Study On Soil Water δ～(18)O Change To Instruction Of Urban Heat Island

Through analyzing heat islands conditions of Beijing city in past 10 years and testing soil water isotopeδ¹⁸O values from different level (10cm, 50cm, 100cm) at heat and cold island area, the influences of the high density population activity and the high strength production activity on soil waterδ¹⁸O changes were revealed. Then urbanization activity and process were indirectly demonstrated by measuring soil waterδ¹⁸O concentrations. The main results were as follows:1. In past 10 years, heat island effect of Beijing was remarkable day by day in fall and winter, which expanded the suburb. The level distribution transforms from "the single center" to "the multi-centers". The Beijing fall winter urban heat island intensity strengthened in 1996～2006 four spots in the city, month average temperature difference to rise 1.0℃, the greatest amplitude official garden station reached 2.0℃。The number of days of heat island at fall and winter increased sharply at Beijing last 10 years with the average number of day all above 15 days. The warm rate of Beijing heat island intensity increases is 8 times the warm rate natural factor (suburb) increases, discropemcies ramakable with the urban development index correlation coefficient. This explained humanity activities kinetic can affect the city temperature.2. The different area soil temperature and water content resulted in soil waterδ¹⁸O changes. With depth increasing, the soil water contentδ¹⁸O variations rule from different depth is: 50cm＜100cm＜10cm。Soil waterδ¹⁸O seasonal variations rule is: 10cm heat island in July is the maximum, with slightly lower in August and lowest at 9-12 month. cold island in July is the maximum and drop by month. The 50cm place heat island area presents the season trend of escalation, in November for biggest. And the trend of escalation is slow. The changes were steady in 100cm place and the seasonal variation is not obvious.3. The major effect factors of affecting soil water isotope changes included: soil water content, soil temperature, air temperature, soil compactness. The most important factor is soil temperature, next for soil compactness and soil water content. And soil pH had less influence onδ¹⁸O.4. Through the measurements, the soil water content isotopeδ¹⁸O changes of the surface layer (10cm) were highly related with the human motivations index such as soil temperature, air temperature, soil water content, soil compactness. Therefore humanity activities can be revealed throughδ¹⁸O changes.δ¹⁸O is a specific index, the different research about macroscopical on urban heat island.