Soil organic matter screening via thermal analysis coupled with mass spectrometry in park soils, Košice, Slovakia

Screening of soil organic matter (SOM) is necessary because it is a key indicator of soil health. For this reason, thermal analysis (TG/DTG, DTA) was used as a more effective alternative to conventional soil analysis. Due to these methods, we can rapidly, non-destructively, and accurately determine key parameters of global warming, mainly soil organic matter (SOM) and its key component, soil organic carbon (SOC). Soil organic matter was monitored in five park urban soil samples collected from the A horizon at a depth of 30 cm in one part of Košice, specifically in the concrete Košice city district called “Above the Lake”. The soil type established according to the Reference Base for Soil Resources was ANTHROSOLS in all studied soils. The studied soils were predominantly moderately alkaline, which was likely caused by higher carbonate contents, as confirmed in some cases via thermal analysis. DTG curves of the studied samples show several peaks, indicating that the SOM has different thermal sensitivities, which depend on the SOM’s chemical composition, including the presence of aliphatic and aromatic parts. Thermal analysis, coupled with mass spectrometry, provided comparable results to other techniques, such as loss on ignition (LOI), in determining the quantity of soil organic matter. SOM determined via LOI strongly correlated with the amount of SOM established by TG/DTG methods as the sum of thermogravimetry weight losses in two temperature intervals (188–400 °C) and (400–620 °C) (R2 = 0.88). It is known that this temperature interval corresponds to labile and stable SOM. The presented study shows that a combination of thermal analysis coupled with mass spectrometry, assuming that about 50% of all SOM exists as carbon, seems to be suitable for a quick assessment of SOM and SOC quantity, as well as carbonate content, with a single analysis.