2 days Ago
March 31, 2025 This article has been reviewed according to Science X's editorial process and policies . Editors have highlightedthe following attributes while ensuring the content's credibility: fact-checked trusted source proofread by Sarah Derouin, American Geophysical Union Scientists know that streams and rivers can contribute significant quantities of greenhouse gases to the atmosphere. One way these bodies of water come to contain greenhouse gases is via groundwater, which picks up carbon and nitrogen as it seeps and flows through rock and sediment near rivers.
Much research into greenhouse gas emissions from rivers assumes that before being released into the atmosphere, the gases in this groundwater mix with the currents of rivers and streams . But during low-flow conditions, groundwater can seep out along stream banks at or above the river surface, creating a pathway for greenhouse gases to escape directly from groundwater. Alaina Bisson and colleagues set out to estimate the magnitude of emissions from groundwater rising directly to the surface, known as groundwater discharge .
They measured greenhouse gas emissions along riverbanks at three locations in the Farmington River watershed in Connecticut and Massachusetts, concentrating on areas that had groundwater discharge above the waterlines during a typical summer flow season. Their findings are published in the Journal of Geophysical Research: Biogeosciences . At each stream, the team used handheld thermal infrared cameras to identify stream banks with and without areas of exposed groundwater discharge.
Once these stream banks were located, the team measured fluxes of the greenhouse gases carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane, as well as groundwater discharge rates along the stream banks. They also collected subsurface groundwater samples and analyzed the samples for concentrations of dissolved organic carbon , oxygen, and nitrogen. At one site, the researchers found that CO 2 concentrations were 1.
4–19.2 times higher in groundwater discharge than in surface water and N 2 O concentrations were 1.1–40.
6 times higher. In comparison, stretches of stream with no groundwater seeps acted as N 2 O sinks. They also found that groundwater emissions of CO 2 and N 2 O were 1.
5 and 1.6 times higher than surface water emissions, respectively. On average, 21% of emissions from the groundwater seeps were released into the atmosphere before they could mix with surface waters.
The authors note that their work shows that exposed groundwater discharge along stream banks can be a significant, often unaccounted-for, source of river corridor greenhouse gas emissions. They add that more work should be done to better understand potential emissions from river corridors where groundwater discharge is abundant. More information: Alaina M.
Bisson et al, Preferential Groundwater Discharges Along Stream Corridors Are Disregarded Sources of Greenhouse Gases, Journal of Geophysical Research: Biogeosciences (2025). DOI: 10.1029/2024JG008395 Provided by American Geophysical Union This story is republished courtesy of Eos, hosted by the American Geophysical Union.
Read the original story here ..
