基于Monte Carlo方法的释光测年剂量率误差估计

Determining the error of dose rate estimates on luminescence dating using Monte Carlo approach

在释光年代学上,剂量率代表样品埋藏过程中单位时间内吸收的辐射剂量,其估计直接影响到埋藏年代的可靠性。误差传递公式(Quadratic propagation of uncertainty)常用于剂量率误差估计。由于计算剂量率涉及到众多参数复杂的非线性运算,造成基于误差传递公式的误差估计过程繁琐复杂。本文以粗颗粒石英矿物为例介绍了剂量率计算过程及误差估计方法,使用蒙特卡罗误差传递法(Monte Carlo error propagation)模拟了剂量率计算过程中多参数不确定性耦合误差,编写了执行随机剂量率模拟运算的开源R程序,并通过实测数据展示了该技术的应用。相对于应用误差传递公式法估计剂量率误差,Monte Carlo方法具有直观灵活、简便科学的特点,这种随机策略在分析科学领域具有广泛的适用性。

Background： In luminescence dating, dose rate is the irradiation dose a sample absorbed per unit time. The estimation of a dose rate affects the reliability of the burial age. Quadratic Propagation of Uncertainty （QPU） is routinely used to assess the standard error of a dose rate estimate. However, dose rate calculation involves lots of non-linear transformations between various parameters. This complicates the application of QPU method in dose rate error estimation. Purpose： In the current study, a detailed introduction to the calculation of the annual dose rate in case of coarse quartz sediments is given. A Monte Carlo technique （a ＂parametric bootstrap＂ method） is employed to simulate the propagation of uncertainty in dose rate calculation. Methods： An open source R program used for performing the simulation is developed. A practical application of this technique is illustrated using a measured data set. Results ＆ Conclusion： The Monte Carlo method is more flexible and simple in comparison with the QPU approach in dose rate error assessment. The stochastic scheme described in this article can be applied to any field of the analytical sciences.