Abstract: Carbon dioxide (CO2) is an important greenhouse gas whose global concentration has increased due to industrial and human activities, leading to climatic consequences such as rising temperatures contributing to the greenhouse effect. Large cities like São Paulo have been implementing monitoring networks to control CO2 concentration since the primary sources of emissions are energy, waste, and the enormous automotive sector. The present study collaborates with the METROCLIMA project and aims to understand vegetation’s role in regulating the CO2 concentration in the Metropolitan Region of São Paulo (MRSP). The methodology employed for this study involved on-site measurements and statistical analysis. Four stations from the METROCLIMA monitoring network, named Pico do Jaraguá, ICESP, IAG, and UNICID, were selected, each surrounded by a different fraction of vegetation cover, with CO2 measurements obtained from Picarro monitors from 2019 to 2022. Pico do Jaraguá is the station with the highest amount of nearby vegetation cover among all the stations, slightly outside the city of São Paulo. In contrast, ICESP and UNICID are the ones with strong urbanization nearby. IAG station is located in the University of São Paulo, which is characterized by a high amount of vegetation nearby and big important roads with heavy traffic jams. The data underwent filtering and treatment to correct for measurement errors. Histograms were obtained for data visualization to measure the seasonal concentration frequency. The results show that in all annual stations (spring, summer, fall, and winter), the CO2 concentrations mostly ranged between 400 to 500 ppm, with a frequency trend around 425 ppm. The concentrations did not exhibit a Gaussian behavior, emphasizing the complex gas dynamics in the MRSP. Temporal variations by hour and day were also considered, revealing a diurnal trend in all stations of decreasing CO2 concentration from 6:00 to 18:00 and increasing at night. ICESP, however, showed an increase in CO2 concentrations in the morning (6:00 – 12:00 hours) and a decrease in the afternoon, increasing again at night and reaching its peak the following day. This behavior may be related to the height of the measurement place (about 30 m from the ground), which directly impacts the detection of the boundary layer evolution throughout the day. Additionally, all analyses showed that IAG has a higher concentration and CO2 variation than the other stations. Statistical data shows that Pico do Jaraguá has a more stable CO2 concentration, averaging around 420 ppm, with a standard deviation of 9 for all annual stations, likely due to the nearby vegetation. In contrast, IAG has the highest standard deviation for all annual stations (spring: 20, summer: 18, fall: 22, and winter: 27), followed by UNICID (spring: 14, summer: 13, fall: 16, winter: 20). Therefore, the preliminary analysis showed that IAG is the measurement station with the most variability and the highest CO2 concentration at night, ICESP exhibits a different behavior compared to the trend of the other three stations, Pico do Jaraguá is the most stable measurement station with the lowest concentration, and in winter, all urban measurement stations experience an increase in concentration, with IAG standing out.

Keywords: Carbon Dioxide, Metropolitan Region of São Paulo, vegetation, Temporal Variation, Statistical Analysis