Chlorofluorocarbons CFC-11 (CCl(3)F), CFC-12 (CCl(2)F(2)), and CFC-113 (CCl(2)F-CClF(2)) are used in hydrology as transient tracers under the assumption of conservative behavior in the unsaturated and saturated soil zones. However, laboratory and field studies have shown that these compounds are not stable under anaerobic conditions. To determine the degradation rates of CFCs in a tropical envi...

Earthen waste lagoons are commonly used to store liquid wastes from concentrated animal feeding operations. The fate of ammonium (NH) and nitrate (NO) was studied in the vadose zone below earthen-clay dairy farm waste lagoons using three independent vadose zone monitoring systems. The vadose zone was monitored from 0.5 to 30 m below land surface through direct sampling of the sediment porewater...

Cholesterol in human bile is solubilized in micelles by (relatively hydrophobic) bile salts and phosphatidylcholine (unsaturated acyl chains at sn-2 position). Hydrophilic tauroursodeoxycholate, dipalmitoyl phosphatidylcholine, and sphingomyelin all decrease cholesterol crystal-containing zones in the equilibrium ternary phase diagram (van Erpecum, K. J., and M. C. Carey. 1997. Biochim. Biophys...

Journal of Environmental Hydrology Volume 17 Paper 7 February 2009 1 A parallelized large-scale regional hydrologic soil model (RHSM) is developed as a tool for large-scale unsaturated zone investigations. It is applied to simulate the temporal and spatial responses of the unsaturated zone and the regional water budget under the forcing of realistic precipitation and evaporation scenarios. The ...

A quasi three-dimensional (QUASI 3-D) model is presented for simulating the subsurface water flow and solute transport in the unsaturated and in the saturated zones of soil. The model is based on the assumptions of vertical flow in the unsaturated zone and essentially horizontal groundwater flow. The 1-D Richards equation for the unsaturated zone is coupled at the phreatic surface with the 2-D ...

A wide array of field observations, in situ testing, and rock and water sampling (and subsequent analyses) within the unsaturated zone (UZ) of Yucca Mountain demonstrate the importance of fractures to flow and transport in the welded tuffs. The abundance of fractures and the spatial variability in their hydraulic properties, along with the heterogeneity within lithologic formations, make evalua...

The unsaturated zone has a crucial role in subsurface processes that, turn, impact soil moisture, groundwater quality and quantity, ecosystem function [...]

While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system-internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure, and anothe...