Investigating the Uncertainties in the Simple Mass Balance Equation for Acidity Critical Loads for Terrestrial Ecosystems in the United Kingdom

The Simple Mass Balance (SMB)equation has been developed and used as one ofthe principal methods for calculating criticalloads of acidity for forest ecosystems. Criticalloads have formed the basis for informing policyrelated to the control and abatement of emissionsof acidifying pollutants. The SMB equationrelies on a variety of assumptions and dataderived from a variety of sources. Each of thesecomponent constituents has a potential source oferror depending on the method(s) used for theirderivation and the value(s) assigned. The resultis the possibility of generating a range ofcritical load values for a single ecosystem. This paper summarises the SMB equation, examinesthe uncertainties in deriving input values andreviews other works on the key assumptions.

[1]  Mnv,et al.  Calculation and Mapping of Critical Thresholds in Europe: Status Report 1999 , 1999 .

[2]  M. Hodson,et al.  a critical evaluation of the use of the PROFILE model in calculating mineral weathering rates , 1997 .

[3]  D. F. Grigal,et al.  Use of Calcium/Aluminum Ratios as Indicators of Stress in Forest Ecosystems , 1995 .

[4]  M. Coull,et al.  The calculation of base cation release from the chemical weathering of Scottish soils using the profile model , 1995 .

[5]  H. Sverdrup,et al.  Weathering of primary silicate minerals in the natural soil environment in relation to a chemical weathering model , 1988, Water, Air, and Soil Pollution.

[6]  Dale W. Johnson,et al.  The Effects of Acidic Deposition on Forested Soils , 1992 .

[7]  D. C. Bain,et al.  A preliminary review of weathering rates in relation to their method of calculation for acid sensitive soil parent materials , 1995 .

[8]  M. Hodson,et al.  Considerations of uncertainty in setting critical loads of acidity of soils: the role of weathering rate determination. , 1999, Environmental pollution.

[9]  W. Vries,et al.  Calculating critical loads for acidity with the simple mass balance method , 1994 .

[10]  P. Loveland,et al.  An empirical map of critical loads of acidity for soils in Great Britain. , 1995, Environmental pollution.

[11]  Harald Sverdrup,et al.  Mapping critical loads : a guidance to the criteria, calculations, data collection and mapping of critical loads , 1990 .

[12]  B. Ulrich,et al.  Interaction of Forest Canopies with Atmospheric Constituents: So 2 , Alkali and Earth Alkali Cations and Chloride , 1983 .

[13]  D. C. Bain,et al.  The calculation of base cation release from mineral weathering in soils derived from Palaeozoic greywackes and shales in upland UK , 1996 .

[14]  P. Loveland,et al.  The sensitivity of surface waters of Great Britain to acidification predicted from catchment characteristics. , 1995, Environmental pollution.

[15]  Hettelingh Jp,et al.  Calculation and mapping of critical loads in Europe: Status Report 1993. CCE report , 1993 .