Effects Of City Green-roof On Environment Of Water And Temperature In Shenzhen

With the acceleration of urbanization, the city with a high density of human settlements has many environmental problems, such as high temperature, drying technology, urban-type flooding, and air pollution. Green roof in their utilization of urban space, increasing urban green space, improving the urban ecological environment and buildings energy efficiency effects, unique advantage of more and more attention and developed rapidly. Effects of urban green roof on water and temperature environment are including three areas:transpiration and water consumption rate of common green roof plants, effects of green roofs cooling humidification, and the role of roof runoff.To provide the theoretical foundation for irrigation of green roof, and then improve blind and extensive irrigation management of green roof now, this thesis had been focused on tests of potted seedlings including four shrubs such as Redlowered Loropetalum,Codiaeum variegatum,Euonymus japonicus,Ligustrum x vicaryi. In the end, we got the water-consuming laws of these plants in different seasons. The results showed that, C. variegatum and L. x vicaryi were summer water-consuming plants, E. japonicus was a water-consuming plant in spring and autumn. The water-consuming characteristics of R. Loropetalum were no significant difference in all seasons. Under controlled water, transpiration rate of four plants with the development of drought stress was progressively decreasing, and in the final stages of drought stress test with the gradual decline in soil moisture, the four plants were reduced transpiration rate very low level, diurnal variation of transpiration water consumption became less marked. L. x vicaryi was the earliest of four plants, had the phenomenon of plant leaves wilt. R. Loropetalum had lower transpiration rate, while in the summer heat under the conditions of water stress was keeping the appearance of branches the smallest, had phenomenon occurs on leaves of plants the latest.Green roof plants through photosynthesis and transpiration, soil water evaporation, made the green roof with cooling and humidification effect on the roof. The average cooling effect of extensive green roof was 8.4%; intensive green roof cooling effect on average 17.6%, the average cooling effect was 2.1 times to extensive green roof. The average humidity in extensive green roof was 20.0%; intensive green roof with 49.8%, the average humidity effect was 2.5 times to extensive green roof. Intensive green roof had the role of cooling and humidification better.Green Roof had the effects on the roof runoff, mainly to reduce roof runoff and the pollutants of runoff both. Common roof runoff coefficient was about 0.89, extensive and intensive green roof runoff coefficients were 0.36,0.21. Green roof can delayed runoff time, the arrival of the peak intensity, and peak greatly reduced. In the determination of runoff pollutants COD, SS, TN, TP found that natural rainfall reached V water requirements, in spring and summer common roof COD, SS pollution was more serious, COD exceeded multiple of 2.77 times in spring, and 3.49 times in summer. Extensive green roof runoff only COD, TN concentration more than V water requirements a little in spring, exceeded only 0.03,0.04 times. The concentration of metal elements in natural water was lower and little change in different seasons. Common roof runoff Fe, Cu, Zn, Pb concentrations were 19.0,9.7, 17.1 and 15.6 times to natural rainfall. In extensive green roof runoff, Fe, Cu, Zn, Pb concentrations were 5.7%,3.0%,5.3% and 4.0% to normal roof runoff. In intensive green roof runoff, Fe, Cu, Zn, Pb concentrations were 5.4%,2.2%,3.4% and 2.9% to normal roof runoff. In comparison with the concentration of metal elements of natural rainfall, in extensive green roof runoff, Fe, Cu, Zn, Pb concentrations were 95.2%, 30.0%,88.1%,59.1% of the natural rainfall. Fe, Cu, Zn, Pb concentrations were 90.4%,22.5%,57.6%,43.8% of natural rainfall in intensive green roof runoff. In general, natural water, common roof runoff, extensive and intensive green roof runoff, pollution from severe to mild in the order of:normal roof> extensive green roof> natural rainfall> intensive green roof.