Chemical profiles of water in the vadose zone and in the upper part of the groundwater from a water-table sand-silt aquifer at Haslemoen, South Norway, have been studied. Filter tips attached to steel pipes (BAT monitoring system) have been installed to different depths at two localities. The system makes it possible to measure pore pressures and hydraulic conductivities and to take samples under controlled conditions both above and below the groundwater level. One locality is characterized by forest, groundwater level at about 7 m below surface, and filter tips down to 13.2 m. Agricultural land surrounds the field installations at the other locality, the groundwater level is here about 4.5 m below surface, and filter tips are down to 10.4 m.

The chemical data demonstrate a) Higher concentrations of both total nitrogen and nitrate below agricultural land b) Decreasing concentrations downwards of both total nitrogen and nitrate in both profiles c) Iron and/or organic carbon seems to take part in the reduction of nitrate, probably to free nitrogen.