Temporal variation of near-surface CO₂ concentrations over different land uses in Suzhou City

The differences in near-surface CO₂ concentration variations over five urban land uses within Suzhou City are investigated from January to December 2014. The selected monitoring sites include a traffic road, a residential district with ~20-story apartments, an institutional office site, an amusement park, and a cultural site at the Yuanquan Temple. The diurnal variations of CO₂ show considerable fluctuation and different variable patterns at the monitoring sites controlled by the CO₂ emissions and weather condition variability. On rainy days, the variation of diurnal CO₂ is clearly smaller than that on sunny and cloudy days, with a reduction from 75 % at the amusement site to 41 % at the office-building site. Monthly variations indicate that the traffic and cultural sites experience the highest level of CO₂ in warm months, but the other sites are exactly opposite. In each month, the mean level of CO₂ at the cultural site is the lowest, but the traffic and amusement sites have the highest levels in warm months and cold months, respectively. Seasonal variations reveal that the traffic, residential, and office-building sites experience a smaller seasonal mean CO₂ fluctuation, and in the spring, autumn, and winter, the amusement site has the highest mean levels compared to the other sites. The urban CO₂ concentration is related to land use, local CO₂ emissions, temperature, and wind; therefore, it is necessary to establish as many monitoring stations as possible to reveal the urban features of CO₂ concentration variation.