Influences of environmental factors on the modern 14C reservoir effects in Qinghai-Tibet Plateau lakes

The establishment of reliable age in the lake sediment profile mainly depends on the AMS 14C dating technique. However, the presence of the 14C lake reservoir effects (LREs) restricted for using radiocarbon dating in lake sediment, especially in dry and cold areas with a scarce plant cover in the Qinghai-Tibet Plateau. Hence, the discussion of influence factors of LREs is crucial. This paper selected 15 lakes (17 sediment and 3 plant samples) in the Qinghai-Tibet Plateau to examine the distribution characteristics of the modern LREs and their main influencing factors. In our study area, 14 lakes were all affected by the LREs. The minimum 14C year is 5900 a BP towards the deep water area, whereas the maximum 14C year is up to 7185 a BP in the margins of Lake Heihai. The maximum 14C year is up to 7750 a BP, and the minimum 14C year is present-day carbon in the 15 lakes. One further study indicated that the LRE differences in individual lake are mostly owing to the contribution of exogenous carbonate. The results displayed that the LREs tended to increase with the increase of the salinity, moreover, the LREs of saltwater lakes or salt lakes were significantly larger than freshwater lakes due to the possible supply of old total dissolved inorganic carbon with a long residence time in the lakes. Moreover, the contribution of calcite played a significant role on the LREs. Additionally, the LREs differences are affected by the source of organic matter. The lake with groundwater supply shows large LRE due to likely being influenced by crustal and ancient CO2 uprising.