Publications by authors named "Christopher Fuller"

43 Publications

Sediment Sources and Sealed-Pavement Area Drive Polycyclic Aromatic Hydrocarbon and Metal Occurrence in Urban Streams.

Environ Sci Technol 2022 Jan 19. Epub 2022 Jan 19.

U.S. Geological Survey, Helena, Montana 59601, United States.

Metals and polycyclic aromatic hydrocarbons (PAHs) are common pollutants in urban streambed sediment, yet their occurrence is highly variable and difficult to predict. To investigate sources of PAHs and metals to streambed sediment, we sampled pavement dust, soil, and streambed sediment in 10 urban watersheds in three regions of the United States and applied a fallout-radionuclide-based sediment-source analysis to quantify the pavement dust contribution to stream sediment (%dust). We also mapped the area of sealcoated pavement in each watershed (%sealed) to investigate the role of coal-tar pavement sealant (CTS) as a PAH source. Median total and carbon-normalized total PAH concentrations were significantly higher in streambed sediment in the Northeast (54.3 mg/kg and 2.71 mg/gOC) and Southeast (5.37 mg/kg and 1.36 mg/gOC), where CTS is commonly used, than in the Northwest (2.11 mg/kg and 0.071 mg/gOC), where CTS is rarely used. Generalized additive models indicated that %sealed and in some cases %dust significantly affected total PAH concentrations in streambed sediments. The %dust was a significant variable for common urban metals: Cu, Pb, and Zn. These findings advance our quantitative understanding of the role of pavement dust as a source and a vector of contaminants to urban streams.
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http://dx.doi.org/10.1021/acs.est.1c00414DOI Listing
January 2022

Prevalence and duration of detectable SARS-CoV-2 nucleocapsid antibodies in staff and residents of long-term care facilities over the first year of the pandemic (VIVALDI study): prospective cohort study in England.

Lancet Healthy Longev 2022 Jan 16;3(1):e13-e21. Epub 2021 Dec 16.

UCL Institute of Health Informatics, London, UK.

Background: Long-term care facilities (LTCFs) have reported high SARS-CoV-2 infection rates and related mortality, but the proportion of infected people among those who have survived, and duration of the antibody response to natural infection, is unknown. We determined the prevalence and stability of nucleocapsid antibodies (the standard assay for detection of previous infection) in staff and residents in LTCFs in England.

Methods: This was a prospective cohort study of residents 65 years or older and of staff 65 years or younger in 201 LTCFs in England between March 1, 2020, and May 7, 2021. Participants were linked to a unique pseudo-identifier based on their UK National Health Service identification number. Serial blood samples were tested for IgG antibodies against SARS-CoV-2 nucleocapsid protein using the Abbott ARCHITECT i-system (Abbott, Maidenhead, UK) immunoassay. Primary endpoints were prevalence and cumulative incidence of antibody positivity, which were weighted to the LTCF population. Incidence rate of loss of antibodies (seroreversion) was estimated from Kaplan-Meier curves.

Findings: 9488 samples were included, 8636 (91·0%) of which could be individually linked to 1434 residents and 3288 staff members. The cumulative incidence of nucleocapsid seropositivity was 34·6% (29·6-40·0) in residents and 26·1% (23·0-29·5) in staff over 11 months. 239 (38·6%) residents and 503 women (81·3%) were included in the antibody-waning analysis, and median follow-up was 149 days (IQR 107-169). The incidence rate of seroreversion was 2·1 per 1000 person-days at risk, and median time to reversion was 242·5 days.

Interpretation: At least a quarter of staff and a third of surviving residents were infected with SAR-CoV-2 during the first two waves of the pandemic in England. Nucleocapsid-specific antibodies often become undetectable within the first year following infection, which is likely to lead to marked underestimation of the true proportion of people with previous infection. Given that natural infection might act to boost vaccine responses, better assays to identify natural infection should be developed.

Funding: UK Government Department of Health and Social Care.
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http://dx.doi.org/10.1016/S2666-7568(21)00282-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8676418PMC
January 2022

Influence of wash aids on Bacillus spore removal from an asphalt parking lot using two spray-based washing methods.

J Appl Microbiol 2021 Dec 8. Epub 2021 Dec 8.

Homeland Security Materials Management Division, Center for Environmental Solutions and Emergency Response, U.S. EPA Office of Research and Development, Durham, North Carolina, USA.

Aims: The goal of this study was to measure the removal efficacy of Bacillus atrophaeus spores from a parking lot using spray-based washing methods (a pressure washer and a garden hose) and wash aids. B. atrophaeus is a commonly used nonpathogenic surrogate for B. anthracis, the causative agent of anthrax and a deadly bioterrorism agent that would cause major disruptions and damage to public health should it be disseminated over an urban area.

Methods And Results: Five wash aids (1 mM sodium chloride, an Instant Ocean® seawater solution, 0.01% Tween 20, 0.01% sodium dodecyl sulfate, and unamended tap water) were used along with two different spray sequences in this study. Across all treatment conditions, 3.7-6.4 log  colony forming unit were recovered in the runoff water, and 0.15%-23% of spores were removed from the surface of the parking lot.

Conclusions: Pressure washing removed more spores than the garden hose, and for both types of washing methods, the first pass removed more spores than the subsequent passes. The Instant Ocean and Tween 20 wash aids were found to significantly increase the percentage of spore removal when using the pressure washer, but the overall increase was only 1%-2% compared to the tap water alone.

Significance And Impact Of Study: This study provides public officials and emergency responders with baseline spore physical removal information for situations where a corrosive disinfectant might have a negative impact on the environment and washing is being considered as an alternative remediation approach.
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http://dx.doi.org/10.1111/jam.15405DOI Listing
December 2021

Changes in COVID-19 outbreak severity and duration in long-term care facilities following vaccine introduction, England, November 2020 to June 2021.

Euro Surveill 2021 11;26(46)

UCL Institute of Health Informatics, London, United Kingdom.

We describe the impact of changing epidemiology and vaccine introduction on characteristics of COVID-19 outbreaks in 330 long-term care facilities (LTCF) in England between November 2020 and June 2021. As vaccine coverage in LTCF increased and national incidence declined, the total number of outbreaks and outbreak severity decreased across the LTCF. The number of infected cases per outbreak decreased by 80.6%, while the proportion of outbreaks affecting staff only increased. Our study supports findings of vaccine effectiveness in LTCF.
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http://dx.doi.org/10.2807/1560-7917.ES.2021.26.46.2100995DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8603404PMC
November 2021

Investigation into the geometry and distribution of oil inclusions in sea ice using non-destructive X-ray microtomography and its implications for remote sensing and mitigation potential.

