Identification of Long-range Transported Polycyclic Aromatic Hydrocarbons in Snow at Mt. Tateyama, Japan

Kazuichi Hayakawa,Ning Tang,Akira Toriba,Kazuma Aoki,Edward G Nagato

doi:10.4209/aaqr.2018.05.0153

Abstract

ABSTRACT Snow layers, L-I to -III, collected from the wall of a snow pit at Murododaira on Mt. Tateyama, Japan, were melted and filtered into soluble (S) and particulate (P) fractions by a glass filter (pore size: 0.5 µm). The total concentration of the polycyclic aromatic hydrocarbons (PAHs) was highest in L-I. In this layer, PAHs with 5–6 rings, which exist mainly in particulate matter (PM) in the atmosphere, were almost completely in the P-fraction. PAHs with 4 rings, which exist in both the particle and the gas phase in the atmosphere, exhibited higher or equal concentrations in the S-fraction. Finally, non-sea salt SO42−, which exists as sulfur oxides in the atmosphere, was filtered into the S-fraction. The air mass for L-I, traced via back trajectory, passed through northeastern and central China. These results suggest that PAHs transported from China to Japan precipitated in snow at Mt. Tateyama. In the melted snow, PM-associated PAHs were primarily in the P-fraction, but lower molecular-weight PAHs were partly in the S-fraction. Gas-phase PAHs were also found in the S-fraction. Furthermore, the high concentration of non-sea salt Ca2+ in the S-fraction of L-I implies the presence of Asian Dust.

Highlights

Asian Dust and sulfates are long-range transported from the Asian continent to Japan over the Sea of Japan (Iwasaka et al, 1988; Nishikawa et al, 1991)
The air mass for L-I, traced via back trajectory, passed through northeastern and central China. These results suggest that polycyclic aromatic hydrocarbons (PAHs) transported from China to Japan precipitated in snow at Mt
PAHp moves mainly into the P-fraction (PAHp) but partly into the S-fraction (PAHs) in the case of PAHs with 5 rings or fewer (Eq (4)). These results suggest that the gas-phase PAH in the atmosphere exists as the S-fraction in snow clouds, while particulate matter (PM)-associated PAH exists as the Pfraction in snow clouds but dissociates partly to the Sfraction in the melted snow

Summary

Introduction

Asian Dust (yellow sand) and sulfates are long-range transported from the Asian continent to Japan over the Sea of Japan (Iwasaka et al, 1988; Nishikawa et al, 1991). We collected total suspended particulate matters (TSP) at Wajima Atmospheric Monitoring Site (WAMS), Kanazawa University, on the Noto Peninsula, Japan, downstream of the westerlies from the Asian continent and analyzed polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) in the TSP. Atmospheric PAH and NPAH concentrations at WAMS increased in winter season every year. Mt. Tateyama (3,015 m above sea level), one of the highest mountains on the west coast of Honshu, Japan, is about 110 km southeast of WAMS (Fig. 1). Tateyama could be useful for studying long-range transported atmospheric pollutants Several pollutants such as Asian Dust and sulfur oxides in snow in this area were reported (Honoki et al, 2001; Osada et al, 2004; Watanabe et al, 2011a)

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Conclusion