珠江中下游表层水体CODMn时空分布特征及水环境评价

为了从常用的水质评价方法中筛选出适合珠三角河网的方法，该研究对2015年珠三角河网的水环境因子和浮游植物数据进行了初步的评价分析。运用自组织映射模型 (SOM) 从6种浮游植物评价指数中筛选出香农指数、均匀度指数、丰富度指数和生物量指数4种相似性高的指数，将上述指数和环境因子的水质评价结果进行对比分析。结果显示，基于溶解氧和氨氮的水质评价结果可以较好地反映城市周边与其他区域的空间差异，而总氮和总磷不适用于研究水域的水质等级评价；基于香农指数和生物量指数的水质评价结果可以较好地反映出城市周边与其他区域的差异，均匀度指数和丰富度指数不适用于研究水域的水质等级评价。除总氮、总磷外，其他环境因子和4种浮游植物指数的评价结果均反映为研究水域水质整体良好，城市周边站位水质略差。研究表明，溶解氧、氨氮、香农指数、生物量指数是适合研究水域水质等级评价的环境因子和浮游植物评价指数。

Spatio-temporal patterns and predictions of phytoplankton assemblages in a subtropical river delta system

In order to select asuitable method for water quality evaluation in the Pearl River Delta (PRD), we accessed and analyzed the water environment factors and phytoplankton data in PRD in 2015. Four phytoplankton indices, including Shannon index, evenness index, richness index and biomass index, were selected from six common phytoplankton indices based on similarities by using self-organizing map (SOM). Then, we compared the water quality evaluation results of the above indices and environmental factors. The results based on dissolved oxygen and ammonia nitrogen could reflect the spatial differences between city centers and other regions, but total nitrogen and total phosphorus were not suitable for water quality evaluation. However, the results based on Shannon and biomass indices could reflect the differences between city centers and other regions, but evenness and richness indices were not suitable for water quality evaluation. Except for total nitrogen and total phosphorus, the evaluation results of other environmental factors and four phytoplankton indices show that the water quality of the survey area was generally good, but the water quality of stations around the city was slightly poor. Thus, issolved oxygen, ammonia nitrogen, Shannon index and biomass index are suitable environmental factors and phytoplankton index for water quality evaluation.