| 1. |
- Baalousha, M., et al.
(författare)
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Modeling nanomaterial fate and uptake in the environment: current knowledge and future trends
- 2016
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Ingår i: Environmental Science-Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 3:2, s. 323-345
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Tidskriftsartikel (refereegranskat)abstract
- Modeling the environmental fate of nanomaterials (NMs) and their uptake by cells and organisms in the environment is essential to underpin experimental research, develop overarching theories, improve our fundamental understanding of NM exposure and hazard, and thus enable risk assessment of NMs. Here, we critically review the state-of-the-art of the available models that can be applied/adapted to quantify/predict NM fate and uptake in aquatic and terrestrial systems and make recommendations regarding future directions for model development. Fate models have evolved from substance flow analysis models that lack nano-specific processes to more advanced mechanistic models that (at least partially) take nano-specific (typically non-equilibrium, dynamic) processes into account, with a focus on key fate processes such as agglomeration, sedimentation and dissolution. Similarly, NM uptake by organisms is driven by dynamic processes rather than by equilibrium partitioning. Hence, biokinetic models are more suited to model NM uptake, compared with the simple bio-accumulation factors used for organic compounds. Additionally, biokinetic models take speciation processes (e.g. particulate versus ionic uptake) into account, although identifying essential environment-specific processes to include in models remains a challenge. The models developed so far require parameterization, calibration and validation with available data, e.g. field data (if available), or experimental data (e.g. aquatic and terrestrial mesocosms), rather than extension to more complex and sophisticated models that include all possible transformation processes. Collaborative efforts between experimentalists and modelers to generate appropriate ground-truth data would advance the field most rapidly.
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| 2. |
- Cornelis, Geert, 1978, et al.
(författare)
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A signal deconvolution method to discriminate smaller nanoparticles in single particle ICP-MS
- 2014
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477. ; 29:1, s. 134-144
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Tidskriftsartikel (refereegranskat)abstract
- Single particle ICP-MS (spICP-MS) analysis of inorganic nanoparticles (NPs) cannot accurately distinguish dissolved ion signals and signals from relatively small NPs, although these particles are often more reactive than their larger counterparts. A signal deconvolution method was developed for spICP-MS analysis using gold (Au) NPs of nominally 10, 15 or 30 nm diameter. The signal distributions of dissolved Au standards were parameterised as a function of concentration using a mixed Polyagaussian probability mass function. Dissolved curves were fitted using this parameterisation to the low-intensity signals of samples containing NPs to subtract and deconvolute the dissolved signals from the particle signals. The dissolved signals were quantified in this process. The accuracy of the deconvolution method was confirmed for all NP suspensions studied when comparing the size and number concentration obtained with the deconvolution method with values based on transmission electron microscopy. This method thus allows analysis of NP suspensions with spICP-MS where it was hitherto not possible. The applicability domain lies predominantly with relatively small NPs and/or when a relatively high concentration of dissolved ions of the element of interest is present, where overlapping between dissolved and particulate signals occurs.
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| 3. |
- Cornelis, Geert, 1978, et al.
(författare)
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Antimony leaching from MSWI bottom ash: Modelling of the effect of pH and carbonation
- 2012
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 32:2, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- Development of treatment methods to reduce Sb leaching from municipal solid waste incinerator (MSWI) bottom ash, such as accelerated carbonation, is being complicated by insufficient understanding of Sb geochemistry. The leaching of antimonate (Sb(V)) and antimonite (Sb(III)) in MSWI bottom was studied as a function of pH and degree of carbonation. While total (Sb(V)+Sb(III)) leaching was lowest (1.2mgkg-1) at the natural pH (i.e. 10.6) of uncarbonated bottom ash, HPLC-ICP-MS analysis showed that acidification and carbonation increased Sb(V) leaching, but decreased Sb(III) leaching, probably because Sb(III)(OH)4- became less stable. PHREEQC geochemical modelling suggested that Sb(V) concentrations approached equilibrium with the romeites, i.e. calcium antimonates, Ca1.13Sb2(OH)0.26·0.74H2O at pH=10.6 and Ca[Sb(OH)6]2at pH=8. It is hypothesised that not interaction with ettringite but dissolution of romeite controls antimonate leaching in the pH range 8-11 in MSWI bottom ash, because while Ca is preferentially leached from romeite, the mineral structures containing more Ca at higher pH are less soluble. A model was proposed where acidification and carbonation both lead to lower Ca2+and/or hydroxyl concentration, which removes Ca2+and hydroxyls from the romeite structure and leads to comparably higher Sb(V) concentration in equilibrium with romeite. Sb solubility depends on pH and Ca2+availability in this model, which has implications for bottom ash valorisation and risk assessment. © 2011 Elsevier Ltd.