Mar Pollut Bull 2021 Dec 6;173(Pt A):112996. Epub 2021 Oct 6.

University of Manitoba, Winnipeg, MB, Canada. Electronic address:

As climate change brings reduced sea ice cover and longer ice-free summers to the Arctic, northern Canada is experiencing an increase in shipping and industrial activity in this sensitive region. Disappearing sea ice, therefore, makes the Arctic region susceptible to accidental releases of different types of oil and fuel pollution resulting in a pressing need for the development of appropriate scientific knowledge necessary to inform regulatory policy formulation. In this study, we examine the microstructure of the surficial layers of sea ice exposed to oil using X-ray microtomography. Through analysis, 3D imaging of the spatial distribution of the ice's components (brine, air, and oil) were made. Additional quantitative information regarding the size, proximity, orientation, and geometry of oil inclusions were computed to ascertain discernable relationships between oil and the other components of the ice. Our results indicate implications for airborne remote sensing and bioremediation of the upper sea ice layers.
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http://dx.doi.org/10.1016/j.marpolbul.2021.112996DOI Listing
December 2021

Conformational control of Cas9 by CRISPR hybrid RNA-DNA guides mitigates off-target activity in T cells.

Mol Cell 2021 09;81(17):3637-3649.e5

Caribou Biosciences, Inc., 2929 Seventh Street, Suite 105, Berkeley, CA 94710, USA. Electronic address:

The off-target activity of the CRISPR-associated nuclease Cas9 is a potential concern for therapeutic genome editing applications. Although high-fidelity Cas9 variants have been engineered, they exhibit varying efficiencies and have residual off-target effects, limiting their applicability. Here, we show that CRISPR hybrid RNA-DNA (chRDNA) guides provide an effective approach to increase Cas9 specificity while preserving on-target editing activity. Across multiple genomic targets in primary human T cells, we show that 2'-deoxynucleotide (dnt) positioning affects guide activity and specificity in a target-dependent manner and that this can be used to engineer chRDNA guides with substantially reduced off-target effects. Crystal structures of DNA-bound Cas9-chRDNA complexes reveal distorted guide-target duplex geometry and allosteric modulation of Cas9 conformation. These structural effects increase specificity by perturbing DNA hybridization and modulating Cas9 activation kinetics to disfavor binding and cleavage of off-target substrates. Overall, these results pave the way for utilizing customized chRDNAs in clinical applications.
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http://dx.doi.org/10.1016/j.molcel.2021.07.035DOI Listing
September 2021

Vaccine effectiveness of the first dose of ChAdOx1 nCoV-19 and BNT162b2 against SARS-CoV-2 infection in residents of long-term care facilities in England (VIVALDI): a prospective cohort study.

Lancet Infect Dis 2021 11 23;21(11):1529-1538. Epub 2021 Jun 23.

UCL Institute of Health Informatics, UCL, London, UK. Electronic address:

Background: The effectiveness of SARS-CoV-2 vaccines in older adults living in long-term care facilities is uncertain. We investigated the protective effect of the first dose of the Oxford-AstraZeneca non-replicating viral-vectored vaccine (ChAdOx1 nCoV-19; AZD1222) and the Pfizer-BioNTech mRNA-based vaccine (BNT162b2) in residents of long-term care facilities in terms of PCR-confirmed SARS-CoV-2 infection over time since vaccination.

Methods: The VIVALDI study is a prospective cohort study that commenced recruitment on June 11, 2020, to investigate SARS-CoV-2 transmission, infection outcomes, and immunity in residents and staff in long-term care facilities in England that provide residential or nursing care for adults aged 65 years and older. In this cohort study, we included long-term care facility residents undergoing routine asymptomatic SARS-CoV-2 testing between Dec 8, 2020 (the date the vaccine was first deployed in a long-term care facility), and March 15, 2021, using national testing data linked within the COVID-19 Datastore. Using Cox proportional hazards regression, we estimated the relative hazard of PCR-positive infection at 0-6 days, 7-13 days, 14-20 days, 21-27 days, 28-34 days, 35-48 days, and 49 days and beyond after vaccination, comparing unvaccinated and vaccinated person-time from the same cohort of residents, adjusting for age, sex, previous infection, local SARS-CoV-2 incidence, long-term care facility bed capacity, and clustering by long-term care facility. We also compared mean PCR cycle threshold (Ct) values for positive swabs obtained before and after vaccination. The study is registered with ISRCTN, number 14447421.

Findings: 10 412 care home residents aged 65 years and older from 310 LTCFs were included in this analysis. The median participant age was 86 years (IQR 80-91), 7247 (69·6%) of 10 412 residents were female, and 1155 residents (11·1%) had evidence of previous SARS-CoV-2 infection. 9160 (88·0%) residents received at least one vaccine dose, of whom 6138 (67·0%) received ChAdOx1 and 3022 (33·0%) received BNT162b2. Between Dec 8, 2020, and March 15, 2021, there were 36 352 PCR results in 670 628 person-days, and 1335 PCR-positive infections (713 in unvaccinated residents and 612 in vaccinated residents) were included. Adjusted hazard ratios (HRs) for PCR-positive infection relative to unvaccinated residents declined from 28 days after the first vaccine dose to 0·44 (95% CI 0·24-0·81) at 28-34 days and 0·38 (0·19-0·77) at 35-48 days. Similar effect sizes were seen for ChAdOx1 (adjusted HR 0·32, 95% CI 0·15-0·66) and BNT162b2 (0·35, 0·17-0·71) vaccines at 35-48 days. Mean PCR Ct values were higher for infections that occurred at least 28 days after vaccination than for those occurring before vaccination (31·3 [SD 8·7] in 107 PCR-positive tests vs 26·6 [6·6] in 552 PCR-positive tests; p<0·0001).

Interpretation: Single-dose vaccination with BNT162b2 and ChAdOx1 vaccines provides substantial protection against infection in older adults from 4-7 weeks after vaccination and might reduce SARS-CoV-2 transmission. However, the risk of infection is not eliminated, highlighting the ongoing need for non-pharmaceutical interventions to prevent transmission in long-term care facilities.

