基于210Pb和137Cs计年法的黄河下游湿地沉积速率研究初探

本文利用²¹⁰Pb和¹³⁷Cs计年方法分析探讨黄河下游湿地沉积速率演化与上游水沙变化的响应关系。结果表明,²¹⁰Pb比活度大致指数衰减趋势以及¹³⁷Cs蓄积峰的鉴出,表明放射性核素手段在黄河下游湿地的沉积学研究具有一定可行性。基于²¹⁰Pb的CIC模式和CRS模式得出的沉积速率分别为1.68 cm/a和0.67~2.76 cm/a;基于¹³⁷Cs剖面的1963年和1986年两个蓄积峰,计算自下而上沉积速率分别为2.67 cm/a、1.08 cm/a和1.21 cm/a。研究发现,近几十年黄河下游湿地沉积速率呈逐渐减小趋势,这与黄河流域气候变化、上游流域建坝、水土保持和下游水资源利用存在密切关系。此外,水库调度方式也在一定程度上影响下游沉积速率,虽然下游淤积量不变,但洪峰的"削平"导致泥沙难以淤积于湿地。

Preliminary Study on the Sedimentation Rate of Wetlands in the Lower Yellow River Based on the 210Pb and 137Cs Dating Techniques

This paper calculates the sedimentation rate of the alluvial wetlands in the lower Yellow River based on the ²¹⁰Pb and ¹³⁷Cs dating techniques and analyzes the relationship between the evolution of sedimentation rate and the change of water and sand in the upstream river. Results showed an exponential decrease trend of ²¹⁰Pb and the occurrence of two spikes of ¹³⁷Cs prove the feasibility of this radionuclide method. Sedimentation rates of 1.68 cm/a and 0.67-2.76 cm/a are calculated based on the CIC model and CRS model of ²¹⁰Pb, respectively; meanwhile, sedimentation rates of 2.67 cm/a, 1.08 cm/a and 1.21 cm/a are found for bottom, middle and upper sediments based on two spikes of ¹³⁷Cs fallout in 1963 and 1986. Furthermore, the sedimentation rate in the alluvial wetlands of the lower Yellow River decreased gradually in the past decades, this is closely correlated with the climate change, damming in the upstream, water and soil conservation project, and the downstream water utilization. In addition, the reservoir operation also affects the sedimentation rate to a certain degree. The dying flood make it harder for the sediment to deposit in the wetland.