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 km²in Surabaya city. The sampling location was set at a height of 2 m above the local ground. The CO₂concentration 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 of 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.