51 research outputs found
A Burning Issue: Assessing the impact of alternative grouse moor managements on vegetation dynamics and carbon cycling on UK blanket bogs
Blanket bogs are a globally rare habitat and store vast quantities of carbon in the form of peat. In the UK, blanket bogs are subject to a variety of anthropogenic activities which threaten their ability to maintain this carbon store long term. Release of this carbon is likely to exacerbate climate change. Burning peatlands to encourage Calluna vulgaris on grouse moors is thought to be detrimental to peat-forming vegetation, water quality and the peatland carbon balance but lacks robust evidence. This study aimed to assess the effects of different methods of Calluna management on the carbon balance, vegetation dynamics and water quality of blanket bogs.
A paired catchment manipulation was combined with plot-scale manipulations and replicated across three English blanket bogs managed as grouse moors to examine the effects of burning, mowing, no management and variations thereof on the carbon balance and vegetation changes.
Carbon balances indicated that unmanaged areas were a carbon sink whereas both burning and mowing caused carbon release. Taking the quantities of burnt plant biomass and tractor fuel into account, burnt areas were a stronger carbon source than mown areas. Mowing increased both height and cover of Calluna compared to burning, promoted growth of Eriophorum vaginatum, a peat-forming species, and had less bare ground. The nutritional content of Calluna increased under management, being slightly higher following burning than mowing.
A pot experiment was combined with radiocarbon analysis to explore whether Calluna-associated ericoid fungi break down recalcitrant matter in the peat. The radiocarbon dates strongly indicated that ericoid fungi decomposed recalcitrant ancient compounds within the peat, releasing these as gaseous and aquatic carbon.
Altering Calluna management practices by replacing burning with mowing, where feasible, could potentially bring benefits for the peatland carbon balance and water quality by increasing abundance of peat-forming species without negatively impacting upon grouse
Bog Breathing: The extent of peat shrinkage and expansion on blanket bogs in relation to water table, heather management and dominant vegetation and its implications for carbon stock assessments
Peatlands represent a globally important carbon stock. Peat soil carbon stock assessments rely on measurements of carbon concentration, bulk density and soil depth. However, peat surface levels - and thus soil depths - change (âbog breathingâ) largely as a response to peat shrinkage and expansion in relation to water table changes. This study assessed the magnitude of and potential for this mechanism to influence carbon stock calculations under field and laboratory conditions. In the UK, most peatlands are upland blanket bogs, of which a large proportion are managed as âgrouse moorsâ. This currently involves rotational burning, although alternative management is increasingly considered. Peat depth and water tables were investigated on three grouse moors on blanket bog in northern England, comparing changes under different heather management interventions (burning, mowing and uncut). One site also allowed investigation of changes in relation to slope and under the three major bog vegetation types (ling heather, cottongrass and Sphagnum moss), which were compared to observed changes in peat cores under controlled laboratory conditions simulating periods of drought and rewetting. Changes in depth and bulk density were recorded and the potential implications for carbon stock estimates were calculated. Results highlight site specific relationships as potential habitat condition indicators and demonstrate that previously reported surface peat carbon losses resulting from enhanced decomposition under rising temperatures might also be explained by apparent changes due to peat shrinkage and expansion. It is recommended to accurately record bulk density and total peat depth measurements as part of peat carbon stock assessments
Comparison of particulate trace element concentrations in the North Atlantic Ocean as determined with discrete bottle sampling and in situ pumping
