Characterization of PM_2.5 and PM₁₀ fugitive dust source profiles in the Athabasca Oil Sands Region

Geological samples were collected from 27 representative locations in the Athabasca Oil Sands Region (AOSR) in Alberta, Canada. These samples were resuspended onto filter substrates for PM_2.5 and PM₁₀ size fractions. Samples were analyzed for 229 chemical species, consisting of elements, ions, carbon, and organic compounds. These chemical species are normalized to gravimetric mass to derive individual source profiles. Individual profiles were grouped into six categories typical of those used in emission inventories: paved road dust, unpaved road dust close to and distant from oil sand operations, overburden soil, tailings sands, and forest soils. Consistent with their geological origin, the major components are minerals, organic and elemental carbon, and ions. The sum of five major elements (i.e., Al, Si, K, Ca, and Fe) and their oxidized forms account for 25–40% and 45–82% of particulate matter (PM) mass, respectively. Si is the most abundant element, averaging 17–18% in the Facility (oil sand operations) and 23–27% in the Forest profiles. Organic carbon is the second most abundant species, averaging 9–11% in the Facility and 5–6% in the Forest profiles. Elemental carbon abundance is 2–3 times higher in Facility than Forest profiles. Sulfate abundance is ~7 times higher in the Facility than in the Forest profiles. The ratios of cation/anion and base cation (sum of Na⁺, Mg²⁺, K⁺, and Ca²⁺)/nitrogen- and sulfur-containing ions (sum of NH₄⁺, NO₂^-, NO₃^-, and SO₄^2-) exceed unity, indicating that the soils are basic. Lead (Pb) isotope ratios of facility soils are similar to the AOSR stack and diesel emissions, while those of forest soils have much lower ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios. High-molecular-weight <i>n</i>-alkanes (C₂₅-C₄₀), hopanes, and steranes are more than an order of magnitude more abundant in Facility than Forest profiles. These differences may be useful for separating anthropogenic from natural sources of fugitive dust at receptors.Implications: <i>Several organic compounds typical of combustion emissions and bitumen are enriched relative to forest soils for fugitive dust sources near oil sands operations, consistent with deposition uptake by biomonitors. AOSR dust samples are alkaline, not acidic, indicating that potential acid deposition is neutralized. Chemical abundances are highly variable within emission inventory categories, implying that more specific subcategories can be defined for inventory speciation.</i>本研究从加拿大阿尔伯塔省阿萨巴斯卡油砂矿区（Athabasca Oil Sands Region, AOSR）的27个代表性点位采集地质样品。将上述样品重悬于滤膜基质，以分离细颗粒物（PM₂.₅）与可吸入颗粒物（PM₁₀）的粒径组分。随后对样品开展229种化学组分的分析，涵盖元素、离子、碳质组分及有机化合物。通过将各化学组分以称重质量归一化，推导得到单个源谱；随后将所有单个源谱归为排放清单中典型的六大类别：铺装道路扬尘、油砂作业周边及远端的非铺装道路扬尘、覆盖层土壤、尾矿砂与森林土壤。 与样品的地质起源一致，其主要组分为矿物、有机碳、元素碳及离子。五种主要元素（Al、Si、K、Ca、Fe）及其氧化形态的总和，分别占颗粒物（Particulate Matter, PM）总质量的25%~40%与45%~82%。硅（Si）是丰度最高的元素：在油砂作业设施源谱中平均占比为17%~18%，在森林土壤源谱中则为23%~27%。有机碳为第二丰富的组分，设施源谱中平均占比9%~11%，森林源谱中为5%~6%。元素碳的丰度在设施源谱中是森林源谱的2~3倍；硫酸盐丰度在设施源谱中约为森林源谱的7倍。 阳离子/阴离子比值，以及碱金属阳离子（Na⁺、Mg²⁺、K⁺、Ca²⁺的总和）与含氮、含硫离子（NH₄⁺、NO₂⁻、NO₃⁻、SO₄²⁻的总和）的比值均大于1，表明该区域土壤呈碱性。 设施土壤的铅（Pb）同位素比值与AOSR的烟囱排放及柴油发动机排放相近；而森林土壤的²⁰⁶Pb/²⁰⁷Pb与²⁰⁸Pb/²⁰⁷Pb比值则显著更低。高分子量正构烷烃（C₂₅~C₄₀）、藿烷及甾烷在设施源谱中的丰度较森林源谱高出一个数量级以上。上述差异可用于区分受体处无组织扬尘的人为来源与自然来源。 研究启示：油砂作业周边无组织扬尘源中，若干典型燃烧排放物及沥青相关有机化合物相较于森林土壤呈现富集特征，这与生物监测器的沉积摄取结果相符。AOSR的扬尘样品呈碱性而非酸性，表明潜在的酸性沉降已被中和。各排放清单类别内的化学组分丰度存在显著差异，这意味着可针对排放清单的组分解析定义更为具体的子类别。