Impacts of the COVID-19 lockdown in China on new particle formation and particle number size distribution in three regional background sites in Asian continental outflow

Despite the curtailment of atmospheric condensing precursor gases during the Coronavirus disease 2019 (COVID-19) lockdown (LD) period, unexpected haze events via the formation of new particles and their subsequent growth have been identified. This study investigated the impact of emission reduction during the Chinese LD period on the new particle formation (NPF) frequency and corresponding particle number size distribution (PNSD) at three regional background atmospheric monitoring sites in the western coastal areas of the Korean Peninsula. During this duration, the number concentrations of the nucleation- (<25 nm) and accumulation-mode (>90 nm) particles significantly decreased in Baengryeong (BRY), showing decreases of 34% and 29%, respectively. Unlike BRY, the PNSD in Anmyeon (AMY), which is influenced by nearby industrial emissions, remained nearly unchanged during the LD period, possibly because the reduction in industrial emissions was not significant during the social distancing period enforced by Korea. Bongseong (BOS) showed a similar variation to that of BRY; however, the magnitude of the reduction was weaker because of its higher altitude compared to other sites. The cyclostationary empirical orthogonal function technique was applied to the measured PNSDs at the three sites to objectively classify NPF events. Because mode 1 of cyclostationary loading vectors commonly represented the typical diurnal variation of PNSD during regional NPF events at three sites, mode 1 of the corresponding principal component time series was used for NPF classification. The NPF frequency decreased by 7%, 1%, and 7% in BRY, AMY, and BOS, respectively, despite favorable meteorological conditions, such as increased temperature and insolation during the LD period. The diurnal variation in the sulfuric acid (H2SO4) proxy implied that the H2SO4 proxy acted as a determining factor for NPF events during the NPF occurrence time (8-12 local hours) in AMY and BOS; however, NPF occurrence in BRY was not connected to the H2SO4 proxy level. This suggests that BRY was more likely to be influenced by the reduction in organic species in the continental upwind regions, while the occurrence of NPF events in AMY and BOS can be suppressed in association with the distinct reduction in inorganic compounds represented by the H2SO4 proxy during the LD period.

Human migration-based graph convolutional network for PM2.5 forecasting in post-COVID-19 pandemic age

Due to the coronavirus disease 2019 pandemic, local authorities always implanted non-pharmaceutical interventions, such as maintaining social distance to reduce human migration. Besides, previous studies have proved that human migration highly influenced air pollution concentration in an area. Therefore, this study aims to explore whether human migration can work as a significant factor in the post-pandemic age to help PM2.5 concentration forecasting. In this work, we first analyze the variations of PM2.5 in 11 cities of Hubei from 2015 to 2020 and further compare PM2.5 trends with the migration trends of Hubei province in 2020. Experimental results indicate that the human migration indirectly affected the urban PM2.5 concentration. Then, we established a graph data structure based on the migration network describing the migration flow size between any two areas in the Hubei province and proposed a migration attentive graph convolutional network (MAGCN) for forecasting PM2.5. Combined with the migration data. The proposed model can attentively aggregate the information of neighbor nodes through migration weights. Experimental results indicate that the proposed MAGCN can forecast PM2.5 concentration accurately.

Different Transport Behaviors between Asian Dust and Polycyclic Aromatic Hydrocarbons in Urban Areas: Monitoring in Fukuoka and Kanazawa, Japan

To clarify different effects of Asian dust (AD), long-range transported from Asian continent, on total suspended particles (TSP) and polycyclic aromatic hydrocarbons (PAHs) in Japan, TSP were simultaneously collected during AD periods (from 1 March to 31 May 2020 and 2021) in Fukuoka and Kanazawa. During AD days, decided by Light Detection and Ranging and Japan Meteorological Agency, TSP concentrations increased significantly (p < 0.001) at two sampling sites. PAH concentrations increased in Kanazawa (p < 0.001) but not in Fukuoka on AD days. Correlation coefficients (r) between daily TSP and total PAHs concentrations were weak in Kanazawa: 0.521 (non-AD) and 0.526 (AD) (p < 0.01), and in Fukuoka: 0.321 (non-AD) and 0.059 (AD). However, correlation between seasonal (average monthly) TSP and total PAH concentrations were stronger: 0.680 (Kanazawa) and 0.751 (Fukuoka). The reasons might be that seasonal variations of TSP and total PAHs in two cities depend equally on planetary scale westerly, while daily TSP and total PAHs variations in each city varied by different transportation distances from AD and PAHs sources in the Asian continent to Japan. Different local sources and meteorological conditions were considered. These results are important for elucidating the causes of chronic and acute respiratory diseases.

