Identification and quantification of physicochemical parameters influencing chlorophyll-a concentrations through combined principal component analysis and factor analysis: A case study of the Yuqiao Reservoir in China

Abstract

Algal outbreaks caused by excessive nutrients in lakes result in eutrophication. Chlorophyll-a, as a primary productivity feature, is used as a representative index of algal presence in lakes. Physicochemical parameters are known to affect the type and amount of nutrients in lakes, which are related to eutrophication. In this study, factor analysis was used in conjunction with principal component analysis to reveal the relationship between chlorophyll-a and its associated parameters. The combination of these two methods helps to identify the main influencing parameters by quantifying the respective extent of parameters using FA, after which the meaning is explained by PCA. We investigate physicochemical parameters, including temperature, dissolved oxygen (DO), pH, suspended solids, chemical oxygen demand (COD) and five-day biochemical oxygen demand, as well as nutrients, such as ammonium, nitrite, nitrate, total nitrogen, and total phosphorus (TP). Yuqiao Reservoir, an important drinking water source in northern China, has been affected by eutrophication for years. Analysis was performed using daily monitoring data of physicochemical parameters and chlorophyll-a concentrations collected from Yuqiao Reservoir between 2003 and 2014. Results show that main parameters affecting chl-a concentrations are TP, temperature, DO, COD, and nitrogen, with correlation coefficients of 0.977, 1.983, 1.797, and 1.595, respectively.