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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]

Abstract Sediment samples were collected from a large reservoir and a river in northern Taiwan to investigate the occurrence and characteristics of Σ73PCNs analyzed. Results indicate that total concentrations of PCNs (Di- to Octa-CNs) measured in sediments collected in reservoir (29.2 ± 7.11 pg/g-dw) are significantly lower than that of samples collected in river (987 ± 440 pg/g-dw). The increasing trend of PCN concentration from upstream to downstream is found for the sediments collected in reservoir. PCN concentrations measured in surface sediments are relatively higher than that measured in sub-surface sediments collected in reservoir. Tetra-CNs consistently dominate in reservoir sediments, however, Penta-, Tetra- and Mono-CNs dominate in sediments collected at different sampling sites of the river investigated, suggesting that various sources contribute to PCNs collected from river. Indeed, diagnostic ratios indicate that mix-source contribute to PCNs measured in sediments collected from the reservoir and river in northern Taiwan. Highlights • Higher PCNs level is found in sediment of river compared with that of reservoir. • Higher PCN level is measured in surface sediment compared with subsurface sediment. • PCN levels in sediments collected in reservoir increase from upstream to downstream. • Mix-source contributes to PCNs in sediments collected from both reservoir and river. [ABSTRACT FROM AUTHOR]

The influence of long-range transport (LRT) of air pollutants on neighboring regions and countries has been documented. The magnitude of LRT aerosols and related constituents can misdirect control strategies for local air quality management. In this study, we aimed to quantify PM 2.5 (diameter less than 2.5 μm, PM 2.5) and associated metals derived from local sources and LRT in different geographic locations in Taiwan using advanced receptor models. We collected daily PM 2.5 samples (n = ∼1000) and analyzed 28 metals every three days from 2016 to 2018 in the northern, central-south, eastern, and southern areas of Taiwan. We first used a machine learning technique with a cluster algorithm coupled with a backward trajectory to classify local, regional, and LRT-related aerosols. We then quantified the source contributions with a positive matrix factorization (PMF) model for Taiwan weighted by region-specific populations. The northern and eastern regions were found to be more vulnerable to LRT-related PM 2.5 and metals than the central-south and southern regions in Taiwan. The LRT increased Pb and As concentrations by 90–200% and ∼40% in the northern and central-south regions. Ambient PM 2.5 -metals mainly originated from local traffic-related emissions in the northern, central-south, and southern regions, whereas oil combustion was the primary source of PM 2.5 -metals in the eastern region. By subtracting the influence from the LRT, the contributions of domestic emission sources to ambient PM 2.5 metals in Taiwan were 35% from traffic-related emission, 17% from non-ferrous metallurgy, 13% from iron ore and steel factories, 12% from coal combustion, 12% from oil combustion, 10% from incinerator emissions, and <1% from cement manufacturing emissions. This study proposed an advanced method for refining local source contributions to ambient PM 2.5 metals in Taiwan, which provides useful information on regional control strategies. [Display omitted] • To quantify PM 2.5 -metals derived from domestic sources in different geographic locations. • A machine learning technique with a cluster algorithm coupled with a backward trajectory was used. • LRT aerosols remarkably increased PM 2.5 in Taipei and Hualien. • The LRT increased Pb and As by 90–200% in the northern regions. • Traffic-related emissions were the most important sources of PM 2.5 -metals in Taiwan. [ABSTRACT FROM AUTHOR]

Highlights: [•] Winter monsoon not only brings cold air but also transports air pollutants to Taiwan. [•] Biomass burnings are important dioxin emission sources in Southeast Asia. [•] Typhoon events have a documented impact on the remobilization of dioxins. [Copyright &y& Elsevier]

Recently, the high PCDD/F emissions observed in the coastal provinces of eastern China have raised global concerns over their adverse effects on human health. To address the effects of the long-range transport of persistent organic pollutants, the observations of atmospheric PCDD/F pollution were conducted across Southeast Asian in this study. Atmospheric PCDD/F levels were evaluated at two background stations (Sites A and B) in Taiwan, three remote islands (Sites C, D and E) around Taiwan and at Dongsha Island (Site F) in South China Sea at various times. Significantly lower atmospheric PCDD/F concentrations (1.24–7.75 fg I-TEQ m−3) and PCDD/F contents (3.45–49.1 pg I-TEQ/g-TSP) in total suspended particles (TSPs) were measured during the summer season. Based on a 72-h backward trajectory analysis conducted for the sampling sites used in this study, the air mass containing theses low levels had originated from the Pacific Ocean and South China Sea during the summer. The highest PCDD/F concentrations (10.2–65.2 fg I-TEQ m−3) and PCDD/F contents (132–620 pg I-TEQ/g-TSP) in ambient air were measured in northern Taiwan (Site A) and at two islands (Site C and Site E) close to mainland China during the northeast monsoon periods. In the meantime, the PCDF compounds in ambient air also increased from 52–54% to 65–75% at those sampling sites. Based on these measurements and corresponding trajectory analysis, we conclude that the significant increase in atmospheric PCDD/Fs measured during the northeast monsoon period in this study was attributable to the long-range transport of emissions from the coastal regions of mainland China. [ABSTRACT FROM AUTHOR]

