苏北浅滩沉积物中的大型绿藻微观繁殖体的垂直分布和物种多样性   总被引：1，自引：0，他引：1  

刘峰  刘兴凤  金柘  于仁成  孔凡洲  颜天 《海洋与湖沼》2018,49(5):983-990

本研究通过在2017年秋冬季组织实施的2个绿潮种源调查航次,研究苏北浅滩紫菜养殖区沉积物中的大型绿藻微观繁殖体的垂直分布和物种多样性。对沉积物中的微观繁殖体的定量实验结果表明:表层泥样中绿藻微观繁殖体的丰度最高,随着深度的增加迅速降低。在9月份表层沉积物中丰度为9±2ind./g,而在11月份表层丰度达到98±25ind./g;与9月份相比, 11月份浅滩沉积物中绿藻繁殖体数量呈现出显著升高的趋势。通过对51个绿藻样品的分子鉴定发现:沉积物中存在石莼属(Ulva)、尾孢藻属(Urospora)、盘苔属(Blidingia)等大型绿藻的微观繁殖体;数量占优是石莼属繁殖体,主要包括曲浒苔(Ulva flexuosa)、浒苔(Ulva prolifera)、扁浒苔(Ulva compressa)、缘管浒苔(Ulva linza);其中曲浒苔占据的比例最高,在9和11月份分别达到80.94%和73.33%。在2个调查航次中,都从沉积物中发现了绿潮浒苔的微观繁殖体,这些微观繁殖体是绿潮浒苔在苏北浅滩种源维持的重要方式和关键阶段,也构成了黄海浒苔绿潮连年暴发的"种子库"。  相似文献   

Fishing industry and related perspectives on the issues raised by no-take marine protected area proposals   总被引：2，自引：2，他引：0  

P.J.S. Jones   《Marine Policy》2008,32(4):749-758

In the face of growing calls for no-take marine protected areas (NTMPAs), the views of fishing industry representatives in south-west (SW) England on related issues are analysed. Only 23% thought NTMPAs were the way forward and a range of concerns were expressed, e.g. that the ‘terrestrial’ protected areas approach and related biodiversity conservation objectives will be extended to the seas, and that fish yield reductions from the loss of access to NTMPAs are very unlikely to be compensated for through spillover/export. Some interesting approaches to ameliorating these concerns emerged, such as being open and honest that NTMPAs are primarily intended to achieve biodiversity conservation benefits, reducing uncertainty concerning the potential for any secondary fisheries spillover/export benefits, justifying NTMPAs on an objective, rational basis rather than on a subjective, precautionary basis, and the quid pro quo streamlining of wider fisheries management approaches. This research reveals a more diverse range of perspectives amongst fishing industry representatives on the issues raised by NTMPA proposals than is often assumed.  相似文献   

The mitigation of the vibration effects caused by tunnel blasts in urban areas: a case study in Istanbul     

Cengiz Kuzu 《Environmental Geology》2008,54(5):1075-1080

Ground vibrations generated by commercial explosives in tunnel construction may cause structural damage in urban areas. Therefore, suppressing the vibration effects and mitigating the possible hazard after blasting is important. We present a new method of controlled blasting that is environmentally friendly, and easy to utilize for tunnel construction. Small charges in this method are detonated sequentially to produce minimum side effects. The efficiency of the charges may be increased based on the previously monitored shots. This method is utilized in a tunnel construction in Istanbul with five experimental shots. In these experiments, the duration and also the quantity of explosives were carefully controlled. We were able to obtain better results with short durations (480 ms) instead of long durations (9,000 ms) although the vibration levels defined as peak particle velocity (PPV) became bigger while the quantity of the explosive charge increased from 3.088 to 9.264 kg.  相似文献   

Damage to surface structures due to underground coal mine blasting: apprehension or real cause?     

