The Study On River Quality Assessment Of The Mighty River In South China Through The Method Of Planktonic Algae Biological Index

Planktonic diatoms are used for monitoring and evaluating the quality of river because it’s very sensitive to the changes of the aquatic environment factors. Some European countries have evaluated the aquatic quality of rivers and lakes by planktonic diatoms. But now in China, the biological monitoring system of diatoms has not been built. In order to build the system, we should study on the relationship between diatoms and physicochemical factors. At present, the investigation between the planktonic diatoms of the mighty river in the south and environmental factors has not been reported yet, howerver, for the functional classifications of planktonic diatoms in the Ganjiang River Basin has not been reported.This paper relies on the national "11th-Five-Year" major scientific and technological program, "Aquatic Ecological Function Division and Quality Target Management Technology Demonstration in Ganjiang River Basin （2008ZX 07526-008-01）". It’s the first time of systematical ecology exploration and assessment of the status quo of the planktonic diatoms of Ganjiang River basin. It mainly discusses the structure of planktonic diatoms community, functional classifications and the influence of environmental factors on the planktonic diatoms. And the international sensitive trophic diatom index for the first time is used to evaluate the quality of the mighty Ganjiang River in the south. It provides good scientific basis for the evaluation of water the mighty river in the south for the future.Through the analysis of mathematical statistics such as Canonical Correspondence Analysis （CCA）, Redundancy Analysis （RDA）, Pearson Correlation Analysis and ANOVA between environmental factors and planktonic diatom and functional classification of the Ganjiang River Basin in the different water period, different important impact factors are selected out, and then stepwise regression equation between the various functional classification and environmental factors is set up. The main contents and results are as follows:（1） Using the CCA analysis to filter out the environmental factors which affect planktonic diatoms of the Ganjiang River Basin, the results show the main environmental factors of affecting the planktonic diatoms’specie composition:in the high water period, N>Zn>TN>E>CN->pH; in the low water period, N>Pb> Hg>Cr6+>WF>pH; in the normal water period, N>CN">WT>E>As>F". The main environmental factors of affecting the planktonic diatom density:in the high water period, N>Zn>TN>volatile phenol>CN>petroleum; in the low water period, Pb>WT>F>WF>pH>CODMn; in the normal water period, CN>WT>WL>BOD5> Fecal coliform>TN. Thus the results show planktonic diatoms and each environmental factors correlation coefficient is high, so do specie composition and density of planktonic diatoms.（2） According to the dividing principle of functional classifications, the planktonic diatoms of Ganjiang River Basin belonging to 11 functional classifications, the results show it is different dominated functional classifications of planktonic diatoms in the different periods, MP is the dominant functional classification in the high water period, C, MP, P and D are the dominant functional classifications in the low water period, C, P and MP are the dominant functional classifications in the normal water period. Functional classifications of the dominant specie and density, more suitable to live in the mesotrophic and eutrophic aquatic, reflecting aquatic of the Ganjiang River has been a certain disturbed by human, which showing a trend of eutrophication of aquatic.（3） Filtering out different environmental factors that have a significant effect on the each functional classification of the Ganjiang River Basin in the different water period through stepwise multiple regression analysis. In the high water period, Compared with other functional classifications, the correlation coefficient in stepwise regression between four functional classifications （B, MP, Lo and A） and environmental factors is bigger （R= 0.809,0.789,0.781 and 0.508）. Volatile phenol and WT is respectively the first significant factor of B and A. Latitude is the first significant factor of MP and L. In the low water period, the correlation coefficient in stepwise regression between six functional classifications （B, A, D, Lo, MP, SI and P） and environment factors is bigger（R=0.873,0.875,0.653,0.652,0.567,0.556 and 0.530）.WF,CN,BOD₅ and WL is respectively the first significant factor of b,a,d abd lo. latitude is the first significant factor of mp,s1 and p. in the normal water period, the correlation coefficient in stepwise regression between ten functional classifications （TB, C, D, A, P, B, S1, X3, MP and N） and environmental factors is bigger （R= 0.519～0.743）. Pb is significantly the predominant factor affecting the structure of TB and P. BOD5, CN-, WT and Hg is respectively the first significant factor of C, A, B and MP. Fecal coliform is significantly the predominant factor affecting the struction of D, S1 and X3.（4） Using the RDA analysis to filter out the environmental factors which affect planktonic diatoms of the Ganjiang River Basin, the results show the main environmental factors of affecting the functional classifications of planktonic diatoms are N, WL, volatile phenol, Zn and S2- in the high water period. WF, pH, Cu, Pb and Cr6+ are the main environmental factors affecting the functional classifications of planktonic diatoms in the low water period. E, WT, fecal coliform, petroleum and CN- are the main environmental factors affecting the functional classifications of planktonic diatom in the normal water period.（5） Application the international sensitive to water eutrophication evaluation index-Trophic Diatom Index （TDI） for the first time assessment the eutrophication of Ganjiang River Basin in the sourthern. The results show that, high water period （TDI=34.35）< low water period （TDI=56.98）< normal water period （TDI=65.19）. According to TDI eutrophication evaluation standard, the river in the high water period is in the poor trophic status, low water period in the nutritional status, normal water period in the state of eutrophication. River health status in different periods is in order as follows:the high water period> low water period> normal water period. Throughout the the different period of Ganjiang River Basin water quality distribution shows, Ganjiang River’s downstream and Yuan River’s downstream （mainly near the Nanchang） are the main areas which appear super eutrophic state, followed by Meijiang River, Mianshui River, Shangyoujiang River in the upstream of the Ganjiang River.