William Perkins - Academia.edu (original) (raw)
Papers by William Perkins
Quaternary International, Oct 1, 2012
ACS Symposium Series, 1993
... Ron Fuge, Fiona M. Pearce, Nicholas JG Pearce, and William T. Perkins ... Although Nordstrom ... more ... Ron Fuge, Fiona M. Pearce, Nicholas JG Pearce, and William T. Perkins ... Although Nordstrom (34) has suggested that Al tends to precipitate as amorphous or poorly crystalline Al(OH)3 at a pH of 4.6 and above, the data in the present study would suggest that appreciable ...
Potato dextrose agar (PDA) is one of the most commonly used media for the isolation and cultivati... more Potato dextrose agar (PDA) is one of the most commonly used media for the isolation and cultivation of fungi, with morphological features and pigmentation in culture often being important for identification of cultures. Cultivation of various fungi on different brands and batches of powdered (commercial) potato dextrose media revealed deficient pigmentation in five of 10 media tested. Reduced pigmentation on
Journal of Quaternary Science, 2013
ABSTRACTFour primary glass populations, well defined by their Sr, Ba and Y concentrations, occur ... more ABSTRACTFour primary glass populations, well defined by their Sr, Ba and Y concentrations, occur in the Youngest Toba Tuff (YTT), which was deposited during a supereruption of the Toba caldera complex in northern Sumatra 75 ka. Average concentrations of major and trace elements indicate a coherent, systematic variation of glass composition across populations. No clear pattern in the areal distribution of these four glass groups can be discerned. The multiple glass populations of the YTT easily distinguish it from the single homogeneous glass population of the Middle Toba Tuff (∼500 ka), as represented by its basal vitrophyre, and that of the Oldest Toba Tuff (∼800 ka), as represented by ash Layer D at the Ocean Drilling Program site 758 in the Indian Ocean.
Radiation Measurements, 2018
There is growing interest in rock surface burial and exposure luminescence dating for use in Quat... more There is growing interest in rock surface burial and exposure luminescence dating for use in Quaternary science and in archaeology. Such methods have enormous potential both in increasing the range of sedimentary contexts that can be dated, and improving the accuracy and the precision of dating within those contexts. Bleaching of the luminescence signal with depth into the rock surface is likely to vary with lithology. However, previous work on rock surface dating has not systematically studied the differences in light attenuation for rocks of different lithologies, or directly quantified the attenuation of light in different rock surfaces. This study investigates the attenuation of light in different rock types (greywacke, sandstone, two granites and quartzite) using two different approaches: 1) sunlight bleaching experiments, to assess the residual infrared stimulated luminescence signal measured at 50°C (IRSL 50) and the post-IR IRSL signal measured at 225°C (post-IR IRSL 225) at different depths within the rocks after different durations of exposure to daylight; and, 2) direct measurement of light attenuation in rock slices using a spectrometer. Data from the spectrometer shows that for all rocks, attenuation is greater for shorter wavelengths (∼400 nm) than longer ones. A consistent difference in attenuation coefficient is seen when comparing the IRSL 50 and the post-IR IRSL 225 signals; this is thought to reflect the different sensitivity of these two signals to infrared and visible light. Direct measurement using a spectrometer is much more rapid than undertaking a bleaching experiment, and also provides wavelength-resolved attenuation data. Comparison of the numerical values from the two approaches is complex, but they yield consistent results. For the samples analysed here, the rocks that appear lightest in colour show the least attenuation of light and the luminescence signals are bleached to the greatest depths, and are thus the most suitable for dating using luminescence.
Environmental Science and Pollution Research, 2015
Field-scale study of the influence of differing remediation strategies on trace metal geochemistr... more Field-scale study of the influence of differing remediation strategies on trace metal geochemistry in metal mine tailings from the Irish Midlands.
