The Scale-Effects of Different Land Use Types on the Distribution Pattern of Park Green Space at Multiple Grid Scales-A Case Study on the Main Urban Area of Nanjing,China

Exploring the scale-effect of different land use types on the distribution pattern of urban park green space(PGS)at multiple grid scales would inform rational allocation and efficient collaborative construction of urban development land at different scales.Selecting 300-m,500-m,1,000-m,and 2,000-m grid scales,the research employed Create Fishnet tool in ArcGIS and Geodetector to construct a scale-effect analysis framework that revealed the scale-effects of different land use types on the distribution pattern of PGS at multiple grid scales in the main urban area of Nanjing,China in 2006,2012,and 2017.Main research results are:1)the overall distribution pattern of PGS showed the evolution characteristics from polarization to advancing quality and efficiency,while the trend gradually weakened with the increase of grid scale;2)the scale-effect of other land use types on PGS increasingly enhanced-the larger the grid scale,the more obvious the synergistic or compressive effect;3)the interactive scaleeffects of different land use types gradually enhanced-the larger the grid scale,the more significant the overall factor interaction;and 4)at the 300-m grid scale,the major interaction factors were residential,transportation,industrial/manufacturing,water area,and administration/public services,which gradually changed to residential,water area,and administration/public services up to the 2,000-m grid scale.The findings of this paper are expected to deepen the theory of the coupling between PGS and other land use types,as well as provide scientific support and a basis for efficient allocation,spatial layout optimization,and sustainable development of urban spaces.

Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park

Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments（RDSs） of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents＇ and tourists＇ health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size（〈150 μm） were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal（i.e., Cu, Zn, Pb and Cd） content was the largest in particles with small size（〈150 μm） among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively.Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index（I geo） decreased in the order：Cd〉Pb〉Cu〉Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order： Cd〉Zn≈Pb〉Cu.