Iron speciation in particulate matter (PM2.5) from urban Los Angeles using spectro-microscopy methods
Iron speciation in particulate matter (PM2.5) from urban Los Angeles using spectro-microscopy methods
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DOI：
10.1016/j.atmosenv.2020.117988
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发表时间：
2021-01-15
影响因子：
5
通讯作者：
O'Day, Peggy A.
中科院分区：
文献类型：
--
作者：
Pattammattel, Ajith;Leppert, Valerie J.;O'Day, Peggy A.
采用体相和空间分辨、元素特异性光谱和显微镜相结合的方法研究了洛杉矶两个城市PM2. 5样品中铁相的形态、氧化态和相对丰度。同步加速器X射线吸收光谱（XAS）的散装样品在原位（即，没有提取或消化）被用来量化的主要Fe相的相对分数，这是由空间分辨光谱显微镜测量证实。水铁矿（无定形氢氧化铁（III））包括最大的铁部分（34-52%），与赤铁矿（α-Fe 2 O3; 13-23%）和磁铁矿（Fe 3 O 4; 10-24%）确定为主要的结晶氧化物组分。含铁层状硅酸盐部分（16-23%）与天然伊利石/蒙皂石矿物的参考光谱最匹配，金属Fe（0）相对较小（2-6%），但易于识别。尺寸，形态，氧化态，和微量元素组成的Fe-轴承PM从电子显微镜，电子能量损失谱（EELS），和扫描透射X射线显微镜（STXM）揭示变量和异质混合物的Fe物种和阶段，通常与碳质材料的表面氧化的证据。水铁矿（或相关的Fe（III）氢氧化物相）是无处不在的PM样品。它作为结晶Fe相的氧化或表面改变产物形成，并且还作为作为环境溶解和再沉淀反应的结果与其他相分散的涂层或纳米颗粒出现。在对环境PM的研究中，水铁矿（和吸附的Fe（III））的普遍性可能被低估了，因为它是非结晶的，非磁性的，比结晶相更易溶解，并且存在于复杂的混合物中。审查不同类型的颗粒的潜在来源表明，大多数含铁PM从这些城市网站来自人类活动，主要是磨损产品从车辆制动系统和发动机排放的燃烧和/或磨损。这些可变的混合物对于Fe、氧化还原活性金属（例如铜）和活性碳物质（例如醌）之间的电子转移反应具有高概率。我们的研究结果表明，需要评估生物反应的特定铁轴承阶段单独和组合，以解开机制的不利健康影响的颗粒铁。
The speciation, oxidation states, and relative abundance of iron (Fe) phases in PM2.5 samples from two locations in urban Los Angeles were investigated using a combination of bulk and spatially resolved, element-specific spectroscopy and microscopy methods. Synchrotron X-ray absorption spectroscopy (XAS) of bulk samples in situ (i.e., without extraction or digestion) was used to quantify the relative fractions of major Fe phases, which were corroborated by spatially resolved spectro-microscopy measurements. Ferrihydrite (amorphous Fe(III)hydroxide) comprised the largest Fe fraction (34-52%), with hematite (alpha-Fe2O3; 13-23%) and magnetite (Fe3O4; 10-24%) identified as major crystalline oxide components. An Fe-bearing phyllosilicate fraction (16-23%) was fit best with a reference spectrum of a natural illite/smectite mineral, and metallic Fe(0) was a relatively small (2-6%) but easily identified component. Sizes, morphologies, oxidation state, and trace element compositions of Fe-bearing PM from electron microscopy, electron energy loss spectroscopy (EELS), and scanning transmission X-ray microscopy (STXM) revealed variable and heterogeneous mixtures of Fe species and phases, often associated with carbonaceous material with evidence of surface oxidation. Ferrihydrite (or related Fe(III) hydroxide phases) was ubiquitous in PM samples. It forms as an oxidation or surface alteration product of crystalline Fe phases, and also occurs as coatings or nanoparticles dispersed with other phases as a result of environmental dissolution and re-precipitation reactions. The prevalence of ferrihydrite (and adsorbed Fe(III)) has likely been underestimated in studies of ambient PM because it is non-crystalline, non-magnetic, more soluble than crystalline phases, and found in complex mixtures. Review of potential sources of different particle types suggests that the majority of Fe-bearing PM from these urban sites originates from anthropogenic activities, primarily abrasion products from vehicle braking systems and engine emissions from combustion and/or wear. These variable mixtures have a high probability for electron transfer reactions between Fe, redox-active metals such as copper, and reactive carbon species such as quinones. Our findings suggest the need to assess biological responses of specific Fe-bearing phases both individually and in combination to unravel mechanisms of adverse health effects of particulate Fe.