John G Farmer

The University of Edinburgh, Edinburgh, Scotland, United Kingdom

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Publications (102)254.03 Total impact

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    ABSTRACT: The use of stable Pb isotope analyses in conjunction with recent (210Pb and anthropogenic radionuclide) chronologies has become a well-established method for evaluating historical trends in depositional fluxes and sources of atmospherically deposited Pb using archival records in lake sediment or peat cores. Such studies rely upon (i) simple radioactive disequilibrium between unsupported 210Pb and longer-lived members of the 238U decay series and (ii) well-defined values for the isotopic composition of contaminant Pb and indigenous Pb in the study area. However, areas of high natural radioactivity can present challenging environments for such studies, with potential complications arising from more complex disequilibria in the 238U decay series and the occurrence, at local or regional level, of anomalous, ill-defined stable isotope ratios due to the presence of elevated levels of radiogenic Pb.
    Geochimica et Cosmochimica Acta 02/2015; 156. DOI:10.1016/j.gca.2015.02.003 · 4.25 Impact Factor
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    ABSTRACT: The Mae Tao watershed, northwest Thailand, has become contaminated with cadmium (Cd) as a result of zinc ore extraction (Padaeng deposit) in the nearby Thanon-Thongchai mountains. Consumption of contaminated rice has led to documented human health impacts. The aim of this study was to elucidate transfer pathways from creek and canal waters to the paddy field soils near Baan Mae Tao Mai village and to determine the relationship between Cd speciation in the soil and uptake by rice plants. Transfer mainly occurred in association with particulate matter during flooding and channel dredging and, in contrast with many other studies, most of the soil Cd was associated with exchangeable and carbonate-bound fractions. Moreover, there was a linear relationship between soil total Cd and rice grain Cd (R2 = 0.715), but a stronger relationship between both the Tessier-exchangeable soil Cd and the BCR-exchangeable soil Cd and rice grain Cd (R2 = 0.898 and 0.862, respectively).
    Environmental Pollution 04/2014; 187:153–161. DOI:10.1016/j.envpol.2014.01.006 · 3.73 Impact Factor
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    ABSTRACT: Extensive Cd contamination of paddy soils in Tak Province, western Thailand, a consequence of Zn mining activities, was first established in 2005 and medical studies showed that the health of local communities was being impaired. Mae Tao, Tak Province, comprising many paddy fields and irrigation canals, has been selected for this study of the geochemical transformation of Cd from the contamination source in the mountainous region to the east of the study site through the community irrigation system to the paddy soils. The aim of this research is to (i) investigate the geochemical transformation of Cd as it is transported from the main irrigation creek through the canals and to the paddy fields, (ii) assess the availability of Cd to rice plants, which may be affected by both chemical and physical factors, and (iii) trial some practical treatments to minimise Cd concentrations in rice grains. Soils, irrigation canal sediments and water samples were collected during the dry season and at the onset of the rainy season. Rice samples were collected at harvesting time and samples of soil fertiliser were also obtained. Water samples were filtered, ultrafiltered and analysed by ICP-MS whilst sub-samples of dried, ground soils and sediments were first subjected to micro-wave assisted acid digestion (modified US EPA method 3052). XRD and SEM-EDX methods were used for mineralogical characterisation and selective chemical extractions have assisted in the characterisation of solid phase Cd associations. Soil Cd concentrations were in the range 2.5-87.6 µg g-1, with higher values being obtained for fields furthest from the main creek. Although current irrigation water Cd inputs are low (mean 1.9 μg L-1; flood period), high loads of suspended particles still contribute additional Cd (4.2-9.8 µg L-1) to the paddy fields. For bioavailability assessment by a 3-step BCR sequential extraction, 70-90% Cd was in the exchangeable; HOAc-extractable fraction. That indicated that most of the Cd was in water soluble, exchangeable and carbonate-bound forms. For the fields with highest Cd concentration, SEM-EDX analysis identified two forms of Cd, i.e. Cd-Clay and Cd-CaCO3, in good agreement with the sequential extraction data. The predominance of easily extractable forms in the paddy field soils suggests that Cd may be readily absorbed by the rice plants. After harvesting, the Cd concentration in rice grains ranged from 0.05-4.0 µg g-1 and the concentration trends across the group of 18 fields matched well with the soil Cd data. Rice from nine out of the 18 fields contained Cd at greater than the safe level of 0.4 µg g-1.
