{
  "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.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 7,
  "authors": [
    {
      "name": "Luiz Cotovicz"
    },
    {
      "name": "Renato Ribeiro"
    },
    {
      "name": "Luciana Vidal"
    },
    {
      "name": "Marcelo Bernardes"
    },
    {
      "name": "Carlos de Rezende"
    },
    {
      "name": "Batiaan Knoppers"
    },
    {
      "name": "Gwenaël Abril"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ecefp32vrpcbj.bib",
  "cited_by": 0,
  "doi": "10.1029/2026jg009956",
  "fulltext_url": null,
  "id": "ecefp32vrpcbj",
  "issns": [
    "2169-8953"
  ],
  "landing_url": "https://hal.science/hal-05741237v1",
  "language": "en",
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.chim"
    ],
    [
      "hal",
      "0.sdu"
    ],
    [
      "hal",
      "1.chim.othe"
    ],
    [
      "hal",
      "1.sdu.ocean"
    ],
    [
      "openalex",
      "1910|Marine and coastal ecosystems"
    ]
  ],
  "openalex": "W7168249809",
  "pdf_url": "https://hal.science/hal-05741237/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-07-14",
  "publisher": "American Geophysical Union",
  "ris": "https://research.draconitic.com/paper/ecefp32vrpcbj.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:39Z",
      "native_id": "hal-05741237",
      "source": "hal",
      "url": "https://hal.science/hal-05741237v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "hal:0.chim",
      "subfield": "general"
    },
    {
      "field": "earth",
      "origin": "hal:1.sdu.ocean",
      "subfield": "oceanography"
    }
  ],
  "title": "Methane and Nitrous Oxide Reshape the Air‐Water Greenhouse Gas Budget of a Tropical Estuarine Delta",
  "title_text": "Methane and Nitrous Oxide Reshape the Air‐Water Greenhouse Gas Budget of a Tropical Estuarine Delta",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:39Z",
  "url": "https://research.draconitic.com/paper/ecefp32vrpcbj",
  "venue": "Journal of Geophysical Research: Biogeosciences",
  "versions": []
}