Methane and Nitrous Oxide Reshape the Air‐Water Greenhouse Gas Budget of a Tropical Estuarine Delta
メタンと一酸化二窒素が熱帯河口デルタの大気-水間温室効果ガス収支を変形させる (AI 翻訳)
Luiz C. Cotovicz, Renato P. Ribeiro, Luciana O. Vidal, Marcelo C. Bernardes, Carlos E. De Rezende, Batiaan A. Knoppers, Gwenaël Abril
🤖 gxceed AI 要約
日本語
本研究はブラジルの熱帯河口デルタ（パライーバ・ド・スル川）において、メタン（CH4）と一酸化二窒素（N2O）の大気-水間フラックスを測定し、CO2データと組み合わせて温室効果ガス収支を評価した。CH4は淡水域とマングローブ水路で高濃度であり、大気への恒常的な放出源となっていた。N2Oは変動が小さく、硝化プロセスが支配的であった。CH4とN2OをCO2換算で考慮すると、乾期にはCO2吸収の10～85%を相殺し、湿期にはCO2放出を18～42%増加させた。
English
This study measured methane (CH4) and nitrous oxide (N2O) air-water fluxes in a tropical estuarine delta in Brazil (Paraíba do Sul River) and combined them with CO2 data to assess the greenhouse gas budget. CH4 concentrations were highest in freshwater and mangrove creeks, indicating a permanent source to the atmosphere. N2O showed weaker variability and was linked to nitrification. In CO2-equivalent terms, CH4 and N2O offset 10-85% of the CO2 sink in dry periods and added 18-42% to CO2 emissions during wet periods.
Unofficial AI-generated summary based on the public title and abstract. Not an official translation.
📝 gxceed 編集解説 — Why this matters
日本のGX文脈において
本論文はブラジルの熱帯河口域の事例であるため、日本のGX文脈に直接関連するものではない。しかし、沿岸域の温室効果ガス収支にメタンや一酸化二窒素を含める重要性を示唆しており、日本の沿岸環境評価やMRV（測定・報告・検証）の高度化に参考となる可能性がある。
In the global GX context
This paper is a case study of a tropical estuary in Brazil, but it underscores the importance of including methane and nitrous oxide in estuarine greenhouse gas budgets globally. For GX practitioners, it highlights that carbon accounting frameworks (e.g., for natural climate solutions) need to consider non-CO2 gases to avoid overestimating sinks.
👥 読者別の含意
🔬研究者:Climate scientists studying estuarine greenhouse gas fluxes will find detailed empirical data on CH4 and N2O dynamics and their relative contribution to the radiative balance.
📄 Abstract（原文）
Abstract Estuaries are important sources and sinks of greenhouse gases (GHGs), yet assessments of their radiative balance often focus primarily on carbon dioxide (CO 2 ), with less attention given to methane (CH 4 ) and nitrous oxide (N 2 O). We combine measurements of CH 4 and N 2 O air‐water fluxes with concurrent CO 2 data in a tropical estuarine delta (Paraíba do Sul River, Brazil), based on three surveys under contrasting hydrological conditions. CH 4 concentrations were highest in freshwater‐dominated waters and mangrove creeks and decreased seaward, with greater values during high river discharge. Surface waters were supersaturated in CH 4 , indicating a permanent atmospheric source driven by freshwater inputs and organic matter degradation. In contrast, N 2 O exhibited weaker variability and alternated between source and sink, with concentrations linked to ammonium (NH 4 + ) and apparent oxygen utilization, suggesting nitrification as a dominant control. In CO 2 ‐equivalent terms, CH 4 emissions offset 30%–84% of the CO 2 sink during dry conditions and enhanced CO 2 emissions by 20%–44% during high discharge. N 2 O exerted a smaller but variable influence, either reinforcing or partially counterbalancing CO 2 fluxes. Together, CH 4 and N 2 O offset 10%–85% of the CO 2 sink in dry periods and added 18%–42% to CO 2 emissions during wet conditions. The relative influence of CH 4 and N 2 O was greatest where CO 2 fluxes were near equilibrium, particularly in the mixing and marine domains. Because many tropical deltas exhibit mixing‐driven CO 2 uptake of weak magnitude, CH 4 and N 2 O fluxes can reshape the radiative balance, underscoring the need for combined GHG assessments where CO 2 exchange is low or bidirectional.
🔗 Provenance — このレコードを発見したソース
- crossref https://doi.org/10.1029/2026jg009956first seen 2026-07-15 06:07:28
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