Riparian zone hydrology and soil water total organic carbon (TOC): implications for spatial variability and upscaling of lateral riparian TOC exports

[摘要] Groundwater flowing from hillslopes through riparian (near-stream) soilsoften undergoes chemical transformations that can substantially influencestream water chemistry. We used landscape analysis to predict total organiccarbon (TOC) concentration profiles and groundwater levels measured in theriparian zone (RZ) of a 67 km² catchment in Sweden. TOC exportedlaterally from 13 riparian soil profiles was then estimated based on theriparian flow–concentration integration model (RIM). Much of the observedspatial variability of riparian TOC concentrations in this system could bepredicted from groundwater levels and the topographic wetness index (TWI).Organic riparian peat soils in forested areas emerged as hotspots exportinglarge amounts of TOC. These TOC fluxes were subject to considerable temporalvariations caused by a combination of variable flow conditions and changingsoil water TOC concentrations. Mineral riparian gley soils, on the otherhand, were related to rather small TOC export rates and were characterizedby relatively time-invariant TOC concentration profiles. Organic and mineralsoils in RZs constitute a heterogeneous landscape mosaic that potentiallycontrols much of the spatial variability of stream water TOC. We developedan empirical regression model based on the TWI to move beyond the plot scaleand to predict spatially variable riparian TOC concentration profiles forRZs underlain by glacial till.

[学科分类] 地球化学与岩石