PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “PEAT”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2003

Effect of peat decomposition and mass loss on historic mercury records in peat bogs from patagonia.

Ombrotrophic peat bogs have been widely used to evaluate long-term records of atmospheric mercury (Hg) deposition. One of the major aims of these investigations is the estimation of the increase in atmospheric Hg fluxes during the industrial age compared to preindustrial fluxes. Comparability of Hg accumulation rates calculated from density, peat accumulation rates, and Hg concentrations requires linearity between these parameters. Peat formation is a dynamic process accompanied by intense mass loss and alteration of the organic material. Our investigations on three peat cores from the Magellanic Moorlands, Chile, indicate that Hg concentrations in peat strongly depend on peat humification. Moreover, differences in mass accumulation rates during peat evolution are not compensated by linear changes in density, peat accumulation, or Hg concentrations. We suggest that Hg accumulation rates be normalized to carbon accumulation rates to achieve comparability of Hg accumulation rates derived from differently altered peat sections. Normalization to the carbon accumulation rates reduces Hg accumulation rates in less degraded peat sections in the upper peat layers by factors of more than 2. Our results suggest that the increase in Hg deposition rates during modern times derived from ombrotrophic peat bogs are potentially overestimated if Hg accumulation rates are not corrected for mass accumulation rates.

Carbon↗
PubMed2005

Investigation of occupational radiation exposures to NORM at an Irish peat-fired power station and potential use of peat fly ash by the construction industry.

Annually, approximately 15% of Ireland's electricity requirement is provided through the combustion of 3 x 10(6) tonnes of peat. While the literature on coal-fired power generation is quite abundant, studies on the peat-fired power generation industry from a radiological point of view are scarce. A study of the largest Irish peat-fired power plant was initiated to review the potential occupational radiation exposures arising from the occurrence of naturally occurring radioactive material (NORM) at different stages of the industrial process and to investigate any radiological health consequences that may arise should peat fly ash be used as a component of building materials. Ambient gamma dose rate measurements, radon measurements, quantification of the occupational exposure from inhalation of airborne particles (personal air sampling) and gamma spectrometry analysis of peat, peat ash and effluent samples from the ash ponds were undertaken. The results indicate that the radiation dose received by any worker involved in the processing of the peat and the handling of the ash resulting from peat combustion does not exceed 150 microSv per annum. Regulatory control of the peat-fired power generation is therefore unnecessary according to the Irish legislation with regards to NORM. The potential use of peat fly ash as a by-product in the building industry was also found to have a negligible radiological impact for construction workers and for members of the public.

Air Pollutants, Radioactive↗
PubMed1989

Artificial radioactivity in fuel peat and peat ash in Finland after the Chernobyl accident.

The accident at the Chernobyl nuclear power plant in April 1986 caused very uneven deposition of radionuclides in Finland. The deposited radionuclides were found in relatively high concentrations in fuel peat and especially in peat ash because a thin surface layer of peat-production bogs was extracted as fuel peat soon after the fallout occurred. Concentrations of artificial radionuclides in fuel peat and peat ash were measured at six peat-fired power plants in Finland throughout the heating season 1986-87. Concentrations of 137Cs in composite peat samples varied between 30 and 3600 Bq kg-1 dry weight and in ash samples between 600 and 68,000 Bq kg-1. High concentrations in peat ash caused some restrictions to the utilization of peat ash for various purposes.

Accidents↗
PubMed2004

Suggested protocol for collecting, handling and preparing peat cores and peat samples for physical, chemical, mineralogical and isotopic analyses.

