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Long-range transport (LRT) can carry air pollutants to downwind areas. However, studies about the impacts of LRT on bacterial communities are few. This study investigated the influence of Asian dust storms (ADS) and frontal pollution (FP) on bacterial communities in ambient air using next-generation sequencing (NGS) and Terminal Restriction Fragment Length Polymorphism (T-RFLP). Air samples were collected at Cape Fugui (CF) and National Taiwan University (NTU) in northern Taiwan before (or background days), during, and after LRTs from November 2013 to March 2015. The richness, H index, and evenness increased during FPs and then decreased after FPs. During and after ADS and FP, the prevalence of the phylum Proteobacteria decreased, but that of Firmicutes increased. The dominant class of Proteobacteria changed from Alphaproteobacteria on background days to Betaproteobacteria during LRTs. At the genus level, the high abundance of Ralstonia and Bacillus during FP and Clostridium during ADS were detected at both locations. Additionally, Ralstonia was dominant at CF during ADS. In conclusion, FP and ADS both changed the bacterial community. The indicator genus was Clostridium and Ralstonia for ADS as well as Bacillus and Ralstonia for FP. Given the potential health threats posed by the bioaerosols transported, people should avoid outdoor activities during LRTs. [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: Surface ozone (O3) and carbon monoxide (CO) mixing ratios were measured at Mei-Feng (24.05 °N, 120.10 °E, 2269 m above sea level) remote mountain site between March 2009 and September 2010 to investigate the impact of regional pollution on O3 and CO. The results showed that the maximum values of both O3 and CO were found in the springtime. Backward trajectory analysis, combined with MODIS fire spots suggested that the enhanced O3 and CO in springtime could be attributed to biomass burning (BB) activities over Southeast (SE) Asia. Thirteen BB events were identified by backward trajectory analysis, MODIS fires, NCEP weather data sets and CO concentrations. Good correlation between O3 and CO was found during the BB plumes. Using the linear regression, the slope (ΔO3/ΔCO) was calculated to be 0.18 ± 0.08 (mean ± 1σ). This value was in agreement with that of 0.2 observed over the west Pacific region during the TRACE-P campaign, but was higher than those (0.11–0.14) of Canadian and Siberian fires. Moreover, significant enhanced O3 productivity was also found in aged BB plumes and that mixed with urban emissions from SE coastal China. To assess the net influence of SE Asian BB, the air masses from SE Asia and SE China were divided in two groups: those that passed over the fire regions (PF) and those that did not (NP). The result showed that the maximum differences between PF and NP were estimated in March with 8 ppb for O3 and 45 ppb for CO, respectively, accounting for 23% of both CO and O3 levels at Mei-Feng. Although uncertainties existed in the estimations, the significant discrepancies of O3 and CO in the two air groups suggested the air pollutants emitted by SE Asian BB could be transported and influence the air quality over subtropical Taiwan in springtime. [Copyright &y& Elsevier]

Abstract: The impacts of long-range transport of Asian dust and anthropogenic air pollutants to Taiwan are strongly associated with the atmospheric conditions and paths of transport. In this study, we identified 16 significant dust events (daily mean mass concentration ≥ 120 μg m−3) to Taiwan from 2002 to 2008. To investigate transport characteristics associated with long-range transport of Asian dust and anthropogenic air pollutants to Taiwan, significant dust events were further classified into dry (12 cases) and wet (4 cases) types according to atmospheric conditions. We found that the major transport paths for the dry type (DT) dust cases passed through anthropogenic source areas in the low boundary while the major paths for the wet type (WT) dust cases passed over the ocean. After mineral dust, which occupied around 32% of total PM10 mass concentration, anthropogenic ionic pollutants was the second major contributor and occupied 19–22% at three sampling stations in Taiwan for DT cases. In the fine particle, the anthropogenic ionic pollutants contributed from 29 to 36% to PM2.5, making it the major contributor. The two most significant cases, one from the DT and one from the WT cases, were selected to study transport mechanisms with the NAQPMS air quality model. Simulation results also suggest that transport paths and boundary atmospheric conditions play important roles in aerosol compositions. [Copyright &y& Elsevier]

