Devensian Late-glacial environmental change in the Gordano Valley, North Somerset, England: a rare archive for southwest Britain     

Thomas C. B. Hill  Wendy A. Woodland  Chris D. Spencer  Susan B. Marriott  David J. Case  John A. Catt 《Journal of Paleolimnology》2008,40(1):431-444

The Late-glacial and Holocene environmental history of the Gordano Valley, North Somerset, UK has been reconstructed using pollen, sediment particle size and mineralogical analyses and radiocarbon dating. A Devensian sediment ridge across the valley confined the waters of a small lake, within which the initial sedimentation was minerogenic. Radiocarbon dating of overlying organic-rich deposits suggests that this began late in the Dimlington Stadial c. 18,000–15,000 Cal. BP. Petrographic analyses indicate the minerogenic sediments were partly wind-blown in origin. Climatic amelioration during the Windermere Interstadial c. 15,000 Cal. BP encouraged a shift from minerogenic to biogenic sedimentation. A brief return to minerogenic sedimentation between c. 10,400 and c. 9,520 Cal. BP was followed by uninterrupted fen peat accumulation throughout the Holocene. The later minerogenic horizon appears to represent the Loch Lomond Stadial. Few stratigraphic sequences preserving the complete Devensian Late-glacial–Holocene transition exist in southwest Britain, making the sedimentary archive of the Gordano Valley valuable regionally for reconstructing Late-glacial climate change.  相似文献   

Community cooperation with natural flood management: a case study in the Scottish Borders   总被引：1，自引：0，他引：1  

Olivia Ruth Howgate  Wendy Kenyon 《Area》2009,41(3):329-340

The cooperation of communities and landowners in the upper catchment is vital for the successful implementation of natural flood management (NFM) projects as few incentives are in place to reward them to host such projects. The aim of this paper is to initiate an exploration of the issues that affect a community's decision to cooperate. The results of a case study in Scotland show that willingness to cooperate is affected by concern about alternative flood management techniques, a sense of responsibility to help connected communities at risk of flooding and the expectation of beneficial impacts from the project. Indeed, these issues appeared to over-ride the hostility generated towards the project as a result of poor communication and engagement with the community from organisations associated with the proposed project. The results of the research suggest that if NFM projects are to proliferate, close attention must be paid to community attitudes towards flood management and related communities at risk, and that NFM projects must be developed and implemented according to well-established principles of public participation.  相似文献   

Records of aquatic pollen and sediment properties as indicators of late-Quaternary Alaskan lake levels     

Mary E. Edwards  Nancy H. Bigelow  Bruce P. Finney  Wendy R. Eisner 《Journal of Paleolimnology》2000,24(1):55-68

We investigated whether techniques developed to evaluate qualitative lake-level changes in the temperate zone can be used in sub-arctic and arctic Alaska. We focused on aquatic pollen records and sediment properties (loss-on-ignition and magnetic susceptibility) from centrally-located sediment-surface samples and cores, as these are the most commonly reported data in the literature. Modern aquatic pollen values are generally low (< 5%) and may be zero, even in lakes with abundant aquatic macrophytes. Greater diversity and higher values of aquatic pollen are likely at depths < 5 m, but pollen is found in depths up to 15 m. It is absent at depths > 20 m. Spores of Isoetes and Equisetum and Pediastrum cell-nets, when present, tend to be widely distributed, even in deep water. At Birch Lake, interior Alaska, trends in aquatic taxa and sediment characteristics for the last ca. 12,000 ¹⁴C yrs recorded in a single, deep-water core reflect the same water-level changes as do transect-based lake-level reconstructions - if modern distributional characteristics of pollen and spores are taken into account. The lake rose from extremely low levels at ca. 12,000 ¹⁴C yr B.P. After a period of fluctuation, it rose to a relatively high level by ca. 8000 ¹⁴C yr B.P. and then stabilized. A preliminary survey of aquatic pollen trends from other lake-sediment records suggests that the period ca. 11,000-8000 ¹⁴C yr B.P. may have seen relatively low lake levels in north-western and interior Alaska and high levels thereafter. Changes in aquatic pollen and sediments are evident in north-eastern interior lakes at the same time, but they are more difficult to interpret. Aquatic pollen productivity in Alaskan lakes may partly depend on factors other than water depth (e.g. temperature, pH, nutrient status, or length of the ice-free season). An Alaska-wide reconstruction of late-Quaternary lake levels based on extant single-core data would be best done after further study of contributing factors that may control sediment properties and aquatic pollen distribution.  相似文献   

