Nanomaterials across a salinity gradient: exposure and ecotoxicological effects within a life cycle perspective (production, usage, end of life) – nanoSALT

The current and foreseen applications of engineered nanomaterials (ENMs) embrace a wide range of technological domains and represent a significant economical fact. From 2006 to 2010 the number of nano-enabled products evolved from approximately 50 to more than 1300. Still now, a large number of uncertainties remain on the effects of ENMs towards human health, aquatic (lake, river, esturine, marine) and terrestrial environments.

Estimations give that 40 000 km3/year of freshwater flows into the worldwide oceans through the main rivers. The major part of this freshwater by-pass the Waste Water Treatment Plant. Consequently, the ENMs accidentally released or not (usage, end of life) in the aquatic environment will flow directly into the rivers. These ENMs will be transported by waters, sediments, and organisms until reaching estuarine or coastal areas. As the population density and economic activity in the coastal zone increases, several questions rise regarding the effects of these ENMs towards media represented by a salinity gradient or salted aquatic media (seawater). To date, several studies have focused on the impacts of ENMs towards freshwater organisms, whereas very few have concerned the impacts towards estuarine and marine organisms.
The aims of nanoSALT is to gather a maximum of disciplines from the three partners to elucidate using a holistic approach the principles governing ENMs behavior and ecotoxicity across a salinity gradient.

Moreover, in most of the industrial applications pristine nanoparticles are surface modified and embedded in the final product. It is unlikely that organisms living at the marine-continental interface will be in direct contact with pristine nanoparticles. So, there is an urgent need to assess the environmental fate of residues of degradation released from currently commercialized nano-products for which no data exists.
In nanoSALT, we selected two nano-enabled products based on relevance criteria: paints and textile containing nano-Ag and nano-CeO2. It is anticipated that weathering/leaching will occur with time, resulting in environmental discharge of nano-residues. Chronic and low doses of these aged nano-enabled products (mimicking their usage and end of life) will be exposed to organisms covering a large salinity gradient (up to 34 PSU). One novel aspect of nanoSALT is to use mesocosms to assess the impacts of ENMs across such a salinity gradient taking into account the exposure (hetero-aggregation, complexation with natural organic matter, salinity changes). Such a degree of complexity in term of exposure to ENMs has never been reached in other (inter)national projects and will provide necessary data for Environmental Risk Assessment.

The scientific program is based on laboratory experiments using two bivalve species covering a large salinity gradient (Scrobicula plana and Corbicula fluminea) under increasing realistic environmental exposure conditions (water, food-borne and mesocosms). After aging processes reflecting realistic conditions of use or the end of life of ENMs (WP2), their physico-chemical behavior will be follow across a salinity gradient (up to 34 PSU) (WP3). This WP3 will inform on the colloidal, chemical stability and consequently the exposure pathway at the marine-continental interface. This will influence the bioaccumulation processes (trophic transfers) and the localization in the different tissues and cellular compartments of the bivalve species (WP4). The ecotoxicity and ecophysiology (WP5) testings will be performed across a salinity gradient in mesocosms using several biochemical and behavioral responses (multi-biomarker approach). To adapt and develop new suitable tools for ENMs Envionmental Risk Assessment, the whole set of biomarkers will be integrated into indices, as the Integrated Biomarker Response and the expert system Health Status Index.