Mineralogical Magazine, 1993
Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian ... more Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian calcite marble within the gneissic basement in an internal part of the Caledonian mobile belt in Dove Bugt, North-East Greenland. It commonly occurs as vitreous black, idioblastic crystals (<7 mm in size) with combined rhombohedral and basal pinacoid forms. XRD data show that its space group is R3m and its unit cell dimensions are a 5.687 ± 0.002 Å and c 41.16 ± 0.02 Å. Electron microprobe and ICP-MS analyses have yielded BeO 5.51 wt.% and ranges in abundance (wt.%): Al2O3 68.74-70.63; Tot, Fe as FeO 6.76-7.89; MgO 12.17-13.98; and ZnO 3.22-4.47. ICP-MS analysis also revealed significant trace amounts of V 249 ppm, Cr 740 ppm and Ga 178 ppm. The crystallographic parameters and composition are broadly in accord with those of musgravite from the two other recorded occurrences, in Precambrian high-grade terrains in Australia and Antarctica, although mineral and rock associations in these...
Earth and Planetary Science Letters, 2002
We report new trace element data for an extensive suite of quench basalt glasses dredged from the... more We report new trace element data for an extensive suite of quench basalt glasses dredged from the southern Mid-Atlantic Ridge (MAR) between 40 ‡S and 52.5 ‡S. Ratios between highly incompatible trace elements are strongly correlated and indicate a systematic distribution of incompatible element enriched mid-ocean ridge basalt (MORB) (E-type: Zr/Nb = 5.9^19, Y/Nb = 0.9^8.4, (La/Sm) n = 1.0^2.9) and incompatible element depleted MORB (N-type: Zr/Nb = 30^69, Y/Nb = 11^29, (La/Sm) n = 0.48^0.79) along this section of the southern MAR. A notable feature of N-type MORB from the region is the higher than usual Ba/Nb (4^9), La/Nb (1.2^2.4) and primitive mantle normalised K/Nb ratios (s 1). Ba/Nb ratios in E-type MORB samples from 47.5 to 49 ‡S are especially elevated (s 10). The occurrence and geographic distribution of E-type MORB along this section of the southern MAR can be correlated with the ridge-centred Shona and off-axis Discovery mantle plumes. In conjunction with published isotope data for a subset of the same sample suite [Douglass et al., J. Geophys. Res. 104 (1999) 2941], a model is developed whereby prior to the breakup of Gondwana and the opening of the South Atlantic Ocean, the underlying asthenospheric mantle was locally contaminated by fluids/melts rising from the major Mesozoic subduction zone along the south^southwest boundary of Gondwana, leaving a subduction zone geochemical imprint (elevated (K/Nb) n and 87 Sr/ 86 Sr ratios, decreased 143 Nd/ 144 Nd ratios). Subsequent impingement of three major mantle plume heads (Tristan/Gough, Discovery, Shona) resulted in heating and thermal erosion of the lowermost subcontinental lithosphere and dispersal into the convecting asthenospheric mantle. With the opening of the ocean basin, continued plume upwelling led to plume^ridge interactions and mixing between geochemically enriched mantle derived from the
A series of small scale field trials have been conducted using dealginated seaweed to absorb meta... more A series of small scale field trials have been conducted using dealginated seaweed to absorb metals from circumneutral mine waters in mid Wales. These waters, issuing from disused 19 th century mines are often rich in Zn (up to 42 mg/L), Pb (up to 2.8 mg/L) and Cd (up to 100 μg/L) but are low in Fe (<<1 mg/L), a result of the dominantly sphalerite/galena mineralisation with very little associated pyrite. Pilot plants treating 1, 2 and 10 L/min show that in excess of 95% of the dissolved metals are removed from these mine waters for a period of time which depends on the volume of dealginated seaweed in the plant and the inflow concentration. Zinc is the first metal to become saturated in the dealginated seaweed, followed closely by Cd. In contrast, in some trials Pb removal continues at between 85-98% efficiency long after the dealginated seaweed had become saturated in Zn and Cd. Different sources of dealginated seaweed, which process different raw materials (Laminaria sp or Ascophyllum sp), behave in a different manner, with the processed Ascophyllum sp absorbing most metal.
In this paper a series of laboratory-scale experiments are described. These experiments have been... more In this paper a series of laboratory-scale experiments are described. These experiments have been used to characterise the behaviour of dealginated seaweed, a potential bioadsorber, for mine water remediation. The experiments are divided into two types, batch experiments and column experiments. Batch experiments show that the minimum contact time between the mine water and the adsorber is 10 minutes. In contrast to previous studies this paper shows that pH does not exert a strong control over the adsorption process. Single metal, isotherm, experiments show that dealginated seaweed shows a preferential uptake of Pb over Zn and Cd. Synthetic, multi-element mine water was used to show that the adsorption capacity of the dealginated seaweed was ~4% of the adsorber mass. Dealginated seaweed has the potential to remove toxic metals from mine discharges.
