Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization ...Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollu- tion is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollu- tion load of urban runoff and summarizing the law and character- istics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the applica- tion of BMPs (best management practices). It is a fresh method- ology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff..展开更多
The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 20...The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.展开更多
Like the hard surfaces of streets and sidewalks in an urban environment, the vertical and horizontal surface area on the outside of urban buildings contributes to the constant heating of large cities around the world....Like the hard surfaces of streets and sidewalks in an urban environment, the vertical and horizontal surface area on the outside of urban buildings contributes to the constant heating of large cities around the world. However, little is done to design this surface to benefit the public sphere. Instead, the facade of a building performs either as a component that focuses only on the quality of comfort for interior occupants, while ignoring effects on the exterior of the building, or as an identifiable aesthetic for the building＇s owners, This essay proposes the rethinking of the building facade as a steward of outdoor pedestrian welfare, and the conception of public health as an added function of the building envelope- a concept that may fall into the jurisdiction of public works. If the huge total surface area of a city＇s buildings is thought of as part of the city＇s infrastructure, then its public contribution may not only make outdoor areas comfortable, clean, and enjoyable, but also help to alleviate the bigger problem of rising temperatures in cities.展开更多
The North China Plain(NCP) has recently faced serious air quality problems as a result of enhanced gas pollutant emissions due to the process of urbanization and rapid economic growth.To explore regional air pollution...The North China Plain(NCP) has recently faced serious air quality problems as a result of enhanced gas pollutant emissions due to the process of urbanization and rapid economic growth.To explore regional air pollution in the NCP,measurements of surface ozone(O3),nitrogen oxides(NOx),and sulfur dioxide(SO2) were carried out from May to November 2013 at a rural site(Xianghe) between the twin megacities of Beijing and Tianjin.The highest hourly ozone average was close to 240 ppbv in May,followed by around 160 ppbv in June and July.High ozone episodes were more notable than in 2005 and were mainly associated with air parcels from the city cluster in the hinterland of the polluted NCP to the southwest of the site.For NOx,an important ozone precursor,the concentrations ranged from several ppbv to nearly 180 ppbv in the summer and over 400 ppbv in the fall.The occurrence of high NOx concentrations under calm conditions indicated that local emissions were dominant in Xianghe.The double-peak diurnal pattern found in NOxconcentrations and NO/NOx ratios was probably shaped by local emissions,photochemical removal,and dilution resulting from diurnal variations of surface wind speed and the boundary layer height.A pronounced SO2 daytime peak was noted and attributed to downward mixing from an SO2-rich layer above,while the SO2-polluted air mass transported from possible emission sources,which differed between the non-heating(September and October) and heating(November) periods,was thought to be responsible for night-time high concentrations.展开更多
Land surface temperature (LST) of Beijing area was retrieved from Landsat TM thermal band data utilizing a radiative transfer equation and the urban heat island (HUI) effects of Beijing and its relationship with land ...Land surface temperature (LST) of Beijing area was retrieved from Landsat TM thermal band data utilizing a radiative transfer equation and the urban heat island (HUI) effects of Beijing and its relationship with land cover and normalized difference vegetation index (NDVI) were discussed. The result of LST showed that the urban LST was evidently higher than the suburban one. The average urban LST was found to 4.5 ℃ and 9 ℃ higher than the suburban and outer suburban temperature, respectively, which demonstrated the prominent UHI effects in Beijing. Prominent negative correlation between LST and NDVI was found in the urban area, which suggested the low percent vegetation cover in the urban area was the main cause of the urban heat island.展开更多
The traditional methods of storm sewers design must be supplemented by a precise and systematic analysis of the consequences of urbanization. This will ensure the reduction of the negative effects of urbanization in t...The traditional methods of storm sewers design must be supplemented by a precise and systematic analysis of the consequences of urbanization. This will ensure the reduction of the negative effects of urbanization in the process of stormwater sewer system normal functioning. As the urbanization of rural areas has been in constant progress, there was a need for the development of infrastructure system of urban planning documents that accompany urbanization. Surface storage appears to be one of the solutions that can have positive effects on the consequences of rapid urbanization in terms of preserving water quality of recipients, as well as opportunities to reduce the diameter of drain pipes downstream of surface storage. The necessary investments do not exceed the values of conventional technologies and procedures that are used for this purpose. The restriction of application of these methods is reflected in the limited space, especially in the smaller urban areas, where urbanization was a sudden and uncontrolled process. Future planning documents must contain alternatives like these, while the reservation of required space must be included in the planning documents in which the treatment of further development of the city will be found.展开更多
基金Key Program of Natural Science Foundation of China(No. 40576024).
