 6031–6059, https://doi.org/10.5194/bg-18-6031-2021, https://doi.org/10.5194/bg-18-6031-2021, 2021
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Biological activity in the shallow Weddell Sea affects the biogeochemistry of recently formed deep waters. To investigate the drivers of carbon and nutrient export, we measured rates of primary production and nitrogen uptake, characterized the phytoplankton community, and estimated nutrient depletion ratios across the under-sampled western Weddell Sea in mid-summer. Carbon export was highest at the ice shelves and was determined by a combination of physical, chemical, and biological factors.
Stéphanie H. M. Jacquet, Christian Tamburini, Marc Garel, Aurélie Dufour, France Van Vambeke, Frédéric A. C. Le Moigne, Nagib Bhairy, and Sophie Guasco
Biogeosciences, 18, 5891–5902, https://doi.org/10.5194/bg-18-5891-2021, https://doi.org/10.5194/bg-18-5891-2021, 2021
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We compared carbon remineralization rates (MRs) in the western and central Mediterranean Sea in late spring during the PEACETIME cruise, as assessed using the barium tracer. We reported higher and deeper (up to 1000 m depth) MRs in the western basin, potentially sustained by an additional particle export event driven by deep convection. The central basin is the site of a mosaic of blooming and non-blooming water masses and showed lower MRs that were restricted to the upper mesopelagic layer.
Shinsuke Kawagucci, Yohei Matsui, Akiko Makabe, Tatsuhiro Fukuba, Yuji Onishi, Takuro Nunoura, and Taichi Yokokawa
Biogeosciences, 18, 5351–5362, https://doi.org/10.5194/bg-18-5351-2021, https://doi.org/10.5194/bg-18-5351-2021, 2021
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Hydrogen and carbon isotope ratios of methane as well as the relevant biogeochemical parameters and microbial community compositions in hydrothermal plumes in the Okinawa Trough were observed. We succeeded in simultaneously determining hydrogen and carbon isotope fractionation factors associated with aerobic oxidation of methane in seawater (εH = 49.4 ± 5.0 ‰, εC = 5.2 ± 0.4 ‰) – the former being the first of its kind ever reported.
Nicolai Schleinkofer, David Evans, Max Wisshak, Janina Vanessa Büscher, Jens Fiebig, André Freiwald, Sven Härter, Horst R. Marschall, Silke Voigt, and Jacek Raddatz
Biogeosciences, 18, 4733–4753, https://doi.org/10.5194/bg-18-4733-2021, https://doi.org/10.5194/bg-18-4733-2021, 2021
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We have measured the chemical composition of the carbonate shells of the parasitic foraminifera Hyrrokkin sarcophaga in order to test if it is influenced by the host organism (bivalve or coral). We find that both the chemical and isotopic composition is influenced by the host organism. For example strontium is enriched in foraminifera that grew on corals, whose skeleton is built from aragonite, which is naturally enriched in strontium compared to the bivalves' calcite shell.
Lena Rohe, Traute-Heidi Anderson, Heinz Flessa, Anette Goeske, Dominika Lewicka-Szczebak, Nicole Wrage-Mönnig, and Reinhard Well
Biogeosciences, 18, 4629–4650, https://doi.org/10.5194/bg-18-4629-2021, https://doi.org/10.5194/bg-18-4629-2021, 2021
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This is the first experimental setup combining a complex set of methods (microbial inhibitors and isotopic approaches) to differentiate between N2O produced by fungi or bacteria during denitrification in three soils. Quantifying the fungal fraction with inhibitors was not successful due to large amounts of uninhibited N2O production. All successful methods suggested a small or missing fungal contribution. Artefacts occurring with microbial inhibition to determine N2O fluxes are discussed.
Inga Köhler, Raul E. Martinez, David Piatka, Achim J. Herrmann, Arianna Gallo, Michelle M. Gehringer, and Johannes A. C. Barth
Biogeosciences, 18, 4535–4548, https://doi.org/10.5194/bg-18-4535-2021, https://doi.org/10.5194/bg-18-4535-2021, 2021
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We investigated how high Fe(II) levels influence the O2 budget of a circum-neutral Fe(II)-rich spring and if a combined study of dissolved O (DO) and its isotopic composition can help assess this effect. We showed that dissolved Fe(II) can exert strong effects on the δ18ODO even though a constant supply of atmospheric O2 occurs. In the presence of photosynthesis, direct effects of Fe oxidation become masked. Critical Fe(II) concentrations indirectly control the DO by enhancing photosynthesis.
Owen A. Sherwood, Samuel H. Davin, Nadine Lehmann, Carolyn Buchwald, Evan N. Edinger, Moritz F. Lehmann, and Markus Kienast
Biogeosciences, 18, 4491–4510, https://doi.org/10.5194/bg-18-4491-2021, https://doi.org/10.5194/bg-18-4491-2021, 2021
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Pacific water flowing eastward through the Canadian Arctic plays an important role in redistributing nutrients to the northwest Atlantic Ocean. Using samples collected from northern Baffin Bay to the southern Labrador Shelf, we show that stable isotopic ratios in seawater nitrate reflect the fraction of Pacific to Atlantic water. These results provide a new framework for interpreting patterns of nitrogen isotopic variability recorded in modern and archival organic materials in the region.
