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REEs are essential materials for modern technology due to their unmatched physical and chemical properties. This paper reviews the potential and types of rare earth elements (REE) in 32 different secondary sources that contain water, wastewater, and slime/solid wastes originating from Turkey. Secondary sources were classified into five different categories as mining wastes (M), combustion residuals (C), sediments and sludges (S), e waste (E), and wastewater (WW). After pre-processing and acidic digestion of solid samples, elemental concentrations of wastewaters and acidic leachates were measured. The highest total REE (REEtotal) concentration was obtained in a combustion residue sample coded as C5 with 379 mg/kg. Besides, the highest critical REE (REEcritical) content was found in an e-waste sample including 346 mg/kg total REE and 76% critical REE. In addition, boron mine wastewater (W5) with a total REE concentration of 110 mu g/L was evaluated as a significant important secondary source in terms of yttrium. The association, between scandium and total REE concentrations of category M and S, was evaluated and correlation coefficients of 0.86 and 0.69, respectively were calculated. E-waste and thermal power plant (TPP) ashes were evaluated as the secondary sources with the highest REE potential among the whole type of waste/wastewater. (C) 2021 Elsevier B.V. All rights reserved.

Engineered silver nanoparticles (Ag NPs) often partially or fully sulfidized enter the environment. There sulfidation of Ag NPs greatly decreases the rate of oxidation of Ag0 and the release of Ag+. We hypothesized that sulfidation of Ag0 NPs added to an emergent freshwater wetland mesocosm would greatly decrease silver bioavailability. We dosed a 1.2x1x3m freshwater wetland mesocosm with 30nm PVP coated Ag NPs (25 mg/L Ag) and then determined the distribution and speciation of Ag NPs after 18 months. A sediment diagenetic model was developed and used to predict the distribution and speciation of Ag in the mesocosms. Ag0 NPs in sediments sulfidized over 18 months. Ag speciation was approximately 50 Ag2S 30 Ag S R (likely organic matter complexed) and 20 Ag0 as determined by X ray absorption spectroscopy. Sulfidation decreased dissolved Ag concentration in the water column to below method detection (2 µg/L). The sediment diagenetic model could predict Ag distribution and speciation well using parameter values (e.g. bioturbation) and partition coefficients (e.g. Ag organic matter) in the range expected for freshwater sediment and demonstrated seasonal fluctuations. There was measurable uptake of Ag into several sediment dwelling organisms suggesting that Ag2S or Ag S R species remained bioavailable. The uptake of Ag2S in duckweed roots was confirmed with synchrotron based micro X ray fluorescence (µ XRF) and µ XANES indicates that the silver within the root cortex was predominantly Ag0.

A recent study of silver nanoparticles introduced to a simulated freshwater wetland indicated an initial period of particle removal and associated die off of some aquatic plants. This talk considers the initial transport and fate of nanoparticles introduced to this system from the standpoint of heteroaggregation deposition and dissolution and the implications for short term impacts on rooted aquatic plants. Simulations show that nanoparticles introduced in a complex albeit greatly simplified environment exhibit a wide range of behaviors depending on their affinities for each other and their concentrations. The complexity of these interactions appears to be governed by the relative affinity of nanoparticles for each other (autoaggregation) and with background particles (heteroaggregation) and other native surfaces. Surface affinity as a predictor or nanoparticle fate is explored further in the context of interactions with plant surfaces biofilms and the potential for uptake by plants. A functional assay for determining the affinity of nanoparticles for complex mixtures of native particles is evaluated.

International audience; Nanomaterials exhibit novel properties that enable new applications ranging from molecular electronics to energy production. Proactive consideration of the potential impacts on human health and the environment resulting from nanomaterial production and use requires methods for forecasting risk associated with of these novel materials. However, the potential variety of nanomaterials is virtually infinite and a case-by-case analysis of the risks these materials may pose is not possible. The challenge of forecasting risk for a broad number of materials is further complicated by large degrees of uncertainty concerning production amounts, the characteristics and uses of these materials, exposure pathways, and a scarcity of data concerning the relationship between nanomaterial characteristics and their effects on organisms and ecosystems. A traditional risk assessment on nanomaterials is therefore not possible at this time. In its place, an evolving process is needed for analyzing the risks associated with emerging nanomaterials-related industries. In this communication, we propose that such a process should include the following six key features: 1) the ability to generate forecasts and associated levels of uncertainty for questions of immediate concern, 2) a consideration of all pertinent sources of nanomaterials, 3) an inclusive consideration of the impacts of activities stemming from nanomaterial use and production that extends beyond the boundaries of toxicology and include full life cycle impacts, 4) the ability to adapt and update risk forecasts as new information becomes available, 5) feedback to improve information gathering and, 6) feedback to improve nanomaterial design. Feature #6 implies that the potential risks of nanomaterials must ultimately be determined as a function of fundamental, quantifiable properties of nanomaterials, so that when these properties are observed in a new material, they can be recognized as indicators of risk. Thus, the required risk assessment process for nanomaterials addresses needs that span urgent, short-term questions dealing with nanomaterials currently in commerce, to longer-term issues that will require basic research and advances in theory. In the following sections we outline issues surrounding each of these six features ad discuss.