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    ABSTRACT: Recent increases in manganese (Mn) concentrations in surface waters, including drinking water supplies, have triggered renewed interest in its geochemical behaviour in freshwater systems. This study, involving analysis of bottom sediments and ultrafiltered water (stream, loch and sediment porewater) samples, identified changes in aqueous phase speciation of Mn upon entering the loch waters and during its transit from the inflow to the outflow of Loch Bradan, a drinking water reservoir in SW Scotland. Diffusion out of the bottom sediments during calm periods or mixing of porewaters with loch water during resuspension events also released Mn into the overlying waters. Although 65% Mn was in colloidal form (3 kDa-0.2 μm) in the main streamwater inflow at the western end, 57-66% was present in the <3 kDa fraction in the proximal loch waters, at least partly as a result of the release of Mn(2+) from the bottom sediments. Towards the outflow at the eastern end, however, the increase in the amount of Mn associated with large organic colloids (100 kDa-0.2 μm) correlated with the speciation of Mn in the bottom water and the bottom sediment porewaters. While the inflow waters do have some impact upon Mn speciation at the western end of the loch, it appears that within-loch processes have a greater impact on Mn speciation near the outflow. These findings emphasise the importance of understanding the geochemical controls on Mn behaviour in aquatic systems: it is clear that although Mn may be present as truly dissolved Mn(2+) in some parts of the loch, it can also be associated to a significant extent (35-47%) with large organic colloids. These findings are important not only with respect to water treatment but also in terms of understanding the likely consequences of climatic change which may exacerbate losses of Mn from the bottom sediments.
    Science of The Total Environment 03/2012; 424:239-50. DOI:10.1016/j.scitotenv.2012.02.028 · 3.16 Impact Factor
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    ABSTRACT: The human bioaccessibility of lead (Pb) in Pb-contaminated soils from the Glasgow area was determined by the Unified Bioaccessibility Research Group of Europe (BARGE) Method (UBM), an in vitro physiologically based extraction scheme that mimics the chemical environment of the human gastrointestinal system and contains both stomach and intestine compartments. For 27 soils ranging in total Pb concentration from 126 to 2160 mg kg(-1) (median 539 mg kg(-1)), bioaccessibility as determined by the 'stomach' simulation (pH ~1.5) was 46-1580 mg kg(-1), equivalent to 23-77% (mean 52%) of soil total Pb concentration. The corresponding bioaccessibility data for the 'stomach+intestine' simulation (pH ~6.3) were 6-623 mg kg(-1) and 2-42% (mean 22%) of soil Pb concentration. The soil (206)Pb/(207)Pb ratios ranged from 1.057 to 1.175. Three-isotope plots of (208)Pb/(206)Pb against (206)Pb/(207)Pb demonstrated that (206)Pb/(207)Pb ratios were intermediate between values for source end-member extremes of imported Australian Pb ore (1.04)--used in the manufacture of alkyl Pb compounds (1.06-1.10) formerly added to petrol--and indigenous Pb ores/coal (1.17-1.19). The (206)Pb/(207)Pb ratios of the UBM 'stomach' extracts were similar (<0.01 difference) to those of the soil for 26 of the 27 samples (r=0.993, p<0.001) and lower in 24 of them. A slight preference for lower (206)Pb/(207)Pb ratio was discernible in the UBM. However, the source of Pb appeared to be less important in determining the extent of UBM-bioaccessible Pb than the overall soil total Pb concentration and the soil phases with which the Pb was associated. The significant phases identified in a subset of samples were carbonates, manganese oxides, iron-aluminium oxyhydroxides and clays.