Franziska Slotta, Lukas Wacker, Frank Riedel, Karl-Uwe Heußner, Kai Hartmann, and Gerhard Helle
Biogeosciences, 18, 3539–3564, https://doi.org/10.5194/bg-18-3539-2021, https://doi.org/10.5194/bg-18-3539-2021, 2021
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The African baobab is a challenging climate and environmental archive for its semi-arid habitat due to dating uncertainties and parenchyma-rich wood anatomy. Annually resolved F14C data of tree-ring cellulose (1941–2005) from a tree in Oman show the annual character of the baobab’s growth rings but were up to 8.8 % lower than expected for 1964–1967. Subseasonal δ13C and δ18O patterns reveal years with low average monsoon rain as well as heavy rainfall events from pre-monsoonal cyclones.
Peter M. J. Douglas, Emerald Stratigopoulos, Sanga Park, and Dawson Phan
Biogeosciences, 18, 3505–3527, https://doi.org/10.5194/bg-18-3505-2021, https://doi.org/10.5194/bg-18-3505-2021, 2021
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Hydrogen isotopes could be a useful tool to help resolve the geographic distribution of methane emissions from freshwater environments. We analyzed an expanded global dataset of freshwater methane hydrogen isotope ratios and found significant geographic variation linked to water isotopic composition. This geographic variability could be used to resolve changing methane fluxes from freshwater environments and provide more accurate estimates of the relative balance of global methane sources.
Veronica R. Rollinson, Julie Granger, Sydney C. Clark, Mackenzie L. Blanusa, Claudia P. Koerting, Jamie M. P. Vaudrey, Lija A. Treibergs, Holly C. Westbrook, Catherine M. Matassa, Meredith G. Hastings, and Craig R. Tobias
Biogeosciences, 18, 3421–3444, https://doi.org/10.5194/bg-18-3421-2021, https://doi.org/10.5194/bg-18-3421-2021, 2021
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We measured nutrients and the naturally occurring nitrogen (N) and oxygen (O) stable isotope ratios of nitrate discharged from a New England river over an annual cycle, to monitor N loading and identify dominant sources from the watershed. We uncovered a seasonality to loading and sources of N from the watershed. Seasonality in the nitrate isotope ratios also informed on N cycling, conforming to theoretical expectations of riverine nutrient cycling.
Zixun Chen, Xuejun Liu, Xiaoqing Cui, Yaowen Han, Guoan Wang, and Jiazhu Li
Biogeosciences, 18, 2859–2870, https://doi.org/10.5194/bg-18-2859-2021, https://doi.org/10.5194/bg-18-2859-2021, 2021
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δ13C in plants is a sensitive long-term indicator of physiological acclimatization. The present study suggests that precipitation change and increasing atmospheric N deposition have little impact on δ13C of H. ammodendron, a dominant plant in central Asian deserts, but affect its gas exchange. In addition, this study shows that δ13C of H. ammodendron could not indicate its water use efficiency (WUE), suggesting that whether δ13C of C4 plants indicates WUE is species-specific.
Petra Zahajská, Carolina Olid, Johanna Stadmark, Sherilyn C. Fritz, Sophie Opfergelt, and Daniel J. Conley
Biogeosciences, 18, 2325–2345, https://doi.org/10.5194/bg-18-2325-2021, https://doi.org/10.5194/bg-18-2325-2021, 2021
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The drivers of high accumulation of single-cell siliceous algae (diatoms) in a high-latitude lake have not been fully characterized before. We studied silicon cycling of the lake through water, radon, silicon, and stable silicon isotope balances. Results showed that groundwater brings 3 times more water and dissolved silica than the stream inlet. We demonstrate that groundwater discharge and low sediment deposition have driven the high diatom accumulation in the studied lake in the past century.
Yu-Te Hsieh, Walter Geibert, E. Malcolm S. Woodward, Neil J. Wyatt, Maeve C. Lohan, Eric P. Achterberg, and Gideon M. Henderson
Biogeosciences, 18, 1645–1671, https://doi.org/10.5194/bg-18-1645-2021, https://doi.org/10.5194/bg-18-1645-2021, 2021
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The South Atlantic near 40° S is one of the high-productivity and most dynamic nutrient regions in the oceans, but the sources and fluxes of trace elements (TEs) to this region remain unclear. This study investigates seawater Ra-228 and provides important constraints on ocean mixing and dissolved TE fluxes to this region. Vertical mixing is a more important source than aeolian or shelf inputs in this region, but particulate or winter deep-mixing inputs may be required to balance the TE budgets.
