基于多元统计分析方法的西苕溪流域水质时空变化研究

基于太湖上游西苕溪流域38个采样点2009年6月至2010年7月完整周年的水质监测数据,综合运用聚类分析、单因素方差分析、因子分析及多维尺度分析等多元统计分析方法,对西苕溪流域水质时间与空间变化进行了分析。根据聚类分析将整个流域河段在空间上分为四个部分,即上游林区的河段、紧邻城镇的下游河段、下游平原区的干流河段和分散于农业灌溉区的河段;利用因子分析的旋转因子载荷矩阵从时间维度研究不同水质参数的季节敏感性,氮素在整个研究时间段与旋转因子的相关系数都大于0.900,表现出整个研究时间段内的敏感性;利用单因素方差分析和多维尺度分析实现时空的统一分析,相同时间不同河段间差异性显著且都与其地理位置特点相吻合,所有河段在时间维度上均显现出丰水期的水质与另两个水期差异显著的特点,紧邻城镇的下游河段水质是整个流域中不同水期间差异性最小的,凸显了人为干扰的持续性。研究结果表明,运用多元统计方法对西苕溪流域水质的时空变化特点进行分析,可以为流域水质监测与污染防控提供有益参考。

Analysis of Temporal and Spatial Variations in Water Quality of Xitiaoxi Watershed Using Multivariate Statistical Techniques

In this study, water quality data from June 2009 to July 2010 at 38 sampling sites in Xitiaoxi watershed, a branch of Taihu Lake in China, were obtained. Multivariate statistical techniques, including cluster analysis, one-way analysis of variance(ANOVA), factor analysis and multidimensional scaling analysis, were employed for the evaluation of spatial and temporal variations in water quality in Xitiaoxi watershed. Based on the similarity of water quality characteristics, the watershed was classified into four sections:upstream forest, downstream city, downstream plain and downstream agricultural irrigation sections. Rotated factor correlation coefficients rendered good results of the seasonal sensitivity of different water quality parameters. The correlation coefficients between nitrogen concentration and rotated factors during the entire study period was greater than 0.900, showing its time sensitivity in the whole study period. One-way ANOVA analysis and multidimensional scaling analysis obtained the best results for both spatial and temporal variations. Overall, the spatial variation in water quality was significant and consistent with the geographical characteristics. Water quality in all channels showed little difference between mean- and low-flow periods, but had significant difference between the high-flow and other two periods. The main channel at city area displayed the minimal temporal variation in the entire watershed, indicating the anthropogenic interference. These results provide critical information for management of water resources in Xitiaoxi watershed.