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1.
Tephra abundance data and geochemistry in Late‐glacial and Holocene sediments on the East Greenland shelf are presented. Two well‐known tephras were identified from electron microprobe analysis of tephra shards picked from ash peaks in the cores. These are the Vedde Ash and Saksunarvatn Ash, which probably were deposited on the shelf after transport on drifting ice. The radiocarbon dates (marine reservoir corrected by −550 yr) that constrain the timing of deposition of the tephra layers compare well with the terrestrial and ice‐core ages of the tephras without requiring additional reservoir correction to align them with the known tephra ages. Several prominent tephra layers with a composition of Ash Zone 2 tephra punctuate the deglacial sediments. These tephra peaks coincide with significant light stable isotope events (signifying glacial meltwater) and fine‐grained sediments poor in ice‐rafted detritus. We interpret the Ash Zone 2 tephra peaks as sediment released from the Greenland Ice Sheet during strong melting pulses of the deglaciation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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A late Quaternary deep-water stratigraphic framework has been established for the deep-water areas (>450m) of the northern Rockall Trough and Faeroe-Shetland Channel. Four stratigraphic units (1–4) are identified; these are primarily biostratigraphic units based on dinoflagellate cyst evidence. Unit 1 represents the late Weichselian glacial (pre-13 000 yr BP); unit 2 the Late Glacial Interstadial (11 000-13 000 yr BP); unit 3 is of Younger Dryas age (10 000-11 000 yr BP); and unit 4 represents the Holocene interglacial (post-10 000 yr BP). This stratigraphy is supported by the discovery of the mixed Vedde Ash (10 600 yr BP) and North Atlantic Ash zone 1, and the Saksunarvatn Ash (9000–9100 yr BP), concentrated in units 3 and 4 respectively. The sedimentology indicates that the oceanographic regime underwent a major change between the glacial and interglacial stages. This is marked by the onset of strong bottom current activity, allied to the restoration of overflow of the Norwegian Sea Deep Water into the North Atlantic, towards the end of the Younger Dryas Stadial. Despite intense bioturbation and bottom-current reworking the basic stratigraphic framework is maintained. Recognition of two volcanic ash markers enables correlation with established onshore and offshore sequences of marine and non-marine environments. 相似文献
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Investigations of Lateglacial to Early Holocene lake sediments from the Nahe palaeolake (northern Germany) provided a high-resolution palynological record. To increase the temporal resolution of the record a targeted search for cryptotephra was carried out on the basis of pollen stratigraphy. Three cryptotephra horizons were detected and geochemically identified as G10ka series tephra (a Saksunarvatn Ash), Vedde Ash and Laacher See Tephra. Here we present the first geochemically confirmed finding of the ash from the Laacher See Eruption in Schleswig-Holstein—extending the so far detected fallout fan of the eruption further to the north-west. These finds enable direct stratigraphical correlations and underline the potential of the site for further investigations. 相似文献
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Trace elements concentrations were determined in 38 lignite samples and their corresponding 850 °C ash from two boreholes of the Domeniko coal deposit (Upper Miocene) in Elassona basin, Central Greece. The methods used were instrumental neutron activation analysis (INAA), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and atomic absorption spectroscopy (AAS). The results showed that all studied elements occur in concentrations within the range of reported values for different coal bearing basins of Greece. The elements U, Th, Cs, Eu, Ce, La, Li, Mo, Y, Pb, and Hg are enriched in the ashes when compared to their average concentration on the Earth's crust.Yb, Y, Lu, Th, La, Sm, Eu, Ce, and V showed positive (r>0.75) to intermediate (0.65<r<0.75) correlation. The elements Mo and As showed intermediate correlation. The rest of the elements poorly correlate with each other. 相似文献
