Further quantifying the fluxes and contributions of sources to modern sediment in Lake Qinghai, NE Tibetan Plateau

Faithfully tracing sources of sediment and then quantifying the flux of each source are the first-order basis for reconstructing paleoclimate and paleoenvironment using lake sediments. The budget of various sources contributing to lake sediment in Lake Qinghai, the largest lake on the Tibetan Plateau, is controversial. In the previous study, the flux of the dust deposition to the modern lake sediment was obtained through 2-year observations, but estimations of other sources have some uncertainties due to inadequate data. In this study our new estimations for the modern Lake Qinghai sediment using new measured data show (1) that contribution (22.1 +/- A 5.2 %) of the fluvial particulate matter is of second significance, only about one-third of the dust deposition, to the modern lake sediment, when its quick deposition near river mouths is not considered, (2) that lacustrine organisms contribute only 5.2 +/- A 1.1 % of the sediment, but account for similar to 70 % of the organic matter in sediment, and (3) that authigenic carbonates contribute 21.0 +/- A 8.6 % of the sediment and 63.6 % of the total carbonates in the lake sediment, respectively, which is due to a direct precipitation of both Ca2+ and Mg2+ in the modern Ca2+-limited lake. These quantifications are instructive to understand the particulate fluxes to sediment pools in Lake Qinghai under the present conditions and to reconstruct paleoclimate and paleoenvironment via physical and geochemical proxies using past sediments.