Residence time of arctic haze aerosols using the concentrations and activity ratios of ~210Po, ~210Pb and ~7Be

摘要

Pollutants from mid-Iatitudes (mainly from Eurasia) reach the polar region through long-range atmo- spheric transport during winter. Due to very low precipitation in the arctic region, the pollutant-laden aerosols in the stable, and dark polar atmosphere are believed to have relatively longer residence times. The disequilibrium between the daughter products of 222Rn, in conjunction with the concentrations of 7Be in arctic aerosols can be utilized to obtain information on the residence times and sources of the arctic haze. We have carried out a pilot study to explore the feasibility of determining the residence time of aerosols from the arctic haze. Towards this, we have analyzed 10 aerosol samples from two stations, Poker Flat and Eagle, Alaska for the concentrations and activity ratios of 7Be, 210pO, and 21°Pb. The activity ratios of21°po/21°Pb varied between 0 and 0.177. The corresponding residence time obta￥1ed using the disequilibrium between the 210pO and 21°Pb, varied between 0 and 39 days. This is the first time an estimate on the residence time of aerosols from the arctic haze is determined. The 7Be/21°pb activity ratios varied between 2.2 and 14.0, possibly suggesting varying inputs of 7Be from the upper atmosphere to the arctic atmosphere. Since long-range atmospheric transport is one of the major pathways of arctic pollution, this study has potential significance on the fate and transport of inorganic and organic atmospheric pollutants in the arctic region.