Abstract: Sun Moon Lake (SML) is located at 23°52′N, 120°55′E near the center of Taiwan Island. In 2009, deposition of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) in ambient air, water bodies and sediments were measured in SML in this study. The monthly atmospheric PCDD/F deposition ranged from 0.61 to 3.0pg I-TEQm−2 d−1 in the vicinity area of SML. Average PCDD/F concentrations (0.008–0.012pg I-TEQ L−1) in the surface water were uniform and sufficiently mixed at the center, outflow and south bay of SML. However, the PCDD/F content (2.42±0.5ng I-TEQ kg−1 d.w.) of surface sediments measured at the south bay of SML was significantly higher than the PCDD/F content at other sampling sites. To evaluate the anthropogenic pollution history in central Taiwan, PCDD/F concentrations were also analyzed at 1–2cm intervals in three dated sediment cores collected at different locations of SML. The year dating by the sediment cores at different depths was estimated from the sedimentation rate (0.47±0.13–1.35±0.22cmy−1) calculated by 210Pb and 137Cs analysis. Based on the results of isotope analysis of sediment cores collected from the center, outflow and south bay of SML, PCDD/F concentrations at different locations appeared to be quite similar. PCDD/F concentrations in sediment cores began to increase in 1964 and reached a peak (4.78ng I-TEQ kg−1 d.w.) in 1968. In addition, variation in PCDD/F content at different depth of the sediment cores appeared to correlate directly with the rate of organochlorine pesticides production in Taiwan. [Copyright &y& Elsevier]

Abstract: In this study, polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations and depositions in ambient air, water column and sediment were measured at a coupled reservoir-watershed system in northern Taiwan. The atmospheric PCDD/F concentration measured in the vicinity of the reservoir ranged from 4.9 to 39fgI-TEQm−3 and the Asian dust storm in February accounted for the peak value, which corresponded to a total suspended particle concentration of 128μgm−3. The atmospheric PCDD/F deposition ranged from 1.4 to 19pg I-TEQm−2 d−1, with higher deposition occurring during winter and spring (long-range transport events). During summer, when atmospheric deposition is lower, consecutive tropical cyclones (typhoons) bring heavy rainfall that enhances soil erosion and creates turbidity-driven intermediate flow. This results in significantly higher PCDD/F deposition in water column of the reservoir at 70m water depth (179pg I-TEQ m−2 d−1) than at 20m (21pg I-TEQm−2 d−1) during typhoon event. The accumulation rate of PCDD/Fs (9.1ngI-TEQm−2 y−1) in the reservoir sediments (depth: 0–2cm) was consistent with PCDD/F deposition obtained from water column (6.1 and 8.3ngI-TEQm−2 y−1); however, it is significantly higher when compared to the atmospheric deposition (2.0ng I-TEQm−2 y−1). Based on the mass balance between the measurements of atmospheric deposition and sinking particles in water column, around 54–74% of PCDD/F inputs into the reservoir were contributed by the catchment erosion during normal period. However, the PCDD/F input contributed by the enhanced catchment erosion significantly increased to 90% during intensive typhoon events. [Copyright &y& Elsevier]

Abstract: Most polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere are bound to particles which are suspended in the atmosphere, and eventually settle on soil, vegetation, water bodies or other receptors in the environment. Monitoring atmospheric deposition fluxes (dry/wet) is important in tracing the environmental fate and behavior of PCDD/Fs. PCDD/F depositions were collected via an automated PCDD/F ambient sampler and traditional cylindrical vessels, respectively, from April 2007 to February 2008. The automated PCDD/F ambient sampler used in this study can prevent both re-suspension and photo degradation of the PCDD/Fs collected and effectively separates the PCDD/F samples into dry and wet contributions. The results indicated that the ambient PCDD/F concentrations collected using the PS-1 sampler ranged from 0.02pg I-TEQ/m3 to 0.16pg I-TEQ/m3 in Northern Taiwan. The results also indicated that the PCDD/F deposition flux collected using the automated PCDD/F sampler (17.5pg I-TEQ/m2 d to 25.8pg I-TEQ/m2 d) was significantly higher than that sampled with the cylindrical vessels (2.0pg I-TEQ/m2 d to 9.9pg I-TEQ/m2 d). The difference was attributed to the fact that part of the PCDD/F depositions collected using the traditional cylindrical vessels had undergone photo degradation and evaporation. In addition, the wet deposition flux of PCDD/Fs (39.4pg I-TEQ/m2 rainy day to 228pg I-TEQ/m2 rainy day) observed in this study was significantly higher than the dry deposition flux (12.3pg I-TEQ/m2 sunny day to 16.7pg I-TEQ/m2 sunny day). These results demonstrated that wet deposition is the major PCDD/F removal mechanism in the atmosphere. [Copyright &y& Elsevier]

Polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) and heavy metal concentrations were analyzed at 1–2cm intervals in a sediment core collected from a reservoir to evaluate anthropogenic pollution history in central Taiwan. The age of the sediment core was estimated from the sedimentation rate (0.44–0.52cmyear−1, calculated by 210Pb and 137Cs analysis). The highest PCDD/F (4.10ng TEQWHO kg−1 d.w.) and PCB (0.345ngTEQWHO kg−1 d.w.) concentrations occurred around 1985 (i.e. at a downcore depth of 10–12cm). Our results also demonstrated that PCDD/F and PCB concentrations in the reservoir sediment core started to decrease at a depth of 8–10cm (estimated year: 1989). This may be attributed to the fact that the Taiwan Environmental Protection Administration (EPA) proposed the regulation of pentachlorophenol (PCP) production and PCB manufacture in 1983 and 1988, respectively. In addition, a linear increasing trend in metal content with time (towards the core top) was observed for several metals (Zn, Cr, Cu, Cd and Pb). Results of the enrichments rates of anthropogenic metals indicated that the metal/alumina (M/Al) ratios of Zn, Cd and Pb in sediment cores exceeded those in crust compositions by 47%, 59% and 78%, respectively. The results revealed that considerable amounts of heavy metals were carried into the reservoir following significant immigration during the Chinese civil war (1950). [Copyright &y& Elsevier]

In spring 2006, an Asian dust storm (ADS) that originated in the deserts of Mongolia and China eventually reached populated areas of East Asia, including Taiwan. The concentrations of total suspended particles (TSP), vapor/solid-phase dioxin-like compounds and metal content in atmospheric aerosols were monitored at two sampling sites in northern Taiwan during the ADS episode: one along the northern coast (Site A), and the other in Taipei city (Site B). The ADS swept across northern Taiwan from 13 March to 19 March, 2006. Data indicate that the atmospheric dibenzo-p-dioxin and dibenzofuran (PCDD/F, 32.2 to 52.5 fg-I-TEQ/m3) and polychlorinated biphenyl (PCB, 2.23 to 4.49 fg-TEQWHO/m3) concentrations measured at the two sampling sites prior to the ADS episode were considerably lower than those measured in other Asian countries. However, measurements made at both sites on 13 and 18 March 2006 indicate that the atmospheric PCDD/F and PCB concentrations increased 2.5 and 3.2 times at Site A, and 2.1 and 1.9 times at Site B, respectively, during the ADS episode. The concentrations of aluminum (Al), potassium (K) and Titanium (Ti) in atmospheric aerosols were also found to increase about 2 to 5 times during this period. As no specific dioxin emission sources exist within nearly 20 km of Site A, the increase in PCDD/F and PCB concentrations observed there is likely to be related to the ADS from mainland China. Additionally, the amount of PCDD/Fs bound to suspended particles increased from 257–259 to 339–512 pg-I-TEQ/g-TSP during the ADS episode. The distribution of OCDD congener observed in Taipei city increased dramatically during the ADS episode, however, the distribution of PCB congener did not vary significantly. [Copyright &y& Elsevier]

Polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF) and polychlorinated biphenyl (PCB) concentrations were analyzed at 1–2cm intervals in a sediment core collected from a reservoir in Northern Taiwan to evaluate the organic pollution history. The highest PCDD/F (14.4ng TEQ/kg d.w.) and PCB (0.261ng TEQWHO/kg d.w.) concentrations were determined at 13–15cm (estimated year: 1992). The ages of the levels of sediment core were estimated from the sedimentation rate. Analysis results demonstrate that the PCDD/F concentration of the sediment core measured in the reservoir reached their peak when the municipal waste incinerators (MWIs) in the area started to operate. Furthermore, the decrease in sediment core PCDD/F concentration is related to the time of enforcement of the PCDD/F emission limit set by the Environmental Protection Administration (EPA) in Taiwan. Significant distribution of OCDD in homologue profiles was noted in archived soil samples in Taiwan in which the major input of PCDD/Fs was thought to be atmospheric. Major PCB congeners found in the sediment core were the major components of the commercial PCB products. Input fluxes of PCDD/Fs (5.75–158ng-I-TEQ/m2-yr) and PCBs (0.248–3.71ng TEQWHO/m2 yr) into the reservoir of interest are also calculated from the concentration and sedimentation rate of the sediment. The results reveal that considerable amounts of PCDD/Fs and PCBs were carried into the reservoir of interest in the flood stage but not during normal stage. [Copyright &y& Elsevier]

Abstract: Partitioning of PCDD/F (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran) congeners between gaseous and particulate phases and removal efficiencies of the existing air pollution control devices (APCDs) for PCDD/Fs at two large-scale municipal waste incinerators (MWIs) in Taiwan are evaluated via stack sampling and analysis. Two MWIs investigated are equipped with activated carbon injection (ACI) and selective catalytic reduction system (SCR) as major PCDD/F control devices, respectively. The average PCDD/F concentrations of stack gases are 2.35 and 1.49 ng/N m3, and the international toxic equivalent quantity (TEQ) are 0.17 and 0.043 ng TEQ/N m3 in MWI-A and MWI-B, respectively. The average removal efficiency of PCDD/Fs achieved with ACI+BF (bag filters) reaches 95% (MWI-A) while that achieved with the WS (wet scrubber)+SCR system reaches 99% (MWI-B). The results obtained on gas/particulate partitioning in flue gases indicate that particulate-phase PCDD/Fs accounted for 27.7% and 24.7% of the total PCDD/F concentrations at the outlets of cyclone (CY) and electrostatic precipitator (EP) for MWI-A and MWI-B, respectively. But the gas/particulate partitioning in flue gas after PCDD/Fs control devices is quite different in two MWIs. This study also indicates that total 2,3,7,8-substituted PCDD/F discharges are 142.3 μg TEQ/ton waste for MWI-A and 98.6 μg TEQ/ton waste for MWI-B, respectively. [Copyright &y& Elsevier]

