| Non-point source pollution refers to the pollution caused by pollutants flowing into receiving water bodies（rivers,lakes,reservoirs and bays）from non-specific places through surface runoff in the process of natural precipitation and snowmelt.Since 1960s,the management of non-point source pollution has been subject to different controls in many ways,and simulation is an important step in helping managers accurately understand pollution,especially in polluted environments.Unlike point source pollution,non-point source pollution comes from plenty of sources with complex spatial distribution,randomness in the polluted process,and it is difficult to control and management.An example in America shows that there were 58%total nitrogen,87%total phosphorus,and 98%total suspended solid come from non-point source pollution in 1980s.In addition,in 1990 years,there were about 30%-50%waterbodies polluted in China by non-point source pollution.Non-point source pollution from agricultural activities is regarded as the first pollution,in which usually occurring in America,Japan,Europe,and some developed countries.Nowadays,the existence in real of both point source pollution and non-point source pollution in China are happening,which the pollution is mainly from agricultural and industrial activities.In recent 30 years,China has a very quickly economic development as industrialization and urbanization process,and this signification leading to change land use situation as well as making environmental pollution,in which non-point source pollutants are very difficult to treatment and manage.Therefore,the simulation of non-point source pollution load and land use optimization research were emphasized in this thesis.The Yangtze River Basin is the biggest basin in China,in this study,precipitation,elevation,runoff coefficients of total nitrogen and total phosphorus,and land use in 1980,2005,2010 of the Yangtze River Basin were applied to the improved export coefficient model to estimate and simulate non-point source pollution load in the Yangtze River Basin.Then,this study used correlation analysis by the self-organizing map（SOM）model to analyze effected factors of non-point source pollution.In addition,the multi-objective optimization（MOP）model and genetic algorithm（GA）were applied to search the optimal urban growth pattern in the Yangtze River Basin in 2020,and to explore the optimal planning of economic development and non-point source pollution in the basin.The main contents and conclusions are as follows:1.International research trend analysis of non-point source pollution based on bibliometrics method.The results showed that:（1）The first document relates to non-point source pollution was published in 1973.From1973 to 2012,4067 documents on non-point source pollution were published.The research productivities of non-point source document were divided into two stages,in which the first stage is from 1973 to 1990,and the second stage is from 1991 to 2012.Especially,in the second stage,total research productivity of non-point source pollution document increases significantly,from 60 documents in 1991 to 272 documents in 2012.（2）The authors of the non-point source pollution documents were mainly distributed in European countries and America,especially in the eastern America.The next was China,India,Australia and some South American countries,but the publication in African countries was very few.The first 15 countries had the high total research productivity,in which the USA had the highest total research productivity;the China and Canada rank the second and the third.（3）Author keywords of non-point source pollution documents from 1900-2012 were divided into 3 stages（1900-1997;1998-2005;2006-2012）and research productivities were presented:The first ranking was“non-point source pollution”with 1064 documents in total research productivity.The second ranking was“water quality”with 577 documents in total research productivity.The third ranking was“phosphorus”with 240 documents in total research productivity.2.Land use changes in the Yangtze River basin in 1980,2005 and 2010.The main land use types in Yangtze River Basin were agricultural land,forest,desert,water,wetland,construction land,desert land and grassland.Compared with 1980,the area of agricultural land decreased in 2005 and 2010;the area of forest,wasteland and urban construction land increased;and the area of wetland decreased in 2005 and increased in 2010.3.The non-point source pollution load assessment in the Yangtze River Basin based on the Improved Export Coefficient Model（IECM）,and the analysis of effected factors of non-point source pollution load based on self-organizing（SOM）model.The exposes effected factors of non-point source pollution include precipitation,land use types,vegetation cover rate data,etc.The results indicated that:（1）Spatial distribution of non-point source pollution influencing factors in the Yangtze River Basin.In 1980,the numerical range of rainfall impact factor was 0.027-2.12mm;in2005,the numerical range was 0.063-1.835mm;and in 2010,the numerical range was0.22-1.72mm.In addition,the high value of rainfall impact factor almost distributed in the east of basin and some regions in the middle of the basin.However,they are revealed in different sizes and positions.Besides,the low values of rainfall impact factor located in western and small regions in northern of the basin.Terrain impact factor was calculated and simulated from equation of slope on the Yangtze River basin.Its value gains from 0.85 to1.1475,and the low terrain impact factor value located mainly at eastern,western small region and a big hole in the middle region of the basin;the high terrain impact factor value located mainly around a big hole of low value at middle region in the basin.