Sina Wallschuss, Julie Granger, Annie Bourbonnais, Raquel Flynn, Jessica Burger, Keshnee Pillay, Sarah Fawcett
{"title":"沉积物在调节Benguela南部上升流系统氧化亚氮生成中的作用:来自稳定同位素示踪剂的见解","authors":"Sina Wallschuss, Julie Granger, Annie Bourbonnais, Raquel Flynn, Jessica Burger, Keshnee Pillay, Sarah Fawcett","doi":"10.1029/2024GB008463","DOIUrl":null,"url":null,"abstract":"<p>The ocean accounts for ∼20%–30% of global nitrous oxide (N<sub>2</sub>O) emissions, with coastal upwelling systems estimated to contribute disproportionately to the sea-air flux of this potent greenhouse gas. To investigate the mechanisms of and controls on N<sub>2</sub>O production in coastal upwelling systems, we measured the concentration and nitrogen and oxygen isotopic composition of N<sub>2</sub>O (δ<sup>15</sup>N-N<sub>2</sub>O and δ<sup>18</sup>O-N<sub>2</sub>O) along a cross-shelf transect in the Southern Benguela Upwelling System (SBUS). At the shelf bottom, N<sub>2</sub>O concentrations increased from the outer shelf toward the shore (11–32 nM) inversely to dissolved oxygen (182 ± 17 to <1 μM) and in concert with the remineralization tracers, apparent oxygen utilization (108 ± 21 to 221 ± 33 μM) and nitrogen (N)-deficit (up to 20.4 μM). These observations suggest that both nitrification and denitrification may be involved in N<sub>2</sub>O production on the SBUS shelf. The δ<sup>15</sup>N-N<sub>2</sub>O implicates both processes as potential N<sub>2</sub>O sources on the shelf, with high δ<sup>18</sup>O-N<sub>2</sub>O values (≤57.2‰) specifically incriminating sediments as the primary N<sub>2</sub>O source to the water column. Isotopic changes across the shelf delineate three discrete domains with distinct N<sub>2</sub>O sources. Sedimentary nitrification and/or denitrification dominate N<sub>2</sub>O production on the <i>midshelf</i>, while coupled nitrification-denitrification explains N<sub>2</sub>O production on the <i>inner-shelf</i>. At the <i>shallow inner-shelf</i> where oxygen is depleted, both water column and sedimentary denitrification account for the production and partial consumption of N<sub>2</sub>O. This study illuminates the disproportionate contribution of sedimentary N cycling to N<sub>2</sub>O production on the SBUS shelf.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 8","pages":""},"PeriodicalIF":5.5000,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008463","citationCount":"0","resultStr":"{\"title\":\"The Role of Sediments in Modulating Nitrous Oxide Production in the Southern Benguela Upwelling System: Insights From Stable Isotopic Tracers\",\"authors\":\"Sina Wallschuss, Julie Granger, Annie Bourbonnais, Raquel Flynn, Jessica Burger, Keshnee Pillay, Sarah Fawcett\",\"doi\":\"10.1029/2024GB008463\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>The ocean accounts for ∼20%–30% of global nitrous oxide (N<sub>2</sub>O) emissions, with coastal upwelling systems estimated to contribute disproportionately to the sea-air flux of this potent greenhouse gas. To investigate the mechanisms of and controls on N<sub>2</sub>O production in coastal upwelling systems, we measured the concentration and nitrogen and oxygen isotopic composition of N<sub>2</sub>O (δ<sup>15</sup>N-N<sub>2</sub>O and δ<sup>18</sup>O-N<sub>2</sub>O) along a cross-shelf transect in the Southern Benguela Upwelling System (SBUS). At the shelf bottom, N<sub>2</sub>O concentrations increased from the outer shelf toward the shore (11–32 nM) inversely to dissolved oxygen (182 ± 17 to <1 μM) and in concert with the remineralization tracers, apparent oxygen utilization (108 ± 21 to 221 ± 33 μM) and nitrogen (N)-deficit (up to 20.4 μM). These observations suggest that both nitrification and denitrification may be involved in N<sub>2</sub>O production on the SBUS shelf. The δ<sup>15</sup>N-N<sub>2</sub>O implicates both processes as potential N<sub>2</sub>O sources on the shelf, with high δ<sup>18</sup>O-N<sub>2</sub>O values (≤57.2‰) specifically incriminating sediments as the primary N<sub>2</sub>O source to the water column. Isotopic changes across the shelf delineate three discrete domains with distinct N<sub>2</sub>O sources. Sedimentary nitrification and/or denitrification dominate N<sub>2</sub>O production on the <i>midshelf</i>, while coupled nitrification-denitrification explains N<sub>2</sub>O production on the <i>inner-shelf</i>. At the <i>shallow inner-shelf</i> where oxygen is depleted, both water column and sedimentary denitrification account for the production and partial consumption of N<sub>2</sub>O. This study illuminates the disproportionate contribution of sedimentary N cycling to N<sub>2</sub>O production on the SBUS shelf.</p>\",\"PeriodicalId\":12729,\"journal\":{\"name\":\"Global Biogeochemical Cycles\",\"volume\":\"39 8\",\"pages\":\"\"},\"PeriodicalIF\":5.5000,\"publicationDate\":\"2025-08-05\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008463\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Global Biogeochemical Cycles\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GB008463\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"ENVIRONMENTAL SCIENCES\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Global Biogeochemical Cycles","FirstCategoryId":"89","ListUrlMain":"https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GB008463","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
The Role of Sediments in Modulating Nitrous Oxide Production in the Southern Benguela Upwelling System: Insights From Stable Isotopic Tracers
The ocean accounts for ∼20%–30% of global nitrous oxide (N2O) emissions, with coastal upwelling systems estimated to contribute disproportionately to the sea-air flux of this potent greenhouse gas. To investigate the mechanisms of and controls on N2O production in coastal upwelling systems, we measured the concentration and nitrogen and oxygen isotopic composition of N2O (δ15N-N2O and δ18O-N2O) along a cross-shelf transect in the Southern Benguela Upwelling System (SBUS). At the shelf bottom, N2O concentrations increased from the outer shelf toward the shore (11–32 nM) inversely to dissolved oxygen (182 ± 17 to <1 μM) and in concert with the remineralization tracers, apparent oxygen utilization (108 ± 21 to 221 ± 33 μM) and nitrogen (N)-deficit (up to 20.4 μM). These observations suggest that both nitrification and denitrification may be involved in N2O production on the SBUS shelf. The δ15N-N2O implicates both processes as potential N2O sources on the shelf, with high δ18O-N2O values (≤57.2‰) specifically incriminating sediments as the primary N2O source to the water column. Isotopic changes across the shelf delineate three discrete domains with distinct N2O sources. Sedimentary nitrification and/or denitrification dominate N2O production on the midshelf, while coupled nitrification-denitrification explains N2O production on the inner-shelf. At the shallow inner-shelf where oxygen is depleted, both water column and sedimentary denitrification account for the production and partial consumption of N2O. This study illuminates the disproportionate contribution of sedimentary N cycling to N2O production on the SBUS shelf.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.