Soil Organic Matter Composition in Urban Soils: A Study of Wroclaw Agglomeration, SW Poland

In urban areas, because of anthropopressure, the transformation of the soil cover can lead to the complete destruction of the natural layout and properties of these soils. The object of this study was to determine the quantity and quality of soil organic matter (SOM) originating in the topsoil horizons of the central part of Wroclaw (SW of Poland). Fractional composition of SOM and humic substances (HS) analysis were performed. Elemental composition and CP MAS C-13 NMR spectra for the humic acids (HA) were determined, and alpha (aromaticity) and omega (oxidation) ratios were calculated. Total organic carbon content ranged from 22.39 to 66.1 g kg(-1), while that of total nitrogen ranged from 2.09 to 4.6 g kg(1). In most analysed urban soils, the highest share in SOM was found for residual carbon (CR), while HA of low maturity was the predominant group over FA. CP MAS C-13 NMR spectroscopy of HA molecules indicated the structure of the samples was dominated by compounds with low aromaticity cores and considerable contents of aliphatic components. In urban soils, efforts should be made to enhance organic matter transformation into more matured and stable forms via, e.g., compost application and chemical treatments, and lawn maintenance should be very strictly controlled and limited.