The Holocene, 1999
We report trace element (Mg, Sr and Ba) records based on laser ablation inductively coupled plasm... more We report trace element (Mg, Sr and Ba) records based on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from three coeval Holocene speleothems from Great Chamber in GB Cave, southwest England. The trace element records are placed on a common timescale on the basis of a suite of TIMS 230Th-234U ages. This permits assessment of the reproducibility of the trace element record in coeval speleothems. The trace element records are not coherent, raising dobuts over the reliability of individual trace element records as potential archives of palaeoenvironmental information. Mg/Sr in speleothem calcite has been proposed as a potential palaeothermometer as Mg partitioning into calcite from water is temperaturedependent, while Sr partitioning into calcite is temperature-independent. However, we present the results of calculations which demonstrate that the observed Mg/Sr values in the three stalagmites cannot have been produced by Holocene temperature changes alone and...
Quaternary Science Reviews, 2011
Old Crow tephra is the largest and most widespread Quaternary eruption presently known in eastern... more Old Crow tephra is the largest and most widespread Quaternary eruption presently known in eastern Beringia. Its major-and trace-element geochemistry, Fe-Ti oxides, and stratigraphic and paleoecological context indicate that it is the result of a single cataclysmic eruption. The proximal region may well have experienced tephra fallout from small eruptions just prior to or after the Old Crow event, but there is no evidence to indicate that the distal area was affected. We recalculate the glass fission-track age at 124 AE 10 ka, which, coupled with stratigraphic and paleoenvironmental reconstructions, indicates that deposition occurred prior to development of the last interglacial boreal forest, which suggests a latest Marine Isotope Stage (MIS) 6 age. The bulk tephra volume erupted is estimated by three different approaches, that are in broad agreement at w200 km 3 , but this result must be considered as tentative given the poor controls on definition of isopachs over such a large area. The source caldera, although presently unrecognized, is located in the eastern Aleutian arc, possibly at or near the Emmons Lake volcanic center.
Quaternary Research, 2013
Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay... more Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay at two sites along the Old Crow River, northern Yukon Territory, are rich in fossils and contain tephra beds. Surprise Creek tephra (SZt) occurs in the lower part of the alluvial sequence at CRH47 and Little Timber tephra (LTt) is present near the base of the exposure at CRH94. Surprise Creek tephra has a glass fission-track age of 0.17 ± 0.07 Ma and Little Timber tephra is 1.37 ± 0.12 Ma. All sediments at CRH47 have a normal remanent magnetic polarity and those near LTt at CRH94 have a reversed polarity — in agreement with the geomagnetic time scale. Small mammal remains from sediments near LTt support an Early Pleistocene age but the chronology is not so clear at CRH47 because of the large error associated with the SZt age determination. Tephrochronological and paleomagnetic considerations point to an MIS 7 age for the interglacial beds just below SZt at CRH47 and at Chester Bluffs in...
Quaternary International, 1996
Laser ablation inductively coupled plasma mass speca'ometry (LA-ICP-MS) has been applied to the a... more Laser ablation inductively coupled plasma mass speca'ometry (LA-ICP-MS) has been applied to the analysis of fine grained (125-250 pan) volcanic glass shards separated from tephra deposits. Our earlier calibration strategies used Ce as an internal standard (which required the use of another trace element analytical technique to determine Ce) followed by off-line data correction by comparison with well characterised glass separates. We have progressed from these cartier studies to use a minor isotope of a major element, routinely determined by EPMA in tephrochronological studies, as an internal standard for LA-ICP-MS analysis. Internal standards used during this study include 4.4r, 57 29Si, a°Si, or Ca for fully quantitative determinations, or Fe for a single internal standard-multi-element calibration (so called 'semiquantitative' analysis). No subsequent off-line data correction is required. The differences between each technique are minimal and choice of technique depends largely upon instrument sensitivity. As little as 80 Ixg of material is consumed during a single determination which takes approximately two minutes, and detection limits are below 1 part per million. Accuracy is generally 15% when compared with other analytical techniques, and precision may vary between 5 and 20%, the worse 'precisions' reflecting within-sample variability. Rare earth and other trace element data can be used to correlate or distinguish individual tephra deposits with confidence, and specific examples are illustrated with Quaternary tephra deposits from Alaska and India and Cretaceous tephra deposits from Banks Island in Arctic Canada.
