Eutrophication of Nakdong River and Statistical Analysis of Environmental Factors

doi:2002.17.2.105

Algae > Volume 17(2); 2002 > Article

Algae 2002;17(2): 105-115. doi: https://doi.org/10.4490/ALGAE.2002.17.2.105

Mi Suk Kim, Young Ryun Chung, Euy Hoon Suh, Won Sup Song

Masan Chilseo Office of Waterworks, Department of Microbiology, Environmental Protection & Division of Applied Life Science (BK 21) Graduate school Gyeongsang National University, Department of Statistics, Division of Natural Science, Gyeongsang National University

ABSTRACT

Influences of various environmental factors on the eutrophication of Nakdong River were analyzed statistically using water samples collected from 1 January, 1999 to 30 September, 2001 at Namji area. The relationships between the concentration of chlorophyll a (eutrophication index) and environmental factors and were analyzed to develop a statistical model which can predict the status of eutrophication. The concentration of chlorophyll a ranged from 66.2 ㎎?m-3 to 70.8 ㎎?m-3 during dry winter season and the average concentration during this study period was 35.5 ㎎?m-3. Namji area of Nakdong River was in the hypereutrophic stage in terms of water quality. Stephanodiscus sp. and Aulacoseira granulata var. angustissima were dominant species during the winter to spring time and summer to autumn period, respectively. Based on the correlation analysis and the analysis of variance between chlorophyll a concentration and environmental factors, significantly high positive relationships were found in the order of BOD > pH > COD > KMnO₄ consumption > DO > conductivity > alkalinity. In contrast to these factors, significantly negative relationships were found as in the order of PO₄3--P > water level > the rate of Namgang-dam discharge > NH₃-N > the rate of Andong-dam discharge > the rate of Hapchoen-dam discharge. Based on the factors analysis of environmental factors on the concentration of chlorophyll a, we obtained five factors as follows. The first factor included water level, pH, turbidity, conductivity, alkalinity and the rate of Namgang-dam discharge. The second factor included water temperature, DO, NH₄+-N, NO₃--N. The third factor included KMnO₄ consumption, COD and BOD. The fourth factor included the rate of Andong-dam discharge, the rate of Hapcheon-dam discharge, and the rate of Imha-dam discharge. The final factor included T-N, T-P and PO₄3--P concentration. We derived two statistical models that can predict the occurrence of eutrophication based on the factors by factor analysis, using regression analysis. The first model is the stepwise regression model whose independent variables are the factors produced by factor analysis : chl a (㎎?m-3) = 42.923+(18.637 factor 3)+(-17.147 factor 1)+(-12.095 factor 5)+(-4.828 factor 4). The second model is the alternative stepwise regression model whose independent variables are the sums of the standardized main component variables : chl a (㎎?m-3) = 37.295 + (7.326 Zfactor 3) + (-2.704 Zfactor 1) + (-2.341 Zfactor 5).

Key words: algae, eutrophication, statistical analysis of factors, statistical model development