Excess nitrogen leaching and C/N decline in the Tillingbourne catchment, southern England: INCA process modelling for current and historic time series

P. G. Whitehead (1) , D. J. Lapworth (2) , R. A. Skeffington (1) , A. Wade (1)

1 Aquatic Environments Research Centre
2 BGS - British Geological Survey

Measurements of nitrate deposition and streamwater chemistry in the Tillingbourne Catchment, in Southern England, made in 1979-1982 and 1999-2001 show a 216% increase in Nitrogen leaching despite a reduction in N inputs. Both the historical and current data sets have been modelled using the Integrated Nitrogen Model in Catchments (INCA). The process-based model is shown to reproduce the historical patterns of N release from the catchment. However, modelling the increased leaching of N during recent years required an increase of the mineralisation control parameter in the model, suggesting enhanced mineralisation rates. Comparing historic and current soils data for C/N ratios shows that there has been a reduction in C/N from 38 to 26% in the humus layer and a reduction from 33 to 26% in the mineral soil horizon. This significant fall in C/N is consistent with the increase in N saturation in the H and Ah horizons of the major catchment soil.

Keywords: acid deposition, recovery, nitrogen, Carbon-Nitrogen ratios, Tillingbourne, Thames, catchment studies, nutrient leaching, modelling

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

P. G. Whitehead, D. J. Lapworth, R. A. Skeffington, A. Wade. Excess nitrogen leaching and C/N decline in the Tillingbourne catchment, southern England: INCA process modelling for current and historic time series. Hydrology and Earth System Sciences Discussions, 2002, 6 (3), pp.455-466. ⟨hal-00304705⟩