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101.
High‐frequency water quality monitoring in an urban catchment: hydrochemical dynamics,primary production and implications for the Water Framework Directive 下载免费PDF全文
Sarah J. Halliday Richard A. Skeffington Andrew J. Wade Michael J. Bowes Emma Gozzard Jonathan R. Newman Matthew Loewenthal Elizabeth J. Palmer‐Felgate Helen P. Jarvie 《水文研究》2015,29(15):3388-3407
This paper describes the hydrochemistry of a lowland, urbanised river‐system, The Cut in England, using in situ sub‐daily sampling. The Cut receives effluent discharges from four major sewage treatment works serving around 190 000 people. These discharges consist largely of treated water, originally abstracted from the River Thames and returned via the water supply network, substantially increasing the natural flow. The hourly water quality data were supplemented by weekly manual sampling with laboratory analysis to check the hourly data and measure further determinands. Mean phosphorus and nitrate concentrations were very high, breaching standards set by EU legislation. Although 56% of the catchment area is agricultural, the hydrochemical dynamics were significantly impacted by effluent discharges which accounted for approximately 50% of the annual P catchment input loads and, on average, 59% of river flow at the monitoring point. Diurnal dissolved oxygen data demonstrated high in‐stream productivity. From a comparison of high frequency and conventional monitoring data, it is inferred that much of the primary production was dominated by benthic algae, largely diatoms. Despite the high productivity and nutrient concentrations, the river water did not become anoxic, and major phytoplankton blooms were not observed. The strong diurnal and annual variation observed showed that assessments of water quality made under the Water Framework Directive (WFD) are sensitive to the time and season of sampling. It is recommended that specific sampling time windows be specified for each determinand, and that WFD targets should be applied in combination to help identify periods of greatest ecological risk. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. 相似文献
102.
Fiona?Elizabeth?Mothersole Katy?EvansEmail authorView authors OrcID profile B.?Ronald?Frost 《Contributions to Mineralogy and Petrology》2017,172(8):69
Subduction of serpentinised mantle transfers oxidised and hydrated mantle lithosphere into the Earth, with consequences for the oxidation state of sub-arc mantle and the genesis of arc-related ore deposits. The role of subducted serpentinised mantle lithosphere in earth system processes is uncertain because subduction fluxes are poorly constrained. Most subducted serpentinised mantle is serpentinised on the ocean floor settings. Yet this material is poorly represented in the literature because it is difficult to access. Large volumes of accessible serpentinite are available in ophiolite complexes, and most interpretations of subduction fluxes associated with ultramafic rocks are based on ophiolite studies. Seafloor and ophiolite serpentinisation can occur under different conditions, so it is necessary to assess if ophiolite serpentinites are a good proxy for seafloor serpentinites. Serpentinites sampled during ODP cruise 209 were compared with serpentinites from New Caledonia. The ODP209 serpentinites were serpentinised by modified seawater in a shallow hydrothermal seafloor setting. The New Caledonia serpentinites were serpentinised in a mantle wedge setting by slab-derived fluids, with possible contributions from oceanic serpentinisation and post-obduction serpentinisation. Petrological, whole rock and mineralogical analyses were combined to compare the two sample sets. Petrologically, the evolution of serpentinisation was close to identical in the two environments. However, more oxidised iron, Cl, S and C is present in serpentine from the ODP209 serpentinites relative to the New Caledonia serpentinites. Given these observations, the use of serpentinites from different geodynamic settings as a proxy for abyssal serpentinites from spreading settings must be undertaken with caution. 相似文献
103.
Elizabeth Cottrell Michael J. Walter David Walker 《Earth and Planetary Science Letters》2010,289(3-4):631-634
104.
Jianping Huang Elizabeth Vanacore Fenglin Niu Alan Levander 《Earth and Planetary Science Letters》2010,289(1-2):105-111
We analyzed receiver-function data recorded by a temporary broadband array deployed as part of the BOLIVAR project and the permanent seismic network of Venezuela to study the mantle transition zone structure beneath the Caribbean-South American plate boundary and Venezuela. Significant topography on both the 410-km and the 660-km discontinuities was clearly imaged in the CCP (common-conversion-point) stacked images. Beneath the southeastern Caribbean, the 410-km is featured by a narrow (~ 200 km EW) ~ 25-km uplift extending in the NS direction around 63° west, while the 660-km is depressed by ~ 20 km in a narrow region slightly west to the uplift, a scenario that is more consistent with westward descent of the oceanic South American plate rather than a break-off of NNW dipping proto-Caribbean oceanic lithosphere along the El Pilar Fault. We also found a thick transition zone beneath the Falcon region in northwestern Venezuela, possibly associated with the subducted Nazca plate. A flat 410-km was observed beneath the Guayana shield, suggesting that the shield has a stable and moderately deep keel, which has little effect on the underlying transition zone structure. 相似文献
105.
