Oxidative stress is one of the key mechanisms linking ambient particulate matter (PM) exposure with various adverse health effects. The oxidative potential of PM has been used to characterize the ability of PM induced oxidative stress. Hydroxyl radical (•OH) is the most destructive radical produced by PM. However, there is currently no high-throughput approach which can rapidly measure PM-induced •OH for a large number of samples with an automated system. This study evaluated four existing molecular probes (disodium terephthalate, 3′-p-(aminophenyl)fluorescein, coumarin-3-carboxylic acid, and sodium benzoate) for their applicability to measure •OH induced by PM in a high-throughput cell-free system using fluorescence techniques, based on both our experiments and on an assessment of the physicochemical properties of the probes reported in the literature. Disodium terephthalate (TPT) was the most applicable molecular probe to measure •OH induced by PM, due to its high solubility, high stability of the corresponding fluorescent product (i.e., 2-hydroxyterephthalic acid), high yield compared with the other molecular probes, and stable fluorescence intensity in a wide range of pH environments. TPT was applied in a high-throughput format to measure PM (NIST 1648a)-induced •OH, in phosphate buffered saline. The formed fluorescent product was measured at designated time points up to 2 h. The fluorescent product of TPT had a detection limit of 17.59 nM. The soluble fraction of PM contributed approximately 76.9% of the •OH induced by total PM, and the soluble metal ions of PM contributed 57.4% of the overall •OH formation. This study provides a promising cost-effective high-throughput method to measure •OH induced by PM on a routine basis.

The natural and ecological wastewater treatment system (NEWS) was developed to target organic pollutants and nutrients for decentralized rural communities. The system was installed in Sangwang-dong, Gongju-si, Chungcheongnam-do, South Korea, and operated for about nine months. It consisted of three parts: the anaerobic septic tank, the absorbent-biofilter system (ABS), and the up- and down-flow constructed wetland. The respective nitrogen (N), phosphorus (P), and chemical oxygen demand removal rates of the NEWS were 45.94, 48.65, and 98.47% in the growing season and 27.93, 23.78, and 86.45% in the winter season. The significantly low N and P removal rates could have been caused by microorganism vitality in the ABS, as most of the nutrients occurred in an organic form. Average water temperature of the ABS was 18.13°C in the growing season and 8.289°C in the winter season, which might have influenced the low overall removal rate during the winter season. Performance of the NEWS was efficient, independent of the influent concentration within the study period, except a short term clogging. Considering its high performance, low maintenance, and cost-effectiveness, the NEWS is an effective, feasible alternative for sewage treatment in decentralized communities in South Korea.