Study On The Performance And Agronomic Effects Of Hydroxyethylcellulose Modified Biodegradable Polymer In Heavy Metal Contaminated Soil

Although polyacrylate?acrylate-co-acrylamide?can solve the problem of soil drought,it is difficult to degrade and will pollute the soil.In addition,in recent decades,soil heavy metal pollution has become increasingly serious,has become a worldwide ecological problem,the restoration of contaminated soil is imperative.Hydroxyethyl cellulose modified the degradation of biodegradable polymer with good performance and slow-release performance,it can not only improve soil cation exchange capacity,increase content of soil organic carbon and plant production,and material can release of phosphate ions and heavy metal forming metal-phosphate deposits,thus its repair of soil heavy metal has a certain theoretical basis.In this paper,through tomato potting,on the one hand,the degradation performance of hydroxyethyl cellulose modified poly?acrylic acid-co-acrylamide?water retention agent and its practical application effect were studied.On the other hand,the degradation and slow-release properties of hydroxyethyl cellulose-modified biodegradable polymers in simulated heavy metals copper,zinc,cadmium and lead polluted soil,and their effects on soil properties,heavy metal mobility and availability,the mechanism of fixing heavy metal ions in soil was further explored.The main research contents and results are as follows:?1?Tomato pot experiments were used to study its water absorption rate and degradation performance,and the effects on water content,microbiological properties,physical and chemical properties of soil,and tomato plant yield of water-retaining agents with different hydroxyethyl cellulose content.The results show that the addition ofhydroxyethyl cellulose can not only improve the water absorption rate and degradation performance of the water-retaining agent,but also further reduce soil water loss,increase soil microbial carbon and urease activity,and regulate soil pH and electrical conductivity,increase plant yield.When the addition amount of hydroxyethyl cellulose is 20%,compared with the unmodified polyacrylics?acrylic-co-acrylamide?,its weight loss rate,soil moisture content,microbial carbon content,urease activity and tomato yield are increased by 172.70%,39.57%,21.11%,25.56%and 16.49%,respectively,which is more suitable for agricultural application promotion.?2?The biodegradable polymer(PSRF+SAP_HEC-HM)that physically mixed NPK-containing biodegradable polymer(PSRF_-HM)and hydroxyethyl cellulose water-retaining agent(SAP_HEC-HM),and chemically bonded biodegradable polymers(SI-PSRF/SAP_HEC-HM)were studied by tomato pot experiment in contaminated soil with simulated heavy metals of copper,zinc,cadmium and lead.SEM,FTIR,XRD,XPS and EDX were used to characterize the microstructure changes of these materials during the degradation process,and the weight loss rate and sustained release performance of the materials were measured.The results showed that SI-PSRF/SAP_HEC-HM with semi-interpenetrating network structure had better degradation and nutrient slow release performance.The comparative analysis of the corresponding materials in contaminated soil and non-heavy metal contaminated soil shows that heavy metals can inhibit the degradation of polymers in the contaminated soil and the slow release performance of nitrogen and carbon,and promote the release performance of phosphorus.Among them,the degradation of SI-PSRF/SAP_HEC-HM and the slow-release performance of nitrogen and carbon by heavy metals are lower than those of PSRF+SAPHEC-HM.?3?Through the tomato pot experiment,the effects of two hydroxyethyl cellulose modified biodegradable polymers on soil properties,heavy metal mobility,plant characteristics and yield,and heavy metal accumulation in simulated heavy metal contaminated soil were studied.The results show that compared with the blank treatment,the application of different materials in the contaminated soil can effectively improve the soil pH,increase the soil cation exchange capacity?CEC?,and increase the soil microbial biomass carbon?SMBC?,enzyme activity,soil organic carbon?STOC?,the content of Humic acid?HA?,nutrient content of total nitrogen?STN?and phosphorus?SP?,reducing the active form of heavy metals and increasing the stable form of heavy metals.In addition,the application of different biodegradable polymers in contaminated soil can also increase the chlorophyll content,plant height and nutrient content of the plant,reduce the accumulation of heavy metals in the plant and increase the yield of tomato.Among them,the ability of SI-PSRF/SAP_HEC-HM treatment to fix heavy metals and all aspects of plants are better than PSRF+SAP_HEC-HM,which can more effectively inhibit the toxicity of heavy metals to plants.