The Technical Research On Greening Downstream Of Duliujianhe River In Tianjin

Rivers had always been inseparable with cultural heritage,ethnic flourished inseparable,both sides of river gave birth to a long history and great civilization.With the comprehensively promotion of urbanization,the river had once again become an important basis for urban development.As an important flood channel and flood protection line in south of Tianjin,Duliujian River was in a situation of bad soil environment,sticky soil structure,serious salinization and a urgent green problem.In this paper,Tianjin Duliujian River greening test section was chosen for the study,a in-depth survey of the river 63-64 km of Duliujian river and the analyze of the section about the river water quality and soil relating physical and chemical properties were done.Based on years of research on saline-alkali soil and greening projects practice,indoor soil column leaching experiments and field irrigation tests,indoor column experiments and outdoor field irrigation leaching tests were carried out according to Tianjin saline-alkali soil characteristic.In the end,coastal saline soil improvement and utilization program and feasible river green technology were proposed,in order to provide full and reliable theoretical and technical support for the river green.The main conclusions were as follows:(1)Soil bulk of saline alkali soil density between 1.22-1.60g/cm3,with an average of 1.42g/cm3;soil porosity between 40.31%-51.05%,the marine mud dredger fill in Tianjin is heavy and clay,the content of sand is little,only account for 15.39% of the total mass;the content of powder accounts for 69.99% of the total mass,the marine mud dredger fill in Tianjin belongs to poor graded soil.The permeability coefficient of saline alkali soil segment significantly,surface coefficient is with an average of3.95×10-4cm/s,and subsoil(40cm below)permeability is relatively poor,with an average of 2.28×10-5cm/s,lower than the ordinary farmland 1 to 2 orders of magnitude,the permeability is poor.(2)The saline alkali soil total salt content in soil is very high,and the overall average reaches 19.13g/kg(variation between 14.91-27.28g/kg),was nearly 6.4 times of Tianjin green planting soil standards,crops can not survive.The pH value is high,which is in line with pH characteristic of Tianjin area.To ensure the survival of green,reducing soil total salt content is especially important.And soil organic matter levels is low with the overall average of 16.64g/kg.(3)Single maize straw can increase soil permeability,but with limited ability to improve.The mix of maize straw and mountain land is the key to improving coastal saline soil permeability,which lead to significantly increasing permeability of the soil,but in different proportions conducts to different results.Desalination desaltingprocess can be divided into fast desalination,slow desalination and leveled three stages.Gypsum is able to suppress salinization phenomenon during desalination process.(4)Comprehensive analysis of desalination desalination process and efficiency,treatment D(original soil+35% mountain land+20% maize straw+1.2% Gypsum)comprehensive improve saline best,with the salt content reduced to 3.95g/kg,desalination efficiency of 79.4% and pH of 8.27.(5)The field irrigation tests of high-strength soil improvement group shows good consistency with indoor column experiments,whose salt content reduced to 3.61g/kg,desalination efficiency of 81.1% and pH of 8.37.The saline-alkali soil improvement programs for effective desalting is fast and stable.(6)Sophora japonica,Sophora japonica Linn,Fraxinus velutina Torr,Salix sp,Ulmus pumila cv.jinye are selected as green varieties,based on salinity uphold,a strong ability to adapt to cold and drought,planting high survival rate and the principles of landscape.(7)Green Efficiency Survey:Two months after planting green saplings,tree species in a sample survey of planting survival rate is high,more than 95%,but in a small sample size,reliability is not high;4 months later,growing status census results show the survival rate of green tree species but Salix sp kept above 94.5%,and the growth potential is good,which has once again proven the feasibility of soil improvement and late planting conservation.