Review of human decomposition processes in soil

Journal of Chemistry

This study focuses on the assessment of the nutrients in the leachate and the groundwater quality around the Nkolfoulou landfill in Yaoundé known in French as “Centre de Traitement de Déchets (CTD).” Landfilling generates leachate that can pollute groundwater. Leachate along with groundwater samples (n=1+13) was collected in January (long dry season) and May (long wet season) 2014 and explored for various parameters including pH, temperature, EC, turbidity, TDS, TA, TSS, TH, BOD5, COD, Na+, K+, Mg2+, Ca2+, NH4+, NO3−, Cl−, F−, SO42−, PO43−, HCO3−, and colour using standard methods. In the leachate samples, values of TSS (700.2 and 130.2 mg/L), BOD5 (140 mg/L), COD (1350 and 1750 mg/L), NH4+ (82.50 and 39.51 mg/L), NO3− (159.32 and 74.82 mg/L), and Cl− (702.69 and 345.50 mg/L) exceeded the Cameroonian standards for effluent discharge. All the values of pH and some values of turbidity (4.55 and 4.50 NTU) and NH4+ (0.51 and 0.73 mg/L) in the groundwater samples violated the Cameroonian...

STAR: Science & Technology of Archaeological Research

Parchment is one of the most abundant resources in archives across the world and is a unique time-sensitive material through which centuries of livestock economies, trade and craft can be explored. We examine the impact of structural and chemical modifications during production to δ 13 C and δ 15 N values in the skin, particularly the removal of cutaneous keratins and lipids and the conversion of amide functional groups into carboxyl groups via alkaline hydrolysis. Through the manufacture of 51 parchment skins (sheep, goat, calf and pig) using both historic and modern manufacturing techniques, we found production resulted in a small enrichment in 13 C (average +0.12‰) and 15 N (+0.26‰). Our results pave the way for the isotopic analysis of parchment in paleodietary and paleoenvironmental studies for the historic period and establish the acceptable C:N ratios in deamidated collagenous tissues.

PeerJ

Background The use and partitioning of trophic resources is a central aspect of community function. On the ground of tropical forests, dozens of ant species may be found together and ecological mechanisms should act to allow such coexistence. One hypothesis states that niche specialization is higher in the tropics, compared to temperate regions. However, trophic niches of most species are virtually unknown. Several techniques might be combined to study trophic niche, such as field observations, fatty acid analysis (FAA) and stable isotope analysis (SIA). In this work, we combine these three techniques to unveil partitioning of trophic resources in a tropical and a temperate community. We describe patterns of resource use, compare them between communities, and test correlation and complementarity of methods to unveil both community patterns and species’ niches. Methods Resource use was assessed with seven kinds of bait representing natural resources available to ants. Neutral lipid f...

Diagnostics

Objectives: We provide a systematic review of the literature to evaluate the current research status of protein degradation-based postmortem interval (PMI) estimation. Special attention is paid to the applicability of the proposed approaches/methods in forensic routine practice. Method: A systematic review of the literature on protein degradation in tissues and organs of animals and humans was conducted. Therefore, we searched the scientific databases Pubmed and Ovid for publications until December 2019. Additional searches were performed in Google Scholar and the reference lists of eligible articles. Results: A total of 36 studies were included. This enabled us to consider the degradation pattern of over 130 proteins from 11 different tissues, studied with different methods including well-established and modern approaches. Although comparison between studies is complicated by the heterogeneity of study designs, tissue types, methods, proteins and outcome measurement, there is clear...

Jurnal Biosains Pascasarjana

Forensic taphonomy is a branch of forensic science which in its application uses processes related to the decomposition of corpses and uses soil evidence to estimate post-mortem interval (PMI) or post burial. Soil has evidential value because it contains minerals, plants and animal materials that are useful for characterization. This research was conducted by analyzing soil characteristics, namely soil pH and soil moisture and total nitrogen content in soil samples taken from under rabbit carcasses that were placed on the soil surface, buried 25 cm and 50 cm at each decomposition stage. The results obtained showed significant differences at each stage of decomposition and laying of the carcasses.

