Long-term nitrate increases in two oligotrophic lakes, due to the leaching of atmospherically-deposited N from moorland ranker soils

• Published in: Environmental pollution (1987) 2008-03, Vol.152 (1), p.41-49
• Main Authors: Tipping, E., Thacker, S.A., Wilson, D., Hall, J.R.
• Format: Article
• Language: English
• Subjects: Adsorption; Air Pollutants - analysis; Applied sciences; Atmospheric deposition; Carbon - analysis; Continental surface waters; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; England; Environmental Monitoring - methods; Environmental Pollution - analysis; Exact sciences and technology; Fertilizers; Fresh Water; Hydrogen-Ion Concentration; Lakes; Leaching; losses from soil; meta-analysis; Natural water pollution; Nitrate; nitrate nitrogen; Nitrates - analysis; Nitrogen - analysis; Pollution; Pollution, environment geology; Soil - analysis; soil pollution; soil types; Soils; streams; Time; Water Movements; Water Pollutants, Chemical - analysis; water pollution; Water treatment and pollution; watersheds
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2007.06.001

During the last 50 years nitrate concentrations in Buttermere and Wastwater (Cumbria, UK) have risen significantly, by 70 and 100%, respectively. By estimating contemporary nitrate fluxes in the lakes' catchments and in sub-catchments and comparing them with the fractional areas of different soil types, it is deduced that the surface water nitrate is derived almost entirely from organic-rich ranker soils that have a limited ability to retain atmospherically-deposited nitrogen. Little or no nitrate leaches from the other major soil type, a brown podzol, despite it having a lower C:N ratio (12.0 g g −1) than the ranker (17.0 g g −1), nor is there much contribution from the small areas of improved (chemically fertilised) grassland within the catchments. Although some nitrate leaching is occurring, total N losses are appreciably smaller than atmospheric inputs, so the catchment soils are currently accumulating between 3 and 4 g N m −2 a −1. Increases in lakewater nitrate concentrations over 50 years are due to the limited ability of ranker soils to retain atmospherically-deposited nitrogen.