资源环境科技发展态势分析平台

We present vertically resolved observations of aerosol composition during pristine summertime Arctic background conditions. The methansulfonic acid (MSA)-to-sulfate ratio peaked near the surface (mean 0.10), indicating a contribution from ocean-derived biogenic sulfur. Similarly, the organic aerosol (OA)-to-sulfate ratio increased toward the surface (mean 2.0). Both MSA-to-sulfate and OA-to-sulfate ratios were significantly correlated with FLEXPART-WRF-predicted air mass residence time over open water, indicating marine-influenced OA. External mixing of sea salt aerosol from a larger number fraction of organic, sulfate, and amine-containing particles, together with low wind speeds (median 4.7ms(-1)), suggests a role for secondary organic aerosol formation. Cloud condensation nuclei concentrations were nearly constant (approximate to 120cm(-3)) when the OA fraction was <60% and increased to 350cm(-3) when the organic fraction was larger and residence times over open water were longer. Our observations illustrate the importance of marine-influenced OA under Arctic background conditions, which are likely to change as the Arctic transitions to larger areas of open water.