Impact and recovery associated with the deposition of capital dredgings at UK disposal sites: Lessons for future licensing and monitoring   总被引：1，自引：0，他引：1  

Suzanne Ware  Stefan G. Bolam  Hubert L. Rees 《Marine pollution bulletin》2010,60(1):79-90

The majority of studies relating to impacts and recovery at dredgings disposal sites have concentrated on areas subject to regular and frequent disposals of maintenance dredgings over relatively long time periods. In comparison less is known regarding the significance of impacts and the recovery processes associated with the disposal of capital dredgings that commonly involves the infrequent deposition of heterogenous material over relatively restricted time periods. Impacts and recovery processes are likely to be different to those associated with the disposal of maintenance dredgings. For example, findings suggest that capital dredgings deposited at both the Roughs Tower and Barrow-in-Furness result in the occurrence of persistent changes to seafloor substrata within the license area and this subsequently effects the composition of associated faunal communities present. Moreover, whilst the two disposal sites are geographically distinct similar species are identified as being particularly sensitive to capital disposal activities in both areas.  相似文献   

Midges (Chironomidae,Ceratopogonidae, Chaoboridae) as a temperature proxy: a training set from Tasmania,Australia     

Andrew B. H. Rees  Les C. Cwynar  Peter S. Cranston 《Journal of Paleolimnology》2008,40(4):1159-1178

Chironomid and ceratopogonid head capsules, along with Chaoborus mandibles, were used to model mean temperature of the warmest quarter (TWARM) in Tasmania. Our transfer function is based on midge assemblages and 21 environmental variables sampled from 47 lakes. Canonical correspondence analysis (CCA) revealed seven variables that account for a significant (P ≤ 0.05) portion of the explainable variance. In order of explanatory power, these were pH, TWARM, annual radiation, magnesium, annual precipitation, SiO₂, and depth. TWARM was modeled using weighted averaging partial least squares (WA-PLS) and generated a model with and RMSEP = 0.94. Advances in chironomid paleoecology are progressing very quickly in the Southern Hemisphere. Chironomid identification guides and autecological data are available for many regions, highlighting the potential for developing midge-based quantitative models to address hemispheric and interhemispheric climate hypotheses.  相似文献   

Dissolved organic carbon delivery from managed flow releases in a montane snowmelt river     

Ann-Marie Rohlfs  Simon M. Mitrovic  Simon Williams  James N. Hitchcock  Gavin N. Rees 《Aquatic Sciences - Research Across Boundaries》2016,78(4):793-807

  相似文献   

The Twannberg (Switzerland) IIG iron meteorites: Mineralogy,chemistry, and CRE ages     

Beda A. HOFMANN  Silvio LORENZETTI  Otto EUGSTER  Urs KRÄHENBÜHL  Gregory HERZOG  Feride SEREFIDDIN  Edwin GNOS  Manuel EGGIMANN  John T. WASSON 《Meteoritics & planetary science》2009,44(2):187-199

Abstract— The original mass (15915 g) of the Twannberg IIG (low Ni‐, high P) iron was found in 1984. Five additional masses (12 to 2488 g) were recovered between 2000 and 2007 in the area. The different masses show identical mineralogy consisting of kamacite single crystals with inclusions of three types of schreibersite crystals: cm‐sized skeletal (10.5% Ni), lamellar (17.2% Ni), and 1–3 × 10 μm‐sized microprismatic (23.9% Ni). Masses I and II were compared in detail and have virtually identical microstructure, hardness, chemical composition, cosmic‐ray exposure (CRE) ages, and ¹⁰Be and ²⁶Al activities. Bulk concentrations of 5.2% Ni and 2.0% P were calculated. The preatmospheric mass is estimated to have been at least 11,000 kg. The average CRE age for the different Twannberg samples is 230 ± 50 Ma. Detrital terrestrial mineral grains in the oxide rinds of the three larger masses indicate that they oxidized while they were incorporated in a glacial till deposited by the Rhône glacier during the last glaciation (Würm). The find location of mass I is located at the limit of glaciation where the meteorite may have deposited after transport by the glacier over considerable distance. All evidence indicates pairing of the six masses, which may be part of a larger shower as is indicated by the large inferred pre‐atmospheric mass.  相似文献   