Elizabeth A. Masden Daniel T. Haydon Robert W. Furness 《Marine pollution bulletin》2010,60(7):1085-1091
Proposals for wind farms in areas of known importance for breeding seabirds highlight the need to understand the impacts of these structures. Using an energetic modelling approach, we examine the effects of wind farms as barriers to movement on seabirds of differing morphology. Additional costs, expressed in relation to typical daily energetic expenditures, were highest per unit flight for seabirds with high wing loadings, such as cormorants. Taking species-specific differences into account, costs were relatively higher in terns, due to the high daily frequency of foraging flights. For all species, costs of extra flight to avoid a wind farm appear much less than those imposed by low food abundance or adverse weather, although such costs will be additive to these. We conclude that adopting a species-specific approach is essential when assessing the impacts of wind farms on breeding seabird populations, to fully anticipate the effects of avoidance flights. 相似文献
106.
Katharine A. Smith Elizabeth W. North Fengyan Shi Shih-Nan Chen Raleigh R. Hood Evamaria W. Koch Roger I. E. Newell 《Estuaries and Coasts》2009,32(4):748-757
Seagrass beds have declined in Chesapeake Bay, USA as well as worldwide over the past century. Increased seston concentrations,
which decrease light penetration, are likely one of the main causes of the decline in Chesapeake Bay. It has been hypothesized
that dense populations of suspension-feeding bivalves, such as eastern oysters (Crassostrea virginica), may filter sufficient seston from the water to reduce light attenuation and enhance seagrass growth. Furthermore, eastern
oyster populations can form large three-dimensional reef-like structures that may act like breakwaters by attenuating waves,
thus decreasing sediment resuspension. We developed a quasi-three-dimensional Seagrass-Waves-Oysters-Light-Seston (SWOLS)
model to investigate whether oyster reefs and breakwaters could improve seagrass growth by reducing seston concentrations.
Seagrass growth potential (SGP), a parameter controlled by resuspension-induced turbidity, was calculated in simulations in
which wave height, oyster abundance, and reef/breakwater configuration were varied. Wave height was the dominant factor influencing
SGP, with higher waves increasing sediment resuspension and decreasing SGP. Submerged breakwaters parallel with the shoreline
improved SGP in the presence of 0.2 and 0.4 m waves when sediment resuspension was dominated by wave action, while submerged
groins perpendicular to the shoreline improved SGP under lower wave heights (0.05 and 0.1 m) when resuspension was dominated
by along-shore tidal currents. Oyster-feeding activity did not affect SGP, due to the oysters’ distance from the seagrass
bed and reduced oyster filtration rates under either low or high sediment concentrations. Although the current implementation
of the SWOLS model has simplified geometry, the model does demonstrate that the interaction between oyster filtration and
along-shore circulation, and between man-made structures and wave heights, should be considered when managing seagrass habitats,
planning seagrass restoration projects, and choosing the most suitable methods to protect shorelines from erosion. 相似文献
107.
Megan J. Macdonald Elizabeth C. Minor 《Aquatic Sciences - Research Across Boundaries》2013,75(4):509-522
The input and fate of dissolved organic matter (DOM) can have important consequences for coastal zone productivity in large lakes and oceans. Chromophoric DOM (CDOM) is often delivered to coastal zones from rivers and streams and affects light penetration in a water column. CDOM can protect biota from damaging ultraviolet (UV) light by acting as sunscreen, resulting in increased ecosystem productivity. Alternatively, CDOM can decrease ecosystem productivity by absorbing light needed for photosynthesis and forming photoreaction products that are harmful to coastal zone biota. Increased urbanization of watersheds and seasonal differences in weather patterns change the delivery pathways, reactivity, input, and energy flow of DOM (and its CDOM component) into aquatic systems. This study investigated the effects of watershed and season on the concentrations and potential photodegradation of stream-derived DOM in Lake Superior tributaries, chosen to be geographically and geologically similar but differing in land use. Organic carbon analysis, UV–Visible spectrophotometry, and terrestrial (land use) analysis were used to investigate differences among samples and sample treatments. The major differences in DOM concentration and photochemical response appeared seasonal rather than site specific, with snow-melt samples showing stronger and more consistent changes in UV–Visible parameters while base-flow samples showed stronger and more consistent losses in DOC. 相似文献
108.