P. K. Singh  M. P. Roy 《Environmental Geology》2008,53(6):1201-1211

Investigations were carried out at three underground coal mines in India to study the response of surface structures to underground blasting and the likelihood of damage to the structures. The structures in the vicinity of the underground blasting area were single and multistoried residential houses. The amplitudes of vibration due to underground blasting were monitored simultaneously on the ground surface near the foundation of the structures and on various floors of the structures. The vibrations were also monitored near the important surface installations. It was observed that the magnitude of vibration in structures decreased with the increase in the height of the structures. The frequency of blast vibration from underground blasting was higher than the natural frequency of the structures. Little energy was transmitted into the structures, which caused reduction in the vibration level in the structures. The reduction in the vibration levels was up to 45% in the houses. It indicates that the dominant frequency of blast vibration plays an important role in persistence of vibration and its amplification or reduction characteristics in the structures. This paper deals with the effect of the vibrations on structures/houses standing above the blasting faces in underground workings and their potential to likely damage to the structures at different Indian geo-mining conditions.  相似文献   

A modified DRASTIC model for Siting Confined Animal Feeding Operations in Williams County,Ohio, USA   总被引：1，自引：0，他引：1  

Enrique Gomezdelcampo  J. Ryan Dickerson 《Environmental Geology》2008,55(8):1821-1832

Three of DRASTIC’s parameters (Depth to Water, Soil Media, and Topography) were modified and another parameter was added (land use/land cover) to the model to determine the potential impact on groundwater from Confined Animal Feeding Operations (CAFO) manure lagoon settings and manure application as fertilizer. Williams County is a mostly agricultural county located in northwest Ohio, USA. It currently has three CAFOs, all dairy, with the possibility of the construction of a multi-million chicken egg CAFO in the near future. A Geographic Information System (GIS) was utilized to modify the Ohio Department of Natural Resources (ODNR) DRASTIC map for the county to fully assess the county-wide pollution potential of CAFOs. The CAFO DRASTIC map indicates that almost half of Williams County has elevated groundwater pollution potential. The rest of the county, primarily the southeast corner, has lower CAFO groundwater pollution potential. Future CAFO development within the county should focus on the southeastern portion of the county where the groundwater table is deeper, and the aquifer is composed of shale substrate with low hydraulic conductivity. The CAFO DRASTIC results are intended to be used as a screening tool and are not to replace site-specific hydrogeologic investigations.  相似文献   

Potential for localized groundwater contamination in a porous pavement parking lot setting in Rhode Island     

Thomas B. Boving  Mark H. Stolt  Janelle Augenstern  Brian Brosnan 《Environmental Geology》2008,55(3):571-582

The control of polluted surface runoff and the assessment of possible impacts on groundwater is a concern at the local and regional scale. On this background, a study investigates possible impacts of organic and inorganic pollutants (including bacteria) originating from a permeable asphalt parking lot on the water quality immediately beneath it. The functioning of the permeable pavement, including clogging and restricted vertical percolation, was also evaluated. Four nested sample ports (shallow and deep) were installed below low- and high-traffic areas, including one port outside the parking lot. At least initially there was a good hydraulic connection between the parking surface and the shallow sample ports. The presence of a geotextile layer at the base of the parking lot structure, however, was identified in lab tests as one factor restricting vertical percolation to the deeper ports. Clogging of the permeable surface was most pronounced in heavy traffic areas and below snow pile storage areas. Corroborated by high electric conductivity and chloride measurements, sand brought in by cars during winter was the principal cause for clogging. No bacteria or BOD were found in percolating water. Polycyclic aromatic hydrocarbons (PAH) were present at concentrations near minimum detection limit. Nutrients (nitrate and phosphate) were being leached into the ground via the permeable parking lot surface at annual flux rates of 0.45–0.84 g/m²/year. A multi-species tracer test demonstrated a retention capacity of the permeable parking lot structure of >90% for metals and 27% for nutrients, respectively.  相似文献   

