Pollution Evaluation And Phytoremediation Of Lead In Greenbelt Of Changchun

Heavy metal contamination in the urban soil is become increasingly. Especially, lead (Pb) pollution has caused a serious increase in blood Pb levels for urban children. Phytoremediation, which is of features for low cost and environmentally friendly, have been an effective method of contaminated soil remediation, and attracted great attention for domestic and foreign scholars. The screening of the hyperaccumulator is the key of phytoremediation, which is also the difficult point of phytoremediation. On the basis of exploration on the mechanism of urban soil lead contamination, the growth responses and accumulation characteristics of 32 common ornamental plants, including Salvia splendens Ker-Gawler, Spiraea salicifolia L., Hosta plantaginea Aschers, Commelina communis L., Iris lactea, Saponaria officinalis, Dianthus chinensis L., Cosmos bipinnatus Cav., Phlox drummondii Hook., Begonia semper. norms, Antirrhinum majus L., Calendula officinalis, Pelargonium hortorum, Amaranthus tricolorL., Weigela florida cv.Red Prince, Mirabilis jalapa Linn., Althaea rosea, Impatiens balsamena. L, Zinnia L., Tagetes erecta L., Dahlia pinnata Cav., Hydrangea macrophylla (Thunb.)Seringe, R chinensis, Canna indica, Pelargonium hortorum Bailey. var. vareigata, Coleus blumei, Pelargonium, Petunia hybrida Vilm, Tagetes patula L., Sedum spectabile Boreau, Clivia and Rhizoma Belamcandae, were studied through the sand culture, hydroponic culture and soil culture experiment. The ornamental species, which is suitable to growth in northern city of China and has high Pb enrichment ability, were screened out. This aimed at exploring the suitable phytoremediation technology of Pb contaminated soil using ornamental plants. The main results are summarized as follows:1. Take Changchun city as an example, the physical and chemical properties and Pb pollution evaluation of surface urban soils positioned were carried out. The results showed that the physical properties of urban soil were slightly worse, and the chemical indicators were in general at a high level. Most of the soils were benefit to the normal growth of plant roots. The Pb content of urban green earth soil in Changchun city varied widely, ranged from 18.7-125.8 mg/kg with an average of 57.1 mg/kg. With lead pollution index and accumulate index method, the Pb content in urban green earth soil of Changchun city generally between the light and moderate pollution levels.2. Both sides of the main street through 14 of the 12 species leaves the determination of lead, calculated using the single pollution index of the quality level of atmospheric pollution index evaluation showed that:the use of cluster analysis,12 species most capable of lead uptake Is Spiraea, followed by leaf boxwood, pine, Petunia and Coleus; while the weakest absorption of lead is the elm trees, privet, Ligustrum leaf, Eight Sedum. Use of single pollution index level of air quality assessment method, Hongqi Street, Changchun City, and comrades Street atmospheric lead pollution to serious pollution, the railway station north exit of the heavily polluted area are lead, Exhibition Avenue has reached moderate pollution, the people are light Avenue and South Lake road Degree of contaminated areas, pollution is Kaixuan, forward Avenue and Yan'an road.3. Adsorption isotherms of Pb2+ onto turfgrass, cattle manure and leaves, its HLA and HLM added in urban soils show that the adsorption capacity data increases at the same increasing Pb2+ concentrations of equilibrium. On the conditions of Identical initial concentration, he adsorption capacity data is following:leaves>cattle manure>turfgrass. On the conditions of Identical initial concentration, the adsorption capacity data is following: HLA>HLM>organic matters. The adsorption capacity data is well correlated by both Langmuir and Freundlich isotherm models, attain remarkable linear correlation. As the same as the regularity of adsorption isotherms, the adsorption capacity data is the same following:HLA>HLM> organic matters.4. Seed germination test results show that the tested plants flowers on lead tolerance Iris seed is the strongest, followed by zinnia seeds and seeds of Mirabilis, patience is the worst seeds Rudbeckia hirta. Compared with the control patula and zinnia root length decreased by 66.2%,55.1%, down 85.2% Rudbeckia hirta. That the patience of the seed radicle of the strongest lead is patula and zinnia flowers, the weakest is Rudbeckia hirta. Pb stress on seedling growth after germination studies confirm the tolerance of plant roots on the ability of lead of four to Iris, Camellia impatiens, zinnia, and maidenhair, the strength of the order of Iris> Camellia impatiens> Zinnia> maidenhair.5. Results from the hydroponic experiment showed that the highest Pb contents in shoot of Begonia semperflorens, Zinnia elegan, Mirabilis jalapa. and Hosta ventricosa reached the critical standard of Pb hyperaccumulating plant. And the Pb content and bioaccumulation coefficient of the 4 ornamental plants was significantly higher than that of the else tested ornamental plants. Among the ornamental plants tested, the highest Pb translocation factor of Begonia semperflorens, Zinnia elegan, Mirabilis jalapa., Hosta ventricosa and Commelina communis were above 0.8. Meantime, the TF of Zinnia elegan was still higher for 200 mg Pb/L than for 100 mg Pb/L. These results indicated that Begonia semperflorens, Zinnia elegan, Mirabilis jalapa., Hosta ventricosa and Commelina communis have stronger tolerance under Pb stress and higher ability of enrichment and translocation for Pb.6. Results from soil culture experiment showed that:1) the tested plants flower, Mirabilis, hollyhock, impatiens Camellia Begonia and the maximum shoot Pb concentrations are more than 100 mg/kg, the order of Mirabilis> hollyhock> Begonia> Camellia impatiens, and they shoot Pb content and Pb enrichment factors were significantly higher than other plants.2) for the test in the flowering plants, Pb transfer coefficient than the maximum value of up to 0.45 with Mirabilis, Silver geranium, Geranium Phnom Penh, eight treasures Sedum, while they are treated with high concentrations of the transfer coefficient of Pb were significantly higher than the low concentration The. Shoot from the repair capacity of flower plants of view, the repair of Begonia efficiency and the highest total Pb migration, followed by Mirabilis, hollyhocks, camellias impatiens, marigold, zinnia, but did not exceed 0.2%.3) The above study results, Mirabilis not only has a strong tolerance to Pb stress, and with high capacity and transfer capacity of Pb enrichment, remediation of polluted soil in Pb has great application value. Shoot from the repair capacity of flower plants of view, Begonia, Mirabilis, zinnia, impatiens on Pb contaminated soil Camellia good repair potential, hollyhock, impatiens, and marigold Camellia repair potential should not be ignored.In summary,4 ornamental plants with feature of Pb hyperaccumulation potential, that is, Begonia semper. norms, Zinnia L., Mirabilis jalapa Linn. and Hosta plantaginea Aschers, were found through systematic study the growth responses and accumulation characteristics of Pb for the 32 common ornamental plants suitable planting in Changchun city. The Pb concentrations for the above 4 ornamental plants were all over 1000mg/kg, and the enrichment factors were all greater than 1. This proved that the screen of the ornamental plants with strong patience and high accumulation ability to Pb is feasible. Thus, it is suitable for the restore of Pb contaminated soils using the ornamental plants. At the same time of reducing the Pb content of the soil, the urban environment is beautified. This provides a new mode for the remediation of Pb contaminated soils in Changchun city.