Synthesis,Characterization Of Polyacrylamide And Fluorescence-labeled Polyacrylamide And Their Improvements On Soil

In agriculture,excessive use of chemical fertilizers may lead to soil degradation or even consolidation.Soil consolidation will reduce the water and fertilizer conservation capacity,reduce the air content in the soil,and then affect the absorption of nutrients and respiration by the crops,resulting in a reduction in production,even worse,affect the soil p H,which make cultivated land uncultivated.In order to solve the problem of soil consolidation,linear polyacrylamide(PAM)and fluorescence labeled linear polyacrylamide(Fl-PAM)with different molecular weight were stably synthesized in this paper.PAM was applied to soil to study the adsorption by the soil,and its effect on water and fertilizer conservation capacity,soil bulk density,soil water-stable aggregates and maize plant growth.The possibility of using Fl-PAM as a marker to visualize the migration of PAM in soil was also explored,and the acute toxicity of PAM to aquatic organisms was investigated.The main contents of this thesis are as follows:(1)A series of PAM(PAM-1,PAM-2 and PAM-3)with viscosity average molecular weight about 1 million,3 million and 5 million are synthesized through free radical solution polymerization.A series of Fl-PAM(Fl-PAM-1,Fl-PAM-2 and Fl-PAM-3)with viscosity average molecular weight about 1 million,3 million and 5 million are synthesized through free radical solution copolymerization.The designed synthesis process is simple and efficient,and the viscosity average molecular weight of the polymer can be controlled.(2)The indoor simulation experiments show that,the adsorption of PAM by soil is in accordance with the Langmuir adsorption model,which is monolayer adsorption,and the adsorption process is relatively easy.The theoretical saturated adsorption capacity of PAM-1and PAM-2 by soil is 151.5 mg/g and 666.7 mg/g,respectively.Applying PAM to soil can conserve water and fertilizer,and the effect increases with the PAM concentration increased.If used at a certain molecular weight and application rate,PAM could effectively reduce soil bulk density and increase the content of soil water-stable aggregates.When the application rate of PAM-2 is 0.5 g/kg,the soil bulk density is the lowest,about 1.03 g/cm~3,which is10.4%lower than the blank group.When the application rate of PAM-3 is 50 mg/kg,the content of soil water stable aggregates is the highest,about 56.2%,which is 32.8%higher than the blank group.In addition,PAM can promote the growth of maize plants.When the application rate of PAM-3 is 25 mg/kg,the dry weight of corn straw is 15.2%heavie than the blank group.According to the results of acute toxicity test of fish,it is found that PAM aqueous solution is non-acute-toxicity to organisms.(3)Because Fl-PAM contains fluorescent groups,under the irradiation of ultraviolet light,it can emit green fluorescence,which can be seen by our eyes.It is beneficial to the visualization of PAM migration in soil.The experimental results show that,PAM can migrate from the soil surface to the bottom with the water.The visualization that the migration and distribution of PAM in soil could be preliminarily realized.