Trophic Transfer and Toxicity of (Mixtures of) Ag and TiO Nanoparticles in the Lettuce-Terrestrial Snail Food Chain.

The increasing application of biosolids and agrochemicals containing silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiONPs) results in their inevitable accumulation in soil, with unknown implications along terrestrial food chains. Here, the trophic transfer of single NPs and a mixture of AgNPs and TiONPs from lettuce to snails and their associated impacts on snails were investigated. Both AgNPs and TiONPs were transferred from lettuce to snails with trophic transfer factors (defined as the ratio of the Ag/Ti concentration in snail tissues to the Ag/Ti concentration in lettuce leaves) of 0.2-1.1 for Ag and 3.8-47 for Ti. Moreover, the majority of Ag captured by snails in the AgNP-containing treatments was excreted via feces, whereas more than 70% of Ti was distributed in the digestive gland of snails in the TiONP-containing treatments. Additionally, AgNP-containing treatments significantly inhibited the activity of snails, while TiONP-containing treatments significantly reduced feces excretion of snails. Furthermore, the concurrent application of AgNPs and TiONPs did not affect the biomagnification and distribution patterns of Ag and Ti in snails, whereas their co-existence exhibited more severe inhibition of the growth and activity of snails than in the case of applying AgNPs or TiONPs alone. This highlights the possibility of nanoparticle transfer to organisms of higher trophic levels via food chains and the associated risks to ecosystem health.