ISO Best Practices in Reference Material Certification and Use in Geoanalysis     

Jean S. Kane  Philip J. Potts 《Geostandards and Geoanalytical Research》2007,31(4):361-378

The International Organisation for Standardisation (ISO) has published many guides, or technical standards, of great value to analytical geochemists. Two of particular importance are Guide 33 (Uses of Certified Reference Materials) and Guide 35 (Certification of Reference Materials). Both were first developed in the 1980s and undergo regular review and updating by the Reference Materials Committee (REMCO) that operates within ISO. Recent revisions have focused on adding statistical rigour to both guides. Although this offers significant advantages for use by professional metrologists, there are consequent issues of comprehension by the analytical chemists who in fact have the greatest need of them. A major focus of Guide 35 is the development of reference material uncertainties that are in full compliance with the Guide on Measurement Uncertainty (GUM), jointly issued by ISO, IUPAC and others. Guide 35 details handling of uncertainty due to (1) degradation on the shelf and in transport, (2) sample heterogeneity and (3) inter‐method and inter‐laboratory bias, as well as within‐laboratory repeatability. The International Association of Geoanalysts has developed a protocol for reference material certification that applies Guide 35 to the specific needs of the geoanalytical community. The approach being taken by the IAG in developing GUM‐compliant uncertainties for its certified values is presented. Recommendations made in Guide 33 for how a laboratory should compare its own results with certified values in assessing laboratory accuracy are outlined. Additionally, the subject of misusing reference materials is discussed. The apparent misuse occurs because so few CRMs exist that meet critical measurement needs of geoanalytical laboratories and that also meet the rigorous metrological demands of the latest editions of the ISO Guides. All of the focus of the IAG certification programme has been to undertake certifications that would fill gaps in CRM availability and thus serve to limit this misuse.  相似文献   

Regional modeling of decadal rainfall variability over the Sahel     

Deborah Herceg  Adam H. Sobel  Liqiang Sun 《Climate Dynamics》2007,29(1):89-99

A regional climate model is used to investigate the mechanism of interdecadal rainfall variability, specifically the drought of the 1970s and 1980s, in the Sahel region of Africa. The model is the National Center for Environmental Prediction’s (NCEPs) Regional Spectral Model (RSM97), with a horizontal resolution of approximately equivalent to a grid spacing of 50 km, nested within the ECHAM4.5 atmospheric general circulation model (AGCM), which in turn was forced by observed sea surface temperature (SST). Simulations for the July–September season of the individual years 1955 and 1986 produced wet conditions in 1955 and dry conditions in 1986 in the Sahel, as observed. Additional July–September simulations were run forced by SSTs averaged for each month over the periods 1950–1959 and the 1978–1987. These simulations yielded wet conditions in the 1950–1959 case and dry conditions in the 1978–1987 case, confirming the role of SST forcing in decadal variability in particular. To test the hypothesis that the SST influences Sahel rainfall via stabilization of the tropospheric sounding, simulations were performed in which the temperature field from the AGCM was artificially modified before it was used to force the regional model. We modified the original 1955 ECHAM4.5 temperature profiles by adding a horizontally uniform, vertically varying temperature increase, taken from the 1986–1955 tropical mean warming in either the AGCM or the NCEP/National Center for Atmospheric Research Reanalysis. When compared to the 1955 simulations without the added tropospheric warming, these simulations show a drying in the Sahel similar to that in the 1986–1955 difference and to the decadal difference between the 1980s and 1950s. This suggests that the tropospheric warming may have been, at least in part, the agent by which the SST increases led to the Sahel drought of the 1970s and 1980s.  相似文献   

Climate change and population history in the Pacific Lowlands of Southern Mesoamerica   总被引：1，自引：0，他引：1  

Hector Neff  Deborah M. Pearsall  John G. Jones  Brbara Arroyo de Pieters  Dorothy E. Freidel 《Quaternary Research》2006,65(3):390-400

Core MAN015 from Pacific coastal Guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr. Chemical, pollen, and phytolith data, which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land, document Holocene climate variability that parallels the Maya lowlands and other New World tropical locations. Human population history in this region may be driven partly by climate variation: sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium B.P. Population growth and cultural florescence during a long, relatively moist period (2800–1200 B.P.) ended around 1200 B.P., a drying event that coincided with the Classic Maya collapse.  相似文献   

The Consumer Society and the Postmodern City by David B Clarke     

Deborah Leslie 《Area》2006,38(2):221-222

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The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study     

Morgan T. Jones  Deborah J. Hembury  Martin R. Palmer  Bill Tonge  W. George Darling  Susan C. Loughlin 《Bulletin of Volcanology》2011,73(3):207-222

The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO₂ emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO₂ due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO₂ is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s inhabitants.  相似文献   

Rare earth evidence concerning the origin of granites of the Isle of Skye,northwest Scotland     