The levels and characteristics of atmospheric metals vary in time and location, can result in various health impacts, which increases the challenge of air quality management. We aimed to investigate PM 2.5 -bound metals in multiple locations and propose a methodology for comparing metal elements across study regions and prioritizing source contributions through integrated health risk assessments. PM 2.5 -bound metals were collected in the urban, suburban, rural, and industrial regions of Taiwan between 2016 and 2018. We incorporated the positive matrix factorization (PMF) with health risk assessments (considering estimates of the margin of exposure (MOE) and excess cancer risk (ECR)) to prioritize sources for control. We found that the concentrations of Fe, Zn, V, Cu, and Mn (industry-related metals) were higher at the industrial site (Kaohsiung) and Ba, Cr, Ni, Mo, and Co (traffic-related metals) were higher at the urban site (Taipei). The rural site (Hualian) had good air quality, with low PM 2.5 and metal concentrations. Most metal concentrations were higher during the cold season for all study sites, except for the rural. Ambient concentrations of Mn, Cr, and Pb obtained from all study sites presents a higher health risk of concern. In Kaohsiung, south Taiwan, PM 2.5 -bound metals from the iron ore and steel factory is suggested as the first target for control based on the calculated health risks (MOE < 1 and ECR > 10−6). Overall, we proposed an integrated strategy for initiating the source management prioritization of PM 2.5 -bound metals, which can aid an effort for policymaking. Image 1 • As, Sb, and Pb levels obtained from the suburban site were significantly high. • Ambient Mn, Cr, and Pb concentrations are of concern in all four study areas. • PM 2.5 -bound metals from the iron ore and steel factory are first prioritized to be controlled. [ABSTRACT FROM AUTHOR]

Over the last two decades, Taiwan has effectively diminished atmospheric concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) through the adept utilization of advanced technologies and the implementation of air pollution control devices. Despite this success, there exists a dearth of data regarding the levels of other PM 2.5 -bound organic pollutants and their associated health risks. To address this gap, our study comprehensively investigates the spatial and seasonal variations, potential sources, and health risks of PCDD/Fs, Polychlorinated biphenyls (PCBs), and Polychlorinated naphthalene (PCNs) in Northern and Central Taiwan. Sampling collections were conducted at three specific locations, including six municipal waste incinerators in Northern Taiwan, as well as a traffic and an industrial site in Central Taiwan. As a result, the highest mean values of PM 2.5 (20.3–39.6 μg/m3) were observed at traffic sites, followed by industrial sites (14.4–39.3 μg/m3), and the vicinity of the municipal waste incinerator (12.4–29.4 μg/m3). Additionally, PCDD/Fs and PCBs exhibited discernible seasonal fluctuations, displaying higher concentrations in winter (7.53–11.9 and 0.09–0.12 fg I-TEQ WHO /m3) and spring (7.02–13.7 and 0.11-0.16 fg I-TEQ WHO /m3) compared to summer and autumn. Conversely, PCNs displayed no significant seasonal variations, with peak values observed in winter (0.05–0.10 fg I-TEQ WHO /m3) and spring (0.03–0.08 fg I-TEQ WHO /m3). Utilizing a Positive Matrix Factorization (PMF) model, sintering plants emerged as the predominant contributors to PCDD/Fs, constituting 77.9% of emissions. Woodchip boilers (68.3%) and municipal waste incinerators (21.0%) were identified as primary contributors to PCBs, while municipal waste incinerators (64.6%) along with a secondary copper and a copper sludge smelter (22.1%) were the principal sources of PCNs. Moreover, the study specified that individuals aged 19–70 in Northern Taiwan and those under the age of 12 years in Central Taiwan were found to have a significantly higher cancer risk, with values ranging from 9.26 x 10−9-1.12 x 10−7 and from 2.50 x 10−8-2.08 x 10−7respectively. [Display omitted] • In 20 years, ambient PCDD/Fs levels dropped from 63.8 to 6.99 fg I-TEQ/m3. • The traffic sites recorded the highest mean values of PM 2.5 (20.3–39.6 μg/m3). • No significant variations in PCN levels were found among different seasons. • PCDD/Fs (TEQ) were predominantly in the particle phase in winter than PCBs and PCNs. • PCDD/Fs account (>95%) of the overall risk via inhalation compared to PCBs and PCNs. [ABSTRACT FROM AUTHOR]