For detailed reconstructions of atmospheric metal deposition using peat cores from bogs, a comprehensive protocol for working with peat cores is proposed. The first step is to locate and determine suitable sampling sites in accordance with the principal goal of the study, the period of time of interest and the precision required. Using the state of the art procedures and field equipment, peat cores are collected in such a way as to provide high quality records for paleoenvironmental study. Pertinent field observations gathered during the fieldwork are recorded in a field report. Cores are kept frozen at -18 degree C until they can be prepared in the laboratory. Frozen peat cores are precisely cut into 1 cm slices using a stainless steel band saw with stainless steel blades. The outside edges of each slice are removed using a titanium knife to avoid any possible contamination which might have occurred during the sampling and handling stage. Each slice is split, with one-half kept frozen for future studies (archived), and the other half further subdivided for physical, chemical, and mineralogical analyses. Physical parameters such as ash and water contents, the bulk density and the degree of decomposition of the peat are determined using established methods. A subsample is dried overnight at 105 degree C in a drying oven and milled in a centrifugal mill with titanium sieve. Prior to any expensive and time consuming chemical procedures and analyses, the resulting powdered samples, after manual homogenisation, are measured for more than twenty-two major and trace elements using non-destructive X-Ray fluorescence (XRF) methods. This approach provides lots of valuable geochemical data which documents the natural geochemical processes which occur in the peat profiles and their possible effect on the trace metal profiles. The development, evaluation and use of peat cores from bogs as archives of high-resolution records of atmospheric deposition of mineral dust and trace elements have led to the development of many analytical procedures which now permit the measurement of a wide range of elements in peat samples such as lead and lead isotope ratios, mercury, arsenic, antimony, silver, molybdenum, thorium, uranium, rare earth elements. Radiometric methods (the carbon bomb pulse of (14)C, (210)Pb and conventional (14)C dating) are combined to allow reliable age-depth models to be reconstructed for each peat profile.

Environmental Monitoring↗
PubMed2002

The chronology of anthropogenic, atmospheric Pb deposition recorded by peat cores in three minerogenic peat deposits from Switzerland.

Peat cores were collected from three minerogenic peatlands in Switzerland: La Tourbière des Genevez (TGE), in Canton Jura; Gola di Lago (GDL), in Canton Ticino; and Mauntschas (MAU), in Canton Grisons. Chemical analyses of the pore waters and the peats document the increasingly minerogenic character with depth. In particular, the Sr concentration profile in the peats reflects the growing importance of mineral sediment dissolution with increasing distance below the peat surface. Despite this circumstance, Pb concentrations are greatest in the surface layers, and decrease with depth. Thus, dissolution of the basal sediments at these sites appears to be an unimportant source of Pb, compared with atmospheric deposition. Twenty-one new radiocarbon age dates for the three cores provide a chronology of Pb enrichment, and these are consistent with the record of atmospheric Pb deposition recorded by the ombrotrophic peat bog 'Etang de la Gruère' (EGR). Sediment samples from TGE and EGR were reacted at pH 5 with ammonium acetate to dissolve the carbonate fraction, filtered, and the residues analyzed using XRF. These analyses show that much of the Ca, Mg, Sr and Mn is lost when the carbonate fraction is dissolved, but this process does not measurably affect Pb. This finding suggests that carbonate dissolution dominates the weathering of the sediments underlying these peat deposits, but this fraction does not contain significant concentrations of Pb. Minerogenic peat deposits such as those described here, therefore, can serve as reliable archives of atmospheric Pb deposition, provided that mineral dissolution in the underlying sediments does not contribute measurably to the Pb inventory of the peat profile.

Air Pollutants↗
PubMed1985

Inoculant Production with Diluted Liquid Cultures of Rhizobium spp. and Autoclaved Peat: Evaluation of Diluents, Rhizobium spp., Peats, Sterility Requirements, Storage, and Plant Effectiveness.