Geological Society, London, Special Publications

Police in the UK received information that a person had been reported as missing. Despite a diligent search and investigation, the person was not found. Several years later police received intelligence giving the location of a grave believed to contain the remains of the person previously reported as missing and now believed to be a victim of homicide. This new information suggested the missing person had been murdered and their remains were buried in a shallow, unmarked grave. Following a systematic search, the murder victim's body was found at a shallow depth, less than 1 m. Following the forensic recovery of the body, soil samples were collected at, beneath the floor of the grave, along the strike of the grave, downslope and upslope. Analysis of the soil samples showed elevated levels of putrescine, at nearly 150 ppb in the soils beneath, downslope and for several metres upslope from the body at localities where detector dogs had showed an ‘interest’ before the grave was disc...

PloS one, 2016

Keratinous 'soft tissue' structures (i.e. epidermally derived and originally non-biomineralized), include feathers, skin, claws, beaks, and hair. Despite their relatively common occurrence in the fossil record (second only to bone and teeth), few studies have addressed natural degradation processes that must occur in all organic material, including those keratinous structures that are incorporated into the rock record as fossils. Because feathers have high preservation potential and strong phylogenetic signal, in the current study we examine feathers subjected to different burial environments for a duration of ~10 years, using transmission electron microscopy (TEM) and in situ immunofluorescence (IF). We use morphology and persistence of specific immunoreactivity as indicators of preservation at the molecular and microstructural levels. We show that feather keratin is durable, demonstrates structural and microstructural integrity, and retains epitopes suitable for specific a...

Scientific Reports, 2021

Most biological features that occur on the body after death were already deciphered by traditional medicine. However, the molecular mechanisms triggered in the cellular microenvironment are not fully comprehended yet. Previous studies reported gene expression alterations in the post-mortem condition, but little is known about how the environment could influence RNA degradation and transcriptional regulation. In this work, we analysed the transcriptome of mouse brain after death under three concealment simulations (air exposed, buried, and submerged). Our analyses identified 2,103 genes differentially expressed in all tested groups 48 h after death. Moreover, we identified 111 commonly upregulated and 497 commonly downregulated genes in mice from the concealment simulations. The gene functions shared by the individuals from the tested environments were associated with RNA homeostasis, inflammation, developmental processes, cell communication, cell proliferation, and lipid metabolism....

International Journal of Legal Medicine, 2017

Several studies have been conducted on decomposition patterns and rates of surface remains, however, much less are known about this process for buried remains. Understanding the process of decomposition in buried remains is extremely important and aids in criminal investigations, especially when attempting to estimate the post mortem interval (PMI). The aim of this study was to compare the rates of decomposition between buried and surface remains. In order to compare these rates, twenty five pigs (Sus scrofa; 45-80 kg) were buried and excavated at different post mortem intervals (7 days, 14 days, 33 days, 92 days and 183 days). The observed total body scores were then compared to those of surface remains decomposing in the same region. Stages of decomposition were scored according to separate categories for different anatomical regions based on standardised methods. Variation in the degree of decomposition was considerable especially with the buried 7 day interval pigs that displayed variations in discolouration in the lower abdomen and trunk. At 14 and 33 days, buried pigs displayed features commonly associated with the early stages of decomposition, but with less variation. A state of advanced decomposition was reached where little change was observed in the next ±90-183 days after interment. Although the patterns of decomposition for buried and surface remains were very similar, the rates differed considerably. Based on the observations made in this study, a revised formula for the estimation of a PMI proposed pertaining to buried remains found at a depth of approximately 0.75m in the Central Highveld of South Africa.

