Study On Application Of Aged Refuse As Sward Soil

As an affordable and environmentally acceptable method, sanitary landfill continues to be primary in solid waste disposal in China. Currently, without any pretreatment, more than 80% of municipal solid waste has been deposited into landfills, and there will be nearly 70% of all solid waste projected to be accepted in landfills in the next 20 years.As a result, it has reached the design capacity in most of the landfills.However, with the rise of land price in the suburbs, as well as the advance of standardization requirements in landfill,it is more and more difficult to build a new refuse landfill.Therefore, a more economical and effective recovery technology of aged refuse will be needed to actualize the continuable use of landfill.Except plenty of organic contaminants and heavy metals, aged refuse also contained abundant essential plant nutrient elements, such as nitrogen, phosphorus,kalium and so on.After improved,it can be safely used as vegetated soil.In recent years, lawn production has developed rapidly. However, it still adopts the traditional production methods in much of our country. In this way, lots of farming soil with high quality is selected to produce the sward. When taking the sward, it will shovel off 3-5 cm soil,and after taken the sward for some times,it will result in serious soil desertification.For a country with a lacking soil resource, it is not a wise choose to produce the sward in this traditional way.Therefore, aged refuse was studied as vegetated soil for sward production in the present research.Above all,the basic physical-chemical properties were determined. Secondly, the tolerant grass to aged refuse was identified by comparing the growth and chlorophyll content of three grass seedlings common in North, and its tolerant mechanism was further investigated.Thirdly, the effects of the particle-size distribution of aged refuse on the physiological response of the tolerant grass seedling were discussed.At last, several additives were taken to improve the aged refuse in the proper way, and we select an optimizing formula for the sward production.As the results showed that, the pH value of aged refuse was slightly acid, which was very similar to the ordinary lawn soil's.Humus,effective N and P were abundant in aged refuse, which was 1.36-,2.25-and 1.13-fold of the ordinary lawn soil, respectively. Soluble salt content in it reached 15-fold of ordinary lawn soil.And Total Cr contents in the refuse leaching were beyond maximum values of selective control items of water quality in urban recycling water used in greenland irrigation. Moreover, the contents of humus, effective N and P, soluble salt and heavy metals showed a negative correlation with the particle-size distribution of aged refuse.After the selection experiment of tolerant grass seedling to aged refuse, it was found that, for higher leaching concentration or longer treatment duration,all three grass seedlings showed significant growth inhibition;for lower leaching concentration and shorter exposure time. Festuca arundinacea presented the least inhibition.On the other hand, the chlorophyll of Lolium perenne L. and Poa annua were obviously inhibited, but the inhibition only presented in 100% treatment of Festuca arundinacea. Therefore, Festuca arundinacea was selected as the tolerant grass seedling to aged refuse.According to the study on the tolerance mechanism of Festuca arundinacea,it indicated that for lower leaching concentration or shorter exposure time, antioxidant enzyme activities were induced, and no obvious oxidative damage was observed. But prolonging treatment duration, SOD and CAT activity was significantly inhibited, and lipid peroxidation and protein oxidation occurred. Howther, POD activity was still induced, which also showed the tolerance of Festuca arundinacea to aged refuse.By analyzing the effects of particle-size distribution of aged refuse on the physiological response of Festuca arundinacea, it showed that compared with the larger particle-size treatments, the aged refuse in smaller particle-size led to a more serious growth inhibition of Festuca arundinacea; Moreover, SOD activity was only induced in the larger particle-size samples, POD activity was induced in all treatment, and CAT activity was all inhibited. As a result, it presented more significant oxidation damage in small particle-size treatment.After the growth experiment of Festuca arundinacea with aged refuse as vegetated soil,it suggested that Festuca arundinacea can not grow on the 900-1μm, and the inhibition effect showed a negative correlation with the particle-size of aged refuse.In view of the effect of the particle-size distribution on the contamination contents in aged refuse and its water permeability and retentivity, aged refuse was improved by adding some additives,and the optimizing formula was determined that the proportion of large particle-size, small particle-size aged refuse, hogwash and coal fly ash was 36%,12%,12%and 40%of the mixture respectively.In order to evaluate secondary pollution of improved aged refuse, leaching of heavy metals in it were determined.The results showed that the contents of Cu,Cr, Pb and Cd all met the environmental quality standards for surface water (GB3838-2002) and ground water (GB/T 14848-93),so the improved aged refuse will not cause such heavy metals pollution to surface water and ground water.