Use of high-resolution mass spectrometry screening workflow of pesticides in a river catchment can lead to enhanced risk assessments.
Research Interests:
Chemcatcher® and POCIS passive sampling devices are widely used for monitoring polar organic pollutants in water. Chemcatcher® uses a bound Horizon Atlantic™ HLB-L sorbent disk as receiving phase, whilst the POCIS uses the same material... more
Chemcatcher® and POCIS passive sampling devices are widely used for monitoring polar organic pollutants in water. Chemcatcher® uses a bound Horizon Atlantic™ HLB-L sorbent disk as receiving phase, whilst the POCIS uses the same material in the form of loose powder. Both devices (n = 3) were deployed for 21 days in the final effluent at three wastewater treatment plants in South Wales, UK. Following deployment, sampler extracts were analysed using liquid chromatography time-of-flight mass spectrometry. Compounds were identified using an in-house database of pharmaceuticals using a metabolomics workflow. Sixty-eight compounds were identified in all samplers. For the POCIS, substantial losses of sorbent (11–51%) were found during deployment and subsequent laboratory analysis, necessitating the use of a recovery factor. Percentage relative standard deviations varied (with 10 compounds exceeding 30% in both samplers) between individual compounds and between samplers deployed at the three...
Research Interests:
Increased concentrations of phosphorus (P) in riverine systems lead to eutrophication and can contribute to other environmental effects. Chalk rivers are known to be particularly sensitive to elevated P levels. We used high-frequency... more
Increased concentrations of phosphorus (P) in riverine systems lead to eutrophication and can contribute to other environmental effects. Chalk rivers are known to be particularly sensitive to elevated P levels. We used high-frequency (daily) automatic water sampling at five distinct locations in the upper River Itchen (Hampshire, UK) between May 2016 and June 2017 to identify the main P species (including filterable reactive phosphorus, total filterable phosphorus, total phosphorus and total particulate phosphorus) present and how these varied temporally. Our filterable reactive phosphorus (considered the biologically available fraction) data were compared with the available Environment Agency total reactive phosphorus (TRP) values over the same sampling period. Over the trial, the profiles of the P fractions were complex; the major fraction was total particulate phosphorus with the mean percentage value ranging between 69 and 82% of the total P present. Sources were likely to be at...
Research Interests:
Research Interests:
Research Interests:
Being able to effectively monitor the molluscicide metaldehyde in river catchments is now of major importance in the UK.
Research Interests:
Acidic herbicides are used to control broad-leaved weeds. They are stable, water-soluble, and with low binding to soil are found frequently in surface waters, often at concentrations above the EU Drinking Water Directive limit of... more
Acidic herbicides are used to control broad-leaved weeds. They are stable, water-soluble, and with low binding to soil are found frequently in surface waters, often at concentrations above the EU Drinking Water Directive limit of 0.10 μg L. This presents a problem when such waters are abstracted for potable supplies. Understanding their sources, transport and fate in river catchments is important. We developed a new Chemcatcher passive sampler, comprising a 3M Empore™ anion-exchange disk overlaid with a polyethersulphone membrane, for monitoring acidic herbicides (2,4-D, dicamba, dichlorprop, fluroxypyr, MCPA, MCPB, mecoprop, tricolpyr). Sampler uptake rates (R = 0.044-0.113 L day) were measured in the laboratory. Two field trials using the Chemcatcher were undertaken in the River Exe catchment, UK. Time-weighted average (TWA) concentrations of the herbicides obtained using the Chemcatcher were compared with concentrations measured in spot samples of water. The two techniques gave ...
