茅洲河流域水环境治理工程的生态效应研究

评价水环境治理工程对流域水生态环境的影响,可为茅洲河流域进一步的生态修复工作提出建议。对水环境治理初期(2016年5月)和治理期间(2018年8月)茅洲河流域水生态状况进行调查,选取44个采样点,覆盖茅洲河流域的干流以及主要支流,以获取的样本和水质理化数据,对比分析水质、底栖动物群落、浮游藻类及大型水生植物群落变化。结果显示,治理期间茅洲河流域水体化学需氧量(COD)、氨氮(NH_3-N)和总磷(TP)平均浓度分别降低了41.2%、50.6%和66.7%,溶解氧(DO)平均浓度升高了130.8%;底栖动物群落物种多样性增加了53.6%,耐污种类的密度和优势度降低,并在部分样点新增敏感性较高的蜉蝣目、鞘翅目、毛翅目和半翅目水生昆虫类群。大型水生植物种类和分布范围明显增加,流域内分布有挺水植物24种、沉水植物4种、漂浮植物2种、浮叶植物1种。Palmer藻类污染指数指示为重污染的样点减少了56.3%,中污染样点增加了16.3%,轻污染的样点增加了40.0%。BMWP指数评价结果也有好转,最高得分为49。研究表明,治理后的茅洲河流域水污染程度降低,生态环境状况总体有所好转,但流域生态健康状况仍然较差,需进一步开展系统的流域生态修复工作。

Ecological Effectiveness of the Water Management Project in Maozhou River Basin

The Maozhou River basin, located in northwest Shenzhen City, has a dense river network. A comprehensive water environment management project has been underway in Maozhou River basin since February, 2016 and ecological surveys of the basin were conducted at an early stage (May 26-31, 2016) and after about 2.5 years of operation (August 8-13, 2018). In this study, the ecological effects of the project were evaluated by comparing the results of the two surveys (water quality and the macroinvertebrate, phytoplankton and macrophyte communities) and suggestions were made to guide further ecological restoration. The ecological surveys involved 44 sampling sites, covering the Maozhou River main stem and primary tributaries. Compared with 2016, the average basin concentrations of COD, ammonia nitrogen (NH3-N) and total phosphorus (TP) in 2018 had decreased, respectively, by 41.2%, 50.6% and 66.7%, and the average concentration of dissolved oxygen (DO) had increased by 130.8%. In 2018, a total of 43 macroinvertebrate species were collected (28 insect species and 15 non-insect species), compared with a total of 28 macroinvertebrate species in 2016, an increase in species richness of 53.6%. The density and dominance of pollution-tolerant species decreased and several sensitive taxa of aquatic insects (Ephemeroptera, Coleoptera, Trichoptera and Hemiptera) were found at some sampling sites. Both the species richness and range of aquatic macrophyte increased significantly. A total of 24 emergent plant species, 4 submerged plant species, 2 floating plant species and 1 species of floating leaf plant were recorded in August 2018. Phytoplankton density decreased in 2018, with an average density of 4.6×106 ind/L, and a dramatic decrease in Chlorophyta and Cyanophyta, and an increase in Bacillariophyta and Euglenophyta. The number of highly polluted sites indicated by the Palmer index decreased by 56.3%, while moderately polluted and slightly polluted sites increased by 16.3% and 40.0%, respectively. The Biological Monitoring Working Party (BMWP) score was 49, indicating improved ecological health. Our results indicate that Maozhou River pollution decreased and ecological health improved. Nevertheless, the health of Maozhou River is still poor and systematic ecological restoration in the basin should continue.