Transformations of oxidized multiwalled carbon nanotubes exposed to UVC (254 nm) irradiation

Bitter, Julie L.; Yang, Jun; Milani, S.; Jafvert, Chad T.; Fairbrother, D. Howard

doi:10.1039/c4en00073k

Cited by 26 publications

(34 citation statements)

References 48 publications

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“…Overall, these chemical changes are consistent with expected surface alteration of highly condensed aromatic carbon substances by photo-oxidation (Chen and Jafvert, 2010; Bitter et al, 2014). Aromatic carbon readily absorbs UV light, and in the presence of oxygen and water leads to the oxidation and cleavage of the C=C bonds resulting in the formation of hydroxyl, carbonyl, and/or carboxylic groups (Bertilsson and Stefan, 1998; Wu et al, 2001).…”

Section: Discussionsupporting

confidence: 84%

Weathering of pyrogenic organic matter induces fungal oxidative enzyme response in single culture inoculation experiments

Gibson

Berry

Wang

et al. 2016

Organic Geochemistry

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The addition of pyrogenic organic matter (PyOM), the aromatic carbon-rich product of the incomplete combustion of plant biomass or fossil fuels, to soil can influence the rate of microbial metabolism of native soil carbon. The interaction of soil heterotrophs with PyOM may be governed by the surficial chemical and physical properties of PyOM that evolve with environmental exposure. We present results of a 36-day laboratory incubation investigating the interaction of a common white-rot fungus, Trametes versicolor, with three forms of 13C-enriched (2.08 atom% 13C) PyOM derived from Pinus ponderosa (450 °C): one freshly produced, and two artificially weathered (254 nm, UV light-water treatment and water-leaching alone). Analysis (FTIR, XPS) of the UV-weathered PyOM showed increased aliphatic C–H content and oxidation of aromatic carbon relative to both the original and water-leached PyOM. The addition of both weathered forms of PyOM stimulated (positively primed) fungal respiration of the growth media, while the unaltered PyOM mildly inhibited (negatively primed) respiration. Artificial weathering resulted in higher oxidative (laccase and peroxidase) enzyme activity than unaltered PyOM, possibly the result of a diminished capacity to bind reactive substrates and extracellular enzymes after weathering. However, and contrary to expectations, simple water-leached weathering resulted in a relatively higher enzyme activity and respiration than that of UV-weathering. The 13C content of respired CO2 indicated negligible fungal oxidation of PyOM for all treatments, demonstrating the overall low microbial reactivity of this high temperature PyOM. The increased enzymatic and positive priming response of T. versicolor to weathered PyOM highlights the importance of weathering-induced chemistry in controlling PyOM–microbe–soil carbon interactions.

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Section: Discussionsupporting

confidence: 84%

Weathering of pyrogenic organic matter induces fungal oxidative enzyme response in single culture inoculation experiments

Gibson

Berry

Wang

et al. 2016

Organic Geochemistry

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“…94 Some species on ENM surfaces may degrade in the environment, 238 while other adsorbates can be acquired. 239, 240 Carbonaceous ENMs may be transformed or degraded by environmental processes such as photo-, 241, 242 enzymatic, 243, 244 chemical, 245 and biodegradation. 246 Redox and other environmental conditions will affect nanomaterial surfaces, which for nano-Ag includes formation of sulfide that inhibits dissolution.…”

Section: What Is the State Of Knowledge Regarding Enm Environmental Ementioning

confidence: 99%

Considerations of Environmentally Relevant Test Conditions for Improved Evaluation of Ecological Hazards of Engineered Nanomaterials

Holden

Gardea‐Torresdey

Klaessig

et al. 2016

Environ. Sci. Technol.

199

150

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Engineered nanomaterials (ENMs) are increasingly entering the environment with uncertain consequences including potential ecological effects. Various research communities view differently whether ecotoxicological testing of ENMs should be conducted using environmentally relevant concentrations—where observing outcomes is difficult—versus higher ENM doses, where responses are observable. What exposure conditions are typically used in assessing ENM hazards to populations? What conditions are used to test ecosystem-scale hazards? What is known regarding actual ENMs in the environment, via measurements or modeling simulations? How should exposure conditions, ENM transformation, dose, and body burden be used in interpreting biological and computational findings for assessing risks? These questions were addressed in the context of this critical review. As a result, three main recommendations emerged. First, researchers should improve ecotoxicology of ENMs by choosing test endpoints, duration, and study conditions—including ENM test concentrations—that align with realistic exposure scenarios. Second, testing should proceed via tiers with iterative feedback that informs experiments at other levels of biological organization. Finally, environmental realism in ENM hazard assessments should involve greater coordination among ENM quantitative analysts, exposure modelers, and ecotoxicologists, across government, industry, and academia.

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“…Hydrolysis is not expected to be a significant environmental degradation pathway for CNTs 30 . Photodegradation of CNTs has been shown to transform CNTs by changing their surface chemistry 31 or causing a loss of fluorescence when hydrogen peroxide was also present 32, 33 , but complete degradation has not been confirmed. Neither pure fungal cultures of white rot fungi, Trametes versicolor , nor environmental microbial communities degraded radioactively-labeled SWCNTs after a six-month incubation period 34 .…”

Section: Introductionmentioning

confidence: 99%

Increasing evidence indicates low bioaccumulation of carbon nanotubes

Bjorkland

Tobias

Petersen

2017

Environ. Sci.: Nano

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As the production of carbon nanotubes (CNTs) expands, so might the potential for release into the environment. The possibility of bioaccumulation and toxicological effects has prompted research on their fate and potential ecological effects. For many organic chemicals, bioaccumulation properties are associated with lipid-water partitioning properties. However, predictions based on phase partitioning provide a poor fit for nanomaterials. In the absence of data on the bioaccumulation and other properties of CNTs, the Office of Pollution Prevention and Toxics (OPPT) within the US Environmental Protection Agency (EPA) subjects new pre-manufacture submissions for all nanomaterials to a higher-level review. We review the literature on CNT bioaccumulation by plants, invertebrates and non-mammalian vertebrates, summarizing 40 studies to improve the assessment of the potential for bioaccumulation. Because the properties and environmental fate of CNTs may be affected by type (single versus multiwall), functionalization, and dosing technique, the bioaccumulation studies were reviewed with respect to these factors. Absorption into tissues and elimination behaviors across species were also investigated. All of the invertebrate and non-mammalian vertebrate studies showed little to no absorption of the material from the gut tract to other tissues. These findings combined with the lack of biomagnification in the CNT trophic transfer studies conducted to date suggest that the overall risk of trophic transfer is low. Based on the available data, in particular the low levels of absorption of CNTs across epithelial surfaces, CNTs generally appear to form a class that should be designated as a low concern for bioaccumulation.

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Transformations of oxidized multiwalled carbon nanotubes exposed to UVC (254 nm) irradiation

Abstract: Motivated by the ability of UVC radiation to destroy harmful pathogens in drinking and waste water treatment plants, we have investigated the effect of 254 nm (UVC) radiation on the physical and chemical properties of oxidized multiwalled carbon nanotube (O-MWCNT) suspensions.

Cited by 26 publications

References 48 publications

Weathering of pyrogenic organic matter induces fungal oxidative enzyme response in single culture inoculation experiments

Weathering of pyrogenic organic matter induces fungal oxidative enzyme response in single culture inoculation experiments

Considerations of Environmentally Relevant Test Conditions for Improved Evaluation of Ecological Hazards of Engineered Nanomaterials

Increasing evidence indicates low bioaccumulation of carbon nanotubes

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