气相色谱测定沉积物中多氯联苯的样品处理方法研究   总被引：1，自引：0，他引：1  

宋喜红  宋吉德  张学超  李晓敏 《海洋科学》2010,34(2):40-44

通过比较密闭微波萃取、超声波萃取、索氏提取3种方法对沉积物中多氯联苯(PCBs)提取效率,对比浓硫酸和Florisil小柱两种净化方式的净化效果,在实验基础上建立了密闭微波萃取-Florisil小柱净化-气相色谱(ECD)测定沉积物中多氯联苯的分析方法,加标质量比为0.2ng/g时,其相对标准偏差(RSD)为2.19%～8.71%,回收率为77.3%～94.6%,检出限为0.027～0.064ng/g。采用该方法对威海湾养殖区沉积物中PCBs进行了监测,结果表明本方法适用于海洋沉积物样品中PCBs的测定。  相似文献   

Practice versus policy-led coastal defence management     

M.C. O&#x;Connor  G. Lymbery  J.A.G. Cooper  J. Gault  J. McKenna 《Marine Policy》2009,33(6):923

Throughout northwest European coastal countries risks associated with coastal erosion are significant but spatially and temporally variable. The level of this risk is largely dependent on the extent of development within the coastal zones and a variety of approaches have been adopted for its management. The decision-making process for responding to erosion risk depends to a large extent on national policy. Coastal protection policy in northwest European countries varies in terms of the level of centralisation and formality of arrangements. In this paper the practical outworking of the informal practice-based system of Ireland, where there is no national policy framework, is compared with the policy-led system of England and Wales where formal national guidelines exist. Using case studies, the strengths and weaknesses of both the bottom-up and top-down approaches are assessed. The findings reveal strengths and weaknesses in both existing types of approach.  相似文献   

The use of video imagery to analyse groundwater and shoreline dynamics on a dissipative beach     

Christien E. Huisman  Karin R. BryanGiovanni Coco  B.G. Ruessink 《Continental Shelf Research》2011,31(16):1728-1738

Groundwater seepage is known to influence beach erosion and accretion processes. However, field measurements of the variation of the groundwater seepage line (GWSL) and the vertical elevation difference between the GWSL and the shoreline are limited. We developed a methodology to extract the temporal variability of the shoreline and the wet-dry boundary using video imagery, with the overarching aim to examine elevation differences between the wet-dry boundary and the shoreline position in relation to rainfall and wave characteristics, during a tidal cycle. The wet-dry boundary was detected from 10 min time-averaged images collected at Ngaranui Beach, Raglan, New Zealand. An algorithm discriminated between the dry and wet cells using a threshold related to the maximum of the red, green, and blue intensities in Hue-Saturation-Value. Field measurements showed this corresponded to the location where the water table was within 2 cm of the beachface surface. Time stacks and time series of pixels extracted from cross-shore transects in the video imagery, were used to determine the location of the shoreline by manually digitizing the maximum run-up and minimum run-down location for each swash cycle, and averaging the result. In our test data set of 14 days covering a range of wave and rainfall conditions, we found 6 days when the elevation difference between the wet-dry boundary and the shoreline remained approximately constant during the tidal cycle. For these days, the wet-dry boundary corresponded to the upper limit of the swash zone. On the other 8 days, the wet-dry boundary and the shoreline decoupled with falling tide, leading to elevation differences of up to 2.5 m at low tide. Elevation differences between the GWSL and the shoreline at low tide were particularly large when the cumulative rainfall in the preceding month was greater than 200 mm. This research shows that the wet-dry boundary (such as often used in video shoreline-finding algorithms) is related to groundwater seepage on low-sloped, medium to fine sand beaches such as Ngaranui Beach (mean grain size ∼0.27 mm, beach slope ∼1:70) and may not be a good indicator of the position of the shoreline.  相似文献   

Age constraints on the late Quaternary evolution of Qinghai Lake, Tibetan Plateau   总被引：9，自引：0，他引：9  

David B. Madsen  Ma Haizhou  P. Jeffrey Brantingham 《Quaternary Research》2008,69(2):316-325

Dating and geomorphology of shoreline features in the Qinghai Lake basin of northwestern China suggest that, contrary to previous interpretations, the lake likely did not reach levels 66-140 m above modern within the past ∼ 90,000 yr. Maximum highstands of ∼ 20-66 m above modern probably date to Marine Isotope Stage (MIS) 5. MIS 3 highstands are undated and uncertain but may have been at or below post-glacial highs. The lake probably reached ∼ 3202-3206 m (+ 8-12 m) during the early Holocene but stayed below ∼ 3202 m after ∼ 8.4 ka. This shoreline history implies significantly different hydrologic balances in the Qinghai Lake basin before ∼ 90 ka and after ∼ 45 ka, possibly the result of a more expansive Asian monsoon in MIS 5.  相似文献   

Depo sequence as tool to convert shoreline trajectory from space domain to time domain     

《Marine and Petroleum Geology》2016

Deposystems are complex and governed by discrete depo events with variable intervals of stasis or erosion in between. Since shoreface sediments indicate sea level, depo events of shoreline facies are discrete samples of sea level. Only if these samples are sufficiently regular and frequent will the shoreline trajectory in the space domain accurately reflect the sea-level curve in the time domain. This study presents a method to convert shoreline trajectory in the space domain to sea-level curve in the time domain from artificial miniature deltas. One obtains the depo sequence as function of time and uses it to: convert depo sequence from time-to space domain, correlate depo sequence to shoreline trajectory in the space domain, and convert shoreline trajectory from space-to time domain. For natural deltas one would extract the depo set in the frequency domain, i.e. the probability density function of stasis intervals between depo events from the experimental depo sequence and use it to: convert shoreline trajectory from space-to time domain, and infer a range of possible sea-level curves. This method therewith explicitly includes the uncertainty of the inferred sea-level curve.  相似文献   