PCDD/Fs are among pollutants, which gain major concern from Taiwan government and citizens during industrialization. PCDD/Fs can be emitted into the atmosphere, soil, and water environment in either vapor or solid forms. Atmospheric deposition is the main pathways for atmospheric PCDD/Fs to precipitate on surface soil. In this study, a simultaneous analysis of both soil and deposition PCDD/Fs was done to investigate the relationship between in-soil and deposited PCDD/Fs in Taiwan. Soil samples (n = 84) and atmospheric deposition samples (n = 57) were collected within overlapped periods of time. Geometric mean of 10.4 pg WHO-TEQ/g was found in the soil samples when the geometric mean of atmospheric deposited PCDD/F concentrations was found to be 7.39 pg WHO-TEQ/m 2 /day. Concentration of PCDD/Fs in samples collected in industrial location were higher than those collected in other locations in all sampling areas. OCDD, OCDF, HpCDD, HpCDF, were the predominant congeners in PCDD/F profile in both soil and atmospheric deposited samples, when 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF were major contributors for PCDD/F fingerprint with WHO-TEQ transformation. Positive Matrix Factorization (PMF) analysis showed that 83% of soil PCDD/Fs correlate with atmospheric deposition process originated from industrial activities (44%) and long range transport activities (39%). Furthermore, the PMF analysis found long range transport, municipal solid water incinerators (MSWIs), industrial waste incinerators (IWIs), electric arc furnace, recycling process of aluminum, sintering plants to be the main sources contributing to atmospheric deposited PCDD/Fs. [ABSTRACT FROM AUTHOR]

It is generally established that PCDD/Fs is harmful to human health and therefore extensive field research is necessary. This study is the first to use a novel geospatial-artificial intelligence (Geo-AI) based ensemble mixed spatial model (EMSM) that integrates multiple machine learning algorithms and geographic predictor variables selected using SHapley Additive exPlanations (SHAP) values to predict spatial-temporal fluctuations in PCDD/Fs concentrations across the entire island of Taiwan. Daily PCDD/F I-TEQ levels from 2006 to 2016 were used for model construction, while external data was used for validating model dependability. We utilized Geo-AI, incorporating kriging, five machine learning, and ensemble methods (combinations of the aforementioned five models) to develop EMSMs. The EMSMs were used to estimate long-term spatiotemporal variations in PCDD/F I-TEQ levels, considering in-situ measurements, meteorological factors, geospatial predictors, social and seasonal influences over a 10-year period. The findings demonstrated that the EMSM was superior to all other models, with an increase in explanatory power reaching 87 %. The results of spatial-temporal resolution show that the temporal fluctuation of PCDD/F concentrations can be a result of weather circumstances, while geographical variance can be the result of urbanization and industrialization. These results provide accurate estimates that support pollution control measures and epidemiological studies. [Display omitted] • A novel Geo-AI with 10-year data was used to predict daily PCDD/Fs across Taiwan. • The Shapley Additive exPlanations (SHAP) was used for predictor selection. • The long-term PCDD/Fs variations across Taiwan main island were examined. • The ensemble mixed spatial model can refine air pollution modelling techniques. • The EMSMs demonstrated strong performance (R2 87 %) and robustness in validations. [ABSTRACT FROM AUTHOR]

Eight carbonaceous fractions from aerosols were resolved using the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol (Chow et al., 1993). The aerosols were collected at the Mountain Lulin Atmospheric Background Station (Mt. Lulin, 2862 m a.s.l.) in Central Taiwan from April 2003 to April 2012. The monthly and yearly levels of organic carbon (OC) and elemental carbon (EC) varied consistently with PM2.5 mass concentrations during biomass burning (BB) period. The highest monthly carbonaceous content was observed in March and the highest yearly carbonaceous concentration was observed in 2007. This finding is consistent with the BB activity in Indochina and indicates that carbonaceous content is a major component of BB aerosols. Lee et al. (2011) classified four trajectory groups from the air masses transported to Mt. Lulin during the aerosol collection period. For the air masses transported from the BB area (the BB group) in Indochina, the carbonaceous content was greater than the water-soluble ions in PM2.5, and the OC/EC ratio (4.8 ± 1.5) was high. With EC as the indicator of primary emission sources, the air masses of the BB group were found to contain more primary than secondary OC. The Anthropogenic group (from the local and free troposphere below the 700-hPa pressure level over the Asian continent) probably contained more secondary than primary OC or the sources of OC and EC could be quite diverse. The average char-EC/soot-EC (low-temperature EC/high-temperature EC) ratios were 3.9 ± 3.5, 0.4 ± 0.4, 0.9 ± 0.8, and 0.3 ± 0.4 for the trajectory groups BB, SNBB (from BB source areas during the non-BB period), Anthropogenic, and FT (from the oceanic area and the free troposphere above the 700-hPa pressure level over the Asian continent), respectively. The presence of a high char-EC/soot-EC ratio confirmed the correct classification of the BB group, whereas the low ratios from the other groups indicated the strong influence of vehicle exhaust. It is noted that higher OC and EC levels were obtained at Mt. Lulin as compared with those obtained at other high-elevation sites. This difference suggested that the Indochina BB plume exhibited a more serious climatic impact on the background air in East Asia than in other places in Asia and Europe. On the basis of the carbonaceous levels of the SNBB and FT groups, the background OC and EC levels of approximately 3000 m in the West Pacific are around 1.33 μg m−3 and 0.35 μg m−3, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Distribution of PCDD/F (polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran) congeners at two electric arc furnaces (EAFs) in Taiwan is evaluated via intensive stack sampling and analysis. Two kinds of exhaust system in EAFs including stack system and shutter system are selected for measuring dioxin emissions. In addition, dioxin emissions during oxidation and reduction stages at EAF-A were characterized. Results indicate that the PCDD/F concentration of stack gas in EAF-A was 4.39ng/Nm3 while total Toxic Equivalent Quantity (TEQ) concentration was 0.35ng I-TEQ/Nm3. The PCDD/F concentration of stack gas in EAF-B was 2.20ng/Nm3 and the TEQ concentration was 0.14ng I-TEQ/Nm3. 1,2,3,4,6,7,8-HpCDF, OCDD and OCDF are the major contributors of the dioxin concentrations for two EAFs investigated and the percentage of PCDD/F in particulate phase increases as the chlorination level of the PCDD/F congener increases. The results obtained on gas/particulate partitioning of PCDD/Fs in flue gases prior to the APCD in EAFs indicate that more than 90% exists in particulate phase. In EAF-A, the PCDD/F concentration during oxidation stage is slightly higher than that measured during reduction stage, including the sampling points of CO converter outlet, prior to bag filter and stack. Majority of PCDD/Fs emitted from steel-making processes exists in particulate-phase (about 60–70%) at both EAFs investigated. [Copyright &y& Elsevier]

