Miranda Keith-Roach - Academia.edu (original) (raw)

Papers by Miranda Keith-Roach

FIA研究懇談会会誌, 2007

... Weir Quay 29 0.5 0.4 85 20 4. Conclusions A FI spectrophotometric method for thedetermination... more ... Weir Quay 29 0.5 0.4 85 20 4. Conclusions A FI spectrophotometric method for thedetermination of silicate in natural waters has been developed and provides reliable results in the presence of high concentrations of phosphate and arsenate. ...

This report provides: • a critical review of the current understanding of the interactions betwee... more This report provides: • a critical review of the current understanding of the interactions between polynaphthalene sulphonate (PNS) and polycarboxylate ether (PCE) superplasticizers and cement • conceptual models developed in Phreeqc to describe superplasticizer uptake and release processes • estimates of DOC and sulphonate concentrations in the porewater of low pH silica fume grout and concrete prepared with PNS or PCE superplasticizer for use in a spent nuclear fuel repository • risk-benefit scorecards describing the use of PNS and PCE superplasticizers in low pH silica fume grouts and concretes The literature review identifies that superplasticizers interact with hydrating cement minerals via adsorption, which results in a superplasticizing effect, and intercalation in organo-mineral phases (OMP). The balance between these interactions depends on the cement porewater sulphate concentration and the timing of superplasticizer addition to the cement. PNS is able to compete more effe...

Aqueous and solid phase interactions of radionuclides with organic complexing agents Estela Reino... more Aqueous and solid phase interactions of radionuclides with organic complexing agents Estela Reinoso-Maset Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites; however, the mechanisms of the interactions in complex environments are poorly understood. In this work, radionuclide speciation and sorption behaviour were investigated in order to identify interactions between four key radionuclides with different oxidation states (Cs{l) and Sr(ll) as important fission products; Th(IV) and U(VI) as representative actinides), three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid as common co-contaminants), and natural sand (as simple environmental solid phase). A UV spectrophotometric an...

Rare Earths Industry, 2016

This paper explores the environmental legislation and best available technique reference document... more This paper explores the environmental legislation and best available technique reference documents in place in the European Union to support the emerging European rare earth element (REE) industry. One of the issues for REE mining, beneficiation and processing is the radioactivity that can be associated with the ores, arising from the presence of elevated U and/or Th and their daughter products. Therefore, workers may need to be protected from radiation during the exploitation of REE resources, and the public protected by suitable disposal of the radioactive wastes produced. Potential regulatory gaps and best practices are identified, based on the experience of countries with a REE industry.

Journal of Nuclear Science and Technology, 2002

Abstract Authorised low level radioactive waste discharges to sea from the BNFL Sellafield reproc... more Abstract Authorised low level radioactive waste discharges to sea from the BNFL Sellafield reprocessing plant have led to the accumulation of a wide range of radionuclides in intertidal sediments. The distributions of Pu and Am suggest that these elements are largely immobile in the sediments. Little information can be obtained from most U isotopes but 236U shows a very clear pattern which can be related to changes in reprocessing operations at Sellafield. The profile distribution of 237Np appears not to reflect the likely discharge history, suggesting that this element is mobile. A more detailed study of transuranic element concentrations in sediment pore waters shows that only about 1% of the sediment inventories is in the solution phase. There is an annual cycle in dissolved Pu concentrations although there appears to be no trend in Np or Am.

Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in o... more Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites [1]; however, the mechanisms of the interactions in complex environments are poorly understood [2]. In this work, radionuclide speciation was explored alongside sorption behaviour, to identify ternary interactions between radionuclides, organic complexing agents and sand as a representative environmental solid phase. Four key radionuclides encompassing different oxidation states (Cs and Sr as important fission products; Th and U(VI) as representative actinides) and three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid) were selected for this project. Electrospray ionisation-mass spectrometry (ESI-MS) was used to characterise the speciation of radionuclide complexes over the pH range 4 to 10. Interactions with sand were examined at circumneutral pH using inductively coupled plasma-mass spectrometry (ICP-MS) and dissolved organic carbon analysis. The results showed that Sr, Th and U interacted with all three ligands and complexation affected their sorption to sand, even in the presence of a seven-fold excess of natural DOC. With EDTA and NTA the solution phase species were identified as: [SrH 2 EDTA] and [SrNTA]-; [ThEDTA] and [ThNTA 2 ] 2-; and [(UO 2) 2 EDTA] and [UO 2 NTA]-. These neutral and anionic species interacted with the sand to a greater extent than the uncomplexed radionuclides, thus complexation lowers radionuclide solubility. With picolinate, the cationic [Cs 2 Pic] + and [Sr 2 Pic 3 ] + species were observed by ESI-MS. The increased solubility of Cs was consistent with this species; however, picolinate did not impact on the sorption of Sr. These results will be explored in the context of sorption kinetics, emphasizing the mechanisms by which the organic co-contaminants affect radionuclide mobility in the environment.

