Perennial flow through convergent hillslopes explains chemodynamic solute behavior in a shale headwater catchment

摘要: Abstract Stream chemistry reflects the mixture of complex biogeochemical reactions that vary across space and time within watersheds. For example, streams experience changing hydrologic connectivity to heterogeneous water sources under different flow regimes; however, it remains unclear how seasonal paths link these regulate concentration-discharge behavior, i.e., changes in stream solute concentration as a function discharge. At Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) central Pennsylvania, USA, concentrations chemostatic solutes (K, Mg, Na, Si, Cl) little wide range discharge values while chemodynamic (Fe, Mn, Ca) decrease sharply with increasing To elucidate controls on we investigated surface shallow subsurface at SSHCZO early autumn when was negligible were high. Dissolved ions, colloids, micron-sized particles extracted from hillslope soils sediments evaluate elements mobilized into pore waters transported hillslopes stream. During study period intermittent, consisted isolated puddles chemically variable along length channel. Inputs limited an area upwelling near headwaters, table remained over meter below bed rest Chemodynamic Fe Mn preferentially organic-rich dissolved particles; consequently, draining upper catchment enriched Mn. Conversely, Ca increased towards outlet primarily Ca2+. Concentrations relatively invariable throughout catchment. We conclude behavior is driven by seasonally between soils. dry season, derives perched (interflow) upwells generate metal-rich headwaters. High soluble low occur headwaters are flushed during periodic rain events. Interflow season originates infiltrates through swales; thus, metals ultimately derived convergent where biological processes have concentrated and/or elements. In contrast, high Ca2+ likely contain secondary calcite precipitates. infer diluted due planar hillslopes. This highlights spatially biogeochemistry catchments.