Funding: UK Government Department of Health and Social Care.
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http://dx.doi.org/10.1016/S1473-3099(21)00289-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8221738PMC
November 2021

Incidence, healthcare-seeking behaviours, antibiotic use and natural history of common infection syndromes in England: results from the Bug Watch community cohort study.

BMC Infect Dis 2021 Jan 22;21(1):105. Epub 2021 Jan 22.

Institute of Health informatics, UCL, 222 Euston Road, London, NW1 2DA, UK.

Background: Better information on the typical course and management of acute common infections in the community could inform antibiotic stewardship campaigns. We aimed to investigate the incidence, management, and natural history of a range of infection syndromes (respiratory, gastrointestinal, mouth/dental, skin/soft tissue, urinary tract, and eye).

Methods: Bug Watch was an online prospective community cohort study of the general population in England (2018-2019) with weekly symptom reporting for 6 months. We combined symptom reports into infection syndromes, calculated incidence rates, described the proportion leading to healthcare-seeking behaviours and antibiotic use, and estimated duration and severity.

Results: The cohort comprised 873 individuals with 23,111 person-weeks follow-up. The mean age was 54 years and 528 (60%) were female. We identified 1422 infection syndromes, comprising 40,590 symptom reports. The incidence of respiratory tract infection syndromes was two per person year; for all other categories it was less than one. 194/1422 (14%) syndromes led to GP (or dentist) consultation and 136/1422 (10%) to antibiotic use. Symptoms usually resolved within a week and the third day was the most severe.

Conclusions: Most people reported managing their symptoms without medical consultation. Interventions encouraging safe self-management across a range of acute infection syndromes could decrease pressure on primary healthcare services and support targets for reducing antibiotic prescribing.
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http://dx.doi.org/10.1186/s12879-021-05811-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820521PMC
January 2021

Transport and speciation of uranium in groundwater-surface water systems impacted by legacy milling operations.

Sci Total Environ 2021 Mar 2;761:143314. Epub 2020 Nov 2.

Conserve-Prosper LLC, Grand Junction, CO 81507, USA.

Growing worldwide concern over uranium contamination of groundwater resources has placed an emphasis on understanding uranium transport dynamics and potential toxicity in groundwater-surface water systems. In this study, we utilized novel in-situ sampling methods to establish the location and magnitude of contaminated groundwater entry into a receiving surface water environment, and to investigate the speciation and potential bioavailability of uranium in groundwater and surface water. Streambed temperature mapping successfully identified the location of groundwater entry to the Little Wind River, downgradient from the former Riverton uranium mill site, Wyoming, USA. Diffusive equilibrium in thin-film (DET) samplers further constrained the groundwater plume and established sediment pore water solute concentrations and patterns. In this system, evidence is presented for attenuation of uranium-rich groundwater in the shallow sediments where surface water and groundwater interaction occurs. Surface water grab and DET sampling successfully detected an increase in river uranium concentrations where the groundwater plume enters the Little Wind River; however, concentrations remained below environmental guideline levels. Uranium speciation was investigated using diffusive gradients in thin-film (DGT) samplers and geochemical speciation modelling. Together, these investigations indicate uranium may have limited bioavailability to organisms in the Little Wind River and, possibly, in other similar sites in the western U.S.A. This could be due to ion competition effects or the presence of non- or partially labile uranium complexes. Development of methods to establish the location of contaminated (uranium) groundwater entry to surface water environments, and the potential effects on ecosystems, is crucial to develop both site-specific and general conceptual models of uranium behavior and potential toxicity in affected ground and surface water environments.
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http://dx.doi.org/10.1016/j.scitotenv.2020.143314DOI Listing
March 2021

Uranium Bioaccumulation Dynamics in the Mayfly and Application to Site-Specific Prediction.

Environ Sci Technol 2020 09 1;54(18):11313-11321. Epub 2020 Sep 1.

U.S. Geological Survey, Menlo Park, California 94025, United States.

Little is known about the underlying mechanisms governing the bioaccumulation of uranium (U) in aquatic insects. We experimentally parameterized conditional rate constants for aqueous U uptake, dietary U uptake, and U elimination for the aquatic baetid mayfly . Results showed that this species accumulates U from both the surrounding water and diet, with waterborne uptake prevailing. Elevated dietary U concentrations decreased feeding rates, presumably by altering food palatability or impairing the mayfly's digestive processes, or both. Nearly 90% of the accumulated U was eliminated within 24 h after the waterborne exposure ceased, reflecting the desorption of weakly bound U from the insect's integument. To examine whether the experimentally derived rate constants for could be generalized to baetid mayflies, mayfly U concentrations were predicted using the water chemistry and U measured in periphyton from springs in Grand Canyon (United States) and were compared to U concentrations in spring-dwelling mayflies. Predicted and observed mayfly U concentrations were in good agreement. Under the modeled site-specific conditions, waterborne U uptake accounted for 52-93% of the bioaccumulated U. U accumulation was limited in these wild populations due to a combination of factors including low concentrations of bioavailable dissolved U species, slow U uptake rates from food, and fast U elimination.
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http://dx.doi.org/10.1021/acs.est.0c03372DOI Listing
September 2020

An interdisciplinary mixed-methods approach to developing antimicrobial stewardship interventions: Protocol for the Preserving Antibiotics through Safe Stewardship (PASS) Research Programme.

Wellcome Open Res 2020 14;5. Epub 2020 Jan 14.

University College London, London, UK.

