基于自组织映射与哈斯图方法的地表水水质评价研究

地表水水质评价是水资源管理与保护中的非常重要的问题.本研究主要目的是应用自组织映射(Self-Organizing Map,SOM)与哈斯图方法(Hasse Diagram Technique,HDT)对地表水水质监测数据集进行分类、建模、解释与评估.以西苕溪流域为例,对其50个断面于2010年6月-2011年5月进行月频率的水质监测.应用SOM分析发现,水质参数可分成10个聚类组,反映了西苕溪流域水质丰、平与枯水期特征,pH、高锰酸盐指数(CODMn)在各个水期变化不大；溶解氧(DO)在枯水期与平水期相对较高,水质具有一定的自净能力；丰水期的氨氮(NH4+-N)、总氮(TN)与总磷(TP)值相对较小；西苕溪流域TN:TP(氮磷质量比)平均为46,监测期间变幅较大为2～482,监测期内有66.7％的水质样本处于磷限制状态,仅有3.2％处于氮限制状态,存在氮限制与磷限制交替出现的状态,表明流域总体处于磷限制状态.选取CODMn、NH4+-N、TN 与TP指标进行HDT综合分析,反映流域上游水质较好,中、下游水质相对较差；敏感性分析结果表明,CODMn敏感性数值最大为235,其次是TN为156,、NH4+-N与TP分别是61与34,表明西苕溪流域的CODMn、TN存在较大的环境风险.建议在西苕溪流域即将开展的环境整治与规划时应考虑开发相关的削减技术与制定相关措施政策以减少CODMn、TN污染.

Assessment of surface water quality using self-organizing map and Hasse diagram technique

Surface water quality is a very important environmental issue for the management and protection of water resources. The primary purpose of this study was to apply self-organizing map (SOM) and Hasse Diagram Technique (HDT) to classify, model, interpret and evaluate the monitoring data for surface water quality. During the period between June 2010 and May 2011, 600 monthly samples were collected from 50 sites in West Tiaoxi River Basin, China. Based on SOM analysis, all the samples were divided into 10 clusters which were related with the water quality status of wet, flat, and dry seasons in the area. pH and COD_Mn had little change during the period. DO showed relatively high values in the dry season, indicating that the water had a certain degree of self-purification capacity. The values of NH₄⁺-N, TN and TP were relatively small in wet season. The average of TN:TP (mass ratio) in West Tiaoxi River Basin was 46, with a range from 2 to 482 during monitoring period. About 66.7% of water samples were in the state of the phosphorus limitation, with only 3.2% in nitrogen limitation status in the period, indicating the occurrence and alternation of phosphorus limitation and nitrogen limitation states. The entire watershed generally appeared to be in phosphorus limitation state. By selecting COD_Mn, NH₄⁺-N, TN and TP for HDT comprehensive analysis, 50 monitoring sites in West Tiaoxi River Basin were divided into eight levels. Water quality in the upstream was better, but relatively poor in midstream and downstream. Sensitivity analysis showed that COD_Mn had the highest sensitivity value (235), followed by TN (156), NH₄⁺-N (61), and TP (34), indicating that among the selected surface water quality indicators, COD_Mn and TN were the two important parameters with high environmental risk. Based on these results, we suggested to consider developing techniques and relevant policies to reduce the pollution of COD_Mn and TN in the basin.