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Long-term rise in riverine dissolved organic carbon concentration is predicted by electrolyte solubility theory
Citation:
Monteith, D., P. Henrys, J. Hruska, H. de Wit, P. Kram, F. Moldan, M. Posch, A. Raike, J. Stoddard, E. Shilland, M. Pereira, AND C. Evans. Long-term rise in riverine dissolved organic carbon concentration is predicted by electrolyte solubility theory. Science Advances. American Association for the Advancement of Science (AAAS), Washington, DC, 9(3):ade3491, (2023). https://doi.org/10.1126/sciadv.ade3491
Impact/Purpose:
Riverine dissolved organic carbon (DOC) fluxes have increased dramatically in many waterbodies in northern industrialised regions over recent decades. These trends have been linked to the increased solubility of soil organic matter since acid deposition began to decline in the 1970s, but persisting uncertainties over biogeochemical mechanisms and the potentially reinforcing or confounding influences of climate and land use change have hampered attempts to scale up and predict future behaviour. Here we demonstrate that DOC has been rising exponentially in fixed inverse proportion to reductions in ionic strength (IS) in a wide range of northern European and North American headwaters subject to reductions in sulphur deposition. This manuscript contributes to SSWR 1.1A.
Description:
The riverine dissolved organic carbon (DOC) flux is of similar magnitude to the terrestrial sink for atmospheric CO2, but the factors controlling it remain poorly determined and are largely absent from Earth system models (ESMs). Here, we show, for a range of European headwater catchments, that electrolyte solubility theory explains how declining precipitation ionic strength (IS) has increased the dissolution of thermally moderated pools of soluble soil organic matter (OM), while hydrological conditions govern the proportion of this OM entering the aquatic system. Solubility will continue to rise exponentially with declining IS until pollutant ion deposition fully flattens out under clean air policies. Future DOC export will increasingly depend on rates of warming and any directional changes to the intensity and seasonality of precipitation and marine ion deposition. Our findings provide a firm foundation for incorporating the processes dominating change in this component of the global carbon cycle in ESMs.
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DOI: Long-term rise in riverine dissolved organic carbon concentration is predicted by electrolyte solubility theory