Behaviour change is key to combating antimicrobial resistance. Antimicrobial stewardship (AMS) programmes promote and monitor judicious antibiotic use, but there is little consideration of behavioural and social influences when designing interventions.  We outline a programme of research which aims to co-design AMS interventions across healthcare settings, by integrating data-science, evidence- synthesis, behavioural-science and user-centred design. The project includes three work-packages (WP): Identifying patterns of prescribing):  analysis of electronic health-records to identify prescribing patterns in care-homes, primary-care, and secondary-care. An online survey will investigate consulting/antibiotic-seeking behaviours in members of the public. (Barriers and enablers to prescribing in practice): Semi-structured interviews and observations of practice to identify barriers/enablers to prescribing, influences on antibiotic-seeking behaviour and the social/contextual factors underpinning prescribing. Systematic reviews of AMS interventions to identify the components of existing interventions associated with effectiveness. Design workshops to identify constraints influencing the form of the intervention. Interviews conducted with healthcare-professionals in community pharmacies, care-homes, primary-, and secondary-care and with members of the public. Topic guides and analysis based on the Theoretical Domains Framework.  Observations conducted in care-homes, primary and secondary-care with analysis drawing on grounded theory.  Systematic reviews of interventions in each setting will be conducted, and interventions described using the Behaviour Change Technique taxonomy v1. Design workshops in care-homes, primary-, and secondary care. (Co-production of interventions and dissemination). Findings will be integrated to identify opportunities for interventions, and assess whether existing interventions target influences on antibiotic use. Stakeholder panels will be assembled to co-design and refine interventions in each setting, applying the Affordability, Practicability, Effectiveness, Acceptability, Side-effects and Equity (APEASE) criteria to prioritise candidate interventions.  Outputs will inform development of new AMS interventions and/or optimisation of existing interventions.  We will also develop web-resources for stakeholders providing analyses of antibiotic prescribing patterns, prescribing behaviours, and evidence reviews.
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http://dx.doi.org/10.12688/wellcomeopenres.15554.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7014923PMC
January 2020

Storytelling as a research tool and intervention around public health perceptions and behaviour: a protocol for a systematic narrative review.

BMJ Open 2019 12 3;9(12):e030597. Epub 2019 Dec 3.

Institute of Epidemiology and Health, University College London, London, UK.

Introduction: There is a growing trend to use storytelling as a research tool to extract information and/or as an intervention to effect change in the public knowledge, attitudes and behaviour (KAB) in relation to public health issues, primarily those with a strong element of disease prevention. However, evidence of its use in either or both capacities is limited. This protocol proposes a systematic narrative review of peer-reviewed, published literature on the use of storytelling as a research tool within the public health arena.

Methods And Analysis: Medline, EMBASE, PsycINFO, ERIC (Educational Resources Information Center), Web of Science, Art and Humanities database (ProQuest), Scopus and Google Scholar will be searched for studies that look at the use of storytelling in the research of pressing current public health issues, for example, vaccinations, antimicrobial resistance, climate change and cancer screening. The review will synthesise evidence of how storytelling is used as a research tool to (a) gain insights into KAB and (b) to effect change in KAB when used as an intervention. Included studies will be selected according to carefully defined criteria relevant to public health issues of interest, and data from qualitative, quantitative and mixed-methods studies will be extracted with a customised data extraction form. A narrative synthesis will be performed according to Economic and Social Research Council guidance from Popay, J, 2006.The study protocol follows the recommendations by the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P).

Ethics And Dissemination: Formal ethical approval is not required for this study, as no primary data will be collected. Dissemination will involve publishing results of this study in relevant peer-reviewed journal(s). Where possible, the study results will also be presented as posters or talks at relevant medical conferences and meetings.

Prospero Registration Number: CRD42019124704.
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http://dx.doi.org/10.1136/bmjopen-2019-030597DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6924770PMC
December 2019

Symptom reporting, healthcare-seeking behaviour and antibiotic use for common infections: protocol for Bug Watch, a prospective community cohort study.

BMJ Open 2019 05 22;9(5):e028676. Epub 2019 May 22.

Institute of Health Informatics, University College London, London, UK.

Introduction: Antimicrobial resistance is a significant worldwide problem largely driven by selective pressure exerted through antibiotic use. Preserving antibiotics requires identification of opportunities to safely reduce prescriptions, for example in the management of mild common infections in the community. However, more information is needed on how infections are usually managed and what proportion lead to consultation and antibiotic use. The aim of this study is to quantify consultation and prescribing patterns in the community for a range of common acute infection syndromes (respiratory, gastrointestinal, skin/soft tissue, mouth/dental, eye and urinary tract). This will inform development of interventions to improve antibiotic stewardship as part of a larger programme of work, Preserving Antibiotics through Safe Stewardship.

Methods And Analysis: This will be an online prospective community cohort study in England. We will invite 19 510 adults who previously took part in a nationally representative survey (the Health Survey for England) and consented to be contacted about future studies. Adults will also be asked to register their children. Data collection will consist of a baseline registration survey followed by weekly surveys sent by email for 6 months. Weekly surveys will collect information on symptoms of common infections, healthcare-seeking behaviour and use of treatments including antibiotics. We will calculate the proportions of infection syndromes that lead to General Practitioner consultation and antibiotic prescription. We will investigate how healthcare-seeking and treatment behaviours vary by demographics, social deprivation, infection profiles and knowledge and attitudes towards antibiotics, and will apply behavioural theory to investigate barriers and enablers to these behaviours.

Ethics And Dissemination: This study has been given ethical approval by the University College London Research Ethics Committee (ID 11813/001). Each participant will provide informed consent upon registration. We will disseminate our work through publication in peer-reviewed academic journals. Anonymised data will be made available through the UK Data Service (https://www.ukdataservice.ac.uk/).
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http://dx.doi.org/10.1136/bmjopen-2018-028676DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6537990PMC
May 2019

Assessing the Dietary Bioavailability of Metals Associated with Natural Particles: Extending the Use of the Reverse Labeling Approach to Zinc.

Environ Sci Technol 2017 03 22;51(5):2803-2810. Epub 2017 Feb 22.

U.S. Geological Survey, MS 496, 345 Middlefield Road Menlo Park, California 94025, United States.

We extend the use of a novel tracing technique to quantify the bioavailability of zinc (Zn) associated with natural particles using snails enriched with a less common Zn stable isotope. Lymnaea stagnalis is a model species that has relatively fast Zn uptake rates from the dissolved phase, enabling their rapid enrichment in Zn during the initial phase of labeling. Isotopically enriched snails were subsequently exposed to algae mixed with increasing amounts of metal-rich particles collected from two acid mine drainage impacted rivers. Zinc bioavailability from the natural particles was inferred from calculations of Zn assimilation into the snail's soft tissues. Zinc assimilation efficiency (AE) varied from 28% for the Animas River particles to 45% for the Snake River particles, indicating that particle-bound, or sorbed Zn, was bioavailable from acid mine drainage wastes. The relative binding strength of Zn sorption to the natural particles was inversely related to Zn bioavailability; a finding that would not have been possible without using the reverse labeling approach. Differences in the chemical composition of the particles suggest that their geochemical properties may influence the extent of Zn bioavailability.
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http://dx.doi.org/10.1021/acs.est.6b06253DOI Listing
March 2017

Sources and ages of fine-grained sediment to streams using fallout radionuclides in the Midwestern United States.

