Search

Taiwan experiences higher air pollution in winter when fine particulate matter (PM 2.5) levels frequently surpass national standards. This study employs the Community Multiscale Air Quality model to assess the effectiveness of reducing SO 2 , NO x , and NH 3 emissions on PM 2.5 secondary inorganic species (i.e., SO 42- , NO 3- , and NH 4+). For sulfate, ∼ 43.7 % is derived from the chemical reactions of local SO 2 emission, emphasizing the substantial contribution of regionally transported sulfate. In contrast, nitrate and ammonium are predominantly influenced by local NO x and NH 3 emissions. Reducing SO 2 emissions decreases sulfate levels, which in turn leads to more NH 3 remaining in the gas phase, resulting in lower ammonium concentrations. Similarly, reducing NO x emissions lowers HNO 3 formation, impacting nitrate and ammonium concentrations by decreasing the available HNO 3 and leaving more NH 3 in the gas phase. A significant finding is that reducing NH 3 emissions decreases not only ammonium and nitrate but also sulfate by altering cloud droplet pH and SO 2 oxidation processes. While the impact of SO 2 reduction on PM 2.5 is less than that of NO x and NH 3 , it emphasizes the complexity of regional sensitivities. Most of western Taiwan is NO x -sensitive, so reducing NO x emissions has a more substantial impact on lowering PM 2.5 levels. However, given the higher mass emissions of NO x than NH 3 in Taiwan, NH 3 has a more significant consequence in mitigating PM 2.5 per unit mass emission reduction (i.e., 2.43 × 10 -5 and 0.85 × 10 -5 µ g m -3 (t yr -1) -1 ​​​​​​​ for NH 3 and NO x , respectively, under current emission reduction). The cost-effectiveness analysis suggests that NH 3 reduction outperforms SO 2 and NO x reduction (i.e., USD 0.06 billion yr -1 µ g -1 m 3 , USD 0.1 billion yr -1 µ g -1 m 3 , and USD 1 billion yr -1 µ g -1 m 3 for NH 3 , SO 2 , and NO x , respectively, under the current emission reduction). Nevertheless, the costs of emission reduction vary due to differences in methodology and regional emission sources. Overall, this study considers both the efficiency and costs, highlighting NH 3 emissions reduction as a promising strategy for PM 2.5 mitigation in the studied environment in Taiwan. [ABSTRACT FROM AUTHOR]

To measure the long-range transport of PCDD/Fs, a background sampling site at Mt. Lulin station (Taiwan) was selected based on meteorological information and its location relative to burning events in Southeast Asia. During regular sampling periods, a higher concentration of PCDD/Fs was recorded in 2008 at Mt. Lulin station during La Niña events, with levels reaching 390 fg I-TEQ/m3. In contrast, a higher concentration of 483 fg I-TEQ/m3 was observed in 2013 during biomass burning events. This indicates that La Niña affects the ambient PCDD/F concentrations. The ratio of ΣPCDD/ΣPCDF was 0.59, suggesting significant long-range transport contributions from 2007 to 2023. From 2007 to 2015, the predominant species was 2,3,4,7,8-PCDF, accounting for 25.3 to 39.6% of the total PCDD/Fs. From 2018 onward, 1,2,3,7,8-PCDD became more dominant, accounting for 15.0 to 27.1%. According to the results from the receptor model PMF (n = 150), the sources of PCDD/Fs were identified as dust storms and monsoon events (19.3%), anthropogenic activity (28.5%), and biomass burning events (52.2%). The PSCF values higher than 0.7 highlighted potential PCDD/F emission source regions for Mt. Lulin during biomass burning events, indicating high PSCF values in southern Thailand, Cambodia, and southern Vietnam. [ABSTRACT FROM AUTHOR]

COVID-19 has been a significant global concern due to its contagious nature. In May 2021, Taiwan experienced a severe outbreak, leading the government to enforce strict Pandemic Alert Level 3 restrictions in order to curtail its spread. Although previous studies in Taiwan have examined the effects of these measures on air quality, further research is required to compare different time periods and assess the health implications of reducing particulate matter during the Level 3 lockdown. Herein, we analyzed the mass concentrations, chemical compositions, seasonal variations, sources, and potential health risks of PM1.0 and PM2.5 in Central Taiwan before and during the Level 3 lockdown. As a result, coal-fired boilers (47%) and traffic emissions (53%) were identified as the predominant sources of polycyclic aromatic hydrocarbons (PAHs) in PM1.0, while in PM2.5, the dominant sources of PAHs were coal-fired boilers (28%), traffic emissions (50%), and iron and steel sinter plants (22.1%). Before the pandemic, a greater value of 20.9 ± 6.92 μg/m3 was observed for PM2.5, which decreased to 15.3 ± 2.51 μg/m3 during the pandemic due to a reduction in industrial and anthropogenic emissions. Additionally, prior to the pandemic, PM1.0 had a contribution rate of 79% to PM2.5, which changed to 89% during the pandemic. Similarly, BaPeq values in PM2.5 exhibited a comparable trend, with PM1.0 contributing 86% and 65% respectively. In both periods, the OC/EC ratios for PM1.0 and PM2.5 were above 2, due to secondary organic compounds. The incremental lifetime cancer risk (ILCR) of PAHs in PM2.5 decreased by 4.03 × 10-5 during the pandemic, with PM1.0 contributing 73% due to reduced anthropogenic activities. [ABSTRACT FROM AUTHOR]

Taiwan experiences higher air pollution in winter when particulate matter (PM2.5) levels frequently surpass national standards. This study employs the Community Multiscale Air Quality model to assess the effectiveness of reducing NH3, NOx, and SO2 emissions on PM2.5 secondary inorganic species (i.e., SO42-, NO3-, and NH4+). For sulfate, ~ 43.7% is derived from the chemical reactions of local SO2 emission, emphasizing the substantial contribution of regional transported sulfate. In contrast, local NOx and NH3 emissions predominantly influence nitrate and ammonium. Reducing SO2 emissions decreases sulfate, thereby influencing NH3 partitioning and resulting in a decreased ammonium. Similarly, reducing NOx emissions lowers HNO3, impacting nitrate and ammonium concentrations due to changes in HNO3 and NH3 partitioning. A particularly significant finding is that NH3 emissions reduction decreases not only nitrate and ammonium but also sulfate by altering cloud droplet pH and SO2 oxidation processes. While SO2 reduction's PM2.5 impact is less than NOx and NH3, it emphasizes the complexity of regional sensitivities. Most of western Taiwan is NOx-sensitive, so reducing NOx emissions has a more substantial impact on lowering PM2.5. However, given the higher mass emissions of NOx than NH3 in Taiwan, NH3 has a more significant consequence in mitigating PM2.5 per unit mass emission reduction. The cost-effectiveness analysis suggests that NH3 reduction outperforms SO2 and NOx. Nevertheless, cost estimates vary due to methodological differences and regional emission sources. Overall, this study considers both efficiency and costs, highlighting NH3 emissions reduction as a promising strategy for PM2.5 mitigation in the studied Taiwan's environment. [ABSTRACT FROM AUTHOR]