Fully grown broth cultures of various fast- and slow-growing rhizobia were deliberately diluted with various diluents before their aseptic incorporation into autoclaved peat in polypropylene bags (aseptic method) or mixed with the peat autoclaved in trays (tray method). In a factorial experiment with the aseptic method, autoclaved and irradiated peat samples from five countries were used to prepare inoculants with water-diluted cultures of three Rhizobium spp. When distilled water was used as the diluent, the multiplication and survival of rhizobia in the peat was similar to that with diluents having a high nutrient status when the aseptic method was used. In the factorial experiment, the mean viable counts per gram of inoculant were log 9.23 (strain TAL 102) > log 8.92 (strain TAL 82) > log 7.89 (strain TAL 182) after 24 weeks of storage at 28 degrees C. The peat from Argentina was the most superior for the three Rhizobium spp., with a mean viable count of log 9.0 per g at the end of the storage period. The quality of inoculants produced with diluted cultures was significantly (P = 0.05) better with irradiated than with autoclaved peat, as shown from the factorial experiment. With the tray method, rhizobia in cultures diluted 1,000-fold or less multiplied and stored satisfactorily in the presence of postinoculation contaminants, as determined by plate counts, membrane filter immunofluorescence, and plant infection procedures. All strains of rhizobia used in both the methods showed various degrees of population decline in the inoculants when stored at 28 degrees C. Fast- and slow-growing rhizobia in matured inoculants produced by the two methods showed significant (P < 0.01) decline in viability when stored at 4 degrees C, whereas the viability of some strains increased significantly (P < 0.01) at the same temperature. The plant effectiveness of inoculants produced with diluted cultures and autoclaved peat did not differ significantly from that of inoculants produced with undiluted cultures and gamma-irradiated peat.

Journal Article↗
PubMed2002

Mercury(II) sorption to two Florida Everglades peats: evidence for strong and weak binding and competition by dissolved organic matter released from the peat.

The binding of mercury(II) to two peats from Florida Everglades sites with different rates of mercury methylation was measured at pH 6.0 and 0.01 M ionic strength. The mercury(II) sorption isotherms, measured over a total mercury(II) range of 10(-7.4) to 10(-3.7) M, showed the competition for mercury(II) between the peat and dissolved organic matter released from the peat and the existence of strong and weak binding sites for mercury(II). Binding was portrayed by a model accounting for strong and weak sites on both the peat and the released DOM. The conditional binding constants (for which the ligand concentration was set as the concentration of reduced sulfur in the organic matter as measured by X-ray absorption near-edge structure spectroscopy) determined for the strong sites on the two peats were similar (Kpeat,s = 10(21.8 +/- 0.1) and 10(22.0 +/- 0.1) M-1), but less than those determined for the DOM strong sites (Kdom,s = 10(22.8 +/- 0.1) and 10(23.2 +/- 0.1) M-1), resulting in mercury(II) binding by the DOM at low mercury(II) concentrations. The magnitude of the strong site binding constant is indicative of mercury(II) interaction with organic thiol functional groups. The conditional binding constants determined for the weak peat sites (Kpeat,w = 10(11.5 +/- 0.1) and 10(11.8 +/- 0.1) M-1) and weak DOM sites (Kdom,w = 10(8.7 +/- 3.0) and 10(7.3 +/- 4.5) M-1) were indicative of mercury(II) interaction with carboxyl and phenol functional groups.

Adsorption↗
PubMed1999

Interdependence of peat and vegetation in a tropical peat swamp forest.

The visual uniformity of tropical peat swamp forest masks the considerable variation in forest structure that has evolved in response to differences and changes in peat characteristics over many millennia. Details are presented of forest structure and tree composition of the principal peat swamp forest types in the upper catchment of Sungai Sebangau, Central Kalimantan, Indonesia, in relation to thickness and hydrology of the peat. Consideration is given to data on peat geochemistry and age of peat that provide evidence of the ombrotrophic nature of this vast peatland and its mode of formation. The future sustainability of this ecosystem is predicted from information available on climate change and human impact in this region.

Carbon Radioisotopes↗
PubMed2000

A new approach for quantifying cumulative, anthropogenic, atmospheric lead deposition using peat cores from bogs: Pb in eight Swiss peat bog profiles.