J Environ Manage 2017 Jun 24;194:73-85. Epub 2016 Aug 24.

U.S. Geological Survey, Texas Water Science Center, Austin, TX 78754 USA.

Fallout radionuclides, Be and Pb, sampled in bed sediment for 99 watersheds in the Midwestern region of the United States and in 15 samples of suspended sediment from 3 of these watersheds were used to partition upland from channel sources and to estimate the age or the time since the surface-derived portion of sediment was on the land surface (0-∼1 year). Channel sources dominate: 78 of the 99 bed material sites (79%) have >50% channel-derived sediment, and 9 of the 15 suspended-sediment samples (60%) have >50% channel-derived sediment. Be was detected in 82 bed sediment samples and all 15 suspended-sediment samples. The surface-derived portion of 54 of the 80 (68%) streams with detectable Be and Pb were ≤ 100 days old and the surface-derived portion of all suspended-sediment samples were ≤ 100 days old, indicating that surface-derived fine-grained sediment moves rapidly though these systems. The concentrations of two hydrophobic pesticides-DDE and bifenthrin-are correlated with the proportion of surface-derived sediment, indicating a link between geomorphic processes and particle-associated contaminants in streams. Urban areas had the highest pesticide concentrations and the largest percentage of surface-derived sediment. Although the percentage of surface-derived sediment is less than channel sources at most of the study sites, the relatively young age of the surface-derived sediment might indicate that management actions to reduce sediment contamination where the land surface is an important source could have noticeable effects.
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http://dx.doi.org/10.1016/j.jenvman.2016.06.018DOI Listing
June 2017

DNA Repair Profiling Reveals Nonrandom Outcomes at Cas9-Mediated Breaks.

Mol Cell 2016 08 4;63(4):633-646. Epub 2016 Aug 4.

Caribou Biosciences, Inc., Berkeley, CA 94710, USA. Electronic address:

The repair outcomes at site-specific DNA double-strand breaks (DSBs) generated by the RNA-guided DNA endonuclease Cas9 determine how gene function is altered. Despite the widespread adoption of CRISPR-Cas9 technology to induce DSBs for genome engineering, the resulting repair products have not been examined in depth. Here, the DNA repair profiles of 223 sites in the human genome demonstrate that the pattern of DNA repair following Cas9 cutting at each site is nonrandom and consistent across experimental replicates, cell lines, and reagent delivery methods. Furthermore, the repair outcomes are determined by the protospacer sequence rather than genomic context, indicating that DNA repair profiling in cell lines can be used to anticipate repair outcomes in primary cells. Chemical inhibition of DNA-PK enabled dissection of the DNA repair profiles into contributions from c-NHEJ and MMEJ. Finally, this work elucidates a strategy for using "error-prone" DNA-repair machinery to generate precise edits.
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http://dx.doi.org/10.1016/j.molcel.2016.06.037DOI Listing
August 2016

Biogeochemical Controls of Uranium Bioavailability from the Dissolved Phase in Natural Freshwaters.

Environ Sci Technol 2016 08 21;50(15):8120-7. Epub 2016 Jul 21.

U.S. Geological Survey , 3215 Marine St Suite E-127, Boulder, CO80303, United States.

To gain insights into the risks associated with uranium (U) mining and processing, we investigated the biogeochemical controls of U bioavailability in the model freshwater species Lymnaea stagnalis (Gastropoda). Bioavailability of dissolved U(VI) was characterized in controlled laboratory experiments over a range of water hardness, pH, and in the presence of complexing ligands in the form of dissolved natural organic matter (DOM). Results show that dissolved U is bioavailable under all the geochemical conditions tested. Uranium uptake rates follow first order kinetics over a range encompassing most environmental concentrations. Uranium uptake rates in L. stagnalis ultimately demonstrate saturation uptake kinetics when exposure concentrations exceed 100 nM, suggesting uptake via a finite number of carriers or ion channels. The lack of a relationship between U uptake rate constants and Ca uptake rates suggest that U does not exclusively use Ca membrane transporters. In general, U bioavailability decreases with increasing pH, increasing Ca and Mg concentrations, and when DOM is present. Competing ions did not affect U uptake rates. Speciation modeling that includes formation constants for U ternary complexes reveals that the aqueous concentration of dicarbonato U species (UO2(CO3)2(-2)) best predicts U bioavailability to L. stagnalis, challenging the free-ion activity model postulate.
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http://dx.doi.org/10.1021/acs.est.6b02406DOI Listing
August 2016

A millennial-scale record of Pb and Hg contamination in peatlands of the Sacramento-San Joaquin Delta of California, USA.

Sci Total Environ 2016 May 23;551-552:738-51. Epub 2016 Feb 23.

U.S. Geological Survey, 345 Middlefield Road, MS465, Menlo Park, CA 94025, United States. Electronic address:

In this paper, we provide the first record of millennial patterns of Pb and Hg concentrations on the west coast of the United States. Peat cores were collected from two micro-tidal marshes in the Sacramento-San Joaquin Delta of California. Core samples were analyzed for Pb, Hg, and Ti concentrations and dated using radiocarbon and (210)Pb. Pre-anthropogenic concentrations of Pb and Hg in peat ranged from 0.60 to 13.0μgg(-1)and from 6.9 to 71ngg(-1), respectively. For much of the past 6000+ years, the Delta was free from anthropogenic pollution, however, beginning in ~1425CE, Hg and Pb concentrations, Pb/Ti ratios, Pb enrichment factors (EFs), and HgEFs all increased. Pb isotope compositions of the peat suggest that this uptick was likely caused by smelting activities originating in Asia. The next increases in Pb and Hg contamination occurred during the California Gold Rush (beginning ~1850CE), when concentrations reached their highest levels (74μgg(-1) Pb, 990ngg(-1) Hg; PbEF=12 and HgEF=28). Lead concentrations increased again beginning in the ~1920s with the incorporation of Pb additives in gasoline. The phase-out of lead additives in the late 1980s was reflected in changes in Pb isotope ratios and reductions in Pb concentrations in the surface layers of the peat. The rise and subsequent fall of Hg contamination was also tracked by the peat archive, with the highest Hg concentrations occurring just before 1963CE and then decreasing during the post-1963 period. Overall, the results show that the Delta was a pristine region for most of its ~6700-year existence; however, since ~1425CE, it has received Pb and Hg contamination from both global and regional sources.
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http://dx.doi.org/10.1016/j.scitotenv.2016.01.201DOI Listing
May 2016

Bridging the gap between pragmatic intervention design and theory: using behavioural science tools to modify an existing quality improvement programme to implement "Sepsis Six".

