Study On The Law Of Nitrogen Transfer And Transformation And The Effect Of PAM On Nitrogen Conservation In The Soil Improved By Sludge

With the increase of sludge output in sewage treatment plants,the problem of sludge treatment and disposal is increasing day by day.At this stage,most of the sludge in sewage treatment plants in our country can not be properly treated and disposed,resulting in the increasingly serious problem of secondary environmental pollution.At the same time,the proportion of desertification land in China is relatively high,and the task of desertification control is arduous.The efficiency of traditional desertification control methods is not high,which is greatly limited by natural and economic conditions.It is found that the reasonable application of sludge to the treatment of desertified soil is of great significance to the choice of sludge disposal way and the treatment of desertified soil.In this study,the concept of "treating wasteland with waste and sediment together" was applied,combined with the previous research results of the research group,under the condition of the best sludge mixing ratio(20%),through the soil column simulation experiment under the constant rainfall intensity,the leaching risk of different nitrogen and the law of nitrogen transfer and transformation in the mud sand composite medium were analyzed,and the PAM method was used for soil nitrogen conservation to optimize PAM The best dosage to reduce the loss of nitrogen.1)the results of water quality analysis of the leaching solution of the improved sandy soil show that the nitrogen content in the soil that can be absorbed and utilized by plants will gradually decrease with the leaching of simulated rainfall,that is,the nitrogen in the soil has a higher leaching risk,the main form of nitrogen leaching is nitrate nitrogen,and the risk has a certain sustainability;with the leaching in OK,the p H of the leaching solution decreased to a certain extent,indicating that the hydrolysis and acidification reaction took place in the soil.In the correlation analysis,it is found that the p H and COD of the leaching solution have a negative correlation with the dynamic change of the leaching times,while the nitrite nitrogen and cod have a significant positive correlation with the dynamic change of the leaching times.NH4-N content decreased with the leaching of simulated rainfall.It was found that nitrification and denitrification continued in soil solution.By calculating the amount of nitrogen leaching,it is found that nitrate nitrogen is the main form of nitrogen leaching,the amount of leaching accounts for 3.63% of the total amount of nitrogen,followed by ammonia nitrogen,the total loss of leaching conversion is 1.32%,the lowest amount of nitrite nitrogen leaching is 0.499%.2)The analysis of physical and chemical properties of each layer of the improved sandy soil shows that the mixed medium with 20% sludge has the risk of hydrolytic acidification reaction,which will reduce the p H value of each layer to a certain extent.The mixed medium with sludge can greatly increase the content of soil organic matter,and the content of soil organic matter in the surface layer(1-2 × 3)gradually decreases with the increase of rainfall times In the analysis of nitrogen content,it was found that the incorporation of sludge could effectively increase the nitrogen content in the subsoil.According to the analysis of the comprehensive experimental results,it can be preliminarily judged that the p H value in the soil layer of 20-30 cm is less affected by sludge,and the content of organic matter and nitrogen in the soil layer is relatively high,that is to say,the third soil layer is the best planting soil layer.3)The results show that compared with other nitrogen retention materials,polyacrylamide has good nitrogen retention effect and less application amount.In the study of the nitrogen retention capacity of polyacrylamide,the law of nitrogen accumulation and loss in different PAM dosage groups is: CK > 0.1% PAM > 0.075% PAM > 0.01% PAM > 0.025% PAM.When PAM dosage is too small,that is,the dosage is less than 0.025%,it does not have a good nitrogen retention effect.When the amount of PAM is more than 0.025%,the amount of nitrogen leaching will increase,which indicates that excessive PAM can inhibit the ability of soil nitrogen retention to a certain extent.Therefore,the best dosage of PAM is 0.025% in the process of nitrogen retention.Compared with the reference sample,the leaching loss of total nitrogen is reduced by about 38%.The amount and times of nitrogen leaching are in accordance with the logarithmic curve(R2 > 0.99).The simulation curve has certain significance for predicting the amount of nitrogen leaching in the future.