Road dust resuspension is a major source of particulate matter in many urban centers, especially those in which traction materials are applied to roadways in winter. Although many studies have investigated the composition and toxicity of road dust, nothing is currently known regarding its photochemical reactivity. Here, we show for the first time that road dust is photochemically active: in particular, we use a molecular probe technique to show that the illumination of aqueous road dust suspensions leads to the production of singlet oxygen (¹O₂), an important environmental oxidant. In experiments conducted using size-fractionated road dust, we found that the surface area-normalized steady-state ¹O₂ concentration ([¹O₂]_ss) increased with decreasing particle size. We also observed correlations between [¹O₂]_ss and the dissolved organic carbon content and ultraviolet absorbance properties of dust extracts, which suggests the involvement of chromophoric water-soluble organic carbon in the observed photochemistry. Interestingly, [¹O₂]_ss in aqueous road dust extracts was lower than in the corresponding particle-containing samples, which implies that the particle surface itself also participated in ¹O₂ production. This work provides evidence that road dust photochemistry may influence the lifetime of urban pollutants that react via ¹O₂-mediated pathways.

中文翻译：

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城市道路扬尘光化学法生产单线态氧

在许多城市中心，尤其是那些在冬季将牵引材料应用于道路的中心，道路灰尘的悬浮是颗粒物的主要来源。尽管许多研究已经调查了道路扬尘的成分和毒性，但目前尚无关于其光化学反应性的信息。在这里，我们首次展示了道路尘埃具有光化学活性：特别是，我们使用分子探针技术显示了水性道路尘埃悬浮液的照明会导致产生单线态氧（¹ O ₂），这是一种重要的环境氧化剂。在使用细分的道路灰尘进行的实验中，我们发现表面积归一化的稳态¹ O ₂浓度（[ ¹O ₂ ] _ss）随着粒径的减小而增加。我们还观察到[ ¹ O ₂ ] _ss与粉尘提取物的溶解有机碳含量和紫外线吸收特性之间的相关性，这表明发色的水溶性有机碳参与了所观察到的光化学。有趣的是，水性道路扬尘提取物中的[ ¹ O ₂ ] _ss低于相应的含颗粒样品，这意味着颗粒表面本身也参与了¹ O ₂生产。这项工作提供了证据，表明道路扬尘的光化学作用可能会影响通过¹ O ₂介导的途径发生反应的城市污染物的寿命。