| Nowadays,the amount of urban sludge grows rapidly.The sludge contains numerous nutrients and organic matter.Owing to the sewage produced by industrial production,urban sludge is mixed up with a lot of harmful substances.The treatment of sludge is roughly divided into land-use method,incineration and landfill.Land-use method is divided into urban landscaping,agricultural utilization and land restoration.The sludge is rich in organic matter and nutrients.So it is good fertilizer.The application will improve the soil fertility and increase the activity of soil enzymes,which contribute to the growth of plants.The soil remediation could improve its physical and chemical properties,which is conducive to ecological restoration and preserving soil and water.Because of the characteristic that urban sludge has nutrient element,we could improve soil and water conservation capacity of sandy grassland and soil structure,and restore vegetation as well as microbial activity by applying sludge.At the same time,unlike agricultural utilization,it avoids bringing the untreated and completely harmful substances to the food,which could do harm to human health.This thesis researches on soil respiration and DOC.Soil respiration is of great significance in the global ecosystem,so it is necessary to study on it.What is the effect of sludge application on soil respiration? There are rare researches at present.And the result is uncertain to a large degree.Therefore,I’d like to provide data support and theoretical basis for future research on sandy grassland through the determination of various physical and chemical indicators of soil.And the analysis of DOC contributes to deeper understanding on global carbon cycle.The factors that affect DOC are complex and many problems need deeper study.Therefore,in this thesis,I only select temperature,water content and other indicators to analyze,trying to provide some help for future research.Through the study of soil respiration,I find that sludge application has a positive effect on soil respiration.When temperature is similar,the increase of soil moisture content also contributes to soil respiration,which indicates that the application of sludge has a greater role in increasing the biomass of sandy grassland.While the growing rate of plant number is the smallest.It indicates that the effect of sludge application on the growth of plants is more obvious than that of increasing the number of plants.Through the study of DOC,I find: the content of protein compounds in the sludge is relatively high.Soil moisture content has a significant correlation with DOC.P is 0.047,which is less than 0.05.Correlation is 0.521,which is between 0.3 and 0.7,so it belongs to moderate correlation.After applying sludge,the soil respiration rate decreased significantly.Soil nutrient,especially the content of N,has a positive effect on soil DOC. |