Sediment transport analysis as a component of coastal management— a UK example   总被引：1，自引：0，他引：1  

J. M. Hooke  M. J. Bray  D. J. Carter 《Environmental Geology》1996,27(4):347-357

Detrimental effects of engineering works on the coast and a wish to conserve parts of the coastline have increased realization among coastal managers of the need to examine shoreline problems and proposals for protection in a wider spatial context than the site itself and over a longer time scale than the past few years. This paper outlines the approach taken in one region of the United Kingdom, the central south coast of England, to provide that wider perspective. Authorities responsible for coastal protection and sea defenses formed a coastal group, which, among other activities, commissioned research aimed at providing a greater understanding on which to base shoreline management decisions. A major project undertaken was a sediment transport study in which all existing information relating to coastal sediment processes in the region was collated and analyzed. All inputs, flows, and outputs of sediment were documented. Links between processes were examined for each part of the region. Finally, nine littoral cells of sediment circulation were identified and were suggested as forming a framework for shoreline management. The methods of compilation and analysis are outlined here and are exemplified for one area in the region. The approach is recommended as a cost-effective basis for strategic management of the coast in developed regions.  相似文献   

Application of one-line model to the prediction of shoreline change     

Qin Chongren  He Jiangcheng 《海洋学报(英文版)》1997,16(3):403-417

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ERS-1 modulation transfer function impact on shoreline change model     

Maged Marghany   《International Journal of Applied Earth Observation and Geoinformation》2003,4(4):279-294

The impact of wave spectra modulation transfer function (MTF) in shoreline change model accuracy has been presented. The MTF consisted of real aperture radar (RAR) and velocity-bunching which is utilized to map the wave spectra observed from ERS-1 into the observed real ocean wave spectra. Based on this information, the shoreline change model have developed. Two hypotheses were concerned with the shoreline change model based on ERS-1 wave spectra. First, there is a significant difference between RAR and velocity-bunching modulations for ERS-1 wave spectra modeling. Second, this significant difference is induced a different spatial variation for shoreline change pattern.This study shows that there was the significant difference between velocity-bunching and quasi-linear models. The study shows that velocity-bunching model produces wave spectra pattern approximately close to the real ocean wave compared to the quasi-linear model. The error percentage occurred with velocity-bunching and quasi-linear models were 33.5 and 46.7%, respectively. The highest rate of erosion occurred to the shore south of Chendering with −5 m per year and the highest rate of sedimentation occurred to north of Chendering headland with 3 m per year. It can be concluded that ERS-1 data could be used to model shoreline change and identify the locations of erosion and sedimentation. The sedimentation was occurred due to the effect of lowest wave spectra energy captured along the range direction while the erosion was occurred due to highest spectra energy captured near azimuth direction.  相似文献   

An Analytical Slab Model for the Growth of the Coastal Thermal Internal Boundary Layer Under Near-Neutral Onshore Flow Conditions     

Ashok K. Luhar 《Boundary-Layer Meteorology》1998,88(1):103-120

Analytical parameterisations of the thermal internal boundary-layer (TIBL) height based on the slab approach are widely used in coastal dispersion models. However, they tend to a singular behaviour when the stability of the onshore flow is close to neutral. Assuming that convective turbulence dominates mixing, we derive a more general analytical model that is valid for both stable and neutral onshore flows. The model is based on the existing framework for the slab approach but involving the Zilitinkevich correction (or the spin-up term). The height variation of the onshore flow lapse rate is accounted for in the model by including an initial TIBL height. An algebraic form of the model also includes the mechanical mixing contribution to the TIBL growth and is, therefore, suitable for use when the overland surface heat flux is small and friction velocity large. The new analytical model is tested with field measurements taken under near-neutral onshore flow conditions. The performance of the model is shown to be better than a commonly used TIBL parameterisation scheme.  相似文献   

The stratigraphy of flandrian relative sea-level changes at a site in tayside,Scotland     

D. E. Smith  A. G. Dawson  R. A. Culungford  D. D. Harkness 《地球表面变化过程与地形》1985,10(1):17-25

Peat deposits in a gully at the inland margin of the Firth of Tay carselands contain a transgressive wedge of estuarine sediments laid down at the culmination of the Main Postglacial Transgression. In previous work, the sequence of deposits in the gully and their age have been examined at one location. The present study both extends and evaluates that previous work, employing further field work and laboratory analyses. The detailed stratigraphy of the deposits is identified, whilst from a borehole close to the limit of the transgressive deposit, diatom analysis and geochemical analyses, involving the determination of Al, Mg, C, and δ ¹³C_PDB are outlined. Eight ¹⁴C assays from peat at the transgressive and regressive contacts in four boreholes along the wedge of estuarine sediments are described. Whilst the results of diatom analysis are inconclusive, the geochemical analyses indicate that the sediment accumulated broadly continuously without major changes in the depositional environment. It is concluded that the Main Postglacial Transgression in the gully was at first rapid, then slowed and culminated between 6240 ± 80 and 6030 ± 80 (or 6170 ± 90) radiocarbon years, B.P. It is subsequently maintained that the geochemical analyses described here may be of value in determining the continuity of transgressive deposits, whilst the practice of obtaining multiple radiocarbon assays at such locations should enable assessment of age to be refined. This may in turn assist in testing the hypothesis of shoreline diachroneity in glacioisostatically affected areas.  相似文献