Clare Wilson

An evaluation of multielement analysis of historic soil contamination to differentiate space use and former function in and around abandoned farms

Historic and prehistoric human activity can cause accumulation of elements in the soil. Multielement soil analysis has been used extensively over the last two decades to study element patterns of historic soil enrichment as a means of prospecting for sites and as an aid to interpretation of space use within archaeological structures. However, there have been surprisingly few of studies designed to assist with the interpretation of the analytical results. In this investigation soils from six abandoned farms with a known history of spatial use were sampled to determine if similar patterns of trace element enhancement occur between different farms. The preliminary results show significant differences in soil elemental concentrations between the functional areas, and highlight similar patterns of element enhancement between the farms. Concentrations of Ca, P, Sr, Ba, Zn and Pb are elevated in the buildings and fields of all the farms and provide valuable information about past human activity.

Three-Dimensional Mapping of Soil Chemical Characteristics at Micrometric Scale by Combining 2D SEM-EDX Data and 3D X-Ray CT Images

There is currently a significant need to improve our understanding of the factors that control a number of critical soil processes by integrating physical, chemical and biological measurements on soils at microscopic scales to help produce 3D maps of the related properties. Because of technological limitations, most chemical and biological measurements can be carried out only on exposed soil surfaces or 2-dimensional cuts through soil samples. Methods need to be developed to produce 3D maps of soil properties based on spatial sequences of 2D maps. In this general context, the objective of the research described here was to develop a method to generate 3D maps of soil chemical properties at the microscale by combining 2D SEM-EDX data with 3D X-ray computed tomography images. A statistical approach using the regression tree method and ordinary kriging applied to the residuals was developed and applied to predict the 3D spatial distribution of carbon, silicon, iron, and oxygen at the microscale. The spatial correlation between the X-ray grayscale intensities and the chemical maps made it possible to use a regression-tree model as an initial step to predict the 3D chemical composition. For chemical elements, e.g., iron, that are sparsely distributed in a soil sample, the regression-tree model provides a good prediction, explaining as much as 90% of the variability in some of the data. However, for chemical elements that are more homogenously distributed, such as carbon, silicon, or oxygen, the additional kriging of the regression tree residuals improved significantly the prediction with an increase in the R2 value from 0.221 to 0.324 for carbon, 0.312 to 0.423 for silicon, and 0.218 to 0.374 for oxygen, respectively. The present research develops for the first time an integrated experimental and theoretical framework, which combines geostatistical methods with imaging techniques to unveil the 3-D chemical structure of soil at very fine scales. The methodology presented in this study can be easily adapted and applied to other types of data such as bacterial or fungal population densities for the 3D characterization of microbial distribution.

A mobile knowledge management and decision support tool for soil analysis

This paper describes the implementation and evaluation of a mobile knowledge management and decision support system to assist archaeologists in dealing with soils. Our view is that provision of a mobile tool which provides access to expert knowledge and a means of recording pertinent onsite information will be of great benefit in ensuring crucial information about an excavation is not lost and that the excavation proceeds in an appropriate manner. In this paper we discuss the tool developed, and detail how it has been evaluated via a variety of workshop sessions with likely users, and discussions with advisory groups.

Stabilization of Organic Carbon via Chemical Interactions with Fe and Al Oxides in Gley Soils