Quaternary International, 2008
Sheep Creek tephra (SCt) consists of inflated, rhyolitic pumice with abundant plagioclase and hor... more Sheep Creek tephra (SCt) consists of inflated, rhyolitic pumice with abundant plagioclase and hornblende, lesser amounts of ferrian ilmenite and magnetite, and trace quantities of basaltic hornblende, augite, quartz, apatite, and zircon. It has an adakitic composition; the glass has low Y, Yb, and high La/Yb and Sr/Y values. Previously, compositional differences between samples were known to exist and thought to be due to derivation from a compositionally zoned magma involving several closely spaced eruptions. SCt was recognized as a useful stratigraphic marker across central Alaska and western Yukon with an age of 190ka.NewOSLdatesonaSCtoccurrenceinwesternYukonare190 ka. New OSL dates on a SCt occurrence in western Yukon are 190ka.NewOSLdatesonaSCtoccurrenceinwesternYukonare80 ka and force a reassessment of the earlier work. SCt is now known to be made up of several stratigraphic units: SCt-F (Fairbanks, Alaska; 200ka),SCt−CC(CanyonCreek,Alaska),andinthewesternYukon,SCt−C,SCt−K(200 ka), SCt-CC (Canyon Creek, Alaska), and in the western Yukon, SCt-C, SCt-K (200ka),SCt−CC(CanyonCreek,Alaska),andinthewesternYukon,SCt−C,SCt−K(80 ka), and SCt-A. Beds C, K, and A must be similar in age because of their close stratigraphic association at Ash Bend in Yukon. Compositional and temporal controls, including Sr isotopes, suggest Mount Drum in the Wrangell volcanic field as the source of the SCt beds. Revision of the age of the SCt beds in western Yukon means that the Reid Glaciation of Yukon is likely of MIS 6 age and probably correlates with the Delta Glaciation of Alaska. Further, the buried forest bed just below SCt-K in the Klondike goldfields must be of MIS 5 age, not MIS 7, as previously thought.
Quaternary International, 2011
Recent developments in laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) ha... more Recent developments in laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) have enabled improvements in spatial resolution and analytical detection limits. Here, the analysis of individual glass shards from tephra deposits using a 193 nm Excimer laser (producing ablation craters as small as 4 mm diameter), coupled to a magnetic sector ICP-MS, is described. Analyses of individual glass shards with crater diameters of 20 mm and 10 mm is essentially routine, and when element fractionation is corrected for, good accuracy is achieved. Analytical precision is good, being around AE15e30% at 1 ppm and around AE2e3% at 500 ppm from 10 mm diameter ablation craters, and lower limits of detection (LLD) are <1 ppm for most elements from 10 mm craters, when 25e28 trace elements are determined in a w20 s analysis. Neither 44 Ca nor 43 Ca can be used reliably as the internal standard for the analysis of rhyolites from 10 mm ablation craters, because CaO is close to the lower limit of quantitation (LLQ); thus 29 Si must be used, although either could be used in the analysis of basaltic glasses at 10 mm. With analyses at 6 mm or 4 mm, many trace elements in rhyolites (e.g. Zr, Ba, LREE, Y, Rb, U, Th) remain above the LLQ, but at this resolution, only Si can be used as an internal standard for glass analysis. Element fractionation is an issue for all analyses <20 mm in diameter, resulting from the formation of a thin melt film on the ablation crater walls. This melt film becomes an increasingly larger proportion of the volume of ablated material as crater diameters become smaller, because the surface area/volume ratio increases. Element retention or volatility from this melt film appears to cause much of the fractionation. For larger craters (20 mm) this fractionation appears to affect all compositions similarly. For many elements determined from smaller craters (10 mme4 mm) there is a systematic variation in the degree of fractionation with the glass (and thus melt film) composition. This relates to a change in the degree of polymerisation of the glass, with, for example, the REE being the most fractionated in polymerised rhyolitic samples at the smallest crater diameters (4 mm). This systematic behaviour, however, offers some hope for the analysis of a selection of abundant trace elements in individual shards of glass using ablation craters of 6 mm and 4 mm in diameter.
