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Abstract This study investigated isotopic signatures of carbon (C), lead (Pb) and strontium (Sr) in PM 2.5 samples collected from two paired sites (urban vs. rural/background) in northern Taiwan during the summer of 2015 and the spring of 2016, respectively. Significant seasonality was revealed in the isotopic signatures of C and Pb, whereas no seasonal difference was observed in 87Sr/86Sr ratio. The values of δ13C, 206Pb/207Pb, and 208Pb/207Pb were more diverse and exhibited local features in summer. However, during the episodes of continental pollution outbreaks in springtime, the δ13C and Pb isotope ratios of PM 2.5 shifted and converged consistently toward the documented characteristics of particulate matters in northern China. Moreover, the results showed that the differences in the Pb and Sr isotopic characteristics between the paired urban and rural sites were statistically insignificant, whereas marginally lower δ13C values were observed at the urban site. It was inferred accordingly that a substantial amount of gaseous hydrocarbons emitted in local urban areas could have been converted to secondary organic aerosols with lower δ13C. On the contrary, the consistency in the spatial and temporal variations of mass concentration and isotope ratios of Pb at the two sites suggested that East-Asian continental pollution outbreak was the major source of Pb-containing particles in the northern Taiwan during springtime. It is noteworthy that there was neither seasonal nor spatial differences in the 87Sr/86Sr ratio observed in this study, which suggested that the Sr-containing particles collected in this study could be originating from a common mixture of sources, including not only natural dust but also the anthropogenic emissions, coal-combustion for instance. This investigation upon the C-Pb-Sr isotopic features evidenced the substantial impacts of the continental pollution outbreaks on the aerosol composition and air quality in the downwind areas of the East-Asian winter monsoons. Graphical abstract Unlabelled Image Highlights • Seasonal and temporal variations of C-Pb-Sr isotopes of PM 2.5 were investigated. • C and Pb in PM 2.5 exhibited significant seasonal isotope signatures. • Isotopic evidences for the impacts of Asian outflows on air quality were revealed. • Consistent Sr isotope ratios were observed from local and distant sources. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the synoptic weather types that have high probability and low probability of producing PM10 episode are referred to as HPE and LPE, respectively. Multiple linear regressions analysis showed that NO2 was the most important contributor (35.61%) to the concentrations of PM10 for HPE weather. For LPE weather, the season factor had the greatest contribution (48.11%) to the concentrations of PM10. Using the correlation coefficients between the concentrations of PM10 and SO2 or NO2 on HPE and LPE to calculate the increase of PM10 from LPE to HPE, we found that the increase of PM10 owing to the increase of SO2 and NO2 from LPE to HPE was 12.93μg/m3 which was about 51% of the total amount of PM10 increased from LPE to HPE. Results of factor analysis showed that the first component could be attributed to the result of local pollution especially for the weather patterns of types P3 and P6, while the secondary component for the weather patterns of types P1 and P4 can be attributed to the long-range transport of SO2 pollutants from China. [Copyright &y& Elsevier]

Since the 24-hr PM 2.5 (particle aerodynamic diameter less than 2.5 μm) concentration standard was regulated in Taiwan in 2012, the PM 2.5 concentration has been decreasing year by year, but the ozone (O 3 ) concentration remains almost the same. In particular, the daily maximum 8-hr average O 3 (MDA8 O 3 ) concentration frequently exceeds the standard. The goal of this study is to find a solution for reducing PM 2.5 and O 3 simultaneously by numerical modeling. After the Volatile Organic Compounds (VOC S )-limited and nitrogen oxides (NO X )-limited areas were defined in Taiwan, then, in total, 50 scenarios are simulated in this study. In terms of the average in Taiwan, the effect of VOC S emission reduction is better than that of NO X on the decrease in PM 2.5 concentration, when the same reduction proportion (20%, 40%) is implemented. While the effect of further NO X emission reduction (60%) will exceed that of VOC S . The decrease in PM 2.5 is proportional to the reduction in precursor emissions such as NO X , VOC S , sulfur dioxides (SO 2 ), and ammonia (NH 3 ). The lower reduction of NO X emission for whole Taiwan caused O 3 increases on average but higher reduction can ease the increase, which suggests the implement of NO X emission reductions must be cautious. When comparing administrative jurisdictions in terms of grids, districts/towns, and cities/counties, it was found that controlling NO X and VOC S at a finer spatial resolution of control units did not benefit the decrease in PM 2.5 but did benefit the decrease in O 3 . The enhanced O 3 control strategies obviously cause a higher decrease of O 3 throughout Taiwan due to NO X and VOC S emission changes when they are implemented in the right places. Finally, three sets of short-term and long-term goals of controlling PM 2.5 and O 3 simultaneously are drawn from the comprehensive rankings for all simulated scenarios, depending on whether PM 2.5 or O 3 control is more urgent. In principle, the short-term scenarios could be ordinary or enhanced version of O 3 decrease with lower NO X /VOC S emissions, while the long-term scenario is enhanced version of O 3 decrease plus high emission reductions for all precursors., (Copyright © 2022 Elsevier Ltd. All rights reserved.)