MONITORING AND COMPARING OF SOIL PROFILE WATER CONTENTS IN URBAN AND SUBURBAN AREAS

The rapid development of urbanization significantly influences the urban geologic environment and especially the underground water environment.In this investigation,two long-term soil water monitoring stations were built in urban and suburban areas of Nanjing city.By using PR2,the soil profile water contents in one meter depth were monitored every day from June to September in 2009.It is found that the soil water content was significantly controlled by weather condition.Its sensitivity to weather decreased as the depth increased.A comparison of the data obtained from the two stations shows that the effect of weather to water content in the urban soil is not as significant as that in the suburban soil.The water content in the urban soil is generally lower than that in the suburban soil.An obvious urban dry island(UDI)effect is observed.During the period of June to September,the average UDI intensity is -9.1%,the highest day UDI intensity is about -20.7%,the highest month UDI intensity observed in July is about -17.0%,,and the minimal month UDI intensity observed in September is about-8.5%..In addition,it is shown that the temporal and spatial variations of soil water contents depend on the underlying surface properties.For example,the average soil profile water content under cement cover is less than those under grass and bare soil covers.It indicates that cement cover in urban area can obviously intensify the UDI effect.During the monitoring period(from June to September),it is found that,in urban area,the average profile water contents under bare soil cover,cement cover and grass cover are 26.9%, 25.6%,and 17.5%,respectively; whereas in suburban area,the three average profile water contents are 37.6%, 37.6%,(36.0%,respectively; the water content differences between the urban and suburban soils for grass,cement and bare soil covers are the highest,the intermediate and the lowest,respectively.