Implement Sci 2016 Feb 3;11:14. Epub 2016 Feb 3.

University College London Medical School, Rowland Hill Street, London, UK.

Background: Sepsis has a mortality rate of 40 %, which can be halved if the evidence-based "Sepsis Six" care bundle is implemented within 1 h. UK audit shows low implementation rates. Interventions to improve this have had minimal effects. Quality improvement programmes could be further developed by using theoretical frameworks (Theoretical Domains Framework (TDF)) to modify existing interventions by identifying influences on clinical behaviour and selecting appropriate content. The aim of this study was to illustrate using this process to modify an intervention designed using plan-do-study-act (P-D-S-A) cycles that had achieved partial success in improving Sepsis Six implementation in one hospital.

Methods: Factors influencing implementation were investigated using the TDF to analyse interviews with 34 health professionals. The nursing team who developed and facilitated the intervention used the data to select modifications using the Behaviour Change Technique (BCT) Taxonomy (v1) and the APEASE criteria: affordability, practicability, effectiveness, acceptability, safety and equity.

Results: Five themes were identified as influencing implementation and guided intervention modification. These were:(1) "knowing what to do and why" (TDF domains knowledge, social/professional role and identity); (2) "risks and benefits" (beliefs about consequences), e.g. fear of harming patients through fluid overload acting as a barrier to implementation versus belief in the bundle's effectiveness acting as a lever to implementation; (3) "working together" (social influences, social/professional role and identity), e.g. team collaboration acting as a lever versus doctor/nurse conflict acting as a barrier; (4) "empowerment and support" (beliefs about capabilities, social/professional role and identity, behavioural regulation, social influences), e.g. involving staff in intervention development acting as a lever versus lack of confidence to challenge colleagues' decisions not to implement acting as a barrier; (5) "staffing levels" (environmental context and resources), e.g. shortages of doctors at night preventing implementation. The modified intervention included six new BCTs and consisted of two additional components (Sepsis Six training for the Hospital at Night Co-ordinator; a partnership agreement endorsing engagement of all clinical staff and permitting collegial challenge) and modifications to two existing components (staff education sessions; documents and materials).

Conclusions: This work demonstrates the feasibility of the TDF and BCT Taxonomy (v1) for developing an existing quality improvement intervention. The tools are compatible with the pragmatic P-D-S-A cycle approach generally used in quality improvement work.
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http://dx.doi.org/10.1186/s13012-016-0376-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4739425PMC
February 2016

Dietary Uptake of Cu Sorbed to Hydrous Iron Oxide is Linked to Cellular Toxicity and Feeding Inhibition in a Benthic Grazer.

Environ Sci Technol 2016 Feb 13;50(3):1552-60. Epub 2016 Jan 13.

University of North Carolina - Charlotte , Charlotte, North Carolina 28223, United States.

Whereas feeding inhibition caused by exposure to contaminants has been extensively documented, the underlying mechanism(s) are less well understood. For this study, the behavior of several key feeding processes, including ingestion rate and assimilation efficiency, that affect the dietary uptake of Cu were evaluated in the benthic grazer Lymnaea stagnalis following 4-5 h exposures to Cu adsorbed to synthetic hydrous ferric oxide (Cu-HFO). The particles were mixed with a cultured alga to create algal mats with Cu exposures spanning nearly 3 orders of magnitude at variable or constant Fe concentrations, thereby allowing first order and interactive effects of Cu and Fe to be evaluated. Results showed that Cu influx rates and ingestion rates decreased as Cu exposures of the algal mat mixture exceeded 10(4) nmol/g. Ingestion rate appeared to exert primary control on the Cu influx rate. Lysosomal destabilization rates increased directly with Cu influx rates. At the highest Cu exposure where the incidence of lysosomal membrane damage was greatest (51%), the ingestion rate was suppressed 80%. The findings suggested that feeding inhibition was a stress response emanating from excessive uptake of dietary Cu and cellular toxicity.
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http://dx.doi.org/10.1021/acs.est.5b04755DOI Listing
February 2016

National observational study to evaluate the "cleanyourhands" campaign (NOSEC): a questionnaire based study of national implementation.

Antimicrob Resist Infect Control 2015 23;4:52. Epub 2015 Nov 23.

University College London, Sheldon Stone, Royal Free Hospital, NW3 2PF. 0207 794 0500, London, UK.

Introduction: The number of national hand-hygiene campaigns has increased recently, following the World Health Organisation's (WHO) "Save Lives: clean your hands" initiative (2009), which offers hospitals a multi-component hand-hygiene intervention. The number of campaigns to be evaluated remains small. Most evaluations focus on consumption of alcohol hand rub (AHR). We are not aware of any evaluation reporting implementation of all campaign components. In a previously published report, we evaluated the effects of the English and Welsh cleanyourhands campaign (2004-8) on procurement of AHR and soap, and on selected healthcare associated infections. We now report on the implementation of each individual campaign component: provision of bedside AHR, ward posters, patient empowerment materials, audit and feedback, and guidance to secure institutional engagement.

Method:

Setting: all 189 acute National Health Service (NHS) hospitals in England and Wales (December 2005-June 2008). Six postal questionnaires (five voluntary, one mandatory) were distributed to infection control teams six-monthly from 6 to 36 months post roll-out. Selection and attrition bias were measured.

Results: Response rates fell from 134 (71 %) at 6 months to 82 (44 %) at 30 months, rising to 167 (90 %) for the final mandatory one (36 months). There was no evidence of attrition or selection bias. Hospitals reported widespread early implementation of bedside AHR and posters and a gradual rise in audit. At 36 months, 90 % of respondents reported the campaign to be a top hospital priority, with implementation of AHR, posters and audit reported by 96 %, 97 % and 91 % respectively. Patient empowerment was less successful.