Abstract: Continuous measurements of ozone (O3) and carbon monoxide (CO) were carried out at Mei-Feng (24.05°N, 120.10°E, 2269m above sea level), a remote mountain site in central Taiwan, to investigate the influence of long-range transported air pollution on O3 and CO variations in the subtropical Pacific region. Data collected from March 2009 to September 2010 revealed average mixing ratios of 37±14ppb for O3 and 188±82ppb for CO at this remote site. Diurnal variations for both O3 and CO were observed as well in all seasons. The higher levels for O3 and CO in the afternoon were attributed to transport of boundary layer pollution to the site during daytime upslope flow. Monthly means of both O3 and CO showed maxima in spring and in the continental air masses from Southeast Asia, coastal China, and Korea/Japan. On the contrary, the lower O3 and CO levels found in summer were due to the marine air masses originating from the Philippine Sea and Pacific Ocean. The relationship between O3 and CO was analyzed, using nighttime data to minimize any local influence. The results showed a fairly good correlation between O3 and CO from March to September. The contribution of CO from the Asian outflow reached a maximum in spring (88ppb) and had a minimum in summer (27ppb). The photochemical buildup of O3 resulting from anthropogenic emissions in continental Asia was estimated to be 15ppb in spring, while its production was insignificant, with an average of 4ppb, in summer. A positive correlation between O3 and CO plus high ozone levels in springtime suggested that the enhancements of O3 were likely due to O3 which was photochemically produced over this region. [Copyright &y& Elsevier]

Abstract: Carbon monoxide (CO) mixing ratios were observed from 30 January to 7 April 2008 at Mt. Lulin (23.51°N, 120.92°E, 2862masl) in central Taiwan to investigate characteristics of CO during biomass burning periods. During the sampling campaign, the average mixing ratio of CO was 234±63ppb with higher levels observed in March. The elevated CO in March can, on the basis of backward trajectories and satellite fire spots analyses, possibly be attributed to biomass burning activities in the Asian continent. Significant diurnal variations of CO mixing ratios were observed at the remote site. The higher CO levels in the afternoon were influenced by the transport of boundary layer pollution to the site during daytime upslope flow. Backward trajectory analysis showed that air masses mainly originated from India (ID), the Indochina Peninsula (IP) and South Coastal China (SC), which together accounted for 85% of the total trajectories. Higher mixing ratios of CO were found in the ID, IP, and SC categories, indicating significant impacts of anthropogenic emissions on the Pacific region. Furthermore, the air parcels were divided into two categories, those that passed over the fire regions and those that did not. The result showed that the average difference of CO levels between the two categories was approximately 79ppb, suggesting that Asian biomass burning plays an important role in CO levels at this remote site during the springtime. [Copyright &y& Elsevier]

Abstract: The impact of long-range transport on the air quality of Taiwan was assessed by using measurements at stations of the air quality monitoring network of the Taiwan Environment Protection Administration over the winter monsoon periods of 2000 and 2001. The primary long-range transport process can be clearly identified to be the prevailing northeasterly following the cold front of winter monsoon that originates in the Asian continent. Based on pollutants concentration differences among different meteorological conditions, we estimate that the long-range transport of particulate pollutants contributes to about 30μgm−3 to the PM10 concentrations in northern and eastern Taiwan. A smaller contribution is estimated for the western plain of Taiwan. Contributions of the long-range transport to CO and SO2 are about 230 and 0.5ppb, respectively. The identified, dust events have the highest average inflow concentration (about 71±34μgm−3) of PM10. The dust impacts on PM10 have been estimated to be nearly 100% at windward background stations along the north and northeast coast. In the northern cities of Taiwan, such as Taipei and Hsinchu, the impacts decrease to around 60–80% as local emission increase. Due to geographic blocking, a smaller impact is estimated for the western plain of Taiwan. However, the identified frontal pollution cases have significant impact on CO and SO2, which is more evident than the impact of dust events. In general, impacts of long-range transport on air pollutants at coastal stations are greater than those in urban areas. [Copyright &y& Elsevier]