Research Interests:
Organotins present a toxicological risk to biota in the aquatic environment. Understanding the behaviour of these compounds in sediment is challenging, with sophisticated analytical techniques required for their measurement. We... more
Organotins present a toxicological risk to biota in the aquatic environment. Understanding the behaviour of these compounds in sediment is challenging, with sophisticated analytical techniques required for their measurement. We investigated the use of silica-bound sorbents for diffusive gradients in thin-films (DGT) adsorption gels to pre-concentrate five organotins (monobutlytin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPhT), triphenyltin (TPhT)) found frequently in coastal sediment. C8 sorbent showed optimum performance in uptake and recovery of organotins for pH and ionic strength ranges typical of coastal waters. Recoveries from adsorption gels deployed in filtered sea water were MBT = 123 ± 20%, DBT = 75 ± 12%, TBT = 81 ± 16%, DPhT = 72 ± 30%, TPhT = 58 ± 10% respectively. Devices were used to investigate DGT fluxes and pore water concentrations of organotins in coastal sediment collected from a contaminated site. DGT fluxes measured in sediment cores for the fi...
Research Interests:
... The procedure extracts firstly the labile fraction by a 25% acetic acid leach (eg, [Landing and Bruland, 1987] , [Fitzwater et al., 2003] , [Lewis and Landing, 1992] , [Löscher, 1999] and [Wells et al., 2000] ), with the residue after... more
... The procedure extracts firstly the labile fraction by a 25% acetic acid leach (eg, [Landing and Bruland, 1987] , [Fitzwater et al., 2003] , [Lewis and Landing, 1992] , [Löscher, 1999] and [Wells et al., 2000] ), with the residue after this extraction being completely digested with aqua ...
Research Interests:
Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently... more
Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently detected at impacted riverine sites, often at concentrations above the EU Drinking Water Directive limit of 0.1µgL-1 for an individual pesticide. This presents a problem when such waters are abstracted for use in the production of potable water supplies, as this chemical is difficult to remove using conventional treatment processes. Understanding the sources, transport and fate of this pollutant in river catchments is therefore important. We developed a new variant of the Chemcatcher® passive sampler for monitoring metaldehyde comprising a Horizon Atlantic™ HLB-L disk as the receiving phase overlaid with a polyethersulphone membrane. The sampler uptake rate (Rs) was measured in semi-static laboratory (Rs = 15.7mLday-1) and in-field (Rs = 17.8mLday-1) calib...
Research Interests:
Research Interests:
Research Interests:
The molluscicide metaldehyde (2,4,6,8-tetramethyl-1,3,5,7-tetraoxocanemetacetaldehyde) is an emerging pollutant. It is frequently detected in surface waters, often above the European Community Drinking Water Directive limit of 0.1 μg/L... more
The molluscicide metaldehyde (2,4,6,8-tetramethyl-1,3,5,7-tetraoxocanemetacetaldehyde) is an emerging pollutant. It is frequently detected in surface waters, often above the European Community Drinking Water Directive limit of 0.1 μg/L for a single pesticide. Gas chromatography mass spectrometry (GC-MS) can be used to determine metaldehyde in environmental waters, but this method requires time consuming extraction techniques prior to instrumental analysis. Use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) can overcome this problem. We describe a novel LC-MS/MS method, using a methylamine mobile phase additive, coupled with on-line sample enrichment that allows for the rapid and sensitive measurement of metaldehyde in surface water. Only the methylamine adduct of metaldehyde was formed with other unwanted alkali metal adducts and dimers being suppressed. As considerably less collision energy is required to fragment the methylamine adduct, a five-fold improvement in method sensitivity, compared to a previous method using an ammonium acetate buffer mobile phase was achieved. This new approach offers: •A validated method that meets regulatory requirements for the determination of metaldehyde in surface water.•Improved reliability of quantification over existing LC-MS/MS methods by using stable precursor ions for multiple reaction monitoring.•Low limits of quantification for tap water (4 ng/L) and river water (20 ng/L) using only 800 μL of sample; recoveries > 97%.
Research Interests:
... This weak dependence has been confirmed for silicone sam-plers (Rusina et al., 2010), but for SPMDs and nonpolar Chemcatchers a much stronger decrease has been observed (Huckins et al., 2006; Vrana et al., 2007). This ...