Peat cores taken from eight Swiss peatlands were used to calculate inventories of anthropogenic Pb using either Sc or Zr to quantify Pb derived from rock weathering. The shapes of the Pb/Sc and Pb/Zr profiles suggest that Pb was supplied exclusively by atmospheric deposition at all sites. At one of the sites (Etang de la Gruère), anthropogenic Pb was calculated using both Sc and Zr as the conservative reference element. Lithogenic Pb determined using Sc was twice that obtained using Zr, possibly because Zr resides only in zircons which are dense compared to pyroxene and amphibole which are the main Sc-bearing phases in the earth's crust. However, the inventory of 'natural' Pb (supplied almost entirely by soil dust) is dwarfed by the anthropogenic inventory such that anthropogenic Pb calculated using Sc and Zr agree to within 5%. The total amount of anthropogenic Pb accumulated in the bogs was calculated by simply adding the mass of anthropogenic Pb for each peat slice over the length of each core. Cumulative, anthropogenic Pb calculated in this way ranged from 1.0 to 9.7 g/m2 and showed pronounced regional differences: the site south of the Alps (Gola di Lago in Canton Ticino) with direct exposure to the heavily industrialized region of northern Italy received nearly 10 times more anthropogenic Pb as the sites in more remote alpine regions (Schöpfenwaldmoor in Canton Berne, and Mauntschas in Canton Grisons). The approach used here to calculate cumulative, anthropogenic, atmospheric Pb (CAAPb) is simple and robust, independent of the chronology of Pb deposition, and makes no assumptions about the immobility of Pb within the peat profile. Given the worldwide distribution of peat bogs, it should be possible to undertake continental and global inventories of atmospheric metal deposition, for both the natural and anthropogenic components of most trace metals of environmental interest.

Air Pollutants↗
PubMed2002

Atmospheric Pb deposition in Spain during the last 4600 years recorded by two ombrotrophic peat bogs and implications for the use of peat as archive.

Two ombrotrophic peat bogs in Northwestern Spain provided a history of 4600 years of Pb accumulation. Highest Pb concentrations (84-87 microg g(-1)) were found near the bogs' surface, but there were also other significant peaks (6-14 microg g(-1)), indicating pre-industrial atmospheric pollution. The enrichment factors (EFs) in both cores show a remarkably similar record. Atmospheric Pb pollution dates back to at least approximately 2500 years ago, reaching a first maximum during the Roman period. For the last 300 years, Pb EFs significantly increased due to industrial development, but the uppermost samples of the bogs show decreasing Pb EFs, probably due to the phasing out of leaded gasoline. These results are also supported by 206Pb/207Pb isotope ratios, as they continuously decrease from ca. 3000 BP until 2000 BP (from 1.275 at 4070 14C years BP to 1.182), indicating the growing importance of nonradiogenic Pb released from Iberian ores by ancient mining. Peat samples at a 3-5-cm depth are even less radiogenic (206Pb/107Pb = 1.157), indicating the strong influence of leaded gasoline. Despite the common history shared by the two bogs, striking differences were found for Pb enrichment, whether this was calculated by normalising to the Pb/Ti ratio of the upper continental crust or to the Pb/Ti ratios of peats from pre-anthropogenic times. This effect seems to be related to differences in Ti accumulation in both bogs, possibly due to physical fractionation of the airborne dust during wind transport. Enrichment has to be carefully considered when comparing the results obtained for different bogs, since our results suggest that normalising to crustal proportions is meaningless when the bulk of the deposition in an area is strongly influenced by short- and medium-range dust transport.

Air Pollutants↗
PubMed2005

Copper binding by peat fulvic and humic acids extracted from two horizons of an ombrotrophic peat bog.

We studied the binding of Cu(II) to humic acids and fulvic acids extracted from two horizons of an ombrotrophic peat bog by metal titration experiments at pH 4.5, 5.0, 5.5, and 6.0 and 0.1 M KNO3 ionic strength. Free metal ion concentrations in solution were measured using an ion selective electrode. The amounts of base required to maintain constant pH conditions were recorded and used to calculate H+/Cu2+ exchange ratios. The amount of Cu(II) bound to the humic fractions was greater than the amount bound to the fulvic fractions and only at the highest concentrations of metal ion the amount of Cu(II) sorbed by both fractions became equal. The proton to metal ion exchange ratios are similar for all humic substances, with values ranging from 1.0 to 2.0, and decreasing with increased pH. The amount of Cu(II) bound is practically independent of the horizon from which the sample was extracted. The results indicate that the humic substances show similar cation binding behaviour, despite the differences in chemical composition. The copper binding data are quantitatively described with the NICA-Donnan model, which allows to characterize only the carboxylic type binding sites. The values of the binding constants are higher for the humic acids than for the fulvic acids.

Adsorption↗