Stephen Hillier

• PhD
• Researcher at James Hutton Institute

Imogolite-type nanoparticles (ITN) are among the most extensively studied particles present in the Bs horizons of Podzols, as they are strongly associated with the adsorption processes of different anions in soils, including phosphate. The aim of this study was to assess the properties of ITN in soil, in order to increase the current knowledge of I...

Globally, there is a vast amount of coal mining waste (CMW) currently stored in spoil tips and tailing dams, presenting a significant source of potentially recoverable geomaterial for construction and geotechnical applications. In the literature, the heterogeneity in compositional and mechanical properties of CMW has often been mentioned, but their...

Halloysite nanotubes (often abbreviated as HNTs) are technologically important owing to their unique structural and morphological features. Some of these features pre-exist in the naturally hydrated halloysite-(10 Å) parent clay mineral; others may develop during its dehydration towards halloysite-(7 Å). This is the first infrared spectroscopic stu...

Nine halloysite nanotubes (HNTs) have been examined using scanning electron microscopy (SEM), atomic force microscopy (AFM) and (cross-sectional) transmission electron microscopy (TEM) to evaluate details of their external and internal morphologies. The samples span morphologies within the cylindrical to prismatic-polygonal framework proposed by Hi...

To help understand the bioaccumulation of Cd and Tl in beaver tissue, we examined the enrichment of these metals in vegetation available to the animals. Bark was collected from 40 species of trees and shrubs, along with a complete soil weathering profile, within a small watershed devoid of trace metal contamination. Weathering resulted in a 5x enri...

The establishment of the reference ambient background concentrations (ABCs) and quality reference values (QRVs) for trace metal (TM) concentrations in soils are required for the environmental assessment and any implementation of a protective action. This information is lacking for soils of the eastern Mitidja plain, which is an important agricultur...

Mineral composition is a fundamental feature that affects the properties and functions of soil through physical, chemical and biological interactions. However, comprehensive knowledge on the mineralogy of agricultural topsoils of Finland has been lacking. In this study, the mineral composition of 120 soil samples included in the national monitoring...

Ferruginous clay minerals in saturated soils and within hydrocarbon deposits often exist in a reduced state. Upon introduction of dissolved oxygen, or other oxidants, the clay minerals oxidise and changes in mineral surface charge and sorption capacity occur, resulting in changes in hydration as well as flux of intercalated species. Here we examine...

The Altar Stone at Stonehenge in Wiltshire, UK, is enigmatic in that it differs markedly from the other bluestones. It is a grey–green, micaceous sandstone and has been considered to be derived from the Old Red Sandstone sequences of South Wales. Previous studies, however, have been based on presumed derived fragments (debitage) that have been iden...

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 abundance...

The molecular speciation of phosphorus (P) in forest soils is of strategic importance for sustainable forest management. However, only limited information exists about soil P speciation in boreal forests. We combined P K-edge XANES spectroscopy, wet chemical P extractions, and X-ray diffraction analysis of soil minerals to investigate the vertical...

Colloids and nanoparticles leached from agricultural land are major carriers of potentially bioavailable nutrients with high mobility in the environment. Despite significant research effort s, accurate knowledge of macronutrients in colloids and nanoparticles is limited. We used multi-elemental synchrotron X-ray fluorescence (XRF) microscopy with m...

X-ray powder diffraction (XRPD) is found consistently to be the most accurate analytical technique for quantitative analysis of clay-bearing mixtures based on results from round-robin competitions such as the Reynolds Cup (RC). A range of computationally intensive approaches can be used to quantify phase concentrations from XRPD data, of which the...

This research has investigated fungal transformations of rock phosphate (RP) by geoactive fungi, with particular emphasis on Aspergillus niger. Direct hyphal interaction with RP particles induced morphological and mineralogical changes, as revealed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The formation of the oxal...