    Science of The Total Environment 09/2011; 409(23):4958-65. DOI:10.1016/j.scitotenv.2011.08.061 · 3.16 Impact Factor
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    ABSTRACT: Knowledge of the anthropogenic contribution to lead (Pb) concentrations in surface soils in high latitude ecosystems is central to our understanding of the extent of atmospheric Pb contamination. In this study, we reconstructed fallout of Pb at a remote sub-arctic region by using two ombrotrophic peat cores and assessed the extent to which this airborne Pb is able to explain the isotopic composition ((206)Pb/(207)Pb ratio) in the O-horizon of tundra soils. In the peat cores, long-range atmospheric fallout appeared to be the main source of Pb as indicated by temporal trends that followed the known European pollution history, i.e. accelerated fallout at the onset of industrialization and peak fallout around the 1960s-70s. The Pb isotopic composition of the O-horizon of podzolic tundra soil ((206)Pb/(207)Pb=1.170 ± 0.002; mean ± SD) overlapped with that of the peat ((206)Pb/(207)Pb=1.16 ± 0.01) representing a proxy for atmospheric aerosols, but was clearly different from that of the parent soil material ((206)Pb/(207)Pb=1.22-1.30). This finding indicated that long-range fallout of atmospheric Pb is the main driver of Pb accumulation in podzolic tundra soil. In O-horizons of tundra soil weakly affected by cryoturbation (cryosols) however, the input of Pb from the underlying mineral soil increased as indicated by (206)Pb/(207)Pb ratios of up to 1.20, a value closer to that of local soil minerals. Nevertheless, atmospheric Pb appeared to be the dominant source in this soil compartment. We conclude that Pb concentrations in the O-horizon of studied tundra soils - despite being much lower than in boreal soils and representative for one of the least exposed sites to atmospheric Pb contaminants in Europe - are mainly controlled by atmospheric inputs from distant anthropogenic sources.
    Science of The Total Environment 08/2011; 409(20):4344-50. DOI:10.1016/j.scitotenv.2011.07.005 · 3.16 Impact Factor
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    ABSTRACT: ²¹⁰Pb dating provides a valuable, widely used means of establishing recent chronologies for sediments and other accumulating natural deposits. The Constant Rate of Supply (CRS) model is the most versatile and widely used method for establishing ²¹⁰Pb chronologies but, when using this model, care must be taken to account for limitations imposed by sampling and analytical factors. In particular, incompatibility of finite values for empirical data, which are constrained by detection limit and core length, with terms in the age calculation, which represent integrations to infinity, can generate erroneously old ages for deeper sections of cores. The bias in calculated ages increases with poorer limit of detection and the magnitude of the disparity increases with age. The origin and magnitude of this effect are considered below, firstly for an idealized, theoretical ²¹⁰Pb profile and secondly for a freshwater lake sediment core. A brief consideration is presented of the implications of this potential artefact for sampling and analysis.
    Science of The Total Environment 03/2011; 409(7):1298-304. DOI:10.1016/j.scitotenv.2010.11.040 · 3.16 Impact Factor
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    ABSTRACT: Uranium associations with colloidal and truly dissolved soil porewater components from two Ministry of Defence Firing Ranges in the UK were investigated. Porewater samples from 2-cm depth intervals for three soil cores from each of the Dundrennan and Eskmeals ranges were fractionated using centrifugal ultrafiltration (UF) and gel electrophoresis (GE). Soil porewaters from a transect running downslope from the Dundrennan firing area towards a stream (Dunrod Burn) were examined similarly. Uranium concentrations and isotopic composition were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), respectively. The soils at Dundrennan were Fe- and Al-rich clay-loam soils whilst at Eskmeals, they were Fe- and Al-poor sandy soils; both, however, had similar organic matter contents due to the presence of a near-surface peaty layer at Eskmeals. These compositional features influenced the porewater composition and indeed the associations of U (and DU). In general, at Dundrennan, U was split between large (100kDa-0.2μm) and small (3-30kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10cm depth, association with large Fe/Al/organic colloids was considered to be a precursor to the removal of U from the Dundrennan porewaters to the solid phase. In contrast, the association of U with small organic colloids was largely responsible for inhibiting attenuation in the Eskmeals soils. Lateral migration of U (and DU) through near-surface Dundrennan soils will involve both large and small colloids but, at depth, transport of the smaller amounts of U remaining in the porewaters may involve large colloids only. For one of the Dundrennan cores the importance of redox-related processes for the re-mobilisation of DU was also indicated as Mn(IV) reduction resulted in the release of both Mn(II) and U(VI) into the truly dissolved phase.
