Yenilmez Firdes, Düzgün Sebnem, Aksoy Aysegül
Department of Environmental Engineering, Middle East Technical University, 06800, Ankara, Turkey.
Environ Monit Assess. 2015 Jan;187(1):4216. doi: 10.1007/s10661-014-4216-5. Epub 2014 Dec 20.
In this study, kernel density estimation (KDE) was coupled with ordinary two-dimensional kriging (OK) to reduce the number of sampling locations in measurement and kriging of dissolved oxygen (DO) concentrations in Porsuk Dam Reservoir (PDR). Conservation of the spatial correlation structure in the DO distribution was a target. KDE was used as a tool to aid in identification of the sampling locations that would be removed from the sampling network in order to decrease the total number of samples. Accordingly, several networks were generated in which sampling locations were reduced from 65 to 10 in increments of 4 or 5 points at a time based on kernel density maps. DO variograms were constructed, and DO values in PDR were kriged. Performance of the networks in DO estimations were evaluated through various error metrics, standard error maps (SEM), and whether the spatial correlation structure was conserved or not. Results indicated that smaller number of sampling points resulted in loss of information in regard to spatial correlation structure in DO. The minimum representative sampling points for PDR was 35. Efficacy of the sampling location selection method was tested against the networks generated by experts. It was shown that the evaluation approach proposed in this study provided a better sampling network design in which the spatial correlation structure of DO was sustained for kriging.
在本研究中，核密度估计（KDE）与普通二维克里金法（OK）相结合，以减少在布尔苏克大坝水库（PDR）溶解氧（DO）浓度测量和克里金法中采样点的数量。目标是保持DO分布中的空间相关结构。KDE被用作一种工具，以帮助识别将从采样网络中移除的采样点，从而减少样本总数。因此，基于核密度图，生成了几个网络，其中采样点每次以4或5个点的增量从65个减少到10个。构建了DO变异函数，并对PDR中的DO值进行了克里金插值。通过各种误差指标、标准误差图（SEM）以及空间相关结构是否得以保持，对这些网络在DO估计中的性能进行了评估。结果表明，较少的采样点会导致DO空间相关结构信息的丢失。PDR的最小代表性采样点数为35个。针对专家生成的网络，测试了采样点选择方法的有效性。结果表明，本研究中提出的评估方法提供了一种更好的采样网络设计，其中DO的空间相关结构在克里金插值中得以维持。
