Estimation of errors in the inverse modeling of accidental release of atmospheric pollutant: Application to the reconstruction of the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant
Estimation of errors in the inverse modeling of accidental release of atmospheric pollutant: Application to the reconstruction of the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant
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DOI：
10.1029/2011jd016932
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发表时间：
2012-03-09
影响因子：
4.4
通讯作者：
Mathieu, Anne
中科院分区：
文献类型：
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作者：
Winiarek, Victor;Bocquet, Marc;Mathieu, Anne
反演大气示踪剂扩散问题的源项时的一个主要困难是先验误差的估计：大气输运模型的误差，归因于测量结果的代表性的误差，仪器误差，以及试图检索的变量的先验知识的误差。在污染物意外释放的情况下，重建的源对这些假设是敏感的。这种敏感性使得检索的质量取决于用于建模和估计逆建模方案的先验误差的方法。提出了一种基于最大似然原理的误差幅度估计方法。在半高斯假设下，它考虑到，没有近似，积极的假设源。我们将该方法应用于使用空气中的放射性浓度来估计福岛第一核电站源项。的结果进行比较的L-曲线估计技术和Desrozier的计划。总的重建活动在很大程度上取决于所选择的方法。由于福岛第一核电站排放物的可观测性较差，这些方法提供了铯-137和碘-131重建放射性的下限。这些下限估计值，铯-137为1.2 × 10（16）Bq，估计标准偏差范围为15%-20%，碘-131为1.9 - 3.8 × 10（17）Bq，估计标准偏差范围为5%-10%，与日本核工业安全局提供的数据数量级相同，比切尔诺贝利大气释放量低5至10倍。
A major difficulty when inverting the source term of an atmospheric tracer dispersion problem is the estimation of the prior errors: those of the atmospheric transport model, those ascribed to the representativity of the measurements, those that are instrumental, and those attached to the prior knowledge on the variables one seeks to retrieve. In the case of an accidental release of pollutant, the reconstructed source is sensitive to these assumptions. This sensitivity makes the quality of the retrieval dependent on the methods used to model and estimate the prior errors of the inverse modeling scheme. We propose to use an estimation method for the errors' amplitude based on the maximum likelihood principle. Under semi-Gaussian assumptions, it takes into account, without approximation, the positivity assumption on the source. We apply the method to the estimation of the Fukushima Daiichi source term using activity concentrations in the air. The results are compared to an L-curve estimation technique and to Desroziers's scheme. The total reconstructed activities significantly depend on the chosen method. Because of the poor observability of the Fukushima Daiichi emissions, these methods provide lower bounds for cesium-137 and iodine-131 reconstructed activities. These lower bound estimates, 1.2 x 10(16) Bq for cesium-137, with an estimated standard deviation range of 15%-20%, and 1.9 - 3.8 x 10(17) Bq for iodine-131, with an estimated standard deviation range of 5%-10%, are of the same order of magnitude as those provided by the Japanese Nuclear and Industrial Safety Agency and about 5 to 10 times less than the Chernobyl atmospheric releases.