Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, United States.
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, United States.
Chemosphere. 2024 Sep;363:142950. doi: 10.1016/j.chemosphere.2024.142950. Epub 2024 Jul 26.
Wildland-urban interface (WUI) fires consume fuels, such as vegetation and structural materials, leaving behind ash composed primarily of pyrogenic carbon and metal oxides. However, there is currently limited understanding of the role of WUI fire ash from different sources as a source of paramagnetic species such as environmentally persistent free radicals (EPFRs) and transition metals in the environment. Electron paramagnetic resonance (EPR) was used to detect and quantify paramagnetic species, including organic persistent free radicals and transition metal spins, in fifty-three fire ash and soil samples collected following the North Complex Fire and the Sonoma-Lake-Napa Unit (LNU) Lightning Complex Fire, California, 2020. High concentrations of organic EPFRs (e.g., 1.4 × 10 to 1.9 × 10 spins g) were detected in the studied WUI fire ash along with other paramagnetic species such as iron and manganese oxides, as well as Fe and Mn ions. The mean concentrations of EPFRs in various ash types decreased following the order: vegetation ash (1.1 × 10 ± 1.1 × 10 spins g) > structural ash (1.6 × 10 ± 3.7 × 10 spins g) > vehicle ash (6.4 × 10 ± 8.6 × 10 spins g) > soil (3.2 × 10 ± 3.7 × 10 spins g). The mean concentrations of EPFRs decreased with increased combustion completeness indicated by ash color; black (1.1 × 10 ± 1.1 × 10 spins g) > white (2.5 × 10 ± 4.4 × 10 spins g) > gray (1.8 × 10 ± 2.4 × 10 spins g). In contrast, the relative amounts of reduced Mn ions increased with increased combustion completeness. Thus, WUI fire ash is an important global source of EPFRs and reduced metal species (e.g., Mn). Further research is needed to underpin the formation, transformation, and environmental and human health impacts of these paramagnetic species in light of the projected increased frequency, size, and severity of WUI fires.
荒地-城市交界火（WUI）燃烧消耗燃料，如植被和结构材料，留下主要由热成因碳和金属氧化物组成的灰烬。然而，目前对于不同来源的 WUI 火灾灰烬作为环境持久性自由基（EPFRs）和过渡金属等顺磁物质源的作用知之甚少。电子顺磁共振（EPR）用于检测和量化 53 个火灾灰烬和土壤样本中的顺磁物质，这些样本是在加利福尼亚州 2020 年北复合体火灾和索诺玛-莱克-纳帕单元（LNU）闪电复合体火灾之后收集的。在研究的 WUI 火灾灰烬中检测到高浓度的有机 EPFRs（例如，1.4×10 至 1.9×10 自旋 g），以及其他顺磁物质，如铁和锰氧化物以及 Fe 和 Mn 离子。各种灰烬类型中 EPFRs 的平均浓度按以下顺序降低：植被灰（1.1×10±1.1×10 自旋 g）>结构灰（1.6×10±3.7×10 自旋 g）>车辆灰（6.4×10±8.6×10 自旋 g）>土壤（3.2×10±3.7×10 自旋 g）。EPFRs 的平均浓度随着灰烬颜色所指示的燃烧完全程度的增加而降低；黑色（1.1×10±1.1×10 自旋 g）>白色（2.5×10±4.4×10 自旋 g）>灰色（1.8×10±2.4×10 自旋 g）。相比之下，随着燃烧完全程度的增加，还原 Mn 离子的相对量增加。因此，WUI 火灾灰烬是 EPFRs 和还原金属物质（例如 Mn）的重要全球来源。鉴于 WUI 火灾频率、规模和严重程度预计会增加，需要进一步研究这些顺磁物质的形成、转化以及对环境和人类健康的影响。