Detailed examination of the mineralogy of the Cretaceous McMurray Formation within a facies framework is used to assess the use of natural gamma-ray spectroscopy (NGS) and a pulsed neutron generator (PNG) tool in delineating variation in clay mineral and bitumen contents. Characterization of the mixed-layer (interstratified) clay phases in the McMu...

X-ray powder diffraction (XRPD) is consistently found to be the most accurate analytical technique for qualitative and quantitative mineralogy. For environmental samples such as rocks, sediments and soils that can contain a range of crystalline, disordered and amorphous components, quantitative XRPD methods implemented in Excel-based programs such...

Soil mineral compositions are often complex and spatially diverse, with each mineral exhibiting characteristic chemical properties that determine the intrinsic total concentration of soil nutrients and their phyto-availability. Defining soil mineral-nutrient relationships is therefore important for understanding the inherent fertility of soils for...

The adsorption and retention of phosphates in soil systems is of wide environmental importance, and understanding the surface chemistry of halloysite (a common soil clay mineral) is also of prime importance in many emerging technological applications of halloysite nanotubes (HNTs). The adsorption of phosphate anions on tubular halloysite (7 Å) has...

Soil organic carbon (SOC) is of key importance for soil functioning. It strongly impacts soil fertility, greenhouse gas emissions, nutrient retention, and contaminant degradation. The soil pore network determines how oxygen, water and nutrients are transported and exchanged in soil, and the architecture of the soil is therefore equally fundamental...

An R package for Full Pattern Summation of X-ray Powder Diffraction Data. Derives quantitative estimates of crystalline and amorphous phase concentrations in complex mixtures.

Reliable and accurate methods for estimating soil mineral weathering rates are required tools in evaluating the sustainability of increased harvesting of forest biomass and assessments of critical loads of acidity. A variety of methods that differ in concept, temporal and spatial scale, and data requirements are available for measuring weathering r...

Geophagy, the intentional consumption of earth materials, has been recorded in humans and other animals. It has been hypothesized that geophagy is an adaptive behavior, and that clay minerals commonly found in eaten soil can provide protection from toxins and/or supplement micronutrients. To test these hypotheses, we monitored chimpanzee geophagy u...

The Weaklaw vent in SE Scotland (East Lothian coast), inferred to be Namurian, produced lava spatter and volcanic bombs. The latter commonly contained ultramafic xenoliths. All were metasomatised by carbonic fluids rich in incompatible elements. The lavas and xenoliths are inferred to have been basanites and lherzolites prior to metasomatism. The a...

The late Ordovician is characterized by dramatic changes in global climate concurrent with a major mass extinction and possible changes in ocean redox. To further refine our understanding of these events, we present nitrogen and carbon isotope and abundance data from the Ordovician-Silurian (O-S) Global Boundary Stratotype Section and Point at Dob'...

Accurate estimates of base cation weathering rates in forest soils are crucial for policy decisions on sustainable biomass harvest levels and for calculations of critical loads of acidity. The PROFILE model is one of the most frequently used methods to quantify weathering rates, where the quantitative mineralogical input has often been calculated b...

Since landing on Mars in 2012 the CheMin instrument on board the Mars Science Laboratory (MSL) rover 'Curiosity' has analysed approximately 35 Martian soil and rock samples by X-ray powder diffraction (XRPD). The MSL XRPD measurements allow researchers to investigate the mineralogy of the Martian surface with particular focus on ancient aqueous env...

Minerals are the major component of most soils. Through direct inheritance from the parent material and subsequent alteration by chemical weathering, the soil mineral composition can be spatially diverse-reflecting the local geology, climate, and age of the soil. Each mineral present within the soil environment exhibits a characteristic chemical co...

X-ray powder diffraction (XRPD) is widely applied for the qualitative and quantitative analysis of soil mineralogy. In recent years, high-throughput XRPD has resulted in soil XRPD datasets containing thousands of samples. The efforts required for conventional approaches of soil XRPD data analysis are currently restrictive for such large data sets,...

