A new review in the Journal of Geophysical Research: Biogeosciences finds that volatile organic compounds, or VOCs, are a much bigger piece of the carbon cycle than previously recognized. The authors estimate that roughly 100 teragrams of carbon per year reach the ground through wet deposition of VOCs, out of about 460 teragrams delivered by rainwater overall. That challenges the long-held assumption that organic compounds in rainwater are negligible compared to nitrate and sulfate deposition. The review highlights a blind spot in carbon cycle modeling. VOCs are highly reactive and biologically available, so even small concentrations can alter water chemistry and trigger responses in carbon-limited ecosystems. Most atmospheric carbon budgets omit or underestimate water-soluble VOCs and their oxidized products. The authors call for better detection methods, more monitoring, and updated Earth system models to account for this overlooked carbon input. For anyone tracking carbon fluxes, the takeaway is that wet deposition of VOCs is not a minor side note. Climate change and human activity are expected to increase VOC emissions, making it more important to measure and model this pathway accurately.