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High‐resolution pollen, plant macrofossil and sedimentary analyses from early Holocene lacustrine sediments on the Faroe Islands have detected a significant vegetation perturbation suggesting a rapid change in climate between ca. 10 380 cal. yr BP and the Saksunarvatn ash (10 240±60 cal. yr BP). This episode may be synchronous with the decline in δ18O values in the Greenland ice‐cores. It also correlates with a short, cold event detected in marine cores from the North Atlantic that has been ascribed to a weakening of thermohaline circulation associated with the sudden drainage of Lake Agassiz into the northwest Atlantic, or, alternatively, a period with distinctly decreased solar forcing. The vegetation sequence begins at ca. 10 500 cal. yr BP with a succession from tundra to shrub‐tundra and increasing lake productivity. Rapid population increases of aquatic plants suggest high summer temperatures between 10 450 and 10 380 cal. yr BP. High pollen percentages, concentrations and influx of Betula, Juniperus and Salix together with macrofossil leaves indicate shrub growth around the site during the initial phases of vegetation colonisation. Unstable conditions followed ca. 10 380 cal. yr BP that changed both the upland vegetation and the aquatic plant communities. A decrease in percentage values of shrub pollen is recorded, with replacement of both aquatics and herbaceous plants by pioneer plant communities. An increase in total pollen accumulation rates not seen in the concentration data suggests increased sediment delivery. The catchment changes are consistent with less seasonal, moister conditions. Subsequent climatic amelioration reinitiated a warmth‐driven succession and catchment stabilisation, but retained high precipitation levels influencing the composition of the post‐event communities. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Liangju Zhao Honglang Xiao Xiaohong Liu Ren Juan Lu Mingfeng Zhou Maoxian 《Environmental Geology》2007,51(6):1049-1056
In different-aged sand-fixing zones and shifting sand dunes, the seasonal variations of foliar carbon isotope discrimination
(Δ), potassium (K) concentration and ash content were investigated in three dominated deserted plants (Artemisia ordosica, Hedysarum scoparium and Caragana korshinskii) during growth season in Shapotou, which is in the southeast margin of the Tengger Desert. The correlations of foliar Δ with
foliar K concentration and ash content were examined to evaluate the foliar K and ash content as surrogates of Δ in those
deserted plants. Results showed that there were significant effects of plant species, micro-habitation and growth season on
foliar Δ, K concentration and ash content. Foliar Δ of C. korshinskii was significantly lower than those of A. ordosica and H. scoparium, and K concentrations in A. ordosica were 2.14 and 2.36 times those of C. korshinskii and H. scoparium. At the same time, micro-habitation and the conditions in growth seasons had significant effects on foliar Δ, K concentration
and ash content. Ash content and K concentration were positively correlated to Δ in A. ordosica and H. scoparium, while there was significantly negative relationship between foliar K concentration and Δ in C. korshinskii. Thus, those findings suggest that foliar ash content and K concentration can serve as surrogates of carbon isotope discrimination
(Δ) in A. ordosica and H. scoparium, while they do not in C. korshinskii. This result implied that the correlations of foliar Δ with ash content and K concentration were various due to the physiological
features of plant species, and species differences should be fully considered when evaluating the surrogates of carbon isotope
discrimination in plants. 相似文献
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This paper investigates the impact ash fall would have on dairy farming, based on a study of ‘Tulachard’, a dairy farming
operation at Rerewhakaaitu, North Island, New Zealand. It includes analysis of the potential effects on the dairy shed and
milking machine, electrical supply and distribution, water supply and distribution, tractors and other farm vehicles, farm
buildings (haysheds, pump sheds, implement sheds, etc.), milk-tanker access to the farm and critical needs of dairy cows and
farm to keep milking. One of the most vulnerable areas identified in the study was the cooling of milk at the milking shed,
pending dairy tanker pick-up. The cooling system’s condenser is exposed to the atmosphere and falling ash would make it highly
vulnerable. Laboratory testing with wet and dry ash was conducted to determine its resilience to ash ingestion. It was found
to perform satisfactorily during dry testing, but during wet testing significant clogging/blocking of the condenser’s radiator
occurred, dramatically reducing airflow through the condenser. Specific mitigation recommendations have been developed that
include cleaning with compressed air and adapting farm management techniques to lessen usage of the condenser during an ash-fall
event. Specific recommendations for management of dairy farm operation are given to mitigate the effects of an ash-fall event.
