Comparative study of dissolved and nanoparticulate Ag effects on the life cycle of an estuarine meiobenthic copepod, <i>Amphiascus tenuiremis</i>

<p>Many nanotoxicological studies have assessed the acute toxicity of nanoparticles (NPs) at high exposure concentrations. There is a gap in understanding NP chronic environmental effects at lower exposure concentrations. This study reports life-cycle chronic toxicity of sublethal exposures of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) relative to dissolved silver nitrate (AgNO₃) for the estuarine meiobenthic copepod, <i>Amphiascus tenuiremis</i>, over a range of environmentally relevant concentrations, i.e., 20, 30, 45, and 75 µg-Ag L⁻¹. A concentration-dependent increase in mortality of larval nauplii and juvenile copepodites was observed. In both treatment types, significantly higher mortality was observed at 45 and 75 µg-Ag L⁻¹ than in controls. In AgNO₃ exposures, fecundity declined sharply (1.8–7 fold) from 30 to 75 µg Ag L⁻¹. In contrast, fecundity was not affected by PVP-AgNPs exposures. A Leslie matrix population-growth model predicted sharply 60–86% of decline in overall population sizes and individual life-stage numbers from 30–75 µg-Ag L⁻¹ as dissolved AgNO₃. In contrast, no population growth suppressions were predicted for any PVP-AgNPs exposures. Slower release of dissolved Ag from PVP-AgNPs and/or reduced Ag uptake in the nanoform may explain these sharp contrasts in copepod response.</p

Characterization and Quantitative Analysis of Single-Walled Carbon Nanotubes in the Aquatic Environment Using Near-Infrared Fluorescence Spectroscopy

Near infrared fluorescence (NIRF) spectroscopy is capable of sensitive and selective detection of semiconductive, single-walled carbon nanotubes (SWNT) using the unique electronic bandgap properties of these carbon allotropes. We reported here the first detection and quantitation of SWNT in sediment and biota at environmentally relevant concentrations using NIRF spectroscopy. In addition, we utilized this technique to qualitatively characterize SWNT samples before and after ecotoxicity, bioavailability and fate studies in the aquatic environment. Sample preparation prior to NIRF analysis consisted of surfactant-assisted high power ultrasonication. The bile salt sodium deoxycholate (SDC) enabled efficient extraction and disaggregation of SWNT prior to NIRF analysis. The method was validated using standard-addition experiments in two types of estuarine sediments, yielding recoveries between 66 ± 7% and 103 ± 10% depending on SWNT type and coating used, demonstrating the ability to isolate SWNT from complex sediment matrices. Instrument detection limits were determined to be 15 ng mL^–1 SWNT in 2% SDC solution and method detection limits (including a concentration step) were 62 ng g^–1 for estuarine sediment, and 1.0 μg L^–1 for water. Our work has shown that NIRF spectroscopy is highly sensitive and selective for SWNT and that this technique can be applied to track the environmental and biological fate of this important class of carbon nanomaterial in the aquatic environment

Sediment Nickel Bioavailability and Toxicity to Estuarine Crustaceans of Contrasting Bioturbative Behaviors – An Evaluation of the SEM-AVS Paradigm

Robust sediment quality criteria require chemistry and toxicity data predictive of concentrations where population/community response <i>should</i> occur under known geochemical conditions. Understanding kinetic and geochemical effects on toxicant bioavailability is key, and these are influenced by infaunal sediment bioturbation. This study used fine-scale sediment and porewater measurement of contrasting infaunal effects on carbon-normalized SEM-AVS to evaluate safe or potentially toxic nickel concentrations in a high-binding <i>Spartina</i> saltmarsh sediment (4%TOC; 35–45 μmol-S^2–·g^–1). Two crustaceans producing sharply contrasting bioturbation -- the copepod <i>Amphiascus tenuiremis</i> and amphipod <i>Leptocheirus plumulosus</i> -- were cultured in oxic to anoxic sediments with SEM_[Ni]-AVS, TOC, porewater [Ni], and porewater DOC measured weekly. From 180 to 750 μg-Ni·g^–1sediment, amphipod bioturbation reduced [AVS] and enhanced porewater [Ni]. Significant amphipod uptake, mortality, and growth-depression occurred at the higher sediment [Ni] even when [SEM-AVS]/<i>f</i>_oc suggested acceptable risk. Less bioturbative copepods produced higher AVS and porewater DOC but exhibited net population <i>growth</i> despite porewater [Ni] 1.3–1.7× their aqueous [Ni] LOEC. Copepod aqueous tests with/without dissolved organic matter showed significant aqueous DOC protection, which suggests porewater DOC attenuates sediment Ni toxicity. The SEM_[Ni]-AVS relationship <i>was</i> predictive of acceptable risk for copepods at the important population-growth level

Effects of single-walled carbon nanotubes on the bioavailability of PCBs in field-contaminated sediments

<p>Adsorption of hydrophobic organic contaminants (HOCs) to black carbon is a well-studied phenomenon. One emerging class of engineered black carbon materials are single-walled carbon nanotubes (SWNTs). Little research has investigated the potential of SWNT to adsorb and sequester HOCs in complex environmental systems. This study addressed the capacity of SWNT, amended to polychlorinated biphenyl (PCB)-contaminated New Bedford Harbor (NBH) sediment, to reduce the toxicity and bioaccumulation of these HOCs to benthic organisms. Overall, SWNT amendments increased the survival of two benthic estuarine invertebrates, <i>Americamysis bahia</i> and <i>Ampelisca abdita</i>, and reduced the accumulation of PCBs to the benthic polychaete, <i>Nereis virens</i>. Reduction in PCB bioaccumulation by SWNT was independent of <i>K</i>_ow. Further, passive sampling-based estimates of interstitial water concentrations indicated that SWNT reduced PCB bioavailability. Results from this study suggest that SWNT are a good adsorbent for PCBs and might be useful for remediation in the future once SWNT manufacturing technology improves and costs decrease.</p

Silver Nanocolloids Disrupt Medaka Embryogenesis through Vital Gene Expressions

Silver nanomaterials are the major components of healthcare products largely because of their antimicrobial effects. However, their unintended toxicity to biological organisms and its mechanism are not well understood. Using medaka fish embryo model, the toxic effects and corresponding mechanisms of silver nanocolloids (SNC, particle size 3.8 ± 1.0-diameter nm) were investigated. SNC caused morphological changes in embryos including cardiovascular malformations, ischemia, underdeveloped central nervous system and eyes, and kyphosis at exposures of 0.5 mg/L. Interestingly, SNC were observed inside the eggs at a level of 786.1 ± 32.5 pg/mg egg weight, and TEM analysis showed that SNC adhered to the surface and inside of the chorion. Meanwhile, medaka oligo DNA microarray and qRT-PCR were used for gene expression analysis in the embryos exposed to 0.05 mg/L SNC for 48 h. As a result, expressions of six of the oxidative stress-, embryogenesis- and morphogenesis-related genes, <i>ctsL</i>, <i>tpm1</i>, <i>rbp</i>, <i>mt</i>, <i>atp2a1</i>, and <i>hox6b6</i>, were affected by the SNC exposure, and these genes’ involvement in those malformations was implied. Thus, SNC could potentially cause malformations in the cardiovascular and central nervous systems in developing medaka embryo through SNC-induced differential expression of the genes related to oxidative stress, embryonic cellular proliferation, and morphological development