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| 4. |
- Cornelis, Geert
(författare)
-
Bioturbation of Ag2S-NPs in soil columns by earthworms
- 2019
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 252, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- Sewage sludge contains Ag2S-NPs causing NP exposure of soil fauna when sludge is applied as soil amendment. Earthworm bioturbation is an important process affecting many soil functions. Bioturbation may be affected by the presence of Ag2S-NPs, but the earthworm activity itself may also influence the displacement of these NPs that otherwise show little transport in the soil. The aim of this study was to determine effects of Ag2S-NPs on earthworm bioturbation and effect of this bioturbation on the vertical distribution of Ag2S-NPs. Columns (12 cm) of a sandy loamy soil with and without Lumbricus rubellus were prepared with and without 10 mg Ag kg(-1), applied as Ag2S-NPs in the top 2 cm of the soil, while artificial rainwater was applied at similar to 1.2 mm day(-1). The soil columns were sampled at three depths weekly for 28 days and leachate collected from the bottom. Total Ag measurements showed more displacement of Ag to deeper soil layers in the columns with earthworms. The application of rain only did not significantly affect Ag transport in the soil. No Ag was detected in column leachates. X-ray tomography showed that changes in macro porosity and pore size distribution as a result of bioturbation were not different between columns with and without Ag2S-NPs. Earthworm activity was therefore not affected by Ag2S-NPs at the used exposure concentration. Ag concentrations along the columns and the earthworm density allowed the calculation of the bioturbation rate. The effect on the Ag transport in the soil shows that earthworm burrowing activity is a relevant process that must be taken into account when studying the fate of nanoparticles in soils. (C) 2019 Elsevier Ltd. All rights reserved.
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| 5. |
- Cornelis, Geert, et al.
(författare)
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Challenges and current approaches toward environmental monitoring of nanomaterials
- 2021
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Ingår i: Monitoring Environmental Contaminants : A volume in Environmental Contaminants. - 9780444643360 ; , s. 73-108
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Bokkapitel (refereegranskat)abstract
- Engineered nanomaterials (ENMs), i.e., man-made particles having at least one dimension smaller than 100nm, have found their way into the environment. Parallel to the efforts to elucidate the possible harmful effects of ENMs, techniques have been developed to monitor environmental ENM concentrations. This chapter discusses the techniques that can currently distinguish ENMs from naturally occurring particles at realistic concentration detection limits without a tedious sample pretreatment procedure. For inorganic ENMs, the most promising approach is based on single particle ICP-MS, and this technique has been developed in recent years to measure solid samples in addition to aquatic samples and distinguish the many different forms of occurrence of ENMs in realistic samples from naturally occurring particles. The detection capabilities for C-based particles are lagging and will likely be the focus of analytical developments in the coming years.
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| 6. |
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| 7. |
- Cornelis, Geert
(författare)
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Chromium Hazard and Risk Assessment: New Insights from a Detailed Speciation Study in a Standard Test Medium
- 2018
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Ingår i: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 37, s. 983-992
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Tidskriftsartikel (refereegranskat)abstract
- Despite the consensus about the importance of chemical speciation in controlling the bioavailability and ecotoxicity of trace elements, detailed speciation studies during laboratory ecotoxicity testing remain scarce, contributing to uncertainty when extrapolating laboratory findings to real field situations in risk assessment. We characterized the speciation and ecotoxicological effects of chromium (Cr-III and Cr-VI) in the International Organization for Standardization (ISO) medium for algal ecotoxicity testing. Total and dissolved (< 0.22 mu m) Cr concentrations showed little variability in media spiked with Cr-VI, whereas dissolved Cr concentration decreased by as much as 80% over a 72-h time period in medium amended with Cr-III. Analyses by ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) highlighted the absence of redox interconversion between Cr-III or Cr-VI both in the presence and absence of algal cells (Raphidocelis subcapitata). Furthermore, the concentration of ionic Cr-III dropped below detection limits in less than 2 h with the corresponding formation of carbonate complexes and Cr hydroxides. Precipitation of Cr-III in the form of colloidal particles of variable diameters was confirmed by nanoparticle (NP) tracking analysis, single particle ICP-MS, and single particle counting. In terms of time-weighted dissolved (< 0.22 mu m) Cr concentration, Cr-III was 4 to 10 times more toxic than Cr-VI. However, Cr-III ecotoxicity could arise from interactions between free ionic Cr-III and algae at the beginning of the test, from the presence of Cr-bearing NPs, or from a combination of the 2. Future ecotoxicological studies must pay more attention to Cr speciation to reliably compare the ecotoxicity of Cr-III and Cr-VI. (C) 2017 SETAC
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| 8. |
- Cornelis, Geert, et al.
