Environmental Isotopes as Indicators for Ground Water Recharge to Fractured Granite

To assess the contribution of accumulated winter precipitation and glacial meltwater to the recharge of deep ground water flow systems in fracture crystalline rocks, measurements of environmental isotope ratios, hydrochemical composition, and in situ parameters of ground water were performed in a deep tunnel. The measurements demonstrate the significance of these ground water recharge components for deep ground water flow systems in fractured granites of a high alpine catchment in the Central Alps, Switzerland. Hydrochemical and in situ parameters, as well as d18O in ground water samples collected in the tunnel, show only small temporal variations. The precipitation record of d18O shows seasonal variations of ~14‰ and a decrease of 0.23‰ ± 0.03‰ per 100 m elevation gain. d2H and d18O in precipitation are well correlated and plot close to the meteoric water line, as well as d2H and d18O in ground water samples, reflecting the meteoric origin of the latter. The depletion of 18O in ground water compared to 18O content in precipitation during the ground water recharge period indicates significant contributions from accumulated depleted winter precipitation to ground water recharge. The hydrochemical composition of the encountered ground water, Na-Ca-HCO3-SO4(-F), reflects an evolution of the ground water along the flowpath through the granite body. Observed tritium concentrations in ground water range from 2.6 to 16.6 TU, with the lowest values associated with a local negative temperature anomaly and anomalous depleted 18O in ground water. This demonstrates the effect of local ground water recharge from meltwater of submodern glacial ice. Such localized recharge from glaciated areas occurs along preferential flowpaths within the granite body that are mainly controlled by observed hydraulic active shear fractures and cataclastic faults.

Misonidazole binding in murine liver tissue: a marker for cellular hypoxia in vivo

The hepatic microcirculation is believed to cause variable cellular oxygenation within the organ. In this study a marker of cellular hypoxia was used to demonstrate liver oxygen tension gradients in vivo. Covalent binding of misonidazole adducts to cellular macromolecules is enhanced by hypoxia. Autoradiographs of liver from mice treated with radiolabeled misonidazole demonstrated enhanced binding of adducts within hepatocytes surrounding hepatic veins. Livers from both hypoxic and normal mice had characteristic autoradiographic grain patterns reflecting regional oxygen tension variation in vivo. Differential binding of misonidazole adducts formed in hypoxic cells could have an application in studies of liver physiology and biochemistry.