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The recent expansion of single particle inductively coupled plasma mass spectrometry (spICP-MS) for analysis of inorganic nanoparticles (NPs) in environmental and laboratory samples requires continued method development to ensure accurate characterization. Spectral interferences in spICP-MS analysis are often not fully addressed, especially particle generated interferences. Discrete ion clouds from ablated NPs entering the plasma form doubly charged and polyatomic species in a manner similar to dissolved ions that contribute to the continuous background signal. spICP-MS analysis of Y- and Nd-NP suspensions resulted in NP detections that are falsely identified as Pd, Ge, and As NPs due to interferences of YO+ and Nd2+. Use of a dynamic reaction cell (DRC) eliminated YO+ interferences, while Pd NPs were still accurately measured in mixed suspensions of Pd- and Y-NPs. A strong correlation was observed between the magnitude of interferences in solution mode and single particle mode, supporting a similar mechanism of interferent formation in the plasma for dissolved and NP-associated ions. Additionally, interference formation was affected by changes in nebulizer gas flow in a manner similar to dissolved ions. We conclude that particle generated interferences must be avoided or eliminated to ensure accurate nanometrology. [ABSTRACT FROM AUTHOR]

We monitored physical–chemical conditions in the North Fork of Clear Creek in Colorado (USA) before, during, and after the start of remediation (lime treatment) to remove metals from two major inputs of acid mine drainage (AMD) water. In addition, we analyzed historical monitoring data that extended back more than two decades. Concentration–discharge (C–D) and load–discharge (L–D) plots accounted for discharge dependence in concentrations and loads of metals, major ions, and other water chemistry parameters. Total and dissolved concentrations, and loads of the metals decreased after remediation began, with the largest decreases usually during low stream flow. However, postremediation concentrations and loads remained slightly to considerably higher than reference, probably because of unidentified groundwater seeps and/or small surface flows. Dissolved Cu concentrations decreased much less than total Cu concentrations, because the percentage of total Cu in the dissolved phase increased considerably as particulate Fe (PFe) concentration decreased. We conclude that 1) water chemistry can change to a new steady state or pseudo‐steady state relatively quickly after major AMD inputs to a stream are remediated; 2) elevated flows during snowmelt and rainfall periods can mobilize additional amounts of major ions and metals, resulting in in‐stream concentrations that are manifestations of both dilution and mobilization; 3) although lime treatment of AMD‐related waters can decrease metal concentrations, it does not decrease elevated concentrations of major ions that might impair sensitive stream invertebrates; 4) although Fe is toxic to aquatic organisms, PFe adsorbs other metals and thereby provides protection against their toxicity; and 5) use of C–D and L–D plots and element ratios can indicate the presence of unidentified AMD inputs to a stream. Environ Toxicol Chem 2023;42:495–511. © 2022 SETAC [ABSTRACT FROM AUTHOR]

Responses of stream ecosystems to gradual reductions in metal loading following remediation or restoration activities have been well documented in the literature. However, much less is known about how these systems respond to the immediate or more rapid elimination of metal inputs. Construction of a water treatment plant on the North Fork of Clear Creek (NFCC; CO, USA), a US Environmental Protection Agency Superfund site, captured, diverted, and treated the two major point‐source inputs of acid mine drainage (AMD) and provided an opportunity to investigate immediate improvements in water quality. We conducted a 9‐year study that included intensive within‐ and among‐year monitoring of receiving‐stream chemistry and benthic communities before and after construction of the treatment plant. Results showed a 64%–86% decrease in metal concentrations within months at the most contaminated sites. Benthic communities responded with increased abundance and diversity, but downstream stations remained impaired relative to reference conditions, with significantly lower taxonomic richness represented by a few dominant taxa (i.e., Baetis sp., Hydropsyche sp., Simulium sp., Orthocladiinae). Elevated metal concentrations from apparent residual sources, and relatively high conductivity from contributing major ions not removed during the treatment process, are likely limiting downstream recovery. Our study demonstrates that direct AMD treatment can rapidly improve water quality and benefit aquatic life, but effectiveness is limited, in part, to the extent that inputs of metals are captured and treated. Consideration should also be given to the effects of elevated major ion concentrations from the treated effluent not removed during the lime treatment process. Continued chemical and biological monitoring will be needed to quantify the NFCC recovery trajectory and to inform future remediation strategies. Environ Toxicol Chem 2023;42:512–524. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Transport of colloids (diameter < 1 [micro]m) through soil has implications for both horizon development and contaminant mobility. Colloid physical properties (size, shape), mineralogy, and surface chemistry are known to influence transport and deposition. Sedimentation field-flow fractionation-inductively coupled plasma--mass spectrometry (Sd FFF-ICP-MS) was used to examine size and element composition distributions of colloids collected from the profile of a texture-contrast soil located in South Australia. The morphology of the colloids was also examined by transmission electron microscopy (TEM). Colloids collected from the soil matrix, the source of mobile colloids, had significant differences in the size distributions among the three horizons sampled. These differences were consistent with long-term soil formation processes. Colloids mobilized by rainfall, which were collected from overland flow and infiltration through the soil profile, all showed very similar size distributions. This is consistent with the presence of preferential flow paths and suggests that colloids, and colloid-associated contaminants, can be transported rapidly through the vadose zone with minimal interaction with the soil matrix. The Sd FFF-ICP-MS analysis showed variation in element ratios (Fe/Al, Mg/Al), which were used to detect changes in surface coatings and mineralogy over the colloid size range. The study demonstrated the utility of Sd FFF-ICP-MS for examining the influence of colloid size on element composition and on elucidating colloid transport processes in soils.

Field flow fractionation (FFF) is a size-based separation technique applicable to biomolecules, colloids, and bacteria in solution. When interfaced with ICPMS on-line, elemental data can be collected concurrent with size distribution. We employed hyperlayer flow FFF (F1 FFF) methodology to separate cells of Shewanella oneidensis strain MR-1 from exopolymers present in washed cell suspensions. With a channel flow of 4 mL [min.sup.-1] and a cross-flow of 0.4 mL [min.sup.-1] cells eluted with a retention time of 4.7 min corresponding to an approximate equivalent spherical cell diameter of 0.8 [micro]m. Cell suspensions were amended with increasing concentrations of U to establish an adsorption isotherm and with fixed U concentrations at varying pH to establish the pH dependence of sorption. A linear sorption isotherm was determined for U solution concentrations of 0.2-16 [micro]M, maximum U sorption occurred at pH 5. A high molecular weight compound, presumably a cell exudate, was identified by F1 FFF-ICPMS. This cell exudate complexed U, and at elevated pH, the exudate appeared to have a greater affinity for U than cell surfaces. Thus, F1 FFF interfaced with ICPMS detection is a powerful analytical technique for metal sorption studies with bacteria; analysis can be carried out on small sample volumes (25 [micro]L) and additional speciation information can be gained because of the versatile FI FFF separation range and multielement detection capabilities of ICPMS.