(författare)
-
Drift correction of the dissolved signal in single particle ICPMS
- 2016
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 408:19, s. 5075-5087
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Tidskriftsartikel (refereegranskat)abstract
- A method is presented where drift, the random fluctuation of the signal intensity, is compensated for based on the estimation of the drift function by a moving average. It was shown using single particle ICPMS (spICPMS) measurements of 10 and 60 nm Au NPs that drift reduces accuracy of spICPMS analysis at the calibration stage and during calculations of the particle size distribution (PSD), but that the present method can again correct the average signal intensity as well as the signal distribution of particle-containing samples skewed by drift. Moreover, deconvolution, a method that models signal distributions of dissolved signals, fails in some cases when using standards and samples affected by drift, but the present method was shown to improve accuracy again. Relatively high particle signals have to be removed prior to drift correction in this procedure, which was done using a 3 x sigma method, and the signals are treated separately and added again. The method can also correct for flicker noise that increases when signal intensity is increased because of drift. The accuracy was improved in many cases when flicker correction was used, but when accurate results were obtained despite drift, the correction procedures did not reduce accuracy. The procedure may be useful to extract results from experimental runs that would otherwise have to be run again.
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| 9. |
- Cornelis, Geert
(författare)
-
Effect of deposition, detachment and aggregation processes on nanoparticle transport in porous media using Monte Carlo simulations
- 2021
-
Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; , s. 2223-2234
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Tidskriftsartikel (refereegranskat)abstract
- A novel off-lattice three-dimensional coarse-grained Monte Carlo model is developed to study engineered nanoparticle (ENP) behavior in porous media. Based on individual particle tracking and on the assumption that different physicochemical processes may occur with different probabilities, our model is used to independently evaluate the influence of homoaggregation, attachment and detachment processes on ENP transport and retention inside porous media made of colloidal collectors. The possibility of straining, i.e. trapping of ENPs or aggregates that are too large to pass pore necks, is also included in the model. The overall probability of ENP retention as a function of the above mentioned processes is quantified using functional tests in the form of a alpha(global)(t(ref)) retention parameter. High alpha(global)(t(ref)) values were obtained for moderate probabilities of homoaggregation between ENPs (alpha(ENP-ENP)) and very small probabilities of attachment between ENPs and collectors (alpha(att)), thus indicating the important role of homoaggregation and attachment in ENP retention. Moreover, attaching ENPs and large aggregates was found to cause pore neck enclosure and thus largely contributed to the straining of unbound ENPs. An analysis of depth distribution of retained ENPs revealed that, depending on the dominating conditions, the number of ENPs was decreasing monotonously or exponentially with depth. The introduction of the ENP detachment probability (alpha(det)) from collectors resulted in an increased ENP occurrence at the porous media matrix outlet. It was also found that different sets of alpha(det) and alpha(att) values, reflecting different ENPs and collector physicochemical properties and inter-particle forces, lead to identical alpha(global)(t(ref)) values. This constitutes an important outcome indicating that alpha(global)(t(ref)) values determined from functional tests are not mechanistic but operationally defined parameters and thus cannot be deemed predictive beyond these tests.
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| 10. |
- Cornelis, Geert
(författare)
-
Effect of soil properties on gold- and platinum nanoparticle mobility
- 2017
-
Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 466, s. 446-453
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Tidskriftsartikel (refereegranskat)abstract
- Soils overlying buried gold (Au) and platinum (Pt) deposits are often Au/Pt-anomalous, widening exploration footprints. This may be a result of the dispersion of (bio) geochemically formed Au/Pt nanoparticles and their sorption/deposition by solid soil phases. However, the influence of soil properties on nanoparticle dispersion, sorption and partitioning are little understood. To assess the partitioning and sorption behaviour of Au- and Pt nanoparticles, soils were spiked with spherical, citrate-stabilized Au- and Pt nanoparticles (diameter: 10-12 nm, final concentration 100 mu g kg(-1)). Soil slurries (1:10, w:w, soil: deionized water) were incubated at 22 degrees C on an end-over-end shaker for 28 days. Gold/Pt concentrations were measured in 0.45 mu m and 1 kDa filtered solutions using inductively coupled plasma-mass spectrometry. Neither Pt nor Au were detected in 1 kDa filtrates. Between 10.3 and 98.7 wt% of Au/Pt was sorbed to solid soil phases. Clay, C-org, Mg, Mn, Fe and Ca contents of soils were significant predictors of Au/Pt-nanoparticle sorption, with clay content explaining > 80% of variation within the Au sorption dataset. Partitioning of sorbed nanoparticles between solid phases was assessed using selective sequential extractions. In all soils 1-20 wt% of Au/Pt was detected in watery extracts. A further 1-25 wt% were associated with the easily remobilizable fraction. The majority of sorbed Au/Pt nanoparticles were sorbed to the organic matter (OM, 53-77 wt% for Pt and 14-80 wt% for Au) and the Fe/Mn-oxides (up to 42 wt%). These results show that: i) Au- and Pt nanoparticles are stable and can remain highly mobile/dispersible in soil solutions, and ii) elevated clay, C-org and Fe/Mn-oxide contents decrease, whereas elevated sand contents and pH increase their mobility. Across all soils, OM and clays were the most important sorbent of Au/Pt nanoparticles, suggesting that the separation of clays and OM, and analyses of their Au/Pt-contents may enhance the contrast of geochemical footprints.
