Effects Of Phosphorus Forms In Sediments Of Lake Sediments On Water Nutrition In Jiangxi Province

With the rapid economic development of Jiangxi Province,small and medium-sized lakes,like large lakes,have received a large amount of phosphorus nutrients from industrial,agricultural and domestic production.As a result,the problem of lake eutrophication has become more and more serious.Some lake water bodies present different forms of phosphorus in sediments of lake sediments at the primary stage of eutrophication.The influence of phosphorus content on water nutrition is different.Studying the phosphorus occurrence form,content and phosphorus adsorption characteristics of sediments in different types of lake sediments and the influence of phosphorus occurrence form on water nutrition can help better explain the contribution of endogenous phosphorus to water eutrophication.In this paper,18 lakes?Junshan Lake,Zhuhu Lake,Jinxi Lake,Waiqinglan Lake,Yangfang Lake,Neiqinglan Lake,Dasha Lake,Chihu Lake,Saicheng Lake,Xinmiao Lake,Niuyahu Lake,Bali Lake,North-South Lake,Taibo Lake,Dahu Lake,Fanghu Lake,Yaogang Lake and Yaohu Lake?are selected as the research objects.The five indices of chlorophyll a?Chla?,total phosphorus?TP?,total nitrogen?TN?,transparency?SD?and permanganate index?CODMn?were used as evaluation indices of Lake eutrophication.Eighteen lakes were divided into two types:moderately eutrophic lakes and mildly eutrophic lakes.The relationship between different phosphorus forms in sediments of sediments of two types of lakes and small and medium-sized lakes and the nutritional status of water bodies were studied.The influence of phosphorus forms in sediments on water nutrition was clarified;the relationship between phosphorus adsorption parameters of lake sediments and water nutrition,and the relationship between phosphorus adsorption parameters PQmax,NAP,EPC0 and m and TP0,DP in water were also studied;the best parameters such as phosphorus occurrence forms and adsorption parameters of sediments were screened out,and the optimum parameters were constructed by principal component analysis.The main components of the indicators,and then study the comprehensive impact of phosphorus forms in sediments on the water nutrition of 18 lakes,try to put forward the comprehensive indicators of water nutrition status affected by phosphorus forms in sediments,that is,the comprehensive factors of sediments.Through the above research,the following conclusions are drawn:1.Classification results of lake trophic types.According to the TLI method,chlorophyll a?Chla?,total phosphorus?TP?,total nitrogen?TN?,transparency?SD?and permanganate index?CODMn?in 18 lakes were used as the evaluation indexes of Lake eutrophication.They were divided into two types:middle-trophic lakes:Junshan lake,Zhuhu lake,Jinxi lake,Waiqinglan lake,Yangfang lake and Inner-trophic lake.There are 11 lakes in Qinglan Lake,Dasha Lake,Chihu Lake,Saicheng Lake,Xinmiao Lake and Niuyahu Lake.There are 7 lakes in mild eutrophication type,including Yao Lake,Bali Lake,North-South Lake,Taibo Lake,Dahu Lake,Fang Lake and Yaogang Lake.2.Phosphorus forms and their differences in sediments of lakes with different nutrient types.The contents of different forms of phosphorus in sediments of middle trophic lakes were TP?601.14 mg/Kg?,IP?451.33 mg/Kg?,Fe/Al-P?325.92 mg/Kg?,Ca-P?167.67 mg/Kg?,OP?124.06 mg/Kg?,respectively.The contents of different forms of phosphorus in sediments of mild eutrophic lakes were TP?711.77 mg/Kg?,IP?518.49 mg/Kg?,Fe/Al-P?398.71mg/Kg?,Ca-P?194 mg/Kg?.41 mg/Kg,OP?190.44 mg/Kg?;the order of average phosphorus content in the two types of lakes is TP>IP>Fe/Al-P>Ca-P>OP,and the average phosphorus content is less than that in the mild eutrophication type.The average weight ratios of IP,Fe/Al-P,Ca-P and OP to TP were 75.1%,55.3%,27.9%and 20.6%in the middle trophic type and 72.8%,60.4%,27.3%and 26.8%in the mild eutrophic type respectively.The main source of phosphorus forms in the two types of lakes is IP,supplemented by OP,while Fe/Al-P is dominant in IP.In both types of lakes,TP-IP and TP-Fe/Al-P are significantly correlated with a=0.05.IP-Fe/Al-P was correlated with alpha=0.1 in the middle trophic type and significantly correlated with alpha=0.05 in the mild eutrophic type.The origin of OP in middle-trophic lakes is different;using principal component analysis method,we can conclude that the first type of influencing factors in middle-trophic lakes are Fe/Al-P and OP,the second type of influencing factors are IP and Ca-P,and the influencing factors in mild eutrophic lakes are Fe/Al-P,OP and Ca-P;the difference of phosphorus occurrence characteristics in sediments of middle-trophic lakes is mainly determined by unstable phosphorus or bioavailable phosphorus,while the difference is light.Degree eutrophic lakes are determined by total phosphorus.The difference of phosphorus forms in sediments is determined by the input of exogenous phosphorus from lakes and the deposition phosphorus produced by the death of phytoplankton in lakes.The difference of phosphorus forms in sediments of two