Comparative study of the elemental composition of metal(loid)-bearing nanomaterials in wildland-urban interface fire ashes using icp-TOF-MS

Abstract

This study investigates the abundance and elemental composition of metal(loid)c incidental nanomaterials (INMs) in wildland-urban interface (WUI) fire ashes from different sources, including vegetation, structures, and vehicles, collected following the 2020 LNU (the Sonoma-Lake-Napa unit) Lightning Complex Fire in California. Particle number concentrations, elemental compositions and ratios, and size distributions were determined by single particle inductively coupled plasma-time of flight-mass spectrometry (SP-ICP-TOF-MS) coupled with automated two-stage hierarchical clustering analysis. Particle morphologies, elemental compositions, and size were identified by transmission electron microscopy coupled with including energy dispersive X-ray spectroscopy. Iron- and Mn-bearing INMs accounted for >80% of INMs detected in vegetation and atmospheric deposition ashes but they represented <50% of all INMs in structural and vehicle ashes. Together, Al, Ba, Cr, Cu, Ti, Pb, and Zn-bearing INMs accounted for 45 to 75% of all INMs in structural and vehicle ashes and 7 to 13% in vegetation and atmospheric deposition ashes. The sizes of INMs varied between a few tens to a few hundreds of nanometers with larger Ba, Cr, Fe, Ti, Pb, and Zn-bearing INMs in structural and vehicles ashes than in vegetation ashes. Several types of multi-element INMs were identified by SP-ICP-TOF-MS including chromated-copper-arsenate-related NMs (e.g., CuCrO2, CuCr2O4, CrAsO4); CuSn and CuPb alloys; SnPb, SbPb, and SnSb alloys; and CoAl alloys. Overall, this study demonstrates the abundance and elemental makeup of various metal(loid)c INMs in WUI fire ashes. This study highlights the need for further research opportunities into the discovery, transformation, reactivity, fate, and effects of INMs during and following WUI fires.