[1] Unsaturated zone salt reservoirs are potentially mobilized by increased groundwater recharge as semiarid lands are cultivated. This study explores the amounts of pore water sulfate and fluoride relative to chloride in unsaturated zone profiles, evaluates their sources, estimates mobilization due to past land use change, and assesses the impacts on groundwater quality. Inventories of water-e...

Nitrate (NO3) profiles in semiarid unsaturated zones archive land use change (LUC) impacts on nitrogen (N) cycling with implications for agricultural N management and groundwater quality. This study quantified LUC impacts on NO3 inventories and fluxes by measuring NO3 profiles beneath natural and rainfed (nonirrigated) agricultural ecosystems in the southern High Plains (SHP). Inventories of NO...

A large reservoir of bioavailable nitrogen (up to approximately 10(4) kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of arid regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for wa...

Perchlorate (Cl4-) reservoirs that accumulated in semiarid unsaturated zones, similar to chloride (Cl-), can contaminate underlying aquifers if they are mobilized. The purpose of this study was to evaluate Cl)4- mobilization related to land-use change from natural to agricultural ecosystems in the southern High Plains (SHP, USA), where large ClO4- concentrations (< or =60 microg/L) are found in...

Nitrogen in different forms is naturally available in abundance in the atmosphere. Excess nitrogen, however, has gradually become the one cause for the most pressing environmental problems we currently face in various regions of the world, since the Haber-Bosch process has made the industrial scale production of nitrogen fertilisers possible. Interactions between the drivers, namely emissions o...

Abstract Large-scale studies of the spatial and temporal variation groundwater drought status require complete inventories levels on regular time steps from many sites so that a standardised index can be calculated for each site. However, are often measured sporadically, include missing or erroneous data. A flexible efficient modelling framework is developed to fill gaps regularise data in such...

The production of corn or soybeans for bio-based fuels and materials requires significant inputs of nitrogen (FN) and phosphorus fertilizer (FP) to increase grain yields. Approximately 50% of these nutrients are integrated into plant biomass. The remaining 50% is volatilized, leached into surface and groundwater, or transformed into gaseous species such as N2, NO, or N2O. Recent efforts to comp...

A field experiment to compare methods of assessing submarine groundwater discharge (SGD) was held on Shelter Island, NY, in May 2002. We evaluated the use of radon, radium isotopes, and methane to assess SGD rates and dynamics from a glacial aquifer in the coastal zone. Fluxes of radon across the sediment-water interface were calculated from changes in measured surface water inventories followi...