Uncertainty and spatial variability in characterization factors for aquatic acidification at the global scale

Abstract

Purpose Characterization factors (CFs) quantifying the potential impact of acidifying emissions on inland aquatic environments in life cycle assessment are typically available on a generic level. The lack of spatial differentiation may weaken the relevance of generic CFs since it was shown that regional impact categories such as aquatic acidification were influencedbythesurroundingsoftheemissionlocation.Thispaper presents a novel approach for the development of spatially differentiatedCFsata globalscalefor theaquatic acidification impact category. Methods CFs were defined as the change in relative decrease of lake fish species richness due to a change in acidifying chemicals emissions. The characterization model includes the modelling steps linking emission to atmospheric acid deposition (atmospheric fate factor) change, which lead to lake H + concentration (receiving environment fate factor) change and a decrease in relative fish species richness (effect factor). We also evaluated the significance of each factor (i.e. atmospheric fate, receiving environment fateand effects)tothe overall CFs spatial variability and parameter uncertainty. Results and discussion The highest CFs were found for emissions occurring in Canada, Scandinavia and the northern central Asia because of the extensive lake areas in these regions (lake areas being one of the parameters of the CFs; the bigger the lake areas, the higher the CFs). The CFs’spatial variability ranged over 5, 6 and 8 orders of magnitude for NOx ,S O2 and NH3 emissions, respectively. We found that the aquatic receiving environment fate factor is the dominant contributor to the overall spatial variability of the CFs, while the effect factors contributed to 98 % of the total parameter uncertainty.