湖泊科学2009，Vol.21Issue(6)：827-833,7.
~(137)Cs质量平衡法测算青海湖现代沉积速率的尝试
An attempt to use the ~(137)Cs mass balance model for assessment of recent deposition rates in Lake Qinghai, China
摘要
Abstract
This paper was an attempt to use the ~(137)Cs mass balance model for assessment of recent deposition rates in Lake Qinghai. ~(137)Cs concentration peak at the depth of a few centimeters in the deposit profiles of Lake Qinghai and other lakes with lower deposition rates may be caused by the nuclide downward diffusion and migration progresses after the ~(137)Cs deposited on the surface of lake bottom mud. Therefore, the interpretation of the sediment layer at the ~(137)Cs peak depth depositing in 1963 and the calculation method of sediment deposition rates under that assumption may not be reasonable. Local ~(137)Cs reference inventory was 117.7mBq/cm~2 in 2005 obtained from grass land of the flat lakeside, ~(137)Cs inventories of the six lake sediment cores collected from the Island Hill of the center of Lake Qinghai to the Fish Port in the south-eastern lake ranged from 92.9mBq/cm~2to 325.0mBq/cm~2. It was clear that sediment deposition apparently occurred in the south-western part of the lake, particularly, the deposition is quite fast at the QHH02 Core position, which is located in the front of the underwater alluvial fan. However, sediment deposition was very slow at the centre part of the lake. The average ~(137)Cs concentration of the deposited sediments in Lake Qinghai since 1963 was estimated to be 30mBq/g by analyses of the ~(137)Cs concentrations from the lake mud in surface layers, the sediment discharged from inlet rivers, and the soil in surface layers on the grass land in the catchment. The average deposition rate in the centre of the lake was 0.020cm/a calculated by the ~(137)Cs mass balance model, which agreed to 0.018cm/a of the specific sediment yield of the Buha River, but much lower than the reported deposition rates estimated by conventional dating techniques. The deposition rate of the QHH02 Core was 0.229cm/a, suggesting that the deposition rates in the south-western part of the lake were much higher than the rates in the centre part of the lake and which was twice of the reported deposition rate of Lake Qinghai.关键词
现代沉积速率/~(137)Cs质量平衡法/青海湖Key words
Sediment deposition rate/~(137)Cs mass balance model/ Lake Qinghai分类
天文与地球科学引用本文复制引用
张信宝,曾奕,龙翼..~(137)Cs质量平衡法测算青海湖现代沉积速率的尝试[J].湖泊科学,2009,21(6):827-833,7.基金项目
国家自然科学基金项(40599420,40971169)资助. （40599420,40971169）
