a b s t r a c tThe components and concentrations of metals in street dust are indictors of environmental pollution. To explore the pollution levels of Cd, Cr, Cu, Mn, Ni and Pb in street dust and their spatial distribution characteristics, 220 dust samples were collected in a grid pattern from urban street surfaces in Beijing. Multivariate statistics and spatial analyses were adopted to investigate the associations between metals and to identify their pollution patterns. In comparison with the soil background values, elevated metal concentrations were found, except those for Mn and Ni. The results of the geo-accumulation index (I geo ) and the potential ecological risk index (Er i ) of the metals revealed the following orders: Cd > Cu > Cr > Pb > -Ni > Mn and Cd > Cu > Pb > Cr > Ni. Levels of I geo ranging from 0 to 5 were found and about 80% of the samples were below the moderately polluted level. The Er i values of single elements were within the low ecological risk level in most sampling sites. Most of the metals in the street dust of Beijing were statistically significantly correlated. It is hard to clearly identify the sources of each metal in the street dust since local environments are very complex. Cadmium, Cu, Cr, Mn and Pb showed medium spatial autocorrelations within the sampling region. Similar spatial distribution patterns were observed for Cu, Cr and Pb, and these metals had relatively high spatial variabilities and were enriched in the center of the city with several peaks scattered in the suburbs. Metal pollution anomalies were identified by using cluster and outlier analyses. Locations identified as clusters with high values indicated non-point source pollution, while locations identified as outliers with high values indicated point source pollution. Traffic, construction, and other human activities influenced these high values. In addition, the locations identified as outliers with low values in urban areas might benefit from less transportation and better management.
Introduction: Urban soils are large pools of carbon, nitrogen, and other elements, supporting plant growth, sustaining biogeochemical cycles, and serving as the foundation for maintaining ecosystem function and services of urban green spaces (UGS). Quantifying urban soil properties is essential for assessing urban ecosystem services and detecting pollution. Characterizing spatial heterogeneity of urban soil properties, which may change with land use or urbanization, is crucial for understanding urban ecosystem functions.
Green spaces in residential areas provide multiple cultural ecosystem services (CES), which can contribute to human health by increasing the frequency of residents' visits. We evaluated the CES of residential green spaces by assessing residents' satisfaction with these spaces in the city of Zhengzhou, China. The data reveal the supply capacity of CES in residential green spaces: the results suggest that the level of recreational services is low, whereas the residents' satisfaction with the sense of place and neighborhood relations is high. The lower the frequency of residents who visit a park outside the residential area, the higher the satisfaction with the CES. This suggests that residential green spaces can effectively compensate for the lack of nearby parks owing to their proximity to residents' living quarters. The CES in residential communities increased as vegetation coverage increased, indicating that natural vegetation is a source of CES. In addition, the results showed that residents' perceptions of plant decoration, landscape patterns, and management and infrastructure in particular can effectively improve the level of CES, and this could compensate for CES that have shrunk owing to low green space coverage. This study has practical significance and value for the planning and design of residential green spaces, offering suggestions for urban landscape planners and decision makers. Future research should combine the residents' perception of demand and supply of CES and should clarify the gap and trade-off between them.
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