No evidence for persistent natural plague reservoirs in historical and modern Europe.

Caused by Yersinia pestis, plague ravaged the world through three known pandemics: the First or the Justinianic (6th-8th century); the Second (beginning with the Black Death during c.1338-1353 and lasting until the 19th century); and the Third (which became global in 1894). It is debatable whether Y. pestis persisted in European wildlife reservoirs or was repeatedly introduced from outside Europe (as covered by European Union and the British Isles). Here, we analyze environmental data (soil characteristics and climate) from active Chinese plague reservoirs to assess whether such environmental conditions in Europe had ever supported "natural plague reservoirs". We have used new statistical methods which are validated through predicting the presence of modern plague reservoirs in the western United States. We find no support for persistent natural plague reservoirs in either historical or modern Europe. Two factors make Europe unfavorable for long-term plague reservoirs: 1) Soil texture and biochemistry and 2) low rodent diversity. By comparing rodent communities in Europe with those in China and the United States, we conclude that a lack of suitable host species might be the main reason for the absence of plague reservoirs in Europe today. These findings support the hypothesis that long-term plague reservoirs did not exist in Europe and therefore question the importance of wildlife rodent species as the primary plague hosts in Europe.

Rapid extraction of high- and low-density microplastics from soil using high-gradient magnetic separation.

Microplastics (MPs) are present in all environments, and concerns over their possible detrimental effects on flora and fauna have arisen. Density separation (DS) is commonly used to separate MPs from soils to allow MP quantification; however, it frequently fails to extract high-density MPs sufficiently, resulting in under-estimation of MP abundances. In this proof-of-concept study, a novel three-stage extraction method was developed, involving high-gradient magnetic separation and removal of magnetic soil (Stage 1), magnetic tagging of MPs using surface modified iron nanoparticles (Stage 2), and high-gradient magnetic recovery of surface-modified MPs (Stage 3). The method was optimised for four different soil types (loam, high­carbon loamy sand, sandy loam and high-clay sandy loam) spiked with different MP types (polyethylene, polyethylene terephthalate, and polytetrafluoroethylene) of different particle sizes (63 µm to 2 mm) as well as polyethylene fibres (2-4 mm). The optimised method achieved average recoveries of 96% for fibres and 92% for particles in loam, 91% for fibres and 87% for particles in high­carbon loamy sand, 96% for fibres and 89% for particles in sandy loam, and 97% for fibres and 94% for particles in high-clay sandy loam. These were significantly higher than recoveries achieved by DS, particularly for fibres and high-density MPs (p < 0.05). To demonstrate the practical application of the HGMS method, it was applied to a farm soil sample, and high-density MP particles were only recovered by HGMS. Furthermore, this study showed that HGMS can recover fibre-aggregate complexes. This improved extraction method will provide better estimates of MP quantities in future studies focused on monitoring the prevalence of MPs in soils.

First evidence of terrestrial ambrein formation in human adipocere.

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 of time, because adipocere is stable against degradation. The association of ambrein formation in ageing faecal material, under moist, oxygen-depleted conditions, now requires more attention in studies of other mammalian and geological samples. Indeed, ambrein and its transformation products may be useful novel chemical indicators of aged faecal matter and decomposed bodies.

Explosive detonation causes an increase in soil porosity leading to increased TNT transformation.

Explosives are a common soil contaminant at a range of sites, including explosives manufacturing plants and areas associated with landmine detonations. As many explosives are toxic and may cause adverse environmental effects, a large body of research has targeted the remediation of explosives residues in soil. Studies in this area have largely involved spiking 'pristine' soils using explosives solutions. Here we investigate the fate of explosives present in soils following an actual detonation process and compare this to the fate of explosives spiked into 'pristine' undetonated soils. We also assess the effects of the detonations on the physical properties of the soils. Our scanning electron microscopy analyses reveal that detonations result in newly-fractured planes within the soil aggregates, and novel micro Computed Tomography analyses of the soils reveal, for the first time, the effect of the detonations on the internal architecture of the soils. We demonstrate that detonations cause an increase in soil porosity, and this correlates to an increased rate of TNT transformation and loss within the detonated soils, compared to spiked pristine soils. We propose that this increased TNT transformation is due to an increased bioavailability of the TNT within the now more porous post-detonation soils, making the TNT more easily accessible by soil-borne bacteria for potential biodegradation. This new discovery potentially exposes novel remediation methods for explosive contaminated soils where actual detonation of the soil significantly promotes subsequent TNT degradation. This work also suggests previously unexplored ramifications associated with high energy soil disruption.