Abstract The importance of soil organic carbon (SOC) stabilization via chemical interactions with Fe and Al oxide minerals within gley soils remains unclear. Changes in the proportions of Fe/Al oxides and SOC and N contents associated with Fe/Al oxides within the profiles of gley soils under contrasting hydrological regimes and freely draining control soils from Harwood Forest (northeast England) were investigated. Sequential selective dissolution techniques were used to measure Fe/Al oxide crystallinity and explore whether crystallinity differed between gleyed and freely draining soils. Extracts were analyzed using Fourier transform infrared spectroscopy to investigate the chemical characteristics of organic matter (OM) associated with Fe/Al oxides. Strongly crystalline Fe oxides were the dominant (∼50%–80% of total Fe oxides present) mineral phase in gley mineral soils. Contrasting gley soil hydrological regimes influenced total subsoil Fe and total and weakly crystalline Al oxide concentrations. Also, within-profile changes in strongly crystalline Fe oxide concentrations were linked to differences in hydrological and redox conditions. A large proportion of SOC (generally 70%–90% of total) seemed to be associated with Fe/Al oxides. Correlation plots, however, indicated that SOC contents were not linearly related to amounts of total Fe and Al oxides, weakly crystalline Fe and Al oxides, or strongly crystalline Fe oxides. The lack of linear correlations observed for these acidic soils may be caused by contributions from other extractable soil components and factors such as high organic loadings and insufficient amounts of Fe/Al oxides for interaction with SOC in topsoils and variable surface loadings of different organic inputs at different soil depths. Subsoil C/N ratios (∼18–21) were higher than those in extracted subsoil residues (∼9–17), suggesting that minerals other than Fe/Al oxides preferentially adsorbed N-rich microbially processed compounds. The OM associated with weakly and strongly crystalline Fe/Al oxides was chemically different, the latter generally having greater hydroxyl, aliphatic, carboxylate, and /or phenolic character and less carbohydrate character than the former. This research shows that interactions between Fe/Al oxides and SOM in redox-dynamic gley soils under different hydrological regimes are complex, and further investigations of SOC stabilization in these systems using selective dissolution and other complementary techniques are required.

Relating microfeatures of soil organic matter to C stabilisation: optical microscopy, SEM-EDS, abiotic oxidation

We investigated the relationships between microscale distribution of soil organic matter (SOM) features and their stability by combining optical microscopy, SEM-EDS analysis and NaClO oxidation of soil thin sections on five soils from Harwood Forest in Northumberland (UK) differently affected by water stagnation. Plant organs at different stages of decomposition and amorphous organic matter were observed by optical microscopy in all samples. SOM microfeature distribution, size of SOM features and the relation with the C-to-N ratio suggested that amorphous features could be the end-products of organ transformation. SEM-EDS elemental analysis showed that amorphous material had higher Si/C, Al/C and Fe/C molar ratios than organs, clearly pointing to interactions with the soil inorganic phases, which contributed to SOM stabilisation. Soil porosity coupled with water stagnation seemed to affect the Fe–SOM interactions as a greater proportion of small water retention pores (10–50xa0μm) was associated with higher abundance of Fe-rich amorphous organic features. The higher chemical stability of amorphous features was confirmed by oxidation. After NaClO treatment, organs were almost totally removed, while amorphous organic material was less affected both morphologically and chemically. Our results demonstrate that in water-affected soils local environment defined by the pore system affects the distribution of SOM microfeatures and that the highest resistance to oxidation of the amorphous features is attributable to the formation of organic–inorganic associations. The proposed combined approach seems to be a promising mean to investigate SOM dynamics by relating features to stability.

Assessment of physico-chemical properties and metal contents of water and sediments of Bodo Creek, Niger Delta, Nigeria

Some physico-chemical properties and the concentrations of the metals Fe, Mn, Ni, Cd, Cr, Co, Cu, Pb, and Zn in water and sediments were examined from September 2011 to January 2012 in Bodo Creek, where oil spills have been recurrent. Temperature, pH, total dissolved solid, conductivity, salinity, dissolved oxygen, biological oxygen demand (BOD), chemical oxygen demand (COD), total hardness, sulfate, nitrate, and phosphate were determined in surface water. Particle size, total organic matter (TOM), and pH were also determined in the sediments. The parameters were within permissible limits except the mean values of BOD, COD, total hardness, and sulfate that exceeded levels permissible for domestic use. The sediments consisted mainly of sand, with TOM ranging from 0.2% to 5.5%. With the exception of cadmium that was below detection limit, metal levels (mg kg−1) in the sediments were 12 (Mn), 1070 (Fe), 10 (Cu), 10 (Zn), 5.3 (Cr), 1.1 (Pb), 1.0 (Ni), and 0.5 (Co) while in water they were 24, 98, 21, 6.9, 4.0, 0.6, 0.18, and 0.16, respectively. The latter were higher than World Health Organization recommended permissible levels for both surface and drinking water.

