Even-numbered n-alkanes/n-alkenes predominance in surface sediments of Gabes Gulf in Tunisia

We investigated the mineral composition and trace element contents of dustfall with different deposited phases at the Minqin Oasis, in China’s Hexi Corridor. The contents of elements such as Pb, Cd, Cu, As, Sb, Se, Rb, Cs, and Ba (believed to be of anthropogenic origin) indicated that the significance of human impacts on dust emissions increased from 1970s to the early 2000s. However, variations in the content of elements including Sc, Mn, Na, Cr, V, Eu, Ce, Nb, Zr, La, and Ce (believed to originate from natural processes such as physical and chemical weathering) show no obvious changes in the major potential dust source areas (PSAs) in this region. In addition, analysis of the assemblage of trace elements in dustfall indicated that the elements assumed to originate from anthropogenic and natural processes appear to be intertwined, leading to difficulties and uncertainties in identifying the PSAs and evaluating the significance of human impacts on dust emissions. Comparisons of the element contents of dustfall collected in Beijing and Minqin with similar data for Beijing show that under different conditions some differences in ranges are permitted; the contents of most trace elements were similar even though the dustfall in the two areas came from different sources. These results suggest that before attempting to identify major PSAs, researchers should perform an integrated analysis that includes the mineral, elemental, geomorphological, vegetation cover, climatic conditions, and other characteristics of the regions being studied.