Reliable and accurate methods for estimating soil mineral weathering rate are required tools in evaluating the sustainability of increased harvesting of forest biomass. A variety of methods that differ in concept, temporal and spatial scale and data requirements are available for measuring weathering rate. In this study, release rates of base catio...

This study explored the influence of uncertainty in quantitative mineralogy on PROFILE base cation (Ca, Mg, K, Na) weathering rates obtained using normative mineralogy compared to those obtained using measured mineralogy, which was taken as a reference. Weathering rates were determined for two sites, one in Northern (Flakaliden) and one in Southern...

Background and aimsThe effects of phosphorus and zinc applications on phosphorus and zinc concentrations in plants grown in different soil types have rarely been investigated. The aim of this study was to evaluate the effects of different soil types and phosphorus and zinc addition on growth and mineral element composition of red cabbage (Brassica...

Despite many reviews and original articles, the actual crystal structure of tubular halloysites remains unclear. Analysis of the structural features of defect-free kaolinite, refined by Bish & von Dreele (1989), shows that the ordered 1Tc kaolinite structure can be described equally well by the orthogonal layer cell {a0, b0, γ0} (γ0 = 90°) or by tw...

Data mining is often used to derive calibrations for soil property prediction from diffuse reflectance spectroscopy, facilitating inference of organic and mineral contributions to given properties. In contrast to spectroscopy, X-ray powder diffraction (XRPD) offers a more direct probe into the complexities of soil mineralogy. Here a national scale...

Polluted soils are a serious environmental risk worldwide and consist of millions of tons of mineral waste to be treated. In order to ensure their sustainable management, various remediation options must be considered. Hydraulic binder treatment is one option that may allow a stabilisation of pollution and thus offer a valorisation as secondary raw...

Geophagy, the deliberate consumption of earth materials, is common among humans and animals. However, its etiology and function(s) remain poorly understood. The major hypotheses about its adaptive functions are the supplementation of essential elements and the protection against temporary and chronic gastrointestinal (GI) distress. Because much les...

Quantitative soil mineralogy has been identified as a key factor influencing PROFILE weathering estimates, and is often calculated with normative methods, such as the “Analysis to Mineralogy” (‘A2M’) model. In Sweden and other countries, there is a large request for accurate base cation weathering estimates in order to establish how sustainable har...

The use of TEM and electron energy loss spectroscopy to determine levels of Fe³⁺ in solids at nanometre spatial resolution is well established. Here we assess this technique at the energy resolution of a monochromated electron source (0.3 eV) and with the capability of simultaneously acquiring core- and low-loss spectra for absolute energy calibrat...

The use of TEM and electron energy loss spectroscopy to determine levels of Fe3+ in solids at nanometre spatial resolution is well established. Here we assess this technique at the energy resolution of a monochromated electron source (0.3 eV) and with the capability of simultaneously acquiring core- and low-loss spectra for absolute energy calibrat...

Clay minerals and K feldspars were evaluated as sources of K in a Norway spruce stand (Picea abies (L.) Karst.) from the Skogaby experimental forest in southwest Sweden. The soil, developed in a Quaternary glacial till, has only 3–5% clay, and more than 95% of its K resides in feldspars. Ratios of K/Rb were assessed in interlayers of 2:1 clay miner...

With time, different soil-forming processes such as weathering, plant growth, accumulation of organic matter, and cultivation are likely to affect phosphorus (P) speciation. In this study, the depth distribution of P species was investigated for an agricultural clay soil, Lanna, Sweden. Small amounts of apatite-P was demonstrated in the topsoil whe...

Berea sandstone has been used by the petroleum industry as a representative model siliciclastic rock for a number of years. However, only incomplete data has been reported in the literature regarding its petrographic, geochemical, and petrophysical properties. In particular knowledge of the mineral distribution along the pore walls is particularly...

