740 research outputs found
Contaminant mobility as a result of sediment inundation : literature review and laboratory scale pilot study on mining contaminated sediments
This report presents a literature review of soil and sediment inundation methodologies and
describes a pilot scale laboratory inundation study.
Changing weather conditions, subsequent flooding events, and the increased frequency of such
events both in the UK and worldwide is highlighting the need to research the area of contaminant
mobility from soils and sediments under inundated conditions. The findings of such
investigations impact on a wide variety of sectors, including human and ecological health,
agriculture, building, transport, world economy and climate change.
Standardised methodologies for the investigation of contaminant mobility resulting from
soil/sediment inundation episodes are not available. Most research has been conducted in the
agricultural sector for nutrient transport, as part of soil fertility and plant nutrition studies. Only
recently has work been undertaken for studying potentially harmful element transport in
inundated sediments/soils.
A pilot scale laboratory study was undertaken using contaminated bank sediment samples
collected from the Rookhope Burn catchment, Northern England, UK, with the aim to examine
the extent of contaminant mobilisation from flooded sediments. The catchment has been
affected by historical mining and processing of lead and zinc ore and is representative of several
catchments affected by the environmental legacy related to mining in the Northern Pennine
Orefield.
Bank sediment Pb and Zn concentrations were found significantly above both the TEL and PEL
sediment quality criteria, posing potentially a significant hazard to aquatic organisms. The source
of the Pb and Zn in the sediments is related to the underlying mineralisation, mining activities
and mine water discharges in the catchment. Abundances of original sulphide ore and authigenic
metal-bearing phases were expected to vary through the catchment.
The study design simulated rising flood water, a slow saturation of the sediment in order to
induce a slow change in physico-chemical properties, followed by a 3 month (88 day) stagnation
period. Natural day-night cycles were simulated by undertaking the study on the bench top
during the winter of 2009/2010 (November to February). The chemical changes in the
inundation water during the experiment were monitored and the sediment pore water at the end
of the inundation period analysed. The inundation water pH remained alkaline to neutral, while
redox measurements indicated oxic conditions in the water column throughout the inundation
period.
The pilot study showed that inundation of river bank sediments from the Rookhope Burn may be
a significant pathway for contaminants in the catchment and that mobilisation from the
sediments may pose a hazard to environmental receptors in the area, particularly with respect to
Pb and Zn contamination. The different degrees and different rates of metal losses to the
overlying water column observed during the flooding of the Rookhope Burn bank sediments
demonstrated that the significance of metal mobilisation was dictated by the sediment
composition.
The inundation water composition monitored during the sediment flooding was used to indirectly
infer possible processes that control contaminant fluxes from the sediments to the overlying
water. Dissolved Pb concentration in the inundation water reflected the original concentration in
the solid material and in sediments that had XRD-detectable galena and cerussite the dissolved
Pb concentration reached a maximum value of 395 Ī¼g l-1. Cerussite, which is commonly formed
as coatings on galena during the sulphide weathering, was close or supersaturated in those
solutions, suggesting that the lead carbonate mineral phase provided a continuous source of Pb to
these solutions.
The initial dissolved Zn in the inundation waters was independent of the original concentration
in the sediments. Sediments downstream a mine water discharge showed a greater availability of
easily mobilised Zn, producing high initial Zn concentration in the inundation water, despite the
relatively low Zn concentration in the inundated sediment. The Zn/SO4 and Cd/Zn molar ratios
were both consistent with sphalerite mineral oxidation. The final inundation water solutions had
the highest Zn concentrations for those sediment samples where sphalerite was detected by
XRD.
Redox sensitive elements such as Fe and Mn could not unequivocally indicate the presence of
reducing conditions within the flooded sediments and the redox measurements were carried out
only in the overlying water column (ORP above 200-350 mV). Low organic matter content and
sandy texture would not have favoured the rapid formation of an anoxic layer. Yet, only
extending the ORP measurements to the submerged sediment would determine the presence of
flooding-induced reducing conditions. Reductive dissolution of Mn oxyhydroxides would result
in release of Mn into solution, along with other trace metals, such as Pb and Zn. Mn increased in
the inundation water throughout most or all the inundation period for some of the studied
sediments. Their final pore water composition was significantly enriched in Mn (1300-
6500 Ī¼g l-1). Saturation indices indicated both rhodocrosite (MnCO3) and Mn oxides reached
saturation. Therefore, it was not possible to preclude either the role of rhodocrosite as solubility
controlling solid phase or the reductive dissolution of Mn oxides for accounting the enhanced
Mn concentrations in the pore water and overlying water column without a better
characterisation of the solid phase and monitoring of the sediment redox conditions.
