South Of Xian City Spring Air Co < Sub > 2 < / Sub > Concentration Change Research

Global warming has evidently damaged and interfered with the relationship created by human and ecological system, which will result to the profound changes for the climate system of the earth in the long term. City is a populated area where is regarded as the main emissions source area of greenhouse gas CO2. Only in terms of CO2concentration from the people living and consumption, the emission value is very considerable. Especially in the big and middle cities, the CO2emissions from transportation has a very high density, not to mention the carbon dioxide emitted from industrial production. But how to reduce CO2and achieve true "balance" of CO2concentration need more reasearches. Therefore, studying on the atmospheric CO2concentration and its influencing factors in the city or city areas has great impotant meanings to study the regularity of the CO2emissions and can provides clues for the CO2emissions controling, which has realistic meanings to build livable cities.The paper concerns the air CO2concentration of Nanjiao District of Xi’an in spring from March to May. According to the function regionalization, commercial district, culture tourist area for QuJiangTang, culture and education district and technology park are selected as the observation sites to observe the air CO2concentration above the ground2m. The air CO2concentration in the rainy day, after the rainy day and the sunny day, the air CO2concentration on work days and weekends, the air CO2concentration on the side pavement and motorway and the air CO2concentration on the bare area and vegetation area are observed to study the air CO2concentration regularity and its influence factors, and the conclusions are showed as follows:(1) The air CO2concentration level in spring of four function regionalization areas such as commercial district, culture tourist area for QuJiangTang, culture and education district and technology park of Nanjiao District of Xi’an can be divided as four stages from6am to6am the next day:high-low-high-low. In the commercial district and culture tourist area, the first stage is from6:40to8:40, and its average concentration is407ppm/h. The second stage is from9:40to13:40, and its average concentration is385ppm/h. The third stage is from14:40to0:40in the next day, and its average concentration is398ppm/h. The four stage is from1:40to5:40in the next day, and its average concentration is386ppm/h. In the culture and education district and technology park, the first stage is from6:40to11:40, and its average concentration is390ppm/h. The second stage is from12:40to18:40, and its average concentration is370ppm/h. The third stage is from19:40to0:40in the next day, and its average concentration is385ppm/h. The four stage is from1:40to5:40in the next day, and its average concentration is370ppm/h.(2) In the24fours, the average air CO2concentration is387ppm in Nanjiao District of Xi’an in spring. The concentration feature of diurnal variation is that the concentration in the daytime is lower than that at night and the concentration at night is1.02times more than that in the daytime.(3) The air CO2concentration in four functional areas in Nanjiao District of Xi’an in spring has significant difference, and the difference has statistic meanings. Their concentration relationship is commercial district> culture tourist area> technology park> culture and education district.(4) The air CO2concentration at daytime in Kaimi Square of Xiaozhai and the gate of Da Ci’en Temple at South Square of Big Wild Goose Pagoda are different from that in the IT park of Mong Block of the High Tech Zone and the bare area in the north of the G students apartment in the east gate of Changan campus of Shannxi normal university. The air CO2concentration in the former two areas reaches the maximum at14:40to15:40, and its concentration is420ppm. But the air CO2concentration in the latter two areas reaches the minimum at this period, and their air CO2concentration are respectively350ppm and370ppm. And the air CO2concentration in the former two areas reaches the minimum at9:40to12:40, and both their minimum concentrations are380ppm. But the air CO2concentration in the latter two areas reaches the maximum at7:40to8:40, and their respective maximum concentration are400ppm and410ppm.(5) The air CO2concentration at daytime in Kaimi Square of Xiaozhai and the gate of Da Ci’en Temple at South Square of Big Wild Goose Pagoda on workdays is7to9ppm less than that on weekends, and the CO2concentration at workdays is lower than that on weekends. The air CO2concentration at daytime in the IT park of Mong Block of the High Tech Zone and the bare area in the north of the G Students apartment in the east gate of Changan campus of Shannxi normal university on workdays is8to9ppm more than that on weekends, and the CO2concentration at workdays is higher than that on weekends.(6) The air CO2concentration above the ground2m and the population concentration as well as the car numbers have positive correlation, and their influrence on the city is carbon source.(7) The precipitation bloks the path that the soil releases CO2. At the same time, the photosynthesis of vegetation becomes weeker, and humans accordingly reduce outdoor activities, which will influrence the distribution of CO2and result to the different air CO2concentration in the rainy day, after the rainy day and the sunny day. Their air CO2concentration at daytiime are respectively256ppm,363ppm,372ppm, and the concentration in the sunny day> the concentration after the rainy day> the concentration in the rainy day.(8) When the relative humidity is bigger, the air CO2concentration is bigger too. The main reason is that when the relative humidity is bigger, the air pressure is accordingly higher, and the high building can blok the air convection, so CO2in the air can not easily decentralize.