资源环境科技发展态势分析平台

Dimethylaminium (DMA(+)) and trimethylaminium (TMA(+)) ions in size-segregated atmospheric particles are measured across the marginal seas of China and the northwest Pacific Ocean (NWPO) in March-May 2014. The concentrations of DMA(+) and TMA(+) in particles with diameters of 0.056-10 mu m (PM0.056-10) collected from the eutrophic seas are 0.22 +/- 0.38 nmol/m(3) and 0.11 +/- 0.23 nmol/m(3), respectively. Surprisingly, an average TMA(+) concentration that is 1 order of magnitude higher and a slightly higher average DMA(+) concentration are observed across the oligotrophic NWPO. However, the concentrations of chlorophyll-a in the NWPO are approximately 5 times lower than those in the marginal seas. The maximum concentrations of TMA(+) (4.39 nmol/m(3)) and DMA(+) (0.92 nmol/m(3)) in PM0.056-10 are observed close to the largest cyclonic eddy in the NWPO under an average wind speed of 14 m/s. The concentrations of TMA(+) increase with decreasing particle size in the sample, whereas those of DMA(+) exhibit a condensation mode at 0.2 mu m and a droplet mode at 1-2 mu m. The bimodal size distribution of DMA(+) is conventionally interpreted in terms of secondary reactions in the atmosphere. The unique size distribution of TMA(+) suggests that it very likely originates from sea-spray aerosols. Based on their size distributions in other samples collected over the NWPO, these conclusions may generally apply for TMA(+) and DMA(+). Moreover, we propose a novel conceptual model to explain how the largely increased primary TMA(+) and secondary DMA(+) are linked to emissions of sea-spray aerosols and gaseous precursors from various cyclonic eddies.