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The International Maritime Organization (IMO) has formulated stringent ship emission regulations, and the global fuel sulfur limit of 0.50% became effective in 2020. Kitakyushu City is in the coastal suburbs of western Japan, and PM2.5 had already decreased prior to the global low-sulfur regulation, with concentrations in 2017, 2018, and 2019 of 12.2, 13.4, and 8.1 µg·m−3, respectively. The loading particles of the air masses passing through the Bohai Sea, Yellow Sea, and East China Sea in 2019 decreased to 3.4 µg·m−3, which was obviously higher than that of other air masses (0.5 µg·m−3), and the contribution of nss-SO42− could reach 56%, followed by OC (23%) and NH4+ (21%). Moreover, the characteristics of typical ship-emitted metals (V, Ni, As, Sb, W, and Cd) also changed greatly. Their sum concentrations in 2017, 2018, and 2019 were 10.6, 11.1, and 6.9 ng·m−3, respectively, which showed an annual variation similar to that of nss-SO42−. As for the particle exposure risk, the lowest chronic effect and carcinogenic risk were observed in 2019, with hazard indices (HI) for adults and children of 0.9 and 7.6, and carcinogenic risks (CRs) of 3.8 × 10−5 and 8.4 × 10−5, respectively. In this study, the health risks as well as air quality prior to the enforcement of the MARPOL Treaty in the leeward area of the Asian continent were totally and more precisely studied and evaluated based on the annual dataset; revealing the influence of trans-boundary transportation under individual Chinese regulations on the particle characteristic variations in Kitakyushu, Japan. [ABSTRACT FROM AUTHOR]

The equilibrium between nitric acid gas (HNO3(g)) and ammonium nitrate aerosol (NH4NO3(p)) in ambient air was studied based on the monitoring data obtained using a five-stage filter-pack system, in which the fine aerosol and the coarse aerosol were separately collected; this made it possible to evaluate the actual situation of the equilibrium more accurately. The partition between HNO3(g) and coarse particulate nitrate (c-NO3-(p)), as well as that between HNO3(g) and fine particulate nitrate (f-NO3-(p)), could be evaluated individually thanks to the classification separation of the aerosol by size. The c-particle proportion c-NO3-(p)/(c-NO3-(p) + HNO3(g)) between HNO3(g) and c-NO3-(p) had a weak negative correlation (r = -0.46, p<0.001) with air temperature; in contrast, the f-particle proportion f-NO3-(p)/(f-NO3-(p) + HNO3(g)) between HNO3(g) and f-NO3-(p) had a moderate negative correlation (r = -0.80, p<0.001) with air temperature in total; furthermore, the f-particle proportion had an interesting and discriminative dependence on air temperature which could be divided into two regions by an air temperature around 15°C. The condition of high air temperature accompanied by high relative humidity frequently resulted in the deliquescent state of NH4NO3(p), providing the disconnect from the theoretical prediction for the products of [NH3(g)] and [HNO3(g)] ([NH3(g)][HNO3(g)]) by Seinfeld and Pandis (1998). [ABSTRACT FROM AUTHOR]

The daily mean concentration of gaseous mercury (Hg0) in an industrialized city in Japan was determined during almost 2 years. The Hg concentration largely fluctuated daily. By applying fast Fourier transform (FFT) analysis, different annual and seasonal variation were clarified. In spite of the large daily fluctuation and different annual and seasonal variations, it was noteworthy that an increasing trend was shown; however, it was strongly suggested that it is necessary to continue the determination for a longer duration. The daily fluctuation also implied the possibility that the precipitation was related to the variation in the Hg concentration. We introduced two new parameters for understanding and evaluating the actual potential risk, potential exposure, as well as the calculated—not actual—probability of risk to be suffered, the strength of the potential risk. At our observation site, the potential exposure was mainly controlled by the frequency of the wind from each direction; in contrast, the strength of the potential exposure was compositely determined by the Hg concentration as well as the wind speed. [ABSTRACT FROM AUTHOR]

Particulate sulfate (SO42−) usually exists in the atmosphere in the chemical form of (NH4)2SO4 and/or NH4HSO4. In contrast, we could successfully detect particulate sulfuric acid (H2SO4) without neutralization by ammonia in the monitoring campaign by filter pack methods. The presence of ambient H2SO4 was revealed from the concentration difference in a nitric acid gas (HNO3) determined by a four-stage filter pack and a five-stage filter pack. Ambient H2SO4 could exist more frequently in summer (August) than in winter (January). Trajectory analysis identified the attribution of ambient H2SO4 as follows: in summer, SO2 released from a domestic volcano in Japan was responsible for the ambient H2SO4, while in other seasons, SO2 was carried to the survey site by northwestern air masses from the Asian continent. [ABSTRACT FROM AUTHOR]

To precisely determine the nitric acid (HNO3) concentration in ambient air, we developed a new methodology to evaluate and correct the sampling artifact in the four-stage filter pack method and the chlorine loss in ambient air. Our new methodology is widely applicable to the dataset accumulated by the four-stage filter pack method in the world (e.g., EANET activity in East Asia), and by applying our methodology, we can precisely understand the transition of the HNO3 concentration back in the past. In order to correct the sampling artifact in the four-stage filter pack method, we firstly evaluated the non-sea-salt- (nss-) chloride concentration, and successively introduced three parameters: total NO3 = NO3- + HNO3, "Initial" HNO3 = HCl – nss-Cl + HNO3, and "Primary" HNO3 = "Initial" HNO3 – (α/(1-α)) NO3, (α, the loss rate of NO3 in the dissociation of NH4NO3). As a result of the evaluation for seasonal variation in 1-year dataset by our new methodology, it was clarified at our study site that the artifact had insignificant influence on the seasonal patterns of the HNO3 concentration; in contrast, under the comprehensive impact (from both sampling artifact and chlorine loss reaction), spring was most affected, resulting in the significant change of the seasonal pattern in the HNO3 concentration. [ABSTRACT FROM AUTHOR]