Quality changes of soils in urban and suburban areas and its eco-environmental impacts--A review
城市土壤质量演变及其生态环境效应

Urbanization represents one of the most striking fo rms of the changes of natural eco-system to man-made eco-system,which may bri ng about a series of changes in ecological and environmental conditions and qual ities.Urbanization has a profound and far-reaching impact on the quantity and q uality of soil resources,which includes aspects such as the disappearance of soi l ecological functions by surface sealing;the worsening of soil physical propert ies;the strong influence of human activities on soil morphology and soil genesis ;the increase in short-range variability and decrease in overall soil diversity ,the aggravation of soil contamination and the soil nutrient enrichment.The arti ficially modified soils affect the ecological and environmental quality as well as the increase in pollutant load in runoff,the decrease in heat-buffering capa city and the contaminant transfer hazard.It is therefore urgent to study the qua lity change of soils in urban and suburban areas and its relationship with eco- environmental impacts,for the sustainable development of cities.This paper gives an overview on the following aspects. 1.Urbanization and ecological functions of urban soils Urbanization changes the ecological functions of urban soil dramatically,it incl udes:a)changes in land use type and fragmentation of landscape;b)changes in the hydrological processes;c)changes in the heating buffer capacity of land surface; and d)decease in diversity of both plants and soil microbes.; 2.Effects of urbanization on the quantity and quality of urban soils; Due to the construction of buildings,roads and recreation facilities,urbanizatin greatly reduce the area of open soil surface.In the mean time,urbanization also results in the deterioration of soil physio-chemical and morphological propert ies,pollution,soil forming processes,enrichment of nutrients such as nitrogen an d phosphorus and severe contamination of both metals and organics.; 3.Ecological impacts of soil degradation in urban areas; Degradation in urban soils results in a number of ecological impacts.Soil contam ination poses long-term risks on humans through soil-plant systems and soil-a tmosphere interactions.Enrichment in nutrients and changes in hydrological proce sses in urban areas can reduce both surface and groundwater quality.; 4.Perspectives in urban soil research Research on urban soils in China is still at the early stage,future effort shou ld be given to the basic understanding of the changes in soil properties under d ifferent patterns of urbanization,risk assessment of contamination in urban soil s and digital database(including soil classification)of urban soil resources for urban planning.