Seasonal variations of sulfate, carbonaceous species (black carbon and polycyclic aromatic hydrocarbons), and trace elements in fine atmospheric aerosols collected at subtropical islands in the East China Sea

Abstract

In order to characterize the outflow of pollution derived aerosols from the Asian Pacific rim to the North Pacific Ocean, seasonal variations of fine aerosol components (aerodynamic diameter <2 μm) were collected at two islands (Amami Island and Miyako Island) that surround the East China Sea. Monthly averaged concentrations of non‐sea‐salt SO42− (nss.SO42−) and black carbon (BC) at Amami and Miyako showed relatively high values in winter to spring and low values in summer. The observed seasonal variation is basically determined by the northwesterly monsoon in winter to spring and southeasterly wind from the stationary North Pacific anticyclone in summer. The minimum concentration levels of nss.SO42− and BC in summer were almost 2–3 times that of the North Pacific background level. Trace metals in aerosols showed similar seasonal variations observed for nss.SO42− and BC. The concentrations of nss.SO42− and Sb were highly correlated; this is in contradiction with the results at stations established in Pacific Exploratory Mission‐West ground monitoring sites. Polycyclic aromatic hydrocarbons (PAHs) also showed a pronounced maximum in winter and/or spring, with maximum concentrations comparable in magnitude to those in spring at Barrow, Alaska. Many of the low molecular weight species of PAHs had high correlation with BC, suggesting that they were either transported independently in a similar way or were transported attached to BC. Furthermore, the relative abundance of some PAH species in the present study and those found in deep‐ocean surface sediments sampled in the middle Pacific Ocean are compared and discussed.