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 116 (2015): 272-282, doi:10.1016/j.dsr2.2014.11.005.The oceanic geochemical cycles of many metals are controlled, at least in part, by interactions with particulate matter, and measurements of particulate trace metals are a core component of the international GEOTRACES program. Particles can be collected by several methods, including in-line filtration from sample bottles and in situ pumping. Both approaches were used to collect particles from the water column on the U.S. GEOTRACES North Atlantic Zonal Transect cruises. Statistical comparison of 91 paired samples collected at matching stations and depths indicate mean concentrations within 5% for Fe and Ti, within 10% for Cd, Mn and Co, and within 15% for Al. Particulate concentrations were higher in bottle samples for Cd, Mn and Co but lower in bottle samples for Fe, Al and Ti, suggesting that large lithogenic particles may be undersampled by bottles in near-shelf environments. In contrast, P was 58% higher on average in bottle samples. This is likely due to a combination of analytical offsets between lab groups, differences in filter pore size, and potential loss of labile P from pump samples following misting with deionized water. Comparable depth profiles were produced by the methods across a range of conditions in the North Atlantic.This work was funded by grants from the US National Science Foundation to BST (OCE-0928289) and PJL (OCE-0963026) as part of the US GEOTRACES North Atlantic Zonal Transect program
Approaches to herbicide (MCPA) pollution mitigation in drinking water source catchments using enhanced space and time monitoring
Publication history: Accepted - 30 September 2020; Published online - 8 October 2020Freshwater occurrences of the selective acid herbicide 2-methyl-4-chloro-phenoxyacetic acid (MCPA) are an ongoing regulatory and financial issue for water utility industries as the number and magnitude of detections increase, particularly in surface water catchments. Assessments for mitigating pesticide pollution in catchments used as drinking water sources require a combination of catchment-based and water treatment solutions, but approaches are limited by a lack of empirical data. In this study, an enhanced spatial (11 locations) and temporal (7-hourly to daily sampling) monitoring approach was employed to address these issues in an exemplar surface water source catchment (384 km2). The spatial sampling revealed that MCPA was widespread, with occurrences above the 0.1 ÎŒg Lâ1 threshold for a single pesticide being highly positively correlated to sub-catchments with higher proportions of âImproved Grasslandâ land use (r = 0.84). These data provide a strong foundation for targeting catchment-based mitigation solutions and also add to the debate on the ecosystems services provided by such catchments. Additionally, of the 999 temporal samples taken over 12 months from the catchment outlet, 25% were above the drinking water threshold of 0.1 ÎŒg Lâ1. This prevalence of high concentrations presents costly problems for source water treatment. Using these data, abstraction shutdowns were simulated for five scenarios using hydrometeorological data to explore the potential to avoid intake of high MCPA concentrations. The scenarios stopped abstraction for 4.2â9.3% of the AprilâOctober period and reduced intake of water containing over 0.1 ÎŒg Lâ1 of MCPA by 16â31%. This represents an important development for real-time proxy assessments for water abstraction in the absence of more direct pesticide monitoring data.This work was funded by the Source to Tap project (project reference IVA5018 â www.sourcetotap.eu). The Source to Tap project is supported by the European Union's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB)
Evaluation of ChemcatcherÂź passive samplers for pesticide monitoring using high-frequency catchment scale data
Publication history: Accepted - 13 September 2022; Published online - 30 September 2022Passive samplers (PS) have been proposed as an enhanced water quality monitoring solution in rivers, but their performance against high-frequency data over the longer term has not been widely explored. This study compared the performance of ChemcatcherÂź passive sampling (PS) devices with high-frequency sampling (HFS: 7-hourly to daily) in two dynamic rivers over 16 months. The evaluation was based on the acid herbicides MCPA (2-methyl-4-chlorophenoxyacetic acid), mecoprop-P, fluroxypyr and triclopyr. The impact of river discharge parameters on ChemcatcherÂź device performance was also explored. Mixed effects modelling showed that time-weighted mean concentration (TWMC) and flow-weighted mean concentration (FWMC) values obtained by the HFS approach were both significantly higher (p 0.05). There was little indication that river flow parameters altered PS performanceâsome minor effects were not significant or consistent. Despite this, the PS recovery of very low concentrations indicated that ChemcatcherÂź devices may be used to evaluate the presence/absence and magnitude of acid herbicides in hydrologically dynamic rivers in synoptic type surveys where space and time coverage is required. However, a period of calibration of the devices in each river would be necessary if they were intended to provide a quantitative review of pesticide concentration as compared with HFS approaches.This work was funded in part by the Source to Tap project (project