Amendments to the inundation test design have been recommended, which comprise:
set-up to allow for the continuous monitoring of pore water dynamics and allow for the
collection of pore water at the different times and measurement of pore water pH and Eh;
inclusion of a blank test cell, to test the influence of the properties and the volume of the
inundation water;
inclusion of flow-cell tests to assess the influence of moving or stagnant inundation
water;
the inclusion of abiotic blanks to identify the role microbes play in the solubilisation of
contaminants.
complementary characterisation of the solid phase material and metal distribution in the
sediment before and after the inundation experiment
Double Ionisation in R-Matrix Theory Using a 2-electron Outer Region
We have developed a two-electron outer region for use within R-matrix theory
to describe double ionisation processes. The capability of this method is
demonstrated for single-photon double ionisation of He in the photon energy
region between 80 eV to 180 eV. The cross sections are in agreement with
established data. The extended RMT method also provides information on
higher-order processes, as demonstrated by the identification of signatures for
sequential double ionisation processes involving an intermediate He state
with .Comment: 5 pages, 4 figure
Anthropogenic and geogenic impacts on arsenic bioaccessibility in UK topsoils
Predictive linear regression (LR) modelling between bioaccessible arsenic (B-As) and a range of total elemental
compositions and soil properties was executed in order to assess the potential for developing a national
B-As dataset for the UK. LR indicates that total arsenic (As) is the only highly significant independent variable
for estimating B-As in urban areas where it explains 75ā92% of the variance. The broad compatibility of the
London, Glasgow and Swansea regression models suggests that application of these models to estimate
bioaccessible As in UK soils impacted by diffuse anthropogenic urban contamination and non-ferrous metal
processing should be relatively accurate. In areas dominated by Jurassic ironstones and associated clays
and limestones, total As, P and pH are significant, accounting for 53, 14 and 5%, respectively, of the B-As
variance. Models based on total As as the sole predictor in the combined Jurassic and Cretaceous sedimentary
ironstones datasets explain about 40% of the B-As variance. The median As bioaccessible fraction (%As-BAF) is
19 to 28% in the anthropogenic contamination impacted urban domains, but much lower (5ā9%) in geogenic
terrains dominated by ironstones. Results of this study can be used as part of a lines of evidence approach to
localised risk assessment but should not be used to replace bioaccessibility testing at individual sites where
local conditions may vary considerably from the broad overview presented in this study
Agent based modelling : initial assessment for use on soil bioaccessibility
This report describes the testing of Agent Based Modelling implementations in three different software packages: Repast-simphony, NetLogo and Insight-maker. These software have been evaluated against their capability to simulate the exposure of people as agents moving across Arsenic contaminated soils. Two of the three tested software (Repast-simphony and NetLogo) are recommended for assessment on more complex problems. An outline work plan is presented for future work
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Comparison of on-line and off-line methods to quantify reactive oxygen species (ROS) in atmospheric aerosols
Atmospheric aerosol particle concentrations have been linked with a wide range of pulmonary and cardio-vascular diseases but the particle properties responsible for these negative health effects are largely unknown. It is often speculated that reactive oxygen species (ROS) present in atmospheric particles lead to oxidative stress in, and ultimately disease of, the human lung. The quantification of ROS is highly challenging because some ROS components such as radicals are highly reactive and therefore short-lived. Thus, fast analysis methods are likely advantageous over methods with a long delay between aerosol sampling and ROS analysis. We present for the first time a detailed comparison of conventional off-line and fast on-line methods to quantify ROS in organic aerosols. For this comparison a new and fast on-line instrument was built and characterized to quantify ROS in aerosol particles with high sensitivity and a limit of detection of 4 nmol H2O2 equivalents per m3 air. ROS concentrations are measured with a time resolution of approximately 15 min, which allows the tracking of fast changing atmospheric conditions. The comparison of the off-line and on-line method shows that, in oxidized organic model aerosol particles, the majority of ROS have a very short lifetime of a few minutes whereas a small fraction is stable for a day or longer. This indicates that off-line techniques, where there is often a delay of hours to days between particle collection and ROS analysis, may severely underestimate true ROS concentrations and that fast on-line techniques are necessary for a reliable ROS quantification in atmospheric aerosol particles and a meaningful correlation with health outcomes.This work was supported by the Natural Environment Research Council (NE/H52449X/1), the Velux Stiftung (Project 593) and an ERC starting grant (grant no. 279405).This is the accepted manuscript version. The final published version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S1352231014002787
