南沙红树林湿地公园水环境质量时空差异分析——基于改进后倍斜率聚类分析的视角

Time and Space Differences of Water Environmental Quality of the Mangrove Wetland Park in Nansha:Based on the Improved Twice-slope Clustering Method

于2007年和2014年的丰水期和枯水期分别测量了南沙红树林湿地公园一期、二期及其附近河涌8个采样点的水体温度、pH、DO、COD、BOD5、TP和TN等物化指标。通过对比监测结果和倍斜率聚类评价结果发现：研究区水质总体上处于Ⅱ级-Ⅲ级或Ⅱ级-Ⅳ级的＂尚清洁＂状态;红树林湿地公园一期2008年对外开放后至2014年,水环境指标中pH变化范围不大,DO、COD含量有所下降,BOD5、TP和TN含量均呈增加趋势;2007年南沙红树林湿地公园一期采样点W1、W2、W3水质优于河涌采样点W7和W8,河涌采样点W7和W8水质优于红树林湿地公园二期采样点W4、W5、W6;2014年南沙红树林湿地公园二期采样点W4、W5、W6水质优于红树林湿地公园一期采样点W1、W2、W3和河涌采样点W7、W8;8个采样点中水质改善最明显的是二期采样点W6,水质下降最明显的是一期采样点W3;丰水期河涌水质2014年较2007年有所好转,但红树林湿地公园水质无论枯水期亦或丰水期,多数情况下优于河涌水质;研究区域水环境质量的时空差异总规律为2007-2014年南沙红树林湿地公园二期水质好转,一期水质有所下降。

This study constructs the wider twice-slope clustering membership functions of the clustering index — dissolved oxygen（DO）, based on the nondimensionalization of the monitoring results of water environment and the pollution classification standard. The physical chemistry indexes（e.g., temperature, pH, DO,COD, BOD5, TP and TN） of eight sampling sites were measured in the Nansha Mangrove Wetland Park Ⅰ, Ⅱand the brook nearby at the abundant, medium and dry seasons in 2007 and 2014. The comparison of the monitoring and evaluation results of the eight sampling points in 2007 and 2014 shows the following findings： on the whole, the water quality in the study area is in the health or sub-health state（level Ⅱ-Ⅲ or level Ⅱ-Ⅳ）.Since its opening to outside as a tourist scenic spot, the Mangrove Wetland Park Ⅰ has shown some changes in the indexes of water environment in 2008-2014. The monitoring results demonstrate that the change in pH is very small. At the same time, the DO has decreased, while the BOD5 has increased. A decrease is also observed in the COD content, by contrast, the TP and TN contents have shown a trend of increase. In 2007, the water quality of the sampling points W1, W2 and W3 in the Nansha Mangrove Wetland Park Ⅰ was better than that of the sampling points W7 and W8 in the brook. The water quality of the sampling points W7 and W8 in the brook was better than that of the sampling points W4, W5 and W6 in the Nansha Mangrove Wetland Park Ⅱ.In 2014, the water quality of the sampling points W4, W5 and W6 showed a dramatic improvement and was better than that of the sampling points W1, W2 and W3 in the Nansha Mangrove Wetland Park Ⅰ and the sampling points W7 and W8 in the brook. Among the eight sampling sites, W6 in the Nansha Mangrove Wetland Park Ⅱ showed the greatest improvement, while the sampling point W3 in the Nansha Mangrove Wetland Park Ⅰ observed the greatest declining in water quality. Although the water quality of the brook was improved at abundant season in 2014, the water quality of the Mangrove Wetland Park, at either abundant or dry seasons,is at least not less than and in most cases superior to the water quality of the brook. The general rule of the time and space differences of the water environmental quality in the study area is that the water quality of the Mangrove Wetland Park Ⅱ has been improved, while that of the Mangrove Wetland Park Ⅰ shows declining a trend in 2007-2014.