This study investigated seasonal variations in the mass concentration and chemical composition of ambient aerosols observed at three stations (coastal, mountainous, and downtown sites) in northern Taiwan from March 2009 to February 2012. The results show that the major aerosol components include ammonium, sulfate, nitrate, sea salt, dust, organic carbon, and elemental carbon, whereas the mass fraction of each species depends on the sampling location and season. A significant correlation (r = 0.7–0.8) was observed in aerosol concentrations measured at the respective stations, indicating that aerosol concentrations were dominated by regional‐scale factors. Ammonium, sulfate, and nitrate consistently reached respective peak values in the spring in conjunction with dust particle levels. This shows that the transport of dust and particulate air pollutants from the Asian continent has affected the atmospheric environment in this area. Distinct seasonality was observed for sea salt and secondary organic carbon (SOC): sea salt levels peaked in the autumn, whereas SOC levels peaked in the summer, implying that their sources were regulated by independent seasonal factors. Correlation between sea salt concentration and surface wind speed was derived from coastal measurements and showed a high value for the wind speed sensitivity parameter of around 0.37 for our location. In addition, it was revealed that the SOC concentration in aerosols was positively correlated with oxidant photolysis index (Ox × UVB), suggesting that the SOC seasonality was dominated by hydroxyl radical production.

Abstract. Photochemically driven nucleation bursts, which typically occur within a few hours after sunrise, often produce strong aerosol number concentration (ANC) fluctuations. The causes of such ANC spikes were investigated using a detailed aerosol model running in the parcel mode. Two potential mechanisms for the ANC spikes were proposed and simulated. The blocking of actinic flux by scattered clouds can significantly influence new particle production, but this does not cause strong fluctuations in the number of aerosols within sizes greater than the detection limit of our measurements. A more plausible mechanism is the turbulence eddy effect. Strong aerosol nucleation may occur in both updrafts and downdrafts, while the cloud formation at the boundary layer top strongly reduces the number of aerosols. As the number of aerosols is sensitive to turbulence eddy and cloud formation properties, a changing turbulence condition would result in large fluctuations in the evolution of ANC similar to that observed at the surface.

Coral skeletons are natural archives whose geochemical signatures provide insights into the tropical ocean history beyond the instrumental record. Carbon stable isotopes from coral skeletons (δ 13 Ccoral) have been used as a proxy for multiple variables on a seasonal basis. Long-term changes in coral δ 13 C relate to the changing isotopic composition of the dissolved inorganic carbon (δ 13 CDIC). δ 13 CDIC in turn reflects changes in the δ 13 C of atmospheric CO2, which in the modern Earth system is governed primarily by anthropogenic injection of CO2 into the atmospherea process known as the Suess Effect.Here we report three δ 13 C coral-based records of Siderastrea stellata from the tropical South Atlantic. U-series dating for the colonies 12SFB-1, 13SS-1 and 13SS-2 suggests these corals lived 13, 57 and 65 years, respectively. Short-term δ 13 C variations in their skeletal aragonite are dominated by inter-annual variation. All three δ 13 C records additionally exhibit an overall decreasing trend, with a depletion of about −0.0243 ± 0.0057 ‰.yr −1 (12SFB-1), −0.0208 ± 0.0007 ‰.yr −1 (13SS-1) and −0.0214 ± 0.0013 ‰.yr −1 (13SS-2). These rates of the coral records from Rocas Atoll are similar to the reported trend for the δ 13 C of atmospheric CO2 over the years 1960-1990 (−0.023 to −0.029 ‰.yr −1 ), and to the estimated decreasing rates of global δ 13 CDIC.Our findings suggest that multiple δ 13 C coral-based records are required for confidently identifying local changes in the δ 13 CDIC of the ocean. This information, in turn, can be used to infer changes in the δ 13 C of the atmospheric CO2 composition and provide valuable information about recent changes on the carbon biogeochemical cycle during the Anthropocene epoch.

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