Journal of Soils and Sediments, 2014

ABSTRACT Estimates of beryllium-7 (Be-7) enrichment in soil particle size fractions are important... more ABSTRACT Estimates of beryllium-7 (Be-7) enrichment in soil particle size fractions are important for correction in existing soil redistribution models. Little attention has been given to documenting methods of estimating Be-7 enrichment and assessing differences in enrichment between soil types in the context of soil redistribution modelling. Here, we detail a method for estimating Be-7 enrichment and correcting soil redistribution estimates. Beryllium from a solution of BeCl2 was adsorbed to two soils with contrasting texture using a batch procedure. Soil fractions were separated by settling according to Stokes' Law, and samples of bulk and settled fractions were digested and analysed for Be concentration and for specific surface area. Both soils demonstrated increasing enrichment of Be with increasing specific surface area. There was a marked difference in enrichment between the soil types with the coarse soil showing greater enrichment in the finer fractions. Calculated enrichment ratios for the coarse soil more than doubled between subfractions of the < 63 mu m class. Failure to account for the selective transport of fractions during soil redistribution studies could incur substantial errors in soil erosion estimates. Stable Be provides a practical means of estimating Be-7 enrichment in soil and subsequent corrections can be incorporated into the conversion model where it is proposed that corrections should be applied to the inventory deficit at each eroding point. The marked difference in enrichment between soil types in these experiments suggested that characterising enrichment and associated correction factors should be done on a site-specific basis. Implementation of the particle size correction procedures requires additional field and laboratory data to standard application of the established soil erosion conversion model.

Radioactivity in the Environment, 2002

Publisher Summary This chapter discusses microbial interactions with radionuclides. It is importa... more Publisher Summary This chapter discusses microbial interactions with radionuclides. It is important to understand microorganisms' adaptability and ability to survive, especially in hostile environments—such as highly polluted sites and waste repositories. There are many different biochemical and physiological processes that can allow microorganisms to interact with radionuclides, both directly and indirectly, and these are dependent both on the properties of the chemical species and on the microbial consortia involved. As the physicochemical environment affects the chemistry of the radionuclides, the microbial community and, particularly, the interplay between them are essential to adopt an integrated approach. Before the effects of any microbial community or culture can be assessed or predicted, its fundamental diversity and robustness must be understood. As microbial life adapts to polluted conditions, mechanisms evolve to protect the species from radioactive or heavy metal contaminants. The interactions of microbes with their environment, the degree to which they affect the chemistry of the system as whole, and the specific ways they interact with major and trace metals are discussed in the chapter.

Talanta, 2005

Phosphorus is an important macronutrient and the accurate determination of phosphorus species in ... more Phosphorus is an important macronutrient and the accurate determination of phosphorus species in environmental matrices such as natural waters and soils is essential for understanding the biogeochemical cycling of the element, studying its role in ecosystem health and monitoring compliance with legislation. This paper provides a critical review of sample collection, storage and treatment procedures for the determination of phosphorus species in environmental matrices. Issues such as phosphorus speciation, the molybdenum blue method, digestion procedures for organic phosphorus species, choice of model compounds for analytical studies, quality assurance and the availability of environmental CRMs for phosphate are also discussed in detail.

