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Characterisation Method Information
Characterisation Method Name:
SO2 impact on base cat-ion capacity
Version:
1999
Date Completed:
1999
Principal Method Name:
EPS: acidification pathway
Method Description:
Model

The characterisation factor is determined by a mechanistic method.

Mechanism

When sulphur dioxide is oxidised in air, two protons (H + ) are produced per mole of SO2.
When the oxidised S in form of sulphate is deposited on soil, the protons will substitute base cat-ions, e.g Mg ++ or K + , which are important nutrient to plants.

Portion of emitted substance that will reach target

On a global scale the critical load for soil acidification is exceeded on approximately 10% of the land area. As much of the SO2 sources are located near the sea, part of the emissions is deposited in the oceans and in inland water. As the average residence time is in the order of a week and the corresponding air transport of several 1000 km, it is reasonable to assume that 50% of the S is deposited at land. This means that approximately 5% of the SO2 cause base cat-ion depletion.

Calculation of characterisation factor

For each kg of SO2 there is thus 2*1000*0.05/64 = 1.56 equivalents of base cat-ions reserves depleted.

Literature Reference:
Steen B (1999b): A systematic approach to environmental priority strategies in product development (EPS). Version 2000 Models and data of the default method CPM report Chalmers University of Technology Sweden
Methodological Range:
The system is global and the time period is 1990.
Notes:

Existing Characterisation Factors of SO2 impact on base cat-ion capacity
Characterisation Parameter Category Indicator Impact Indication Principle Aspect Substance Quantity Unit Notes
CFactor Base cat-ion capacity EPS/2000
Type = Emission
Direction = Output
Media = Air
Geography = *
SO2 1.56 H+ mole equivalence/kg acidification pathway