Grave Soils Research Articles

Long-term effects of buried vertebrate carcasses on soil biogeochemistry in the Northern Great Plains.

Decomposing vertebrates impact ecosystems by stimulating animal, insect, and microbial scavengers, perturbing biogeochemical cycles, and transferring elements back to the environment. Most studies exploring the impacts of vertebrate decomposition focus on surface decay scenarios over timescales of days to years. Accordingly, our knowledge of ecosystem impacts of vertebrate decomposition in burial contexts and over longer time scales is limited. In 2000, six animal carcasses were buried in a shallow grave (<1.0 m) and allowed to decompose naturally until partial excavation in 2021, enabling evaluation of long-term soil biogeochemical responses to decomposing vertebrates. Soils were sampled along three vertical transects from the surface to the bone-bearing layer (~40 cm depth) and below. Comparison of the physical and chemical properties of the grave and control soils from equivalent depths indicate significant perturbations even 21 years after burial. Notably, soil pH was significantly more acidic in grave soils (p = 0.0296), and conductivity was significantly elevated (p = 0.0009). Grave soils were significantly enriched with respect to nitrogen stable isotopes, exhibiting δ15N values of 10.48 ± 3.6‰, which is ~5‰ greater than controls. Carbon and nitrogen content was also disrupted in the burial, with five times more nitrogen in the bone-bearing layer and almost double the carbon. Water and acid-based extractions of soils revealed significant differences between grave and control soils, driven largely by calcium, phosphorus (P), magnesium, and iron concentrations. P concentrations in acid extracts were significantly enriched at the bone-bearing layer, suggesting release of P from the bones. This study demonstrates that decomposition may result in long-lived impacts to burial environments and soil biogeochemistry, even after soft tissues decay. While not typically considered in ecosystem models, buried remains contribute to soils for decades or longer, and soil biogeochemistry serves a critical role in facilitating or preventing the long-term preservation of bone.

Identification and quantification of adipocere from human grave soils and its forensic application

Identification and quantification of adipocere from human grave soils and its forensic application

Structural stabilization of soil backfill with quicklime

AbstractThe application of quicklime (CaO) to soil backfill for the amelioration of poorly aerated grave soils (sandy loam) was tested in a cemetery in Germany. Two grave simulations (soil pits 9 m × 2 m × 1.6 m, l × w × d) were set up. Variation sans was only excavated and refilled, while in variation qlm, 20 kg quicklime per m3 soil were added to the backfill. Soil matric potential and gas composition were recorded over a period of 24 months in the two refilled pits and in the surrounding undisturbed soil (ref) at the 50 cm and 135 cm depths, respectively. Soil samples were taken in the beginning from ref and in three‐month intervals from the treatments sans and qlm. Soil pH and CaCO3 content, as well as bulk density (ρB), air capacity (AC), air conductivity (kl), and saturated hydraulic conductivity (ks) were measured. Excavation and backfill of the untreated soil (sans) led to an increase in ρB at the 50 and 90 cm depths and decreases in AC, kl, and ks when compared to ref. Quicklime application led to an increase in pH, the formation of CaCO3 in the formerly carbonate‐free soil, consistently reduced ρB, and increased AC, kl and ks. Although the quicklime application did not lead to notably more negative matric potentials, it increased the O2 concentration in the soil air and reduced the CO2 concentration to zero. The results show that the application of quicklime helps the structural amelioration of cemetery soils even at relatively low clay contents.

Signatures of degraded body tissues and environmental conditions in grave soils from a Roman and an Anglo-Scandinavian age burial from Hungate, York

Despite the importance of human burials in archaeological investigations of past peoples and their lives, the soil matrix that accommodates the remains is rarely considered, attention being focused mainly on visible features. The decomposition of a buried corpse and associated organic matter influences both the organic composition and, directly or indirectly, the microstructure of the burial matrix, producing signatures that could be preserved over archaeological timescales. If preserved, such signatures have potential to reveal aspects of the individual's lifestyle and cultural practices as well as providing insights into taphonomic processes. Using organic chemical analysis and soil micromorphology we have identified organic signatures and physical characteristics relating to the presence of the body, and its decomposition in grave soils associated with two human skeletons (one Roman age and one Anglo-Scandinavian age) from Hungate, York, UK. The organic signatures, including contributions from body tissues, gut contents, bone degradation and input from microbiota, exhibit spatial variations with respect to anatomical location and features of the immediate burial environment. In the Roman grave broad changes in redox conditions associated with the decomposition of the corpse and disturbance from the excavation and use of an Anglo-Scandinavian age cess pit that partially cuts the grave were evident. Leachate from the cess pit was shown to exacerbate the degradation of the skeletal remains in the regions closest to it, also degrading and depleting spherulites in the soil, through decalcification of the bone and liberation of bone-derived cholesterol into the soil matrix. The findings from this work have implications for future archaeo- and contemporary forensic investigations of buried human remains.

