Studies on Lead Isotope Analysis and Composition in Soils and Near-surface Atmospheric Aerosols of the Ruoergai High Altitude Plateau, and Lead Sources Identification

The Ruoergai highland pasture is located in the remote, high altitude area of China. Atmospheric transport and precipitation is one of the major routes of pollutants to this area, but pollution source identification is difficult due to the monsoon. Atmospheric aerosol samples were taken in different seasons at multiple sites in Ruoergai. High precision Pb isotope analysis for soils and atmospheric aerosols was performed by using Thermal Ionization Mass Spectrometry (TIMS), which has the advantage of effectively removing the isotope fractionation effect in mass analysis. The sources of the aerosols were analyzed in association with the characteristics of the monsoon. The range of ²⁰⁸Pb/²⁰⁴Pb ratio is 38.79059±0.00194-38.94461±0.00135 and ²⁰⁶Pb/²⁰⁷Pb 1.18551±0.00002-1.19362±0.00002, ²⁰⁸Pb/²⁰⁴Pb in the atmo-spheric aerosol is 37.49571±0.00117-38.48980±0.00105 and ²⁰⁶Pb/²⁰⁷Pb 1.12894±0.00001-1.16734±0.00001. The Pb isotopic composition of soil in Ruoergai is characterized by high radiogenic Pb, mainly from local rock and minerals. The Pb isotopic composition of aerosols differs from that of soil, showing a multiple mode of mixing of natural and anthropogenic sources. Automobile exhaust gas and long-range atmospheric transport mainly from the north (Lanzou) and northwest (Qinghai, Xinjiang, Kazakhstan and Russia) are possible sources of aerosols and pollutants.