Distribution of stable isotope values in groundwater in Northwestern Germany-Evaluation of continental, altitude and land use effects

摘要

This study provides an overview of the distribution of stable isotopes of hydrogen (delta H-2) and oxygen (delta O-18) in groundwater of Lower Saxony and Bremen through the analysis of 133 groundwater samples using cavity ring-down spectroscopy. Results show a continental effect in the northwest-southeast direction along the prevailing wind direction, characterized by a depletion of the water isotope signal with increasing distance from the coastline (delta H-2: -48.3 parts per thousand; delta O-18: -6.8 parts per thousand) into the back-country (delta H-2: -56.8 parts per thousand; delta O-18: -7.8 parts per thousand). The potential appearance of an altitude effect is observed over a large distance and is thus most likely not a real feature but caused by the continental effect. Furthermore, we observed a dependence of water isotope values on the evaporation rate, which itself largely depends on soil porosity and plant growth and is caused by differences in land use and in hydrogeological conditions. The latter effects have a mutual impact on each other and are also overprinted by the continental effect.