reference IVA5018 â http://www.sourcetotap.eu), supported by the
European Unionâs INTERREG VA Programme which is managed by the
Special EU Programmes Body (SEUPB). The work was also part-funded
by the FAIRWAY project (project reference 727984 - http://www.fair
way-project.eu/). supported by the European Unionâs HORIZON 2020
Programme
Application of metal oxide semiconductor for detection of ammonia emissions from agricultural sources
Publication history: Accepted - 17 November 2022; Published online - 21 November 2022.Agricultural emissions of ammonia (NH3) reduce air quality and biodiversity. Measuring the effectiveness of
mitigations measures requires rapid monitoring tools, however, conventional methods are labour intensive and
costly. This study evaluated the performance of a prototype metal oxide semiconductor (MOS) gas sensor for
monitoring NH3. Conventional methods were used to calibrate sensor conductance. The metal oxide semiconductor
(MOS) gas sensor was calibrated against NH3 released from a 0.1 M phosphate buffer spiked with
ammonium chloride and NH3 released from recently spread cattle slurry. Field measurements using the MOS
sensor were compared with values measuring a Bruker Open Path Air Monitoring System. Sensor conductance
and NH3 concentration were described using single site Langmuir adsorption model. Field calibrations suggest a
higher detection limit above 0.1 ppm and coefficients of determination were 0.93 and 0.89 for sensors 1 and 2,
respectively. For prototypes deployed under field conditions, sensitivities of 2.2 and 2.4 with nonlinearity
constants of 0.53 and 0.51, were found for sensor 1 and 3 respectively. Average R2 values were 0.88 for sensor 1
and 0.92 for sensor 3. The calibrations were used to calculate NH3 concentrations from slurry emissions using
MOS sensor conductance. NH3 concentrations between 0.2 and 1 ppm, were measured with standard deviation
of 20% of verified concentrations. The MOS sensor is sensitive enough to detect NH3 emission from agricultural
sources with concentrations above 0.2 ppm. Low power and cost of MOS sensors are an advantage over existing
techniques.This work was supported by the European Unionâs Horizon 2020 Research and Innovation Programme [grant agreement No. 825325]
Reducing MCPA herbicide pollution at catchment scale using an agri-environmental scheme
Publication history: Accepted - 16 May 2022; Published online - 20 May 2022.In river catchments used as drinking water sources, high pesticide concentrations in abstracted waters require an expensive
treatment step prior to supply. The acid herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) is particularly
problematic as it is highly mobile in the soil-water environment following application. Here, an agri-environmental
scheme (AES) was introduced to a large-scale catchment (384 km2) to potentially reduce the burden of pesticides in
the water treatment process. The main measure offered was contractor application of glyphosate by weed wiping as
a substitute for boom spraying of MCPA, supported by educational and advisory activities. A combined innovation applied
in the assessment was, i) a full before-after-control-impact (BACI) framework over four peak application seasons
(April to October 2018 to 2021) where a neighbouring catchment (386 km2) did not have an AES and, ii) an enhanced
monitoring approach where river discharge and MCPA concentrations were measured synchronously in each catchment.
During peak application periods the sample resolution was every 7 h, and daily during quiescent winter periods.
This sampling approach enabled flow- and time-weighted concentrations to be established, and a detailed record of
export loads. These loads were up to 0.242 kg kmâ2 yrâ1, and over an order of magnitude higher than previously reported
in the literature. Despite this, and accounting for inter-annual and seasonal variations in river discharges, the
AES catchment indicated a reduction in both flow- and time-weighted MCPA concentration of up to 21% and 24%, respectively,
compared to the control catchment. No pollution swapping was detected. Nevertheless, the percentage of
MCPA occurrences above a 0.1 ÎŒg Lâ1 threshold did not reduce and so the need for treatment was not fully resolved.