In this study, ambient air samples were taken concurrently in the vicinity area of a large-scale municipal waste incinerator (MWI) and the background area for measuring polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) concentrations from November 1999 through July 2000 in northern Taiwan. The results obtained from eighteen ambient air samples indicate that the mean PCDD/F concentration of seventeen 2,3,7,8-substituted congeners in wintertime (188–348 fg-I-TEQ/m3) is significantly higher than that measured in summertime (56–166 fg-I-TEQ/m3). In addition, the seasonal PCDD/F concentrations are compared with the ambient air quality data including CO, NO2, PM10 and TSP sampled from Taipei area to gain better insights. It indicates that the variation of ambient air PCDD/F concentrations is closely correlated with that of PM10 concentrations. Besides, the results indicate that the I-TEQ concentration of ambient air in sampling site B (directly downwind of the MWI) is of the highest while the sampling site A (upwind of MWI) is of the lowest among all sampling sites. This implies that existing MWI can be a significant emitter of PCDD/Fs in this area. Furthermore, the patterns of the PCDD/F congener distribution at all sampling sites (including the background site in Taoyuan) are quite similar. OCDD concentration is of the highest among seventeen PCDD/F congeners investigated and accounts for about 35% of the total concentration. As for the I-TEQ concentrations, 2,3,4,7,8-PeCDF is the most significant contributor, generally being responsible for 30–45% of the total I-TEQ values depending on the sampling sites and seasons. [Copyright &y& Elsevier]

[Display omitted] • PAHs emitted from coal-fired plants were over 300 BaPeq ng/m3. • PAHs inside the tunnel were 10 times higher than the ambient air of the vicinity. • IDP and BghiP were major congeners in emission sources but different contribution. • ECRs in industrial areas were 3.61 times higher than recommendation. In this research, we simultaneously studied the characteristics of particulate matter-bound PAHs from two industrial coal fire boilers, one highway tunnel, and PAHs from the ambient air of each source. In the stack gas, condensable particulate matter (CPM) was 10–30 times higher than filterable particulate matter (FPM 2.5). The content of PAHs in each mg of PM 2.5 at emission stack (479 ± 284 ng BaPeq/mg) was reduced by 1.7 times at the industrial vicinity (282 ± 264 ng BaPeq/mg). Inside the tunnel, the PAH content was (138 ± 23.8 ng BaPeq/mg). Such value was reduced with the reduction of human activities from urban (40.8 ± 22.3 ng BaPeq/mg) to rural (34.4 ± 23.9 ng BaPeq/mg) and background areas (3.03 ± 1.94 ng BaPeq/mg). Indeno[1,2,3-cd]pyrene and Benzo[g,h,i]perylene were found to be the major contributor of PAHs from the industrial emission (25–30%) and traffic source (60%). Source apportionment in ambient PAHs found fossil fuel burning (for both industry and traffic purposes), incineration, and biomass burning was major contributors of PAHs in the ambient air in Taiwan. Excessive cancer risk in the vicinity of industrial areas and central regions of Taiwan was higher than the EPA standard threshold of 10−4. [ABSTRACT FROM AUTHOR]

Atmospheric polychlorinated-dibenzo-dioxins/dibenzo-furans (PCDD/Fs) remains an important environmental health concern. Although the total emission inventories of PCDD/Fs in Taiwan decreased from 320 to 52.1 g-I-TEQ/year during 2002–2016, the resulting concentrations of atmospheric PCDD/F and distributions in Taiwan are unknown. We, therefore, conducted a comprehensive investigation of spatial and seasonal variations and apportioned potential sources of ambient PCDD/F concentrations in Taiwan-based on 11-year observation data. A total of 1,008 atmospheric PCDD/F samples were collected from 25 air monitoring stations (from seven areas) and 1 background station for 2006–2016. Linear regression was used to model changes in PCDD/F concentrations. Principal component analysis (PCA) and positive matrix factorization (PMF) were used to identify potential contributors. PCDD/F concentrations in the ambient air gradually decreased during the study period, with a median concentration of 28.2 fg I-TEQ/m3 over 11 years. The highest median PCDD/F concentrations were found in the highly industrialized regions of western Taiwan (38.0–43.4 fg I-TEQ/m3). Lower concentrations were found in eastern Taiwan (∼10 fg I-TEQ/m3). Background stations reported the lowest concentrations of PCDD/Fs, with a median concentration of 1.47 fg I-TEQ/m3. Overall, the concentrations of atmospheric PCDD/Fs in Taiwan were higher in winter (13.4–86.7 fg I-TEQ/m3) than in summer (9.65–27.2 fg I-TEQ/m3). The PCA results indicated that PCDD/F profiles varied by both region (industrialized, urbanized, and background areas) and season. The PMF model for the overall data revealed that the major sources of PCDD/Fs were industrial activities (71.2%). However, in less industrialized areas, traffic activities, long-range transport, and open burning were dominant. • Atmospheric PCDD/Fs widely ranged from 0.97 to 255 fg I-TEQ/m3. • Annual median of ambient PCDD/Fs dropped from 43.9 to 18.2 fg I-TEQ/m3 in 11 years. • Highest level of PCDD/Fs were in western Taiwan spatially and in winter seasonally. • PMF showed major sources to be industry (71.2%), LRT (28.6%), and traffic (2.2%). [ABSTRACT FROM AUTHOR]

