衢州地区渔业水域水库水体富营养化水平及驱动因子研究

为探求衢州市渔业水域水库水体富营养化水平和主要驱动因子,本研究基于2018年水质监测数据,综合评价黄坛口水库(S1)、铜山源水库(S2)、狮子口水库(S3)、花园垄水库(S4)和金仓垅水库(S5)5座不同水库水体富营养化水平,并采用相关性分析、主成分分析探讨水质环境因子对水体富营养化水平间的影响和相关关系。结果显示,叶绿素a(Chl-a)与综合营养状态指数法评价结果趋于一致,表明S1、S2和S3水库均为中营养,S4为轻度富营养,S5为重度富营养,水产养殖水域富营养化水平显著高于增殖放流水域(P<0.05)。5个水库中,S5为氮限制,其余水库均为磷限制。多元线性逐步回归分析表明,Chl-a与溶解氧(DO)、透明度(SD)、铜(Cu)、总磷(TP)、总氮(TN)、高锰酸盐指数(CODMn)的相关性较好,综合营养状态指数(TLI)与水温(T)、SD、Cu、TP、TN的相关性较好,得到模型:Chl-a=19.793 CODMn-32.065 TP-33.004,TLI=1.062 CODMn+18.468 TP-0.06 SD+0.450 T+1.765 TN+33.886。综合相关性分析、主成分分析结果,CODMn、TP、SD、T和TN是影响衢州市水库水体富营养化的主要因子,其中,氮、磷营养盐和有机物是造成水库水体富营养化的主要影响因子,水温是造成各水库富营养化季节性变化的主要原因,而pH、溶解氧是水体富营养化后的结果,可以作为水库富营养化水平的指示因子。

Research on eutrophication and its driving factors in reservoirs of the Quzhou area

In the Quzhou area,there are five important reservoirs:Huangtankou(S1),Tongshanyuan(S2),Shizikou(S3),Huayuanlong(S4),and Jincanglong(S5).To ascertain the eutrophication level and the main driving factors in reservoirs in the Quzhou area,we analyzed the water quality in 2018 to determine the relationship between eutrophication and environmental factors.The comprehensive trophic level index(TLI)method showed that reservoirs S1,S2,and S3 were mesotrophic,S4 was lightly eutrophic,and S5 was highly eutrophic,which concurred with the relative chlorophyll a(Chl-a)concentrations.To improve the comprehensive development and utilization of the reservoirs,industry,such as aquaculture,was developed in Quzhou.Results showed that eutrophication in aquacultural areas was significantly higher than that in breeding and releasing areas.Furthermore,we analyzed how water quality was affected by aquaculture using a cluster analysis.Results showed that effectively managed aquaculture may not be the main contributing factor for eutrophication.Based on the N/P ratio,we found nitrogen limitation occurred in S5,whereas phosphorous limitation occurred in the other reservoirs.Therefore,we should focus on controlling phosphorous and nitrogen.The regression equation among Chl-a,TLI,and the correlated environmental factors was expressed using multiple linear stepwise regression as follows:Chl-a=19.793 CODMn-32.065 TP-33.004,TLI=1.062 CODMn+18.468 TP-0.06 SD+0.450 T+1.765 TN+33.886,where TP,SD,T,and TN stand for total phosphorous,transparency,temperature,and total nitrogen respectively.Combined with a correlation and principal component analysis(PCA),it was concluded that CODMn,TP,SD,T,and TN were the main factors influencing reservoir eutrophication in the Quzhou area,among which nitrogen and phosphorous and organic compounds were the impact factors,and water temperature was the main cause of seasonal change.However,pH and DO were a consequence of eutrophication,and could be indicators of the eutrophication level.pH and DO increased with increasing eutrophication,but in highly eutrophic water,algal overgrowth can cause a rapid decrease in DO in the water.