School of Pharmacy and Molecular Sciences, James Cook University, Douglas, QLD 4811, Australia.
Forensic Sci Int. 2010 Jul 15;200(1-3):60-6. doi: 10.1016/j.forsciint.2010.03.031. Epub 2010 Apr 18.
Forensic taphonomy involves the use of decomposition to estimate postmortem interval (PMI) or locate clandestine graves. Yet, cadaver decomposition remains poorly understood, particularly following burial in soil. Presently, we do not know how most edaphic and environmental parameters, including soil moisture, influence the breakdown of cadavers following burial and alter the processes that are used to estimate PMI and locate clandestine graves. To address this, we buried juvenile rat (Rattus rattus) cadavers (approximately 18 g wet weight) in three contrasting soils from tropical savanna ecosystems located in Pallarenda (sand), Wambiana (medium clay), or Yabulu (loamy sand), Queensland, Australia. These soils were sieved (2mm), weighed (500 g dry weight), calibrated to a matric potential of -0.01 megapascals (MPa), -0.05 MPa, or -0.3 MPa (wettest to driest) and incubated at 22 degrees C. Measurements of cadaver decomposition included cadaver mass loss, carbon dioxide-carbon (CO(2)-C) evolution, microbial biomass carbon (MBC), protease activity, phosphodiesterase activity, ninhydrin-reactive nitrogen (NRN) and soil pH. Cadaver burial resulted in a significant increase in CO(2)-C evolution, MBC, enzyme activities, NRN and soil pH. Cadaver decomposition in loamy sand and sandy soil was greater at lower matric potentials (wetter soil). However, optimal matric potential for cadaver decomposition in medium clay was exceeded, which resulted in a slower rate of cadaver decomposition in the wettest soil. Slower cadaver decomposition was also observed at high matric potential (-0.3 MPa). Furthermore, wet sandy soil was associated with greater cadaver decomposition than wet fine-textured soil. We conclude that gravesoil moisture content can modify the relationship between temperature and cadaver decomposition and that soil microorganisms can play a significant role in cadaver breakdown. We also conclude that soil NRN is a more reliable indicator of gravesoil than soil pH.
法医尸检学涉及利用尸体分解来估计死后时间间隔 (PMI) 或定位秘密坟墓。然而，尸体分解仍然知之甚少，尤其是在埋葬在土壤中之后。目前，我们不知道大多数土壤和环境参数，包括土壤湿度，如何影响埋葬后尸体的分解，并改变用于估计 PMI 和定位秘密坟墓的过程。为了解决这个问题，我们将幼年大鼠（Rattus rattus）尸体（约 18 克湿重）埋在来自澳大利亚昆士兰州帕拉伦达（沙质）、万巴亚纳（中壤土）或雅布卢（壤土沙质）热带稀树草原生态系统的三种不同土壤中。这些土壤经过筛选（2 毫米）、称重（500 克干重），调整至基质势为-0.01 兆帕（MPa）、-0.05 MPa 或-0.3 MPa（最湿到最干），并在 22°C 下培养。尸体分解的测量包括尸体质量损失、二氧化碳-碳（CO2-C）释放、微生物生物量碳（MBC）、蛋白酶活性、磷酸二酯酶活性、茚三酮反应性氮（NRN）和土壤 pH 值。尸体埋葬导致 CO2-C 释放、MBC、酶活性、NRN 和土壤 pH 值显著增加。在较低基质势（较湿的土壤）下，壤土沙质土和沙质土中的尸体分解更大。然而，在中壤土中，最优的尸体分解基质势被超过，导致最湿土壤中尸体分解速度较慢。在高基质势（-0.3 MPa）下也观察到尸体分解较慢。此外，湿沙质土壤与较大的尸体分解有关，而湿细质地土壤则相反。我们得出结论，墓穴土壤含水量可以改变温度与尸体分解之间的关系，土壤微生物可以在尸体分解中发挥重要作用。我们还得出结论，土壤 NRN 是墓穴土壤比土壤 pH 值更可靠的指标。
