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Carbonate buffering and metabolic controls on carbon dioxide in rivers
Author(s) -
Stets Edward G.,
Butman David,
McDonald Cory P.,
Stackpoole Sarah M.,
DeGrandpre Michael D.,
Striegl Robert G.
Publication year - 2017
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2016gb005578
Subject(s) - alkalinity , carbonate , carbon dioxide , carbon cycle , environmental chemistry , chemistry , dissolved organic carbon , total inorganic carbon , water quality , environmental science , streams , carbonic acid , carbonate minerals , nutrient , ocean acidification , seawater , ecology , geology , ecosystem , oceanography , organic chemistry , computer network , computer science , biology
Multiple processes support the significant efflux of carbon dioxide (CO 2 ) from rivers and streams. Attribution of CO 2 oversaturation will lead to better quantification of the freshwater carbon cycle and provide insights into the net cycling of nutrients and pollutants. CO 2 production is closely related to O 2 consumption because of the metabolic linkage of these gases. However, this relationship can be weakened due to dissolved inorganic carbon inputs from groundwater, carbonate buffering, calcification, and anaerobic metabolism. CO 2 and O 2 concentrations and other water quality parameters were analyzed in two data sets: a synoptic field study and nationwide water quality monitoring data. CO 2 and O 2 concentrations were strongly negatively correlated in both data sets ( ρ = −0.67 and ρ = −0.63, respectively), although the correlations were weaker in high‐alkalinity environments. In nearly all samples, the molar oversaturation of CO 2 was a larger magnitude than molar O 2 undersaturation. We used a dynamically coupled O 2 CO 2 model to show that lags in CO 2 air‐water equilibration are a likely cause of this phenomenon. Lags in CO 2 equilibration also impart landscape‐scale differences in the behavior of CO 2 between high‐ and low‐alkalinity watersheds. Although the concept of carbonate buffering and how it creates lags in CO 2 equilibration with the atmosphere is well understood, it has not been sufficiently integrated into our understanding of CO 2 dynamics in freshwaters. We argue that the consideration of carbonate equilibria and its effects on CO 2 dynamics are primary steps in understanding the sources and magnitude of CO 2 oversaturation in rivers and streams.