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| 11. |
- Cornelis, Geert, 1978, et al.
(författare)
-
Fate and Bioavailability of Engineered Nanoparticles in Soils: A Review
- 2014
-
Ingår i: Critical Reviews in Environmental Science and Technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 44:24, s. 2720-2764
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Tidskriftsartikel (refereegranskat)abstract
- Interactions within natural soils have often been neglected when assessing fate and bioavailability of engineered nanomaterials (ENM) in soils. This review combines patchwise ENM research using natural soils with the much wider literature on ENM performed in standard tests or on the fate of colloids in soils, and an analysis of the diverse ENM characteristics determining availability from the soil organisms' perspective to assess the main soil characteristics that determine the fate, speciation, and ultimately bioavailability of ENM in natural soils. Predominantly salinity, texture, pH, concentration, and nature of mobile organic compounds and degree of saturation determine ENM bioavailability.
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| 12. |
- Cornelis, Geert, 1978
(författare)
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Fate descriptors for engineered nanoparticles: the good, the bad, and the ugly
- 2015
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Ingår i: Environmental science: Nano. - 2051-8153 .- 2051-8153. ; 1:2, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- Developments in hazard identification of engineered nanoparticles (ENP) have not been met with proper fate descriptors to calculate travel distances and the bioavailable concentration of ENP. Three possible fate descriptors for ENP in soils are compared – batch partitioning coefficients (Kd values), batch retention coefficients (Kr values) and column attachment efficiency – in view of both technical and practical aspects of environmental risk assessments of ENP. Kd values are deemed not appropriate fate descriptors for ENP because the equilibrium assumption is not valid. The kinetic interpretation of batch studies offered by Kr values bears a link to relevant ENP processes in the environment, but interpretation may be confounded by the conditions of high shear during batch tests complicating direct use in transport or bioavailability calculations. Column experiments are, to some extent, also operationally defined and require a more experimentally dedicated approach that does not necessarily lead to a widely carrying physical parameter. Future efforts should therefore be investigated in development of tests that strike a better balance between operational simplicity and technical accuracy.
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| 13. |
- Cornelis, Geert
(författare)
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Harmonizing across environmental nanomaterial testing media for increased comparability of nanomaterial datasets
- 2020
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 7, s. 13-36
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Tidskriftsartikel (refereegranskat)abstract
- The chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is essential that sufficient context be provided for describing the physical and chemical characteristics of the setting in which a nanomaterial may be present. While the nanomaterial environmental, health and safety (NanoEHS) field has begun harmonization to allow data comparison and re-use (e.g. using standardized materials, defining a minimum set of required material characterizations), there is limited guidance for standardizing test media. Since most of the NM properties driving environmental behaviour and toxicity are medium-dependent, harmonization of media is critical. A workshop in March 2016 at Duke University identified five categories of test media: aquatic testing media, soil and sediment testing media, biological testing media, engineered systems testing media and product matrix testing media. For each category of test media, a minimum set of medium characteristics to report in all NM tests is recommended. Definitions and detail level of the recommendations for specific standardized media vary across these media categories. This reflects the variation in the maturity of their use as a test medium and associated measurement techniques, variation in utility and relevance of standardizing medium properties, ability to simplify standardizing reporting requirements, and in the availability of established standard reference media. Adoption of these media harmonization recommendations will facilitate the generation of integrated comparable datasets on NM fate and effects. This will in turn allow testing of the predictive utility of functional assay measurements on NMs in relevant media, support investigation of first principles approaches to understand behavioral mechanisms, and support categorization strategies to guide research, commercial development, and policy.