Forensic Sciences, 2022

There are several methodologies available to estimate time since death based on different changes that a corpse undergoes after death. However, these methods are imprecise due to the decomposition process being affected by several factors, principally temperature and humidity. Current trends for the determination of the Postmortem Interval (PMI) attempt to estimate the PMI in a quantifiable manner, based on chemical changes on and in the body, summarized in the field of “thanatochemistry”. Although these methodologies have improved PMI estimates, additional research has been developed to increase the accuracy and precision of this determination. As a result, the fields of “thanatobiology” and “thanatomicrobiome” have emerged. Thanatobiology is based on the estimation of the PMI from DNA/RNA degradation, signaling pathways of cell death, and protein analysis. Thanatomicrobiome refers to changes in the bacterial communities as a consequence of the decomposition process. Although both ...

Scientific Reports, 2019

To date, the only known occurrence of ambrein, an important perfumery organic molecule, is in coproliths found in about one in a hundred sperm whales. Jetsam ambergris coproliths from the whale are also found occasionally on beaches worldwide. Here we report on the surprising occurrence of ambrein in human adipocere. Adipocere is a waxy substance formed post-mortem during incomplete anaerobic decomposition of soft tissues. Adipocere samples obtained from grave exhumations were analysed using gas chromatography-mass spectrometry (GC-MS). In addition to the typical fatty acids of adipocere, lesser amounts of ambrein were identified in the samples, in abundances similar to those of the major accompanying faecal steroids. The distribution of these compounds suggests that ambrein was produced post-mortem during the microbial decomposition of faecal residues and tissues. It is assumed that the adipocere matrix of saturated fatty acidsaided the preservation of ambrein over extended periods...

Journal of Forensic Sciences, 2018

The admissibility of human "odor mortis" discrimination in courts depends on the lack of comprehension of volatile organic compounds (VOCs) during the human decay process and of the lack in standardized procedures in training cadaver dogs. Blood was collected from four young people who died from traffic accidents and analyzed using HS-SPME/GC-MS at different decompositional stages. Two dogs, professionally trained, were tested to exactly locate blood samples, for each time point of the experiment. We found a long list of VOCs which varied from fresh to decomposed blood samples, showing differences in specific compounds. Dog performance showed a positive predictive value between 98.96% and 100% for DOG A, and between 99.47% and 100% for DOG B. Our findings demonstrated that decomposing human blood is a good source of VOCs and a good target for canine training.

Australian Journal of Forensic Sciences, 2019

The ability to monitor changes in human decomposition chemistry provides a potentially valuable tool for an understanding of the fate of human remains. This study reports the findings of an experimental study of a decomposing human cadaver investigated using infrared spectroscopy. This study was carried out at the Australian Facility for Taphonomic Experimental Research (AFTER) with a donated human cadaver clothed in cotton. An examination of the fluid retained by the cotton revealed that lipids and proteins, and their corresponding decomposition products, could be identified for the different stages of decomposition. The mechanisms for the changes to the lipid and protein components can be inferred from the spectroscopic changes observed and correlated with the corresponding decay processes observed for the cadaver. This study demonstrated that the use of this non-destructive technique allows the components of the decomposition fluid produced by decaying remains to be simultaneously monitored over time.

Archaeological and Anthropological Sciences, 2018

Stable isotope analysis from bone collagen and carbonate is a crucial tool in archaeometry for dietary and provenance studies. However, an expedient evaluation and interpretation of results have to rely on the integrity of the isotopic values, reflecting the in vivo signal of the tissue. In this context, postmortem bone breakdown can affect measurement results and add uncertainty. This study investigates the effects of bone breakdown and the use of two different extraction methods on the isotopic composition of carbon, nitrogen, and oxygen from collagen and the structural carbonate. The main goal of this study was to test the efficiency of commonly applied quality markers to identify alterations of the isotopic in vivo signal in the organic and inorganic bone fraction. Three fresh human femur diaphyses from different age groups with a known in vivo signal were degraded experimentally to simulate diagenetic processes. One batch was heated in water to induce hydrolytic breakdown; the other one was inoculated with several aerobic and anaerobic bacterial strains for biodeterioration. Furthermore, 60 long-bone samples from natural burial conditions, representing different age groups and burial times, were analyzed. The collagen extraction method proved to have a relevant effect. For bones already compromised by degradational processes, the common gelatin extraction protocol using pulverized bone and a 1 M HCl demineralization step was shown to be too harsh and damaging to the extract. Additionally, the age of the individual might play a role in the resistance of the tissue against degradational factors. The investigation of the commonly used quality criteria revealed that the C/N molar ratio is well suited to identify diagenetically modified isotopic data from collagen carbon and nitrogen. However, no valid marker could be assessed for the reliable prediction of altered δ 18 O values from the structural carbonate fraction, but oxygen isotopic values proved to be considerably affected by in vitro degradation.

