Selection of xerophils and drought tolerant plants is highly crucial in green roof techniques in the drought prone regions of Northwest China. In this study, the thermal performance under the natural conventional climate in summer was analyzed using a self-made simulation experimental platform through comparison of the internal surface temperature with and without green roofs. The distribution frequency of internal surface temperature was investigated by dividing internal surface temperature into several ranges. Statistical analysis showed that the frequency of internal surface temperature lower than 33 • C for green roofs was 91.8%, about 1.09 times higher than that for non-green roofs, and that the sum of internal surface temperature exceeding 35 • C was about one third of that for non-green roofs. The results proved that green roofs have a significant insulation effect. Moreover, the thermal insulation property of green roofs had a strong positive relation with outside temperature. The thermal insulation characteristic was improved as the outdoor temperature increased, additionally, it had a better insulation effect within two hours after irrigation.
a b s t r ac tThe vertical hard revetment can cause the disturbance in river flow with the results of destroyed features, degraded biodiversity, decreasing self-purification ability and deteriorated water quality. The current work is focused on the application of prefabricated porous concrete template covered on widespread vertical hard revetment for improving water purification, increasing biodiversity and decreased negative impact of hard concrete revetment to river quality. Six kinds of porous concrete with different void ratio, aggregate size and water cement ratio were prepared to investigate the compressive strength and water purification properties. A river simulator device was used to determine the water purification capacity of the porous concrete in flowing condition. Water quality purification mechanism of porous concrete was discussed thoroughly by the analysis of microbial community diversity. Results show that the compressive strength and water purification ability of porous concrete were higher when the void ratio, size of the aggregate material and water cement ratio were 30%, 10-20 mm and 0.3, respectively. Under the flow velocity of V = 0.03 m/s and hydraulic retention time of 6 d, the removal rates of M 2 biofilm for chemical oxygen demand (COD Mn ), ammonia nitrogen (NH 3 -N), nitrate nitrogen (NO 3 -N), total nitrogen (TN) and total phosphorus (TP) were 59.21%, 74.07%, 54.25%, 55.47% and 62.90%, respectively. Findings reveal that prefabricated porous concrete was efficient for river water purification. Porous concrete templates can be attached to a large number of microorganisms.
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