Optical properties and source analysis of aerosols over a desert area in Dunhuang, Northwest china

Abstract

Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China (Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth (AOD) at 500 nm was 0. 32 ± 0. 06,and the Angstrom exponent (α) was 0. 73 ± 0. 27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM (March–April–May) resulted in the seasonal maximum AOD,0. 41 ± 0. 04,and a relatively smaller α value,0. 44 ± 0. 04. The tourism seasons,JJA (June–July–August) and SON (September–October–November) coincide with serious emissions of small anthropogenic aerosols. While in DJF (December–January–February),the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and α were 0. 29 ± 0. 02 and 0. 66 ± 0. 17,respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM,ranges of AOD (0.11–1.18) and α (0.06–0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF,the similar ranges of AOD and α under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.