Abstract
PM2.5 (fine particles with diameters 2.5 micrometers and smaller) and PM>2.5 were separately collected in Kanazawa, Japan in every season, from the spring of 2017 to the winter of 2018, and nine polycyclic aromatic hydrocarbons (PAHs) and six nitropolycyclic aromatic hydrocarbons (NPAHs) were respectively determined using high-performance liquid chromatography (HPLC) with fluorescence and chemiluminescence detections. The atmospheric concentrations of both the PAHs and NPAHs showed seasonal changes (highest in the winter and lowest in the summer), which differed from the variations in the total suspended particulate matter (TSP) and PM2.5 amounts (which were highest in the spring). The contributions of major sources to the combustion-derived particulate (Pc) in the PM2.5 were calculated using the 1-nitropyrene-pyrene (NP) method, using pyrene and 1-nitropyrene as the representative markers of PAHs and NPAHs, respectively. The annual average concentration of Pc accounted for only 2.1% of PM2.5, but showed the same seasonal variation as PAHs. The sources of Pc were vehicles (31%) and coal heating facilities/industries (69%). A backward trajectory analysis showed that the vehicle-derived Pc was mainly from Kanazawa and its surroundings, and that coal heating facilities/industry-derived Pc was transported from city areas in central and northern China in the winter, and during the Asian dust event in the spring. These results show that large amounts of PAHs were transported over a long range from China during the winter. Even in the spring, after the coal heating season was over in China, PAHs were still transported to Japan after Asian dust storms passed through Chinese city areas. By contrast, the main contributors of NPAHs were vehicles in Kanazawa and its surroundings. The recent Pc concentrations were much lower than those in 1999. This decrease was mostly attributed to the decrease in the contribution of vehicle emissions. Thus, the changes in the atmospheric concentrations of Pc, PAHs and NPAHs in Kanazawa were strongly affected not only by the local emissions but also by long-range transport from China.
Highlights
Air pollution caused by particulate matter (PM) is a growing global concern
Polycyclic aromatic hydrocarbons (PAHs) and their derivatives—such as nitropolycyclic aromatic hydrocarbons (NPAHs)—are known as carcinogens and/or mutagens
The daily weather map showed a typical pattern in which the wind flowed from the Asian Continent towards the Islands of Japan after a cold front passed over the Sea of Japan. These results strongly suggest that the increase of total suspended particulate matter (TSP) in the three days was caused by an Asian dust event
Summary
Air pollution caused by particulate matter (PM) is a growing global concern. The. Chinese and Russian cities, especially in the central and northern parts of China, showed extremely high concentrations of PAHs and NPAHs in winter. This was attributed mainly to emissions from coal heating facilities. A backwards trajectory analysis showed that the air masses travelled over mega city areas in central and northern China [9] This suggests that the emissions of PAHs and NPAHs in China may have an impact on Kanazawa, because Kanazawa is only about 100 km south of the WAMS (Figure S1). The seasonal changes in vehicular and coal combustion contributions to combustion-derived particulates in Kanazawa, and the impact of trans-boundary transport from China are further clarified
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