Application Of Municipal Sludge In Coastal Saline Soil Improvement

Tianjin Binhai and its surrounding area is one of the main occurrence areas of the coastal salinealkali soil.In the context of rapid urban development,it is an important challenge for Tianjin Binhai and its surrounding areas to develop and utilize saline soil resources scientifically and rationally.It is necessary prerequisite for the sustainable utilization of saline soil resources to correctly evaluate the characteristics of soil salinization and master the spatial distribution of soil salinity.Due to the increasing production and treatment of domestic and industrial wastewater,a massive amount of sewage sludge has been generated and discharged to the environment.Heavy metals are the primary pollutants in sewage sludge and present a serious environmental problem.In order to study the leaching behaviors of contaminants in saline-alkali soil amended with sewage sludge,the changes of nutrients content,heavy metal form distribution and the contents of organic matter,N,P contaminants and heavy metals in leachate were investigated through incubation and leaching experiment.The main method used was SBR,the leaching of heavy metals in sludge was made,started by extraction of colloidal from saline soil;acid extraction;followed by alternative,reversible and oxidation states.It was necessary to apply sequential extraction techniques to obtain a suitable information about their bioavailability and toxicity.The results showed that the quality of 1.5 times,of soil organic matter was increased by adding sludge in the early stage(incubation 0d),increasing total nitrogen 2.24 times,total phosphorus 1.6 times,available nitrogen 1.94 times,available phosphorus 1.8 times,available potassium 1.06 times,and all index values were significantly different from those of saline-alkali soil control group.With the prolongation of incubation time,organic matter decreased slightly in the improved soil due to his decomposition.It was showed that the total amount of heavy metals in sludge improved while in the soil it increased.It can be seen that Cr,Cd and Pb were mainly residues in saline-alkali soil with the exchangeable state of Cr,Cd,Pb and the transition of the reversible state to the oxidation state and the residue state,the migration and transformation tendency of the sludge in saline-alkali soil was less than the saline-alkali soil,Cr,Pb in the improvement 30 days changed trend was more stable,and Cd in the improvement of 15 days before the change trend was larger,from 15 days to 30 days basically stable.The Cd that was easily migrated within 15 days was converted to a more stable form and was fixed.The application of sewage sludge can effectively improve the nutrient status of saline soil,and the heavy metal in soil was mainly in residue state,and the risk of heavy metal migration was small.