（2）Both TN and TP pollution loads in the Yangtze River Basin showed significant spatial and temporal distribution characteristics.TN pollution loads was 0-59.67kg/ha,0-50.02kg/ha,0-51.16kg/ha respectively in 1980,2005,2010.TP pollution load was 0-1.83kg/ha,0-1.52kg/ha,0-1.55kg/ha respectively in 1980,2005,and 2010.The spatial distribution of TN pollution loads in 1980 and 2005 was similarly.The high value area main locates at the east region of the Yangtze River Basin,about three-quarters of the basin and the low-value,area is mainly distributed in the west of the basin and some small regions in the east of the basin as urban construction land use region.Nevertheless,in 2010,the high value and low value of TN pollution load was dispersed.In the latitudinal direction,high value was mainly concentrated on the northern region while the low value was mainly distributed on the southern region.Similar in the spatial distribution of total phosphorus load in 1980 and 2005,the high value was mainly distributed in the eastern basin around three-quarters of the basin,while the low value was distributed mainly in the western basin.However,the spatial distribution of the high value was located at central and eastern of the basin while the low value area was in the eastern and western areas in 2010.（3）The estimation of non-point source pollution loads（total nitrogen and total phosphorus）for each land use type in 11 sub-basins.In total nitrogen load indicates average contribution in 1980 was gained from 4.76 to 22.81 kg/ha,in which Tai Lake sub-basin was a region has the highest contribution on agriculture land,water area,and buildup land.The highest contribution on forest pattern belong to Poyang Lake sub-basin;Jinsha River sub-basin had the least averaged contribution but has the highest load value on the grassy land,barren,and desert pattern.In 2005,the average contribution was obtained from 4.28 to15.48 kg/ha,and river downstream is area has the highest average total nitrogen load value and also has the highest total nitrogen load value in the agricultural land type.The least average total nitrogen contribution was Jinsha River sub-basin and has the highest total nitrogen load value in the grassy land,wetland,barren,and desert type.In 2010,average contribution of total nitrogen occupies from 4.87 kg/ha to 15.53 kg/ha,and at the Tai lake sub-basin has both the highest average contribution and the highest TN load on forest,agricultural land,and urban construction land pattern,as well as the water area is the biggest.Moreover,with average contribution is low on the Jinsha River sub-basin,but total nitrogen contribution on the grassy land and desert land pattern is the highest.In total phosphorus presents,average contribution of total phosphorus is obtained from 0.16 kg/ha to 0.69 kg/ha in 1980,and Tai Lake sub-basin has the highest average contribution of total phosphorus.In2005,the average contribution is from 0.12 kg/ha to 0.47 kg/ha.Moreover,the highest average total phosphorus contribution in 2005 locates at river downstream,and it has the highest total phosphorus load value on agriculture land type.In 2010,the average contribution line is represented from the lowest value to the highest value,from 0.18 kg/ha to 0.51 kg/ha respectively,and Tai lake sub-basin is not only has the highest average total phosphorus contribution,but also has the highest total phosphorus contribution on the forest land,agricultural land,and urban construction land pattern.Besides,the highest total phosphorus contribution on the grassy land and desert land pattern belongs to Jinsha River sub-basin with the medium total phosphorus average contribution.（4）Correlation analysis between mean total nitrogen load and mean total phosphorus load based on regression analysis.It indicated average contribution of total nitrogen had close relationship with average contribution of total phosphorus and was positive relationship.It was proved through regression line and determined coefficient.Particular,in1980 is R2=0.981;R2=0.964 in 2005;and R2=0.983 in 2010.Moreover,the P value<0.0001 in all three years.The prediction of non-point source pollution load in the future was based on regression models,which were presented on each map per year,such as Y=0.031X+0.011 in 1980,Y=0.031X+0.008 in 2005,and Y=0.033X–0.004 in 2010.It was proved the average contribution of total nitrogen has affected strongly to the average contribution of total phosphorus.From that,this study had relationship comparison of total nitrogen average contribution and total phosphorus average contribution in 1980,2005,and2010.It indicates the relationship in 2010 was the closest relation.Next was in 1980,and finally is in 2005.These meanings could be helped planner make decisions better in control of pollutant factors（total nitrogen and total phosphorus）on the Yangtze River Basin,or in other word,the average contribution of total phosphorus will has been controlled if contribution of total nitrogen is monitored well.