Reuse Of Aged Refuse As Greenery Substrate

With high pH value, urban soil in Shanghai lacks organic matter and nutrient elements and is unfavorable to the growth of plants. Meanwhile, aged refuse, available at the refuse landfills and dumping sites, has been proved to be a high quality soil-like substrate for the growth of plants, due to its rich contents of nutrients. Hence, in this work, the aged refuse was used as the plant growth substrate, together with the soil or alone.Risk assessment of aged-refuse in greenery reuse was conducted, in terms of aged-refuse heavy metal showering and plant seed emergence experiments. A comparison between the concentrations of heavy metal in the showering liquid of the aged refuse and limits in the National Underground Water Quality Standard was made and the potential pollution risk was thus drawn. Meanwhile, seed emergence inhibition using the aged refuse was explored and comprehensive pollution index assessment was observed, showing that the aged refuse and its mixed sustrates with soil may not pose potential risk to the underground water and surrounding environments where the aged refuse was used. 40-50% of aged refuse in the soil and aged refuse mixture seemed to be the optimum condition subjected to the plant seed emergence experiment.Triple mixed substrate of aged refuse—composted sludge—soil and double mixed substrate of aged refuse—soil were made and used for the potted growth experiments. Physiochemical properties of mixed substrates with aged refuse and sole soil were compared. Effects of different aged refuse proportion on plant growth, absorption of inorganic nutrient elements by plant and heavy metal accumulation in plant were focused. Presence of aged refuse can make plant absorb more nutrient elements to facilitate the plant growth. The maximum biomass, chlorophyll contents and TOC in the plants of test occurred at 75% of aged refuse in the double mixed substrate, while 45%-55% in triple mixed substrate.On-site plant survey at Shanghai Refuse Landfill was conducted. It was found that wild herbal plants dominated in the landfill. In units with 6-7 years landfill age, Humulus scandens, Chenopodium album and Solidago canadensis L. were observed to be the main advantageous plant community, while in units with 9-10 years landfill age, Humulus scandens, Cynodon datylon and Sctaria, viridis form advantageous plant community.