Risk Assessments On The Heavy Metals Pollution And Evaluation On The Effects On The Diversity Of The Aquatic Plants Communities In The Wetland Of Lean River In The Poyang Lake

The main district of the northeast part of Jiangxi Province is rich in mineralresources, which is an important mineral concentration of nonferrous metals in ourcountry. Abundant of heavy metals acidicmine waste water pollutants produced bylong-term mining activities were disposed into rivers. The river ecosystem health wasbadly infective affected by the pollutants. In the thesis, we chose the watershedswetland of Lean River in the Poyang Lake as the study areas, and studied themacrophyte communities structure and diversity of macrophyte and floristiccompositions based on the field survey data of phytocoenosium for normal season,wet season and dry season in the Wetland of Lean River in the Poyang Lake, and alsostudied the risks of heavy metals pollution in the water and surface soil environmentof Lean River based on the laboratory physicochemical analysis methods of the heavymetals concentration in the overlying water, sediments, surface soils, the pollutionconditions, distribution characteristics and the source of the pollutants by applying thebackground value comparative analysis methods and risk evaluation analysis methods.We also studied the macrophyte communities structures’ response to theenvironmental pollution factors which were also based on the field survey data ofLean River riverine wetlands ecosystem. We also hope to provide some basic data forconservation and restoration of the macrophyte communities in the Wetland of LeanRiver, and also provide some scientific basis for controlling and rehabilitation theheavy metals pollution in the wetland of Lean River. The main results in the thesis aresummarized as follows:First, the main macrophyte were collected from the study areas wereclassificated and identificated, we collected166Vascular plants in the Wetland ofLean River, which belonged to48families,124generas. Fern has1family,1generas,1species. Monocotyledon has11families,39generas,52species; dicotyledon has36families,84generas,113species. The dominant families were Poaceae, Asteraceae,Cyperaceae, Umbellifrae, Cruciferae, Polygonaceae etc.; the dominant genera werePolygonum, Carex, Cyperus, Artemisia, Stellaria, Cardamine, Ludwigia etc. In thethesis, we adopted the four kinds of biodiversity indices methods included Patrickrichness index, Shannon-Wiener diversity index, Simpson species index, Pielouevenness index, and etc. to evaluate the macrophyte diversity of the Wetland in LeanRiver. The results of the four different species diversity indices of the macrophyte in different water time showed that the same regular characteristic, the values of speciesdiversity indices of the macrophyte in different sampling sites in the normal seasonwere more than those of the macrophyte in the dry season, and those of macrophyte inthe dry season were more than those of wet season. And the different species diversityindices of the macrophyte in the sampling sites of Haikou Town located in theheadstream of Lean River, and those sampling sites located in the lower reaches andestuary of Lean River, were much more than those of the macrophyte in the samplingsites located in the upper reaches and middle reaches, and where was contaminatedwith the acidicwaste water containing heavy metals pollutants from Dawu River.Secondly, we also adopted TWINSPAN methods to divide into5different typicalplants formations in different water season in the13sampling sites which located inthe wetland of Lean River. The results were as follows,5plants formations such asMiscanthus sinensis-Cynodon dactylon, Rumex japonicus+Cynodon dactylon,Carex cinerascens+Cynodon dactylon, Miscanthus sinensis-Phalarisarundinacea+Glechoma, longituba+Cynodon dactylon, Phalarisarundinacea+Cynodon dactylon+Stellaria aquatica and so on were contained in thenormal season in the13sampling sites; and other five plants formations such asFagopyrum tataricum+Oenanthe javanica, Cynodon dactylon+Phalaris arundinacea,Cynodon dactylon, Carex tristachya+Phalaris arundinacea+Hemarthria altissima,Miscanthus sinensis-Cynodon dactylon+Miscanthus sinensis-Alternantheraphiloxeroides and so on were contained in the wet season in the13sampling sites; andother five plants formations such as Cynodon dactylon+Carex cinerascens,Miscanthus sinensis-Cynodon dactylon+Celosia argentea, Fagopyrumtataricum+Oenanthe javanica+Hydrilla verticillata, Polygonumsieboldii+Polygonum hydropiper+Polygonum amp-hibium, Cynodondactylon+Phalaris arundinacea were contained in the dry season in the sampling sites.According to the characteristics of the vegetation Spatial distribution, we divided thedistrict of the watersheds of Lean River into different siding-to-siding blocks, whichwere the polluted area located in Dawu River, the unpolluted area located in theheadstream of Lean River, the mixed region which located in the intersection ofDawu River met into Lean River, the polluted area by heavy metals contaminationlocated in the upstream of Lean River, the midstream of Lean River, the lower reachesof Lean River and the estuary of Lean River in Poyang Lake. The dominant species inthe sampling sites located in the district of Dawu River were mainly Cynodondactylon, Phalaris arundinacea； the dominant species were maily Fagopyrum tataricum, Oenanthe javanica, Hydrilla verticillata and Vallisneria spp in HaikouTown in the headstream of Lean River; the dominant species were Miscanthussinensis, Cynodon dactylon, Alternanthera philoxeroides, Celosia argentea in thesampling sites where is the intersection of Dawu River met into Lean River; thedominant species were mainly Cynodon dactylon, Rumex japonicus Houtt,Hemarthria hirta in midstream of Lean River; and the dominant species were Carexspp, Cynodon dactylon, Potamogeton crispus, Nymphoides peltatum in the lowerreaches and estuary of Lean River.Tirdly, the contents of heavy metals in the surface soils and sediments samples inthe sampling sites of Lean River were determined by using physical and chemicaltesting methods, the results indicated that the content value of Copper in the mostsamples were the highest among the three kinds of heavy metal elements, the highestaverage value of the content of Copper was up to591.86mg/kg, which was125timesas much as the background value of the surface sediments in the wetland of PoyangLake in1980s’. And the results of the contents of Copper in the suface soils orsediments samples in different water time showed that the contents