Long-range transport (LRT) reportedly carries air pollutants and microorganisms to downwind areas. LRT can be of various types, such as dust storm (DS) and frontal pollution (FP); however, studies comparing their effects on bioaerosols are lacking. This study evaluated the effect of LRT on viral and bacterial concentrations in Northern Taiwan. When LRT occurred and possibly affected Taiwan from August 2013 to April 2014, air samples (before, during, and after LRT) were collected in Cape Fugui (CF, Taiwan's northernmost point) and National Taiwan University (NTU). Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) was applied to quantify influenza A virus. qPCR and qPCR coupled with propidium monoazide were, respectively, used to quantify total and viable bacteria. Types and occurrence of LRT were confirmed according to the changing patterns of meteorological factors and air pollution, air mass sources (HYSPLIT model), and satellite images. Two Asian DS and three FP cases were included in this study. Influenza A virus was detected only on days before and during FP occurred on January 3–5, 2014, with concentrations of 0.87 and 10.19 copies/m3, respectively. For bacteria, the increase in concentrations of total and viable cells during Asian DSs (17–19 and 25–29 November 2013) was found at CF only (from 3.13 to 3.40 and from 2.62 to 2.85 log copies/m3, respectively). However, bacterial levels at NTU and CF both increased during FP and lasted for 2 days after FP. In conclusion, LRT increased the levels of influenza A virus and bacteria in the ambient air of Northern Taiwan, particularly at CF. During and 2 days (at least) after LRT, people should avoid outdoor activities, especially in case of FP. Image 1 • Bioaerosols were monitored before, during, and after long-range transport. • Dust storm and frontal pollution cases transported bacteria and influenza A virus. • Both non-viable (dominant) and viable bacteria were transported. • The effect of long-range transport was lasted to at least two days after events. • Factors associated bacterial levels were varied between background and event days. A capsule of no more than two lines that summarizes the main finding: Asian DS and FP both can transport virus and total and viable bacteria to the downwind area, which can last up to at least 2 days after LRT. [ABSTRACT FROM AUTHOR]

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]

A long term assessment of atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) at Mt. Lulin, located in center of Taiwan was carried out from 2008 to 2013 (n = 81) assuming Mt. Lulin to be background area. During monitoring processes, PCDD/F samples collected in the field occasionally reached high concentration. To investigate this situation, simultaneous sample collection was carried out in Southeast Asia countries (i.e., Vietnam and Thailand) and Taiwan in 2013. The average concentration of atmospheric PCDD/Fs in biomass-burning source regions, namely Son La and Doi Ang Khang were 19.8 ± 12.1 fg I-TEQ m −3 (n = 19) and 17.8 ± 12.4 fg I-TEQ m −3 (n = 20), respectively. In the downwind area of Mt. Lulin, the average concentration of PCDD/Fs was found to be 4.64 ± 3.77 fg I-TEQ m −3 (n = 18). PCDD/F concentration in the source region was much higher than that in the downwind region. On March 19, 2013, the atmospheric PCDD/F concentrations increased dramatically from 7.71 to 484 fg I-TEQ m −3 at Mt. Lulin, which many times exceeded that of assumed source region in Southeast Asia. Moreover, mainland Southeast Asia and the southeast coast of China was suspected to be the main contributors of atmospheric PCDD/Fs and biomass markers, such as nonsea-salt K + and NH 4 + , during the spring. WRF-Chem and Potential Source Contribution Function (PSCF) simulations have confirmed this correlation. It can be concluded that atmospheric PCDD/Fs observed at Mt. Lulin during spring mostly derived from the air mass transport not only from Southeast Asia but also the southeast coast of China. [ABSTRACT FROM AUTHOR]