Research Interests:
Research Interests: Geology and Geochemistry
Research Interests:
Research Interests:
Sensors such as electrodes and optical fibre devices, optrodes, can be used to determine steep concentration gradients of chemical species in aquatic microenvironments, such as in the pore waters of surface sediments and microbial mats,... more
Sensors such as electrodes and optical fibre devices, optrodes, can be used to determine steep concentration gradients of chemical species in aquatic microenvironments, such as in the pore waters of surface sediments and microbial mats, but are limited to a restricted range of determinands. The highest-resolution measurements of trace-metal concentrations in pore waters, at about 1.25 mm, have been provided by a recently developed thin-film gel technique,, but the resultant metal distributions suggest that sub-millimetre-scale gradients need to be determined if the fluxes and cycling of the metals are to be fully quantified and understood. Here we report the development of this thin-film gel technique to measure Zn, Mn, Fe and As fluxes and concentrations at a resolution of 100 μm, and demonstrate the utility of the method in situ within the surface sediments and overlying microbial mat of a stream. Vertical profiles through the mat and sediments, and horizontal two-dimensional mapping just below the sediment-water interface, reveal the contrasting gradients, fluxes and remobilization niches of the four metal species at a sub-millimetre scale. The microbial mat appears to be an important regulator of the cycling of these metals. This technique has the potential to be extended to other chemical species and applied to other microenvironments with steep concentration gradients, such as redox boundaries, plant roots, animal burrows and sites of precipitation/dissolution in soils and sediments.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT A continuing issue in chemical oceanography and environmental monitoring is the need for frequent and continuous monitoring of analytes in complex matrices such as sea water and ground waters. Particularly for analytes at trace... more
ABSTRACT A continuing issue in chemical oceanography and environmental monitoring is the need for frequent and continuous monitoring of analytes in complex matrices such as sea water and ground waters. Particularly for analytes at trace levels such as Cu(II) in sea water, sampling and analysis of discrete specimens is costly, slow, labor intensive, employs ship time inefficiently, and risks error by contamination. We have developed a fluorescence lifetime- based fiber optic biosensor which demonstrates real time determination of free Cu(II) in coastal waters, in situ, with a subpicomolar detection limit.
Research Interests:
Research Interests:
Research Interests:
ABSTRACT A phytoplankton bloom shown to be naturally iron (Fe) induced occurs north of the Crozet Islands (Southern Ocean) every year, providing an ideal opportunity to study dissolved trace metal distributions within an island system... more
ABSTRACT A phytoplankton bloom shown to be naturally iron (Fe) induced occurs north of the Crozet Islands (Southern Ocean) every year, providing an ideal opportunity to study dissolved trace metal distributions within an island system located in a high nutrient low chlorophyll (HNLC) region. We present water column profiles of dissolved nickel (Ni), zinc (Zn), cobalt (Co), cadmium (Cd), lead (Pb), aluminium (Al), and manganese (Mn) obtained as part of the NERC CROZEX program during austral summer (2004-2005). Two stations (M3 and M1) were sampled downstream (north) of Crozet in the bloom area and near the islands, along with a control station (M2) in the HNLC zone upstream (south) of the islands. The general range found was for Ni, 4.64-6.31 nM; Zn, 1.59-7.75 nM; Co, 24-49 pM; Cd, 135-673 pM; Pb, 6-22 pM; Al, 0.13-2.15 nM; and Mn, 0.07-0.64 nM. Vertical profiles indicate little island influence to the south with values in the range of other trace metal deprived regions of the Southern Ocean. Significant removal of Ni and Cd was observed in the bloom and Zn was moderately correlated with reactive silicate (Si) indicating diatom control over the internal cycling of this metal. Higher concentrations of Zn and Cd were observed near the islands. Pb, Al, and Mn distributions also suggest small but significant atmospheric dust supply particularly in the northern region.