Nitrous oxide, methane and carbon dioxide dynamics from experimental pig graves

Area of Science:

• Forensic science
• Environmental science
• Biogeochemistry

Background:

• Decomposition of buried remains releases gases.
• Understanding these gases can aid in locating clandestine graves.
• Factors like depth and cadaver condition may influence gas release.

Purpose of the Study:

• To investigate the biogeochemistry of grave detection using nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2).
• To determine the effect of grave depth (shallow vs. deep) and cadaver condition (bagged vs. bare) on gas concentrations and emissions.
• To assess the utility of these gases for identifying buried remains.

Main Methods:

• Experimental burial of pig carcasses in shallow (30 cm) and deep (90 cm) graves.
• Comparison of bagged versus unbagged carcasses.
• Measurement of soil pore air concentrations and surface fluxes of N2O, CH4, and CO2 over three years.
• Inclusion of reference pits without remains and surface-exposed carcasses.

Main Results:

• Graves exhibited significantly higher N2O and CO2 concentrations and fluxes than reference pits.
• CH4 concentrations did not differ significantly between graves and reference pits.
• N2O and CO2 increased with depth, while CH4 decreased.
• Shallow graves and bare carcasses produced significantly higher N2O and CO2 emissions and pore air concentrations compared to deep graves and bagged carcasses, respectively.

Conclusions:

• N2O and CO2 are valuable indicators for grave detection, with higher concentrations in shallow, unbagged graves.
• Grave depth and cadaver condition significantly influence the release of decomposition gases.
• These findings contribute to the understanding of postmortem biogeochemistry for forensic applications.