International Journal of Legal Medicine, 2010

Adipocere is a late stage postmortem decomposition product that forms from the lipids present in soft tissue. Its formation in aquatic environments is typically related to the presence of a moist, warm, anaerobic environment, and the effect of decomposer microorganisms. The ideal temperature range for adipocere formation is considered to be 21-45⁰C and is correlated to the optimal conditions for bacterial growth and enzymatic release. However, adipocere formation has been reported in cooler aquatic environments at considerable depths. This study aimed to investigate the chemical process of adipocere formation in a cold freshwater environment in Lake Ontario, Canada. Porcine tissue was used as a human tissue analogue and submerged at two depths (i.e. 10 and 30 feet) in the trophogenic zone of the lake. Samples were collected at monthly postmortem submersion intervals and analysed using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy to provide a qualitative profile of the lipid degradation and adipocere formation process. Early stage adipocere formation occurred rapidly in the cold water environment and proceeded to intermediate stage adipocere formation by the second month of submersion. However, further adipocere formation was inhibited in the third month of the study when temperatures approached the freezing point. The depth of submergence did not influence the chemical conversion process as similar stages of adipocere formation occurred at both depths investigated. The study demonstrated that adipocere can form rapidly, even on small amounts of soft tissue, which may be representative of dismembered or disarticulated limbs discovered in an aquatic environment.

PLOS ONE, 2018

S4 Fig. Gene copy abundances of Total 16S rRNA (Bacteria), Bacteroides 16S rRNA (Bacteroides), and ITS (Fungi) within the grave. Bacteroides were below detection in all but the 70-75 cm samples.

Academic Forensic Pathology

Introduction: The oral cavity is home to numerous microorganisms including bacteria, fungi, and viruses which together form the oral microflora. It is the second most diverse microbial site in the human body after the gastrointestinal tract. Microbial degradation is a common phenomenon that occurs after death, with the early and advanced stages of decomposition being closely associated with oral microbial activity. Methods: This article reviews the current state of knowledge on the role of the oral microflora in postmortem events, and highlights the growing importance of terms such as forensic microbiology and thanatomicrobiome. This article also discusses next-generation sequencing, metagenomic sequencing studies, and RNA sequencing to study the oral thanatomicrobiome and epinecrotic communities in forensic oral genetics. Results: The indigenous microorganisms in the oral cavity are among the first to respond to the process of decomposition. DNA/RNA sequencing is a relatively simpl...

New Perspectives for Post-mortem Examination [Working Title]

After the death of individuals, sequential degradative processes called autolysis and putrefaction are initiated in the tissues, processes that cause total or partial degradation, sometimes leaving remnants of tissue. Mummification is a process by which the degradative processes are slowed and, in some cases, stopped, allowing the tissue to be apparently preserved. There are two main types of mummification: natural and artificial; natural mummification is caused by conditions related to the environment in which the tissues are located. Within the artificial techniques, there is cadaveric preservation (embalming), a procedure currently used for health and scientific studies. To carry out studies of tissues in some degree of decomposition or mummified, it is necessary to submit the samples for a process called recovery and/or rehydration, by means of immersion techniques in hypotonic solutions, which facilitates the processing and subsequent analysis of the characteristics of these ti...

