关键词: 城市污泥, 构树, 植物修复, 重金属, 养分

Abstract: Broussonetia papyrifera, an important fast-growing economic tree species in China, has the advantages of strong adaptability, high-biomass, and high bioconcentration of heavy metals. Sewage sludge contains a great deal of nutrients and heavy metals. Planting B. papyrifera with sewage sludge can achieve the goals of sewage sludge remediation as well as resources production of B. papyrifera. A pot experiment was conducted to investigate growth, uptake and accumulation of nutrient and heavy metal in different organs (root, stem, leaf) of B. papyrifera, with treatments of control (lateritic red soil), 50% sewage sludge (mixed substrates of 50% sewage sludge and 50% lateritic red soil based on weight) and 100% sewage sludge. The comprehensive evaluation of capacity of uptake and accumulation was also carried out by principal component analysis and membership function. The results showed that B. papyrifera could grow normally in both 50% and 100% sewage sludge substrates, with higher plant height and biomass than that in the control, especially in 100% sewage sludge substrate. The quality index in 100% sewage sludge substrate (1.02) was 4.3 times and 2.4 times as that of the control and 50% sewage sludge substrate, respectively. The content of N in different organs and P in stem increased significantly in both 50% and 100% sewage sludge substrates. The content of K in stem and leaf was significantly decreased in 100% sewage sludge substrate, which were significant lower than that of control. The uptake of heavy metals such as Cu, Zn, Pb, Cd, Ni for B. papyrifera were mainly through roots. There was positive correlation between the content of heavy metals in root and sewage sludge ratio. The content of Pb and Cd in leaves were lower than the limit value of Hygienic Standard For Feeds (GB 13078-2017). The capacity for absorption and accumulation of Cd was better than that of other heavy metals. Compared with the control, rootretention rates of Zn, Pb and Cd significantly increased in both 50% and 100% sewage sludge substrates (57.8%-85.8%), while Cu and Ni significantly increased in 100% sewage sludge substrate (67.5% and 74.8%). Nutrient and heavy metal accumulations in total plant in both 50% and 100% sewage sludge substrates were significantly higher than that in the control, with 100% sewage sludge substrate being significantly higher than that in 50% sewage sludge substrate. Compared with 50% sewage sludge substrate, the increment rates of nutrient and heavy metal accumulations in different organs as well as total plants in 100% sewage sludge substrates were greatly increased. The rank of comprehensive evaluation scores of adaptability, element uptake and accumulation was in an order: 100% sewage sludge substrate (0.848) > 50% sewage sludge substrate (0.344) > control (0.080). With good adaptability to sewage sludge, B. papyrifera could grow normally in sewage sludge andeffectively absorb and fix nutrients and heavy metals. It is feasible to plant B. papyrifera into the sewage sludge for remediation of sewage sludge and resource production.

Key words: sewage sludge, Broussonetia papyrifera, phytoremediation, heavy metal, nutrient