Quantification of the increase in Pb bioavailability to marine organisms caused by different types of DOM from terrestrial and river origin

► Fulvic acids (FA) and dissolved organic matter from river origin (SRDOM) increased the toxicity of Pb to sea-urchin embryos. ► Results are compared with previous studies of DOM effects on Pb bioavailability to other marine organisms. ► An f ratio comparing the theoretical effect of PbDOM to that of inorganic Pb quantifies the effect of DOM on Pb bioavailability. ► f ratio was higher for humic acids (HA), followed by SRDOM and FA for the three organisms tested. ► Physicochemical properties of DOM, which control their adsorption to surfaces, may be responsible of DOM effects on Pb uptake and toxicity.