Dissolved organic matter: Unraveling the role of organic carbon from the hypogeal cadaver decomposition island

The biogeochemical processes occurring in soils beneath buried cadavers, here defined as hypogeal cadaver decomposition islands (HCDIs), remain poorly understood, particularly with respect to the role of organic carbon. This study investigated temporal variations in dissolved organic matter (DOM) within HCDI to evaluate its potential as a time-dependent decomposition marker. Twenty piglets were buried under controlled conditions at the non-human Forensic Taphonomy Facility Ticino-LEAF(s) (University of Milan, Italy), using four different concealment scenarios: unclothed, wounded, clothed in cotton, and covered with quicklime prior burial. Soil samples collected at successive post-burial intervals (PBIs) up to 467 days were analyzed for pH, DOM concentration, and molecular composition through Fourier Transform Infrared (FT-IR) spectroscopy. Results revealed consistent correlations between decomposition stage, soil pH, and DOM dynamics. In most groups, pH increased during early decay and declined in advanced stages, while DOM concentrations peaked at intermediate intervals before returning to baseline levels. FT-IR spectra highlighted molecular markers of lipids, fatty acids, and protein degradation, with adipocere-associated signals detectable at later stages. Quicklime-treated burials exhibited atypical chemical patterns, though DOM analyses remained informative. Other burial conditions, such as the presence of lesions or clothing, significantly influenced both decomposition processes and the expression of biochemical markers. This pilot study suggests that combined monitoring of DOM concentration and molecular characterization, supported by pH measurements, may contribute to a better understanding of decomposition processes. The approach shows potential for estimating the post-burial interval, suggesting a potentially rapid, cost-effective, and context-sensitive support tool for forensic investigations.