期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 46, 期 20, 页码 11384-11392出版社
AMER CHEMICAL SOC
DOI: 10.1021/es302484r
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资金
- USEPA [R834799]
- Mexico-US Commission for Cultural and Educational Exchange
- Fullbright program
- Air Resources Engineering Center at Georgia Tech
Relative contributions of water- and methanol-soluble compounds and their hydrophobic/hydrophilic subtractions to the ROS (reactive oxygen species)-generating potential of ambient fine aerosols (D-p < 2.5 mu m) are assessed. ROS-generating (or oxidative) potential of the particulate matter (PM) was measured by the dithiothreitol (DTT) assay. Particles were collected on quartz filters (N = 8) at an urban site near central Atlanta during January February 2012 using a PM2.5 high-volume sampler. Filter punches were extracted separately in both water and methanol. Hydrophobic and hydrophilic fractions were then subsequently segregated via a C-18 solid phase extraction column. The DTT assay response was significantly higher for the methanol extract, and for both extracts a substantial fraction of PM oxidative potential was associated with the hydrophobic compounds as evident from a substantial attenuation in DTT response after passing PM extracts through the C-18 column (6496 for water and 83% for methanol extract; both median values). The DTT activities of water and methanol extracts were correlated with the water-soluble (R = 0.86) and water-insoluble organic carbon (R = 0.94) contents of the PM, respectively. Brown carbon (BrC), which predominantly represents the hydrophobic organic fraction (referred to as humic-like substances, HULIS), was also correlated with DTT activity in both the water (R = 0.78) and methanol extracts (R = 0.83). Oxidative potential was not correlated with any metals measured in the extracts. These findings suggest that the hydrophobic components of both water-soluble and insoluble organic aerosols substantially contribute to the oxidative properties of ambient PM. Further investigation of these hydrophobic organic compounds could help identify sources of a significant fraction of ambient aerosol toxicity.
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