Identifying the Influence of Water Chemistry on Chlorophyll a in Lake Dianchi: A Structural Equation Modeling Analysis

YAN Xiaopin1,LI Yuzhao1,LIU Yong 1*,YANG Yonghui1,ZHAO Lei 2, GUO Huaicheng1

(1.College of Environmental Science and Engineering, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Peking University, Beijing 100871; 2. Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake-Watershed, Kunming 650034)

Abstract: An integrated approach of absolute principle components score-multivariate linear regression (APCS-MLR) and structural equation modeling (SEM) were developed in this study to understand the influence of water chemistry variables on chlorophyll a (Chl a) in Lake Dianchi. The SEM result was further validated with the artificial neural networks (ANN) model. It proved that there was a good agreement on the results of the various models. The model results demonstrated that, among the water chemistry factors, physical factors (T> DO > SD >pH ) had the greatest influence on Chl a; whereas nutrients had little influence. In severely polluted water with chronically high nitrogen (N) and phosphorus (P) concentrations like Lake Dianchi, the change of nutrients concentrations will not significantly influence on Chl a, while the sensibility of N is higher than P. Therefore, nitrogen load reduction should be put in priority for eutrophication control in Lake Dianchi.

Keywords: Eutrophication; Structural Equation Modeling; Artificial Neural Networks; Chlorophyll a; Lake Dianchi