文摘Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollu- tion is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollu- tion load of urban runoff and summarizing the law and character- istics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the applica- tion of BMPs (best management practices). It is a fresh method- ology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff..
基金Under the auspices of Key Project of National Natural Science Foundation of China(No.41130534)
文摘The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.
文摘Like the hard surfaces of streets and sidewalks in an urban environment, the vertical and horizontal surface area on the outside of urban buildings contributes to the constant heating of large cities around the world. However, little is done to design this surface to benefit the public sphere. Instead, the facade of a building performs either as a component that focuses only on the quality of comfort for interior occupants, while ignoring effects on the exterior of the building, or as an identifiable aesthetic for the building＇s owners, This essay proposes the rethinking of the building facade as a steward of outdoor pedestrian welfare, and the conception of public health as an added function of the building envelope- a concept that may fall into the jurisdiction of public works. If the huge total surface area of a city＇s buildings is thought of as part of the city＇s infrastructure, then its public contribution may not only make outdoor areas comfortable, clean, and enjoyable, but also help to alleviate the bigger problem of rising temperatures in cities.
基金supported by the National Natural Science Foundation of China (Grant Nos.41305114 and 41175030)supported by Beijing Municipal Natural Science Foundation (Grant No.8121002)
文摘The North China Plain(NCP) has recently faced serious air quality problems as a result of enhanced gas pollutant emissions due to the process of urbanization and rapid economic growth.To explore regional air pollution in the NCP,measurements of surface ozone(O3),nitrogen oxides(NOx),and sulfur dioxide(SO2) were carried out from May to November 2013 at a rural site(Xianghe) between the twin megacities of Beijing and Tianjin.The highest hourly ozone average was close to 240 ppbv in May,followed by around 160 ppbv in June and July.High ozone episodes were more notable than in 2005 and were mainly associated with air parcels from the city cluster in the hinterland of the polluted NCP to the southwest of the site.For NOx,an important ozone precursor,the concentrations ranged from several ppbv to nearly 180 ppbv in the summer and over 400 ppbv in the fall.The occurrence of high NOx concentrations under calm conditions indicated that local emissions were dominant in Xianghe.The double-peak diurnal pattern found in NOxconcentrations and NO/NOx ratios was probably shaped by local emissions,photochemical removal,and dilution resulting from diurnal variations of surface wind speed and the boundary layer height.A pronounced SO2 daytime peak was noted and attributed to downward mixing from an SO2-rich layer above,while the SO2-polluted air mass transported from possible emission sources,which differed between the non-heating(September and October) and heating(November) periods,was thought to be responsible for night-time high concentrations.
文摘Land surface temperature (LST) of Beijing area was retrieved from Landsat TM thermal band data utilizing a radiative transfer equation and the urban heat island (HUI) effects of Beijing and its relationship with land cover and normalized difference vegetation index (NDVI) were discussed. The result of LST showed that the urban LST was evidently higher than the suburban one. The average urban LST was found to 4.5 ℃ and 9 ℃ higher than the suburban and outer suburban temperature, respectively, which demonstrated the prominent UHI effects in Beijing. Prominent negative correlation between LST and NDVI was found in the urban area, which suggested the low percent vegetation cover in the urban area was the main cause of the urban heat island.
文摘The traditional methods of storm sewers design must be supplemented by a precise and systematic analysis of the consequences of urbanization. This will ensure the reduction of the negative effects of urbanization in the process of stormwater sewer system normal functioning. As the urbanization of rural areas has been in constant progress, there was a need for the development of infrastructure system of urban planning documents that accompany urbanization. Surface storage appears to be one of the solutions that can have positive effects on the consequences of rapid urbanization in terms of preserving water quality of recipients, as well as opportunities to reduce the diameter of drain pipes downstream of surface storage. The necessary investments do not exceed the values of conventional technologies and procedures that are used for this purpose. The restriction of application of these methods is reflected in the limited space, especially in the smaller urban areas, where urbanization was a sudden and uncontrolled process. Future planning documents must contain alternatives like these, while the reservation of required space must be included in the planning documents in which the treatment of further development of the city will be found.