Improvement of oxygen transport functions in grave soils due to quicklime application depending on soil texture

Quickliming (application of CaO) was tested as structure amelioration method in order to improve aeration properties in grave soils and thereby prevent decomposition problems due to an insufficient oxygen supply in the burial environment. CaO is expected to promote a stronger aggregation and stabilization in the backfilled soil and thereby enhance pore functionality. In this study, grave simulations (without buried corpses) were set up at three differently textured sites in Germany (S1: sandy loam, S2: silt loam, S3: clay loam texture) with clay contents ranging from 6 to 35%. Each site included two grave simulations: (i) excavation and backfill only (“Nil” treatment) and (ii) addition of 20 kg CaO m−3 to the soil backfill (“CaO” treatment) prior to backfilling. Undisturbed soil cores were repeatedly taken at specific time intervals to determine the aeration status in the simulated cover layer (L1, above potential coffin position in 50 cm depth) and the coffin layer (L2, 90–135 cm depth) by measuring the diffusivity and pore functionality parameters (air-filled porosity (θa), pore continuity index (C1) and tortuosity (Τ)) at field capacity (−6 kPa). Field measurements included a continuous monitoring of field moisture conditions (matric potential) and repeated measurements (2–4 week intervals) of O2 concentrations in both layers (L1 and L2).The addition of CaO to the backfill improved the aeration properties in the grave simulations; this was indicated by a higher diffusivity and mostly higher O2 concentrations at all sites, which was related to a more continuous (C1) and less tortuous (Τ) pore system compared to the “Nil” treatment. However, under field conditions, the effectiveness of soil-lime-mixtures was reduced with increasing clay and soil moisture content. A permanently high water saturation in L2 at S2 and S3 offsets the positive effects of CaO on gas transport ability and therefore restricts an undisturbed gas exchange from the atmosphere to the coffin layer. Consequently, for grave soils with high stagnic/ground water level an additional drainage is needed, while for cohesive, clay-enriched soils a more pronounced homogenization and lime mixing intensity is recommended.

Changes in soil aeration and soil respiration of simulated grave soils after quicklime application

AbstractThe decomposition of buried human remains on cemeteries can be delayed in poorly aerated graves due to high water levels and a low permeable pore system for oxygen and water transport. With aim to improve the soil aeration properties in the burial environment, the addition of quicklime (CaO) to the grave backfill was tested. Quicklime is expected to promote a stronger aggregation and stabilization of the backfilled soil mainly by forcing an immediate dehydration and particle cementation processes.Two different grave simulations (without buried corpses) were prepared: (1) mixing the grave backfill with 20 kg m−3 quicklime (“CaO”) and (2) backfill without CaO (“NIL”) on a cemetery in Northern Germany. The soil type was a Terric Anthrosol (Stagnic) with a loamy sand texture. Undisturbed soil cores were taken from two depths before and after excavation and backfill at regular intervals of 3 months in order to analyze changes in (1) gaseous transport functions expressed by air‐filled porosity, air permeability (air permeameter), gas diffusivity (double chamber method) and related pore continuity indices as well as in (2) soil respiration (alkali trap method) representing microbial activity.Results clearly demonstrated a more conductive pore system in the CaO variant reflected by higher gas diffusivity and air permeability over 1 year compared to the NIL variant. Pore continuity indices also indicated a more connective pore system for the CaO variant. Effects of CaO application on soil respiration rate differed between the quarterly sampling times. Results indicated that microorganism were still active under alkaline soil conditions induced by CaO application, but the quantitative determination of biologically produced CO2 is influenced by chemical reactions when hydrated quicklime [Ca(OH)2] was reformed to limestone under consumption of CO2. The experiments indicate that the application of quicklime is a promising approach to improve aeration properties of grave soils and is therefore proposed as an adequate method to improve the aeration of burials on cemeteries.

The application of amplicon length heterogeneity PCR (LH-PCR) for monitoring the dynamics of soil microbial communities associated with cadaver decomposition

The placement of cadavers in shallow, clandestine graves may alter the microbial and geochemical composition of the underlying and adjacent soils. Using amplicon length heterogeneity-PCR (LH-PCR) the microbial community changes in these soils can be assessed. In this investigation, nine different grave sites were examined over a period of 16weeks. The results indicated that measurable changes occurred in the soil bacterial community during the decomposition process. In this study, amplicons corresponding to anaerobic bacteria, not indigenous to the soil, were shown to produce differences between grave sites and control soils. Among the bacteria linked to these amplicons are those that are most often part of the commensal flora of the intestines, mouth and skin. In addition, over the 16week sampling interval, the level of indicator organisms (i.e., nitrogen fixing bacteria) dropped as the body decomposed and after four weeks of environmental exposure they began to increase again; thus differences in the abundance of nitrogen fixing bacteria were also found to contribute to the variation between controls and grave soils. These results were verified using primers that specifically targeted the nifH gene coding for nitrogenase reductase. LH-PCR provides a fast, robust and reproducible method to measure microbial changes in soil and could be used to determine potential cadaveric contact in a given area. The results obtained with this method could ultimately provide leads to investigators in criminal or missing person scenarios and allow for further analysis using human specific DNA assays to establish the identity of the buried body.

