A Study Of Heavy Metal Pollution On The Plankton Community Genetic Structure And Its Ecological Risk Evaluation In Huayuan River In Xiangxi

Background and Object: The Huayuan River lies in the Huayuan County Xiangxiautonomous prefecture of Hunan Province in south China (E109°43′, N28°29′). It isthe major river in this country which provides living water and aquaculture water forlocal residents. With the development of mining industry, manganese sulfate residuewas piled up along the river and waster water directly discharged into the riverwithout waster treatment, these all led to serious heavy metal contamination on theHuayuan River. Our lab has been devoted to the investigation of heavy metalpollution and the pollution remediation of Huayuan River and the pollutionremediation since2007, and has achieved certain results. On the basis of previouswork, the study took the water sample from the Huayuan River again, which aims toevaluate the current pollution situation of the river and to explore the impact ofheavy metal pollution on the plankton community genetic structure.Methods:1、The contents of heavy metal in eight water samples (Tea hole,1000metresupstream of Ditch Bridge,1000metres downstream of Ditch Bridge, Pennybeach, pontoon, junction, grinding rock slope,Lion Bridge) were determined byusing atomic absorption spectrophotometry.2、The potential ecological risk assessment of the water in Huayuan River wasanalyzed by Hakanson ecological risk index method.3、 RAPD technology was used to analyse genetic diversity of plankton communityin eight samples polluted by heavy metals and the correlation between DNAfingerprint and heavy metal factor.4、 The genetic diversity of prokaryotic and eukaryotic plankton in eight samples,and its correlations with the heavy metal factors were detected by using DGGE technology.Results:1、The average concentrations of Mn、Pb、Cd、Fe、Zn were above the limiting valueof 《Drinking water standard in China》, and the average contents of Mn、Pb、Cd were above standard value of《WHO drinking water quality standard》.2、In the eight sampling sites, the order of singal heavy metal potential ecologicalrisk coefficient from high to low is as follows: Cd＞Pb＞Mn＞Zn＞Cu. Theecological risk index of eight sampling ponint from high to low is: grinding rockslope、Lion Bridge、1000metres downstream of Ditch Bridge、pontoon、junction、1000metres upstream of Ditch Bridge、Penny beach、Tea hole.3、Cluster analysis of RAPD and heavy metal concentrations revealed that: there wasa good correlation between heavy metal concentrations and the composition ofplankton in the severe polluted sampling sites of Huayuan River.But it did notshow a good correlation in the slightly and medium pollution sites,whichsuggested that it is not enough to use RAPD tcchnology alone to evaluate thepollution degree of the water.4、By using DGGE technology, the analysis of the16s rDNA and18s rDNA ofplankton indicated that: Prokaryotes is simple, short life cycle, rather sensitive tothe change of environment,which can be better used in environment pollutionevaluation.5、At different levels of heavy metal pollution in water, other DNA fingerprinttechnology in combination with other environment factors should be needed todiscuss the effects of heavy metal pollution on bacterioplankton andphytoplankton and planktonic animal communities in Huayuan river separately,so as to improve the monitoring system of heavy metal pollution of water onDNA fingerprint level. Conclusion：1、The average concentrations of Mn、Pb、Cd、Fe、Zn were above the limiting valueof《Drinking water standard in China》, and the average contents of Mn、Pb、Cd were above standard value of《WHO drinking water quality standard》. Theecological risk index is between slight and very strong degree.2、 There is a good correlation between the community genetic structure ofprokaryotes and heavy metal pollution, which can be better used in environmentpollution evaluation.