Concepts

Human-induced nitrogen input that has doubled biologically-available nitrogen on Earth

Shallow subsurface zone where river and groundwater mix, serving as a source or sink of reactive nitrogen depending on water residence times and nitrogen transformation rates

Organic carbon derived from sedimentary rocks that is often poorly quantified and influences soil organic carbon composition, age, and stability

Spatial variability in biogeochemical processes and solute sources within watersheds, particularly between shallow soil zones and deeper groundwater zones

The relationship between solute concentrations and discharge in streams, widely used as a metric for interpreting interaction of hydrological processes, chemical transport, and mineral reactions in wa...

Areas of disproportionately high biogeochemical activity or export relative to surrounding landscape

Redox-stratified and temporally dynamic sediments in river corridors where biological processes mediate sulfur transformations

Concentration-discharge pattern where solute concentrations remain relatively constant across flow conditions, indicated by C-Q slope near zero

Spatial variations in oxidation-reduction conditions within floodplain environments that can form within microsites, along textural transitions, or along the capillary fringe

The association of uranium with different solid-phase mineral forms that influences uranium mobility between solid and water phases

Zone of active mineral dissolution and precipitation reactions that advances through bedrock over time

Different trajectory of C-Q relationships during rising and falling limbs of hydrographs that indicate differences in timing of hydrological response from surface and subsurface compartments

Subsurface conditions where chemical transport is limited to diffusion rather than advection, creating oxygen-depleted anoxic conditions

Unsaturated zone above the water table where pore spaces contain both air and water