This study aimed to assess the characteristics of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) from various stationary and mobile emission sources in Taiwan, with a focus on source apportionment and associated health risks. The northern power plant, equipped with bag filters operating at 150 °C, had significantly lower FPM and CPM levels (0.44 and 0.13 mg/m 3 , respectively) compared to the central and southern power plants, which used electrostatic precipitators operating at 250 °C (FPM, 1.45-8.35 mg/m 3 ; CPM, 2.37-3.73 mg/m 3 ). Additionally, emissions from diesel vehicles under both idle and high-speed conditions exhibited higher FPM levels (3.46-4.67 mg/m 3 ) than gasoline vehicles (0.19-0.40 mg/m 3 ). In terms of PAH toxicity, diesel vehicle emissions had significantly higher BaP-TEQ (87.3 ng/m 3 ) and BaP-MEQ (25.9 ng/m 3 ) levels compared to power plants (BaP-TEQ, 5.49 ng/m 3 ; BaP-MEQ, 2.65 ng/m 3 ). The highest ambient concentrations of PM2.5, BaP-TEQ, and BaP-MEQ were recorded at traffic sites, with values of 48 ± 36 µg/m 3 , 0.29 ng/m 3 , and 0.11 ng/m 3 , respectively. Differences in PAH distributions between stationary and mobile sources were influenced by factors such as pollution control technologies, combustion temperatures, and fuel types. Diesel vehicle emissions were dominated by benzo[g,h,i]perylene (BghiP), indeno[1,2,3-cd]pyrene (IND), benzo[a]pyrene (BaP), and benzo[b]fluoranthene (BbF) under idle conditions, while phenanthrene (PA), pyrene (Pyr), and BghiP were prevalent under high-speed conditions. Source apportionment conducted using principal component analysis (PCA) and positive matrix factorization (PMF) identified diesel and gasoline vehicles as the dominant contributors to atmospheric PAHs in Taiwan, accounting for 38% of the total, followed by coal-fired power plants at 35%. The highest lifetime excess cancer risk (ECR) of 2.5 × 10⁻ 5 was observed in traffic-dense areas, emphasizing the public health implications of vehicle emissions. The study adds credibility to the source apportionment findings, and the health risk analysis highlights variations across different regions, including traffic, urban, rural, and background zones., Competing Interests: Declarations. Ethical approval: Not applicable. Consent to participate: All authors contributed to this work. Consent for publication: All authors have approved authorship, read, and consented to publication. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

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 PM 1.0 and PM 2.5 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 PM 1.0 , while in PM 2.5 , 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/m 3 was observed for PM 2.5 , which decreased to 15.3 ± 2.51 μg/m 3 during the pandemic due to a reduction in industrial and anthropogenic emissions. Additionally, prior to the pandemic, PM 1.0 had a contribution rate of 79% to PM 2.5 , which changed to 89% during the pandemic. Similarly, BaPeq values in PM 2.5 exhibited a comparable trend, with PM 1.0 contributing 86% and 65% respectively. In both periods, the OC/EC ratios for PM 1.0 and PM 2.5 were above 2, due to secondary organic compounds. The incremental lifetime cancer risk (ILCR) of PAHs in PM 2.5 decreased by 4.03 × 10 -5 during the pandemic, with PM 1.0 contributing 73% due to reduced anthropogenic activities., (© 2024. The Author(s).)