    Science of The Total Environment 02/2011; 409(10):1854-66. DOI:10.1016/j.scitotenv.2011.01.011 · 3.16 Impact Factor
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    ABSTRACT: Cores from four Scottish ombrotrophic peat bogs were used to reconstruct the historical record of atmospheric vanadium (V) deposition in Scotland over the last 150 years. The general similarity of V and Pb concentration profile trends in (210)Pb-dated cores from each of the sites strongly suggested that V, like Pb, is essentially immobile in ombrotrophic peat. After allowance via use of the conservative element Ti for the contribution of soil dust V, the deposition of anthropogenic V was found to be greatest (∼ 1.3 to 2.0 mg m(-2) y(-1)) in the mid-20(th) century before decreasing to 0.1-0.3 mg m(-2) y(-1) in the early years of the 21(st) century. The latter values were in good agreement with directly measured atmospheric V fluxes at nearby sites, a finding also observed in the case of Pb. The decline in peat-core-derived fluxes for both V and Pb from 1970 to 2004, however, was not as large as the decline in official UK emission estimates for the two metals during this period. This, along with an order of magnitude discrepancy between the anthropogenic V/Pb ratios at the peat core surface and the higher values of the ratio for UK emissions in the early 2000s, suggests that the recently revised UK emissions data for V may perhaps still be overestimated and/or that some previously deposited Pb is being resuspended in the atmosphere.
    Journal of Environmental Monitoring 01/2011; 13(1):58-65. DOI:10.1039/c0em00492h · 2.09 Impact Factor
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    ABSTRACT: The Unified Bioaccessibility Method (UBM), which simulates the fluids of the human gastrointestinal tract, was used to assess the oral bioaccessibility of Cr in 27 Glasgow soils. These included several contaminated with Cr(VI), the most toxic form of Cr, from the past disposal of chromite ore processing residue (COPR). The extraction was employed in conjunction with the subsequent determination of the bioaccessible Cr by ICP-OES and Cr(VI) by the diphenylcarbazide complexation colorimetric procedure. In addition, Cr(III)-containing species were determined by (i) HPLC-ICP-MS and (ii) ICP-OES analysis of gel electrophoretically separated components of colloidal and dissolved fractions from centrifugal ultrafiltration of extracts. Similar analytical procedures were applied to the determination of Cr and its species in extracts of the <10 μm fraction of soils subjected to a simulated lung fluid test to assess the inhalation bioaccessibility of Cr. The oral bioaccessibility of Cr was typically greater by a factor of 1.5 in the 'stomach' (pH ~1.2) compared with the 'stomach+intestine' (pH ~6.3) simulation. On average, excluding two COPR-contaminated soil samples, the oral bioaccessibility ('stomach') was 5% of total soil Cr and, overall, similar to the soil Cr(VI) concentration. Chromium(VI) was not detected in the extracts, a consequence of pH- and soil organic matter-mediated reduction in the 'stomach' to Cr(III)-containing species, identified as predominantly Cr(III)-humic complexes. Insertion of oral bioaccessible fraction data into the SNIFFER human health risk assessment model identified site-specific assessment criteria (for residential land without plant uptake) that were exceeded by the soil total Cr (3680 mg kg(-1)) and Cr(VI) (1485 mg kg(-1)) concentration at only the most COPR-Cr(VI)-contaminated location. However, the presence of measurable Cr(VI) in the <10 μm fraction of the two most highly Cr(VI)-contaminated soils demonstrated that inhalation of Cr(VI)-containing dust remains the most potentially harmful exposure route.
