Spatial aspects affecting acidification factors in European acidification modelling

Plain linear models have recently been used in methodologies to model fate and transport for assessing acidification in life cycle impact assessment (LCIA), or in support of air pollution abatement policies. These models originate from a statistical analysis of the relationship between inputs and outputs of physically-based models that reflect the mechanics of a system in detail. Linear models applied to assess acidification use an acidification factor (AF), which relates changes in the magnitude of emissions to changes in the total area that is protected against acidification in Europe. The changes in emission volume refer to changes of one substance, within one country and one sector or one grid cell.This paper evaluates the dependence of AFs on three spatial characteristics, i.e. the spatial emission and deposition resolution, the spatial emission distribution and the actual spatial location of emissions.The applied spatial resolutions of emission and deposition cause non-systematic variations in AFs of up to 60%, relative to the finest resolution. The manner in which the distribution of emissions is modelled, i.e. grid or sector-specific, is shown to affect AFs considerably, as well. We conclude that spatial characteristics of the physically-based acidification model can affect the assessment of acidification by means of plain linear models.