A new protocol for the quantitative determination of zeolite-group mineral compositions by electron probe microanalysis (wavelength-dispersive spectrometry) under ambient conditions, is presented. The method overcomes the most serious challenges for this mineral group, including new confidence in the fundamentally important Si-Al ratio. Development...

The cation exchange capacity (CEC) of seven well characterized halloysite nanotubes (HNTs) in the dehydrated 7 å form has been measured using a method based on cobalt hexammine exchange. In addition to unbuffered measurements, which varied between 2.9 and 9.3 cmol(+)kg⁻¹, CECs were also determined over a wide pH range and proton titration measureme...

Twenty one samples of relatively pure tubular halloysites (HNTs) from localities in Australia, China, New Zealand, Scotland, Turkey and the USA have been investigated by X-ray diffraction (XRD), infrared spectroscopy (IR) and electron microscopy. The halloysites occur in cylindrical tubular forms with circular or elliptical cross sections and curve...

Up until about 2005, the main application of halloysites had been as an alternative raw material to kaolinite for ceramics. Since then, however, there has been an exponential increase in studies aimed at applications of halloysite nanotubes, now widely referred to as HNTs (Fig. 1). The readily available and relatively cheap nanotubular forms of hal...

Twenty one samples of relatively pure tubular halloysites (HNTs) from localities in Australia, China, New Zealand, Scotland, Turkey and the USA have been investigated by X-ray diffraction (XRD), infrared spectroscopy (IR) and electron microscopy. The halloysites occur in cylindrical tubular forms with circular or elliptical cross sections and curve...

Previous research has demonstrated the transformation of metallic lead into pyromorphite in solid and liquid medium by several species of fungi. In this work, the soil fungus Paecilomyces javanicus was found to mediate formation of an unknown lead mineral phase after incubation in liquid media with lead shot. After 2 weeks' incubation, precipitated...

Purpose The purpose of this study is to define the relative contributions of fine (<10 μm) suspended sediment from tributaries within the Burdekin River catchment, NE Australia, and subsequent delivery to the Great Barrier Reef (GBR) lagoon. The temporal variability in these contributions was also investigated. Materials and methods Sediments in r...

A new protocol for the quantitative determination of zeolite group mineral compositions by electron probe microanalysis (EPMA, wavelength dispersive spectrometry) under ambient conditions, is presented. The method overcomes the most serious challenges for this mineral group, including new confidence in the fundamentally important Si-Al ratio. Devel...

Reconstructing variations in the intensity of chemical weathering in river basins is crucial if we are to understand how climate change impacts environment and whether there are feedbacks between climate and weathering processes. Quantifying chemical weathering is, however, a complicated process, involving a number of competing proxies. We compare...

Proportion of clay, fine silt and coarse sediment contributed by each sub-catchment tributary site (see Table 1 for site names). Circle size represents mean total suspended solids (TSS) concentration (mg L-1) over the study period. Major sub-catchment, reservoir and end-of-river sites are also included (represented by bold circle)

We present the rationale for a cross-disciplinary investigation addressing the ?Devonian plant hypothesis? which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramaticall...

Geoactive soil fungi were examined for their ability to release inorganic phosphate (Pi ) and mediate lead bioprecipitation during growth on organic phosphate substrates. Aspergillus niger and Paecilomyces javanicus grew in 5 mM Pb(NO3 )2 -containing media amended with glycerol 2-phosphate (G2P) or phytic acid (PyA) as sole P sources, and liberated...

We present the rationale for a cross-disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramaticall...

Fungi play important roles in biogeochemical processes such as organic matter decomposition, bioweathering of minerals and rocks, and metal transformations, and therefore influence elemental cycles for essential and potentially-toxic elements, e.g. P, S, Pb, and As. Arsenic is a potentially-toxic metalloid for most organisms, and naturally occurs i...

Applying by-products as soil amendments to agricultural systems is growing in popularity. We aimed to assess the efficacy of some contemporary by-products to provide nutrients to crops as well as the potential harm of adding toxic elements to the environment. Four different by-products widely available in Northern Europe were tested for their effec...

