Using Long-Lived Thorium Isotopes to Quantify the Lithogenic Inputs to the Lakes in Qaidam Basin, China

Abstract

In the last decade, the 232Th–230Th system has gained popularity as a tracer to quantify lithogenic sources of trace elements to the marine environment. Thorium (Th) isotopes were utilized to quantify the supply of lithogenic inputs to Keluke Lake and Tuosu Lake in Qaidam Basin, China. A total of 33 water samples were collected from Keluke Lake, Tuosu Lake, and Bayin River to measure the concentrations of dissolved 232Th and 230Th. The relationship of 232Th concentration in the water was in the order Bayin River > Keluke Lake > KLK–TS River > Tuosu Lake, confirming the input of variable lithogenic material sources. Three sources dominate the flux of lithofacies into the lakes: the river input, the deposition of dust and the local input from the sediments surrounding the lakes. On an interannual timescale, the lithogenic flux of Keluke Lake was mainly derived from river input. In summer, the dust flux in the study area could be estimated as 0.133 g/m2/year, while the flux of lithologic material from Bayin River to Keluke Lake was 12.367 g/m2/year. In contrast, the fluvial input to the Tuosu lake was small in comparison to the dust contribution of lithogenic flux. The high Th232-concentration and the vertical sediment flux in this lake may have been caused by resuspension of bottom sediments.