PM-Bound Polycyclic Aromatic Hydrocarbons and Nitro-Polycyclic Aromatic Hydrocarbons in the Ambient Air of Vladivostok: Seasonal Variation, Sources, Health Risk Assessment and Long-Term Variability

Total suspended particles (TSP) were collected in Vladivostok, Russia, which is a typical port city. This study investigated the concentration, potential sources, and long-term variation in particle PAHs and NPAHs in the atmosphere of Vladivostok. The PAH and NPAH concentrations were higher in winter than in summer (PAHs: winter: 18.6 ± 9.80 ng/m3 summer: 0.54 ± 0.21 ng/m3; NPAHs: winter: 143 ± 81.5 pg/m3 summer: 143 ± 81.5 pg/m3). The diagnostic ratios showed that PAHs and NPAHs mainly came from vehicle emissions in both seasons, while heating systems were the main source of air pollution in winter. The TEQ assessment values were 2.90 ng/m3 and 0.06 ng/m3 in winter and summer, respectively, suggesting a significant excess cancer risk in the general population in winter. The ILCR values conveyed a potential carcinogenic risk because the value was between 1 × 10-5 and 1 × 10-7 and ingestion was a main contributor in Vladivostok. However, it is worth noting that the concentrations of PAHs and NPAHs showed an overall downward trend from 1999 to 2020. An important reason for this is the cogenerations project implemented by the Far Eastern Center for Strategic Research on Fuel and Energy Complex Development in 2010. This research clarified the latest variations in PAHs and NPAHs to provide continuous observation data for future chemical reaction or model prediction research.

Changes in air quality in-taxis and in working conditions of taxi drivers pre- and post-lockdown, during the COVID-19 pandemic in the Paris area

We evaluated the impact of the lockdown restriction measures in the Paris area on the variation of in-vehicle ultrafine particle (UFP) and black carbon (BC) concentrations between the pre- and post-lockdown period and professional drivers' working conditions and practices. The study was conducted with 33 taxi drivers. UFP and BC were measured inside their vehicles with DiSCmini^® and microAeth^® , respectively, on two typical working days pre- and post-lockdown. Job characteristics were self-reported. Our results showed that post-lockdown, both the number of clients and journey duration significantly decreased. Taxi drivers opened their windows significantly more and reduced the use of air recirculation. UFP decreased significantly by 32% and BC by 31% post-lockdown, with a weaker positive correlation compared to pre-lockdown. The reduction of in-vehicle UFP was due mainly to the reduction of traffic flow and ventilation settings, though the latter probably varied according to traffic conditions. The variation of in-vehicle BC also tended to be related to the decrease in traffic flow post-lockdown. We emphasize the role of traffic emissions on in-vehicle air pollution and that preventive measures such ventilation settings would help to minimize the exposure of professional drivers and passengers to air pollutants.

Polycyclic aromatic hydrocarbons and nitro-polycyclic aromatic hydrocarbons in five East Asian cities: Seasonal characteristics, health risks, and yearly variations

Total suspended particulate matter and fine particulate matter were collected in five East Asian cities (Sapporo, Sagamihara, Kirishima, Shenyang, and Vladivostok) during warm and cold periods from 2017 to 2018. Nine polycyclic aromatic hydrocarbons (PAHs) and three nitro-polycyclic aromatic hydrocarbons (NPAHs) were detected by high-performance liquid chromatography with a fluorescence detector. The average concentrations of ∑PAHs and ∑NPAHs differed significantly both temporally and spatially and were the lowest in Kirishima during the warm period (∑PAHs: 0.11 ± 0.06 ng m^-3; ∑NPAHs: 1.23 ± 0.96 pg m^-3) and the highest in Shenyang during the cold period (∑PAHs: 49.7 ± 21.8 ng m^-3; ∑NPAHs: 357 ± 180 pg m^-3). The average total benzo[a]pyrene-equivalent concentrations were also higher in Shenyang and Vladivostok than in Japanese cities. According to the results of source apportionment, traffic emissions impacted these cities in both the warm and cold periods, whereas coal combustion-generated effects were obvious in Shenyang and Vladivostok during the cold period. Furthermore, PAHs and NPAHs originating from the Asian continent, including Shenyang and Vladivostok, exerted some influence on Japanese cities, especially in the cold period. Compared to Japanese cities and Vladivostok, yearly variations in ∑PAHs and 1-nitropyrene in Shenyang showed that their concentrations were considerably lower than those reported in past studies, indicating the positive effects of air pollutant control policies in China. These results not only describe the current characteristics and yearly variations of PAHs and NPAHs in typical urban cities in East Asia but also, more importantly, reveal that the effects of the East Asian monsoon play an important role in the analysis of atmospheric behaviours of PAHs and NPAHs. Furthermore, this study supports the role of multinational cooperation to promote air pollution control in East Asia.

