基于主成分分析的西南山区典型河道型水库富营养化评价讨论

Eutrophication Evaluation of Typical River Reservoirs in Southwest Mountainous Areas Based on Principal Component Analysis

为了解西南山区典型河道型水库的营养状态变化规律,并探究一种更为适合河道型水库、可靠的富营养化评价方法,以紫坪铺水库为例,基于2015年8月-2018年1月连续30个月对水库7个点位的跟踪监测,运用主成分分析法判别营养状态变化的主控因子及进行评价讨论,结果表明:①水库水体中藻类存在明显的演替规律,甲藻优势度下降14%,绿藻优势度上升26%;②通过主成分分析发现,水库中藻类、营养状态变化的主控因子为DO、NH3-H、TP和TN;③与常规的综合营养状态法相比,主成分分析法得出的评价结果更为可靠,与藻密度值、藻类皮娄指数的相关性各提高了0.338、0.279;④运用多元线性回归得到了水库藻类快速估算公式,通过6个月的实测值检验,公式误差可控制在45%以内。在更加全面准确、客观地反映水库营养状态上具有一定的研究意义。

To gain insight into the change law of nutrient status of typical channel reservoirs in the southwest mountainous area of China, and to look for a more resilient, reliable evaluation method for eutrophication in channel reservoirs, this paper adopts PCA(principal component analysis) in a way that helps identify key factors that restrict the change in nutrient status and evaluate and discuss the results on the basis of a case study in Zipingpu Reservoir in which 7 locations of the reservoir are subject to tracking and monitoring for 30 months from August 2015 to January 2018. The results indicate that, ①The algae in the water of Reservoir clearly features evolutionary changes 14% decline in the dominance of dinoflagellate means 26% rise in the dominance of chlorophyta. ②PCA finds that the main restricting factors related to the changes of algae and nutrient status turn out to be DO, NH3-H, TP, TN. ③Compared with the conventional method focusing on the comprehensive trophic status, PCA is able to deliver a more reliable evaluation result marked by an increase in 0.338 in the correlation with algae density and an increase in 0.279 in the evenness index of algae. ④A formula of flash estimation for algae in the reservoir is developed by using multivariate linear regression, with errors in the formula being controlled within 45% through a 6-month test on measured value. In this case, the paper bears certain research significance to reflecting the nutrient status of reservoir in a more comprehensive, accurate and objective way.