Biomedical subjects

O F Donard

Publications and source records attributed to O F Donard.

12 recordsLinked to original sources

PubMed2001

Speciation of mercury in a fluid mud profile of a highly turbid macrotidal estuary (Gironde, France).

Mercury (Hg) speciation and partitioning have been investigated in a fluid mud profile collected in the high turbidity zone of the Gironde estuary. The formation of the fluid lens generates local and transient oxic-anoxic oscillations following the sedimentation-resuspension tidal cycles under a specific hydrodynamic regime. The total Hg concentration, ranging from 5 to 190 nM, increases with SPM concentration (4-174 g L-1) to a maximum at bottom. Particulate Hg averages 99% of total Hg. Particulate inorganic Hg (IHg(II)P) and monomethyl Hg (MMHgP) exhibit a similar trend: the maximum concentration is observed within the upper layer above the depth of 7 m and the minimum at the bottom layers of the fluid mud. Significant levels of "dissolved" (i.e. filter passing) Hg species (IHg(II)D, HgoD, MMHgD, DMHgD) are observed within the redox transition interface. In the sub/anoxic fluid mud layer, increasing concentrations of IHg(II)D and MMHgD coincide with decreasing concentrations of IHg(II)P and MMHgP, respectively. The distribution coefficient (log Kd) between the "dissolved" and particulate fraction for IHg(II) averages 4.5 +/- 0.2. A Kd minimum for IHg(II) is observed in the surface layer and at the bottom of the fluid mud and coincides with the maximum levels of dissolved Mn and Fe. Log Kd for MMHg averages 3.3 +/- 0.9 and presents the highest values (4.3-4.6) in the surface and the lowest (approximately 2.2) at bottom, corresponding to the particulate carbon profile. These results demonstrate that the fate of IHg(II) and MMHg in the fluid mud system is influenced by the redox cycling of major species such as carbon, Fe, and Mn. It is therefore suggested that the redox oscillations generated by fluid mud formation in the high turbidity zone affect the distribution and transfer of Hg species in macrotidal estuaries.

Environmental Monitoring↗

PubMed2001

Trends in certified reference materials for the speciation of trace elements.

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.

Animals↗

PubMed2001

Precise isotope-ratio measurements of lead species by capillary gas chromatography hyphenated to hexapole Multicollector ICP-MS.

The precision and accuracy of lead isotope-ratio determination on a short transient signal has been assessed by coupling capillary gas chromatography to the Isoprobe (Micromass, UK), a single-focusing inductively coupled plasma mass spectrometer with multicollector detection. A T-piece connecting the GC transfer line to the torch enabled continuous aspiration of thallium solution for mass-bias correction. The volatile lead species PbEt4 was derivatized from NIST isotopic certified lead standard SRM 981 and different amounts of PbEt4 dissolved in iso-octane were injected into the GC. Chromatograms were recorded in multicollection mode by use of Faraday cups; seven isotopes (204Pb, 206Pb, 207Pb, 208Pb,

Journal Article↗

PubMed2000

Chemical availability of mercury in stream sediments from the Almadén area, Spain.

The chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almadén, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercury can be extremely high (up to 1,000 mg kg(-1)), no organomercury compounds were detected (< 2 microg kg(-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almadén's sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar).

Biological Availability↗

PubMed2000

Field cryofocussing hydride generation applied to the simultaneous multi-elemental determination of alkyl-metal(loid) species in natural waters using ICP-MS detection.

Two hydride generation manifold systems, utilizing flow injection and cryotrapping techniques for alkyl-metal(loid) speciation analysis in natural waters, are described in this paper. They provide shipboard capacity for simultaneous derivatization of analytes with NaBH4 and cryotrapping of the generated products in a field packed column at -196 degrees C. The first system is a large-volume hydride generator, using a reagent-injection flow technique as a flow batch type, that has been fully optimized and applied to the simultaneous detection of alkylated species in estuarine waters. The technique permits the analysis of a large volume sample (0.5-11) at a sampling rate of 3 h-1. The second is an online continuous flow hydride generator. A sampling rate of 3-12 h-1 can be achieved with samples of 0.1-0.51. In addition, shipboard operation eliminates major problems related to sample pretreatment, transport and storage. Ultra-trace multi-element determination is finally performed in the laboratory by cryogenic GC hyphenated with ICP-MS. Routine detection limits of 0.5-10 pg (as metal) for 0.51 water samples were achieved for the selected alkyl-metal(loid) species of arsenic, germanium, mercury and tin. Concentrations of various species, obtained from water samples taken from the Rhine estuary, are also presented. These species include alkylated arsenic compounds, other than methyl derivatives, that have been tentatively identified and are reported here for the first time.

Chemistry Techniques, Analytical↗

PubMed1999

Ensuring quality in long term environmental monitoring for chemical speciation.

The awareness regarding quality assurance (QA) and quality control (QC) for environmental monitoring has considerably increased in the past few years, especially with respect to the determination of chemical species, since errors occurring at various levels may considerably affect the interpretation of results (e.g. studies of toxic impact, geochemical pathways, etc.). QA for environmental analysis covers a broad range of activities from sample collection to laboratory work and the approach for ensuring quality data should be considered in a global context. However, whereas great emphasis has been placed on QA within the laboratory, there have been few systematic attempts to evaluate risks of discrepancies related, for example, to field manipulations. The situation is even worse when monitoring is applied to relatively new fields such as chemical speciation. This paper outlines some of the main aspects of quality control of environmental analysis, including the validation of methods, sampling and sample handling, storage, etc., with special emphasis on the monitoring of chemical forms of elements (e.g. species of tin, mercury, lead and selenium).