Biogeochemistry, 2002

Microbial activity within the environment can have distinct geochemicaleffects, and so changes in... more Microbial activity within the environment can have distinct geochemicaleffects, and so changes in a microbial community structure can result ingeochemical change. We examined seasonal changes in both the microbialcommunityand the geochemistry of an inter-tidal salt marsh in north-west England tocharacterise biogeochemical processes occurring at this site.Phospholipid fatty acid (PLFA) analysis of sediment samples collected atmonthly intervals was used to measure

Water Research, 2012

The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has bee... more The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has been studied using sand-packed columns and flow rates in the range of 20 e100 m y À1. The concentrations injected into the columns were in the range of 0.4e4 mM for Th and 4e40 mM for EDTA, and with EDTA:Th ratios in the range 1:1 to 10:1. The results show that EDTA can significantly increase Th transport, but two very different behaviours are observed at Th concentrations of 0.4 and 4 mM. At the lower concentration, Th breakthrough is retarded with respect to a conservative tracer, with a peak width that is consistent with a single K d value, followed by a longer tail, and the behaviour is very sensitive to the flow rate. However at 4 mM Th, the breakthrough peak appears near to that of the tracer, and the width of the peak is consistent with a distribution of K d values and/or a larger dispersivity than the tracer. Speciation and transport modelling have been used to interpret the data, and a model was developed that could explain the 0.4 mM behaviour. This suggests that ternary surface complexes are important in these systems, with at least two different species involved, although the complexity of Th speciation in these systems leads to significant uncertainty in the values of the equilibrium and kinetic parameters. For the 4 mM systems, the rapid transport observed could not be explained by a simple chemical model; instead it is likely that EDTA plays an important role in stabilising and transporting thorium colloids and clusters.

TrAC Trends in Analytical Chemistry, 2008

Understanding speciation is fundamental to predicting radionuclide behaviour and fate in the envi... more Understanding speciation is fundamental to predicting radionuclide behaviour and fate in the environment, and factors affecting speciation (pH, Eh and ligand availability) ultimately control radionuclide solubility and mobility. Speciation data are therefore required to predict the ...

The Analyst, 2001

Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in... more Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in order to test the robustness of the procedure and to carry out a comparison of two ICP-MS set-ups. A sector field instrument (MicroMass PT2) coupled with an ultrasonic nebuliser and a quadrupole ICP-MS (Perkin-Elmer Elan 6000) coupled with an electrothermal vaporisation (ETV) unit were used. The results showed that the radiochemical procedure was robust, removing Ru and Mo to acceptable levels, and that the two set-ups gave results that were in agreement. The correlation coefficient between the sets of 11 results was 1.0 +/- 0.05. The importance of establishing the matrix effect when using an ETV is discussed.

Science of The Total Environment, 2011

A depth profile of (239)Pu and (240)Pu specific activities and isotope ratios was determined in a... more A depth profile of (239)Pu and (240)Pu specific activities and isotope ratios was determined in an inter-tidal sediment core from the Esk Estuary in the northeastern Irish Sea. The study site has been impacted with plutonium through routine radionuclide discharges from the Sellafield nuclear reprocessing plant in Cumbria, NW England. A pronounced sub-surface maximum of ~10 k Bq kg(-1) was observed for (239+240)Pu, corresponding to the peak in Pu discharge from Sellafield in 1973, with a decreasing trend with depth down to ~0.04 k Bq kg(-1) in the deeper layers. The depth profile of (239+240)Pu specific activities together with results from gamma-ray spectrometry for (137)Cs and (241)Am was compared with reported releases from the Sellafield plant in order to estimate a reliable sediment chronology. The upper layers (1992 onwards) showed higher (239+240)Pu specific activities than would be expected from the direct input of annual Sellafield discharges, indicating that the main input of Pu is from the time-integrated contaminated mud patch of the northeastern Irish Sea. The (240)Pu/(239)Pu atom ratios ranged from ~0.03 in the deepest layers to >0.20 in the sub-surface layers with an activity-weighted average of 0.181. The decreasing (240)Pu/(239)Pu atom ratio with depth reflects the changing nature of operations at the Sellafield plant from weapons-grade Pu production to reprocessing spent nuclear fuel with higher burn-up times in the late 1950s. In addition, recent annual (240)Pu/(239)Pu atom ratios in winkles collected during 2003-2008 from three stations along the Cumbrian coastline showed no significant spatial or temporal differences with an overall average of 0.204, which supports the hypothesis of diluted Pu input from the contaminated mud patch.