Zhongjie Yu and Emily M. Elliott
Biogeosciences, 18, 805–829, https://doi.org/10.5194/bg-18-805-2021, https://doi.org/10.5194/bg-18-805-2021, 2021
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In this study, we demonstrated distinct nitrogen isotope effects for nitric oxide (NO) production from major microbial and chemical NO sources in an agricultural soil. These results highlight characteristic bond-forming and breaking mechanisms associated with microbial and chemical NO production and implicate that simultaneous isotopic analyses of NO and nitrous oxide (N2O) can lead to unprecedented insights into the sources and processes controlling NO and N2O emissions from agricultural soils.
Daniel A. Frick, Rainer Remus, Michael Sommer, Jürgen Augustin, Danuta Kaczorek, and Friedhelm von Blanckenburg
Biogeosciences, 17, 6475–6490, https://doi.org/10.5194/bg-17-6475-2020, https://doi.org/10.5194/bg-17-6475-2020, 2020
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Silicon is taken up by some plants to increase structural stability and to develop stress resistance and is rejected by others. To explore the underlying mechanisms, we used the stable isotopes of silicon that shift in their relative abundance depending on the biochemical transformation involved. On species with a rejective (tomato, mustard) and active (wheat) uptake mechanism, grown in hydroculture, we found that the transport of silicic acid is controlled by the precipitation of biogenic opal.
Quentin Charbonnier, Julien Bouchez, Jérôme Gaillardet, and Éric Gayer
Biogeosciences, 17, 5989–6015, https://doi.org/10.5194/bg-17-5989-2020, https://doi.org/10.5194/bg-17-5989-2020, 2020
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The abundance and isotope composition of the trace metal barium (Ba) allows us to track and quantify nutrient cycling throughout the Amazon Basin. In particular, we show that the Ba biological fingerprint evolves from that of a strong net nutrient uptake in the mountainous area of the Andes towards efficient nutrient recycling on the plains of the Lower Amazon. Our study highlights the fact that the geochemical signature of rock-derived nutrients transported by the Amazon is scarred by life.
Ajinkya G. Deshpande, Thomas W. Boutton, Ayumi Hyodo, Charles W. Lafon, and Georgianne W. Moore
Biogeosciences, 17, 5639–5653, https://doi.org/10.5194/bg-17-5639-2020, https://doi.org/10.5194/bg-17-5639-2020, 2020
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Wetland forests in the southern USA are threatened by changing climate and human-induced pressures. We used tree ring widths and C isotopes as indicators of forest growth and physiological stress, respectively, and compared these to past climate data. We observed that vegetation growing in the drier patches is susceptible to stress, while vegetation growth and physiology in wetter patches is less sensitive to unfavorable environmental conditions, highlighting the importance of optimal wetness.
Dominika Lewicka-Szczebak, Maciej Piotr Lewicki, and Reinhard Well
Biogeosciences, 17, 5513–5537, https://doi.org/10.5194/bg-17-5513-2020, https://doi.org/10.5194/bg-17-5513-2020, 2020
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We present the first validation of N2O isotopic approaches for estimating N2O source pathways and N2O reduction. These approaches are widely used for tracing soil nitrogen cycling, but the results of these estimations are very uncertain. Here we report the results from parallel treatments allowing for precise validation of these approaches, and we propose the best strategies for results interpretation, including the new idea of an isotope model integrating three isotopic signatures of N2O.
Markus Raitzsch, Claire Rollion-Bard, Ingo Horn, Grit Steinhoefel, Albert Benthien, Klaus-Uwe Richter, Matthieu Buisson, Pascale Louvat, and Jelle Bijma
Biogeosciences, 17, 5365–5375, https://doi.org/10.5194/bg-17-5365-2020, https://doi.org/10.5194/bg-17-5365-2020, 2020
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The isotopic composition of boron in carbonate shells of marine unicellular organisms is a popular tool to estimate seawater pH. Usually, many shells need to be dissolved and measured for boron isotopes, but the information on their spatial distribution is lost. Here, we investigate two techniques that allow for measuring boron isotopes within single shells and show that they yield robust mean values but provide additional information on the heterogeneity within and between single shells.
Florian Einsiedl, Anja Wunderlich, Mathieu Sebilo, Ömer K. Coskun, William D. Orsi, and Bernhard Mayer
Biogeosciences, 17, 5149–5161, https://doi.org/10.5194/bg-17-5149-2020, https://doi.org/10.5194/bg-17-5149-2020, 2020
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Nitrate pollution of freshwaters and methane emissions into the atmosphere are crucial factors in deteriorating the quality of drinking water and in contributing to global climate change. Here, we report vertical concentration and stable isotope profiles of CH4, NO3-, NO2-, and NH4+ in the water column of Fohnsee (southern Bavaria, Germany) that may indicate linkages between nitrate-dependent anaerobic methane oxidation and the anaerobic oxidation of ammonium.
