Degradation of PAHs during long range transport based on simultaneous measurements at Tuoji Island, China, and at Fukue Island and Cape Hedo, Japan

Nohchi

Maeshima

et al. 2022

Sci Rep

Self Cite

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tokyo, Japan, for 10 years from 2007 to 2016. The effects of changes in emission sources and their degradation by reaction with ozone were assessed in this study. There was no significant increasing or decreasing trend of the PAH concentrations during 10 years (P > 0.05). The average selected seven the PAH concentrations (0.88 ng m−3) during 10 years was lower than those in New York and Paris. However, the trend of ozone concentrations is increasing in central Tokyo. This inconsistency raises a question. Did the fact that the ozone concentration was higher than the PAH concentrations promote PAH degradation? To apportion the PAH sources, we used PAH concentration profiles and positive matrix factorization analysis. The contribution of vehicle emissions to the PAHs ranged from 40 to 80%. Ozone concentrations increased by 3.70%/year during 10 years. The theoretical degradation rates of PAHs by ozone, which were calculated using a pseudo-first-order rate equation, suggested that the lifetimes of benzo[a]pyrene (BaP) decreased by 1 min from 2007 to 2016. We investigated the aging of BaP using the profile of the isomer ratios. We found that the aging of BaP at the urban and roadside sites were nearly identical indicating aging regardless of the season. Although the decomposition of BaP is promoted by the photochemical oxidation reaction, this result suggests that a certain threshold value exists as the degree of the decomposition. This degradation of PAH can improve chemical loss processes in air quality model.

Section: Resultsmentioning

confidence: 99%

Effects of changes in polycyclic aromatic hydrocarbons (PAHs) emissions and degradation on their concentrations in Tokyo from 2007 and 2016

Nohchi

Maeshima

et al. 2022

Sci Rep

Self Cite

“…According to Brien et al, 30 which investigated the photolytic aging of secondary organic aerosol (SOA) in a laboratory experiment, there is a certain threshold for its decomposition. Shimada et al 31 point out that the coating of SOA is responsible for the existence of the BaP/BeP ratio threshold when transported long distance from China to Okinawa, Japan. They suggests that degradation of PAHs…”

Section: Resultsmentioning

confidence: 99%

Long-Term Trend of Polycyclic Aromatic 1 Hydrocarbon (PAH) Concentrations in Tokyo from 2007 to 2016: Effects of Changes in PAH Emissions and Degradation.

Nohchi

Maeshima

et al. 2021

Preprint

Self Cite

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tokyo, Japan, for 10 years from 2007 to 2016. The effects of changes in emission sources and their degradation by reaction with ozone were assessed in this study. There was no significant increasing or decreasing trend of the PAH concentrations during 10 years (P > 0.05). The average selected seven the PAH concentrations (0.88 ng m−3) during 10 years was lower than those in New York and Paris. However, the trend of ozone concentrations is increasing in central Tokyo. This inconsistency raises a question. Did the fact that the ozone concentration was higher than the PAH concentrations promote PAH degradation? To apportion the PAH sources, we used PAH concentration profiles and positive matrix factorization analysis. The contribution of vehicle emissions to the PAHs ranged from 40 to 80 %. Ozone concentrations increased by 3.70 %/year during 10 years. The theoretical degradation rates of PAHs by ozone, which were calculated using a pseudo-first-order rate equation, suggested that the lifetimes of benzo[a]pyrene (BaP) decreased by 1 min from 2007 to 2016. We investigated the aging of BaP using the profile of the isomer ratios. We found that the aging of BaP at the urban and roadside sites were nearly identical indicating aging regardless of the season. Although the decomposition of BaP is promoted by the photochemical oxidation reaction, this result suggests that a certain threshold value exists as the degree of the decomposition. This degradation of PAH can improve chemical loss processes in air quality model.

“…PAH concentrations at CHAAMS in each season were dominated by PAHs transported from China. PAH concentrations were highest in winter and lowest in spring (Shimada et al 2020;Miura et al 2019). We used the data classified as of Chinese origin by back trajectory in these references (Sato et al, 2007a;Sato et al, 2008;Yoshino et al, 2011;Ogawa et al, 2012;Miura et al, 2019).…”

Section: Accepted Manuscriptmentioning

confidence: 95%

Long-term Measurements of Carbonaceous Aerosol at Cape Hedo, Okinawa, Japan: Effects of Changes in Emissions in East Asia

Takami

Ishida

et al. 2021

Aerosol Air Qual. Res.

Self Cite

We investigated changes in sources of carbonaceous aerosol and their effect on long-term trends in elemental carbon (EC) and organic carbon (OC) concentrations at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, for the period 2004-2013. EC and OC concentrations were measured by using a semi-real-time carbon monitor and performing an offline filter analysis involving the thermal-optical method, following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol.Overall, the annual average concentration of EC did not change between 2004 and 2013, whereas the OC concentration clearly decreased at the rate of 0.11 μg C m −3 yr −1 (α > 0.05).