Due to rapid growth of population, urbanization and industrialization, in many cites of the developing world, there is severe contradiction between urban land supply and land demand which resulted in many urban land u...Due to rapid growth of population, urbanization and industrialization, in many cites of the developing world, there is severe contradiction between urban land supply and land demand which resulted in many urban land use conflicting situations and urban environment degrading. This paper is mainly focused on this problem, demonstrating the feasibility and efficiency of environmental study by integrating GIS and environmetal zoning method. Two neighbourhoods of the old city of Wenzhou were chosen as the study area. With the aid of GIS software PC Arc/info as dBate IV, an urhan environmental impact assessment study was carried out based on the data available such as land use map and detailed attribute data of each land planning unit. The main factors taken into consideration include: the type of activity causing environmental stress, the type and strength of environmental impact and the type of receptive area that could be affected.展开更多
The homogeneous risk characteristics within a sub-area and the heterogeneous from one sub-area to another are unclear using existing environmental risk zoning methods. This study presents a new zoning method by determ...The homogeneous risk characteristics within a sub-area and the heterogeneous from one sub-area to another are unclear using existing environmental risk zoning methods. This study presents a new zoning method by determining and categorizing the risk characteristics using the k-means clustering data mining technology. The study constructs indices and develops index quantification models for environmental risk zoning by analyzing the mechanism of environmental risk occurrence. We calculate the source risk index, air risk field index, water risk field index, and target vulnerability of the study area with Nanjing Chemical Industrial Park using a 100 m - 100 m mesh grid as the basic zoning unit, and then use k-means clustering to analyze the environmental risk in the area. We obtain the optimal clustering number with the largest average silhouette coefficient by calculating the average silhouette coefficients of clustering at different k-values. The clustering result with the optimal clustering number is then used for the environmental risk zoning, and the zoning result is mapped using the geographic information system. The study area is divided into five sub-areas. The common environmental risk characteristics within the same sub-area, as well as the differences between sub- areas, are presented. The zoning is helpful in risk management and is convenient for decision makers to distribute limited resources to different sub-areas in the design of risk reducing intervention.展开更多
17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau, and an experimental method was established which is suitable for pollen extraction from aeolia...17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau, and an experimental method was established which is suitable for pollen extraction from aeolian sediment. A comparative study of pollen dating was carried out using the accelerator mass spectrometry (AMS)14C dating of known age samples, and then an experiment with the pollen concentrates was performed. The results indicate that pollen that has been deposited simultaneously with sediment in a stable environment can provide reliable ages. This technique will provide a way of improving the chronological framework for the Loess Plateau since the late Pleistocene. TheI4c dating was combined with field investigations, and from the geological record within this zone, evidence was extracted of four major monsoon precipitation changes during the transition from the late Pleistocene to Holocene.展开更多
文摘Due to rapid growth of population, urbanization and industrialization, in many cites of the developing world, there is severe contradiction between urban land supply and land demand which resulted in many urban land use conflicting situations and urban environment degrading. This paper is mainly focused on this problem, demonstrating the feasibility and efficiency of environmental study by integrating GIS and environmetal zoning method. Two neighbourhoods of the old city of Wenzhou were chosen as the study area. With the aid of GIS software PC Arc/info as dBate IV, an urhan environmental impact assessment study was carried out based on the data available such as land use map and detailed attribute data of each land planning unit. The main factors taken into consideration include: the type of activity causing environmental stress, the type and strength of environmental impact and the type of receptive area that could be affected.
文摘The homogeneous risk characteristics within a sub-area and the heterogeneous from one sub-area to another are unclear using existing environmental risk zoning methods. This study presents a new zoning method by determining and categorizing the risk characteristics using the k-means clustering data mining technology. The study constructs indices and develops index quantification models for environmental risk zoning by analyzing the mechanism of environmental risk occurrence. We calculate the source risk index, air risk field index, water risk field index, and target vulnerability of the study area with Nanjing Chemical Industrial Park using a 100 m - 100 m mesh grid as the basic zoning unit, and then use k-means clustering to analyze the environmental risk in the area. We obtain the optimal clustering number with the largest average silhouette coefficient by calculating the average silhouette coefficients of clustering at different k-values. The clustering result with the optimal clustering number is then used for the environmental risk zoning, and the zoning result is mapped using the geographic information system. The study area is divided into five sub-areas. The common environmental risk characteristics within the same sub-area, as well as the differences between sub- areas, are presented. The zoning is helpful in risk management and is convenient for decision makers to distribute limited resources to different sub-areas in the design of risk reducing intervention.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 49894170, 49725308)Chinese Academy of Sciences (Nos. KZ-951-A1-402 & KZ-952-S1-419)State Committee of Science and Technology of China.
文摘17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau, and an experimental method was established which is suitable for pollen extraction from aeolian sediment. A comparative study of pollen dating was carried out using the accelerator mass spectrometry (AMS)14C dating of known age samples, and then an experiment with the pollen concentrates was performed. The results indicate that pollen that has been deposited simultaneously with sediment in a stable environment can provide reliable ages. This technique will provide a way of improving the chronological framework for the Loess Plateau since the late Pleistocene. TheI4c dating was combined with field investigations, and from the geological record within this zone, evidence was extracted of four major monsoon precipitation changes during the transition from the late Pleistocene to Holocene.
