a spatially differentiated life cycle impact assessment method

Photochemical Ozone Formation

Ecosystem quality

Photochemical Ozone Formation

Air pollution causing tropospheric ozone in the atmosphere can have a negative impact on human health, e.g. respiratory problems, and terrestrial ecosystems, e.g. plant biomass decrease.

Cause-effect pathway

The impact model is addressing emissions of nitrogen oxides (NOx), and non-methane volatile organic compounds (NMVOC) and consequent effects on the Areas of protection ‘Human Health’ and ‘Terrestrial ecosystems’. This overview will focus on the effects on ecosystems quality only.

Modeling approach

A marginal approach for calculating the characterization factors is followed, meaning that the additional impact of a marginal increase in ozone precursor emission using today’s situation as the reference state was determined. Model results were determined following a change in anthropogenic emissions and is determined by lowering the year 2000 emissions by 20% for each of the 56 source regions. Impact is measured in disability adjusted life years for human health (DALYs) for human health and potentially disappeared fraction of species over time for terrestrial ecosystems.

Value choices

Time Horizon: not of importance as only short-living substances are involved.

Spatial variability

The method was applied to 56 world regions. Country-average CFs were determined from these region-specific factors. A global average is not considered meaningful but provided for background processes.

Characterisation factors

The endpoint characterisation factors (CFs for ecosystem damage due to ozone formation caused by emitted precursor substance x in world region i (CFx,i in PDF·yr·kg-1) are defined as the area-integrated change in Potentially Disappeared Fraction (PDF) of forest and natural grassland species due to a change in emission of substance x in source region i (dMx,i in kg·yr-1). This CF for ecosystem damage is composed of a Fate Factor (FFx,i→g, unit: ppm·h·yr·kg-1), quantifying the relationship between the emission of precursor substances in region i and ozone exposure in receiving grid cell g, and an Effect Factor (EFn,j in PDF· ppm-1·h-1), quantifying the relationship between ozone exposure and the damage to natural vegetation n (forest and grassland). In equation this reads:

$$\mathsf{CF_{ECO,x,i}=\sum_g\sum_n{(FF_{x,i\to g}\cdot EF_{n,g})}}$$