相似文献
| James W. ColeEmail: |
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In 1995, the central heating plant Draken in Kalmar, Sweden, started manufacturing a granular ash product for nutrient recycling
to forest soil, instead of dumping the ash in landfills. Chemical composition, leaching and dissolution characteristics were
determined for the Draken wood ash, the dolomite used in granule manufacturing and the final granule product. The heavy metal concentrations in fly
ash were within the limit values recommended by the Swedish National Board of Forestry for ash recycling, except for Cd and
As levels which occasionally exceeded the limit values. The Ca, Mn and P levels were too low for nutrient recycling at the
time. Adding dolomite insures that the levels of the important nutrients Ca and Mg are sufficient in the granules. After 7
months in the field, about 60 % of Na and K was leached out from granules. Between 20 and 60% of trace elements Mo, Sc, V,
Y and Zr were leached out after 7 months. The release of Ca and Mg was low, 1–5% during 7 months.
Received: 12 July 1999 · Accepted: 31 August 1999 相似文献
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Microfacies and depositional environment of Tertiary Tanjung Enim low rank coal, South Sumatra Basin, Indonesia 总被引：2，自引：2，他引：2
The South Sumatra basin is among the most important coal producing basins in Indonesia. Results of an organic petrography study on coals from Tanjung Enim, South Sumatra Basin are reported. The studied low rank coals have a mean random huminite reflectance between 0.35% and 0.46% and are dominated by huminite (34.6–94.6 vol.%). Less abundant are liptinite (4.0–61.4 vol.%) and inertinite (0.2–43.9 vol.%). Minerals are found only in small amounts (0–2 vol.%); mostly as iron sulfide.Based on maceral assemblages, the coals can be grouped into five classes: (1) humotelinite-rich group, (2) humodetrinite-rich group, (3) humocollinite-rich group, (4) inertinite-rich group and (5) humodetrinite–liptinite-rich group. Comparing the distribution of maceral assemblages to the maceral or pre-maceral assemblages in modern tropical domed peat in Indonesia reveals many similarities. The basal section of the studied coal seams is represented typically by the humodetrinite–liptinite-rich group. This section might be derived from sapric or fine hemic peat often occurring at the base of modern peats. The middle section of the seams is characterized by humotelinite-rich and humocollinite-rich groups. The precursors of these groups were hemic and fine hemic peats. The top section of the coal seams is typically represented by the humodetrinite-rich or inertinite-rich group. These groups are the counterparts of fibric peat at the top of the modern peats. The sequence of maceral assemblages thus represents the change of topogenous to ombrogenous peat and the development of a raised peat bog.A comparison between the result of detailed maceral assemblage analysis and the paleodepositional environment as established from coal maceral ratio calculation indicates that the use of coal maceral ratio diagrams developed for other coal deposits fails to deduce paleo-peat development for these young tropical coals. In particular, mineral distribution and composition should not be neglected in coal facies interpretations. 相似文献
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The marine benthic fauna and the δ18Oc of foraminifers and ostracods from six sites situated on a west–east transect through central Sweden have been analysed in order to estimate the palaeosalinity and palaeocirculation in this shallow‐marine environment. The measurements have been undertaken on material from the early Preboreal, when the Baltic Basin was in contact with the North Sea through straits in central Sweden. The δ18Oc values have a more negative value towards the east, indicating decreasing salinity. This was the result of limited possibilities for marine water to penetrate into the Baltic Basin and the mixing with freshwater from the melting Fennoscandian ice‐sheet. Four water masses existed in the area: a surface layer of freshwater, marine water from the North Sea, brackish–marine intermediate water on the Swedish west coast and brackish Yoldia Sea water in the Baltic Basin. The chronology is based on radiocarbon dates of marine fossils and, at one site, on the occurrence of the Vedde Ash (10 400–10 300 14C yr BP). This is the first record from marine settings in Sweden. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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对柯林斯冰帽小冰穹冰芯中物质成分的研究，发现冰芯中有九层火山灰沉积。它们由玻屑（橙玄玻璃）、岩屑（黑色）和晶屑（长石、辉石、橄榄石和微量的钛铁氧化物）组成。长石为钠钙系列的中长石到拉长石。橄榄石为镁质的贵橄榄石。主要元素和微量元素分析结果表明，该类火山灰为玄武质成分，其ＳｉＯ２含量在５０ｗｔ％左右，Ｎａ２Ｏ大于Ｋ２Ｏ，并具有轻稀土元素轻微的富集、重稀土元素亏损、Ｅｕ正异常的特征。这些火山灰的存在，证实了近百年来南极地区的企鹅岛和欺骗岛的火山喷发活动。 相似文献
16.
