枯水期鄱阳湖及其滨湖水体氮磷等污染物分布与藻华风险研究

Study on Distribution of N and P Pollutants and Risk of Cyanobacteria Bloom in Poyang Lake and Waters around the Lake during Drought Periods

在以往研究重点关注鄱阳湖主湖区水生态环境基础上,在枯水期对鄱阳湖及其滨湖水体等鄱阳湖邻近污染汇湖网络进行了氮磷等主要营养物质及浮游植物调查,并从全局角度对结果进行了主成分分析评价和藻华成因Pearson相关分析,为系统全面评估鄱阳湖整体水环境污染状况及藻华风险预警提供科学依据。得出主要结论如下:枯水期鄱阳湖及周边水体的营养盐浓度普遍偏高,如藻华关键指标因子总磷主湖区平均达到0.22 mg·L-1,"五河"平均为0.12 mg·L-1,鄱阳湖主湖区营养盐浓度如总氮和总磷总体呈现南高北低分布,如总磷南部平均0.29 mg·L-1,北部0.14 mg·L-1,可能主要受南部受污染较重的入湖支流赣江和饶河污染输入影响。主成分分析结果表明,枯水期湖泊型水体水质主要受总磷、总氮、温度及p H影响,上述指标值越高,主成分分析的水质评价结果越差;河流型水体则主要受总氮、氨氮、温度、p H和透明度影响。滨湖湖泊中柘林湖水质良好,对修河和鄱阳湖水质起较好的促进作用,入湖河流的中小河流如博阳河水质较"五河"水质好,"五河"中赣江和饶河污染尤为严重。枯水期鄱阳湖和艾溪湖均发生了蓝藻水华,微囊藻是鄱阳湖蓝藻水华的绝对优势种。对鄱阳湖蓝藻水华区水体毒素分析表明,其水体溶解性微囊藻毒素浓度达到了1.60μg·L-1,其中MC-RR占蓝藻毒素总量的92.6%,MC-LR占5.2%,MC-YR占0.8%,其它类型毒素异构体约占1.4%,总体毒害风险尚不高。对数据进行相关分析表明,秋季高温气候、湖区高浓度的氮和有机物污染可能是该区域湖泊藻类增殖和水华暴发的主要成因。

The water quality and phytoplankton in Poyang Lake and waters around the lake, which including fiver major rivers in Jiangxi, were investigated during drought periods were investigated. Data were analyzed systematically with principal component analysis and Pearson's correlation. The results demonstrated that nutrient content such as TN and TP in the water was high in both Poyang Lake and waters around it. Average TP in Poyang Lake and five major rivers reached 0.22 and 0.12 mg·L-1 respectively. TN and TP in the south region of Poyang Lake was higher than in the north due to mainly polluted inflow from Ganjiang River and Rao River. Average TP in the south region was 0.29 mg·L-1 and was only 0.14 mg·L-1 in the north. The results of principal component analysis demonstrated that water quality in the lakes was mainly affected by TP, TN, temperature and pH. And water quality of inflowing rivers was mainly affected by TN, NH3-N, temperature, pH and water clarity. The water quality of Zhelin Lake was the finest of all the lakes and it has the function of purifying the water of Xiu River water before it went into Poyang Lake. Water quality in small rivers was much better than the five major rivers especially the heavily polluted Ganjiang River and Rao River. Cyannobacteria bloom broke out in both Aixi Lake in Nanchang and Poyang Lake during the dry season, and the dominant species in the bloom of Poyang Lake was Microcystis. The microcystins concentration in the blooming waters of Poyang Lake reached 1.60μg·L-1, including MC-RR (92.6%), MC-LR (5.2%), MC-YR (0.4%) and other mirocystin variant (1.4%), indicating a relatively low cyanobacterial toxin risk. The high temperature of autumn, high TN and COD content were probably the main cause of the cyanobacteria bloom.