Ruifang C. Xie, Frédéric A. C. Le Moigne, Insa Rapp, Jan Lüdke, Beat Gasser, Marcus Dengler, Volker Liebetrau, and Eric P. Achterberg
Biogeosciences, 17, 4919–4936, https://doi.org/10.5194/bg-17-4919-2020, https://doi.org/10.5194/bg-17-4919-2020, 2020
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Thorium-234 (234Th) is widely used to study carbon fluxes from the surface ocean to depth. But few studies stress the relevance of oceanic advection and diffusion on the downward 234Th fluxes in nearshore environments. Our study in offshore Peru showed strong temporal variations in both the importance of physical processes on 234Th flux estimates and the oceanic residence time of 234Th, whereas salinity-derived seawater 238U activities accounted for up to 40 % errors in 234Th flux estimates.
Ralf A. Oeser and Friedhelm von Blanckenburg
Biogeosciences, 17, 4883–4917, https://doi.org/10.5194/bg-17-4883-2020, https://doi.org/10.5194/bg-17-4883-2020, 2020
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We present a novel strategy to decipher the relative impact of biogenic and abiotic drivers of weathering. We parameterized the nutrient fluxes in four ecosystems along a climate and vegetation gradient situated on the Chilean Coastal Cordillera. We investigated how nutrient demand by plants drives weathering. We found that the increase in biomass nutrient demand is accommodated by faster nutrient recycling rather than an increase in the weathering–release rates.
Tito Arosio, Malin M. Ziehmer, Kurt Nicolussi, Christian Schlüchter, and Markus Leuenberger
Biogeosciences, 17, 4871–4882, https://doi.org/10.5194/bg-17-4871-2020, https://doi.org/10.5194/bg-17-4871-2020, 2020
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Stable isotopes in tree-ring cellulose are tools for climatic reconstructions, but interpretation is challenging due to nonclimate trends. We analyzed the tree-age trends in tree-ring isotopes of deciduous larch and evergreen cembran pine. Samples covering the whole Holocene were collected at the tree line in the Alps. For cambial ages over 100 years, we prove the absence of age trends in δD, δ18O, and δ13C for both species. For lower cambial ages, trends differ for each isotope and species.
Yuyang He, Xiaobin Cao, and Huiming Bao
Biogeosciences, 17, 4785–4795, https://doi.org/10.5194/bg-17-4785-2020, https://doi.org/10.5194/bg-17-4785-2020, 2020
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Different carbon sites in a large organic molecule have different isotope compositions. Different carbon sites may not have the chance to exchange isotopes at all. The lack of appreciation of this notion might be blamed for an unsettled debate on the thermodynamic state of an organism. Here we demonstrate using minerals, N2O, and acetic acid that the dearth of exchange among different carbon sites renders them as independent as if they were different elements in organic molecules.
Felix M. Spielmann, Albin Hammerle, Florian Kitz, Katharina Gerdel, and Georg Wohlfahrt
Biogeosciences, 17, 4281–4295, https://doi.org/10.5194/bg-17-4281-2020, https://doi.org/10.5194/bg-17-4281-2020, 2020
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Carbonyl sulfide (COS) can be used as a proxy for plant photosynthesis on an ecosystem scale. However, the relationships between COS and CO2 fluxes and their dependence on daily to seasonal changes in environmental drivers are still poorly understood. We examined COS and CO2 ecosystem fluxes above an agriculturally used mountain grassland for 6 months. Harvesting of the grassland disturbed the otherwise stable COS-to-CO2 uptake ratio. We even found the canopy to release COS during those times.
Getachew Agmuas Adnew, Thijs L. Pons, Gerbrand Koren, Wouter Peters, and Thomas Röckmann
Biogeosciences, 17, 3903–3922, https://doi.org/10.5194/bg-17-3903-2020, https://doi.org/10.5194/bg-17-3903-2020, 2020
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We measured the effect of photosynthesis, the largest flux in the carbon cycle, on the triple oxygen isotope composition of atmospheric CO2 at the leaf level during gas exchange using three plant species. The main factors that limit the impact of land vegetation on the triple oxygen isotope composition of atmospheric CO2 are identified, characterized and discussed. The effect of photosynthesis on the isotopic composition of CO2 is commonly quantified as discrimination (ΔA).
Moritz Schroll, Frank Keppler, Markus Greule, Christian Eckhardt, Holger Zorn, and Katharina Lenhart
Biogeosciences, 17, 3891–3901, https://doi.org/10.5194/bg-17-3891-2020, https://doi.org/10.5194/bg-17-3891-2020, 2020
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Fungi have recently been identified to produce the greenhouse gas methane. Here, we investigated the stable carbon isotope values of methane produced by saprotrophic fungi. Our results show that stable isotope values of methane from fungi are dependent on the fungal species and the metabolized substrate. They cover a broad range and overlap with stable carbon isotope values of methane reported for methanogenic archaea, the thermogenic degradation of organic matter, and other eukaryotes.
Cited articles
Aber, J. D., Nadelhoffer, K. J., Steudler, P., and Melillo, J. M.: Nitrogen
Saturation in Northern Forest Ecosystems, Bioscience, 39, 378–386, 1989.
Aber, J. D., Goodale, C. L., Ollinger, S. V., Smith, M.-L., Magill, A. H.,
Martin, M. E., Hallett, R. A., and Stoddard, J. L.: Is nitrogen deposition
altering the nitrogen status of northeastern forests?, Bioscience, 53,
375–389, 2003.
