Variations of regional background peroxyacetyl nitrate in marine boundary layer over Baengyeong Island, South Korea

Concurrent two-week measurements of peroxyacetyl nitrate (PAN), other photochemically reactive species (including O3, CO, NO2, and volatile organic compounds), and aerosols (water-soluble ionic species, organic and elemental carbon, and trace metals) were made at an atmospheric monitoring station on Baengyeong Island in the summer and autumn of 2010 and winter and spring of 2011. PAN mixing ratios ranged from the below the detection limit of 0.01–2.47 ppbv, with a median of 0.04, 0.58, 0.32, 0.17 ppbv during the summer, autumn, winter; and spring, respectively. Although the photochemical ages determined from the PAN/NOx ratios indicated that the measurement site was situated under a relatively clean marine boundary layer, significant and abrupt increases in PAN were frequently observed due to transport from nearby land masses, mainly China and South Korea. The vertical trend of PAN with a mid-altitude maximum observed in this study is consistent with previous aircraft campaigns near the site. However, the PAN concentration recorded in this study was about two times higher than those of previous studies at remote marine surface sites in the southern Yellow Sea. In most cases, the marine boundary layer acted as an overall sink for PAN. However, we found that in-situ photochemical production of insoluble PAN also contributes to maintaining high-PAN mixing ratios in the boundary layer over the Yellow Sea and plays a role in the regional transport of reactive nitrogen species.