    Science of The Total Environment 10/2010; 409(2):267-77. DOI:10.1016/j.scitotenv.2010.09.007 · 3.16 Impact Factor
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    ABSTRACT: The lead concentrations and isotopic ratios (206Pb/207Pb, 208Pb/206Pb, 208Pb/207Pb) of 31 rainwater (September 2006-December 2007) and 11 surface vegetation (moss, lichen, heather) samples (October 2007) from the rural upland catchment of Glensaugh in northeast Scotland and of nine bark samples (October 2007) from trees, predominantly Scots pine, in or near Glensaugh were determined. The mean 206Pb/207Pb ratios for rainwater in 2006 and 2007 were similar to those previously determined for 2000 to 2003 at Glensaugh, yielding an average mean annual value of 1.151+/-0.005 (+/-1 SD) for the period from 2000, when an outright ban on leaded petrol came into force in the UK, to 2007. The mean 206Pb/207Pb ratio (1.146+/-0.004; n=7) for surface vegetation near the top (430-450 m) of the catchment was not significantly different (Student's t test) from that of rainwater (1.148+/-0.017; n=24) collected over the 12-month period prior to vegetation sampling, but both were significantly different, at the 0.1% (i.e. p<0.001) and 1% (p<0.01) level, respectively, from the corresponding mean value (1.134+/-0.006; n=9) for the outermost layer of tree bark. When considered in conjunction with similar direct evidence for 2002 and indirect evidence (e.g. grass, atmospheric particulates, dated peat) for recent decades in the Glensaugh area, these findings confirm that the lead isotopic composition of surface vegetation, including that of suitably located moss, reflects that of the atmosphere while that of the outermost layer of Scots pine bark is affected by non-contemporaneous lead. The nature and relative extent of the different contributory sources of lead to the current UK atmosphere in the era of unleaded petrol, however, are presently not well characterised on the basis of lead isotopic measurements.
    Science of The Total Environment 08/2010; 408(17):3704-10. DOI:10.1016/j.scitotenv.2010.03.050 · 3.16 Impact Factor
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    ABSTRACT: The historical accumulation rates of mercury resulting from atmospheric deposition to four Scottish ombrotrophic peat bogs, Turclossie Moss (northeast Scotland), Flanders Moss (west-central), Red Moss of Balerno (east-central) and Carsegowan Moss (southwest), were determined via analysis of (210)Pb- and (14)C-dated cores up to 2000 years old. Average pre-industrial rates of mercury accumulation of 4.5 and 3.7 microg m(-2) y(-1) were obtained for Flanders Moss (A.D. 1-1800) and Red Moss of Balerno (A.D. 800-1800), respectively. Thereafter, mercury accumulation rates increased to typical maximum values of 51, 61, 77 and 85 microg m(-2) y(-1), recorded at different times possibly reflecting local/regional influences during the first 70 years of the 20th century, at the four sites (TM, FM, RM, CM), before declining to a mean value of 27+/-15 microg m(-2) y(-1) during the late 1990s/early 2000s. Comparison of such trends for mercury with those for lead and arsenic in the cores and also with direct data for the declining UK emissions of these three elements since 1970 suggested that a substantial proportion of the mercury deposited at these sites over the past few decades originated from outwith the UK, with contributions to wet and dry deposition arising from long-range transport of mercury released by sources such as combustion of coal. Confidence in the chronological reliability of these core-derived trends in absolute and relative accumulation of mercury, at least since the 19th century, was provided by the excellent agreement between the corresponding detailed and characteristic temporal trends in the (206)Pb/(207)Pb isotopic ratio of lead in the (210)Pb-dated Turclossie Moss core and those in archival Scottish Sphagnum moss samples of known date of collection. The possibility of some longer-term loss of volatile mercury released from diagenetically altered older peat cannot, however, be excluded by the findings of this study.
