Concentrations and Sources of Atmospheric PM, Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons in Kanazawa, Japan

Contributions of long-range transport from the Asian continent and local emissions on atmospheric PM2.5, polycyclic aromatic hydrocarbons, and their nitro-derivatives in Kanazawa and Noto Peninsula, Japan

This study collected samples of particulate matter that are 2.5 μm or less in diameter (PM2.5) in Kanazawa, Japan, and Noto Peninsula located 100 km north on the windward side of the westerlies from the Asian continent and characterized the extent of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) pollution in Kanazawa. Emission areas and specific sources of PM2.5 and of PAHs and NPAHs were clarified via back-trajectory analysis and the NP-method, respectively. The results indicate that during 2020 and 2021, most PAHs (93%) in Kanazawa were transported from the Asian continent by westerlies and that the main source was coal and biomass combustion. The presence of NPAHs in Kanazawa was caused by a mixture of transport from the Asian continent (53%) and local emissions (47%), with the main source of the latter being from vehicles. Although the content of combustion-derived particulates (Pc) was <2.4% of PM2.5 in Kanazawa, this showed a similar seasonal variation (winter > summer) to that of PAHs. The contribution of Pc transported from the Asian continent exceeded that of locally emitted Pc. The current situation of Kanazawa is considerably different from that of 1997, when local vehicles were the main source of pollution.

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.

Polycyclic Aromatic Hydrocarbons in the Atmosphere of the Southern Baikal Region (Russia): Sources and Relationship with Meteorological Conditions

This article presents the results of the long-term studies at two stations located in the city of Irkutsk and the Listvyanka settlement of the southern Baikal region (East Siberia) concerning the concentration of polycyclic aromatic hydrocarbons (PAHs) in atmospheric aerosol. The studies revealed the seasonal and interannual dynamics in the distribution of PAHs in aerosols from urban (source) and rural (receptor) areas. We carried out a comprehensive analysis of weather conditions such as wind direction, relative humidity, air temperature, and atmospheric pressure. The analysis determined high correlations between air temperature, atmospheric pressure, temperature inversions, and PAHs at the monitoring stations. The average annual concentrations of PAHs in the abnormally warm 2020 were three times lower than the average values obtained in the cold 2016. The toxic equivalent concentrations (BaPeq) increased from summer to winter with an increase in the contribution from benzo(a)pyrene, one of the most toxic and hazardous compounds of this class of organic substances. Four-, five- and six-ring PAHs mainly predominated in aerosol; the proportion of two- and three-ring PAHs increased from the warm season to the cold season. Diagnostic ratios of PAHs identified the main sources of air pollution by this class of compounds: combustion of coal, liquid fuel and firewood, vehicle emissions, and wildfires. The percentage of the transport of anthropogenic aerosol containing PAHs from industrial sources of the Southern Baikal region towards Lake Baikal was 65 to 71%.

Long-Term and Seasonal Changes in Sources of Urban Atmospheric Particulates in the Western Pacific

To reduce atmospheric pollutants, the sources need to be identified. To this end, combustion-derived particulates (Pc) in atmospheric suspended particulate matter (TSP) in ten Western Pacific cities from 1997 to 2018 were analyzed using the NP method, which we have recently developed. The method separates Pc into particulates originating from high-temperature (Ph) and low-temperature (Pl) combustion sources. Using this method, ten cities in the Asia-Pacific region were separated into three classes. Class 1: commercial cities whose major contributor to Pc was from vehicles, and which showed lower [Pc] values with larger [Ph]/[Pc] ratios. Sapporo, Kanazawa, Tokyo, Sagamihara (Japan), Shanghai (China), and Busan (Korea) were contained in this class. Class 2: cities whose main source of Pc was from coal heating, and which showed much higher winter [Pc] with larger [Pl]/[Pc] ratios. Beijing, Shenyang (China), and Vladivostok (Russia) were contained in this class. Class 3: steel manufacturing city which showed lower [Pc] with larger [Pl]/[Pc] ratio. The low [Pc] appeared to be due to elimination of Pl from coke oven plants. Only Kitakyushu was contained in this class. This study has elucidated the contribution of sources to urban atmospheric TSP in the Western Pacific that was previously unknown. Overall [Pc] was decreasing in this region, mainly due to the decreasing contribution of vehicles to Pc, but not due to a decrease in coal combustion.

Calculating source contributions to urban atmospheric polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons using 1-nitropyrene and pyrene: An application to an Asian dust event

A method to calculate source contributions to atmospheric polycyclic aromatic hydrocarbons (PAHs) and their nitrated congeners (NPAHs) is proposed, using pyrene (Pyr) and 1-nitropyrene (1-NP), as respective representatives of PAHs and NPAHs. This is based on the known increases in NPAH to PAH ratios as combustion temperatures increase. The fractions of 1-NP and Pyr from high temperature combustion sources in total 1-NP and Pyr are respectively calculated as a (0 < a <1) and b (0 < b < 1). By using atmospheric concentrations of Pyr and 1-NP obtained at monitoring sites, contributions of high and low temperature combustion sources were calculated. Using this method, the contributions of automobiles and coal combustion facilities/industries to atmospheric Pyr and 1-NP concentrations were calculated for atmospheric samples collected in Kanazawa, Japan during a seasonal Asian dust event. The results show that Pyr was almost entirely emitted from industries in China and transported long-range to Japan. By contrast, 1-NP was emitted primarily from automobiles in Kanazawa and its surrounding areas, with a small amount of 1-NP possibly transported from China. The proposed method can provide greater clarity on source identification compared to the typically used PAH isomer pairs.