Geoactive soil fungi were investigated for phosphatase-mediated uranium precipitation during growth on an organic phosphorus source. Aspergillus niger and Paecilomyces javanicus were grown on modified Czapek-Dox medium amended with glycerol 2-phosphate (G2P) as sole P source and uranium nitrate. Both organisms showed reduced growth on uranium-conta...

The effectiveness of four by-products (biogas digestate, pot ale, rockdust and wood ash) as fertilisers of a perennial ryegrass (Lolium perenne)–red clover (Trifolium pratense) mixture in terms of biomass production, botanical composition and macro- and micronutrient concentrations was tested in an outdoor pot trial. This was carried out over two g...

Saprotrophic fungi were investigated for their bioweathering effects on the vanadium- and lead-containing insoluble apatite group mineral, vanadinite (Pb5(VO4)3Cl). Despite the insolubility of vanadinite, fungi exerted both biochemical and biophysical effects on the mineral including etching, penetration and formation of new biominerals. Lead oxala...

The use of kaolins in health has its origins in prehistoric times. Humans and other animals consume kaolin for gastrointestinal ailments, digestive enhancement, and possibly nutritional supplementation. Kaolins are effective as hemostatic wound dressings, because they can clot blood from traumatic injury, with little damage to tissue. Various forms...

Lead is a priority pollutant, and lead metal is widely found in the environment as a waterproofing structural component in roofing, fence post covers, venting and flashing, as well as in industrial and urban waste. However, little is known of microbial interactions with metallic lead. The objective of this research was to investigate fungal roles i...

Background and Aims Rising costs and pressure on supplies of commercial mineral fertilizers and increasing markets for organically produced foods and feeds have led to a growing interest in soil amendments to supply plant nutrients. Rockdust is a by-product of quarrying and its effectiveness to supply plants with nutrients has been a contested issu...

Enteropathogens released into the environment can represent a serious risk to public health. Soil clay content has long been known to have an important effect on enteropathogen survival in soil, generally enhancing survival. However, clay mineral composition in soils varies, and different clay minerals have specific physiochemical properties that w...

Six samples of 'Vermiculite' have been studied to investigate the mechanism of its well known but poorly understood property to exfoliate. The samples were analysed quantitatively by XRD to determine their precise mineralogical composition. Electron microprobe methods, including elemental mapping of native potassium and of caesium (introduced by ca...

Sediments in the Pearl River delta have the potential to record the weathering response of this river basin to climate change since 9.5 ka, most notably weakening of the Asian monsoon since the Early Holocene (~8 ka). Cores from the Pearl River delta show a clear temporal evolution of weathering intensity, as measured by K/Al, K/Rb and clay mineral...

Geophagy, the deliberate consumption of earth, is strongly associated with iron (Fe) deficiency. It has been proposed that geophagy may be practiced as a means to improve Fe status by increasing Fe intakes and, conversely, that geophagy may cause Fe deficiency by inhibiting Fe absorption. We tested these hypotheses by measuring Fe concentration and...

Different extraction methods are used world-wide in routine soil analysis to estimate long-term potassium (K) reserves for plants. In Sweden, K extracted with 2 M HCl at 100°C (KHCl) is frequently used, although with limited understanding of the phases extracted. In the present study, we quantified the effects of this extraction on soil minerals in...

In this work, several fungi with geoactive properties, including Aspergillus niger, Beauveria caledonica and Serpula himantioides, were used to investigate their potential bioweathering effects on zinc silicate and zinc sulfide ores used in zinc extraction and smelting, to gain understanding of the roles that fungi may play in transformations of su...

We analyzed sediment from Ocean Drilling Program (ODP) Site 1144 in the northern South China Sea to examine the weathering response of SE Asia to the strengthening of the East Asian Monsoon (EAM) since 14 ka. Our high-resolution record highlights the decoupling between continental chemical weathering, physical erosion and summer monsoon intensity....