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NanoEarth: Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure

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Browsing NanoEarth: Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure by Author "Alpers, Charles N."

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    Discovery and potential ramifications of reduced iron-bearing nanoparticles-magnetite, wustite, and zero-valent iron-in wildland-urban interface fire ashes
    Baalousha, Mohammed; Desmau, Morgane; Singerling, Sheryl A.; Webster, Jackson P.; Matiasek, Sandrine J.; Stern, Michelle A.; Alpers, Charles N. (Royal Society Chemistry, 2022-11)
    The increase in fires at the wildland-urban interface has raised concerns about the potential environmental impact of ash remaining after burning. Here, we examined the concentrations and speciation of iron-bearing nanoparticles in wildland-urban interface ash. Total iron concentrations in ash varied between 4 and 66 mg g(-1). Synchrotron X-ray absorption near-edge structure (XANES) spectroscopy of bulk ash samples was used to quantify the relative abundance of major Fe phases, which were corroborated by transmission electron microscopy measurements. Maghemite (gamma-(Fe3+)(2)O-3) and magnetite (gamma-Fe2+(Fe3+)(2)O-4) were detected in most ashes and accounted for 0-90 and 0-81% of the spectral weight, respectively. Ferrihydrite (amorphous Fe(iii)-hydroxide, (Fe3+)(5)HO8 center dot 4H(2)O), goethite (alpha-Fe3+OOH), and hematite (alpha-Fe23+O3) were identified less frequently in ashes than maghemite and magnetite and accounted for 0-65, 0-54, and 0-50% of spectral weight, respectively. Other iron phases identified in ashes include wustite (Fe2+O), zerovalent iron, FeS, FeCl2, FeCl3, FeSO4, Fe-2(SO4)(3), and Fe(NO3)(3). Our findings demonstrate the impact of fires at the wildland-urban interface on iron speciation; that is, fires can convert iron oxides (e.g., maghemite, hematite, and goethite) to reduced iron phases such as magnetite, wustite, and zerovalent iron. Magnetite concentrations (e.g., up to 25 mg g(-1)) decreased from black to gray to white ashes. Based on transmission electron microscopy (TEM) analyses, most of the magnetite nanoparticles were less than 500 nm in size, although larger particles were identified. Magnetite nanoparticles have been linked to neurodegenerative diseases as well as climate change. This study provides important information for understanding the potential environmental impacts of fires at the wildland-urban interface, which are currently poorly understood.
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    Identification and quantification of Cr, Cu, and As incidental nanomaterials derived from CCA-treated wood in wildland-urban interface fire ashes
    Alam, Mahbub; Alshehri, Talal; Wang, Jingjing; Singerling, Sheryl A.; Alpers, Charles N.; Baalousha, Mohammed (Elsevier, 2023-03-05)
    In addition to the combustion of vegetation, fires at the wildland-urban interface (WUI) burn structural mate-rials, including chromated copper arsenate (CCA)-treated wood. This study identifies, quantifies, and charac-terizes Cr-, Cu-, and As-bearing incidental nanomaterials (INMs) in WUI fire ashes collected from three residential structures suspected to have originated from the combustion of CCA-treated wood. The total elemental concentrations were determined by inductively coupled plasma-time of flight-mass spectrometry (ICP-TOF-MS) following acid digestion. The crystalline phases were determined using transmission electron micro-scopy (TEM), specifically using electron diffraction and high-resolution imaging. The multi-element single particle composition and size distribution were determined by single particle (SP)-ICP-TOF-MS coupled with agglomerative hierarchical clustering analysis. Chromium, Cu, and As are the dominant elements in the ashes and together account for 93%, 83%, and 24% of the total mass of measured elements in the ash samples. Chromium, Cu, and As phases, analyzed by TEM, most closely match CrO3, CrO2, eskolaite (Cr2O3), CuCrO2, CuCr2O4, CrAs2O6, As2O5, AsO2, claudetite (As2O3, monoclinic), or arsenolite (As2O3, cubic), although a bona fide phase identification for each particle was not always possible. These phases occur predominantly as het-eroaggregates. Multi-element single particle analyses demonstrate that Cr occurs as a pure phase (i.e., Cr oxides) as well as in association with other elements (e.g., Cu and As); Cu occurs predominantly in association with Cr and As; and As occurs as As oxides and in association with Cu and Cr. Several Cr, Cu, and As clusters were identified and the molar ratios of Cr/Cu and Cr/As within these clusters are consistent with the crystalline phases identified by TEM as well as their heteroaggregates. These results indicate that WUI fires can lead to significant release of CCA constituents and their combustion-transformed by-products into the surrounding environment. This study also provides a method to identify and track CCA constituents in environmental systems based on multi-element analysis using SP-ICP-TOF-MS.
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    Wildland-urban interface fire ashes as a major source of incidental nanomaterials
    Alshehri, Talal; Wang, Jingjing; Singerling, Sheryl A.; Gigault, Julien; Webster, Jackson P.; Matiasek, Sandrine J.; Alpers, Charles N.; Baalousha, Mohammed (Elsevier, 2023-02-05)
    Although metal and metalloid concentrations in wildfire ashes have been documented, the nature and concen-trations of incidental nanomaterials (INMs) in wildland-urban interface (WUI) fire ashes have received consid-erably less attention. In this study, the total metal and metalloid concentrations of 57 vegetation, structural, and vehicle ashes and underlying soils collected at the WUI following the 2020 fire season in northern California - North Complex Fire and LNU Lightning Complex Fire - were determined using inductively coupled plasma-time of flight-mass spectrometry after microwave-assisted acid digestion. The concentrations of Ti, Zn, Cu, Ni, Pb, Sn, Sb, Co, Bi, Cr, Ba, As, Rb, and W are generally higher in structural/vehicle-derived ashes than in vegetation -derived ashes and soils. The concentrations of Ca, Sr, Rb, and Ag increased with increased combustion completeness (e.g., black ash < gray ash < white ash), whereas those of C, N, Zn, Pb, and In decreased with increased combustion completeness. The concentration of anthropogenic Ti - determined by mass balance calculations and shifts in Ti/Nb above the natural background ratios - was highest in vehicle ash (median: 30.8 g kg -1, range: 4.5-41.0 g kg -1) followed by structural ash (median: 5.5 g kg -1, range: of 0-77.4 g kg -1). Various types of carbonaceous INM (e.g., amorphous carbon, turbostratic-like carbon, and carbon associated with zinc oxides) and metal-bearing INMs (e.g., Ti, Cu, Fe, Zn, Mn, Pb, and Cr) with sizes between few nanometers to few hundreds of nanometers were evidenced in ashes using transmission electron microscopy, including energy dispersive X-ray spectroscopy. Overall, this study demonstrates the abundance of a variety of metals and met-alloids in the form of INMs in WUI fire ashes. This study also highlights the need for further research into the formation, transformation, reactivity, fate, and effects of INMs during and following fires at the WUI.