An error in the units used for Ag sediment concentration (µg Ag kg-1 instead of mg Ag kg-1) in eqn (3) and (4) resulted in the units for sediment uptake being wrongly presented as gsediment gorganism -1 per day rather than kgsediment gorganism -1 per day in the original Table 2. Correcting these units changes the interpretation of the data slightly, as such high uptake rate constants suggest that the Ag concentrations in the sediment were probably too low to explain uptake, and thus uptake through water was probably more important. The modelling using model 2 was redone, leading to different values of kw, although the values for ks, k2 or SF reported in the original Table 2 were not affected. With these new calculations, the units for ks were maintained as gsediment gorganism -1 per day. The unit for Ag sediment concentrations used in model 4 (eqn (7) and (8)) was also µg Ag kg-1, so the unit of k1 was wrongly presented as gsediment gorganism -1 per day in the original Table 2 but is changed now to kgsediment gorganism -1 per day. The new values and corrected units are shown in the revised Table 2 below. The new kw (uptake from water) values are highest for the exposures to Ag2S-NPs (3.15 Lwater gorganism -1 per day) and 60 nm Ag-NPs (2.19 Lwater gorganism -1 per day), followed by AgNO3 (1.88 Lwater gorganism -1 per day). The new kw values, however, did change our conclusion regarding the contribution of uptake from water and sediment to the total Ag uptake, and thus the values in the original Table 3 are incorrect and should not be considered anymore. Redoing the estimate showed that, at the low sediment concentrations in the water-spiked test, for all Ag forms nearly 100% of the Ag measured in the animals was from the water, with less than 0.1% coming from the sediment. The new values are shown in the revised Table 3 below. These new calculations particularly affected the conclusion of sediment being a more important uptake route for Ag2S-NPs by the snails, which is no longer valid. It should also be noted that the units of k1 for sediment as a single exposure route (model 4) changed, with Ag2S-NPs and AgNO3 presenting the highest k1 values (1.88 kgsediment gorganism -1 per day and 2.05 kgsediment gorganism -1 per day, respectively). These k1 values considering sediment as the only exposure route are much higher than the ones obtained in the test with Ag-spiked sediment, due to the fact that uptake was mainly from water because of the very low sediment concentrations in this test with spiked water and clean sediment. As explained above, uptake from water is the dominant process. In the Abstract, the sentence “When considering the double exposure route, which provides a more realistic contamination scenario, water was the main route, except for Ag2S-NPs, for which sediment was more important” should be replaced with “When considering the double exposure route, which provides a more realistic contamination scenario, water was the main route”. In the Conclusions, the section: “When accounting for double exposure via both water and sediment, water was likely to be the main route. Interestingly, the simulated aged Ag-NP form (Ag2S-NPs) revealed analogous kinetics in experiments that considered sediment as exposure route, which points to a higher influence of the sediment for Ag2S-NPs. This was also supported by the higher contribution to Ag uptake from sediment determined for Ag2S-NP. Moreover, Ag2S-NPs were not only highly available to snails but were also easily depurated” should be replaced with: “When accounting for double exposure via both water and sediment, water was the main route for all Ag forms tested. Moreover, Ag2S-NPs were not only highly available to snails but were also easily depurated”. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
ASJC Scopus subject areas
- Materials Science (miscellaneous)
- Environmental Science(all)