Science of The Total Environment, 2008

The potential migration of radionuclides is of concern at contaminated land sites and, in the lon... more The potential migration of radionuclides is of concern at contaminated land sites and, in the long term, waste repositories. Pathways of migration need to be characterised on a predictive level so that management decisions can be made with confidence. A pathway that is relatively poorly understood at present is radionuclide solubilisation due to complexation by organic complexing agents that are present in mixed radioactive wastes, and at radioactively contaminated land sites. Interactions of the complexing agents with radionuclides and the host environment, and the response to changes in the physicochemical conditions make their role far from simple to elucidate. In addition, chemical and biodegradation of the organic materials may be important. In this paper, key co-contaminant organics are reviewed with emphasis on their environmental fate and impact on radionuclide migration.

Science of The Total Environment, 2010

Depleted uranium (DU) is a by-product of nuclear fuel enrichment and is used in antitank penetrat... more Depleted uranium (DU) is a by-product of nuclear fuel enrichment and is used in antitank penetrators due to its high density, self-sharpening, and pyrophoric properties. Military activities have left a legacy of DU waste in terrestrial and marine environments, and there have been only limited attempts to clean up affected environments. Ten years ago, very little information was available on the dispersion of DU as penetrators hit their targets or the fate of DU penetrators left behind in environmental systems. However, the marked increase in research since then has improved our knowledge of the environmental impact of firing DU and the factors that control the corrosion of DU and its subsequent migration through the environment. In this paper, the literature is reviewed and consolidated to provide a detailed overview of the current understanding of the environmental behaviour of DU and to highlight areas that need further consideration.

Rapid Communications in Mass Spectrometry, 2012

RATIONALE: Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the ... more RATIONALE: Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the speciation of solutionphase metal complexes; however, the quantification of ternary systems is challenging due to the differences in the electrospray response of different species. Here, the Th-Mn-EDTA system was investigated to evaluate the capability of ESI-MS for quantifying the species present. METHODS: Increasingly complex mixtures of Th(IV), Mn(II) and EDTA were analysed using manual flow injection of samples into an HPLC grade water mobile phase delivered to an ion trap mass spectrometer fitted with an ESI interface (ThermoQuest Finnigan Mat LCQ). Mass spectra were obtained in the positive and negative ion modes over a mass-to-charge (m/z) range from 50-2000. RESULTS: The instrumental response to EDTA was affected by the addition of Th(NO 3) 4 but not MnCl 2 , while the response to both Th-EDTA and Mn-EDTA species was affected by addition of the other metal salt. Internal standards were also found to suppress signals to different extents. Therefore, each signal suppression was carefully quantified as the solution became more complex, and signal correction factors were used in conjunction with regular external calibration. Mixed metal signals were quantified adequately. CONCLUSIONS: This study showed the complexity of quantifying a ternary system involving different co-existing species. Nonetheless, the step-wise protocol developed provided quantitative data on the displacement of Mn from its EDTA complex by Th.

Radiation Research, 2012

FIG. 3. Level of biological organization of endpoints studied in papers on the effects of ionizin... more FIG. 3. Level of biological organization of endpoints studied in papers on the effects of ionizing radiation on aquatic invertebrates from 1950-2010. Articles examining two or more endpoints were counted multiple times.

Marine Environmental Research, 2010

Since the first nuclear weapons tests in the 1940s, pulsed inputs of plutonium isotopes have serv... more Since the first nuclear weapons tests in the 1940s, pulsed inputs of plutonium isotopes have served as excellent tracers for understanding sources, pathways, dynamics and the fate of pollutants and particles in the marine environment. Due to the well-defined spatial and temporal inputs of Pu, the long halflives of 240 Pu and 239 Pu and its unique chemical properties, Pu is a potential tracer for various physical and biogeochemical ocean processes, including circulation, sedimentation and biological productivity, and hence a means of assessing the impacts of global climate change. Due to the source dependency of the Pu isotopic signature, plutonium isotopes are beginning to be exploited as tools for the evaluation and improvement of regional and global ocean models that will enhance understanding of past and future changes in the oceans. This paper addresses the major sources of Pu and the physical and biogeochemical behaviour in the marine environment. Finally, the use of Pu isotopes as tracers for various oceanic processes (e.g. water mass transport, particle export, and sedimentation) is considered.

