Studies On Characteristics Of Phosphorus GIS Distribution And Phosphorus-dissolving Microorganism In Sediments Of Lakes In The Middle And Lower Reaches Of The Yangtze River

Lake as the main water source of human life and production has palyed a very important role in the social and economic development.With the rapid development of society and economy,population increasement and continues improvement of people's living standerds,lakes pollution was getting worse by external contamination,and lake eutrophication was the most serious environmrntal problems.Only timely investgation and understanding for trophic status,we could better solve the pollution problems and reduce the possibility of lake eutrophication.Phosphorus was a restrictive factor casuing lake eutrophication.Sediments were potential sources of pollutants in lake aquatic ecosystems.Therefore,the study for distribution characteristic of content and forms of phosphorus in lake sediments,helped to understand the characteristic of lakes'internal phosphorus pollution and provide the lake pollution treatment advice.In the process of lake phosphorus cycling,phosphorus-dissolving microorganism played an important role for conversion between different forms of phosphorus.These microorganisms could degradate the insoluble phosphorus soluble phosphate.So the study of phosphorus-dissolving bacteria in eutrophic lake sediments had important significance.In this paper,75 lakes in the middle and lower reaches of the Yangtze River were research objects.On the basic of investigating the degree of lake water eutrophication,the research was mainly focused on the GIS spatial distribution characteristics of content and forms of phosphorus in lake surface sediment.The strains with the ability of dissolving phosphorus were isolated from the sediments,and the study on their phosphorus-dissolving ability was carried out.After 16SrDNA identification of the phosphorus-dissolving advantage strains,the analysis of the effect of phosphorus content and phosphorus forms on these strains'phosphorus-dissolving ability was carried out.The results were listed below:1?Comprehencive nurtrition state index?TLI index?was used to analyse the lake water nutritional status.In the study lakes,12%of the total lake water was the middle degree of nutritional status,but these lakes had the trend of eutrophication.88%of that had been eutrophic,in which,34%of these eutrophic lakes was light eutrophication,47%was moderate eutrophication,and 7%was severe eutrophication.These results helped to understand real-time lake pollution situation in the study aera,and provide the basis for pollution control.2?SMT grade extraction method was used to measure various forms of phosphorus content in the sediments.GIS spatial distribution graph assisted to analyse the spatial distribution characteristics of phosphorus content and phosphorus forms.The distribution ranges of different forms of phosphorus content in lake sediments in study aera were 437.43²547.79mg/kg?TP?,172.46²054.38mg/kg?IP?,24.56¹932.72mg/kg?NaOH-P?,20.28⁷30.47mg/kg?HCl-P?,132.61¹310.8mg/kg?OP?.The maximum and the minimum difference ratio and intergral coefficient of variation was lager,indicating that distribution was very uneven.The distribution characteristic of TP,IP,HCl-P and NaOH-P forms was similar.Lakes along the Yangze River in Hunan province and the south of Jiangsu province had relatively high phosphorus content.The content of various forms of phosphorus was in wide distribution in Hubei province,and it was mosaic.Lakes in Anhui and northern Jiangsu province which located in Huaihe River Basin appeared high value aera.Poyang Lake and its surrounding lakes were relatively low as a whole.The distribution of OP had significant increasing trend from west to east.Combined with the nutritional status of lakes water bodies,average content of various forms of phosphorus in eutrophic lake sediments were higher than that in non-eutrophic lake sediments,and it showed that phosphorus content in sediment had an effect on the eutrophication of lake water body.3?IP and NaOH-P in sediments had significant relationship with TP in sediments and TP,PO₄^3--P and TLI???in water,and their correlation coefficients were lager than other forms of phosphorus,and in which NaOH-P had the best relationship with other forms of phosphorus.The above analysis showed that NaOH-P in sediments of lakes in the middle and lower reaches of the Yangtze River was the main form which effected the change of phosphorus content both in sediments and water,and influenced the nutritional status of lakes.So,control on the formation and release of NaOH-P in sediments was the key to reduce lake endogenous pollution.In addition,there was a negative relationship between OP and NaOH-P,and they were bioavailable phosphorus,explained the possibility of mutural convertion between them.?NaOH-P+OP?was considered as the potentially releasable phosphorus source in sediments,and had a good correlation with TP.When other forms of phosphorus content were unknow,the potentially releasable phosphorus content in sediments could be roughly calculated by TP content.4?35 effective phosphorus-dissolving strains were screened out from sediments in seven lakes which were Shanpo Lake,Ci Lake,Huama Lake,Gaoyou Lake,Yangcheng Lake,Poyang Lake,Taipo Lake,and they were all organic phosphorus-dissolving bacterium.Using solid plate culture method,and based on the ratio of dissolving phosphorus circle diameter and colony diameter?D/d?,15dominant strains were screened out and seen as the key research object.The16SrDNA sequence analysis of these dominant strains showed that,TP-1,TP-2,CIH-4,GY8#-1,YC4#-4 and PY17#-7 were Pseudomonas sp..HM-2 was Paenibacillus sp..CIH-1,CIH-6,PY17#-2,PY17#-4,PY17#-5,YC4#-2,SP-2 and GY8#-2 were Bacillus sp..Shake bottle of luquid culture experiment was used to measure phosphorus-dissolving ability of the dominant strains.Combined with D/d values judgement result of phosphorus-dissolving ability,it showed that,HM-2,PY17#-2,SP-2,GY8#-2,PY17#-5,YC4#-4,CIH-4,these 7 strains of bacteria had the consistenet comparison results of their phosphorus-dissolving ability,indicating their stable phosphorus-dissolving ability;but GY8#-1,CIH-6,TP-1,TP-2,PY17#-4,CIH-1,PY17#-7,YC4#-2,these 8 strains of bacteria had the inconsistent comparison results,indicating their unstable phosphorus-dissolving ability.5?Throuth the analysis of the relationship between the maximum phosphorus-dissolving amount and various forms of phosphorus content in sediments,the degree of eutrophication,the conclusion were:Different forms of phosphorus in lake sediments had a certain influence on the phosphorus-dissolving capacity.NaOH-P was the main form which impacted this capacity;TLI index and the maximum phosphorus-dissolving amount showed negative correlation relationship,incediting that the degree of eutrophication of lakes might inhibit the phosphorus-dissolving capacity,and the specific reason remained to be further explored.