Long-term nitrate increases in two oligotrophic lakes, due to the leaching of atmospherically-deposited N from moorland ranker soils.
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).
Tipping
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Centre for Ecology and Hydrology Lancaster, Lancaster Environment Centre, Bailrigg, Lancaster LA1 4AP, UK. et@ceh.ac.uk
Thacker
S A
SA
Wilson
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D
Hall
J R
JR
D000327:Adsorption; D000393:Air Pollutants / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D004739:England; D004784:Environmental Monitoring / Q000379:methods*; D004787:Environmental Pollution / Q000032:analysis*; D005308:Fertilizers; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis; D012987:Soil / Q000032:analysis; D013995:Time; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D000393:Air Pollutants; D005308:Fertilizers; D009566:Nitrates; D012987:Soil; D014874:Water Pollutants, Chemical; D002244:Carbon; D009584:Nitrogen