The Research On Handicap Characteristics And Regulation Mechanism For Dredger Fill As The Growing Media

Coastal dredger fill in situ soil improvement technology has recently become a hotissue for the saline soil improvement at home and abroad. For characteristics of theheavy salt and alkali of the Tianjin Coastal Tourism Area dredger fill, this paper focuson the soil improvement technology in situ of desalination and control alkali. As thegrowing media, the handicap characteristics of the dredger fill has determined by thebackground value of the physical and chemical properties and the effect ofgroundwater TDS （total dissolved solids） on the migration of soil salinity. A kind ofeffective regulation mechanism is suggested on account of these handicapcharacteristics. That is Ca provide by the desulphurization by-products of the powerstation exchange with the Na which is adsorptioned on the soil colloid, ultimately toachieve the purpose of lower soil salinity and improve soil structure by leaching, andfor the coastal dredger fill in situ modified provide a theoretical foundation andtechnical support, make coastal reclamation of saline soil to achieve a rationalutilization of resources, to achieve the purpose of construction of the coastalecological environment.The results showed that the salt content of soil in tourist area was extremely high.In different sampling points soil salt content fluctuated between5.15and17.81g·kg^-1,Cl^-and Na⁺content more than the sum of soil salt ions90%, the soil belonged to thechloride type of saline soil. The alkaline characteristics of soil were outstanding, themaximum value of the pH, SAR （sodium adsorption ratio） and ESP （degree of soilalkalization） were8.96,103.68and59.67, respectively, and had very serious toxiceffects on plants. According to the analysis of soil nutrients in the district, theavailable potassium and phosphorus content in soil were rich, but organic matter andavailable nitrogen content were very lack, therefore a certain amount of nitrogen andorganic matter must be added into the soil in order to dredger fill as a green matrix.Due to capillary action of groundwater, soil salt ions migrated to the upper, soilalkalization degree gradually increased with the rise of capillary water, and was proportional to the groundwater TDS.The soil column leaching simulation test results showed that the desulfurizedgypsum and PAM （Polyacrylamide） can accelerate the desalinization efficiency ofhydraulic fill. During the test, the original dredger fill had not leachate outflow fromstart to finish in two ways. Desulfurized gypsum with different contact times andamounts can improve soil properties, enhance the saturated hydraulic conductivity,reduce the degree of soil salinization, and total salt of soil were reduced from13.03g·kg^-1to0.29-0.71g·kg^-1and0.36-0.44g·kg^-1by these two methods respectively, thedecrease range was over94.53percent, on combined effect of desulfurized gypsumand PAM, soil salt downed to0.30-0.35g·kg^-1. The alkaline features of soil hadobviously improved, compared with the original dredger fill, SAR and ESP of soilafter leaching decreased more than96.63%and98.93%respectively. But pH of eachtreatment significantly increased, in the test of different amounts of desulfurizedgypsum, pH increased from7.81to8.45.