Temporal And Spatial Evolution Of CO₂ Concentration Near The Ground In Different Functional Areas Of Oasis City And Its Influencing Factors

The use of fossil fuels in cities and changes in land use/covers are profoundly affecting the urban ecosystem carbon cycle and the temporal and spatial variation of urban atmospheric CO₂.The city is an important source of CO₂emissions.Direct observation of atmospheric CO₂concentration is essential for studying the contribution of human activities to atmospheric greenhouse gases.Observing atmospheric CO₂concentration is helpful to understand the temporal and spatial variation of urban CO₂concentration and determine its impact mechanism.This study takes Urumqi as the research object,and studies the temporal and spatial variation characteristics of atmospheric CO₂in urban ecosystem based on static fixed point and dynamic mobile sampling method.At the same time,this study based on the Urumqi City Ambient Air Quality National Control Automatic Monitoring Station released real-time air pollutant data for correlation research.The research results reveal the influence mechanism of urbanization on CO₂emissions,which has important theoretical and practical significance for further enriching the content of urban carbon cycle research and development.The main conclusions of this study are as follows:(1)The average CO₂concentration in the urban area of Urumqi is 472.65?mol·mol^-1.The CO₂concentration in the study area fluctuated between 381.71 and778.05?mol·mol^-1.From the perspective of seasonal changes,the overall characteristics of autumn and winter,low in spring and summer.During the monitoring period,the daily variation of atmospheric CO₂concentration in Urumqi showed“three peaks and two valleys”,and the peak time appeared to coincide with the peak period of Urumqi commuting.In July,August,September,October,and November,the daily variation of Urumqi showed that the CO₂concentration during the day was lower than that at night.In terms of the daily variation,the average daily difference in July,August,and September was 53,57,and 88?mol·mol^-1,and the average daily difference in October and November was 104 and 100?mol·mol^-1.This phenomenon is mainly related to the change in the intensity of the carbon source.(2)The average value of near-surface CO₂concentration in different functional areas was 454.38?mol·mol^-1,and the daytime atmospheric CO₂concentration varied from 404 to 498?mol·mol^-1,showing significant spatial heterogeneity.According to the functional area,the average CO₂concentration during static monitoring is:industrial area>commercial traffic mixed area>residential area>cultural area>protected area.(3)Mobile observations show that the concentration of CO₂near the surface of Urumqi City is trending from north to south.The value of CO₂concentration in each district:New Urban Area>Midong District>Shuimogou District>Tianshan District>Shayibak District.The spatial distribution of CO₂concentration in the vicinity of Urumqi is similar to that of the built-up area.In the three typical samples of AL,HB and HN,the near-surface CO₂concentration decreases with the distance from the origin,and there is a clear“CO₂island phenomenon”,and the center deviates to the northwest.This also develops with the economic level of the economic regions.Related.(4)When the outer loop movement monitoring,the trend is in the southeast,the middle is high and the northwest is low.The highest value appears near the Karamay West Street Institute of Technology.The lowest value is near the exhibition center.Because the exhibition center is more open,it is suitable for CO₂.The diffusion of the concentration does not easily cause aggregation of the CO₂concentration.(5)Mainly discuss the influence of different factors on CO₂concentration.Different underlying surface characteristics,meteorological elements and road density have certain contribution and reduction to near-surface CO₂.The CO₂concentration near the ground in Urumqi was significantly positively correlated with the coverage of construction land,and the correlation coefficient was 0.73(P<0.01).There was a significant negative correlation with the green coverage rate,and the correlation coefficient was-0.43(P<0.01).The lower the residential land,the lower the CO₂concentration in the ground,and the proportional relationship between the two.Green space is an important source of CO₂elimination in urban areas.The higher the green area is,the lower the CO₂concentration in the near ground.There was a significant negative correlation between wind speed and near-surface CO₂concentration.The correlation coefficient was-0.72(P<0.01).The near-surface CO₂was significantly negatively correlated with humidity and pressure.The correlation coefficients were-0.40 and-0.35,respectively(P<0.05).There was a significant positive correlation between temperature and CO₂concentration.Urumqi in summer,the temperature increases by 1%,the CO₂concentration increases by 2.36?mol·mol^-1Using superposition analysis,it can be concluded that the road density of Urumqi is sand area>Toutunhe District>Tianshan District>Shuimogou District>Daban District>Midong District>Urumqi County.For every 1%increase in urban road density,the CO₂concentration increases by 11?mol·mol^-1.During the monitoring period,PM_2.5,PM10,SO₂and NO₂,the main pollutants in Urumqi,generally showed“inverted U”.The atmospheric CO₂concentration showed a very significant positive correlation with PM10(correlation coefficient R was 0.970,P<0.01),and showed a significant positive correlation with PM_2.5,SO₂and NO₂(correlation coefficient R was 0.907,0.897,0.925,0.897,respectively).P<0.05).O3showed a significant negative correlation(correlation coefficient R was 0.949,P<0.05).The change in O3 concentration is mainly controlled by photochemical reactions.