Although the work highlights the advantages of catchment management approaches for pollution reduction in source
water catchments, it also indicates that maximising participation will be essential for future AES.This work was carried out as part of Source to Tap (IVA5018), a project supported by the European Union's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB)
Evaluation of ChemcatcherÂź passive samplers for pesticide monitoring using high-frequency catchment scale data
Publication history: Accepted - 13 September 2022; Published online - 30 September 2022Passive samplers (PS) have been proposed as an enhanced water quality monitoring solution in rivers, but their performance against high-frequency data over the longer term has not been widely explored. This study compared the performance of ChemcatcherÂź passive sampling (PS) devices with high-frequency sampling (HFS: 7-hourly to daily) in two dynamic rivers over 16 months. The evaluation was based on the acid herbicides MCPA (2-methyl-4-chlorophenoxyacetic acid), mecoprop-P, fluroxypyr and triclopyr. The impact of river discharge parameters on ChemcatcherÂź device performance was also explored. Mixed effects modelling showed that time-weighted mean concentration (TWMC) and flow-weighted mean concentration (FWMC) values obtained by the HFS approach were both significantly higher (p 0.05). There was little indication that river flow parameters altered PS performanceâsome minor effects were not significant or consistent. Despite this, the PS recovery of very low concentrations indicated that ChemcatcherÂź devices may be used to evaluate the presence/absence and magnitude of acid herbicides in hydrologically dynamic rivers in synoptic type surveys where space and time coverage is required. However, a period of calibration of the devices in each river would be necessary if they were intended to provide a quantitative review of pesticide concentration as compared with HFS approaches.This work was funded in part by the Source to Tap project (project
reference IVA5018 â http://www.sourcetotap.eu), supported by the
European Unionâs INTERREG VA Programme which is managed by the
Special EU Programmes Body (SEUPB). The work was also part-funded
by the FAIRWAY project (project reference 727984 - http://www.fair
way-project.eu/). supported by the European Unionâs HORIZON 2020
Programme
Quantifying MCPA load pathways at catchment scale using high temporal resolution data
peer-reviewedDetection of the agricultural acid herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) in drinking water source catchments is of growing concern, with economic and environmental implications for water utilities and wider ecosystem services. MCPA is poorly adsorbed to soil and highly mobile in water, but hydrological pathway processes are relatively unknown at the catchment scale and limited by coarse resolution data. This understanding is required to target mitigation measures and to provide a framework to monitor their effectiveness. To address this knowledge gap, this study reports findings from river discharge and synchronous MCPA concentration datasets (continuous 7 hour and with additional hourly sampling during storm events) collected over a 7 month herbicide spraying season. The study was undertaken in a surface (source) water catchment (384 km2âof which 154 km2 is agricultural land use) in the cross-border area of Ireland. Combined into loads, and using two pathway separation techniques, the MCPA data were apportioned into event and baseload components and the former was further separated to quantify a quickflow (QF) and other event pathways. Based on the 7 hourly dataset, 85.2 kg (0.22 kg kmâ2 by catchment area, or 0.55 kg kmâ2 by agricultural area) of MCPA was exported from the catchment in 7 months. Of this load, 87.7 % was transported via event flow pathways with 72.0 % transported via surface dominated (QF) pathways. Approximately 12 % of the MCPA load was transported via deep baseflows, indicating a persistence in this delayed pathway, and this was the primary pathway condition monitored in a weekly regulatory sampling programme. However, overall, the data indicated a dominant acute, storm dependent process of incidental MCPA loss during the spraying season. Reducing use and/or implementing extensive surface pathway disconnection measures are the mitigation options with greatest potential, the success of which can only be assessed using high temporal resolution monitoring techniques
Practical considerations for a TB controlled human infection model (TB-CHIM); the case for TB-CHIM in Africa, a systematic review of the literature and report of 2 workshop discussions in UK and Malawi
Background: Tuberculosis (TB) remains a major challenge in many domains including diagnosis, pathogenesis, prevention, treatment, drug resistance and long-term protection of the public health by vaccination. A controlled human infection model (CHIM) could potentially facilitate breakthroughs in each of these domains but has so far been considered impossible owing to technical and safety concerns.
Methods: A systematic review of mycobacterial human challenge studies was carried out to evaluate progress to date, best possible ways forward and challenges to be overcome. We searched MEDLINE (1946 to current) and CINAHL (1984 to current) databases; and Google Scholar to search citations in selected manuscripts. The final search was conducted 3rd February 2022. Inclusion criteria: adults â„18 years old; administration of live mycobacteria; and interventional trials or cohort studies with immune and/or microbiological endpoints. Exclusion criteria: animal studies; studies with no primary data; no administration of live mycobacteria; retrospective cohort studies; case-series; and case-reports. Relevant tools (Cochrane Collaboration for RCTs and Newcastle-Ottawa Scale for non-randomised studies) were used to assess risk of bias and present a narrative synthesis of our findings.
Results: The search identified 1,388 titles for review; of these 90 were reviewed for inclusion; and 27 were included. Of these, 15 were randomised controlled trials and 12 were prospective cohort studies. We focussed on administration route, challenge agent and dose administered for data extraction. Overall, BCG studies including fluorescent BCG show the most immediate utility, and genetically modified Mycobacteria tuberculosis is the most tantalising prospect of discovery breakthrough.
Conclusions: The TB-CHIM development group met in 2019 and 2022 to consider the results of the systematic review, to hear presentations from many of the senior authors whose work had been reviewed and to consider best ways forward. This paper reports both the systematic review and the deliberations
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