CO2 net ecosystem flux in Krakow, Poland

Urban areas, with dynamically changing, varied sources and sinks in highly heterogeneous terrain, are one of the most complicated ecosystems to explore. Being also a significant CO₂ net source, they contribute largely to uncertainty in local and global carbon balance calculations. Experimental data are required to verify existing CO₂ emission inventories and to become a reliable input to climate models.

Since 2021 an eddy covariance site has operated in Krakow, southern Poland. Site neighborhood includes various anthropogenic sources and sinks such as traffic, household heating, mainly with natural gas, and people themselves. On the other hand, a significant part of the source area is covered in green, with a municipal park and a number of home gardens.

We are presenting a data record from the beginning of the measurements in February 2021 up to the present. As expected, the area is a net CO₂ source, emitting on average around 7 kg of CO₂ per square meter yearly. Clear diurnal and seasonal patterns of CO₂ net flux were observed: morning and evening traffic peaks and negative values during the day due to active photosynthesis; also higher diurnal amplitude during the warm season but on average higher net CO₂ emission in winter. Directional flux analysis reveals that 1) the highest emissions come from the area where individual households as well as busy traffic lanes are located; and 2) urban green areas have a potential to become a net CO₂ sink during the day in all seasons except winter, however, mean diurnal emission on average remains positive.

This project has been partially supported by the European Union’s Horizon 2020 research and innovation program CoCO2 under grant agreement No. 958927, "Excellence Initiative - Research University" program at AGH University of Science and Technology, and the subsidy of the Ministry of Education and Science.