Science with ASKAP     

S. Johnston  R. Taylor  M. Bailes  N. Bartel  C. Baugh  M. Bietenholz  C. Blake  R. Braun  J. Brown  S. Chatterjee  J. Darling  A. Deller  R. Dodson  P. Edwards  R. Ekers  S. Ellingsen  I. Feain  B. Gaensler  M. Haverkorn  G. Hobbs  A. Hopkins  C. Jackson  C. James  G. Joncas  V. Kaspi  V. Kilborn  B. Koribalski  R. Kothes  T. Landecker  A. Lenc  J. Lovell  J.-P. Macquart  R. Manchester  D. Matthews  N. McClure-Griffiths  R. Norris  U.-L. Pen  C. Phillips  C. Power  R. Protheroe  E. Sadler  B. Schmidt  I. Stairs  L. Staveley-Smith  J. Stil  S. Tingay  A. Tzioumis  M. Walker  J. Wall  M. Wolleben 《Experimental Astronomy》2008,22(3):151-273

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Late Holocene environmental changes and anthropogenic impact in Dee Why Lagoon,New South Wales     

C. Chagué  D. Edwards  J. Ruszczyk  P. Gadd  A. Zawadzki  G. Jacobsen 《Australian Journal of Earth Sciences》2019,66(5):657-670

Late Holocene environmental changes were examined in Dee Why Lagoon, New South Wales, based on the sedimentological, geochemical and geochronological analysis of six cores collected from the fluvial delta and lagoon basin. The lagoon formed about 7300–7200?cal yr BP, following the post-glacial marine transgression and establishment of a sand barrier. Infilling of the lagoon occurred at a rate of 0.09–0.15?mm/yr until about 3300–3200?cal yr BP, when the barrier closed, resulting in mostly freshwater conditions, as evidenced by a change from pyrite-rich units to sediment containing little sulfur and a lack of foraminifera. Sedimentation rates increased to 0.23 then 0.43?mm/yr until about 100?years ago. Post-European land clearance led to an increase in sedimentation rates to 1.0–1.3?mm/yr on the fluvial delta, which are lower than those from other wave-dominated estuaries in New South Wales as well as those estimated by previous studies in Dee Why Lagoon. Our study shows that the fluvial delta started forming much earlier than originally thought, based on results of radiometric dating, and confirmed using sedimentological and geochemical data, as well as a critical examination of historic aerial photographs. Human impact has resulted in an increase in heavy metal (Cu, Pb, Zn) and metalloid (As) concentrations in the recent sediment, most likely attributed to stormwater discharge. Pb and As concentrations are above the ANZECC high sediment quality guideline values at the site closest to the stormwater outlet, with As-based pesticides one of the possible sources. Using the mean enrichment quotient, which is based on normalised Cu, Pb and Zn concentrations over their normalised background concentrations, we show that the surface sediments in Dee Why Lagoon are severely enriched, reflecting the recent anthropogenic impact that has also led to an increase in sedimentation rates.  相似文献   

Clitellate worms (Annelida) in lateglacial and Holocene sedimentary DNA records from the Polar Urals and northern Norway     

Youri Lammers  Charlotte L. Clarke  Christer Ersus  Antony G. Brown  Mary E. Edwards  Ludovic Gielly  Haflidi Haflidason  Jan Mangerud  Emilia Rota  John Inge Svendsen  Inger Greve Alsos 《Boreas: An International Journal of Quaternary Research》2019,48(2):317-329

While there are extensive macro‐ and microfossil records of a range of plants and animals from the Quaternary, earthworms and their close relatives amongst annelids are not preserved as fossils and therefore the knowledge of their past distributions is limited. This lack of fossils means that clitellate worms (Annelida) are currently underused in palaeoecological research, even though they can provide valuable information about terrestrial and aquatic environmental conditions. Their DNA might be preserved in sediments, which offers an alternative method for detection. Here we analyse lacustrine sediments from lakes in the Polar Urals, Arctic Russia, covering the period 24 000–1300 cal. a BP, and NE Norway, covering 10 700–3300 cal. a BP, using a universal mammal 16S rDNA marker. While mammals were recorded using the marker (reindeer was detected twice in the Polar Urals core at 23 000 and 14 000 cal. a BP, and four times in the Norwegian core at 11 000 cal. a BP and between 3600–3300 cal. a BP), worm extracellular DNA ‘bycatch’ was rather high. In this paper we present the first reported worm detection from ancient DNA. Our results demonstrate that both aquatic and terrestrial clitellates can be identified in late‐Quaternary lacustrine sediments, and the ecological information retrievable from this group warrants further research with a more targeted approach.  相似文献   

Near‐surface hydraulic conductivity of northern hemisphere glaciers          下载免费PDF全文