Aikawa, M., Hiraki, T., Tamaki, M., and Shoga, M.: Difference between
filtering-type bulk and wet-only data sets based on site classification,
Atmos. Environ., 37, 2597–2603, 2003.
Alexander, B., Hastings, M. G., Allman, D. J., Dachs, J., Thornton, J. A.,
and Kunasek, S. A.: Quantifying atmospheric nitrate formation pathways based
on a global model of the oxygen isotopic composition (Δ17O) of
atmospheric nitrate, Atmos. Chem. Phys., 9, 5043–5056,
https://doi.org/10.5194/acp-9-5043-2009, 2009
Berner, E. K. and Berner, R. A.: The global water cycle: geochemistry and
environment, Englewood Cliffs, NJ, Prentice-Hall, 1987.
Bourgeois, I., Savarino, J., Caillon, N., Angot, H., Barbero, A., Delbart,
F., Voisin, D., and Clément, J.-C.: Tracing the fate of atmospheric
nitrate in a subalpine watershed using Δ17O, Environ. Sci.
Technol., 52, 5561–5570, 2018a.
Bourgeois, I., Savarino, J., Némery, J., Caillon, N., Albertin, S.,
Delbart, F., Voisin, D., and Clément, J.-C.: Atmospheric nitrate export
in streams along a montane to urban gradient, Sci. Total Environ., 633,
329–340, 2018b.
Breuer, L., Kiese, R., and Butterbach-Bahl, K.: Temperature and moisture
effects on nitrification rates in tropical rain-forest soils, Soil Sci. Soc.
Am. J., 66, 834–844, 2002.
Buchwald, C., Santoro, A. E., McIlvin, M. R., and Casciotti, K. L.: Oxygen
isotopic composition of nitrate and nitrite produced by nitrifying cocultures
and natural marine assemblages, Limnol. Oceanogr., 57, 1361–1375, 2012.
Clow, D. W., Roop, H. A., Nanus, L., Fenn, M. E., and Sexstone, G. A.:
Spatial patterns of atmospheric deposition of nitrogen and sulfur using
ion-exchange resin collectors in Rocky Mountain National Park, USA, Atmos.
Environ., 101, 149–157, 2015.
Costa, A. W., Michalski, G., Schauer, A. J., Alexander, B., Steig, E. J., and
Shepson, P. B.: Analysis of atmospheric inputs of nitrate to a temperate
forest ecosystem from Δ17O isotope ratio measurements,
Geophys. Res. Lett., 38, L15805, https://doi.org/10.1029/2011GL047539, 2011.
Dansgaard, W.: Stable isotopes in precipitation, Tellus, 16, 436–468, 1964.
Dejwakh, N. R., Meixner, T., Michalski, G., and McIntosh, J.: Using
17O to investigate nitrate sources and sinks in a semi-arid
groundwater system, Environ. Sci. Technol., 46, 745–751, 2012.
Durka, W., Schulze, E.-D., Gebauer, G., and Voerkeliust, S.: Effects of
forest decline on uptake and leaching of deposited nitrate determined from
15N and 18O measurements, Nature, 372, 765–767, 1994.
EANET: Data Report 2013, Network center for EANET (Acid Deposition Monitoring
Network in East Asia), Nigata, Japan, 2014.
EANET: Data Report 2014, Network center for EANET (Acid Deposition Monitoring
Network in East Asia), Nigata, Japan, 2015.
Hirota, A., Tsunogai, U., Komatsu, D. D., and Nakagawa, F.: Simultaneous
determination of δ15N and δ18O of N2O
and δ13C of CH4 in nanomolar quantities from a single
water sample, Rapid Commun. Mass Sp., 24, 1085–1092, 2010.
Hoyle, F. C., Murphy, D. V., and Fillery, I. R. P.: Temperature and stubble
management influence microbial CO2−C evolution and gross N
transformation rates, Soil Biol. Biochem., 38, 71–80, 2006.
Kabeya, N., Katsuyama, M., Kawasaki, M., Ohte, N., and Sugimoto, A.:
Estimation of mean residence times of subsurface waters using seasonal
variation in deuterium excess in a small headwater catchment in Japan,
Hydrol. Process., 21, 308–322, 2007.
Kaiser, J., Hastings, M. G., Houlton, B. Z., Röckmann, T., and Sigman, D.
M.: Triple oxygen isotope analysis of nitrate using the denitrifier method
and thermal decomposition of N2O, Anal. Chem., 79, 599–607, 2007.
Kamisako, M., Sase, H., Matsui, T., Suzuki, H., Takahashi, A., Oida, T.,
Nakata, M., Totsuka, T., and Ueda, H.: Seasonal and annual fluxes of
inorganic constituents in a small catchment of a Japanese cedar forest near
the Sea of Japan, Water Air Soil Poll., 195, 51–61, 2008.