Forensic Sciences

Cemeteries from the European Romantic period (18th–19th centuries) are often compared to small cities that hold memories, art, and history. Portuguese public cemeteries were first established in 1835 and became an interesting combination of fauna, flora, and monumental sculptures to mourn the dead at a location outside the limits of the city. Over the past 187 years, laws have been created and amended taking into consideration the needs of the population and the scientific knowledge available at each time point in history. Nevertheless, cemeteries have long been struggling with the lack of burial space which has been emphasised during the two years of the COVID pandemic. This work aims to review the development of Portuguese public cemeteries since their establishment, highlighting the imposed measures for the inhumation and exhumation of the deceased. It will also discuss the importance of soil as an abiotic agent, focusing on eight specific soil properties and their significance o...

Journal of Vertebrate Paleontology, 2017

PLOS ONE, 2015

In this study, a validated method using a thermal desorber combined with a gas chromatograph coupled to mass spectrometry was used to identify the volatile organic compounds released during decomposition of 6 human and 26 animal remains in a laboratory environment during a period of 6 months. 452 compounds were identified. Among them a human specific marker was sought using principle component analysis. We found a combination of 8 compounds (ethyl propionate, propyl propionate, propyl butyrate, ethyl pentanoate, pyridine, diethyl disulfide, methyl(methylthio)ethyl disulfide and 3-methylthio-1-propanol) that led to the distinction of human and pig remains from other animal remains. Furthermore, it was possible to separate the pig remains from human remains based on 5 esters (3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate). Further research in the field with full bodies has to corroborate these results and search for one or more human specific markers. These markers would allow a more efficiently training of cadaver dogs or portable detection devices could be developed.

Forensic Toxicology, 2019

Purpose Interpretation of drug levels in decomposed and buried corpses is difficult. We aimed to determine postmortem distribution of drugs in putrefied-decomposed visceral tissues and buried bones, and the effect of decomposition and burial on distribution of drugs in organs and bone tissues by administering drug groups selected from various drug classes to domestic pigs. Methods Pigs were divided into groups (n = 5) and dosed with a variety of drugs. Peripheral blood, organ and bone samples in different anatomical locations were collected from pigs killed. Organ samples were collected at postmortem 4th, 24th, 48th, 72nd and 96th hour. Then the corpses were buried below soil ground. Bone samples from buried corpses were collected at 5th and 10th months of the burial time by exhumation. All samples were analysed using liquid chromatography-tandem mass spectrometry after making sample preparation using appropriate methods. Results Only 10 of the 14 drugs were detected in the initial peripheral blood. For all bone types analyzed, highest drug levels were detected at thorax region and lowest drug levels were detected at the lower extremity. Given the fact that most of the soft tissue is located in the thorax region, it is possible that during the decomposition process, drugs partitioned from the liquefied tissue into bones. That the drug levels in bones decreased was observed when exhumation was done at 10th month of the burial time. Conclusions Drug distribution in organ and bone of decomposed and burial corpses vary due to unknown mechanisms and completely unexplained conditions such as postmortem redistribution.

Forensic Chemistry, 2023

The decomposition process involves the degradation of carbohydrates, nucleic acids, proteins and fats, and leads to the release of volatile organic compounds (VOCs) among many other decomposition by-products. Despite the extensive literature on the VOCs emitted in the air from vertebrate corpses, there is a lack of research dedicated to aquatic decomposition. In this study, we aimed to evaluate the potential of direct immersion solid-phase microextraction gas chromatography coupled with mass spectrometry (DI-SPME/GC/MS) to characterize dissolved cadaveric VOCs. Dimethyl disulphide and indole-two compounds commonly released during decomposition-were selected to evaluate and set the optimal methodological parameters, which were found to be 10 min of collection performed under 27.5 • C and a stirring rate of 250 rpm. Using responsive surface methodology, the obtained curves highlighted the appropriate conditions for the dissolved cadaveric volatilome analysis. The method allows to trap 17 dissolved cadaveric VOCs, including commonly encountered compounds such as dimethyl disulfide, 9-hexanoic acid, dimethyl trisulfide and indole. DI-SPME/GC/MS has therefore potential for the identification of dissolved cadaveric VOCs, pending further tests are performed to optimize the method and make it capable of detecting all dissolved VOCs, through all stages of decomposition.

