National Administration "ApeleRomane", Edgar Quinet Street, Postal Code 010018, Bucharest, Romania,
Environ Monit Assess. 2013 Nov;185(11):9495-507. doi: 10.1007/s10661-013-3268-2. Epub 2013 May 31.
The concept of basin-wide Joint Danube Survey (JDS) was launched by the International Commission for the Protection of the Danube River (ICPDR) as a tool for investigative monitoring under the Water Framework Directive (WFD), with a frequency of 6 years. The first JDS was carried out in 2001 and its success in providing key information for characterisation of the Danube River Basin District as required by WFD lead to the organisation of the second JDS in 2007, which was the world's biggest river research expedition in that year. The present paper presents an approach for improving the survey strategy for the next planned survey JDS3 (2013) by means of several multivariate statistical techniques. In order to design the optimum structure in terms of parameters and sampling sites, principal component analysis (PCA), factor analysis (FA) and cluster analysis were applied on JDS2 data for 13 selected physico-chemical and one biological element measured in 78 sampling sites located on the main course of the Danube. Results from PCA/FA showed that most of the dataset variance (above 75%) was explained by five varifactors loaded with 8 out of 14 variables: physical (transparency and total suspended solids), relevant nutrients (N-nitrates and P-orthophosphates), feedback effects of primary production (pH, alkalinity and dissolved oxygen) and algal biomass. Taking into account the representation of the factor scores given by FA versus sampling sites and the major groups generated by the clustering procedure, the spatial network of the next survey could be carefully tailored, leading to a decreasing of sampling sites by more than 30%. The approach of target oriented sampling strategy based on the selected multivariate statistics can provide a strong reduction in dimensionality of the original data and corresponding costs as well, without any loss of information.
全流域联合多瑙河调查（JDS）的概念是由保护多瑙河国际委员会（ICPDR）作为在水框架指令（WFD）下进行调查监测的工具提出的，其频率为 6 年一次。第一次 JDS 于 2001 年进行，其成功地为 WFD 要求的多瑙河流域地区特征描述提供了关键信息，这导致了 2007 年第二次 JDS 的组织，这是当年世界上最大的河流研究考察。本文提出了一种通过几种多元统计技术改进下一次计划调查 JDS3（2013）调查策略的方法。为了设计出最佳的参数和采样点结构，在 78 个采样点上对 13 个选定的理化和一个生物元素进行了主成分分析（PCA）、因子分析（FA）和聚类分析，这些采样点位于多瑙河的干流上。PCA/FA 的结果表明，数据集的大部分方差（超过 75%）由五个变量因子解释，这些变量因子加载了 14 个变量中的 8 个：物理（透明度和总悬浮物）、相关养分（N-硝酸盐和 P-正磷酸盐）、初级生产的反馈效应（pH、碱度和溶解氧）和藻类生物量。考虑到 FA 与采样点的因子得分表示以及聚类过程生成的主要组，下一次调查的空间网络可以仔细调整，从而减少 30%以上的采样点。基于选定的多元统计的目标导向采样策略方法可以在不损失信息的情况下，大大降低原始数据的维数和相应的成本。
