Retention of nitrogen by peatland buffer zones at six forested catchments in Southern and Central Finland

摘要

Nitrogen retention capacity of six peatland buffer zone areas was studied by adding ammonium nitrate solution into inflow waters originating from forested catchments in Finland. The buffer zones were either pristine mires or drained peatlands which had been rewetted 10-12 years before the present study. Water samples were collected below the adding point of ammonium nitrate and from the waters flowing out from the buffer zones. The main factors controlling the retention of NO3-N and NH4-N were the size of the buffer zone area and runoff volume. The largest mires retained NO3-N almost completely, while one small-sized area with considerable discharge during the addition period had a retention capacity of NO3-N less than <15 %. NH4-N reduction was lower compared with NO3-N at each study site, yet the large sites retained NH4-N effectively. The release of added N occurred within a short period of time, except in one of the larger buffer areas, where NH4-N concentrations in outflow water rose significantly during the first autumn following N addition.