    Science of The Total Environment 08/2009; 407(21):5578-88. DOI:10.1016/j.scitotenv.2009.06.014 · 3.16 Impact Factor
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    ABSTRACT: Possible postdepositional As migration in ombrotrophic peat bogs was investigated by comparing depth profiles of As with those of Sb and Pb, two elements considered to be essentially immobile in peat, and those of redox-sensitive, potentially mobile nutrient elements such as Mn, Fe, P, and S in 210Pb-dated cores from four Scottish bogs. Concentration profiles of As were similar to those of Sb and Pb rather than these other elements, indicating that As is bound strongly to organic matter and is relatively immobile in ombrotrophic peat. Historical records of atmospheric anthropogenic As, Sb, and Pb deposition during the industrial and postindustrial periods were derived, site-specific maxima (up to 1.55, 1.33, and 45 mg m(-2) y(-1), respectively) occurring between the late 1890s and 1960s, reflecting emissions from diverse sources such as mining and smelting, coal combustion, and also, in the case of Pb, exhaust emissions from the use of leaded gasoline. Since the mid-1980s, fluxes of Pb decreased (4-7 fold) more rapidly than those of As and Sb (2-3 fold), attributable to both the gradual elimination of leaded gasoline and recent new sources of the latter elements. Relative trends in derived anthropogenic As, Sb, and Pb deposition largely agreed with other Scottish peat and moss archive records, direct measurements of deposition, and UK emissions, i.e., four different types of data source.
    Environmental Science and Technology 04/2009; 43(6):1756-62. DOI:10.1021/es802573e · 5.48 Impact Factor
  • John G. Farmer
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    ABSTRACT: The mobility and bioavailability of depleted uranium (DU) in soils at a UK Ministry of Defence (UK MoD) weapons testing range were investigated. Soil and vegetation were collected near a test-firing position and at eight points along a transect line extending approximately 200 m down-slope, perpendicular to the firing line, toward a small stream. Earthworms and porewaters were subsequently separated from the soils and both total filtered porewater (<0.2 microm) and discrete size fractions (0.2 microm-100 kDa, 100-30 kDa, 30-3 kDa, and <3 kDa)obtainedvia centrifugal ultrafiltration were examined. Uranium concentrations were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) for soils and ICP-mass spectrometry (MS) for earthworms and porewaters, while 235U:238U atom ratios were determined by multicollector (MC)-ICP-MS. Comparison of the porewater and earthworm isotopic values with those of the soil solids indicated that DU released into the environment during weapons test-firing operations was more labile and more bioavailable than naturally occurring U in the soils at the testing range. Importantly, DU was shown to be present in soil porewater even at a distance of approximately 185 m from the test-firing position and, along the extent of the transect was apparently associated with organic colloids.
    Environmental Science and Technology 12/2008; 42(24):9158-64. DOI:10.1021/es8013634 · 5.48 Impact Factor
  • John G Farmer, Richard Jarvis
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    ABSTRACT: Strategies for improving human health in contaminated situations have traditionally been based on restricting emissions, remedial reduction of exposure and, where appropriate and possible, medical reconnaissance of efficacy. We review these and the broader aspects of general public health approaches, including necessary understanding of epidemiology and the wider social context, before considering a specific local case study involving health issues associated with chromium-contaminated land and its remediation in an area of urban regeneration. The impact of remediation upon the common good, in its broadest environmental, health and socio-economic sense, including enhanced opportunities for members of the community to take personal responsibility for health-improving activities, should be taken into account in addition to conventional theoretical assessments and practical measurements of relief from environmental risk. Rapidly emerging toxicogenomic technologies may have a role to play in informing future risk assessment and remediation approaches in contaminated situations, although the ethical challenges of using personal genetic information could well be considerable.
    Environmental Geochemistry and Health 11/2008; 31(2):227-38. DOI:10.1007/s10653-008-9209-2 · 2.08 Impact Factor
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    ABSTRACT: Methods for the fractionation of aquatic colloids require careful application to ensure efficient, accurate and reproducible separations. This paper describes the novel combination of mild colloidal fractionation and characterisation methods, namely centrifugal ultrafiltration, gel electrophoresis and gel filtration along with spectroscopic (UV-visible) and elemental (Inductively Coupled Plasma-Optical Emission Spectroscopy, Inductively Coupled Plasma-Mass Spectrometry) analysis, an approach which produced highly consistent results, providing improved confidence in these methods. Application to the study of the colloidal and dissolved components of soil porewaters from one soil at a depleted uranium (DU)-contaminated site revealed uranium (U) associations with both large (100 kDa-0.2 microm) and small (3-30 kDa) humic colloids. For a nearby soil with lower organic matter content, however, association with large (100 kDa-0.2 microm) iron (Fe)-aluminium (Al) colloids in addition to an association with small (3-30 kDa) humic colloids was observed. The integrated colloid fractionation approach presented herein can now be applied with confidence to investigate U and indeed other trace metal migration in soil and aquatic systems.