Leaching characteristics of fly ash 总被引：6，自引：0，他引：6
Aysenur Ugurlu 《Environmental Geology》2004,46(6-7):890-895
The disposal of fly ash as a byproduct of thermic power stations, results in significant environmental problems. The leaching of coal fly ash during disposal is of concern for possible contamination, especially for the aquatic environment when ash is in contact with water. The aim of this study was to investigate the leaching behaviour of fly ashes currently disposed in Kemerkoy Power Plant (Turkey) fly-ash-holding pond. The studies were conducted with fly ashes from the electrostatic precipitators (fresh fly ash) and from the fly ash pond (pre-leached fly ash). The fly ashes has alkaline in nature and pH ranges between 11.9 to 12.2. The pre-leached fly ash exhibited lower EC values (7,400 µS) than the fresh fly ash (10,300 µS). In contrast to Fe and Pb, the elements such as Cr, Cd, Cu and Co did not leach from the fly ash. The Ca and Mn concentrations decreased with increasing temperature whereas, Na and K concentrations increased. The results showed that the most important effects of fly ash leaching were pH, Na, Ca, K, Fe, Mg, Mn and Pb. 相似文献
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以大量钻孔煤心化验成果及煤岩鉴定特征资料为基础,通过分析研究,利用各煤层煤的灰份、镜质组份指标的差异性进行煤层对比,很好地解决勘查中各煤层的编号归属. 相似文献
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Sean D. F. Pyne‐O'Donnell 《第四纪科学杂志》2007,22(6):559-570
Three new microtephras are reported from a number of lake sites from the Inner Hebrides and Scottish mainland. One occurs stratigrapically in the middle of Greenland Interstadial 1 (GI‐1) and has been named the Penifiler Tephra. It is rhyolitic and possesses a geochemical signature that is very similar to that of the Borrobol Tephra, which also occurs in three of the sequences reported here, but which lies close to the lower boundary of GI‐1. The second occurs stratigraphically in the early Holocene below the Saksunarvatn Ash and is named the Ashik Tephra. This tephra is geochemically bimodal, with a rhyolitic component comparable to the An Druim Tephra that occurs later in the Holocene, and a basaltic component which is similar to the Saksunarvatn Ash. A third tephra occurs stratigraphically above the Saksunarvatn Ash and is provisionally named the Breakish Tephra. The consistent inter‐site correlation demonstrated for these new tephras at several sites enhances the regional tephrostratigraphic framework, and increases the potential for correlating palaeoenvironmental events during GI‐1 and the early Holocene. However, the occurrence of multiple tephras with similar geochemistry in close stratigraphic and temporal proximity has implications for the rigour with which tephrostratigraphic investigations must be performed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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以大量钻孔煤心化验成果及煤岩鉴定特征资料为基础,通过分析研究,利用各煤层煤的灰份、镜质组份指标的差异性进行煤层对比,很好地解决勘查中各煤层的编号归属. 相似文献