Green roofs have become a common method to increase water retention on-site in urban areas.However,the long-term water quality of runoff from green roofs is poorly understood.This study evaluated the water quality of ...Green roofs have become a common method to increase water retention on-site in urban areas.However,the long-term water quality of runoff from green roofs is poorly understood.This study evaluated the water quality of stormwater runoff from a regular(non-vegetated)roof,a green roof installed 6 months previously,and a green roof installed 6 years ago in Portland,Oregon.Samples of runoff were taken during every rain event for 10 months,and analyzed for total phosphorus(TP),phosphate(PO_(4)^(3-)),total nitrogen(TN),nitrate(NO_(3)^(-)),ammonia(NH_(3)),copper(Cu),and zinc(Zn).Runoff from the green roofs had higher concentrations of TP and PO_(4)^(3-)and lower concentrations of Zn compared to the regular roof.Average TP concentrations from the 6-year old roof and 6-month old roof were 6.3 and 14.6 times higher,respectively,than concentrations from the regular roof,and average PO_(4)^(3-)concentrations from the 6-year old roof and 6-month old roof were 13.5 and 26.6 times higher,respectively,compared to the regular roof.Runoff from the 6-month old green roof had higher concentrations of TP and PO_(4)^(3-)than the 6-year old green roof during the wet season,but lower concentrations during the dry season.The 6-month old green roof installations where receiving waters are sensitive or impaired may need additional treatment methods to reduce phosphorus levels.As green roofs age,water retention decreases and phosphorus leaching increases during the dry season.展开更多
A novel series of color-tunable single-phased phosphors La1-x-yPO4：xEu3＋/yTb3＋（x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20） was synthesized via microwave-assisted co-precipitation method with d...A novel series of color-tunable single-phased phosphors La1-x-yPO4：xEu3＋/yTb3＋（x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20） was synthesized via microwave-assisted co-precipitation method with diammonium hydrogen phosphate as precipitant. The morphology, crystal structure and photoluminescence properties of the as-prepared samples were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fluorescence spectrophotometer. The results reveal that the as-synthesized samples calcined at 1100 ℃ display spherical morphology with uniform distribution. Upon excitation with 350 nm ultraviolet radiation, the LaPOa：Eu3＋/Tb3＋ phosphors showed a green light peaking at 543 nm assigned to the characteristic 5Da-7F5 emission of Tb3＋ and a red light peaking at 591 nm corresponding to the characteristic 5D0-7F1 emission of Eu3＋ simultaneously. For the Eu3＋/Tb3＋ co-activated phosphors, Tb3＋ acts as an efficient sensitizer to enhance the emission intensity of Eu3＋ ions. The energy transfer mechanism and the emission color tunability of LaPO4：Eu3＋/Tb3＋ have been studied. The results indicate that a color-tunable luminescence（from green to white to red） can be achieved by adjusting the Eu3＋/Tb3＋ doping ratio in the LaPO4 host matrix.展开更多
基金funded by the Oregon Alliance of Independent Colleges and Universities and the Shiley Fellows Fund.
文摘Green roofs have become a common method to increase water retention on-site in urban areas.However,the long-term water quality of runoff from green roofs is poorly understood.This study evaluated the water quality of stormwater runoff from a regular(non-vegetated)roof,a green roof installed 6 months previously,and a green roof installed 6 years ago in Portland,Oregon.Samples of runoff were taken during every rain event for 10 months,and analyzed for total phosphorus(TP),phosphate(PO_(4)^(3-)),total nitrogen(TN),nitrate(NO_(3)^(-)),ammonia(NH_(3)),copper(Cu),and zinc(Zn).Runoff from the green roofs had higher concentrations of TP and PO_(4)^(3-)and lower concentrations of Zn compared to the regular roof.Average TP concentrations from the 6-year old roof and 6-month old roof were 6.3 and 14.6 times higher,respectively,than concentrations from the regular roof,and average PO_(4)^(3-)concentrations from the 6-year old roof and 6-month old roof were 13.5 and 26.6 times higher,respectively,compared to the regular roof.Runoff from the 6-month old green roof had higher concentrations of TP and PO_(4)^(3-)than the 6-year old green roof during the wet season,but lower concentrations during the dry season.The 6-month old green roof installations where receiving waters are sensitive or impaired may need additional treatment methods to reduce phosphorus levels.As green roofs age,water retention decreases and phosphorus leaching increases during the dry season.
基金Supported by the National Natural Science Foundation of China（No.50772016）.
文摘A novel series of color-tunable single-phased phosphors La1-x-yPO4：xEu3＋/yTb3＋（x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20） was synthesized via microwave-assisted co-precipitation method with diammonium hydrogen phosphate as precipitant. The morphology, crystal structure and photoluminescence properties of the as-prepared samples were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fluorescence spectrophotometer. The results reveal that the as-synthesized samples calcined at 1100 ℃ display spherical morphology with uniform distribution. Upon excitation with 350 nm ultraviolet radiation, the LaPOa：Eu3＋/Tb3＋ phosphors showed a green light peaking at 543 nm assigned to the characteristic 5Da-7F5 emission of Tb3＋ and a red light peaking at 591 nm corresponding to the characteristic 5D0-7F1 emission of Eu3＋ simultaneously. For the Eu3＋/Tb3＋ co-activated phosphors, Tb3＋ acts as an efficient sensitizer to enhance the emission intensity of Eu3＋ ions. The energy transfer mechanism and the emission color tunability of LaPO4：Eu3＋/Tb3＋ have been studied. The results indicate that a color-tunable luminescence（from green to white to red） can be achieved by adjusting the Eu3＋/Tb3＋ doping ratio in the LaPO4 host matrix.
