Abstract
The geochemical fingerprint of potential source areas (PSA) of mineral dust to the atmosphere have been investigated across North Africa, North and South America, Australia and East Asia. In contrast, the vast arid and semi-arid areas in West and Central Asian segments of the so-called, African-Asian "dust belt".remain poorly characterized, in spite of encompassingup to %30 to the global natural and anthropogenic dust emissions annually In a step towards improving the regional dataset of mineral dust composition, we focus on the radiogenic Sr and Nd isotopic composition to differentiate various sources of modern dust, we present high-precision isotope data in samples of volcanic ash deposits, as well as fine-grained (<20 mm) lake sediments from west and northwest Iran. We combined these measurements with the previously published data sets to better characterize the isotopic signature of these PSAs. Aerosol vertical distributions and qualitative speciation of the aerosol mass yield by the available CALIOP images for the studied area indicates the presence of dust in the atmospheric profile during the high emission seasons of boreal spring and summer. Six-hour air mass forward-trajectory form the sampling area for selected days in spring and summer reveals two different wind patterns during the spring and summer. The forward-trajectory also indicates that the air masses mobilized from the sampling regions overlap greatly even after a relatively short period of six hours. The (super 87) Sr/ (super 86) Sr values in the study area ranges from 0.704435+ or -0.000010 to 0.708338+ or -0.000010, where more radiogenic values are observed near the Urmia Lake and Eslami Isand. The epsilon Nd (deviation from the Chondritic Uniform Reservoir) ranged between -4.3 to 5.6, where the most radiogenic values appeared in Maku, where the least radiogenic epsilon Nd values are observed near the Urmia Lake and Eslami Island. Radiogenic Sr and Nd isotopes in surficial samples from the PSAs in W-NW Iran compared to the world's source regions indicate that the majority of the samples from W-NW Iran are clustered together near the mantle source with almost no overlap with other global PSAs. Samples from Urmia Lake and Eslami Island regions are distinctively clustered away from other sampling regions and overlapped with the Holocene paleo-dust samples from NW Iran.