9Purpose The study develops site-dependent Characterization Factors (CFs) for marine ecotoxicity of metals emitted to 10 freshwater, taking their passage of the estuary into account. To serve LCA studies where emission location is often 11 unknown, site-generic marine CFs were developed for metal emissions to freshwater and coastal seawater respectively. 12The new CFs were applied to calculate endpoint impact scores for the same amount of metal emission to each 13 compartment, to compare the relative ecotoxicity damages in freshwater and marine ecosystems in LCA. 14 Methods Site-dependent marine CFs for emission to freshwater were calculated for 64 comparatively independent seas 15 (Large Marine Ecosystems, LMEs). The site-dependent CF was calculated as the product of Fate Factor (FF), 16Bioavailability Factor (BF) and Effect Factor (EF). USEtox modified with site-dependent parameters was extended with 17 an estuary removal process to calculate FF. BF and EF were taken from Dong et al. (2016). Site-generic marine CFs were 18 derived from site-dependent marine CFs. Different averaging principles were tested, and the approach representing 19 estuary discharge rate was identified as the best one. Endpoint marine and freshwater metals CFs were developed to 20 calculate endpoint ecotoxicity impact scores. 21Results and discussion Marine ecotoxicity CFs are 1.5 orders of magnitude lower for emission to freshwater than for 22 emission to seawater for Cr, Cu and Pb, due to notable removal fractions both in freshwater and estuary. For the other 23 metals, the difference is less than half an order of magnitude, mainly due to removal in freshwater.