The lack of an efficient and standardized method to disperse soil particles and quantitatively subsample the nanoparticulate fraction for characterization analyses is hindering progress in assessing the fate and toxicity of metallic engineered nanomaterials in the soil environment. This study investigates various soil extraction and extract preparation techniques for their ability to remove nanoparticulate Ag from a field soil amended with biosolids contaminated with engineered silver nanoparticles (AgNPs), while presenting a suitable suspension for quantitative single-particle inductively coupled plasma mass spectroscopy (SP-ICP-MS) analysis. Extraction parameters investigated included reagent type (water, NaNO, KNO, tetrasodium pyrophosphate (TSPP), tetramethylammonium hydroxide (TMAH)), soil-to-reagent ratio, homogenization techniques as well as procedures commonly used to separate nanoparticles from larger colloids prior to analysis (filtration, centrifugation, and sedimentation). We assessed the efficacy of the extraction procedure by testing for the occurrence of potential procedural artifacts (dissolution, agglomeration) using a dissolved/particulate Ag mass ratio and by monitoring the amount of Ag mass in discrete particles. The optimal method employed 2.5 mM TSPP used in a 1:100 (m/v) soil-to-reagent ratio, with ultrasonication to enhance particle dispersion and sedimentation to settle out the micrometer-sized particles. A spiked-sample recovery analysis shows that 96% ± 2% of the total Ag mass added as engineered AgNP is recovered, which includes the recovery of 84.1% of the particles added, while particle recovery in a spiked method blank is ∼100%, indicating that both the extraction and settling procedure have a minimal effect on driving transformation processes. A soil dilution experiment showed that the method extracted a consistent proportion of nanoparticulate Ag (9.2% ± 1.4% of the total Ag) in samples containing 100%, 50%, 25%, and 10% portions of the AgNP-contaminated test soil. The nanoparticulate Ag extracted by this method represents the upper limit of the potentially dispersible nanoparticulate fraction, thus providing a benchmark with which to make quantitative comparisons, while presenting a suspension suitable for a myriad of other characterization analyses.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/es500141hEnvironmental Science and Technology, 48, 14, pp. 8135-8142, 2014-06-10 ABSTRACT: Soil toxicity tests for metal oxide nanoparticles often include micrometer-sized oxide and metal salt treatments to distinguish between toxicity from nanometer-sized particles, non-nanometer-sized particles, and dissolved ions. Test result will be confounded if each chemical form has different effects on soil solution chemistry. We report on changes in soil solution chemistry over 56 daysthe duration of some standard soil toxicity testsin three soils amended with 500 mg/kg Cu as nanometer-sized CuO (nano), micrometer-sized CuO (micrometer), or Cu(NO 3 ) 2 (salt). In the CuO-amended soils, the log Cu 2+ activity was initially low (minimum −9.48) and increased with time (maximum −5.20), whereas in the salt-amended soils it was initially high (maximum −4.80) and decreased with time (minimum −6.10). The Cu 2+ activity in the nano-amended soils was higher than in the micrometer-amended soils for at least the first 11 days, and lower than in the saltamended soils for at least 28 d. The pH, and dissolved Ca and Mg concentrations in the CuO-amended soils were similar, but the salt-amended soils had lower pH for at least 14 d, and higher Ca and Mg concentrations throughout the test. Soil pretreatments such as leaching and aging prior to toxicity tests are suggested.

Nanometer-sized titanium dioxide (nano-TiO(2) ) is found in a number of commercial products; however, its effects on soil biota are largely unknown. In the present study, earthworms (Eisenia andrei and Eisenia fetida) were exposed to three types of commercially available, uncoated TiO(2) nanomaterials with nominal diameters of 5, 10, and 21 nm. Nanomaterials were characterized for particle size, agglomeration, surface charge, chemical composition, and purity. Standard lethality, reproduction, and avoidance tests, as well as a juvenile growth test, were conducted in artificial soil or field soil amended with nano-TiO(2) by two methods, liquid dispersion and dry powder mixing. All studies included a micrometer-sized TiO(2) control. Exposure to field and artificial soil containing between 200 and 10,000 mg nano-TiO(2) per kilogram of dry soil (mg/kg) had no significant effect (p > 0.05) on juvenile survival and growth, adult earthworm survival, cocoon production, cocoon viability, or total number of juveniles hatched from these cocoons. However, earthworms avoided artificial soils amended with nano-TiO(2) . The lowest concentration at which avoidance was observed was between 1,000 and 5,000 mg nano-TiO(2) per kilogram of soil, depending on the TiO(2) nanomaterial applied. Furthermore, earthworms differentiated between soils amended with 10,000 mg/kg nano-TiO(2) and micrometer-sized TiO(2) . A positive relationship between earthworm avoidance and TiO(2) specific surface area was observed, but the relationship between avoidance and primary particle size was not determined because of the agglomeration and aggregation of nano-TiO(2) materials. Biological mechanisms that may explain earthworm avoidance of nano-TiO(2) are discussed. Results of the present study indicate that earthworms can detect nano-TiO(2) in soil, although exposure has no apparent effect on survival or standard reproductive parameters.

1H NMR-based metabolomics was used to examine the response of Eisenia fetida earthworms raised from juveniles for 20–23 weeks in soil spiked with either 20 or 200 mg/kg of a commercially available uncoated titanium dioxide (TiO2) nanomaterial (nominal diameter of 5 nm). To distinguish responses specific to particle size, soil treatments spiked with a micrometer-sized TiO2 material (nominal diameter, <45 μm) at the same concentrations (20 and 200 mg/kg) were also included in addition to an unspiked control soil. Multivariate statistical analysis of the 1H NMR spectra for aqueous extracts of E. fetida tissue suggested that earthworms exhibited significant changes in their metabolic profile following TiO2 exposure for both particle sizes. The observed earthworm metabolic changes appeared to be consistent with oxidative stress, a proposed mechanism of toxicity for nanosized TiO2. In contrast, a prior study had observed no impairment of E. fetida survival, reproduction, or growth following exposure to the same TiO2 spiked soils. This suggests that 1H NMR-based metabolomics provides a more sensitive measure of earthworm response to TiO2 materials in soil and that further targeted assays to detect specific cellular or molecular level damage to earthworms caused by chronic exposure to TiO2 are warranted.

S2 Ion exchange technique (IET) theoryThe principles of IET have been previously outlined 28,30 . Briefly, a sample is passed through a column containing a known mass of a negatively-charged resin (mr) saturated with a readily exchangeable cation, usually Na + . Exchange occurs between the free metal ions in the sample, and the exchange cation on the resin until steady-state equilibrium conditions are achieved (i.e., the concentration of resin-bound metal is constant). The resin-bound metals are then extracted by passing an exact volume of eluate (e.g., 1.5 M HNO3) through the column from which the metal concentration can be determined. The concentration of resin-bound metal, [R-M] (mol g -1 ), is thus determined as: Details of the SP-ICP-MS analysisAs quantification of both the dissolved and nano-particulate forms of Ag are of interest, capturing both dissolved and particle signals is necessary; however, it is doubtful that one dilution/analysis can optimally capture both signals. We have previously developed an approach for the analysis of samples containing high levels of dissolved analyte [36] , whereby a sample dilution series is used as follows:1. The first dilution allows for the capture of the dissolved analyte signal within the dissolved calibration range and above the LoQ.