Volatile organic compounds may be underestimated in the carbon cycle
Rainwater connects the biogeochemical cycles of land and the atmosphere. It's effectively a chemical conveyor belt that delivers compounds to the ground during a process called wet deposition.
Volatile organic compounds (VOCs) may be significantly underrepresented in the carbon cycle, according to a new review in the Journal of Geophysical Research: Biogeosciences. Ana Yañez-Serrano and her colleagues estimate that roughly 100 teragrams of carbon, out of the 460 teragrams delivered annually via wet deposition, come from VOCs in rainwater.
These compounds, which can be found in petroleum fuels, paint thinners, and pharmaceuticals, have been largely overlooked in biogeochemical research. Scientists have long assumed their role in rainwater-based cycling was negligible due to limitations in detection techniques. However, recent improvements in analytical methods have revealed VOCs are present in rainwater at higher concentrations than previously thought.
VOCs are highly reactive and biologically labile, meaning even small concentrations can impact water chemistry, plants, and microorganisms at local to regional scales. Their presence in carbon-limited ecosystems could trigger rapid biological responses. The authors highlight key knowledge gaps and suggest next steps for the research community, emphasizing the need for improved detection methods and modeling.
Most atmospheric carbon budgets currently exclude or underestimate water-soluble VOCs and their oxidized products, leaving this reactive form of carbon out of the equation. Modelers must explore VOC mechanisms and transport, incorporate them into Earth system models, and observe the effects of VOC wet deposition on terrestrial ecosystems and biogeochemical cycles.
As climate change and human activities intensify VOC emissions and alter rainwater patterns, understanding VOCs as an overlooked component of Earth's biogeochemistry has become increasingly crucial.
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