A COMPARATIVE ASSESSMENT ON SPATIO-TEMPORAL VARIATIONS IN WATER ENVIRONMENT QUALITY OF CHAOHU LAKE (CHINA) BY USING DIFFERENT MODELS

In this study, two pollution index methods (single-factor and comprehensive index models) and two fuzzy mathematical methods (single-factor deciding and weighted-average models) were used to investigate water environment quality of Chaohu Lake based on chemical analyses of water samples collected from 12 sites during 2002-2009. Chemical oxygen demand, ammonia nitrogen, total nitrogen, total phosphorus and chlorophyll a in Chaohu Lake water showed evidently spatio-temporal variations. With pollution models, water quality of all the sampling locations in the western lake was identified as class III (slightly polluted) to V (heavily polluted), while the eastern half had a slighter pollution stress. The two fuzzy mathematical methods shared almost common assessment results of the western lake (classes V in most cases), but had distinct differences in the membership degree to each pollution class. Comparison of the models showed that in-troduction of membership degree and weight of each factor to fuzzy mathematical models made these methods more reasonable in environmental quality assessment. This study provided some baseline information for water environment assessment, which is of assistance and importance to select suitable models to make assessment results satisfactory to practical requirements and close to the facts.