Quaternary International, Oct 1, 2012
ACS Symposium Series, 1993
... Ron Fuge, Fiona M. Pearce, Nicholas JG Pearce, and William T. Perkins ... Although Nordstrom ... more ... Ron Fuge, Fiona M. Pearce, Nicholas JG Pearce, and William T. Perkins ... Although Nordstrom (34) has suggested that Al tends to precipitate as amorphous or poorly crystalline Al(OH)3 at a pH of 4.6 and above, the data in the present study would suggest that appreciable ...
Potato dextrose agar (PDA) is one of the most commonly used media for the isolation and cultivati... more Potato dextrose agar (PDA) is one of the most commonly used media for the isolation and cultivation of fungi, with morphological features and pigmentation in culture often being important for identification of cultures. Cultivation of various fungi on different brands and batches of powdered (commercial) potato dextrose media revealed deficient pigmentation in five of 10 media tested. Reduced pigmentation on
Journal of Quaternary Science, 2013
ABSTRACTFour primary glass populations, well defined by their Sr, Ba and Y concentrations, occur ... more ABSTRACTFour primary glass populations, well defined by their Sr, Ba and Y concentrations, occur in the Youngest Toba Tuff (YTT), which was deposited during a supereruption of the Toba caldera complex in northern Sumatra 75 ka. Average concentrations of major and trace elements indicate a coherent, systematic variation of glass composition across populations. No clear pattern in the areal distribution of these four glass groups can be discerned. The multiple glass populations of the YTT easily distinguish it from the single homogeneous glass population of the Middle Toba Tuff (∼500 ka), as represented by its basal vitrophyre, and that of the Oldest Toba Tuff (∼800 ka), as represented by ash Layer D at the Ocean Drilling Program site 758 in the Indian Ocean.
Radiation Measurements, 2018
There is growing interest in rock surface burial and exposure luminescence dating for use in Quat... more There is growing interest in rock surface burial and exposure luminescence dating for use in Quaternary science and in archaeology. Such methods have enormous potential both in increasing the range of sedimentary contexts that can be dated, and improving the accuracy and the precision of dating within those contexts. Bleaching of the luminescence signal with depth into the rock surface is likely to vary with lithology. However, previous work on rock surface dating has not systematically studied the differences in light attenuation for rocks of different lithologies, or directly quantified the attenuation of light in different rock surfaces. This study investigates the attenuation of light in different rock types (greywacke, sandstone, two granites and quartzite) using two different approaches: 1) sunlight bleaching experiments, to assess the residual infrared stimulated luminescence signal measured at 50°C (IRSL 50) and the post-IR IRSL signal measured at 225°C (post-IR IRSL 225) at different depths within the rocks after different durations of exposure to daylight; and, 2) direct measurement of light attenuation in rock slices using a spectrometer. Data from the spectrometer shows that for all rocks, attenuation is greater for shorter wavelengths (∼400 nm) than longer ones. A consistent difference in attenuation coefficient is seen when comparing the IRSL 50 and the post-IR IRSL 225 signals; this is thought to reflect the different sensitivity of these two signals to infrared and visible light. Direct measurement using a spectrometer is much more rapid than undertaking a bleaching experiment, and also provides wavelength-resolved attenuation data. Comparison of the numerical values from the two approaches is complex, but they yield consistent results. For the samples analysed here, the rocks that appear lightest in colour show the least attenuation of light and the luminescence signals are bleached to the greatest depths, and are thus the most suitable for dating using luminescence.
Environmental Science and Pollution Research, 2015
Field-scale study of the influence of differing remediation strategies on trace metal geochemistr... more Field-scale study of the influence of differing remediation strategies on trace metal geochemistry in metal mine tailings from the Irish Midlands.
Mineralogical Magazine, 1993
Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian ... more Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian calcite marble within the gneissic basement in an internal part of the Caledonian mobile belt in Dove Bugt, North-East Greenland. It commonly occurs as vitreous black, idioblastic crystals (<7 mm in size) with combined rhombohedral and basal pinacoid forms. XRD data show that its space group is R3m and its unit cell dimensions are a 5.687 ± 0.002 Å and c 41.16 ± 0.02 Å. Electron microprobe and ICP-MS analyses have yielded BeO 5.51 wt.% and ranges in abundance (wt.%): Al2O3 68.74-70.63; Tot, Fe as FeO 6.76-7.89; MgO 12.17-13.98; and ZnO 3.22-4.47. ICP-MS analysis also revealed significant trace amounts of V 249 ppm, Cr 740 ppm and Ga 178 ppm. The crystallographic parameters and composition are broadly in accord with those of musgravite from the two other recorded occurrences, in Precambrian high-grade terrains in Australia and Antarctica, although mineral and rock associations in these...
