Contribution of Asian dust to soils in Southeast China estimated with Nd and Pb isotopic compositions

Abstract

Asian dust has been identified in subtropical soils of China. Neodymium (Nd) and lead (Pb) elemental and isotopic geochemistry of soils in Southeast China were used to assess the significance of local versus extraneous sources. The eNd(0) values were close to the parent rocks (+ 2.9) in the young soils (NSJ); while their values were always negative (~ − 3.7) in the old soils (OMJ), implying dust deposition. The young soils contained less Asian dust contribution (< 8 %) while the old soils contained more than 50 % Asian dust contribution. This implied that dust contributions were gradually increasing with the soil development stage and Asian dust input had become the principal Nd source for the old soils in this area. On the other hand, Pb excesses and low 207Pb/206Pb values (~ 0.8503) in near-surface soils indicated a significant anthropogenic Pb addition onto surface soils. The close relationship between the Pb content and isotopic ratios in the soil profile indicated that the excessive lead in the surface soil was exogenous. These results suggested that Asian dust made up a significant fraction in the old soils, but that local sources (i.e., basalt and anthropogenic) were not trivial in Southeast China.