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To assess the environmental fate of engineered nanoparticles (ENPs), it is essential to understand their interactions with dissolved organic matter (DOM). The highly complex nature of the interactions between DOM and ENPs and other particulate matter (PM) requires investigating a wide range of material types under different conditions. However, despite repeated calls for an increased diversity of the DOM and PM studied, researchers increasingly focus on certain subsets of DOM and PM. Considering the discrepancy between the calls for more diversity and the research actually carried out, we hypothesize that materials that were studied more often are more visible in the scientific literature and therefore are more likely to be studied again. To investigate the plausibility of this hypothesis, we developed an agent-based model simulating the material choice in the experiments studying the interaction between DOM and PM between 1990 and 2015. The model reproduces the temporal trends in the choice of materials as well as the main properties of a network that displays the DOM and PM types investigated experimentally. The results, which support the hypothesis of a positive reinforcing material choice, help to explain why calls to increase the diversity of the materials studied are repeatedly made and why recent criticism states that the selection of materials is unbalanced., PLoS ONE, 13 (5), ISSN:1932-6203

International audience; The fate of manufactured nanoparticles in natural aqueous environments is influenced by dispersion and transport processes as well as aggregation and deposition. These processes depend on both environmental factors and properties intrinsic to the nanoparticles themselves. For example, at environmentally relevant concentrations (μg/L), titanium dioxide nanoparticles (TiO2 NPs) likely have a higher probability of interacting with suspended particulate matter (SPM) present at mg/L or greater concentrations in natural surface waters, rather than with themselves, favoring a heteroaggregation scenario. With both high specific surface area and reactivity, the SPM may act as a TiO2 NP carrier in the water column, strongly affecting their fate and transport via the heteroaggregation process. Herein, mechanistic evaluation of TiO2 NP fate in surface waters was assessed by measuring their heteroaggregation with different types of mineral SPM previously identified in the Rhône River (e.g., quartz, calcite, chlorite, feldspar, montmorillonite). The TiO2 NPs (μg/L) were spiked into synthetic riverine waters containing one of the main SPM analogues, their mixture, or the natural Rhone water SPM. The TiO2 NPs demonstrated a significant affinity for montmorillonite clay colloids as well as the natural SPM, leading to rapid heteroaggregation measured by time-resolved laser diffraction. In addition to determining the NP/SPM heteroaggregation kinetics and attachment efficiencies for the natural and analogue SPM, the influence of natural organic matter (NOM) on TiO2 NP fate and behavior was also assessed. Four common families of NOM analogues (i.e., proteins, polyhydroxy aromatics, polysaccharides, and amino sugars) were added to the SPM-containing synthetic waters to evaluate the role of NOM on the TiO2 NP compartmentalization. Protein and polyhydroxy aromatic analogues, followed by the amino sugar had the strongest stabilising effects on the system, while enhanced aggregation was observed in the presence of polysaccharide. Together, these mechanistic data, coupled to a river-scale fate model,5 will aid in ranking potential TiO2 NP fate scenarios and assessing their risk within natural aqueous environments. This work was funded by the French National Research Agency and the Swiss FOEN as NANOHETER under the frame of SIINN. http://nanoheter.cerege.fr

International audience; The fate of engineered nanoparticles (ENPs) in natural aqueous environments is influenced by ENP dispersion/transport and aggregation/deposition related to environmental factors as well as those intrinsic to the nanoparticles themselves. For example, at environmentally relevant concentrations (μg/L), TiO2 ENPs likely have a higher probability of interacting with suspended particulate matter (SPM) and natural organic matter (NOM) present at mg/L to g/L concentrations in natural surface waters, rather than with themselves. With both high specific surface area and reactivity, the SPM and NOM may act as TiO2 ENP carriers in the water column, strongly affecting their fate and transport via the heteroaggregation process. Herein, previously identified and characterized SPM and NOM compositions of the Rhone River, a major European river, were used to guide the selection of relevant analogues for mechanistic evaluation of TiO2 ENP fate in surface waters. The TiO2 ENPs (μg/L) were first spiked into synthetic riverine waters containing one of the main SPM analogues (e.g., quartz, calcite, chlorite, feldspar, muscovite). With rapid heteroaggregation and subsequent sedimentation, the TiO2 ENPs demonstrated a significant affinity for several of the SPM analogues, especially quartz and calcite. In addition to determining the ENP/SPM heteroaggregation kinetics and attachment efficiencies, the influence of NOM on the TiO2 ENP fate and behaviour was also assessed. Four common families of NOM analogues (i.e., proteins, polyhydroxy aromatics, polysaccharides, and amino sugars) were added to the SPM-containing synthetic waters to evaluate the role of NOM on the TiO2 ENP compartmentalization. The protein (bovine serum albumin) and polyhydroxy aromatic (Suwannee River humic acid) analogues, followed by the amino sugar (N-acetyl-D-glucosamine) had the strongest stabilising effects on the system, while enhanced aggregation was observed in the presence of the polysaccharide (YAS 34). Together, these mechanistic data, coupled to a river-scale fate model, will aid in ranking potential TiO2 ENP fate scenarios and assessing their risk within natural aqueous environments. This work was funded by the French National Research Agency and the Swiss FOEN as NANOHETER under the frame of SIINN. http://nanoheter.cerege.fr