Earth and Planetary Science Letters, 2002
We report new trace element data for an extensive suite of quench basalt glasses dredged from the... more We report new trace element data for an extensive suite of quench basalt glasses dredged from the southern Mid-Atlantic Ridge (MAR) between 40 ‡S and 52.5 ‡S. Ratios between highly incompatible trace elements are strongly correlated and indicate a systematic distribution of incompatible element enriched mid-ocean ridge basalt (MORB) (E-type: Zr/Nb = 5.9^19, Y/Nb = 0.9^8.4, (La/Sm) n = 1.0^2.9) and incompatible element depleted MORB (N-type: Zr/Nb = 30^69, Y/Nb = 11^29, (La/Sm) n = 0.48^0.79) along this section of the southern MAR. A notable feature of N-type MORB from the region is the higher than usual Ba/Nb (4^9), La/Nb (1.2^2.4) and primitive mantle normalised K/Nb ratios (s 1). Ba/Nb ratios in E-type MORB samples from 47.5 to 49 ‡S are especially elevated (s 10). The occurrence and geographic distribution of E-type MORB along this section of the southern MAR can be correlated with the ridge-centred Shona and off-axis Discovery mantle plumes. In conjunction with published isotope data for a subset of the same sample suite [Douglass et al., J. Geophys. Res. 104 (1999) 2941], a model is developed whereby prior to the breakup of Gondwana and the opening of the South Atlantic Ocean, the underlying asthenospheric mantle was locally contaminated by fluids/melts rising from the major Mesozoic subduction zone along the south^southwest boundary of Gondwana, leaving a subduction zone geochemical imprint (elevated (K/Nb) n and 87 Sr/ 86 Sr ratios, decreased 143 Nd/ 144 Nd ratios). Subsequent impingement of three major mantle plume heads (Tristan/Gough, Discovery, Shona) resulted in heating and thermal erosion of the lowermost subcontinental lithosphere and dispersal into the convecting asthenospheric mantle. With the opening of the ocean basin, continued plume upwelling led to plume^ridge interactions and mixing between geochemically enriched mantle derived from the
A series of small scale field trials have been conducted using dealginated seaweed to absorb meta... more A series of small scale field trials have been conducted using dealginated seaweed to absorb metals from circumneutral mine waters in mid Wales. These waters, issuing from disused 19 th century mines are often rich in Zn (up to 42 mg/L), Pb (up to 2.8 mg/L) and Cd (up to 100 μg/L) but are low in Fe (<<1 mg/L), a result of the dominantly sphalerite/galena mineralisation with very little associated pyrite. Pilot plants treating 1, 2 and 10 L/min show that in excess of 95% of the dissolved metals are removed from these mine waters for a period of time which depends on the volume of dealginated seaweed in the plant and the inflow concentration. Zinc is the first metal to become saturated in the dealginated seaweed, followed closely by Cd. In contrast, in some trials Pb removal continues at between 85-98% efficiency long after the dealginated seaweed had become saturated in Zn and Cd. Different sources of dealginated seaweed, which process different raw materials (Laminaria sp or Ascophyllum sp), behave in a different manner, with the processed Ascophyllum sp absorbing most metal.
In this paper a series of laboratory-scale experiments are described. These experiments have been... more In this paper a series of laboratory-scale experiments are described. These experiments have been used to characterise the behaviour of dealginated seaweed, a potential bioadsorber, for mine water remediation. The experiments are divided into two types, batch experiments and column experiments. Batch experiments show that the minimum contact time between the mine water and the adsorber is 10 minutes. In contrast to previous studies this paper shows that pH does not exert a strong control over the adsorption process. Single metal, isotherm, experiments show that dealginated seaweed shows a preferential uptake of Pb over Zn and Cd. Synthetic, multi-element mine water was used to show that the adsorption capacity of the dealginated seaweed was ~4% of the adsorber mass. Dealginated seaweed has the potential to remove toxic metals from mine discharges.
