Relationships between aerosol and snow chemistry at King Col, Mt. Logan Massif, Yukon, Canada

Abstract

Simultaneous samples of aerosol ( n = 48 ) and recent snow ( n = 193 ) chemistry were collected at King Col (4135 m) in the St. Elias Mountains, Yukon, between 17 May and 11 June 2001. Major ion concentrations in aerosol samples were low with the total ionic burden averaging 5.52 neq m −3 at standard temperature and pressure (STP). Interspecies aerosol relationships indicate the presence of (NH 4) 2SO 4 aerosol at King Col. An aerosol Cl − deficiency relative to seawater suggests volatilization of HCl by reaction with unneutralized SO 4 2 - that is present in half of the samples. Backwards trajectories for select aerosol concentration peaks document the transport of Asian dust and anthropogenic emissions, the eruption plume from the 22 May eruption of Sheveluch, Kamchatka, and sea salt from the marine boundary layer over the Gulf of Alaska to King Col during the sampling period. Fresh snow chemistry generally mimics aerosol chemistry with similar relative abundances and interspecies relationships except for large enrichments in snow Cl − and NO 3 - relative to aerosol due to snow scavenging of gas-phase HCl and HNO 3. Although relatively strong correlations between aerosol and snow concentrations were observed for species associated with accumulation mode aerosols, e.g. NH 4 + ( r = 0.56 ) and SO 4 2 - ( r = 0.43 ), only weak correlations were observed for dust and sea-salt species. These results are influenced by greater variability in concentrations between replicate snow samples for species associated with coarse mode dust and sea-salt particles and by snow scavenging of gas-phase HCl and HNO 3.