Heavy metal bioavailability and bioaccessibility in soil
This chapter considers the use of a variety of approaches to assess either the bioavailability or the bioaccessibility of metals in soil. The bioavailability of metals from soils is considered with respect to a series of single-extraction methods, including the use of ethylenediaminetetraacetic acid (EDTA), acetic acid, diethylenetriaminepentaacetic acid (DTPA), ammonium nitrate, calcium chloride and sodium nitrate. Then, a procedure for the recovery of metals using a three-stage sequential extraction protocol is described. Two alternate approaches for assessing the environmental health risk to humans by undertaking in vitro gastrointestinal extraction (also known as the physiologically based extraction test, PBET) are considered. Finally, two acid digestion protocols that allow the pseudo-total metal content of samples to be assessed are provided. In all cases details of how the different approaches can be performed are provided, including the specific reagents required (and their preparation), details of the different extraction and acid digestion protocols to be followed and suitable analytical details to allow the measurement of metals by inductively coupled plasma mass spectrometry (ICP-MS) with/without a collision/reaction cell. A detailed Notes section provides experimental details to guide the reader through some of the practical aspects of the procedures. Finally, some experimental results are provided as evidence of the suitability of the approaches described including single-extraction data, using EDTA and acetic acid, for metals in CRM BCR 700. In addition, in vitro gastrointestinal extraction data are provided for metals in CRM SRM 1570A (spinach leaves). The influence of time on the intestinal fluid phase on the recovery of metals in CRM SRM 1570A (spinach leaves) and CRM INCT-TL-1 (tea leaves) is investigated, as well as the repeatability in terms of recovery of metals from soil over a 3-week period by in vitro gastrointestinal extraction
Sources, mobility and bioaccessibility of potentially harmful elements in UK soils
Potentially harmful elements (PHE) occur both naturally from geogenic sources and from anthropogenic derived pollution. Anthropogenic sources can be further categorised into those derived from point sources. A point source is a single identifiable source which is confined to a very small area such as that arising from disposal of waste material or from an industrial plant. Diffuse pollution arises where substances are widely used and dispersed over an area as a result of land use activities, often associated with urban development. Examples of diffuse pollution include atmospheric deposition of contaminants arising from industry, domestic coal fires and traffic exhaust, and disposal of domestic coal ash. The total concentration and the chemical form and hence the mobility of the PHE in a soil is highly dependent on the source
Small-scale skeletal muscle constructs for in-vitro musculoskeletal junction preclinical testbed [Abstract]
Small-scale skeletal muscle constructs for in-vitro musculoskeletal junction preclinical testbed [Abstract
Preclinical musculoskeletal junction testbed: Optimisation of a reproducible skeletal muscle construct [Abstract]
Preclinical musculoskeletal junction testbed: Optimisation of a reproducible skeletal muscle construct [Abstract
A review of the current state of the art of physiologically-based tests for measuring human dermal in vitro bioavailability of polycyclic aromatic hydrocarbons (PAH) in soil
Polycyclic Aromatic Hydrocarbons are classed as Persistent Organic Pollutants, a large group of compounds that share similar characteristics. They are lipophilic, resistant to degradation in the environment and harmful to human and environmental health. Soil has been identified as the primary reservoir for Polycyclic Aromatic Hydrocarbons in the United Kingdom. This study reviews the literature associated with, or is relevant to, the measurement and modelling of dermal absorption of Polycyclic Aromatic Hydrocarbons from soils. The literature illustrates the use of in vivo, in vitro and in silico methods from a wide variety of scientific disciplines including occupational and environmental exposure, medical, pharmaceutical and cosmetic research and associated mathematical modelling. The review identifies a number of practical shortcomings which must be addressed if dermal bioavailability tests are to be applied to laboratory analysis of contaminated soils for human health risk assessment
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