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| 14. |
- Cornelis, Geert
(författare)
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Impact of Ag2S NPs on soil bacterial community - A terrestrial mesocosm approach
- 2020
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Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier BV. - 0147-6513 .- 1090-2414. ; 206
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Tidskriftsartikel (refereegranskat)abstract
- Soils might be a final sink for Ag2S nanoparticles (NPs). Still, there are limited data on their effects on soil bacterial communities (SBC). To bridge this gap, we investigated the effects of Ag2S NPs (10 mg kg(-1) soil) on the structure and function of SBC in a terrestrial indoor mesocosm, using a multi-species design. During 28 days of exposure, the SBC function-related parameters were analysed in terms of enzymatic activity, community level physiological profile, culture of functional bacterial groups [phosphorous-solubilizing bacteria (P-SB) and heterotrophic bacteria (HB)], and SBC structure was analysed by 16S rRNA gene-targeted denaturing gradient gel electrophoresis.The SBC exposed to Ag2S NPs showed a significative decrease of functional parameters, such as p-glucosidase activity and L-arginine consumption, and increase of the acid phosphatase activity. At the structural level, significantly lower richness and diversity were detected, but at later exposure times compared to the AgNO3 treatment, likely because of a low dissolution rate of Ag2S NPs. In fact, stronger effects were observed in soils spiked with AgNO3, in both functional and structural parameters. Changes in SBC structure seem to negatively correlate with parameters related to phosphorous (acid phosphatase activity) and carbon cycling (abundance of HB, P-SB, and beta-glucosidase activity). Our results indicate a significant effect of Ag2S NPs on SBC, specifically on parameters related to carbon and phosphorous cycling, at doses as low as 10 mg kg soil. These effects were only observed after 28 days, highlighting the importance of long-term exposure experiments for slowly dissolving NPs.
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| 15. |
- Cornelis, Geert
(författare)
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Key principles and operational practices for improved nanotechnology environmental exposure assessment
- 2020
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 15, s. 731-742
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Forskningsöversikt (refereegranskat)abstract
- Nanotechnology is identified as a key enabling technology due to its potential to contribute to economic growth and societal well-being across industrial sectors. Sustainable nanotechnology requires a scientifically based and proportionate risk governance structure to support innovation, including a robust framework for environmental risk assessment (ERA) that ideally builds on methods established for conventional chemicals to ensure alignment and avoid duplication. Exposure assessment developed as a tiered approach is equally beneficial to nano-specific ERA as for other classes of chemicals. Here we present the developing knowledge, practical considerations and key principles need to support exposure assessment for engineered nanomaterials for regulatory and research applications.The operationalization and improvement of environmental exposure assessment models for engineered nanomaterials can build on ten emerging principles relating to their release pathways, waste handling, transformations, influence of the properties on reactions and role that organisms can play in their fate and transport.
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| 16. |
- Cornelis, Geert
(författare)
-
Nanomaterials as soil pollutants
- 2018
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Ingår i: Soil pollution : from monitoring to remediation. - 9780128498736 ; , s. 161-190
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 17. |
- Cornelis, Geert
(författare)
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Occurrence, behaviour and effects of inorganic nanoparticles in the environment
- 2021
-
Ingår i: Analysis and characterisation of metal-based nanomaterials. - : Elsevier. - 9780323853057 ; 93:93, s. 1-34
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Bokkapitel (refereegranskat)abstract
- Research in environmental risk assessment (ERA) of nanomaterials (NMs) has been an important incentive to develop analytical approaches to better understand and quantify fate and ecotoxicity of these materials in standard media and field environmental samples. This chapter presents and overview of the most recent insights in fate and ecotoxicity of NMs to steer analytical chemists to the most pressing analytical needs to further ERA of NMs thus avoid making it overly conservative. Sensitive analysis is required to quantify and characterize NMs at generally low expected concentrations (μg L− 1 to ng L− 1 range). Moreover, analysis of the core NM composition is required because many NMs are subject to transformation reactions in the environment, which in turn affects their fate and ecotoxicity. At the very minimum, dissolution of the NMs should be quantified, especially during standard ecotoxicity assays, while mesocosm-scale experiments have revealed unexpected NM behaviour that otherwise does not appear from standard tests. Finally, databases of relevant fate descriptors need development to aid NM fate prediction, similarly to soluble contaminants.