Kendall, C.: Tracing Nitrogen Sources and Cycling in Catchments, in: Isotope
Tracers in Catchment Hydrology, edited by: Kendall, C. and McDonnell, J. J.,
Elsevier Science B.V., Amsterdam, 519–576, 1998.
Kendall, C., Campbell, D. H., Burns, D. A., Schanley, J. B., Silva, S. R.,
and Chang, C. C. Y.: Tracing sources of nitrate in snowmelt runoff using the
oxygen and nitrogen isotopic compositions of nitrate, in: Biogeochemistry of
seasonally snow-covered catchments, Proceedings of a Boulder Symposium,
Boulder, Co., 3–14 July 1995, IAHS Publication No. 228, 339–347, 1995.
Kendall, C., Elliott, E. M., and Wankel, S. D.: Tracing anthropogenic inputs
of nitrogen to ecosystems, in: Stable Isotopes in Ecology and Environmental
Science, 2nd edn., edited by: Michener, R. H. and Lajtha, K., Blackwell
Publishing, Oxford, UK, 2007.
Komatsu, D. D., Ishimura, T., Nakagawa, F., and Tsunogai, U.: Determination
of the 15N ∕ 14N, 17O ∕ 16O,
and 18O ∕ 16O ratios of nitrous oxide by using
continuous-flow isotope-ratio mass spectrometry, Rapid Commun. Mass Sp., 22,
1587–1596, 2008.
Konno, U., Tsunogai, U., Komatsu, D. D., Daita, S., Nakagawa, F., Tsuda, A.,
Matsui, T., Eum, Y.-J., and Suzuki, K.: Determination of total N2
fixation rates in the ocean taking into account both the particulate and
filtrate fractions, Biogeosciences, 7, 2369–2377,
https://doi.org/10.5194/bg-7-2369-2010, 2010.
Koshikawa, M., Watanabe, M., Takamatsu, T., Hayashi, S., Nohara, S., and
Satake, K.: Relationships between stream water chemistry and watershed
geology and topography in the Miomote River System, Niigata, Japan, Jap. J.
Limnol., 72, 71–80, 2011 (in Japanese with English abstract).
Liu, T., Wang, F., Michalski, G., Xia, X., and Liu, S.: Using 15N,
17O, and 18O To Determine Nitrate Sources in the Yellow
River, China, Environ. Sci. Technol., 47, 13412–13421,
https://doi.org/10.1021/es403357m, 2013.
McIlvin, M. R. and Altabet, M. A.: Chemical conversion of nitrate and nitrite
to nitrous oxide for nitrogen and oxygen isotope analysis in freshwater and
seawater, Anal. Chem., 77, 5589–5595, 2005.
McIsaac, G. F., David, M. B., Gertner, G. Z., and Goolsby, D. A.:
Eutrophication: Nitrate flux in the Mississippi River, Nature, 414, 166–167,
2001.
Michalski, G., Savarino, J., Böhlke, J. K., and Thiemens, M.:
Determination of the total oxygen isotopic composition of nitrate and the
calibration of a Δ17O nitrate reference material, Anal. Chem.,
74, 4989–4993, 2002.
Michalski, G., Scott, Z., Kabiling, M., and Thiemens, M. H.: First
measurements and modeling of Δ17O in atmospheric nitrate,
Geophys. Res. Lett., 30, 1870, https://doi.org/10.1029/2003GL017015, 2003.
Michalski, G., Meixner, T., Fenn, M., Hernandez, L., Sirulnik, A., Allen, E.,
and Thiemens, M.: Tracing Atmospheric Nitrate Deposition in a Complex
Semiarid Ecosystem Using Δ17O, Environ. Sci. Technol., 38,
2175–2181, 2004.
Miller, M. F.: Isotopic fractionation and the quantification of 17O
anomalies in the oxygen three-isotope system: an appraisal and geochemical
significance, Geochim. Cosmochim. Ac., 66, 1881–1889, 2002.
Mitchell, M. J., Iwatsubo, G., Ohrui, K., and Nakagawa, Y.: Nitrogen
saturation in Japanese forests: an evaluation, Forest Ecol. Manag., 97,
39–51, 1997.
Morin, S., Savarino, J., Frey, M. M., Yan, N., Bekki, S., Bottenheim, J. W.,
and Martins, J. M. F.: Tracing the origin and fate of NOx in
the Arctic atmosphere using stable isotopes in nitrate, Science, 322,
730–732, 2008.
Nakagawa, F., Suzuki, A., Daita, S., Ohyama, T., Komatsu, D. D., and
Tsunogai, U.: Tracing atmospheric nitrate in groundwater using triple oxygen
isotopes: evaluation based on bottled drinking water, Biogeosciences, 10,
3547–3558, https://doi.org/10.5194/bg-10-3547-2013, 2013.
Nakahara, O., Takahashi, M., Sase, H., Yamada, T., Matsuda, K., Ohizumi, T.,
Fukuhara, H., Inoue, T., Takahashi, A., Kobayashi, H., Hatano, R., and
Hakamata, T.: Soil and stream water acidification in a forested catchment in
central Japan, Biogeochemistry, 97, 141–158, 2010.
