Research On The Improvement Of The Garden Soil Of Fuzhou City Through Trees Cut Waste And Municipal Sludge

The waste caused by pruning landscape plants grows increasingly and the harmless recycling of the municipal sludge becomes one of the crucial environmental problems for China to deal with.Besides,the hardening and malnutrition of soil are mainly responsible for the poor growth of plants around the viaducts in urban area.This research makes use of trees cut waste from the pruning of common plants in Fuzhou city to compost,and utilizes the coal ash to passivate the heavy metals in sludge so as to ensure the maturity conditions which are suitable for the compost of Fuzhou’s common trees cut waste and confirm the best proportion and time of the passivation of sludge by coal ash.What’s more,this research also studies the promotion of garden yellow soil and the cultivation of Ruellia brittoniana through utilizing the compost of trees cut waste and the passivated sludge in an effort to provide the theoretical basis for the study of lightweight nutritive soil.The main results are as follows:1.Impact on the content of heavy metals in sludge by applying coal ash and phosphogypsumThe coal ash can significantly decrease the content of effective Fe,effective Mn,effective Cu,effective Ni,effective Pb and effective Cd in municipal sludge.With the increase of coal ash in municipal sludge,the content of effective Fe and effective Mn reduces gradually.When the proportion of sludge,coal ash,phosphogypsum is 1:2:0.003,the content of effective Fe in sludge bottom at 94.89mg/kg.In addition,the content of effective Cu,effective Ni,effective Pb and effective Cd in sludge with different treatments being remarkably lower than the national standard of agricultural sludge cannot have a toxic influence on plant.When the proportion of sludge and coal ash is 1:3,the content of effective Zn in sludge peaks at 270.45mg/kg,which is remarkably higher than the natural background value of national standard of agricultural sludge.When the proportion of sludge and coal ash is 1:2,the effect of passivation is more remarkable.After the eight hours of passivation of municipal sludge by coal ash,the effect reaches at the best with the content of effective Cu,effective Zn,effective Fe,effective Mn and effective Cd touching the bottom.Yet,the result of passivation of municipal sludge through applying phosphogypsum is indistinctive.2.An analysis of key index parameters during the composting process of trees cut wasteAs the content of organic matter decreases constantly during the composting process,the content of total nitrogen,total phosphorus,total potassium and total nutrients goes upward and then falls.What’s more,the content of total nitrogen,total phosphorus,total potassium and total nutrients reaches the highest in the 35th day.When the compost is in the 10th day,the temperature peaks at 50℃ and then remains stable.As for the pH value,it rises at first and then decreases gradually.In the 30th day of the compost,the pH value peaks at 9.33 and then tends to be steady in the 35th day,which is suitable for the environmental conditions of the compost of garden plants.The water content shows a trend of decline during composting process.In the 35th day of compost,the water content decreases fastest.In terms of C/N ratio,it decreases to 19.50 which has reached the requirements scope of decomposition(15-20:1)in the 35th day.Besides,The surface of the compost presents milky white and is not smelly.This means when the environment temperature varies from 45℃ to 49℃ with the average temperature of 48℃,the C/N ratio of 19.50 and the pH value of 9,the compost of trees cut waste has been decomposed and the nutrient contents of total nitrogen,total phosphorus,total potassium and total nutrient is 1.28%,1.73%,1.95%and 4.95%respectively,and can be used as the raw materials of lightweight nutritive soil for landscape plants growth.3.Impact on the improvement of garden soil and the nutrient absorption of Ruellia brittoniana through the compost of trees cut waste and the passivated sludgeThe compost of trees cut waste and the passivated sludge are conducive to the increase of micronutrient contents in soil and plant.In addition,the highest content of effective Cd,effective Pb,effective Cu,effective Zn and effective Ni in soil with different treatments are lower than the classification standard of heavy metals pollution in agricultural soil of Fujian province,which cannot affect the normal growth of plants.The content of total Ni,total Cu,total Mn and total Zn in Ruellia brittoniana significantly increases as the soil is only added with the passivated sludge.Besides,When the proportion of soil and passivated sludge is 1:3,the content of the Cu in Ruellia brittoniana’s aboveground part peak at 23.54mg/kg,which exceeds the toxic concentration of the Cu and leads to the retardation of the normal growth of plants.Compared with the group only being treated with the passivated sludge,the treatment with both the compost of trees cut waste and the passivated sludge in soil is able to lighten the harm to plants.The compost of trees cut waste and the passivated sludge remarkably increase both the content of macronutrients in the soil and the content of dry biomass of plant,which is conducive to the growth of plants.Moreover,the content of total nitrogen and total phosphorus in the experimental groups grow more evidently than that of the control group.When the proportion of soil,passivated sludge and the compost of trees cut waste is 1:1:3,the content of effective nitrogen in soil peaks at 273.89 mg/kg,which is 317.76%,29.87%,5.56%and 138.89%higher than that of the treatment with the proportion of soil and passivated sludge being 1:1,that of the treatment with the proportion of soil,passivated sludge and the compost of trees cut waste being 1:1:1,that of the treatment with the proportion of soil,passivated sludge and the compost of trees cut waste being 1:1:2,that of the treatment with the proportion of soil and the compost of trees cut waste being 1:3 respectively.Generally,when the proportion of soil,the passivated sludge and the compost of trees cut waste is 1:1:3,the matrix is the most beneficial to promoting the nutrient contents of garden soil and the growth of landscape plants around the viaducts.