Environmental isotopes, such as oxygen-18 and deuterium, have been used increasingly to separate stormflow into its event and pre-event components in order to elucidate the sources, pathways and re...

Isotope hydrograph separations and rapid delivery of pre-event water from drainage basins:

Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem re- search is increasing. In this review we introduce and dis- cuss the relevant details underlying the use of carbon and oxygen isotopic compositions in ecosystem gas ex- change research. The current use and potential develop- ments of stable isotope measurements together with con- centration and flux measurements of CO2 and water va- por are emphasized. For these applications it is critical to know the isotopic identity of specific ecosystem compo- nents such as the isotopic composition of CO 2 , organic matter, liquid water, and water vapor, as well as the associated isotopic fractionations, in the soil-plant- atmosphere system. Combining stable isotopes and con- centration measurements is very effective through the use of "Keeling plots." This approach allows the identifi- cation of the isotopic composition and the contribution of ecosystem, or ecosystem components, to the exchange fluxes with the atmosphere. It also allows the estimation of net ecosystem discrimination and soil disequilibrium effects. Recent modifications of the Keeling plot ap- proach permit examination of CO2 recycling in ecosys- tems. Combining stable isotopes with dynamic flux mea- surements requires precision in isotopic sampling and analysis, which is currently at the limit of detection. Combined with the micrometeorological gradient ap- proach (applicable mostly in grasslands and crop fields), stable isotope measurements allow separation of net CO 2 exchange into photosynthetic and soil respiration compo- nents, and the evapotranspiration flux into soil evapora- tion and leaf transpiration. Similar applications in con- junction with eddy correlation techniques (applicable to forests, in addition to grasslands and crop fields) are more demanding, but can potentially be applied in com- bination with the Keeling plot relationship. The advance and potential in using stable isotope measurements should make their use a standard component in the limit- ed arsenal of ecosystem-scale research tools.

The use of stable isotopes to study ecosystem gas exchange.

https://nature.berkeley.edu/classes/espm-c220/barnes.pdf

Tracing of water movement in the unsaturated zone using stable isotopes of hydrogen and oxygen

A portion of the Gambier Plain underlain by an unconfined aquifer with readily definable hydrologic boundaries has been divided into a number of areas within which soil types have similar hydrologic properties. Mean annual recharge has been estimated for each area using both the tritium concentration and the chloride concentration of water within the soil profile. Good agreement was obtained between the two methods with local recharge varying between 50 and 250 mm year-1. Total mean annual recharge for the area has been estimated to be 2.4 ± 0.3 x 108 m3 year-1, and this compares favourably with an estimated discharge of 2.5 ± 0.3 x 108 m3 year-1.

The use of environmental chloride and tritium to estimate total recharge to an unconfined aquifer

Funded by DFG research project “From Catchments as Organised Systems to Models based on Functional Units” (FOR 1

/pdf/illuminating-hydrological-processes-at-the-soil-vegetation-3so6gh133c.pdf

Illuminating hydrological processes at the soil-vegetation-atmosphere interface with water stable isotopes

Downward Movement of Soil Moisture Traced by Means of Hydrogen Isotopes

The downward movement of water in soil is a layered one. Marking a certain layer with hydrogen-isotope tracer, and watching its displacement, makes possible a water balance and gives information on evaporation and groundwater recharge.

W. Roether

Papers

Downward Movement of Soil Moisture Traced by Means of Hydrogen Isotopes

Tracers determine movement of soil moisture and evapotranspiration.