Chemistry Techniques, Analytical↗

PubMed1998

Determination of butyltins in harbour sediment and water by aqueous phase ethylation GC-ICP-MS and hydride generation GC-AAS.

Sediment and water samples have been collected between 1992 and 1995 for evaluating butyltin contamination in two marinas from the coastal area in The Netherlands, two years after the ban of TBT. Sediments extracts were analysed by capillary gas chromatography-inductively coupled plasma-mass spectrometry. Sediment concentrations for TBT showed no trend of decrease between 1992 and 1995 and were extremely high in the marina secluded from tidal action; 17.5 +/- 8.0 microg g(-1) and much lower for the marina with tidal action; 0.117 +/- 0.073 microg g(-1). High ratios between TBT and DBT in the sediments indicate that degradation mechanisms in the sediments are of minor importance. Dissolved butyltin compounds were analysed in water by means of gas chromatography-atomic absorption spectrometry. Water concentrations of TBT showed no clear trend of decrease between 1992 and 1995 and were high in the marina secluded from tidal action; 139 +/- 166 ng litre(-1) but much lower for the marina with tidal action; 48 +/- 98 ng litre(-1). An active degradation mechanism during summer periods was indicated by low (<1) TBT/DBT ratios in the water phase of the marina secluded from tidal action.

Journal Article↗

PubMed1997

Thallium in French agrosystems-II. Concentration of thallium in field-grown rape and some other plant species.

The aim of this study was to assess thallium (Tl) uptake into the aerial parts of selected crop species grown on French soils with high Tl content of pedogeochemical origin (0.3-40 mg Tl kg(-1) on a dry wt (DW) basis). Husked wheat and maize grains contained less than 4 microg Tl kg(-1) DW, but rape shoots accumulated Tl with a shoot-soil partition coefficient (PC) > 1, and rape seeds had PC > 3. Tl content of rape seed reached 33 mg Tl kg(-1) DW and higher concentrations in soil corresponded to increased concentrations in rape seeds. It is argued that parent material of the soil and pedogenesis have a considerable effect on Tl accumulation in rape seeds. These results show enhanced phytoavailability of Tl of pedogeochemical origin and prompt questions on the potential for food chain contamination by Tl in rape cattle cakes.

Journal Article↗

PubMed1997

Organotin compounds in trimethyltin-treated rats and in human brain in Alzheimer's disease.

As blood tin concentrations are elevated in Alzheimer's disease and as some low molecular weight organotin compounds are neurotoxic, we have attempted to detect organotins in brain in Alzheimer's Disease. First we measured the concentration of trimethyltin (TMT) in the brains of rats which had been exposed to memory-impairing concentrations of TMT and, as the method of linking hydride generation, cryogenic trapping, gas chromotographic separation and atomic absorption spectrophotometric detection permitted the measurements of organotin compounds when the total tin was greater than 0.2 nanograms, we applied these techniques to human brain tissue, some of which showed neuropathological evidence of Alzheimer's Disease. No low molecular weight organotin compounds were detected in the human brain tissue, but it is possible that tin may be complexed with large organic molecules, the hydrides of which would not be volatile, but which could be identified by liquid chromatography.

Aged↗

PubMed1996

Three decades of tributyltin in the coastal environment with emphasis on Arcachon Bay, France.

This account briefly reviews the fate, bioconcentration and effects of tributyltin (TBT) three decades after its introduction into the coastal environment. Data on TBT-related events that occurred in Arcachon Bay (gastropod imposex, oyster recruitment failure, oyster shell malformations, concentrations in water and sediments) are revised and reinterpreted. Historically, TBT concentrations in the waters of the open bay seldom exceeded 1 ng Sn l(-1) in the 1960s, likely surpassed the range of 100 ng Sn l(-1) from 1977 to 1981 (years when no oyster spat were collected and the local shellfish industry collapsed), and decreased to about 1 ng Sn l(-1) in the late 1980s and early 1990s following legislation in January 1982 banning TBT use. TBT pollution is discussed in relation to the green tides that have developed in Arcachon Bay since 1982.

Journal Article↗

PubMed1994

Butyltin distribution in a sediment core from Arcachon harbour (France).

The concentrations of butyltin compounds in water, intertidal sediments and in a sediment core have been measured in the harbour of Arcachon (France) in order to assess the effectiveness of government legislative actions on the use of tributylin (TBT) in marine antifouling paints. The results revealed the occurrence of an increasing TBT gradient from the bottom to the top of the core with a maximum at 15 cm depth, and a slight decrease within the upper 15 cm. It is shown that the TBT levels are still very high in this area and that this compound is not rapidly degraded in sediment as was previously assumed. This leads to the conclusion that even if the regulations have been respected, contamination from resuspended sediments is still likely.

Journal Article↗

PubMed1993

Survey of butyltin contamination in Portuguese coastal environments.

Butyltin compounds (MBT, DBT and TBT) in intertidal sediments collected in four different Portuguese coastal environments have been measured in order to evaluate the extent of contamination. The sites chosen were the Rias of Aveiro and Faro, and the Sado and Tejo estuaries. These zones were traditional areas for shellfish production in the recent past, but the effects of industrial development have caused a deterioration of the environment. Specific contaminations were derived from the harbour (commercial and/or fisheries) and shipyard activities, resulting in a release of TBT and causing the oyster populations of the above mentioned estuaries to almost disappear. Results presented in this study give a survey of TBT contamination levels found in the four areas. The paper discusses the importance of the pollution in comparison with other European coastal areas.

Journal Article↗