    Science of The Total Environment 10/2008; 404(1):207-17. DOI:10.1016/j.scitotenv.2008.05.042 · 3.16 Impact Factor
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    ABSTRACT: Depleted uranium (DU) has become a soil contaminant of considerable concern in many combat zones and weapons-testing sites around the world, including locations in Europe, the Middle East and the USA, arising from its dispersion via the application of DU-bearing munitions. Once DU is released into the environment its mobility and bioavailability will, like that of other contaminants, largely depend on the type of associations it forms in soil and on the nature of the soil components to which it binds. In this study we used the BCR sequential extraction scheme to determine the partitioning of DU amongst soil fractions of texturally varying soils from locations affected by weapons-testing activities. Isotopic analyses (MC-ICP-MS and alpha-spectrometry) were performed to verify the presence of DU in whole soils and soil fractions and to determine any preferential partitioning of the contaminant. Results identified soil organic matter as being consistently the most important component in terms of DU retention, accounting for 30-100% of DU observed in the soils examined. However, at greater distances from known contamination points, DU was also found to be largely associated with the exchangeable fraction, suggesting that DU can be mobilised and transported by surface and near-surface water and does remain in an exchangeable (and thus potentially bioavailable) form in soils.
    Chemosphere 07/2008; 72(6):932-9. DOI:10.1016/j.chemosphere.2008.03.029 · 3.50 Impact Factor
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    ABSTRACT: Cores collected from ombrotrophic peat bogs in west central, east central, northeast and southwest Scotland were dated (14C, 210Pb) and analyzed (ICP-OES, ICP-MS) to derive and compare their historical records of atmospheric anthropogenic Pb deposition over the past 2500 years. On the basis of Pb isotopic composition (e.g., 206Pb/207Pb), clear indications of Pb contamination during the pre-Roman/Roman, post-Roman and medieval periods were attributed to the mining and smelting of Pb ores from Britain and elsewhere in Europe. Between the 17th and early 20th centuries, during the industrial period, the mining and smelting of indigenous Scottish Pb ores were the most important sources of anthropogenic Pb deposition at three of the sites. In contrast, at the most southerly site, influences from the use of both British Pb ores and imported Australian Pb ores (in more southern parts of Britain) since the late 19th century were evident. At each of the sites, Australian-Pb-influenced car exhaust emissions (from the 1930s to late 1990s), along with significant contributions from coal combustion (until the late 1960s and onset of the postindustrial period), were evident. Atmospheric anthropogenic Pb deposition across Scotland was greatest (∼10 to 40 mg m−2 a−1) between the late 1880s and late 1960s, increasing southward, declining to 0.44 to 5.7 mg m−2 a−1 by the early 2000s. The records from four peat bogs extend knowledge of the chronology of atmospheric Pb deposition trends across the northern hemisphere, there being general agreement with other environmental archive records from not only Scotland but also other countries in western Europe and Greenland. Nevertheless, during all periods investigated here, the isotopic composition of atmospheric Pb deposition across western Europe and Greenland exhibited variations in the relative importance of different sources of anthropogenic Pb, as well as some differences in timings and magnitudes of anthropogenic Pb contamination, arising from variations in local and regional sources of Pb deposition and possibly climatic regimes.
    Global Biogeochemical Cycles 06/2008; 22(2). DOI:10.1029/2007GB003059 · 4.53 Impact Factor
  • GeoCongress 2008; 03/2008

Publication Stats

2k Citations
254.03 Total Impact Points


  • 1989–2015
    • The University of Edinburgh
      • • School of GeoSciences
      • • School of Chemistry
      Edinburgh, Scotland, United Kingdom
  • 2006
    • Rice University
      Houston, Texas, United States
  • 1981–1990
    • University of Glasgow
      • Forensic Medicine and Science Section
      Glasgow, SCT, United Kingdom