25 – Anthropogenic Features

Publisher Summary nThis chapter discusses anthropogenic features. There are many challenges in developing through micromorphology, an understanding of soils and regoliths that have been influenced by direct human interventions, the application of micromophology to Anthrosols and Technosols may lead to better understanding of both their past and future management. Various classifications for risk assessment of contaminated land have been developed and may be furthered through use of soil micromorphology. In both the Anthrosol and Technosol contexts, confounding the typical questions posed to the micromorphologist on the identification of the type, nature and intensity of these human interventions are many process-led issues. Seasonal changes, and the different rates of change for natural and anthropogenic processes operating in a single soil profile, create many localized phenomena and localized alterations of different soil constituents.

Characterising the morphological properties and surface composition of radium contaminated particles: a means of interpreting origin and deposition

Radioactive hot particles that occur in the environment present specific challenges for health and environmental regulators as often their small size makes them difficult to detect, and they are easily dispersed and accidentally ingested or inhaled by members of the public. This study of nine hot particles recovered from the beach at Dalgety Bay, UK, uses a combination of gamma spectrometry, imaging microscopy and SEM-EDX in order to characterise their morphology and surface composition, thereby helping to identify their origin and source characteristics. The nine particles analysed showed great heterogeneity in their activities, physical form and elemental composition. The particle activities were dominated by (226)Ra and its daughters. Three distinct grouping of particles were identified based on their morphology (artefact, glassy and metal-rich), whilst four distinct groupings (artefact, glassy, angular and porphyric, rounded and highly porous) were identified based on morphology and surface properties as seen in the SEM. Whilst the artefact particles were little altered, the other particles showed evidence of incineration. All particles were in a size and/or shape class vulnerable to wind- or water-mediated transport. No correlations were found between morphology and chemical composition. SEM-EDX analysis revealed C, Si, Zn, Fe, Ca are common in the particles together with Ba, Ni, Pb, Cu, Mn and Ti. This is interpreted as the particles being derived from radium containing luminescent paint containing a Zn/S phosphor, a hydrocarbon base and other fillers and additives. Evidence of copper and steel alloys were also present in some particles, whilst one consisted of a hydrocarbon based capsule. The combination of techniques employed here has enabled interpretation of the origins of the radioactive particles and given insights into the potential movement of particles within the local environment.

MMI partial extraction geochemistry for the resolution of anthropogenic activities across the archaeological Roman town of Calleva Atrebatum

Sixty three soils samples, fourteen samples of previously excavated archaeological material, and five background soil samples taken at the Silchester Roman Town of Calleva Atrebatum in the County of Hampshire, United Kingdom were analysed by the Mobile Metal Ion (MMI) method for a total of fifty three elements. Samples from within the town walls showed considerably higher concentrations than samples outside for many elements; Au, Ag, Cu and Sn were in extremely anomalous concentrations, Bi, Cd, Hg, Mo, P and Pb were anomalous and Sb and Zn in elevated concentrations. The overall pattern of element distribution is one of an annulus of higher elemental concentrations surrounding a centre of generally lower values centred on the previously excavated Forum basilica. The elements Zr, Ti, Th, Ti, Tl, Nb, Sn, Sc, Cr, Co, Sb, Bi, Ce, Nd (and all other REEs), show similar distributions to one another, and their distribution and that of the noble and base metals, as highlighted by various additive indices, is considered to be the result of metallurgical processing on site. The low values for most elements around the Forum basilica are the result of disturbance of the soil geochemical profile in this area by previous archaeological excavation.