Risk assessment on soil environment quality and losses of nitrogen and phosphorus for the gravel soils under different farming practices in the watershed of Lake Fuxian

On August 2006, grave soils from organic and conventional farming were sampled within the watershed of Fuxian Lake in Yunnan Province. Soil granule composition, heavy metal contents and nutrition accumulation in the soil profile were determined. Nitrogen and phosphorus losses from the soils were assessed by the in-door rainfall simulation. The results were as below: 1) both organic and conventional farming practices significantly lower the soil sand content on the 0-20 cm soil profile; 2) all soil heavy metal contents met the Class A standard of National Environment Quality Standard for Soils (GB/15618-1995) except Cd which only met Class B standard; 3) soil total nitrogen and organic matter accumulated in the 0-20 cm soil profile, and showed no significant differences between organic and conventional farming practices. The accumulation of soil total phosphorus, NO3-N and water dissolved phosphorus (WSP) under the organic farming practice is significantly higher than those under conventional farming practice; and 4) under the condition of 780 mm rainfall simulation, the risk of nitrogen and phosphorus losses from the organic farming soil is higher than that from the conventional farming. Total amount of nitrogen and phosphorus losses from the organic fanning soil were 1.9 and 19.8 times higher than those from the conventional farming soil, respectively.

The effect of soil type on adipocere formation

Adipocere refers to a postmortem product which forms from body fat in the later stages of decomposition. Factors present in the surrounding decomposition environment will influence adipocere formation and may accelerate or retard the process of conversion. One such factor important in burial environments is the type of grave soil in which the burial has taken place. This study was conducted to investigate the influence of various soil types on the formation of adipocere in grave soils. X-ray diffraction and particle size analysis were used to characterise the soils which were essentially chosen on the basis of grain size. Infrared spectroscopy, inductively coupled plasma-mass spectrometry, and gas chromatography–mass spectrometry were used to investigate the lipid profile and chemical composition of adipocere developed from decomposing tissue. The results suggest that adipocere is able to form in various soil types and that particular soil environments may accelerate its formation.

Characterization of Soils Containing Adipocere

The formation of adipocere (commonly known as grave wax), a spontaneous inhibition of postmortem changes, has been extensively analyzed in forensic science. However, soils in which adipocere formation occurs have never been described in detail. Therefore, this study is intended as a first step in the characterization of soils containing adipocere. Two grave soils (Gleyic Anthrosols) that prevent the timely reuse of graves due to the occurrence of adipocere and a control soil (Gleyic Luvisol) were selected from a cemetery in the Central Black Forest (Southwest Germany). Descriptions of soil morphology and a wide assay of physical, chemical, and microbiologic soil characteristics were accomplished. In contrast to the control soil, the grave soils were characterized by lower bulk density and pH. The degradation of the soil structure caused by digging led to a higher water table and the expansion of the reducing conditions in the graves where the prevalent absence of oxygen in range of the coffins inhibited decomposition processes. Although the formation of adipocere led to the conservation of the buried corpses, phosphorus, dissolved organic carbon, and cadavarine leaching from the graves was observed. Microbial biomass and microbial activity were higher in the control soil and hence reflected the inert character of adipocere. The study results clearly show the need for additional approaches in forensic, pedologic, and microbiologic research.

A gas chromatography‐mass spectrometry method for the detection of adipocere in grave soils

AbstractAdipocere refers to a decomposition product, which forms due to the post‐mortem conversion of adipose tissue into a lipid mixture. During the conversion process, triglycerides present in the adipose tissue convert to free fatty acids via hydrolysis. Under the right conditions, hydrogenation of the free fatty acids will yield adipocere, which is chiefly comprised of saturated fatty acids. In a burial environment, adipocere may form macroscopically on the decomposing remains, but may also leach into the surrounding soil. This paper describes the development of a gas chromatography‐mass spectrometry method which allows for the quantitative analysis of trace levels of adipocere in grave soils.

The identification of adipocere in grave soils

Soil samples recovered from grave exhumations have been analysed in an attempt to identify and characterise adipocere contained in the samples. The soil samples were collected from different environments, including samples recovered from forensic grave sites. Gas chromatography–mass spectrometry (GC–MS) was employed to identify adipocere and characterise the fatty acid composition. X-ray diffraction was used to characterise the soil environments.

Microbial characteristics of soils from graves: an investigation at the interface of soil microbiology and forensic science

Very little is known about the microbiology of graves. We have taken the opportunity to investigate this subject by taking advantage of the unusual opportunity afforded by the experimental burial of pigs in a forensic experiment. Selected microbial characteristics of soils from the 0–15 and 15–30 cm depths of the graves of three pigs and of control soils have been determined 430 days after burial. The grave soils contained more total C, microbial biomass C and total N, and showed increased rates of respiration and N mineralisation compared to the control soils. The grave soils also had larger amino acid and NH 4 + concentrations, which was consistent with the increases in both net N mineralisation and pH values. Nitrification was not detected in any of the soils and the limited NO 3 − supply restricted the rate of denitrification, but the large alkali-soluble S 2− concentration of soils from the graves indicated reducing conditions in the graves.