Biological and non-biological turnover of anthropogenic nitrogen in a remote aquifer

摘要

Nitrogen sinks in the subsoil are usually ascribed to plant uptake and denitrification. However, there is strong evidence that other processes might play an important role as well. Turnover of anthropogenic non-point source pollutants has been extensively investigated at the forested Lehstenbach Watershed in south Germany. It has been shown that denitrification occurs only locally. However, nitrate concentration in the groundwater significantly decreases with increasing residence time in spite of oxygen saturation. It is clearly anticorrelated with silicon concentration. Mean residence time of the groundwater is about four years. Nitrogen input has been fairly constant during the last 12 years at least. It is concluded that most of the nitrogen loss in the watershed is due to a substantial sink in the deeper aquifer. Future research will focus on identifying this sink.