FIA研究懇談会会誌, 2007

... Weir Quay 29 0.5 0.4 85 20 4. Conclusions A FI spectrophotometric method for thedetermination... more ... Weir Quay 29 0.5 0.4 85 20 4. Conclusions A FI spectrophotometric method for thedetermination of silicate in natural waters has been developed and provides reliable results in the presence of high concentrations of phosphate and arsenate. ...

This report provides: • a critical review of the current understanding of the interactions betwee... more This report provides: • a critical review of the current understanding of the interactions between polynaphthalene sulphonate (PNS) and polycarboxylate ether (PCE) superplasticizers and cement • conceptual models developed in Phreeqc to describe superplasticizer uptake and release processes • estimates of DOC and sulphonate concentrations in the porewater of low pH silica fume grout and concrete prepared with PNS or PCE superplasticizer for use in a spent nuclear fuel repository • risk-benefit scorecards describing the use of PNS and PCE superplasticizers in low pH silica fume grouts and concretes The literature review identifies that superplasticizers interact with hydrating cement minerals via adsorption, which results in a superplasticizing effect, and intercalation in organo-mineral phases (OMP). The balance between these interactions depends on the cement porewater sulphate concentration and the timing of superplasticizer addition to the cement. PNS is able to compete more effe...

Aqueous and solid phase interactions of radionuclides with organic complexing agents Estela Reino... more Aqueous and solid phase interactions of radionuclides with organic complexing agents Estela Reinoso-Maset Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites; however, the mechanisms of the interactions in complex environments are poorly understood. In this work, radionuclide speciation and sorption behaviour were investigated in order to identify interactions between four key radionuclides with different oxidation states (Cs{l) and Sr(ll) as important fission products; Th(IV) and U(VI) as representative actinides), three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid as common co-contaminants), and natural sand (as simple environmental solid phase). A UV spectrophotometric an...

Rare Earths Industry, 2016

This paper explores the environmental legislation and best available technique reference document... more This paper explores the environmental legislation and best available technique reference documents in place in the European Union to support the emerging European rare earth element (REE) industry. One of the issues for REE mining, beneficiation and processing is the radioactivity that can be associated with the ores, arising from the presence of elevated U and/or Th and their daughter products. Therefore, workers may need to be protected from radiation during the exploitation of REE resources, and the public protected by suitable disposal of the radioactive wastes produced. Potential regulatory gaps and best practices are identified, based on the experience of countries with a REE industry.

Journal of Nuclear Science and Technology, 2002

Abstract Authorised low level radioactive waste discharges to sea from the BNFL Sellafield reproc... more Abstract Authorised low level radioactive waste discharges to sea from the BNFL Sellafield reprocessing plant have led to the accumulation of a wide range of radionuclides in intertidal sediments. The distributions of Pu and Am suggest that these elements are largely immobile in the sediments. Little information can be obtained from most U isotopes but 236U shows a very clear pattern which can be related to changes in reprocessing operations at Sellafield. The profile distribution of 237Np appears not to reflect the likely discharge history, suggesting that this element is mobile. A more detailed study of transuranic element concentrations in sediment pore waters shows that only about 1% of the sediment inventories is in the solution phase. There is an annual cycle in dissolved Pu concentrations although there appears to be no trend in Np or Am.

Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in o... more Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites [1]; however, the mechanisms of the interactions in complex environments are poorly understood [2]. In this work, radionuclide speciation was explored alongside sorption behaviour, to identify ternary interactions between radionuclides, organic complexing agents and sand as a representative environmental solid phase. Four key radionuclides encompassing different oxidation states (Cs and Sr as important fission products; Th and U(VI) as representative actinides) and three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid) were selected for this project. Electrospray ionisation-mass spectrometry (ESI-MS) was used to characterise the speciation of radionuclide complexes over the pH range 4 to 10. Interactions with sand were examined at circumneutral pH using inductively coupled plasma-mass spectrometry (ICP-MS) and dissolved organic carbon analysis. The results showed that Sr, Th and U interacted with all three ligands and complexation affected their sorption to sand, even in the presence of a seven-fold excess of natural DOC. With EDTA and NTA the solution phase species were identified as: [SrH 2 EDTA] and [SrNTA]-; [ThEDTA] and [ThNTA 2 ] 2-; and [(UO 2) 2 EDTA] and [UO 2 NTA]-. These neutral and anionic species interacted with the sand to a greater extent than the uncomplexed radionuclides, thus complexation lowers radionuclide solubility. With picolinate, the cationic [Cs 2 Pic] + and [Sr 2 Pic 3 ] + species were observed by ESI-MS. The increased solubility of Cs was consistent with this species; however, picolinate did not impact on the sorption of Sr. These results will be explored in the context of sorption kinetics, emphasizing the mechanisms by which the organic co-contaminants affect radionuclide mobility in the environment.