Integrated analysis of risks of coastal flooding and cliff erosion under scenarios of long term change   总被引：2，自引：1，他引：1  

R. J. Dawson  M. E. Dickson  R. J. Nicholls  J. W. Hall  M. J. A. Walkden  P. K. Stansby  M. Mokrech  J. Richards  J. Zhou  J. Milligan  A. Jordan  S. Pearson  J. Rees  P. D. Bates  S. Koukoulas  A. R. Watkinson 《Climatic change》2009,95(1-2):249-288

The risks to human populations in coastal areas are changing due to climate and socio-economic changes, and these trends are predicted to accelerate during the twenty-first century. To understand these changing risks, and the resulting choices and pathways to successful management and adaptation, broad-scale integrated assessment is essential. Due to their complexity the two risks of flooding and erosion are usually managed independently, yet frequently they are interconnected by longshore exchange of sediments and the resulting broad scale morphological system behaviour. In order to generate new insights into the effects of climate change and coastal management practises on coastal erosion and flood risk, we present an integrated assessment of 72 km of shoreline over the twenty-first century on the East Anglian coast of England which is a site of significant controversy about how to manage coastal flood and erosion risks over the twenty-first century. A coupled system of hydrodynamic, morphological, reliability and socio-economic models has been developed for the analysis, implemented under scenarios of coastal management, climate and socio-economic change. The study is unique in coastal management terms because of the large spatial scale and extended temporal scale over which the analysis is quantified. This study for the first time quantifies what has for some years been argued qualitatively: the role of sediments released from cliff erosion in protecting neighbouring low-lying land from flooding. The losses and benefits are expressed using the common currency of economic risk. The analysis demonstrates that over the twenty-first century, flood risk in the study area is expected to be an order of magnitude greater than erosion risk. Climate and socio-economic change and coastal management policy have a significant influence on flood risk. This study demonstrates that the choices concerning coastal management are profound, and there are clear tradeoffs between erosion and flood impacts.  相似文献   

Depth distribution of chironomids and an evaluation of site-specific and regional lake-depth inference models: a good model gone bad?     

Les C. Cwynar  Andrew B. H. Rees  Cy R. Pedersen  Stefan Engels 《Journal of Paleolimnology》2012,48(3):517-533

We used 39 surface samples from Marcella Lake, Yukon Territory, to examine the distribution of chironomid head capsules in relation to depth and to develop a site-specific (intralake) inference model for reconstructing past lake levels. Ten of the 34 most-frequently occurring taxa encountered in the surface-sediment samples are significantly related to depth. We then applied the site-specific inference model and a previously developed regional model to samples from deep- and shallow-water cores from Marcella Lake. The inferences were compared to an independent Digerfeldt-type reconstruction of lake level history and to moisture inferences drawn from pollen data. Although the site-specific model was good in having better performance statistics than the regional model, it was bad at producing depth reconstructions because most samples from the long cores lacked suitable analogues in the site-specific training set. None of the chironomid-based reconstructions was a good match to the Digerfeldt-type reconstruction. Inconsistencies remain between the paleohydrological inferences derived from the chironomid depth models, the Digerfeldt-type reconstruction and pollen-inferred reconstructions of past moisture regimes.  相似文献   

Large-scale managed retreat and structural protection following the 2011 Japan tsunami     

Pinter  Nicholas  Ishiwateri  Mikio  Nonoguchi  Atsuko  Tanaka  Yumiko  Casagrande  David  Durden  Susan  Rees  James 《Natural Hazards》2019,96(3):1429-1436

