Hygroscopicity and CCN Activity of Water-Soluble Extracts From the Arctic Aerosols in Winter to Early Summer

• The hygroscopicity and cloud condensation nuclei (CCN) activity of water-soluble extracts from Arctic lower tropospheric aerosols during winter to summer were investigated under sub- and super-saturated conditions, with chemical composition and air mass origin. The κ values from the hygroscopic growth factor at 80%–90% relative humidity (κHTDMA) during winter, spring, and summer were 0.34 ± 0.06, 0.41 ± 0.05, and 0.25 ± 0.02, respectively, whereas those derived from CCN activation diameter at 0.29%–0.59% supersaturation (κCCNC) were 0.42 ± 0.03, 0.43 ± 0.05, and 0.34 ± 0.11, respectively. The hygroscopicity and CCN activity showed clear seasonal variations following changes in composition that are linked to natural, anthropogenic, and biogenic sources. During winter and spring, κ was high when highly hygroscopic components such as sea salts, sulfate, and highly-oxidized/aged particles were dominant due to long-range atmospheric transport and photochemical reactions. In contrast, κ was significantly lower in summer when water-insoluble (22%) and water-soluble organic matter (OM) (17%) were dominated with high biogenic activity associated with ice-edge zones. The κCCNC and κHTDMA values agreed well within 8% and the surface tension agreed with that of pure water within 10%. The κ for OM (κOM) estimated from chemical composition during spring and summer was on average 0.04 ± 0.06 (up to ∼0.17). This result suggests that highly hygroscopic components such as sea salt and sulfate mainly controlled particle hygroscopicity and CCN activity in winter, but water-soluble OM could also contribute in spring and summer.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

hygroscopicity of Arctic aerosols

CCN activity

seasonal variation

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