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Characterisation Method Information
Characterisation Method Name:
Contributions to EF(ac)
Version:
1997
Date Completed:
1997
Principal Method Name:
EDIP: acidification potential
Method Description:
When acids and compounds which can be converted to acids are emitted to the atmosphere and deposited in water and soil, the addition of hydrogen ions may eventually result in a decrease in pH, i.e. an increase in acidity. This has consequences in the form of a widespread decline of coniferous forests in many places in Europe and the USA, and increased fish mortality in mountain lakes in Scandinavia and central Europe. Corrosion damage to metals and disintegration of surface coatings and mineral building materials are also caused by acidification on exposure to wind and weather. The most significant man-made sources of acidification are combustion processes in electricity and heating production, and transport. The contribution to acidification is greatest when the fuels used contain sulphur.

Acidification is an impact which mainly affects the environment on a regional scale.

1 Determine which substances contribute to
acidification

For a substance to be considered a contributor to acidification:
it must cause introduction or release of hydrogen ions in the environment, and
the anions which accompany the hydrogen ions must be leached or washed out from the system.

The addition of hydrogen ions occurs either when the substance itself is an acid or is converted to an acid, or when hydrogen ions are released as the substance is converted in the environment.

Acidification can be caused by emissions to air, water and soil. The number of substances which should be considered contributors to acidification is not large, and in practice the list of equivalency factors in right side can be used to decide whether a substance contributes to acidification. Note that emission of organic acids is not regarded as a contribution to acidification.

2 Calculate the acidification potential

There is no internationally accepted system of equivalency factors for acidifying substances. In contrast to the global environmental impacts and photochemical ozone formation, it has therefore been necessary in the EDIP programme to develop equivalency factors for acidification.


Calculation of the equivalency factor for a substance is based on the number of hydrogen ions which can theoretically be released from the substance directly or after any conversions in the environment.
Whether or not the acidification potential is
realized depends, as noted, on the accompanying anion release from the ecosystem which receives the emission. For some substances, the proportion of anions released can vary from ecosystem to
ecosystem. To reflect this, Hauschild & Wenzel (1997b) propose a site factor, the value of which can vary between 0 and 1.
As for the potentials for the other types of
environmental impacts, the acidification potential is exnressed as an equivalent quantity of a reference substance. Sulphur dioxide (SO,) is used as the reference substance for acidification. Should the inventory include compounds causing acidification other than those shown in right side, it is easy to calculate
equivalency factors for them. The method is given in Hauschild & Wenzei (1997b).



Literature Reference:
Henrik Wenzel, Michael Hauschild and Leo Alting (1997 ): Environmental assessment of products Vol. 1 Methodology, tools and case studies in product development London Chapman & Hall
Methodological Range:
Geographical range is Global
Notes:

Existing Characterisation Factors of Contributions to EF(ac)
Characterisation Parameter Category Indicator Impact Indication Principle Aspect Substance Quantity Unit Notes
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
H2S 1.88 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
H2SO4 0.65 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
H3PO4 0.98 g/g
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
HCl 0.88 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
HF 1.60 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
HNO3 0.51 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
NH3 1.88 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
NO 1.07 g/g
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
NO2 0.7 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
NOx 0.7 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
SO2 1 kg/kg
CFactor EF(ac) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
SO3 0.80 kg/kg