The influence of long-range transport (LRT) of air pollutants on neighboring regions and countries has been documented. The magnitude of LRT aerosols and related constituents can misdirect control strategies for local air quality management. In this study, we aimed to quantify PM 2.5 (diameter less than 2.5 μm, PM 2.5 ) and associated metals derived from local sources and LRT in different geographic locations in Taiwan using advanced receptor models. We collected daily PM 2.5 samples (n = ∼1000) and analyzed 28 metals every three days from 2016 to 2018 in the northern, central-south, eastern, and southern areas of Taiwan. We first used a machine learning technique with a cluster algorithm coupled with a backward trajectory to classify local, regional, and LRT-related aerosols. We then quantified the source contributions with a positive matrix factorization (PMF) model for Taiwan weighted by region-specific populations. The northern and eastern regions were found to be more vulnerable to LRT-related PM 2.5 and metals than the central-south and southern regions in Taiwan. The LRT increased Pb and As concentrations by 90-200% and ∼40% in the northern and central-south regions. Ambient PM 2.5 -metals mainly originated from local traffic-related emissions in the northern, central-south, and southern regions, whereas oil combustion was the primary source of PM 2.5 -metals in the eastern region. By subtracting the influence from the LRT, the contributions of domestic emission sources to ambient PM 2.5 metals in Taiwan were 35% from traffic-related emission, 17% from non-ferrous metallurgy, 13% from iron ore and steel factories, 12% from coal combustion, 12% from oil combustion, 10% from incinerator emissions, and <1% from cement manufacturing emissions. This study proposed an advanced method for refining local source contributions to ambient PM 2.5 metals in Taiwan, which provides useful information on regional control strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The levels and characteristics of atmospheric metals vary in time and location, can result in various health impacts, which increases the challenge of air quality management. We aimed to investigate PM 2.5 -bound metals in multiple locations and propose a methodology for comparing metal elements across study regions and prioritizing source contributions through integrated health risk assessments. PM 2.5 -bound metals were collected in the urban, suburban, rural, and industrial regions of Taiwan between 2016 and 2018. We incorporated the positive matrix factorization (PMF) with health risk assessments (considering estimates of the margin of exposure (MOE) and excess cancer risk (ECR)) to prioritize sources for control. We found that the concentrations of Fe, Zn, V, Cu, and Mn (industry-related metals) were higher at the industrial site (Kaohsiung) and Ba, Cr, Ni, Mo, and Co (traffic-related metals) were higher at the urban site (Taipei). The rural site (Hualian) had good air quality, with low PM 2.5 and metal concentrations. Most metal concentrations were higher during the cold season for all study sites, except for the rural. Ambient concentrations of Mn, Cr, and Pb obtained from all study sites presents a higher health risk of concern. In Kaohsiung, south Taiwan, PM 2.5 -bound metals from the iron ore and steel factory is suggested as the first target for control based on the calculated health risks (MOE < 1 and ECR > 10 -6 ). Overall, we proposed an integrated strategy for initiating the source management prioritization of PM 2.5 -bound metals, which can aid an effort for policymaking., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study examined the long-term trends in chemical components in PM 2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) samples collected at Lulin Atmospheric Background Station (LABS) located on the summit of Mt. Lulin (2862 m above mean sea level) in Taiwan in the western North Pacific during 2003-2018. High ambient concentrations of PM 2.5 and its chemical components were observed during March and April every year. This enhancement was primarily associated with the long-range transport of biomass burning (BB) smoke emissions from Indochina, as revealed from cluster analysis of backward air mass trajectories. The decreasing trends in ambient concentrations of organic carbon (-0.67% yr -1 ; p = 0.01), elemental carbon (-0.48% yr -1 ; p = 0.18), and non-sea-salt (nss) K + (-0.71% yr -1 ; p = 0.04) during 2003-2018 indicated a declining effect of transported BB aerosol over the western North Pacific. These findings were supported by the decreasing trend in levoglucosan (-0.26% yr -1 ; p = 0.20) during the period affected by the long-range transport of BB aerosol. However, NO 3 - displayed an increasing trend (0.71% yr -1 ; p = 0.003) with considerable enhancement resulting from the air masses transported from the Asian continent. Given that the decreasing trends were for the majority of the chemical components, the columnar aerosol optical depth (AOD) also demonstrated a decreasing trend (-1.04% yr -1 ; p = 0.0001) during 2006-2018. Overall decreasing trends in ambient (carbonaceous aerosol and nss-K + ) as well as columnar (e.g., AOD) aerosol loadings at the LABS may influence the regional climate, which warrants further investigations. This study provides an improved understanding of the long-term trends in PM 2.5 chemical components over the western North Pacific, and the results would be highly useful in model simulations for evaluating the effects of BB transport on an area., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interests regarding financial funding and the content of this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Fine particulate matter (PM 2.5 ) from different sources with different components have different health impact. In this research in Taiwan, composition and cytotoxicity of PM 2.5 from long-range transport event (LRT), traffic activity, and outdoor cooking at night market were studied. The PM 2.5 mass concentrations were 39.0 μg/m 3 during LRT, 42.9 μg/m 3 at traffic area, and 28.3 μg/m 3 at the night market. Traffic area had highest concentrations of PCDD/Fs (46.9 fg I-TEQ/m 3 ) when highest PAH concentrations of 3.57 BaPeq-ng/m 3 were found at night market area. One quarter of PM 2.5 mass at LRT and night market was constituted by water-soluble ion (26.02-28.93%). Road dust (represented by high concentration of Al and Ca) was the main contributor for metal element at traffic station whereas presence of natural salt (Na and Cl elements) was a marker of LRT and cooking activities. Cell viability reduced 9% after exposure to organic extracts of 0.316 μg of PM 2.5 from LRT and night market samples. 150% elevation of ROS production was observed after exposure with organic compound of night market samples at the dose equivalent to 10.0 μg PM 2.5 . Organic extracts from night market induced positive genotoxicity in umu test (at a dose of 20.0 μg PM 2.5 ).