Journal of Soils and Sediments, 2014

ABSTRACT Estimates of beryllium-7 (Be-7) enrichment in soil particle size fractions are important... more ABSTRACT Estimates of beryllium-7 (Be-7) enrichment in soil particle size fractions are important for correction in existing soil redistribution models. Little attention has been given to documenting methods of estimating Be-7 enrichment and assessing differences in enrichment between soil types in the context of soil redistribution modelling. Here, we detail a method for estimating Be-7 enrichment and correcting soil redistribution estimates. Beryllium from a solution of BeCl2 was adsorbed to two soils with contrasting texture using a batch procedure. Soil fractions were separated by settling according to Stokes' Law, and samples of bulk and settled fractions were digested and analysed for Be concentration and for specific surface area. Both soils demonstrated increasing enrichment of Be with increasing specific surface area. There was a marked difference in enrichment between the soil types with the coarse soil showing greater enrichment in the finer fractions. Calculated enrichment ratios for the coarse soil more than doubled between subfractions of the < 63 mu m class. Failure to account for the selective transport of fractions during soil redistribution studies could incur substantial errors in soil erosion estimates. Stable Be provides a practical means of estimating Be-7 enrichment in soil and subsequent corrections can be incorporated into the conversion model where it is proposed that corrections should be applied to the inventory deficit at each eroding point. The marked difference in enrichment between soil types in these experiments suggested that characterising enrichment and associated correction factors should be done on a site-specific basis. Implementation of the particle size correction procedures requires additional field and laboratory data to standard application of the established soil erosion conversion model.

Radioactivity in the Environment, 2002

Publisher Summary This chapter discusses microbial interactions with radionuclides. It is importa... more Publisher Summary This chapter discusses microbial interactions with radionuclides. It is important to understand microorganisms' adaptability and ability to survive, especially in hostile environments—such as highly polluted sites and waste repositories. There are many different biochemical and physiological processes that can allow microorganisms to interact with radionuclides, both directly and indirectly, and these are dependent both on the properties of the chemical species and on the microbial consortia involved. As the physicochemical environment affects the chemistry of the radionuclides, the microbial community and, particularly, the interplay between them are essential to adopt an integrated approach. Before the effects of any microbial community or culture can be assessed or predicted, its fundamental diversity and robustness must be understood. As microbial life adapts to polluted conditions, mechanisms evolve to protect the species from radioactive or heavy metal contaminants. The interactions of microbes with their environment, the degree to which they affect the chemistry of the system as whole, and the specific ways they interact with major and trace metals are discussed in the chapter.

Talanta, 2005

Phosphorus is an important macronutrient and the accurate determination of phosphorus species in ... more Phosphorus is an important macronutrient and the accurate determination of phosphorus species in environmental matrices such as natural waters and soils is essential for understanding the biogeochemical cycling of the element, studying its role in ecosystem health and monitoring compliance with legislation. This paper provides a critical review of sample collection, storage and treatment procedures for the determination of phosphorus species in environmental matrices. Issues such as phosphorus speciation, the molybdenum blue method, digestion procedures for organic phosphorus species, choice of model compounds for analytical studies, quality assurance and the availability of environmental CRMs for phosphate are also discussed in detail.