Nelson, D. M., Tsunogai, U., Ding, D., Ohyama, T., Komatsu, D. D., Nakagawa,
F., Noguchi, I., and Yamaguchi, T.: Triple oxygen isotopes indicate
urbanization affects sources of nitrate in wet and dry atmospheric
deposition, Atmos. Chem. Phys., 18, 6381–6392,
https://doi.org/10.5194/acp-18-6381-2018, 2018.
Ogawa, S.: Forests and water resources, chap. 3, in: Hydrological Cycle and
Local Metabolic System of Water, edited by: Tambo, N. and Maruyama, T.,
Gihodo, 2003 (in Japanese).
Ohte, N., Sebestyen, S. D., Shanley, J. B., Doctor, D. H., Kendall, C.,
Wankel, S. D., and Boyer, E. W.: Tracing sources of nitrate in snowmelt
runoff using a high-resolution isotopic technique, Geophys. Res. Lett., 31,
L21506, https://doi.org/10.1029/2004GL020908, 2004.
Paerl, H. W.: Controlling eutrophication along the freshwater–marine
continuum: Dual nutrient (N and P) reductions are essential, Estuar. Coast.,
32, 593–601, 2009.
Pellerin, B., Saraceno, J., Shanley, J., Sebestyen, S., Aiken, G., Wollheim,
W., and Bergamaschi, B.: Taking the pulse of snowmelt: in situ sensors reveal
seasonal, event and diurnal patterns of nitrate and dissolved organic matter
variability in an upland forest stream, Biogeochemistry, 108, 183–198, 2012.
Peterjohn, W. T., Adams, M. B., and Gilliam, F. S.: Symptoms of nitrogen
saturation in two central Appalachian hardwood forest ecosystems,
Biogeochemistry, 35, 507–522, 1996.
Piatek, K. B., Mitchell, M. J., Silva, S. R., and Kendall, C.: Sources of
nitrate in snowmelt discharge: evidence from water chemistry and stable
isotopes of nitrate, Water Air Soil Poll., 165, 13–35, 2005.
Riha, K. M., Michalski, G., Gallo, E. L., Lohse, K. A., Brooks, P. D., and
Meixner, T.: High Atmospheric Nitrate Inputs and Nitrogen Turnover in
Semi-arid Urban Catchments, Ecosystems, 17, 1309–1325, 2014.
Rose, L. A., Elliott, E. M., and Adams, M. B.: Triple Nitrate Isotopes
Indicate Differing Nitrate Source Contributions to Streams Across a Nitrogen
Saturation Gradient, Ecosystems, 18, 1209–1223, 2015a.
Rose, L. A., Sebestyen, S. D., Elliott, E. M., and Koba, K.: Drivers of
atmospheric nitrate processing and export in forested catchments, Water
Resour. Res., 51, 1333–1352, 2015b.
Sabo, R. D., Nelson, D. M., and Eshleman, K. N.: Episodic, seasonal, and
annual export of atmospheric and microbial nitrate from a temperate forest,
Geophys. Res. Lett., 43, 683–691, https://doi.org/10.1002/2015GL066758, 2016.
Sase, H., Takahashi, A., Sato, M., Kobayashi, H., Nakata, M., and Totsuka,
T.: Seasonal variation in the atmospheric deposition of inorganic
constituents and canopy interactions in a Japanese cedar forest, Environ.
Pollut., 152, 1–10, 2008.
Sase, H., Matsuda, K., Visaratana, T., Garivait, H., Yamashita, N.,
Kietvuttinon, B., Hongthong, B., Luangjame, J., Khummongkol, P., Shindo, J.,
Endo, T., Sato, K., Uchiyama, S., Miyazawa, M., Nakata, M., and Lenggoro, I.
W.: Deposition Process of Sulfate and Elemental Carbon in Japanese and Thai
Forests, Asian Journal of Atmospheric Environment, 6, 246–258, 2012.
Sase, H., Ohizumi, T., Yamashita, N., Visaratana, T., Kietvuttinon, B.,
Garivait, H., and Majid, N. M.: Dynamics of Sulphur Derived from Atmospheric
Deposition and its Possible Impacts on East Asian Forests, Final Report
submitted to APN (Project Refence Number: ARCP2013-13CMY-Sase), Asia-Pacific
Network for Global Change Research, Kobe, Japan, 2015.
Shibata, H., Kuraji, K., Toda, H., and Sasa, K.: Regional Comparison of
Nitrogen Export to Japanese Forest Streams, Sci. World J., 1, 572–580,
https://doi.org/10.1100/tsw.2001.371, 2001.
Stoddard, J. L.: Long-Term Changes in Watershed Retention of Nitrogen: Its
Causes and Aquatic Consequences. In: Environmental Chemistry of Lakes and
Reservoirs, Baker, L. A. (Ed.), Advances in Chemistry Series, American
Chemical Society, Washington DC, 1994.
