Spatial and Temporal Patterns of Alkalinity in an Alpine Headwater Stream Network: Linking Catchment Heterogeneity to Carbon Dynamics

Abstract Alkalinity is a key regulator of carbon dioxide () dynamics in freshwater systems, influencing both dissolved inorganic carbon speciation and the buffering capacity of water. Despite its importance, alkalinity in freshwater environments remains comparatively underexplored relative to ocean systems. Here, we investigate alkalinity dynamics in an alpine stream network in the Dolomites (Italy) by sampling 15 sites at different temporal resolutions. Results indicate that alkalinity varies markedly across the network, ranging from approximately 1.9 to 4.3 mEq , whereas seasonal and diel fluctuations are less pronounced. By combining alkalinity and discharge measurements, we estimated the alkalinity of lateral inflows through a mass‐balance approach and related it to catchment characteristics using a land use regression model, which identified three geological formations (Val Gardena sandstones, Gastropod Oolites Member, and Bellerophon Formation) as primary controlling factors, achieving an adjusted of 0.78 (cross‐validated = 0.73). Furthermore, we propose a general framework for predicting in‐stream alkalinity throughout the network by integrating the regression model with spatial estimates of lateral flow, providing a useful tool for studies of alkalinity and the related carbon dynamics in stream networks. Our findings underscore the importance of accounting for spatial variability in alkalinity when assessing carbon cycling in fluvial networks, particularly in mountain regions where geological features strongly influence carbon processing.