【作者】 高磊；

【导师】 施斌；

【作者基本信息】 南京大学 ， 地质工程， 2011， 博士

【摘要】 城市热岛效应及其带来的各种环境和生态问题越来越受到重视,迄今为止对于城市热岛效应的研究主要集中在其对大气环境的影响,而对城市热岛效应环境中浅层土体的影响研究还很少。论文围绕城市环境中浅层土体热岛和干岛效应的实际观测及其时空变化规律进行了比较系统的研究,并取得了如下研究成果：1.对南京地区气象站近50年来的大气温度和30年来40cm深度内的浅层土体温度资料进行了综合分析,获得了南京地区半个世纪以来的大气温度和30年来浅层土体温度的变化规律。南京地区大气温度变化大致可分为三个阶段：1961-1967年,大气温度下降阶段,年平均温度下降了1.05℃；1968-1985年,大气温度波动偏冷阶段；1985-2007年,大气温度波动上升阶段,年平均温度上升了2.33℃。近30年来,地表(Ocm)温度明显高于浅层土体温度和大气温度,其温度上升幅度达到2.8。C左右。土体温度场呈现上升趋势,20cm以上的浅层土体温度上升幅度达到2.0℃左右,40cm深度的土体温度上升幅度仍达到1.75℃左右。2.南京城区地面覆盖层的性质对城市大气热岛效应的影响十分明显。论文在2008年7月27日至7月28日对南京城区和郊区的草地、水泥地面及地面以上80cm的大气温度观测分析的基础上,获得了一些重要数据和结论：城郊日平均温度差：水泥地为3.1℃,大气为1.9℃,草地为1.2℃；水泥地面平均温度高出大气3.8℃,高出草地4.7℃,而草地比大气低0.9℃,说明城市中草地对减轻城市热岛效应效果明显。3.在南京城区和郊区300cm深度内的浅层土体中,分别设立了长期观测站和短期监测点,并对它们的温度场和湿度场进行了2009年6月至2010年6月一年的观测和短期普查。结果表明：(1)与大气中的城市热岛和干岛效应一样,城区浅层土体中同样存在显著的城市热岛和干岛效应现象。根据本文非PVC管系统测得的土体温度数据统计,在300 cm深度范围内,城区浅层土体年平均热岛强度为2.14℃,日平均热岛强度变化范围为0.37℃-3.83℃；月平均热岛强度变化范围为1.34℃-2.9℃,7月份最大,11月份最小；季平均热岛强度变化为：冬季(2.57℃)>夏季(2.34℃)>春季(1.63℃)>秋季(1.53℃)。(2)根据本文PVC管系统温度观测数据统计,在浅层土体150cm深度范围内,土体年平均热岛强度为1.27℃,日平均热岛强度变化范围为0.28℃-3.03℃；月平均热岛强度变化范围为0.74℃-2.00℃,7月份最大,10月份最小；季平均热岛强度变化范围为0.83℃-1.51℃,夏季最大,秋季最小。(3)根据城郊不同覆盖层下的土体温度观测数据统计,在300 cm深度范围内,各覆盖层下浅层土体年平均热岛强度：裸土为1.82℃,草地为2.20℃,混凝土为2.22℃。土体月平均热岛强度：裸土6月份最大为3.54℃,11月份最小为0.16℃；草地7月份最大为3.02℃,11月份最小为1.28℃；混凝土1月份最大为4.06℃,5月份最小为0.92℃。(4)根据非PVC管系统所有湿度观测数据统计,在100 cm深度范围内,土体年平均干岛强度为-7.2%,日平均干岛强度变化范围为-28.0--4.5%；月平均干岛强度变化-19.1%--2.0%,7月份最小,1月份最大；季平均干岛强度变化为：夏季(-13.8%)<春季(-6.3%)<秋季(-5.2%)<冬季(-3.7%)。(5)根据城郊不同覆盖层下的土体湿度观测数据统计,在100 cm深度范围内,各覆盖层下浅层土体年平均干岛强度：裸土为-6.03%,草地为-15.04%,混凝土为-7.00%。月平均干岛强度：裸土5月份最小为-14.81%,2月份最大为0.06%；草地7月份最小为-26.30%,5月份最大为-10.21%；混凝土7月份最小为-23.95%,5月份最大为-2.54%。(6)在2010年8月11日至2010年8月13日对城区和郊区近600个地点的土体温度和湿度进行了普查,结果表明：城区25cm深度处土体总体平均温度比郊区高3.30℃,各覆盖层下土体平均热岛强度：草地为3.34℃,裸土为3.24℃,树林为3.36℃。城区土体平均湿度比郊区总体低2.40%,各覆盖层下土体平均干岛效应：草地为-2.32%,裸土为-2.26%,树林为-2.05%。4.为了研究土体中的热传递规律、覆盖层传热特征、土体的渗透性、土的膨胀性等,课题组开展了一系列的室内物理模型试验,结果表明：(1)自制的土体温度物理模型试验系统具有较好的灵敏性和精度,可以用来模拟土体剖面温度随时间的变化规律。(2)不同覆盖层对土体剖面温度传递过程有一定影响。在混凝土板覆盖的情况下,由于表面热物理性质的改变,剖面土体平衡时温度较裸土高,土体的初始升温速率也高于裸土,但随着深度的增加,混凝土板覆盖层对初始升温速率的影响程度逐渐减弱。(3)饱和土的温度传递过程与风干土类似,但饱和土相对风干土,容积热容量大,因此它的平衡温度低于风干土。(4)水分入渗过程受到土体持水能力、入渗距离、水分补给量和补给时间等多因素的制约。土体膨胀过程中,随着水分补给量与补给时间的变化,土颗粒周围的结合水膜厚薄发生了变化,使得土颗粒之间的连接力减弱或者增强,导致土体膨胀或者收缩。5.为了提高浅层土体湿度测量的精确性,论文开展了大量试验工作,研究了基于FDR的土体湿度测量技术。结果表明：基于FDR的土体湿度传感器存在明显的温度效应,其测量值随温度的升高而线性增大,TDR-3型湿度传感器的温度修正系数范围为0.2%-0.3%(m3/m3)/℃,PR2型湿度传感器的温度修正系数范围为0.1%-0.2%(m3/m3)/℃。6.在大量观测资料和室内模型试验的基础上,对南京城区浅层土体中的热岛效应和干岛效应的形成机理进行了比较系统的分析。分析表明：南京城区浅层土体中存在明显的热岛效应和干岛效应现象,其原因来自于城市大气中的热岛效应。城市大气热岛效应通过各种地表覆盖层介质,向土中传递热量,导致土体温度场升高,同时导致土体中水分蒸发量上升,形成浅层土体的热岛和干岛效应。此外,浅层土体热岛和干岛效应还与地/气界面覆盖层的热物理性质、土体自身的物质组成、物理性质和状态结构、水分补给等因素有关。更多还原

【Abstract】 The urban heat island effect (UHIE) causes many environmental and ecological problems. Now, most of the researches on UHIE pay attention to its influences on the atmospheric environment, while few works on the shallow soil. In this paper, though the actual observation, the time and space variation of the soil heat and dry island effects were studied systematically. The research and corresponding findings are presented as follows:1. By analysing the temperature data of atmosphere from Weather station of Nanjing in the last 50 years and the temperature data of the shallow soil within 40cm depth in the last 30 years, the variation of temperature is obtained. The variation of atmospheric temperature in Nanjing can be divided into