International audience; The influence of pesticides (glyphosate, aminomethylphosphonic acid (AMPA) and 2.4-D) on the surface charge and aggregation of pure TiO2 nanoparticles (NP; 5-30 nm; anatase and rutile) have been investigated in modeled water solutions. The dependence of the surface charge and the size distribution at upon the various factors (including surface chemistry of NP and pesticides, presence of mono- (Na+) and bi-valent (Ca2+) cations, pH value, and ionic strength (IS) of an aqueous solution) has been studied. The presence of glyphosate (5µg/L) affects rutile TiO2 NP (5 mg/L) stabilization in NaCl solution of IS=10-4M - 10-3M (>CCC) and in CaCl2 solution of IS =10-4M (>CCC) with pH=5 near the pH point of zero charge (PZC) (pHPZC=4.5). With adding of the glyphosate no changes in NP aggregation were observed in very high (IS= 10-1M) ionic strength solutions for rutile NP and in all studied conditions for anatase NP. No significant changes in NP aggregation were observed in the presence of AMPA and 2.4-D. Compared to mono-valent cations, bi-valent cations favored an increase in zeta potential at pH8 and no changes at pH5. These results show new evidences of the role of pesticides on the NP mobility in aquatic environments.

International audience; The increasing production and use of nanoparticles (NP) in consumer products inevitably lead to ENP emissions into the environment. The physicochemical properties of NP depend on various parameters (e.g. pH, cations, IS). In natural waters, the stability of NP can vary as a function of a sum of these parameters and occurs by one of the numerous scenarios. In particular, the presence of anthropogenic organic molecules (AOM) can change the NP fate. Also, the presence of NP may affect the organic pollutants (fate and toxicity). The main objective of the work was to study the aggregation of TiO2 NP (pure hydrophilic 100 % rutile and pure hydrophilic 100 % anatase, 5−30 nm) in the presence of the most frequently occur and representative pesticides (glyphosate, AMPA, 2.4D) in natural waters considering lab experiments under relevant aqueous conditions (pH, ionic strength, presence and concentrations of mono- and bivalent cations). The presence of pesticides affected TiO2 NP homoaggregation in solutions (IS=10-3M - 10-2M) with pH values below the NP point of zero charge (PZC) for the anatase NPs (pH=6.5) and with pH values above the NP PZC for the rutile NP (pH=4.5). No changes in NP aggregation were observed in very low (IS=10-4M) or very high (IS= 10-1M) ionic strength solutions. The presence of the pesticides caused a significant modification of the NP surface charge (zeta potential) over a large range of salt concentrations (IS=10-4M - 10-1M). Compared to mono-valent cations (Na+), bi-valent cations (Ca2+) favor an increase in zeta potential of NP (anatase and rutile) at pH 8. There is no significant difference between at pH 5. Finally, these results demonstrated that, among the studied AOMs, glyphosate (with 4 pKa-s from 0.8 to 11) affects NP aggregation/stabilization in a wider range of physicochemical conditions. Overall, these results will aid in the evaluation of potential environmental risks posed by engineered NP in the aquatic environments exposed to pesticide load.

International audience; The fate and behavior of engineered nanoparticles (NPs) released in aquatic environments will be influenced by the water chemistry, as well as the pesticide load due to the potential for NP interaction with anthropogenic organic molecules (AOMs). As such, surface charge and aggregation of pure hydrophilic 100 % rutile and pure hydrophilic 100 % anatase titanium dioxide nanoparticles (TiO2 NPs, 5−30 nm) were evaluated in a modeled water solution in the presence of three common AOMs, glyphosate, aminomethylphosphonic acid (AMPA), and 2.4-D. The surface charge and size distribution were assessed over time as a function of various factors including surface chemistry of the NPs and AOMs, presence of mono- and bi-valent cations, pH, and ionic strength of the aqueous solution. The presence of AOMs (5 µg/L) affected TiO2 NP (5 mg/L) homoaggregation in solutions (IS=10-3M - 10-2M) with pH values below the NP point of zero charge (PZC) for the anatase NPs (pH=6.5) and with pH values above the NP PZC for the rutile NPs (pH=4.5). No changes in NP aggregation were observed in very low (IS=10-4M) or very high (IS= 10-1M) ionic strength solutions. Passing through the PZC resulted in irreversible aggregation of the NPs, even in the presence of AOMs. The presence of the pesticides also caused a significant modification of the NP surface charge (zeta potential) over a large range of salt concentrations (IS=10-4M - 10-1M). Compared to mono-valent cations, bi-valent cations (Ca2+) favored NP aggregation and an increase in zeta potential. Finally, these results demonstrated that, among the studied AOMs, glyphosate (with 4 pKa-s from 0.8 to 11) affects NP aggregation/stabilization in a wider range of physicochemical conditions. Overall, these results will aid in the evaluation of potential environmental risks posed by engineered NPs in the aquatic environments exposed to pesticide load.