Biogeochemistry, 2002

Microbial activity within the environment can have distinct geochemicaleffects, and so changes in... more Microbial activity within the environment can have distinct geochemicaleffects, and so changes in a microbial community structure can result ingeochemical change. We examined seasonal changes in both the microbialcommunityand the geochemistry of an inter-tidal salt marsh in north-west England tocharacterise biogeochemical processes occurring at this site.Phospholipid fatty acid (PLFA) analysis of sediment samples collected atmonthly intervals was used to measure

Water Research, 2012

The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has bee... more The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has been studied using sand-packed columns and flow rates in the range of 20 e100 m y À1. The concentrations injected into the columns were in the range of 0.4e4 mM for Th and 4e40 mM for EDTA, and with EDTA:Th ratios in the range 1:1 to 10:1. The results show that EDTA can significantly increase Th transport, but two very different behaviours are observed at Th concentrations of 0.4 and 4 mM. At the lower concentration, Th breakthrough is retarded with respect to a conservative tracer, with a peak width that is consistent with a single K d value, followed by a longer tail, and the behaviour is very sensitive to the flow rate. However at 4 mM Th, the breakthrough peak appears near to that of the tracer, and the width of the peak is consistent with a distribution of K d values and/or a larger dispersivity than the tracer. Speciation and transport modelling have been used to interpret the data, and a model was developed that could explain the 0.4 mM behaviour. This suggests that ternary surface complexes are important in these systems, with at least two different species involved, although the complexity of Th speciation in these systems leads to significant uncertainty in the values of the equilibrium and kinetic parameters. For the 4 mM systems, the rapid transport observed could not be explained by a simple chemical model; instead it is likely that EDTA plays an important role in stabilising and transporting thorium colloids and clusters.

TrAC Trends in Analytical Chemistry, 2008

Understanding speciation is fundamental to predicting radionuclide behaviour and fate in the envi... more Understanding speciation is fundamental to predicting radionuclide behaviour and fate in the environment, and factors affecting speciation (pH, Eh and ligand availability) ultimately control radionuclide solubility and mobility. Speciation data are therefore required to predict the ...

The Analyst, 2001

Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in... more Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in order to test the robustness of the procedure and to carry out a comparison of two ICP-MS set-ups. A sector field instrument (MicroMass PT2) coupled with an ultrasonic nebuliser and a quadrupole ICP-MS (Perkin-Elmer Elan 6000) coupled with an electrothermal vaporisation (ETV) unit were used. The results showed that the radiochemical procedure was robust, removing Ru and Mo to acceptable levels, and that the two set-ups gave results that were in agreement. The correlation coefficient between the sets of 11 results was 1.0 +/- 0.05. The importance of establishing the matrix effect when using an ETV is discussed.

Science of The Total Environment, 2011

A depth profile of (239)Pu and (240)Pu specific activities and isotope ratios was determined in a... more A depth profile of (239)Pu and (240)Pu specific activities and isotope ratios was determined in an inter-tidal sediment core from the Esk Estuary in the northeastern Irish Sea. The study site has been impacted with plutonium through routine radionuclide discharges from the Sellafield nuclear reprocessing plant in Cumbria, NW England. A pronounced sub-surface maximum of ~10 k Bq kg(-1) was observed for (239+240)Pu, corresponding to the peak in Pu discharge from Sellafield in 1973, with a decreasing trend with depth down to ~0.04 k Bq kg(-1) in the deeper layers. The depth profile of (239+240)Pu specific activities together with results from gamma-ray spectrometry for (137)Cs and (241)Am was compared with reported releases from the Sellafield plant in order to estimate a reliable sediment chronology. The upper layers (1992 onwards) showed higher (239+240)Pu specific activities than would be expected from the direct input of annual Sellafield discharges, indicating that the main input of Pu is from the time-integrated contaminated mud patch of the northeastern Irish Sea. The (240)Pu/(239)Pu atom ratios ranged from ~0.03 in the deepest layers to >0.20 in the sub-surface layers with an activity-weighted average of 0.181. The decreasing (240)Pu/(239)Pu atom ratio with depth reflects the changing nature of operations at the Sellafield plant from weapons-grade Pu production to reprocessing spent nuclear fuel with higher burn-up times in the late 1950s. In addition, recent annual (240)Pu/(239)Pu atom ratios in winkles collected during 2003-2008 from three stations along the Cumbrian coastline showed no significant spatial or temporal differences with an overall average of 0.204, which supports the hypothesis of diluted Pu input from the contaminated mud patch.