three stages:from 1961 to 1967 is the stage that atmospheric temperature declined, the mean annual temperature dropped by 1.05 ℃. From1968 to 1985 is the stage that atmospheric temperature fluctuated. From 1985 to 2007 is the stage that the atmospheric temperature fluctuations increased, the mean annual temperature increased by 2.33 ℃. In the last 30 years, the temperature of the surface (0cm) was higher than that of shallow soil and atmosphere, the temperature increased by about 2.8 ℃. Soil temperature is on the rise, the shallow soil above 20cm depth increased by 2.0 ℃ while 1.75 ℃ at depth of 40cm.2. The effect of urban ground cover on urban atmosphere island effect is very remarkable. Through the observation of air temperature that 80cm above the ground and the surface temperature of concrete and grass from July 27 to July 28,2008 in the urban and rural areas of Nanjing, some important data and conclusions are obtained. The mean daily temperature difference between the urban and suburban areas: Cement is 3.1 ℃, Atmosphere is 1.9 ℃, Grass is 1.2 ℃. The surface temperature of concrete is 3.8 ℃ over the temperature of air,4.7 ℃ higher than that of Grass. The surface temperature of grass ground is 0.9℃ lower than the air. It means that Grass has a remarkable effect on reducing the UHIE.3. Two long-term observation station and 600 short-term monitoring points were established respectively within the 300cm depth of shallow soil in Nanjing urban and rural areas respectively. From June 2009 to June 2010, there is a one year observation on the temperature and moisture field of soil. The results showed that:(1) As the same in the atmosphere, the urban heat island exists in the shallow soil of urban area. Based on the soil temperature data of Non PVC monitoring system, within 300cm depth, the mean annual soil heat island intensity (SHII) of urban soil is 2.14"C, the ranges of mean daily SHII are 0.37℃-3.83℃. The ranges of mean monthly SHII are 1.34℃-2.9℃, at maximum in July and minimum in November. The mean quarterly SHII are Winter (2.57℃), Summer (2.34℃), Spring (1.63℃), Autumn (1.53℃).(2) Based on the soil temperature data of PVC monitoring system, within 150cm depth, the mean annual SHII of urban soil is 1.27℃, the ranges of mean daily SHII are 0.28℃-3.03℃. The ranges of mean monthly SHII are 0.74℃-2.00℃, at maximum in July and minimum in Octomber. The ranges of mean quarterly SHII are 0.83℃-1.51℃, at maximum in Summer and minimum in Autumn.(3) Based on the soil temperature data of cover monitoring system, within 300cm, the mean annual SHII of urban soil:Bare soil is 1.82℃, Grass is 2.20℃, Concrete is 2.22℃. The mean monthly SHII, Bare soil are at maximum in June (3.54℃) and minimum in November (0.16℃). Grass are at maximum in July (3.02℃) and minimum in November (1.28℃). Concrete are at maximum in January (4.06℃) and minimum in May (0.92℃).(4) Based on the soil moisture data of Non PVC monitoring system, within 100cm depth, the mean annual soil dry island intensity (SDII) of urban soil is-7.2%, the ranges of mean daily SDII are -28.0--4.5%. The ranges of mean monthly SDII are-19.1%--2.0%, at minimum in July and maximum in January. The mean quarterly SDII are Winter (-3.7%), Summer (-13.8%), Spring (-6.3%), Autumn (-5.2%).