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| 18. |
- Cornelis, Geert
(författare)
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Polyphosphates and Fulvates Enhance Environmental Stability of PO4-Bearing Colloidal Iron Oxyhydroxides
- 2016
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 64, s. 8465-8473
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Tidskriftsartikel (refereegranskat)abstract
- Iron oxyhydroxide nanoparticles (Fe-NPs) are natural vectors of phosphate (PO4) in the environment. Their mobility is determined by colloidal stability, which is affected by surface composition. This might be manipulated in engineered NPs for environmental or agricultural applications. Here, the stability of PO4-Fe-NPs (HFO/goethite) was determined across contrasting environmental conditions (pH, Ca concentration) and by using fulvates (FA) and polyphosphates (poly-P's) as coatings. The PO4-Fe-NPs are unstable at Ca concentrations above 0.1 mM. Addition of FA and some poly-P's significantly improved stability. Zeta potential explained colloidal stability across treatments; surface charge was calculated with surface complexation models and explained for phytic acid (PA) and hexametaphosphate (HMP) by a partial (1-4 of the 6 PO4 units) adsorption to the surface, while the remaining PO4 units stayed in solution. This study suggests that Ca concentration mainly affects the mobility of natural or engineered PO4-Fe-NPs and that HMP is a promising agent for increasing colloidal stability.
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| 19. |
- Cornelis, Geert
(författare)
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Secondary gold structures: Relics of past biogeochemical transformations and implications for colloidal gold dispersion in subtropical environments
- 2017
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 450, s. 154-164
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Tidskriftsartikel (refereegranskat)abstract
- Biogeochemical processes are known to drive the cycling of gold via dissolution/re-precipitation reactions that result in the transformation of gold grain in near-surface environments. In this study, placer gold grains were collected from West Coast Creek, Queensland, Australia and characterized using high-resolution electron microscopy. The outer surface of grains contains 98.1 mol%Au and 1.9 mol%Ag. Crevices occur on the surface of grains and are filled with organics and clay minerals in which nanometer-size gold colloids and micrometer-sized octahedral gold platelets are embedded. The formation of these secondary gold structures is attributed to gold precipitation by the availability of reducing agents such as microbiota, residual organics and clays. Bacterioform gold contains 74.7 mol%Au and 25.3 mol% Ag and is also embedded in clay minerals within crevices. From sonicated gold grains, grain surfaces beneath the clay minerals are striated and contain 68.5mol%Au and 31.5mol%Ag. This data suggests that dissolution processes occur at the gold grain interface. Varying sizes of gold colloids on the grains suggest that five 'episodes' of gold dissolution/re-precipitation processes occurred; each episode was estimated to be 7.64 +/- 4.1 years. Therefore, these grains represent 17.9-58.5 years of gold cycling and mobilization within this subtropical environment. Furthermore, laboratory experiments involving colloidal gold dispersion demonstrated that iron-oxides and organic material from West Coast Creek sediment adsorbed 94.5% of suspended gold colloids. In conclusion, this study highlights the value of nanophase gold characterization for the interpretation of biogeochemical processes affecting gold grain transformation and mobility in near-surface environments. Importantly, this study is the first to estimate the kinetics of biogeochemical gold cycling with regards to colloidal gold dispersion and re-concentration.(C) 2016 Elsevier B.V. All rights reserved.
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| 20. |
- Cornelis, Geert
(författare)
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Sludge concentration, shear rate and nanoparticle size determine silver nanoparticle removal during wastewater treatment
- 2017
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Ingår i: Environmental Science: Nano. - 2051-8153 .- 2051-8161. ; 4, s. 2225-2234
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Tidskriftsartikel (refereegranskat)abstract
- Wastewater treatment (WWT) is generally efficient in removing nanoparticles (NPs) from sewage effluent, but the variety in removal rates has not yet been explained. WWT parameters such as the activated sludge (AS) concentration, shear rate and ionic strength were varied in kinetic batch attachment and sedimentation studies using silver NPs having nominal 20 or 80 nm sizes and citrate or PEG coatings. The fitted attachment and detachment rate constants and the resulting distribution ratios at steady state varied with WWT process parameters, but most notably with the NP size, which was also found to influence the settling rates most. The NP coating molecules had a limited or no effect. A meta-analysis of literature distribution ratios (attached/detached concentration) of NPs composed of Ag and other materials showed the NP (aggregate) size as the only significant parameter. However, while the distribution ratio of silver NPs to AS increased linearly with AS concentration, the final effect of NP effluent concentrations is partly offset by decreased sedimentation rates. The results thus confirm that a WWT process is efficient in removing NPs from wastewater, but relatively small (<20 nm) non-aggregated NPs are somewhat more likely to exit a WWT process via the effluent into aquatic compartments compared to relatively larger NPs, which nearly entirely leave the WWT plants with the AS towards soils, incineration plants or landfills.
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| 21. |
- Cornelis, Geert, et al.