Enhancing understanding of breakdown and collapse in the Yorkshire Dales using ground penetrating radar on cave sediments     

P. Murphy  A.R. Westerman  R. Clark  A. Booth  A. Parr 《Engineering Geology》2008,99(3-4):160

Historical evidence shows block breakdown and collapse are actively occurring in large fault aligned caverns in the Yorkshire Dales karst. Deployment of ground penetrating radar at two such sites has provided detailed images of the sedimentary sequences below the present day cavern floor but no large blocks are imaged within the sediments. Solutional processes must be removing limestone from the sediment to allow continued cavern growth. Possible mechanisms to account for the lack of large blocks within the sediment fill are discussed.  相似文献   

Nonlinear Analysis of Local Site Effects on Seismic Ground Response in the Bam Earthquake   总被引：1，自引：0，他引：1  

M. H. T. Rayhani  M. H. El Naggar  S. H. Tabatabaei 《Geotechnical and Geological Engineering》2008,26(1):91-100

The influence of local geologic and soil conditions on the intensity of ground shaking is addressed in this study. The amplification of the ground motion due to local site effects resulted in severe damage to dwellings in the Bam area during the 2003 Bam Earthquake. A unique set of strong motion acceleration recordings was obtained at the Bam accelerograph station. Although the highest peak ground acceleration recorded was the vertical component (nearly 1 g), the longitudinal component (fault-parallel motion) clearly had the largest maximum velocity as well as maximum ground displacement. Subsurface geotechnical and geophysical (down-hole) data in two different sites have been obtained and used to estimate the local site condition on earthquake ground motion in the area. The ground response analyses have been conducted considering the nonlinear behavior of the soil deposits using both equivalent linear and nonlinear approaches. The fully nonlinear method embodied in FLAC was used to evaluate the nonlinear soil properties on earthquake wave propagation through the soil layer, and compare with the response from the equivalent linear approach. It is shown that thick alluvium deposits amplified the ground motion and resulted in significant damage in residential buildings in the earthquake stricken region. The comparison of results indicated similar response spectra of the motions for both equivalent and nonlinear analyses, showing peaks in the period range of 0.3–1.5 s. However, the amplification levels of nonlinear analysis were less than the equivalent linear method especially in long periods. The observed response spectra are shown to be above the NEHRP building code design requirements, especially at high frequencies.  相似文献   

Effect of Inter-Column Spacing on Soil Stresses due to Vibro-Installed Stone Columns: Interesting Findings   总被引：1，自引：0，他引：1  

Hesham Elshazly  Mohamed Elkasabgy  Azza Elleboudy 《Geotechnical and Geological Engineering》2008,26(2):225-236

This paper reveals the interesting relation between the inter-column spacing and the corresponding alteration of soil state of stresses due to the vibro-installation technique. This relation is inferred from analyses for load settlement records of various field load tests, performed for stone columns arrangements with different inter-column spacing values. In order to have adequate confidence in the findings, a well-documented case history, involving three columns patterns along with their relevant field and laboratory test results, is utilized for this study. Moreover, a well-tested finite element model, capable of simulating both elasto-plastic and time dependent soil deformations as well as pore water pressure building and dissipation, is employed in the analysis. Instead of determining the soil response to the test load, based on known initial soil stresses and material properties, the analysis is inversely posed to determine the soil initial stresses, based on the recorded settlements and the post-installation material properties. The alteration in the soil state of stress is represented by the increase in the post-installation horizontal to vertical stress ratio, K*, as a function of the inter-column spacing. It is found that this alteration experiences a systematic decrease in its magnitude as the inter-column spacing increases.  相似文献   

Efficiency analysis of open trench for impact pile driving through a single-variable method     

Amir Hamidi  Abtin Farshi Homayoun Rooz 《Marine Georesources & Geotechnology》2021,39(1):82-102

Abstract

The ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design.  相似文献