Ian T. Stevens  Tristram D.L. Irvine‐Fynn  Philip R. Porter  Joseph M. Cook  Arwyn Edwards  Martin Smart  Brian J. Moorman  Andy J. Hodson  Andrew C. Mitchell 《水文研究》2018,32(7):850-865

The hydrology of near‐surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments. To elucidate the hydrological characteristics of this near‐surface glacial weathering crust, we describe the design and operation of a capacitance‐based piezometer that enables rapid, economical deployment across multiple sites and provides an accurate, high‐resolution record of near‐surface water‐level fluctuations. Piezometers were employed at 10 northern hemisphere glaciers, and through the application of standard bail–recharge techniques, we derive hydraulic conductivity (K) values from 0.003 to 3.519 m day^?1, with a mean of 0.185 ± 0.019 m day^?1. These results are comparable to those obtained in other discrete studies of glacier near‐surface ice, and for firn, and indicate that the weathering crust represents a hydrologically inefficient aquifer. Hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short‐wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance. The large range of K observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography. Our data demonstrate a greater complexity of near‐surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production. The conductivities reported here, coupled with typical supraglacial channel spacing, suggest that meltwater can be retained within the weathering crust for at least several days. Not only does this have implications for the accuracy of predictive meltwater run‐off models, but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments, impurities, microbes, and nutrients to downstream ecosystems. Because continued atmospheric warming will incur rising snowline elevations and glacier thinning, the supraglacial hydrological system may assume greater importance in many mountainous regions, and consequently, detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained.  相似文献   

VSOP and ground-based VLBI observations of Markarian 421     

B. G. Piner  S. C. Unwin  A. E. Wehrle  P. G. Edwards  A. L. Fey  K. A. Kingham 《New Astronomy Reviews》1999,43(8-10)

We have produced 22 VLBI images of the TeV blazar Markarian 421 at 11 epochs, including a Space VLBI observation with the HALCA satellite. We measure the speeds of the three innermost jet components to be 0.64±0.33, 0.48±0.09, and 0.06±0.09c (H₀=65 km s⁻¹ Mpc⁻¹). Interpretation of these subluminal speeds in terms of the high Doppler factor demanded by the TeV observations is discussed.  相似文献   

Coral Transplantation: A Useful Management Tool or Misguided Meddling?     

Alasdair J. Edwards  Susan Clark 《Marine pollution bulletin》1999,37(8-12):474-487

The primary objectives of coral transplantation are to improve reef ‘quality' in terms of live coral cover, biodiversity and topographic complexity. Stated reasons for transplanting corals have been to: (1) accelerate reef recovery after ship groundings, (2) replace corals killed by sewage, thermal effluents or other pollutants, (3) save coral communities or locally rare species threatened by pollution, land reclamation or pier construction, (4) accelerate recovery of reefs after damage by Crown-of-thorns starfish or red tides, (5) aid recovery of reefs following dynamite fishing or coral quarrying, (6) mitigate damage caused by tourists engaged in water-based recreational activities, and (7) enhance the attractiveness of underwater habitat in tourism areas. Whether coral transplantation is likely to be effective from a biological standpoint depends on, among other factors, the water quality, exposure, and degree of substrate consolidation of the receiving area. Whether it is necessary (apart from cases related to reason 3 above), depends primarily on whether the receiving area is failing to recruit naturally.

The potential benefits and dis-benefits of coral transplantation are examined in the light of the results of research on both coral transplantation and recruitment with particular reference to a 4.5 year study in the Maldives. We suggest that in general, unless receiving areas are failing to recruit juvenile corals, natural recovery processes are likely to be sufficient in the medium to long term and that transplantation should be viewed as a tool of last resort. We argue that there has been too much focus on transplanting fast-growing branching corals, which in general naturally recruit well but tend to survive transplantation and re-location relatively poorly, to create short-term increases in live coral cover, at the expense of slow-growing massive corals, which generally survive transplantation well but often recruit slowly. In those cases where transplantation is justified, we advocate that a reversed stance, which focuses on early addition of slowly recruiting massive species to the recovering community, rather than a short-term and sometimes short-lived increase in coral cover, may be more appropriate in many cases.  相似文献   

A novel index of susceptibility of rivers and their catchments to acidification in regions subject to a maritime influence     

C. C. White  R. Smart  M. Stutter  M. S. Cresser  M. F. Billett  E. A. Elias  C. Soulsby  S. Langan  A. C. Edwards  A. Wade  R. Ferrier  C. Neal  H. Jarvie  R. Owen 《Applied Geochemistry》1999,14(8):369