Natural Hazards - On March 11, 2011, a magnitude MW 9.0 thrust earthquake ruptured the Japan Trench along the northwest coast of Honshu and generated a tsunami that killed 15,894 people, left 2585...  相似文献   

Use of a single-bowl continuous-flow centrifuge for dewatering suspended sediments: Effect on sediment physical and chemical characteristics     

Terry F. Rees  Jerry A. Leenheer  James F. Ranville 《水文研究》1991,5(2):201-214

The use of a single-bowl continuous-flow centrifuge (CFC, Sharples-Pennwalt Model AS-12) for dewatering suspended sediment from large volumes of river water is evaluated. Sediment-recovery efficiency of 86-91 per cent is comparable to that of other types of CFC units. The recovery efficiency is limited by the particle-size distribution of the feed water and by the limiting particle diameter that is retained in the centrifuge bowl. The limiting particle diameter, using the parameters for this study (bowl radius = 10.5cm; bowl length = 71.1 cm; rotational velocity = 16000 r min^?1; flow rate = 2 L min^?1, and an assumed hydrated particle density = 1.7 gm cm^?3), is 370 nm. There seems to be no particle-size fractionation within the centrifuge bowl—the median particle size was the same at the top as at the bottom. Particle electrophoretic mobility plays some role in fractionation of particles within the centrifuge. The mobility ranged from ?1.19 to ?2.01 × 10^?8 m² V^?1 s^?1, which is typical of clays coated with organic matter, the charge of which is partially neutralized by divalent cations and iron. Contamination by trace metals and organics is minimized by coating all surfaces that come in contact with the sample with either FEP or PFA Teflon and using a removable FEP Teflon liner in the centrifuge bowl. Because of the physical and chemical factors affecting particle fractionation within the centrifuge, care must be exercised in interpreting the environmental consequences of particles collected by continuous-flow centrifugation.  相似文献   

The consequences of high latitude particle precipitation on global thermospheric dynamics     

M. F. Smith  D. Rees  T. J. Fuller-Rowell 《Planetary and Space Science》1982,30(12):1259-1267

A previous comparison of experimental measurements of thermospheric winds with simulations using a global self-consistent three-dimensional time-dependent model confirmed a necessity for a high latitude source of energy and momentum acting in addition to solar u.v. and e.u.v. heating. During quiet geomagnetic conditions, the convective electric field over the polar cap and auroral oval seemed able to provide adequate momentum input to explain the thermospheric wind distribution observed in these locations. However, it seems unable to provide adequate heating, by the Joule mechanism, to complete the energy budget of the thermosphere and, more importantly, unable to provide the high latitude input required to explain mean meridional winds at mid-latitudes. In this paper we examine the effects of low energy particle precipitation on thermospheric dynamics and energy budget. Modest fluxes over the polar cap and auroral oval, of the order of 0.4 erg cm ⁻²/s, are consistent with satellite observations of the particles themselves and with photometer observations of the OI and OII airglow emissions. Such particle fluxes, originating in the dayside magnetosheath cusp region and in the nightside central plasma sheet, heat the thermosphere and modify mean meridional winds at mid-latitudes without enhancing the OI 557.7 line, or the ionization of the lower thermosphere (and thus enhancing the auroral electrojets), neither of which would be consistent with observations during quiet geomagnetic conditions.  相似文献   

Time dependent studies of the aurora—II. Spectroscopic morphology     

M.H. Rees  R.A. Jones 《Planetary and Space Science》1973,21(7):1213-1235

The temporal morphology of auroral spectral emission features is investigated. For a given energy distribution of bombarding electrons but a time varying flux magnitude, the emission rates of various auroral radiations exhibit a nonlinear time response due to the variety of reactions that contribute to excitation. Absolute intensities and intensity ratios of various spectroscopic features, therefore, can vary solely with atmospheric interaction effects, indicating the importance of considering the time history of a precipitation event when attempting to infer the characteristics of auroral electrons from optical measurements.  相似文献