Conclusions: The study suggests that all campaign components, apart from patient empowerment, were widely implemented and sustained. It supports previous work suggesting that adequate piloting, strong governmental support, refreshment of campaigns, and sufficient time to engage institutions help secure sustained implementation of a campaign's key components. The results should encourage countries wishing to launch coordinated national campaigns for hospitals to participate in the WHO's "Save Lives" initiative, which offers hospitals a similar multi-component intervention.
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http://dx.doi.org/10.1186/s13756-015-0077-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4655453PMC
November 2015

Characterising an implementation intervention in terms of behaviour change techniques and theory: the 'Sepsis Six' clinical care bundle.

Implement Sci 2015 Aug 8;10:111. Epub 2015 Aug 8.

Department of Clinical, Educational and Health Psychology, University College London, 1-19 Torrington Place, London, UK.

Background: Sepsis is a major cause of death from infection, with a mortality rate of 36 %. This can be halved by implementing the 'Sepsis Six' evidence-based care bundle within 1 h of presentation. A UK audit has shown that median implementation rates are 27-47 % and interventions to improve this have demonstrated minimal effects. In order to develop more effective implementation interventions, it is helpful to obtain detailed characterisations of current interventions and to draw on behavioural theory to identify mechanisms of change. The aim of this study was to illustrate this process by using the Behaviour Change Wheel; Behaviour Change Technique (BCT) Taxonomy; Capability, Opportunity, Motivation model of behaviour; and Theoretical Domains Framework to characterise the content and theoretical mechanisms of action of an existing intervention to implement Sepsis Six.

Methods: Data came from documentary, interview and observational analyses of intervention delivery in several wards of a UK hospital. A broad description of the intervention was created using the Template for Intervention Description and Replication framework. Content was specified in terms of (i) component BCTs using the BCT Taxonomy and (ii) intervention functions using the Behaviour Change Wheel. Mechanisms of action were specified using the Capability, Opportunity, Motivation model and the Theoretical Domains Framework.

Results: The intervention consisted of 19 BCTs, with eight identified using all three data sources. The BCTs were delivered via seven functions of the Behaviour Change Wheel, with four ('education', 'enablement', 'training' and 'environmental restructuring') supported by the three data sources. The most frequent mechanisms of action were reflective motivation (especially 'beliefs about consequences' and 'beliefs about capabilities') and psychological capability (especially 'knowledge').

Conclusions: The intervention consisted of a wide range of BCTs targeting a wide range of mechanisms of action. This study demonstrates the utility of the Behaviour Change Wheel, the BCT Taxonomy and the Theoretical Domains Framework, tools recognised for providing guidance for intervention design, for characterising an existing intervention to implement evidence-based care.
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http://dx.doi.org/10.1186/s13012-015-0300-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529730PMC
August 2015

Sedimentary organic biomarkers suggest detrimental effects of PAHs on estuarine microbial biomass during the 20th century in San Francisco Bay, CA, USA.

Chemosphere 2015 Jan 7;119:961-970. Epub 2014 Oct 7.

U.S. Geological Survey, Pacific Coastal and Marine Science Center, 400 Natural Bridges Drive, Santa Cruz, CA 95060, United States. Electronic address:

Hydrocarbon contaminants are ubiquitous in urban aquatic ecosystems, and the ability of some microbial strains to degrade certain polycyclic aromatic hydrocarbons (PAHs) is well established. However, detrimental effects of petroleum hydrocarbon contamination on nondegrader microbial populations and photosynthetic organisms have not often been considered. In the current study, fatty acid methyl ester (FAME) biomarkers in the sediment record were used to assess historical impacts of petroleum contamination on microbial and/or algal biomass in South San Francisco Bay, CA, USA. Profiles of saturated, branched, and monounsaturated fatty acids had similar concentrations and patterns downcore. Total PAHs in a sediment core were on average greater than 20× higher above ∼200 cm than below, which corresponds roughly to the year 1900. Isomer ratios were consistent with a predominant petroleum combustion source for PAHs. Several individual PAHs exceeded sediment quality screening values. Negative correlations between petroleum contaminants and microbial and algal biomarkers - along with high trans/cis ratios of unsaturated FA, and principle component analysis of the PAH and fatty acid records - suggest a negative impacts of petroleum contamination, appearing early in the 20th century, on microbial and/or algal ecology at the site.
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http://dx.doi.org/10.1016/j.chemosphere.2014.08.053DOI Listing
January 2015

Using psychological theory to understand the challenges facing staff delivering a ward-led intervention to increase hand hygiene behavior: a qualitative study.

Am J Infect Control 2014 May 20;42(5):495-9. Epub 2014 Mar 20.

Department of Psychology, University College London, London, UK.

Background: The Feedback Intervention Trial was a national trial of an intervention to increase hand hygiene behavior in English and Welsh hospitals. It significantly improved behavior, the effect increasing with fidelity to intervention, but the intervention proved more difficult to implement than anticipated. This study aimed to identify the barriers to and facilitators of implementation as experienced by those who delivered the intervention.

Methods: Semistructured interviews were conducted with 17 intervention ward coordinators implementing the intervention. Interview questions were based on the Theoretical Domains Framework. Text relating to each domain was scored according to whether it indicated low or high likelihood of implementation, and thematic analysis conducted.

Results: The lowest scoring domains were "environmental context and resources," "beliefs about capabilities," "social influences," and "emotion." Lack of time and understaffing, perceived negativity from other staff members, and stress were identified as challenges to implementation. The highest scoring domains were "behavioral regulation," "motivation," "skills," "knowledge," and "professional role." Ward coordinators reported that they had the skills, understanding, and motivation to implement the intervention and spoke of consistency of tasks with existing roles.

Conclusion: Implementation might be improved by giving designated time for intervention tasks and ensuring that the ward coordinator role is allocated to staff for whom tasks are commensurate with existing professional roles.
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http://dx.doi.org/10.1016/j.ajic.2013.12.022DOI Listing
May 2014

Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona.

Environ Sci Technol 2014 Feb 4;48(4):2165-72. Epub 2014 Feb 4.

United States Geological Survey , Menlo Park, California 94025, United States.

The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (μSXRF) mapping, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.
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http://dx.doi.org/10.1021/es402576fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991428PMC
February 2014

The national one week prevalence audit of universal meticillin-resistant Staphylococcus aureus (MRSA) admission screening 2012.

