Characteristics of carbonate content and carbon and oxygen isotopic composition of northern China soil and dust aerosol and its application to tracing dust sources

The carbonate content and the carbon and oxygen isotopic composition of carbonate were determined for 28 surface soil samples from northern China and 30 dust aerosol samples collected at four sites in northern China: Aksu, Dunhuang, Yulin and XiAn. The carbonate content and stable C isotopic composition show distinctly different values for dust from different sources, both vary inversely with annual mean precipitation and also vary as function of grain size. The δ13C value in the aerosol is lower and the δ18O higher than in local bulk surface soils because the particle-size distribution in the aerosol is skew toward smaller particles. At Aksu and Dunhuang, the dust aerosol shows a higher δ13C value (average-0.148‰) and also a higher carbonate content (average 10.2%) compared with Yulin. The relative contributions of remote and local sources to Yunlin aerosol was estimated by a two component isotopic mixing equation using δ13C data. At XiAn, the aerosols collected during a dust storm had higher δ13C value than local fugitive dusts, indicating a significant contribution from long-range transport. Stable C isotopic composition provides a useful index for identifying putative sources for ambient dust aerosol, especially when used in combination with meteorological methods such as back trajectory analysis.