The Holocene, 1999
We report trace element (Mg, Sr and Ba) records based on laser ablation inductively coupled plasm... more We report trace element (Mg, Sr and Ba) records based on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from three coeval Holocene speleothems from Great Chamber in GB Cave, southwest England. The trace element records are placed on a common timescale on the basis of a suite of TIMS 230Th-234U ages. This permits assessment of the reproducibility of the trace element record in coeval speleothems. The trace element records are not coherent, raising dobuts over the reliability of individual trace element records as potential archives of palaeoenvironmental information. Mg/Sr in speleothem calcite has been proposed as a potential palaeothermometer as Mg partitioning into calcite from water is temperaturedependent, while Sr partitioning into calcite is temperature-independent. However, we present the results of calculations which demonstrate that the observed Mg/Sr values in the three stalagmites cannot have been produced by Holocene temperature changes alone and...
Quaternary Science Reviews, 2011
Old Crow tephra is the largest and most widespread Quaternary eruption presently known in eastern... more Old Crow tephra is the largest and most widespread Quaternary eruption presently known in eastern Beringia. Its major-and trace-element geochemistry, Fe-Ti oxides, and stratigraphic and paleoecological context indicate that it is the result of a single cataclysmic eruption. The proximal region may well have experienced tephra fallout from small eruptions just prior to or after the Old Crow event, but there is no evidence to indicate that the distal area was affected. We recalculate the glass fission-track age at 124 AE 10 ka, which, coupled with stratigraphic and paleoenvironmental reconstructions, indicates that deposition occurred prior to development of the last interglacial boreal forest, which suggests a latest Marine Isotope Stage (MIS) 6 age. The bulk tephra volume erupted is estimated by three different approaches, that are in broad agreement at w200 km 3 , but this result must be considered as tentative given the poor controls on definition of isopachs over such a large area. The source caldera, although presently unrecognized, is located in the eastern Aleutian arc, possibly at or near the Emmons Lake volcanic center.
Quaternary Research, 2013
Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay... more Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay at two sites along the Old Crow River, northern Yukon Territory, are rich in fossils and contain tephra beds. Surprise Creek tephra (SZt) occurs in the lower part of the alluvial sequence at CRH47 and Little Timber tephra (LTt) is present near the base of the exposure at CRH94. Surprise Creek tephra has a glass fission-track age of 0.17 ± 0.07 Ma and Little Timber tephra is 1.37 ± 0.12 Ma. All sediments at CRH47 have a normal remanent magnetic polarity and those near LTt at CRH94 have a reversed polarity — in agreement with the geomagnetic time scale. Small mammal remains from sediments near LTt support an Early Pleistocene age but the chronology is not so clear at CRH47 because of the large error associated with the SZt age determination. Tephrochronological and paleomagnetic considerations point to an MIS 7 age for the interglacial beds just below SZt at CRH47 and at Chester Bluffs in...
Quaternary International, 1996
Laser ablation inductively coupled plasma mass speca'ometry (LA-ICP-MS) has been applied to the a... more Laser ablation inductively coupled plasma mass speca'ometry (LA-ICP-MS) has been applied to the analysis of fine grained (125-250 pan) volcanic glass shards separated from tephra deposits. Our earlier calibration strategies used Ce as an internal standard (which required the use of another trace element analytical technique to determine Ce) followed by off-line data correction by comparison with well characterised glass separates. We have progressed from these cartier studies to use a minor isotope of a major element, routinely determined by EPMA in tephrochronological studies, as an internal standard for LA-ICP-MS analysis. Internal standards used during this study include 4.4r, 57 29Si, a°Si, or Ca for fully quantitative determinations, or Fe for a single internal standard-multi-element calibration (so called 'semiquantitative' analysis). No subsequent off-line data correction is required. The differences between each technique are minimal and choice of technique depends largely upon instrument sensitivity. As little as 80 Ixg of material is consumed during a single determination which takes approximately two minutes, and detection limits are below 1 part per million. Accuracy is generally 15% when compared with other analytical techniques, and precision may vary between 5 and 20%, the worse 'precisions' reflecting within-sample variability. Rare earth and other trace element data can be used to correlate or distinguish individual tephra deposits with confidence, and specific examples are illustrated with Quaternary tephra deposits from Alaska and India and Cretaceous tephra deposits from Banks Island in Arctic Canada.