Takagi, K., Fukuzawa, K., Liang, N., Kayama, M., Nomura, M., Hojyo, H.,
Sugata, S., Shibata, H., Fukazawa, T., Takahashi, Y., Nakaji, T., Oguma, H.,
Mano, M., Akibayashi, Y., Murayama, T., Koike, T., Sasa, K., and Fujinuma,
Y.: Change in CO2 balance under a series of forestry activities in a
cool-temperate mixed forest with dense undergrowth, Glob. Change Biol., 15,
1275–1288, 2009.
Takimoto, H., Tanaka, T., and Horino, H.: Does forest conserve runoff
discharge during drought?, Transactions of The Japanese Society of
Irrigation, Drainage and Reclamation Engineering, 170, 75–81,
https://doi.org/10.11408/jsidre1965.1994.170_75, 1994 (in Japanese with English
abstract).
Tanoue, M., Ichiyanagi, K., and Shimada, J.: Seasonal variation and spatial
distribution of stable isotopes in precipitation over Japan, Journal of
Japanese Association of Hydrological Sciences, 43, 73–91, 2013 (in Japanese
with English abstract).
Thiemens, M. H., Savarino, J., Farquhar, J., and Bao, H.: Mass-Independent
Isotopic Compositions in Terrestrial and Extraterrestrial Solids and Their
Applications, Accounts Chem. Res., 34, 645–652, 2001.
Tsunogai, U., Kido, T., Hirota, A., Ohkubo, S. B., Komatsu, D. D., and
Nakagawa, F.: Sensitive determinations of stable nitrogen isotopic
composition of organic nitrogen through chemical conversion into N2O,
Rapid Commun. Mass Sp., 22, 345–354, 2008.
Tsunogai, U., Komatsu, D. D., Daita, S., Kazemi, G. A., Nakagawa, F.,
Noguchi, I., and Zhang, J.: Tracing the fate of atmospheric nitrate deposited
onto a forest ecosystem in Eastern Asia using Δ17O, Atmos.
Chem. Phys., 10, 1809–1820, https://doi.org/10.5194/acp-10-1809-2010, 2010.
Tsunogai, U., Daita, S., Komatsu, D. D., Nakagawa, F., and Tanaka, A.:
Quantifying nitrate dynamics in an oligotrophic lake using Δ17O, Biogeosciences, 8, 687–702, https://doi.org/10.5194/bg-8-687-2011, 2011.
Tsunogai, U., Komatsu, D. D., Ohyama, T., Suzuki, A., Nakagawa, F., Noguchi,
I., Takagi, K., Nomura, M., Fukuzawa, K., and Shibata, H.: Quantifying the
effects of clear-cutting and strip-cutting on nitrate dynamics in a forested
watershed using triple oxygen isotopes as tracers, Biogeosciences, 11,
5411–5424, https://doi.org/10.5194/bg-11-5411-2014, 2014.
Tsunogai, U., Miyauchi, T., Ohyama, T., Komatsu, D. D., Nakagawa, F., Obata,
Y., Sato, K., and Ohizumi, T.: Accurate and precise quantification of
atmospheric nitrate in streams draining land of various uses by using triple
oxygen isotopes as tracers, Biogeosciences, 13, 3441–3459,
https://doi.org/10.5194/bg-13-3441-2016, 2016.
Tsunogai, U., Miyauchi, T., Ohyama, T., Komatsu, D. D., Ito, M., and
Nakagawa, F.: Quantifying nitrate dynamics in a mesotrophic lake using triple
oxygen isotopes as tracers, Limnol. Oceanogr., 63, S458–S476, 2018.
Wright, R. F. and Tietema, A.: Ecosystem response to 9 years of nitrogen
addition at Sogndal, Norway, Forest Ecol. Manag., 71, 133–142, 1995.
Yamada, T., Inoue, T., Fukuhara, H., Nakahara, O., Izuta, T., Suda, R.,
Takahashi, M., Sase, H., Takahashi, A., Kobayashi, H., Ohizumi, T., and
Hakamata, T.: Long-term Trends in Surface Water Quality of Five Lakes in
Japan, Water Air Soil Poll.: Focus, 7, 259–266, 2007.
Yamazaki, A., Watanabe, T., and Tsunogai, U.: Nitrogen isotopes of organic
nitrogen in reef coral skeletons as a proxy of tropical nutrient dynamics,
Geophys. Res. Lett., 38, L19605, https://doi.org/10.1029/2011GL049053, 2011.
Zaman, M. and Chang, S. X.: Substrate type, temperature, and moisture content
affect gross and net N mineralization and nitrification rates in agroforestry
systems, Biol. Fert. Soils, 39, 269–279, 2004.
Short summary
To clarify the biological processing of nitrate within temperate forested catchments using unprocessed atmospheric nitrate exported from each catchment as a tracer, we continuously monitored stream nitrate concentrations and stable isotopic compositions in three forested catchments for more than 2 years. We concluded that the export flux of unprocessed atmospheric nitrate relative to the deposition flux in each forest ecosystem is applicable as an index for nitrogen saturation.
To clarify the biological processing of nitrate within temperate forested catchments using...
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