Investigation of sterols as potential biomarkers for the detection of pig (S. s. domesticus) decomposition fluid in soils.

This study was carried out to evaluate the potential of using cholesterol and coprostanol, as indicators for the detection of decomposition fluid of buried pigs (S. s. domesticus) in soils. In May 2007, four pig carcasses (∼35kg) were buried in shallow graves (∼40 cm depth) at the University of Ontario Institute of Technology in Canada. Two pigs were exhumed after three months (Pig 1, Pig 2) and six months (Pig 3, Pig 4) post burial. Soil samples were collected beneath the pig carcasses (∼40cm depth) and from grave walls (∼15-20 cm depth) as well as from a parallel control site. Coprostanol and cholesterol were extracted from soils, purified with solid phase extraction (SPE) and analysed with gas chromatography/mass spectrometry (GC/MS). A significant increase in cholesterol concentrations (p<0.05) and amounts of coprostanol were detected in soil located beneath the pig carcasses after three months of burial. It is assumed that during the putrefaction and liquefaction stages of decomposition pig fluid which contains cholesterol and coprostanol is released into the underlying soil. Therefore, cholesterol and coprostanol could be used as potential biomarkers to detect the presence of decomposition fluid three months after burial under comparable soil and environmental conditions. Further research is suggested for additional soil sampling before and after three months to investigate the abundance of these and other sterols.

Quantifying species composition in root mixtures using two methods: near-infrared reflectance spectroscopy and plant wax markers.

Understanding of plant interactions is greatly limited by our ability to identify and quantify roots belonging to different species. We proposed and compared two methods for estimating the root biomass proportion of each species in artificial mixtures: near-infrared reflectance spectroscopy (NIRS) and plant wax markers. Two sets of artificial root mixtures composed of two or three herbaceous species were prepared. The proportion of root material of each species in mixtures was estimated from NIRS spectral data (i) and the concentration patterns of n-alkanes (ii), n-alcohols (iii), and n-alkanes +n-alcohols combined (iv). For each data set, calibration equations were developed using multivariate statistical models. The botanical composition of root mixtures was predicted well for all the species considered. The accuracy varied slightly among methods: alkanes < alcohols = alkanes + alcohols < NIRS. Correlation coefficients between predicted and actual root proportions ranged from 0.89 to 0.99 for alkanes + alcohols predictions and from 0.97 to 0.99 for NIRS predictions. These two methods provide promising potential for understanding allocation patterns and competitive interactions.

The speed of soil carbon throughput in an upland grassland is increased by liming.

In situ (13)C pulse labelling was used to measure the temporal and spatial carbon flow through an upland grassland. The label was delivered as (13)C-CO(2) to vegetation in three replicate plots in each of two treatments: control and lime addition. Harvests occurred over a two month period and samples were taken along transects away from the label delivery area. The (13)C concentration of shoot, root, bulk soil, and soil-respired CO(2) was measured. There was no difference in the biomass and (13)C concentration of shoot and root material for the control and lime treatments meaning that the amount of (13)C-CO(2) assimilated by the vegetation and translocated below ground was the same in both treatments. The (13)C concentration of the bulk soil was lower in the lime treatment than in the control and, conversely, the (13)C concentration of the soil-respired CO(2) was higher in the lime. Unlike the difference in bulk soil (13)C concentration between treatments, the difference in the (13)C concentration of the soil-respired CO(2) was obvious only at the delivery site and primarily within 1 d after labelling. An observed increase in the abundance of mycorrhizal fungi in the lime treatment was a possible cause for this faster carbon throughput. The potential key role of mycorrhizas in the soil carbon cycle is discussed. The importance of a better understanding of soil processes, especially biological ones, in relation to the global carbon cycle and environmental change is highlighted.