International audience; no abstract

International audience; no abstract

Uptake, transport and toxicity of engineered nanomaterials (ENMs) into plant cells are complex processes that are currently still not well understood. Parts of this problem are the multifaceted plant anatomy, and analytical challenges to visualize and quantify ENMs in plants. We critically reviewed the currently known ENM uptake, translocation, and accumulation processes in plants. A vast number of studies showed uptake, clogging, or translocation in the apoplast of plants, most notably of nanoparticles with diameters much larger than the commonly assumed size exclusion limit of the cell walls of ∼5–20 nm. Plants that tended to translocate less ENMs were those with low transpiration, drought-tolerance, tough cell wall architecture, and tall growth. In the absence of toxicity, accumulation was often linearly proportional to exposure concentration. Further important factors strongly affecting ENM internalization are the cell wall composition, mucilage, symbiotic microorganisms (mycorrhiza), the absence of a cuticle (submerged plants) and stomata aperture. Mostly unexplored are the roles of root hairs, leaf repellency, pit membrane porosity, xylem segmentation, wounding, lateral roots, nodes, the Casparian band, hydathodes, lenticels and trichomes. The next steps towards a realistic risk assessment of nanoparticles in plants are to measure ENM uptake rates, the size exclusion limit of the apoplast and to unravel plant physiological features favoring uptake.

The study and application of materials possessing size dimensions in the nano scale range and, as a result, unique properties have led to the birth of a new field; nanotechnology. Scientists and engineers have discovered and are exploiting the novel physicochemical characteristics of nanoparticles (NPs) to enhance consumer products and technologies in ways superior to their bulk counterparts. Escalating production and use of NPs will unavoidably lead to release and exposure to environmental systems. This introduction of emerging potential contaminant NPs will provide new and interesting challenges for exposure and risk forecasting as well as environmental endurance.The ultimate goal of this research is to develop a framework that incorporates experimental and computational efforts to assess and better understand the exposure of metal and metal-oxide NPs released to wastewater treatment plants (WWTPs) and further implications on land application units (LAUs) where biosolids can be applied. The foundation of the computational effort is comprised of Monte Carlo mass balance models that account for the unique processes affecting NP fate and transport through the different technical compartments of a WWTP and LAU. Functional assay and bioreactor experiments in environmental media were used to determine parameters capable of describing the critical processes that impact the fate of NPs in wastewater. The results of this research indicate that a simplified, but still environmentally relevant nano-specific exposure assessment is possible through experimentation to parameterize adapted models. Black box modeling efforts, which have been shown in previous studies, show no disadvantage relative to discretization of technical compartments as long as all key transport and fate mechanisms are considered. The distribution coefficient (_), an experimentally determined, time-dependent parameter, can be used to predict the distribution of NPs between the liquid and solid phase in WWTPs. In addition, this parameter can be utilized a step further for the estimation of the more fundamental, time independent attachment efficiency between the NPs and the solids in wastewater. The NP core, size, and surface coating will influence the value of these parameters in addition to the background particle characteristics as the parameters are specific to the environmental system of study. For the metal and metal-oxide NPs studied, preferential overall association of approximately 90% or greater with the solid phase of wastewater was observed and predicted. Furthermore, NP transformations including dissolution, redox reactions, and adsorption can potentially impact exposure. For example, experimental results showed that nano-CeO2 is reduced from Ce(IV) to Ce(III) when in contact with wastewater bacteria where Ce2S3 will likely govern the Ce(III) phase in biosolids. From the literature, similar transformations have been observed with Ag and ZnO NPs to Ag2S and ZnS. With respect to TiO2 NPs, studies indicated that due to high insolubility, these NPs would not undergo transformation in WWTPs. The distribution and transformation rate coefficients can then be used in fate models to predict the NP species exposed to aquatic and terrestrial systems and environmentally relevant concentrations released from WWTPs. Upon completion of the WWTP model, the predicted concentrations of NPs and NP transformation byproducts released in effluent and biosolids were attainable. A simple mass balance model for NP fate in LAUs was then developed to use this output. Results indicate that NP loading on LAUs would be very low but that build up over time to steady state could result in mass concentrations on the order of the typical level for the background metal in soil. Transport processes of plant uptake and leaching were expected to greatly impact the solid phase concentration of the NPs remaining in the LAU, while rainfall did not impart a significant influence upon variation between low and high annual amounts. The significance of this research is the introduction of a method for NP exposure assessment in WWTPs and subsequently in LAUs. This work describes and quantifies the key processes that will impact Ag, TiO2, CeO2 and ZnO NP fate and transport, which can inform future studies, the modeling community and regulatory agencies.