(författare)
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Solubility and transport of Cr(III) in a historically contaminated soil – Evidence of a rapidly reacting dimeric Cr(III) organic matter complex
- 2017
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 189, s. 709-716
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Tidskriftsartikel (refereegranskat)abstract
- Chromium is a common soil contaminant and, although it has been studied widely, questions about its speciation and dissolutions kinetics remain unanswered. We combined information from an irrigation experiment performed with intact soil columns with data from batch experiments to evaluate solubility and mobilization mechanisms of Cr(III) in a historically contaminated soil (>65 years). Particulate and colloidal Cr(III) forms dominated transport in this soil, but their concentrations were independent of irrigation intensity (2-20 mm h(-1)). Extended X-ray absorption fine structure (EXAFS) measurements indicated that Cr(III) associated with colloids and particles, and with the solid phase, mainly existed as dimeric hydrolyzed Cr(III) bound to natural organic matter. Dissolution kinetics of this species were fast (<= 1 day) at low pH (<3) and slightly slower (<= 5 days) at neutral pH. Furthermore, it proved possible to describe the solubility of the dimeric Cr(III) organic matter complex with a geochemical equilibrium model using only generic binding parameters, opening the way for use of geochemical models in risk assessments of Cr(III)-contaminated sites. (C) 2017 The Authors. Published by Elsevier Ltd.
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| 22. |
- Cornelis, Geert
(författare)
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TiO2 nanomaterial detection in calcium rich matrices by spICPMS. A matter of resolution and treatment
- 2017
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477. ; 32, s. 1400-1411
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Tidskriftsartikel (refereegranskat)abstract
- High Ca concentrations in complex matrices such as river waters often hamper the detection of titanium nanomaterials (TiO2 NPs) by single particle inductively coupled plasma mass spectrometry (spICPMS), because of isobaric interference of Ca-48 on the most abundant Ti isotope (Ti-48). Several approaches were used to reduce this interference while measuring TiO2 in solutions with different Ca concentrations up to 100 mg L-1. ICP-MS/MS was used with ammonia as the reaction ceLL gas and high resoLution (HR) ICP-MS was used under different resoLution settings. These approaches were compared by measuring different Ti isotopes (Ti-47 and Ti-49). spICPMS data were then treated with a deconvoLution method to filter out dissolved signals and identify the best approach to detect the Lowest possible corresponding spherical size of TiO2 NPs (D,in). ICP-MS/MS aLLowed for an important decrease of the theoretical D-min compared to standard quadrupole ICP-MS, down to 64 nm in uLtrapure water; however the sensitivity was reduced by the reaction gas and increasing Ca concentrations also increased the D-min. The comparably higher sensitivity of HR-ICP-MS aLLowed for theoretically measuring a D-min of 10 nm in uLtrapure water. Combined with the deconvoLution analysis, the highest resoLution mode in HR-ICP-MS Leads to the Lowest D-min at high Ca concentrations, even though significant broadening of the measured mass distributions occurred for TiO2 NPs at Ca concentrations up to 100 mg L-1.
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| 23. |
- Cornelis, Geert
(författare)
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Toxicokinetics of Ag from Ag2S NP exposure in Tenebrio molitor and Porcellio scaber: Comparing single-species tests to indoor mesocosm experiments
- 2023
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Ingår i: NanoImpact. - : Elsevier BV. - 2452-0748. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- Determining the potential for accumulation of Ag from Ag2S NPs as an environmentally relevant form of AgNPs in different terrestrial organisms is an essential component of a realistic risk assessment of AgNP emissions to soils. The objectives of this study were first to determine the uptake kinetics of Ag in mealworms (Tenebrio molitor) and woodlice (Porcellio scaber) exposed to Ag2S NPs in a mesocosm test, and second, to check if the obtained toxicokinetics could be predicted by single-species bioaccumulation tests. In the mesocosms, meal-worms and woodlice were exposed together with plants and earthworms in soil columns spiked with 10 mu g Ag g(-1) dry soil as Ag2S NPs or AgNO3. The total Ag concentrations in the biota were measured after 7, 14, and 28 days of exposure. A one-compartment model was used to calculate the Ag uptake and elimination rate constants. Ag from Ag2S NPs appeared to be taken up by the mealworms with significantly different uptake rate constants in the mesocosm compared to single-species tests (K-1 = 0.056 and 1.66 g dry soil g(-1) dry body weight day(-1), respectively), and a significant difference was found for the Ag bioaccumulation factor (BAFk = 0.79 and 0.15 g dry soil g(-1) dry body weight, respectively). Woodlice did not accumulate Ag from Ag2S NPs in both tests, but uptake from AgNO3 was significantly slower in mesocosm than in single-species tests (K-1 = 0.037 and 0.26 g dry soil g(-1) dry body weight day(-1), respectively). Our results are of high significance because they show that single-species tests may not be a good predictor for the Ag uptake in mealworms and woodlice in exposure systems having greater levels of biological complexity. Nevertheless, single-species tests could be used as a fast screening approach to assess the potential of a substance to accumulate in biota before more complex tests are conducted.