(5) Based on the soil moisture data of cover monitoring system, within 100cm depth, the mean annual SDII of urban soil:Bare soil is-6.03%, Grass is-15.04%, Concrete is-7.00%. The mean monthly SDII, Bare soil are at maximum in February (0.06%) and minimum in May (-14.81%). Grass are at maximum in May (-10.21%) and minimum in July (-26.30%). Concrete are at minimum in July (-23.95%) and maximum in May (-2.54%).(6) Based on the soil moisture and temperature data of 600 monitoring points from August 11,2010 to August 13,2010 in urban and rural areas, at 25cm depth, the totally mean SHII of urban soil is 3.30℃:the mean SHII of urban soil, Bare soil is 3.24℃, Grass is 3.34℃, Wood is 3.36℃. The totally mean SDII of urban soil is-2.40%:the mean SDII of urban soil, Bare soil is -2.32%, Grass is -2.26%, Wood is-2.05%.4. In order to study the heat transfer in the soil, heat transfer characteristics of cover, soil permeability, soil swelling and so on. A series of indoor physical model test were made, the results show:(1) Homemade physical model of soil temperature test system has good sensitivity and precision. It can be used to simulate the variation of soil temperature with time.(2) Cover has some effects on the heat transfer process in soil. With the coverage of concrete, the equilibrium soil temperature is higher than that of bare soil because of the variation of the thermal properties. The initial heat increasing rate of the concrete soil is also higher than that of the bare soil. But with depth increasing, the influence of concrete on the initial heating rate gradually decreased.(3) The temperature transfer process of saturated soil is similar with that of air-dried soil. But compared with the air-dried soil, the specific heat of the saturated soil is higher, thermal conductivity and thermal diffusivity is smaller, so its equilibrium temperature is lower than dry soil.(4) The process of water infiltration is restricted by the water holding capacity of the soil, infiltration distance, water supply and time, and other factors. During the soil expansion process, the thickness of the soil bond water layer around changes with the water supply. It makes the strength of the connection between soil particles reduced or increased and leads to expansion or contraction of the air-dried soil.5. In order to improve the moisture measurement accuracy of the shallow soil, a large number of tests were made, and the techniques of soil moisture measurement based on FDR were studied. The results showed:An obvious temperature effect exists on the soil moisture sensor that based on FDR. The measured value increases linearly with the temperature. The ranges of temperature correction factor, TDR-3 are 0.2%-0.3%(m3/m3)/℃ and PR2 are 0.1%-0.2%(m3/m3)/℃.6. Based on a large number of observations outside and model test in the lab. The formation mechanism of the urban heat island effect and the dry island effect in the shallow soil in Nanjing is analyzed systematically. The urban atmosphere heat island effect transfers heat to the soil through different kinds of cover, which increases soil temperature. The evaporation of moisture in the soil increased at the same time. The two factors above cause the urban soil heat and dry island effect.In addition, the shallow soil and dry island heat island effect are also associated with the thermal properties of the cover in the land/air interface, material composition, physical properties and structure state of the soil, water supply and other factors.更多还原