R.S. Thorpe  P.J. Potts  M.B. Sarre 《Earth and Planetary Science Letters》1977,36(1):111-120

Eleven samples of Skye granites, two samples of Torridonian sandstone and one sample of Lewisian gneiss have been analysed for ten rare earth elements (REE) by neutron activation analysis. The granites are representative of the main granite centres and compositional types. All granites have sub-parallel light-REE-enriched patterns with chondrite-normalised Ce(Ce_N) = 78–263,Yb_N = 16–60and Ce_N/Yb_N = 2.9–8.0. REE patterns for the Lewisian gneiss and Torridonian sandstone are similar to each other, withCe_N = 32–61,Yb_N = 3–5and Ce_N/Yb_N = 8–18. These two rock types as well as the Glamaig granite have negligible Eu anomalies (Eu/Eu* > 0.9), and the other granites have Eu/Eu* in the range 0.83-0.34. The REE evidence suggests that Lewisian gneiss or Torridonian sandstone arenot suitable materials from which the granites could be derived by partial melting. The Western Red Hills granite intrusions show a systematic relation of REE content with Eu/Eu*. We suggest that the Glamaig granite is the most primitive, and was derived from a source with no Eu anomaly by fractional crystallization of a more basic magma. The later Western Red Hills granites might then have resulted from further fractional crystallization of magma with a composition like that of the Glamaig granite. The Coire Uaigneich and Eastern Red Hills granites may also be products of fractional crystallization, but from different magmas to those parental to the Western Red Hills granites. The basaltic parent magmas of the Skye granites may be “continental” tholeiites derived by interaction of basalt magma with Lewisian gneiss.  相似文献   

A comparison between subaerial and submarine eruptions at Kilauea Volcano, Hawaii: implications for the thermal viability of lateral feeder dikes     

Elisabeth A. Parfitt  Tracy K. P. Gregg  Deborah K. Smith 《Journal of Volcanology and Geothermal Research》2002,113(1-2)

Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre.  相似文献   

A Glossary of Terms and Definitions Used in Analytical Chemistry     

Philip J. Potts 《Geostandards and Geoanalytical Research》1997,21(1):157-161

Definitions of common terms used in analytical chemistry are listed. Most have international approval through the International Organisation for Standardisation. Others are terms that have not yet received formal ISO approval, but have wide international support.  相似文献   

Rare earth element mobility during granite alteration: Evidence from southwest England     

D.H.M. Alderton  J.A. Pearce  P.J. Potts 《Earth and Planetary Science Letters》1980,49(1):149-165

Geochemical analyses of granitic rocks from southwest England reveal that the rare earth elements (REE) were potentially mobile during hydrothermal and supergene alteration. In particular, trivalent REE were removed from the system during K-silicate alteration, Eu was lost during sericitic alteration; all REE were lost during tourmalinization, and light REE were lost during chloritization and argillic alteration. The fluids themselves had low concentrations of REE; in only one case (chloritization) were heavy REE introduced during alteration. Analysis of separated minerals indicated that the behaviour of the REE could be partly explained in terms of their different affinities for the primary and secondary assemblages. Thermodynamic calculations indicated that REE mobility is enhanced by the presence of fluorine in the alteration fluids partly because REE form more stable complexes with F than with Cl and partly because elements such as Ti, Zr and P that form REE-bearing minor phases are themselves potentially mobile.  相似文献   

Analysis and simulated diagenesis of kerogen in a Recent bottom mud from Mono Lake,California: a comparison with selected ancient kerogens     

Deborah S. Sklarew 《Geochimica et cosmochimica acta》1979,43(12):1949-1958

The insoluble organic matter, or kerogen, in a Recent bottom mud (<1000yr old) from Mono Lake, California, has been analyzed by vacuum pyrolysis-GC-MS and compared with the kerogen from several Precambrian rocks, including the Belingwe and Transvaal stromatolites. The Mono Lake kerogen consists mainly of cyclic and acyclic aliphatic components with lesser amounts of aromatics present. It is less aromatic and more susceptible to thermal degradation than the Precambrian kerogens, and its products show a much greater diversity especially among the unsaturated aliphatics and the heteroatomic components. The presence of these compounds, most notably 2,5-dimethylfuran, in the Mono Lake kerogen indicates a relatively rapid formation and incorporation into a young kerogen and suggests that their presence in the Precambrian kerogens, such as the Belingwe stromatolite, may be consistent with an ancient biological origin.In simulated diagenesis experiments the Recent mud was heated at 150°C for 3 months or 225°C for 8 months. The former was insufficient to affect the kerogen pyrolysis products. The latter, however, caused a large decrease in the heteroatomic components and a slight increase in the abundance of n-alkanes relative to that of the cyclic and branched alkanes. This suggests that the presence of some of these components in Precambrian rocks should be consistent with a high degree of preservation of these rocks, as appears to be the case for the Belingwe and Transvaal stromatolites.  相似文献