Pristine atmospheric condition over the Third Pole:An insight from levoglucosan records

Expanding urbanization and agricultural intensification across neighboring South Asia and East Asia have substantially threatened atmospheric condition over the Third Pole(TP)during the past few decades.Whether the atmospheric condition over the TP is still as clean as a representative of the regional background draws great concern.In this work,great differences in levoglucosan concentration within/above the atmospheric boundary layer height are revealed.Levoglucosan results support the hypothesis that atmospheric pollutants in the mid-troposphere over the TP are mainly affected by long-range transport,although there are some local biomass burning emissions in residential areas.In addition,levoglucosan concentration in the midtroposphere over the TP is at the same magnitude as marine and polar regions,but about 2–3 magnitudes lower than neighboring densely-populated Asian regions.With insights of levoglucosan records,this work therefore proves that the high-altitude TP still has largely pristine atmospheric conditions,and is one of the cleanest remote regions on the Earth.