Formation of CO₂ on a carbonaceous surface: a quantum chemical study     

T. P. M. Goumans  Madeeha A. Uppal  Wendy A. Brown 《Monthly notices of the Royal Astronomical Society》2008,384(3):1158-1164

The formation of CO₂ in the gas phase and on a polyaromatic hydrocarbon surface (coronene) via three possible pathways is investigated with density functional theory. Calculations show that the coronene surface catalyses the formation of CO₂ on model grain surfaces. The addition of ³O to CO is activated by 2530 K in the gas phase. This barrier is lowered by 253 K for the Eley–Rideal mechanism and 952 K for the hot-atom mechanism on the surface of coronene. Alternative pathways for the formation of CO₂ are the addition of ³O to the HCO radical, followed by dissociation of the HCO₂ intermediate. The O + HCO addition is barrierless in the gas phase and on the surface and is more than sufficiently exothermic to subsequently cleave the H–C bond. The third mechanism, OH + CO addition followed by H removal from the energized HOCO intermediate, has a gas-phase exit barrier that is 1160 K lower than the entrance barrier. On the coronene surface, however, both barriers are almost equal. Because the HOCO intermediate can also be stabilized by energy dissipation to the surface, it is anticipated that for the surface reaction the adsorbed HOCO could be a long-lived intermediate. In this case, the stabilized HOCO intermediate could react, in a barrierless manner, with a hydrogen atom to form H₂+ CO₂, HCO₂H, or H₂O + CO.  相似文献   

Concentration, Molecular Weight Distribution and Neutral Sugar Composition of DOC in Maritime Antarctic Lakes of Differing Trophic Status     

Wendy C. Quayle  Peter Convey 《Aquatic Geochemistry》2006,12(2):161-178

The molecular weight distributions and hydrolysable neutral sugar composition of dissolved organic carbon (DOC) was investigated in four maritime Antarctic lakes on Signy Island of different trophic status; Heywood Lake (eutrophic), Light Lake (oligo-mesotrophic), Sombre Lake and Moss Lake (both oligotrophic). Tangential flow ultra-filtration (TFU) was used to separate DOC into high molecular weight (HMW; >1000 Da) and low molecular weight (LMW; < 1000 Da) size fractions. Pulsed amperometric detection-high performance liquid chromatography (PAD-HPLC) was used to determine the hydrolysable neutral sugar molecular composition of each size fraction. Total DOC concentrations defined the trophic trend in the four lakes and ranged from 8 to 303 μM. The <1000 Da fraction of all the lakes dominated the DOC distribution, comprising 76% in Light Lake which also had the highest chl-a concentrations. Heywood Lake was relatively enriched in >1000 Da total organic carbon and had extremely high concentrations of total hydrolysable neutral sugars (11 μM) corresponding to 43% of total DOC. However, no clear pattern was apparent with regard to lake trophic status and potential sources of DOC, and the measured variations in individual aldose concentration, composition and their various molecular weight fractions.  相似文献   

Future changes of temperature and heat waves in Ontario,Canada     

Li  Zhong  Huang  Guohe  Huang  Wendy  Lin  Qianguo  Liao  Renfei  Fan  Yurui 《Theoretical and Applied Climatology》2018,132(3-4):1029-1038

Theoretical and Applied Climatology - Apparent changes in the temperature patterns in recent years brought many challenges to the province of Ontario, Canada. As the need for adapting to climate...  相似文献   

Improved hydrograph prediction through subsurface characterization: conditional stochastic hillslope simulations     

Steven B. Meyerhoff  Reed M. Maxwell  Wendy D. Graham  John L. Williams III 《Hydrogeology Journal》2014,22(6):1329-1343

Subsurface heterogeneity is one of the largest sources of uncertainty associated with saturated hydraulic conductivity. Recent work has demonstrated that uncertainty in hydraulic conductivity can impart significant uncertainty in runoff generation processes and surface-water flow. Here, the role of site characterization in reducing hydrograph prediction bias and uncertainty is demonstrated. A fully integrated hydrologic model is used to conduct two sets of stochastic, transient simulation experiments comprising different overland flow mechanisms: Dunne and Hortonian. Conditioning hydraulic conductivity fields using values drawn from a simulated synthetic control case are shown to reduce both mean bias and variance in an ensemble of conditional hydrograph predictions when compared with the control case. The ensemble simulations show a greater reduction in uncertainty in the hydrographs for Hortonian flow. The conditional simulations predict surface ponding and surface pressure distributions with reduced mean error and reduced root mean square error compared with unconditional simulations. Uncertainty reduction in Hortonian and Dunne flow cases demonstrates different temporal signals, with more substantial reduction achieved for Hortonian flow.  相似文献