types of lakes mainly depends on Fe/Al-P,and the difference of sources is mainly affected by domestic sewage and industrial wastewater.3.Phosphorus occurrence patterns and their differences in sediments of small and medium-sized lakes.The average size of different forms of phosphorus in sediments of middle and small lakes in Jiangxi Province is TP>IP>Fe/Al-P>Ca-P>OP.The proportion of IP,Fe/Al-P,Ca-P and OP in sediments is 73.94%,54.50%,27.54%and 23%respectively.The increase of TP mainly comes from IP,followed by OP;Fe/Al-P is the main source of IP.Urban lakes in small and medium-sized lakes in Jiangxi Province are seriously affected by the discharge of human domestic sewage and industrial wastewater.Fe/Al-P in sediment of medium and small lakes is the main occurrence form of IP,and its potential release to overlying water body is great,which should be paid attention to.Open lakes with high Ca-P content are mainly affected by the Yangtze River,Poyang Lake and Xiuhe River,and the running water carries some sediment into the water body.There is a significant correlation between TP and IP in sediments of medium and small lakes in Jiangxi Province and between TP and Fe/Al-P.TP content in sediments can reflect the potential release of phosphorus to a certain extent.IP and OP have no significant correlation,but their contents are relatively independent.The correlation between Ca-P and Fe/Al-P is not significant,indicating that the two sources are different.The first principal component of medium and small lakes in Jiangxi Province is IP,Fe/Al-P and OP,and the second principal component is IP and Ca-P.The distribution of TP is affected by IP,Fe/Al-P and OP,and the content and distribution of TP,IP,Fe/Al-P,Ca-P and OP are affected by OM.4.Characteristics of phosphorus adsorption in Lake sediments.The adsorption of phosphorus by sediments of middle-trophic lakes and mild eutrophic lakes was mainly completed in the first 12 hours,and then gradually reached the adsorption equilibrium.The best model for describing the adsorption kinetics of phosphorus in sediments was the modified Elovich model.Under low initial concentration,the isotherms of phosphorus adsorption on sediments of medium-eutrophic lakes and mild eutrophic lakes were in line with Linear model,while at high initial concentration,the isotherms of phosphorus adsorption on sediments of medium-eutrophic lakes and mild eutrophic lakes were well matched with Langmuir model and Freundlich model,and reached significant levels?P<0.05?.The maximum amount of phosphorus adsorbed by sediments of middle-trophic lakes is669.83-833.22 mg/kg,and 718.03-856.82 mg/kg for mild eutrophic lakes.The phosphorus adsorbed by sediments of middle-trophic lakes is 112.01-216.07 L/kg,and 124.31-148.91L/kg for mild eutrophic lakes.NAP of sediments in the two types of lakes are 15.27-25.18mg/Kg and 22.25-30.84 mg/Kg,respectively.The EPC₀ of sediments from middle-trophic lakes is 0.07 mg/L⁰.23 mg/L;that of mild eutrophic lakes is 0.16 mg/L⁰.26 mg/L;that of sediments from middle-trophic lakes is less than that of sediments from mild eutrophic lakes:Q_max,NAP,EPC₀;the adsorption efficiency m is opposite;both types of sediments have desorption behavior to the outside world;and that of sediments from middle-trophic lakes is less than that from mild eutrophic lakes.Q_max,NAP and EPC₀ were correlated well with TP,IP,Fe/Al-P and OP contents,while Q_max,NAP and EPC₀ were correlated well with IP and Fe/Al-P contents in slightly eutrophic sediments,and Q_max,NAP and EPC₀ were correlated with sediment pollution.5.Effects of phosphorus forms and phosphorus adsorption characteristics of lake sediments on water nutrient status.TP content in sediment of middle trophic lake is negatively correlated with TP₀ and DP content in overlying water body,and positively correlated with Chla content;Fe/Al-P content is positively correlated with Chla content in overlying water body;IP,Ca-P,OP are weakly correlated with TP₀,DP and Chla content in overlying water body;it shows that Fe/Al-P content has a great influence on eutrophication of medium trophic lake water body;and slightly eutrophic lake body has a positive correlation with Chla content.TP,IP,Fe/Al-P and OP in sediment are positively correlated with TP₀,DP and Chla in water body,which indicates that these four forms of phosphorus have important contributions to phosphorus content in overlying water body;Ca-P has no correlation with TP₀,DP and Chla content in overlying water body in medium-trophic lakes and mild eutrophic lakes because of its stable nature;Total phosphorus?TP?,iron-aluminum bound phosphorus?Fe/Al-P?,calcium bound phosphorus?Ca-P?,organic phosphorus?OP?and inorganic phosphorus?IP?contents in the sediments are basically consistent with the nutrient levels of the lakes.NAP and EPC₀ were positively correlated with DP,while Q_maxax was positively correlated with Chla,indicating that NAP,EPC₀ and Q_maxax were closely related to the nutrient status of sediments from medium and small lakes in Jiangxi Province.The comprehensive factors of sediments were TP,IP,Fe/Al-P,NAP and EPC₀.