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| 24. |
- Cornelis, Geert
(författare)
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Where is the nano? Analytical approaches for the detection and quantification of TiO2 engineered nanoparticles in surface waters
- 2018
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 5, s. 313-326
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Tidskriftsartikel (refereegranskat)abstract
- Detecting and quantifying engineered nanoparticles (ENPs) in complex environmental matrices requires the distinction between natural nanoparticles (NNPs) and ENPs. The distinction of NNPs and ENPs for regulatory purposes calls for cost-efficient methods, but is hampered by similarities in intrinsic properties, such as particle composition, size, density, surface chemistry, etc. Titanium dioxide (TiO2) ENPs, for instance, are produced in very large quantities but Ti also commonly occurs naturally in nano-scale minerals. In this work, we focus on utilizing particle size and composition to identify ENPs in a system with a significant background concentration of the target metal. We have followed independent approaches involving both conventional and state-of-the-art analytical techniques to detect and quantify TiO2 ENPs released into surface waters from sunscreen products and to distinguish them from Ti-bearing NNPs. To achieve this, we applied single particle inductively coupled plasma mass spectrometry with single-element (spICPMS) and multi-element detection (time-of-flight) spICP-TOFMS, together with transmission electron microscopy (TEM), automated scanning electron microscopy (autoSEM), and bulk elemental analyses. A background concentration of Ti-bearing NPs (approximately 5 x 10(3) particles per ml), possibly of natural origin, was consistently observed outside the bathing season. This concentration increased by up to 40% during the bathing season. Multi-element analysis of individual particles using spICP-TOFMS revealed that Al, Fe, Mn, and Pb are often present in natural Ti-bearing NPs, but no specific multi-element signatures were detected for ENPs. Our data suggests that TiO2 ENPs enter the lake water during bathing activities, eventually agglomerating and sedimenting. We found adhesion of the TiO2 ENPs to the air-water interface for short time periods, depending on wind conditions. This study demonstrates that the use of spICP-TOFMS and spICPMS in combination with other conventional analytical techniques offers significant advantages for discriminating between NNPs and ENPs. The quantitative data produced in this work can be used as input for modeling studies or as a benchmark for analysis protocols and model validations.
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| 25. |
- Doolette, Casey L, et al.
(författare)
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Transformation of PVP coated silver nanoparticles in a simulated wastewater treatment process and the effect on microbial communities.
- 2013
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Ingår i: Chemistry Central Journal. - 1752-153X. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Manufactured silver nanoparticles (AgNPs) are one of the most commonly used nanomaterials in consumer goods and consequently their concentrations in wastewater and hence wastewater treatment plants are predicted to increase. We investigated the fate of AgNPs in sludge that was subjected to aerobic and anaerobic treatment and the impact of AgNPs on microbial processes and communities. The initial identification of AgNPs in sludge was carried out using transmission electron microscopy (TEM) with energy dispersive X-ray (EDX) analysis. The solid phase speciation of silver in sludge and wastewater influent was then examined using X-ray absorption spectroscopy (XAS). The effects of transformed AgNPs (mainly Ag-S phases) on nitrification, wastewater microbial populations and, for the first time, methanogenesis was investigated. RESULTS: Sequencing batch reactor experiments and anaerobic batch tests, both demonstrated that nitrification rate and methane production were not affected by the addition of AgNPs [at 2.5 mg Ag L-1 (4.9 g L-1 total suspended solids, TSS) and 183.6 mg Ag kg -1 (2.9 g kg-1 total solids, TS), respectively].The low toxicity is most likely due to AgNP sulfidation. XAS analysis showed that sulfur bonded Ag was the dominant Ag species in both aerobic (activated sludge) and anaerobic sludge. In AgNP and AgNO3 spiked aerobic sludge, metallic Ag was detected (~15%). However, after anaerobic digestion, Ag(0) was not detected by XAS analysis. Dominant wastewater microbial populations were not affected by AgNPs as determined by DNA extraction and pyrotag sequencing. However, there was a shift in niche populations in both aerobic and anaerobic sludge, with a shift in AgNP treated sludge compared with controls. This is the first time that the impact of transformed AgNPs (mainly Ag-S phases) on anaerobic digestion has been reported. CONCLUSIONS: Silver NPs were transformed to Ag-S phases during activated sludge treatment (prior to anaerobic digestion). Transformed AgNPs, at predicted future Ag wastewater concentrations, did not affect nitrification or methanogenesis. Consequently, AgNPs are very unlikely to affect the efficient functioning of wastewater treatment plants. However, AgNPs may negatively affect sub-dominant wastewater microbial communities.
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