Environmental Earth Sciences, 2019

Considerable research has been conducted on the physical and chemical corrosion of metals under various environmental conditions, but less attention has been given to the impact of corrosion on the environment. One such potentially hazardous situation may occur in cemeteries where metals and coatings used in the manufacturing of coffins may corrode, seep into the soils, and could end up in nearby water sources. The aim of this project was to determine whether burial materials corrode and leach into groundwater under controlled laboratory conditions. This was achieved by burying samples of burial materials in containers with three different soil types, namely sand, silt and clay. The experimental containers were exposed to various conditions simulating typical South African temperatures, rainfall intensities and with different pH values. A total of 24 simulations and 3 controls were tested. The leachates of each sample were collected every 8 weeks over a period of 6 months and tested for aluminium, iron, copper and zinc. In this experiment, it becomes evident that coffin materials do corrode and become mobile; however, they react differently in different soil media and under diverse environmental conditions. In general, the most corrosive conditions are high temperatures and acidic rainfall. Zn is the most corroded and mobile metal, with Fe being the least. It is notable that Al, Fe and Cu continue to leach out of the soils even after a period of 6 months. This may pose a health and environmental problem and a programme of groundwater quality monitoring should be undertaken in the vicinity of cemeteries.

Frontiers in Microbiology

The decomposition of a body is inseparably associated with the release of several types of odors. This phenomenon has been used in the training of sniffer dogs for decades. The odor profile associated with decomposition consists of a range of volatile organic compounds (VOCs), chemical composition of which varies over time, temperature, environmental conditions, and the type of microorganisms, and insects colonizing the carcass. Mercaptans are responsible for the bad smell associated with corpses; however, there are no unified recommendations for conducting forensic analysis based on the detectable odor of revealed corpses and previous research on VOCs shows differing results. The aim of this review is to systematize the current knowledge on the type of volatile organic compounds related to the decomposition process, depending on a few variables. This knowledge will improve the methods of VOCs detection and analysis to be used in modern forensic diagnostics and improve the methods o...

PLOS ONE, 2023

Mammalian decomposition provides pulses of organic matter to the local ecosystem creating ephemeral hotspots of nutrient cycling. While changes to soil biogeochemistry in these hotspots have been described for C and N, patterns associated with deposition and cycling of other elements have not received the same attention. The goal of our study was to evaluate temporal changes to a broad suite of dissolved elements in soils impacted by human decomposition on the soil surface including: 1) abundant mineral elements in the human body (K, Na, S, P, Ca, and Mg), 2) trace elements in the human body (Fe, Mn, Se, Zn, Cu, Co, and B), and 3) Al which is transient in the human body but common in soils. We performed a four-month human decomposition trial at the University of Tennessee Anthropology Research Facility and quantified elemental concentrations dissolved in the soil solution, targeting the mobile and bioavailable fraction. We identified three groups of elements based on their temporal patterns. Group 1 elements appeared to be cadaver-derived (Na, K, P, S) and their persistence in soil varied based upon soluble organic forms (P), the dynamics of the soil exchange complex (Na, K), and gradual releases attributable to microbial degradation (S). Group 2 elements (Ca, Mg, Mn, Se, B) included three elements that have greater concentrations in soil than would be expected based on cadaver inputs alone, suggesting that these elements partially originate from the soil exchange (Ca, Mg), or are solubilized as a result of soil acidification (Mn). Group 3 elements (Fe, Cu, Zn, Co, Al) increased late in the decomposition process, suggesting a gradual solubilization from soil minerals under acidic pH conditions. This work presents a detailed longitudinal characterization of changes in dissolved soil elements during human decomposition furthering our understanding of elemental deposition and cycling in these environments.