Quaternary International, 2008
Sheep Creek tephra (SCt) consists of inflated, rhyolitic pumice with abundant plagioclase and hor... more Sheep Creek tephra (SCt) consists of inflated, rhyolitic pumice with abundant plagioclase and hornblende, lesser amounts of ferrian ilmenite and magnetite, and trace quantities of basaltic hornblende, augite, quartz, apatite, and zircon. It has an adakitic composition; the glass has low Y, Yb, and high La/Yb and Sr/Y values. Previously, compositional differences between samples were known to exist and thought to be due to derivation from a compositionally zoned magma involving several closely spaced eruptions. SCt was recognized as a useful stratigraphic marker across central Alaska and western Yukon with an age of 190ka.NewOSLdatesonaSCtoccurrenceinwesternYukonare190 ka. New OSL dates on a SCt occurrence in western Yukon are 190ka.NewOSLdatesonaSCtoccurrenceinwesternYukonare80 ka and force a reassessment of the earlier work. SCt is now known to be made up of several stratigraphic units: SCt-F (Fairbanks, Alaska; 200ka),SCt−CC(CanyonCreek,Alaska),andinthewesternYukon,SCt−C,SCt−K(200 ka), SCt-CC (Canyon Creek, Alaska), and in the western Yukon, SCt-C, SCt-K (200ka),SCt−CC(CanyonCreek,Alaska),andinthewesternYukon,SCt−C,SCt−K(80 ka), and SCt-A. Beds C, K, and A must be similar in age because of their close stratigraphic association at Ash Bend in Yukon. Compositional and temporal controls, including Sr isotopes, suggest Mount Drum in the Wrangell volcanic field as the source of the SCt beds. Revision of the age of the SCt beds in western Yukon means that the Reid Glaciation of Yukon is likely of MIS 6 age and probably correlates with the Delta Glaciation of Alaska. Further, the buried forest bed just below SCt-K in the Klondike goldfields must be of MIS 5 age, not MIS 7, as previously thought.
Quaternary International, 2011
Recent developments in laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) ha... more Recent developments in laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) have enabled improvements in spatial resolution and analytical detection limits. Here, the analysis of individual glass shards from tephra deposits using a 193 nm Excimer laser (producing ablation craters as small as 4 mm diameter), coupled to a magnetic sector ICP-MS, is described. Analyses of individual glass shards with crater diameters of 20 mm and 10 mm is essentially routine, and when element fractionation is corrected for, good accuracy is achieved. Analytical precision is good, being around AE15e30% at 1 ppm and around AE2e3% at 500 ppm from 10 mm diameter ablation craters, and lower limits of detection (LLD) are <1 ppm for most elements from 10 mm craters, when 25e28 trace elements are determined in a w20 s analysis. Neither 44 Ca nor 43 Ca can be used reliably as the internal standard for the analysis of rhyolites from 10 mm ablation craters, because CaO is close to the lower limit of quantitation (LLQ); thus 29 Si must be used, although either could be used in the analysis of basaltic glasses at 10 mm. With analyses at 6 mm or 4 mm, many trace elements in rhyolites (e.g. Zr, Ba, LREE, Y, Rb, U, Th) remain above the LLQ, but at this resolution, only Si can be used as an internal standard for glass analysis. Element fractionation is an issue for all analyses <20 mm in diameter, resulting from the formation of a thin melt film on the ablation crater walls. This melt film becomes an increasingly larger proportion of the volume of ablated material as crater diameters become smaller, because the surface area/volume ratio increases. Element retention or volatility from this melt film appears to cause much of the fractionation. For larger craters (20 mm) this fractionation appears to affect all compositions similarly. For many elements determined from smaller craters (10 mme4 mm) there is a systematic variation in the degree of fractionation with the glass (and thus melt film) composition. This relates to a change in the degree of polymerisation of the glass, with, for example, the REE being the most fractionated in polymerised rhyolitic samples at the smallest crater diameters (4 mm). This systematic behaviour, however, offers some hope for the analysis of a selection of abundant trace elements in individual shards of glass using ablation craters of 6 mm and 4 mm in diameter.