The Relative Contributions of Different Chemical Components to the Oxidative Potential of Ambient Fine Particles in Nanjing Area.

Ambient fine particles (PM) have been shown to have adverse health effects by inducing oxidative stress. Here, dithiothreitol (DTT)-based oxidative potential (OP) was used to assess the capacity of oxidative stress caused by PM. In this study, PM samples were collected in the Nanjing area in 2016, and physicochemical properties and DTT activity were investigated. The annual mean PM mass concentration was 73 μg m and greatly varied among seasons (spring > winter > summer > autumn). Three fluorescent substances were identified by the excitation-emission matrix (EEM) spectrum. The annual mean mass-normalized DTT activity (DTT; 0.02 nmol min μg) was similar to that documented for cities of some developed countries. The annual mean volume-normalized DTT activity (DTT) showed a relatively high value of 1.16 nmol min m, and the seasonal mean DTT was highest in winter, followed by spring, autumn, and summer, whose pattern is different from PM mass concentration. Correlation and multiple linear regression analysis suggested that transition metals may have a greater effect on OP in autumn and winter, humic-like substances and UV absorbing aromatic substances may have a strong effect on OP in spring and summer. Generally, this study enhances our understanding of seasonal variation in health effects associated with PM.