A simple, unifying approach to classifying quantitatively the susceptibility of catchment soils and surface waters to acidification is suggested. In areas subject to a strong maritime influence, such as the UK and substantial parts of NW Europe, wherever soil mineral weathering rates are low and soils are unfertilised, atmospherically derived base cations of maritime origins have a greater effect than those derived from biogeochemical weathering on the exchangeable soil base cations. This is directly reflected in the relative base cation concentrations of the associated drainage waters, which become increasingly Na-dominated. Using 10 sub-catchments of the River Dee in north-eastern Scotland, it is shown here that the extent of Na dominance, the ratio of Na⁺ to ΣNa⁺+Ca²⁺+Mg²⁺, at any point in a river provides a quantitative index of the upstream weathering rate and thus of the susceptibility of the river concerned to acidification under diverse flow conditions. Data from a further 58 sub-catchments from the same river system, and from 4 other catchments from around Scotland, were used to validate this theory.  相似文献   

Comparison of trends in stream water quality     

J. M. Potts  D. Hirst  J. D. Miller  A. C. Edwards  D. A. Elston 《水文研究》2003,17(12):2449-2462

A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying trend. The method involves fitting the model twice, once with the underlying trends constrained to be identical for each river and once with the trends unconstrained. Statistical properties are assessed by simulation methods that allow for the autocorrelation in the residuals from the unconstrained fit. The method is applied to data from two streams in the Balquhidder catchments in the Highlands of Scotland and to data from the Dee, Don and Ythan rivers in the north‐east of Scotland. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

贵州荔波地区2000年来石笋高分辨率的气候记录   总被引：10，自引：1，他引：9  

张美良  程海  林玉石  覃嘉铭  朱晓燕  冉景丞  杨琰  陈会明  Edwards R L 《沉积学报》2006,24(3):339-348

通过对荔波董哥洞石笋进行高精度的ICP MS或TIMS U系测年和碳、氧同位素分析,建立了荔波地区2 300a B.P.来高分辨率的古气候变化的时间序列。研究结果表明,贵州荔波地区2 300a B.P.以来石笋记录的季风气候变化,大致可分为8个气候(亚)期:① 2 300～1 800a B.P.为降温期,显示东亚夏季风减弱,东亚冬季风增强,气候干旱寒冷;② 1 800～1 080a B.P.气温有所回升,显示东亚冬季风缓慢减弱,东亚夏季风有所回升,表现为半湿润的温凉气候期;③ 1 080～680a B.P. 为降温期,气温再次下降,显示东亚冬季风再次增强,但降水相对增大,表现为寒冷湿润的气候期,是气候变化的关键转折时期;④ 680～550a B.P.温暖期,显示东亚夏季风再次增强,气温升高,降水增大,表现为温暖湿润的气候期。⑤ 550～400a B.P.寒冷期,显示东亚冬季风快速增强,气温下降,表现为寒冷湿润的气候环境,是近1 000年以来最冷的时期;⑥ 400～364a B.P.温凉期,显示东亚夏季风有所增强,气温有所回升,表现为温凉湿润气候环境;⑦ 364～324a B.P.冷凉期,显示东亚夏季风有所减弱,气温有所下降,表现为冷凉湿润气候环境;⑧ 324a B.P.至今,气候相对波动期,同位素记录曲线呈锯齿状波动,在其内包括若干个冷凉半湿润、冷湿的气候变化亚阶段。根据荔波董哥洞石笋的高分辨率的古气候变化的连续记录,揭示了荔波地区2 300a B.P.以来的一些百年尺度的重大气候事件——干旱寒冷期、隋唐温暖期(或小温暖期)、小寒冷期以及一些十年尺度的降水、温度变化。石笋记录的这种百年、十年尺度的突发性气候变化事件,与冰芯记录极为相似,反映低纬度地区石笋记录的季风气候与高纬度及北极地区的气候具有极好的相关性,这对于认识现代气候系统变化以及对未来十年—百年尺度的气候预测和演化的驱动机制,具有重要的科学意义。  相似文献   

Rock fall hazard control along a section of railway based on quantified risk     

Renato Macciotta  C. Derek Martin  David M. Cruden  Michael Hendry  Tom Edwards 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(3):272-284

Rock falls represent a large percentage of landslide-related hazards reported by Canadian railways in mountainous terrain. A 54.7?km-long section of railway through the Canadian Cordillera is examined that experiences, on average, 18 rock falls each year. An approach for rock fall hazard management is developed based on quantified risk. The approach focuses on defining railway operation procedures (freight train operations and track maintenance) that comply with quantified risks. Weather-based criteria that define periods when rock falls are more likely to occur along the study area are examined. These criteria are used herein to reduce exposure to rock falls and reduce their consequences. Several freight train operation strategies are proposed that comply with a tolerable level of risk adopted in this study for illustrative purposes. The approach provides a simple, flexible and practical strategy for railway operations that can be regularly adopted by the operators, and that is based on a more comprehensive assessment of quantified risk.  相似文献