Air–water exchange fluxes of polycyclic aromatic hydrocarbons in the tropical coast, Taiwan

Abstract

Air–water exchange fluxes of polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in air and water samples from two sites on the Kenting coast, located at the southern tip of Taiwan, from January to December 2010. There was no significant difference in the total PAH (t-PAH) concentrations in both gas and dissolved phases between these two sites due to the less local input which also coincided to the low levels of t-PAH concentration; the gas and dissolved phases averaged 1.29±0.59ngm−3 and 2.17±1.19ngL−1 respectively. The direction and magnitude of the daily flux of PAHs were significantly influenced by wind speed and dissolved PAH concentrations. Individual PAH flux ranged from 627ngm−2d−1 volatilization of phenanthrene during the rainy season with storm–water discharges raising dissolved phase concentration, to 67ngm−2d−1 absorption of fluoranthene during high wind speed periods. Due to PAH annual fluxes through air–water exchange, Kenting seawater is a source of low molecular weight PAHs and a reservoir of high molecular weight PAHs. Estimated annual volatilization fluxes ranged from 7.3μgm−2yr−1 for pyrene to 50μgm−2yr−1 for phenanthrene and the absorption fluxes ranged from −2.6μgm−2yr−1 for chrysene to −3.5μgm−2yr−1 for fluoranthene.