Connecting the Oxidative Potential of Fractionated Particulate Matter With Chromophoric Substances
Na Wu, Bingqing Lu, Qingcai Chen, Jianmin Chen, Xiang Li
Abstract
Abstract Particulate matter (PM) air pollution is recognized as a major cause of adverse health outcomes, yet much remains unknown about which fractions and compositions are the most harmful. Efforts in this direction can be improved by employing a cell‐free approach, dithiothreitol (DTT) assay, the so‐called oxidative potential (OP). Here, we provide a detailed examination of OP from fractionated PM by a combination extraction method of solvent and solid‐phase extractions (SPE). We estimate that the average OP of water‐soluble matter (WSM; 4.27 nmol/min/m 3 ) is up to 1.2 times higher than methanol‐soluble matter (3.66 nmol/min/m 3 ) in most seasons apart from summer. Of these WSM, OP is distributed almost equally between hydrophobic and hydrophilic fractions. OP of PM is mainly related to transition metals (Cu: 12.1%, Mn: 2.5%); apart from these, more than 80% of the total OP remains unidentified. Identification of this unexplained OP by a novel approach, integrating the chromophore characteristics with parallel factor analysis, has shown that chromophore1 (C1) accounted for 98% of OP, although this factor only made a small contribution to the total fluorescence. Our paper highlights the importance of a holistic approach by evaluating the chemical structure‐activity relationship between optical characteristics and OP. Information presented here draws a connection between light‐absorbing organic aerosols and a possible toxicological mechanism on the basis of their optical properties.