PLoS One 2013 12;8(9):e74219. Epub 2013 Sep 12.

University College London, London, United Kingdom.

Introduction: The English Department of Health introduced universal MRSA screening of admissions to English hospitals in 2010. It commissioned a national audit to review implementation, impact on patient management, admission prevalence and extra yield of MRSA identified compared to "high-risk" specialty or "checklist-activated" screening (CLAS) of patients with MRSA risk factors.

Methods: National audit May 2011. Questionnaires to infection control teams in all English NHS acute trusts, requesting number patients admitted and screened, new or previously known MRSA; MRSA point prevalence; screening and isolation policies; individual risk factors and patient management for all new MRSA patients and random sample of negatives.

Results: 144/167 (86.2%) trusts responded. Individual patient data for 760 new MRSA patients and 951 negatives. 61% of emergency admissions (median 67.3%), 81% (median 59.4%) electives and 47% (median 41.4%) day-cases were screened. MRSA admission prevalence: 1% (median 0.9%) emergencies, 0.6% (median 0.4%) electives, 0.4% (median 0%) day-cases. Approximately 50% all MRSA identified was new. Inpatient MRSA point prevalence: 3.3% (median 2.9%). 104 (77%) trusts pre-emptively isolated patients with previous MRSA, 63 (35%) pre-emptively isolated admissions to "high-risk" specialties; 7 (5%) used PCR routinely. Mean time to MRSA positive result: 2.87 days (±1.33); 37% (219/596) newly identified MRSA patients discharged before result available; 55% remainder (205/376) isolated post-result. In an average trust, CLAS would reduce screening by 50%, identifying 81% of all MRSA. "High risk" specialty screening would reduce screening by 89%, identifying 9% of MRSA.

Conclusions: Implementation of universal screening was poor. Admission prevalence (new cases) was low. CLAS reduced screening effort for minor decreases in identification, but implementation may prove difficult. Cost effectiveness of this and other policies, awaits evaluation by transmission dynamic economic modelling, using data from this audit. Until then trusts should seek to improve implementation of current policy and use of isolation facilities.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074219PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772122PMC
May 2014

Uranium(VI) interactions with mackinawite in the presence and absence of bicarbonate and oxygen.

Environ Sci Technol 2013 Jul 21;47(13):7357-64. Epub 2013 Jun 21.

U.S. Geological Survey, Box 25046, MS 973, Denver Federal Center, Denver, Colorado 80225-0046, United States.

Mackinawite, Fe(II)S, samples loaded with uranium (10(-5), 10(-4), and 10(-3) mol U/g FeS) at pH 5, 7, and 9, were characterized using X-ray absorption spectroscopy and X-ray diffraction to determine the effects of pH, bicarbonate, and oxidation on uptake. Under anoxic conditions, a 5 g/L suspension of mackinawite lowered 5 × 10(-5) M uranium(VI) to below 30 ppb (1.26 × 10(-7) M) U. Between 82 and 88% of the uranium removed from solution by mackinawite was U(IV) and was nearly completely reduced to U(IV) when 0.012 M bicarbonate was added. Near-neighbor coordination consisting of uranium-oxygen and uranium-uranium distances indicates the formation of uraninite in the presence and absence of bicarbonate, suggesting reductive precipitation as the dominant removal mechanism. Following equilibration in air, mackinawite was oxidized to mainly goethite and sulfur and about 76% of U(IV) was reoxidized to U(VI) with coordination of uranium to axial and equatorial oxygen, similar to uranyl. Additionally, uranium-iron distances, typical of coprecipitation of uranium with iron oxides, and uranium-sulfur distances indicating bidentate coordination of U(VI) to sulfate were evident. The affinity of mackinawite and its oxidation products for U(VI) provides impetus for further study of mackinawite as a potential reactive medium for remediation of uranium-contaminated water.
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http://dx.doi.org/10.1021/es400450zDOI Listing
July 2013

Estimating sub-surface dispersed oil concentration using acoustic backscatter response.

Mar Pollut Bull 2013 May 13;70(1-2):140-6. Epub 2013 Mar 13.

Civil and Environmental Engineering, Clarkson University, 8 Clarkson Ave., Potsdam, NY 13699, USA.

The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles.
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http://dx.doi.org/10.1016/j.marpolbul.2013.02.025DOI Listing
May 2013

Novel and nontraditional use of stable isotope tracers to study metal bioavailability from natural particles.

Environ Sci Technol 2013 Apr 18;47(7):3424-31. Epub 2013 Mar 18.

US Geological Survey, MS 496, 345 Middlefield Road, Menlo Park, California 94025, United States.

We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails ( Lymnaea stagnalis ) to synthetic water spiked with Cu that was 99.4% (65)Cu to increase the relative abundance of (65)Cu in the snail's tissues from ~32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing Fe-Al particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used (63)Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes.
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http://dx.doi.org/10.1021/es400162fDOI Listing
April 2013

Dietary bioavailability of Cu adsorbed to colloidal hydrous ferric oxide.

Environ Sci Technol 2013 Mar 26;47(6):2869-76. Epub 2013 Feb 26.

U.S. Geological Survey, Menlo Park, California, USA.

The dietary bioavailability of copper (Cu) adsorbed to synthetic colloidal hydrous ferric oxide (HFO) was evaluated from the assimilation of (65)Cu by two benthic grazers, a gastropod and a larval mayfly. HFO was synthesized, labeled with (65)Cu to achieve a Cu/Fe ratio comparable to that determined in naturally formed HFO, and then aged. The labeled colloids were mixed with a food source (the diatom Nitzschia palea) to yield dietary (65)Cu concentrations ranging from 211 to 2204 nmol/g (dry weight). Animals were pulse fed the contaminated diet and assimilation of (65)Cu from HFO was determined following 1-3 days of depuration. Mass transfer of (65)Cu from HFO to the diatom was less than 1%, indicating that HFO was the source of (65)Cu to the grazers. Estimates of assimilation efficiency indicated that the majority of Cu ingested as HFO was assimilated (values >70%), implying that colloidal HFO potentially represents a source of dietary Cu to benthic grazers, especially where there is active formation and infiltration of these particles into benthic substrates.
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http://dx.doi.org/10.1021/es3044856DOI Listing
March 2013
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