Improved Detection Sensitivity of an Antigen Test for SARS-CoV-2 Nucleocapsid Proteins with Thio-NAD Cycling

Antigen tests for infectious diseases are inexpensive and easy-to-use, but the limit of detection (LOD) is generally higher than that of PCR tests, which are considered the gold standard. In the present study, we combined a sandwich enzyme-linked immunosorbent assay (ELISA) with thionicotinamide-adenine dinucleotide (thio-NAD) cycling to improve the LOD of antigen tests for coronavirus disease 2019 (COVID-19). For recombinant nucleocapsid proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the LOD of our ELISA with thio-NAD cycling was 2.95 × 10^-17 moles/assay. When UV-irradiated inactive SARS-CoV-2 was used, the minimum detectable virions corresponding to 2.6 × 10⁴ RNA copies/assay were obtained using our ELISA with thio-NAD cycling. The assay volume for each test was 100 µL. The minimum detectable value was smaller than that of the latest antigen test using a fluorescent immunoassay for SARS-CoV-2, indicating the validity of our detection system for COVID-19 diagnosis.

Assessing Approaches of Human Inhalation Exposure to Polycyclic Aromatic Hydrocarbons: A Review

Polycyclic aromatic hydrocarbons (PAHs) are a class of important organic pollutants widely emitted from anthropogenic activities, with a general distribution in the gas and particulate phases. Some PAHs are carcinogenic, teratogenic, and mutagenic. Inhalation exposure to PAHs is correlated with adverse health outcomes in the respiratory and cardiovascular systems. Thus, it is significant to determine the exposure level of the general population. This study summarizes the evaluation methods for PAH exposure, focusing on different exposure parameters. External exposure can be determined via the collection of the environmental pollution concentration through active samplers or passive samplers during environmental monitoring or personal sampling. Time-activity patterns give critical exposure information that captures the exposure period, origin, and behaviors. Modeling is a labor-less approach for human exposure estimation, and microenvironmental exposure requires specific research. It is important to select appropriate methods to quantify the exposure level to provide accurate data to establish the exposure–risk relationship and make scientific suggestions for the protection of public health.

Exposure to Atmospheric Particulate Matter-Bound Polycyclic Aromatic Hydrocarbons and Their Health Effects: A Review

Particulate matter (PM) is a major factor contributing to air quality deterioration that enters the atmosphere as a consequence of various natural and anthropogenic activities. In PM, polycyclic aromatic hydrocarbons (PAHs) represent a class of organic chemicals with at least two aromatic rings that are mainly directly emitted via the incomplete combustion of various organic materials. Numerous toxicological and epidemiological studies have proven adverse links between exposure to particulate matter-bound (PM-bound) PAHs and human health due to their carcinogenicity and mutagenicity. Among human exposure routes, inhalation is the main pathway regarding PM-bound PAHs in the atmosphere. Moreover, the concentrations of PM-bound PAHs differ among people, microenvironments and areas. Hence, understanding the behaviour of PM-bound PAHs in the atmosphere is crucial. However, because current techniques hardly monitor PAHs in real-time, timely feedback on PAHs including the characteristics of their concentration and composition, is not obtained via real-time analysis methods. Therefore, in this review, we summarize personal exposure, and indoor and outdoor PM-bound PAH concentrations for different participants, spaces, and cities worldwide in recent years. The main aims are to clarify the characteristics of PM-bound PAHs under different exposure conditions, in addition to the health effects and assessment methods of PAHs.