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With the increase in the rate of urban sewage treatment, sewage sludge production also increased dramatically. Way out of the problem of sludge being exposed in the major cities, how to safely dispose of large quantities of sewage sludge become the most urgent task. Land use is increasingly seen as a positive, effective and promising way of sludge disposal. The method is to avoid the sludge hazardous substances such as heavy metals, toxic organic compounds and other hazards to human health into the food chain prerequisite, the use of sludge contains a large number of nutrients and rich in organic matter to improve soil structure and supply of plant nutrients. This method can effectively use sludge useful resources, but also can solve the problem of sludge outlet. In Xiamen City, for example, on the sewage sludge used as fertilizer for fruit tree research. Xiamen dewatered sludge produced daily about 260m ~ 3 (moisture content 76%), mainly shipped to the East Corfu sludge waste for landfill. Reach because of dewatered sludge landfill requirements, East Corfu dewatered sludge landfill began to reject, there is an urgent demand for new sludge outlet. In this paper, Xiamen City sewage treatment plant sludge main components were tested and analyzed, and the island of Xiamen Shi Wei head after aerobic sewage sludge compost applied grapefruit tree, focus on the heavy metals in the soil, leaves and Migration Characteristics of pulp, Xiamen City, land application of sludge to provide theoretical and technical guidance to ensure the safe use of sludge. The study includes analysis of heavy metals in the sludge in Xiamen city, sludge nutrient analysis and evaluation of resource utilization and stone Wei Head sewage treatment plant sludge fruit fertilizer use test, after application of sludge soil environmental quality assessment, heavy metals in the soil - crop system migration characteristics and migration model. The results showed that: the island of Xiamen Municipal Sludge fruit fertilizer use is feasible. The island city of Xiamen island city than sludge sludge composition is simple, low heavy metal content, TN and TP nutrient content, and TN and TP concentrations rise, there is a greater prospect of resource utilization. Shi Wei Head sewage treatment plant sludge nutrient levels were slightly higher than manure, fertilizer better; sludge as fertilizer fruit after one year, can increase soil TP, grapefruit tree fertilizer, can promote the growth of grapefruit trees, grapefruit increased fruit, fruit prolongation; heavy metals mainly in the surface soil (0 ~ 15 cm) in the migration and accumulation in grapefruit leaves and fruits are also migrated, accumulation, but little impact. Grapefruit leaves strong enrichment of heavy metals in the flesh, leaves the content of heavy metals is much higher than the content of the pulp, the Cr, Cd, Pb, Cu and Ni content exceeding the national food hygiene standards. The concentration of heavy metals in the flesh is quite low, only the Ni content exceeds food hygiene standards. Sludge fertilizer is not available for roots, leafy edible plants of application; sludge before using Ni content needs to be reduced, add the right amount of TK nutrients. Heavy metals in the soil - crop system content and accumulation characteristics of migration studies show that, Cd in soil enrichment ability, Cd in soil that has been contaminated by heavy; downward migration in the soil capacity: Pb> Zn> Hg> Cr> As ~ Cd> Ni> Cu, Pb, Zn downward migration ability, while weak migration of Ni, Cu has a strong table cohesion, mainly at the O ~ 15cm soil. Migration of heavy metals from the soil to the leaves accumulate much larger capacity than the flesh, and its ability to transfer and accumulation of leaves was: Cr> Cu> Ni> Pb> Zn> Cd> As, Cr migration to accumulate leaves the strongest; from the soil The migration to the flesh cumulative capacity: Ni> Cu> Zn> Cr> Pb> As, Ni strongest ability to transfer and accumulation flesh. Cd was not detected in the flesh, indicating Cd basically does not migrate to the grapefruit pulp, severe soil Cd contamination on grapefruit flesh will not cause harm. Sludge fruit fertilizer use that higher levels of sludge in the five elements, Zn and Cu are plants need nutrients in the short term will not cause harm, but long-term application must be monitored; NiFei of application increased soil Cd pollution, improve the leaves of Cr, Ni ability to migrate to the flesh, so when the sludge land use these three elements are present greater potential hazards, the need for long-term tracking and detection. Shortly after the sludge fertilizer, heavy metals mainly in the surface soil (0 ~ 15 cm) in the migration and accumulation, in addition to deep soil (1 5 ~ 30 cm) of Cd content increased significantly, increased pollution, other heavy metals content in not significant, not to soil pollution. In this paper, set pair analysis model after application of sludge soil environmental quality evaluation, the results showed that after one year of sludge application ,0-15cm and 15-30cm soil layer of soil layers are in still clean state, verify the application of sewage sludge security. Of Cd concentration in the soil to determine the maximum limiting factor for municipal sludge land application period, terms of maximum continuous application rate 30 t / (hm ~ 2.a) be applied, the maximum application period is 20 years. After the test data, regression analysis, using Eviews software for model fitting, the establishment of grapefruit trees on soil samples between still and test various heavy metals such as As, Hg, Cu, Pb, Cr, Ni, etc. relational model, heavy metals from soil to the leaves and pulp migration model, you can use the sludge fruit fertilizer after heavy metals in soil - plant concentrations for prediction. Transfer mechanism and statistical analysis will combine to provide a sludge land use research method has practical significance. Finally, the combination of research topics in the expansion of the shortcomings and made recommendations for future research.
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