Time variability of cumulative carbon dioxide concentration for adequacy assessment of greenspace: A case study in Surabaya, Indonesia

Introduction: The upward movement of Carbon dioxide (CO2) mass into the air and downwards towards the earth's surface, especially vegetative areas, affected the variability of CO2 concentration in the ambient air. In this pattern, this study aimed to determine the net cumulative value of CO2 concentration (Net_CO2-Con) in an urban area to assess the adequacy of greenspace. Materials and methods: This research method uses CO2 concentration observations within 24 h in 137 observation locations covering an area of 350 km2 in Surabaya city. The sampling location was set at a height of 2 m above the local ground. The CO2 concentration observations were carried out in the dry season and the rainy season for a total of 640 air samples. Results: The results of this study obtained Net_CO2-Con values for ambient CO2 concentrations in a daily pattern. Starting at night there was a flow CO2 flux into the air, which reached its peak in the morning, in about 90% of the city area. This event was evidence of a lack of CO2 absorption due to the lack of extensive vegetative areas. On a bright day the CO2 flux flows towards the land, which indicated the presence of vegetation absorption in addition to soil absorption. The seasonal time variability of CO2 flux density had the same pattern for the daily time variability. Conclusion: Mapping for CO2 flux could be an approach to determine the adequacy of greenspace. Areas of upward movement of CO2 flux density were priority areas for greenspace intensification.