Seasonal and annual changes in PAH concentrations in a remote site in the Pacific Ocean

Kaori Miura,Kei Sato,Neng-Huei Lin,Kojiro Shimada,In Sun Kim,Shiro Hatakeyama,Taichi Sugiyama,Akinori Takami,Yong Pyo Kim,Chak K Chan

doi:10.1038/s41598-019-47409-9

Abstract

This paper reports the long term observation of particle-associated polycyclic aromatic hydrocarbons (PAHs) at Cape Hedo Atmosphere and Aerosol Monitoring Station, a remote site in the Western Pacific Ocean, from 2008 to 2015. This is the first long-term study that evaluated the contribution of long-range transport of PAHs in East Asia. No obvious trend (P > 0.05) was found in a particular season over the years. However, there are seasonal variations of PAH concentrations with higher in spring and winter. The higher PAH are attributed to air masses from the area including part of China. Source apportionment using three different approaches, i.e., PAH compositional pattern analysis, PAH diagnostic ratio analysis and positive matrix factorization modeling, showed the combined high contribution of biomass burning (18%, 14%) and coal combustion (33%, 24%) in spring and winter. In addition, the contribution of ship emissions (35%) was relatively high in spring, whereas that of vehicle emissions (36%) was relatively high in winter. The contribution of coal combustion to PAH has decreased throughout the years, likely due to changes in energy structure in China. The contribution of biomass burning to PAH has showed no trend, being stable, and that of vehicular emissions has increased.

Highlights

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that originate mainly from incomplete combustion of organic materials
We have made observations of atmospheric aerosols from 2008 to 2015 at the Cape Hedo Atmosphere and Aerosol Measurement Station (CHAAMS) in Okinawa, Japan, a remote site between East Asian Continent and Japan used in the Atmospheric Brown Cloud (ABC) project of the United Nations Environment Programme (UNEP) for investigating the long term transboundary air pollution in East, Southeast, and South Asia[5,6]
Using a potential receptor influence function model, Lang et al suggested that polycyclic aromatic hydrocarbons (PAHs) emitted from northeastern China were transported to CHAAMS by northwesterly wind that occurred most frequently during winter-spring months[7]

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that originate mainly from incomplete combustion of organic materials They are primarily associated with fine particles, and their sources in ambient aerosol are vehicle exhaust and combustion of biomass and fossil fuel[1]. PAHs emission sources are coal combustion in East Asia and biomass burning in Southeast, and South Asia. Understanding the change of PAHs source in the atmosphere is important to evaluate for the long term trends of PAHs concentrations. The objectives of this study are to (1) determine the long term trends of the PAHs concentrations at CHAAMS, (2) identify the sources of the observed PAHs based on long term data sets and (3) evaluate the impacts of reduction in emissions in China in these observed trends

Objectives

Methods

Results