Science of The Total Environment, 2008

The potential migration of radionuclides is of concern at contaminated land sites and, in the lon... more The potential migration of radionuclides is of concern at contaminated land sites and, in the long term, waste repositories. Pathways of migration need to be characterised on a predictive level so that management decisions can be made with confidence. A pathway that is relatively poorly understood at present is radionuclide solubilisation due to complexation by organic complexing agents that are present in mixed radioactive wastes, and at radioactively contaminated land sites. Interactions of the complexing agents with radionuclides and the host environment, and the response to changes in the physicochemical conditions make their role far from simple to elucidate. In addition, chemical and biodegradation of the organic materials may be important. In this paper, key co-contaminant organics are reviewed with emphasis on their environmental fate and impact on radionuclide migration.

Science of The Total Environment, 2010

Depleted uranium (DU) is a by-product of nuclear fuel enrichment and is used in antitank penetrat... more Depleted uranium (DU) is a by-product of nuclear fuel enrichment and is used in antitank penetrators due to its high density, self-sharpening, and pyrophoric properties. Military activities have left a legacy of DU waste in terrestrial and marine environments, and there have been only limited attempts to clean up affected environments. Ten years ago, very little information was available on the dispersion of DU as penetrators hit their targets or the fate of DU penetrators left behind in environmental systems. However, the marked increase in research since then has improved our knowledge of the environmental impact of firing DU and the factors that control the corrosion of DU and its subsequent migration through the environment. In this paper, the literature is reviewed and consolidated to provide a detailed overview of the current understanding of the environmental behaviour of DU and to highlight areas that need further consideration.

Rapid Communications in Mass Spectrometry, 2012

RATIONALE: Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the ... more RATIONALE: Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the speciation of solutionphase metal complexes; however, the quantification of ternary systems is challenging due to the differences in the electrospray response of different species. Here, the Th-Mn-EDTA system was investigated to evaluate the capability of ESI-MS for quantifying the species present. METHODS: Increasingly complex mixtures of Th(IV), Mn(II) and EDTA were analysed using manual flow injection of samples into an HPLC grade water mobile phase delivered to an ion trap mass spectrometer fitted with an ESI interface (ThermoQuest Finnigan Mat LCQ). Mass spectra were obtained in the positive and negative ion modes over a mass-to-charge (m/z) range from 50-2000. RESULTS: The instrumental response to EDTA was affected by the addition of Th(NO 3) 4 but not MnCl 2 , while the response to both Th-EDTA and Mn-EDTA species was affected by addition of the other metal salt. Internal standards were also found to suppress signals to different extents. Therefore, each signal suppression was carefully quantified as the solution became more complex, and signal correction factors were used in conjunction with regular external calibration. Mixed metal signals were quantified adequately. CONCLUSIONS: This study showed the complexity of quantifying a ternary system involving different co-existing species. Nonetheless, the step-wise protocol developed provided quantitative data on the displacement of Mn from its EDTA complex by Th.

Radiation Research, 2012

FIG. 3. Level of biological organization of endpoints studied in papers on the effects of ionizin... more FIG. 3. Level of biological organization of endpoints studied in papers on the effects of ionizing radiation on aquatic invertebrates from 1950-2010. Articles examining two or more endpoints were counted multiple times.

Marine Environmental Research, 2010

Since the first nuclear weapons tests in the 1940s, pulsed inputs of plutonium isotopes have serv... more Since the first nuclear weapons tests in the 1940s, pulsed inputs of plutonium isotopes have served as excellent tracers for understanding sources, pathways, dynamics and the fate of pollutants and particles in the marine environment. Due to the well-defined spatial and temporal inputs of Pu, the long halflives of 240 Pu and 239 Pu and its unique chemical properties, Pu is a potential tracer for various physical and biogeochemical ocean processes, including circulation, sedimentation and biological productivity, and hence a means of assessing the impacts of global climate change. Due to the source dependency of the Pu isotopic signature, plutonium isotopes are beginning to be exploited as tools for the evaluation and improvement of regional and global ocean models that will enhance understanding of past and future changes in the oceans. This paper addresses the major sources of Pu and the physical and biogeochemical behaviour in the marine environment. Finally, the use of Pu isotopes as tracers for various oceanic processes (e.g. water mass transport, particle export, and sedimentation) is considered.