一种获取地区大气降水线方程(LMWL)的简单方法——以北京平原为例

A Simple Method of Obtaining Local Meteoric Water Line(LMWL) Equation: A Case Study in Beijing Plain

地区大气降水线(LMWL)是进行区域水循环研究的基准。受监测站点数量的限制,大多数地区无法获得,只能参考最近监测站点的降水线或全球大气降水线(GMWL),或者需要较长时间的监测后才能获得。传统的获取方法存在较多的限制。本研究以北京平原区为例,提出了一种获取地区大气降水线(LMWL)的新方法:通过对不同深度的第四系地下水进行取样测试获取同位素数据,然后拟合获得。通过与传统方法所得的本区大气降水线对比,表明本次所得方程的相关系数更大,标准误差小,样本量大,拟合效果更好。同时可以节约大量的监测时间与人力物力,且可获得长时间序列的历史数据,较为简单实用。该方法也存在一定的局限,要求取样时尽量选取颗粒细小的冲积平原地带。

The local meteoric water line （LMWL） is a significant benchmark in regional water cycle research. Because of the limited numbers of monitoring stations, most sites cannot obtain the LMWL easily, and could only refer the LMWL of the nearest monitoring station or the Global Meteoric Water Line （GMWL）, or there needs a long term monitoring before analyzing and obtaining. There also exist many limitations in the conventional methods to obtain the LMWL. A case study was carried out in the Beijing Plain, and a new simple method of obtaining the LMWL was proposed in this paper. The data of the 8D and 818O of historical periods can be got through quaternary groundwater sampling and analysis, and the LMWL was obtained with the data directly. Compared with the LMWL equations using the conventional method, the new method is shown to have many advantages. The method could save a lot of human and physical resources and monitoring time, is relatively simple and is more practical. Moreover, it has a better fitting effect. It is also noted that the method has some deficiencies： it requires the sampling sites to be selected from an alluvial plain area with fine deposition particles.