OPTICAL-ABSORPTION BY AEROSOL BLACK CARBON AND DUST IN A DESERT REGION OF CENTRAL-ASIA

In September 1989 a joint U.S.S.R.-U.S. study of the causes and effect s of desert dust on the environment was conducted in the Tadzhik S.S.R . in Soviet Central Asia. The objectives of the study included measure ments of optical absorption by suspended material, both windblown dust and aerosol ''black'' carbon. This latter material is a combustion ef fluent, prevalent in emissions from poorly controlled burning, with a long atmospheric lifetime and a large cross-section for the absorption of visible radiation. The measurements obtained from the analysis of filter samples indicate that only during periods of active dust produc tion was there a significant contribution of dust to total absorption. At other times, the presence of black carbon from local and regional sources accounted for approximately 90 degrees of the total aerosol op tical absorption. The conclusions are that fuel combustion may produce a greater optical impact on the atmosphere in less-developed areas of the world than that arising from the effects of desert dust productio n.