Julia M. Ribeiro Robert J. Stern Fernando Martinez Osamu Ishizuka Susan G. Merle Katherine Kelley Elizabeth Y. Anthony Minghua Ren Yasuhiko Ohara Mark Reagan Guillaume Girard Sherman Bloomer 《Island Arc》2013,22(4):453-476
The southernmost Mariana forearc stretched to accommodate opening of the Mariana Trough backarc basin in late Neogene time, erupting basalts at 3.7–2.7 Ma that are now exposed in the Southeast Mariana Forearc Rift (SEMFR). Today, SEMFR is a broad zone of extension that formed on hydrated, forearc lithosphere and overlies the shallow subducting slab (slab depth ≤ 30–50 km). It comprises NW–SE trending subparallel deeps, 3–16 km wide, that can be traced ≥ ∼30 km from the trench almost to the backarc spreading center, the Malaguana‐Gadao Ridge (MGR). While forearcs are usually underlain by serpentinized harzburgites too cold to melt, SEMFR crust is mostly composed of Pliocene, low‐K basaltic to basaltic andesite lavas that are compositionally similar to arc lavas and backarc basin (BAB) lavas, and thus defines a forearc region that recently witnessed abundant igneous activity in the form of seafloor spreading. SEMFR igneous rocks have low Na8, Ti8, and Fe8, consistent with extensive melting, at ∼23 ± 6.6 km depth and 1239 ± 40°C, by adiabatic decompression of depleted asthenospheric mantle metasomatized by slab‐derived fluids. Stretching of pre‐existing forearc lithosphere allowed BAB‐like mantle to flow along the SEMFR and melt, forming new oceanic crust. Melts interacted with pre‐existing forearc lithosphere during ascent. The SEMFR is no longer magmatically active and post‐magmatic tectonic activity dominates the rift. 相似文献
109.
Elizabeth S. Garcia 《水文科学杂志》2013,58(1):204-220
AbstractThis work presents a method for calculating the contributions of sea-level rise and urban growth to flood risk in coastal flood plains. The method consists of hydraulic/hydrological, urban growth and flood-damage quantification modules. The hydraulic/hydrological module estimates peak annual flows to generate flood stages impacted by sea-level rise within flood plains. A model for urban growth predicts patterns of urbanization within flood plains over the period 2010–2050. The flood-damage quantification module merges flood maps and urbanization predictions to calculate the expected annual flood damage (EAFD) for given scenarios of sea-level rise. The method is illustrated with an application to the Tijuana River of southern California, USA, and northwestern Mexico, where the EAFD is predicted to increase by over US$100 million because of sea-level rise of 0.25–1.0 m and urban growth by the year 2050. It is shown that urbanization plays a principal role in increasing the EAFD in the study area for the range of sea-level rise considered.Editor Z.W. KundzewiczCitation Garcia, E.S. and Loáiciga, H.A., 2013. Sea-level rise and flooding in coastal riverine flood plains. Hydrological Sciences Journal, 59 (1), 204–220. 相似文献
110.
Elizabeth Holcombe Sarah Smith Edmund Wright Malcolm G. Anderson 《Natural Hazards》2012,61(2):351-385
Despite the recognition of the need for mitigation approaches to landslide risk in developing countries, the delivery of ‘on-the-ground’
measures is rarely undertaken. With respect to other ‘natural’ hazards, it is widely reported that mitigation can pay. However,
the lack of such an evidence base in relation to landslides in developing countries hinders advocacy amongst decision makers
for expenditure on ex-ante measures. This research addresses these limitations directly by developing and applying an integrated
risk assessment and cost–benefit analysis of physical landslide mitigation measures implemented in an unplanned community
in the Eastern Caribbean. In order to quantify the level of landslide risk reduction achieved, landslide hazard and vulnerability
were modelled (before and after the intervention), and project costs, direct and indirect benefits were monetised. It is shown
that the probability of landslide occurrence has been substantially reduced by implementing surface-water drainage measures
and that the benefits of the project outweigh the costs by a ratio of 2.7–1. This paper adds to the evidence base that ‘mitigation
pays’ with respect to landslide risk in the most vulnerable communities—thus strengthening the argument for ex-ante measures.
This integrated project evaluation methodology should be suitable for adoption as part of the community-based landslide mitigation
project cycle, and it is hoped that this resource, and the results of this study, will stimulate further such programmes. 相似文献