（5）The influence factors of non-point source pollution load were analyzed based on self-organizing mapping model（SOM）.The results indicated neurons make clusters and distribute on different positions in each map per factor.Moreover,in the correlation of factors in 1980,the agriculture land factor and the forestland factor had correlated with each other.Total nitrogen load factor and total phosphorus load factor had a close correlation with each other.Especially,the agriculture land factor had a high correlation with the forestland factor at the highest value.More especially at the wetland and the barren land factor,they had a close correlation from the lowest to the highest value.It was only a few medium value of two these factors has the different.Moreover,the population factor had a high correlation with the agriculture land and the forestland factor at the highest value.In the correlation of factors in 2005 showed that,factors of precipitation and the forest land factor;the grassy land and barren factor had correlated with each other at the lowest value,but distribute into different positions on the maps such as the grassy land factor and the barren factor were from top left corner to bottom right corner.Especially,the wetland factor and the barren land factor;total nitrogen load factor and total phosphorus load had closely correlated with each other at the lowest as well as the highest value.The forest cover rate factor had not any correlation with others.In the correlation of factors in 2010 presents the precipitation,total nitrogen load,and total phosphorus load factors had correlation in the highest value,in which total nitrogen load and total phosphorus load factors had a close correlation each other from the lowest value to the highest value.The wetland and barren land factors had correlation in the lowest value and the highest value.The agricultural land,forestland,and grassy land factors had a correlation one another in the high value and the highest value.The forest cover rate factor had not any correlation with other factors.4.Search optimal solution via multi-objectives optimization process（MOP）in Yangtze River Basin for the four objectives of minimum non-point source pollution,maximum gross domestic product,minimum changing cost and minimum incompatibility index.The results show that:（1）The fitness value of objectives in multi-objective optimization（MOP）changes in the first 100th iteration and it becomes stability after 100th iteration.（2）The optimal solutions is also found for minimization of NPS pollution load,minimization of changing cost index,maximization of GDP value,and minimization of incompatibility index objectives although between them have high conflicting.There are six the best optimal solutions in the relationship of minimization of NPS pollution load and minimization of changing cost index;eleven the best optimal solutions for minimization of NPS pollution load and maximization of GDP value;and nine the best optimal solutions for minimization of NPS pollution load and minimization of incompatibility index.Moreover,more next generation and more have optimal solutions than the first generation.5.Best Management Practices（BMPs）for non-point source pollution control in Yangtze River Basin.Almost Jinsha River basin,Jialing River sub-basin,Dongting Lake sub-basin and Poyang Lake sub-basin are key control areas in this study.NPS pollution control BMPs could effectively reduce the TN and TP load.In addition to that,it proposed the BMPs to control non-point source pollution in the Yangtze River Basin:（1）macro-management BMPs measures,such as needing to establish NPS pollution management institutions and set up a special fund,strengthen environmental management,construct NPS pollution monitoring network,enhance public awareness and education.（2）Source-control BMPs,BMPs for reducing pollution in process,and terminal control BMPs is proposed respectively to reduce the non-point source pollution load and enhance efficiency of non-point source pollution control.Source-control BMPs include agriculture NPS control and urban NPS control.In agriculture NPS area,needs to restrict pesticide excess using and residual pesticides,establish solid waste septic tank and discharging liquid waste after,plenty of plant shrubs in the channel;aquatic plants in the wetland;and grassy plants in the buffer,increase vegetative cover rate especially at north eastern region of the Yangtze River Basin,such as Qinghai and Xizang provinces.In the urban NPS area needs to improve the urban forestation and reduce impervious area.In the sidewalk area needs to be collected pollutants by the vacuum sweeper or broom sweeper.Plenty plant of grass and tree around construction sites of the basin to absorb dust,runoff,and mitigate contaminant emitting in the environment.The optimum proposal of BMPs for reducing pollution in process including farmland runoff recharge after processing and urban runoff used for greening after purification;properly dispose of motor oil and chemicals,and forbidding pour directly on the ground or in runoff.Terminal treatment BMPs lies in achieving the effect of purifying pollutants through detention of runoff in the pond,wetland and lake ecological system.The specific measurements include constructing riparian buffer strips and artificial wetlands are to absorb the agriculture runoff.Constructing riparian buffer strips and artificial wetland are to absorb the agriculture runoff.Riparian buffer strip including grassy land and forest could effectively holding up pollutants,increasing vegetation coverage and improving regional environment.Artificial wetland is used to purifying wastewater via intercept,adsorption,and precipitation,which has a better removal effect of Nitrogen and Phosphorus. |
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