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Surface chemistry plays an essential role in determining the reactivity, bioaccessibility, bioavailability and toxicity of nanoparticles (NPs) in the environment. Processes such as aggregation, deposition and biouptake are controlled in part by the attachment efficiency, α, between particles and the surfaces they encounter. One premise of this research is that surface hydrophobicity is a pivotal property of NP surfaces that can affect the behavior of NPs in aquatic environment and potentially decide the fate and transport of NPs. However, there are multiple challenges in the characterization of hydrophobicity for NPs. Methods developed for macroscopic surfaces or organic compounds may not be readily applied or interpreted for the case of nano-scale surfaces. This dissertation addresses theoretical basis for applying methods to determining hydrophobicity of NPs. The use of an octanol-water partitioning method analogous to that used for organic compounds was evaluated on the basis of trends anticipated by thermodynamics, and by experimental observations. This work shows that partitioning of NPs in two phases systems, such as water and octanol, is not uniquely determined by hydrophobicity, but also influenced by surface charge and particle size. The water-oil interface rather than the bulk phases becomes the thermodynamically favored location for NP accumulation once NPs are larger than 1-10 nm and/or the surface is amphiphilic. Nonetheless, the relative hydrophobicity of selected NPs, as characterized by adsorption of molecular probes (i.e. organic dye and naphthalene), was consistent with the macroscopic contact angle measurements and octanol-water distribution coefficients. The in-situ adsorption of these molecular probes offers the most solid grounds for measurement of hydrophobicity. Other measure of hydrophobicity or hydrophilicity such as water-affinity based methods that measure water vapor adsorption to nanomaterial powders, or immersion microcalorimetry and thermogravimetric analysis, yielded similar results to the molecular probes. However, possible physical or chemical transformations to NP surfaces during characterization by these other methods limited the use of results to infer hydrophobicity based on a rigorous thermodynamic model.Column experiments suggested that the attachment efficiency of NPs to biofilm was generally greater for more hydrophobic NPs, though polymeric coatings might stabilize NPs against the attachment. The affinity of NPs for a variety of bacterial surfaces (i.e. different species, planktonic or biofilm, with or without extracellular polymeric substances (EPS)) of different hydrophobicities, which correlated with the quantity of proteins in EPS, was also investigated. It was found that the attachment of hydrophobic NPs increased with the hydrophobicity of bacterial surfaces, but not for hydrophilic NPs. Environmental conditions such as divalent ions and pH influenced the affinity of nanoparticle for bacterial surface by changing the bacterial surface hydrophobicity and electric double layer interaction, respectively.

The transport of uncoated silver nanoparticles (AgNPs) in a porous medium composed of silica glass beads modified with a partial coverage of iron oxide (hematite) was studied and compared to that in a porous medium composed of unmodified glass beads (GB). At a pH lower than the point of zero charge (PZC) of hematite, the affinity of AgNPs for a hematite-coated glass bead (FeO-GB) surface was significantly higher than that for an uncoated surface. There was a linear correlation between the average nanoparticle affinity for media composed of mixtures of FeO-GB and GB collectors and the relative composition of those media as quantified by the attachment efficiency over a range of mixing mass ratios of the two types of collectors, so that the average AgNPs affinity for these media is readily predicted from the mass (or surface) weighted average of affinities for each of the surface types. X-ray photoelectron spectroscopy (XPS) was used to quantify the composition of the collector surface as a basis for predicting the affinity between the nanoparticles for a heterogeneous collector surface. A correlation was also observed between the local abundances of AgNPs and FeO on the collector surface.