of Copper in thesamples in the wet season were more than those of the normal season, and those of thenormal season were more than those of the dry season. There was not any differenceamong the contents of Lead in the samples in different water season. But the contentsof Cadmium in the samples in different water time showed that the contents ofCadmium in the samples in normal season were much more than those of the samplesin wet season, and those of the samples in wet season were almost the same as thoseof the samples in dry season. The results of the contents of the three heavy metalselements in different sampling sites of the watersheds of Lean River showed that thecotents of Copper in the samples from the upstream and midstream of Lean Riverwere more than those of other samples from other sites because the areas in theupstream or the midstream of Lean River were contaminated with the same acidicwaste water containing heavy metals from Dawu River. But the contents of Pb and Cdin the samples from the lower reaches and the estuary of Lean River were relativelymore than those of other sites located in other reaches of Lean River. By usingcorrelation analysis methods, we found that the pollution sources of Copper indifferent sampling sites had the same source that were the acidic sewage, waste waterfrom Dawu River in different water time. And there was a significant positivecorrelation between the contents of the elements Pb and Cd in the samples of the wetseason and the dry season, which reflected that the heavy metals Pb and Cd elements showed compound pollution problem and had some homology.Forthly, we assessed the risks of the heavy metals pollution in the surface soils ofthe wetland by using the single factor index method, the geo-accumulation indexmethod, the Nemero comprehensive pollution index method and the potentialecological risk index method separately. The results indicated that the potentialecological risk index method is the best accurate evaluation method among the fourkinds of evaluation methods for assessment on the risks of the heavy metals pollutionin the soil environment in the wetland of Lean River. The evaluation results showedthat the risk of the heavy metals pollution in the surface soils in the sampling sites ofHaikou Town which located in the headpstream of Lean River was the most slightpollution in the all sampling sites in the wetland of Lean River. But the risks of theheavy metals pollution in the surface soils in the sampling sites, such as the siteslocated in the Gukou Village and the sites in Xiangtun Town, which located in thenear district of the Dawu River, were the most serious pollution. And the evaluationresults of the risk of the heavy metals pollution in the surface soils in the differentsampling sites which located in the watersheds from the middle reaches to the lowerreaches in the wetland of Lean River showed the decreased trend.Finaly, we analysed the effects of the environmental factors on the macrophytecommunities in the wetland of Lean River by using Detrended CanonicalCorrespondence Analysis methods (DCCA). The results indicated that the macrophytecommunities structures in the sampling sites of the wetland in Lean River alsoshowed the corresponding response to the environmental pollution factors. Taking thesampling sites located in Haikou Town as the example, the water environment,surface soils and sediments in the wetland were polluted slightly and had fewerhuman activities, there were high biodiversity and many sensitive plants species in thesampling sites, such as Sagittaria sagittifolia, Oenanthe javanica, Fagopyrumtataricum, Fagopyrum dibotrys, Trachelospermum jasminoides and so on, all thosespecies were distributed in the area. On the other hand, some samling sites in the neardistrict of the intersection of Lean River and Dawu River where were polluted heavilyby the heavy metals from the acidic waste water from Dawu River, where thecommunities structure of the macrophytes is severely degraded, the number of speciesis reduced greatly, especially some sensitive species reduced, stain resistant species orhyper accumulating species increased, such as Miscanthus sinensis, Miscanthusfloridulu, Lophatherum gracile, Celosia argentea, Viola patrinii, Viola yedoensis，Boehmeria nivea, Solanum nigrum and so on. These different species appeared or disappeared, the quantity of the species increased or decreased, the composition of thespecies changed, which could determine the nature and extent of pollution. And in thedownstream region, the vegetation communities structure and heavy metals Pb and Cdshowed significant positive correlation because the combined pollution of the heavymetals Pb and Cd in the soil and water environment, but the correlation of thevegetation communities structure and other environmental factors was not significant.There were also some good living tolerant species which can endure the compoundpollution of the heavy metals Pb and Cd, such as Artemisia selengensis, Gnaphaliumaffine, Soliva anthemifolia, Lobelia chinensis and so on.Based on the above analysis results, we drew the following conclusions that therisks of the heavy metals pollution in the water and surface soil environment of thewetland of Lean River in the Poyang Lake reached to be relatively serious, which hadbeen significant influence on the macrophyte communities structure and the plantsdiversity. With the further development and utilization of the mineral resources in theareas of Lean River, it will further aggravate the serious influence on the wetlandecological environment of Lean River in Poyang Lake, and will bring about a seriousthreat to the biodiversity and the security of the wetland ecological environment. Inorder to prevent the heavy metals pollution threat to the diversity of the wetland inPoyang Lake, and to restore and reconstruct the vegetation in the wetland of LeanRiver in Poyang Lake, we should continue to carry out the scientific research work onthe migration and transformation of the heavy metals in the wetland ecological systemprocesses. We also need to inquire into the study on the warning line of heavy meatlspollution and research on the establishment of mathematical model to predict thechanges of the heavy metals contents in the Wetland of Lean River in the PoyangLake. We should strengthen the investigation and research on the plants resources,especially the rare, unique and important wild plants resources, and should take someeffective measures to protect the plants resources in the Wetland of Lean River in thePoyang Lake further more.