Organic carbon stored in pavement joint material of paved urban soils

Cities emit large amounts of CO₂ while urban soils can be crucial sinks for organic carbon (C_org), spatially highly variable due to human activities. In cities, paved soils - streets, sidewalks, plazas - account for about 1/3 of the surface area but little is known about its C_org. It is for instance stored in the soil between the pavers. As the pavement joint material, also called Dialeimmasol, is highly exposed to anthropogenic influences, we assumed that its C_org is not only natural e.g. humus but of technogenic nature, among it black carbon (BC).

Soil mapping guidelines propose to use the Munsell Soil Color chart and pedotransfer functions to predict humus contents. Subsequently, C_org can be calculated using conversion factors. To assess whether this method, designed for natural soil, is applicable to the seam material of paved urban soils, predicted contents were compared to measured C_org and BC of seam material from cities worldwide. The results are used to adjust the model accordingly and to discuss the sink function of paved soils regarding organic carbon.

Acknowledgements: We used data from soil samples that were provided from numerous international colleagues and data from samples that were partly analysed by late Sonja Brodowski, Institute of Crop Science and Resource Conservation, Soil Science and Soil Ecology, University of Bonn