Distribution,potential sources and ecological risks of two persistent organic pollutants in the intertidal sediment at the Shuangtaizi Estuary,Bohai Sea of China     

Xiutang Yuan  Xiaolong Yang  Anguo Zhang  Xindong Ma  Hui Gao  Guangshui Na  Humin Zong  Guize Liu  Yongguang Sun 《Marine pollution bulletin》2017,114(1):419-427

Spatial distribution, source apportionment, and potential ecological risks of sixteen polycyclic aromatic hydrocarbons (PAHs) and seven endocrine disrupting compounds (EDCs) in the intertidal sediment at the Shuangtaizi Estuary, Bohai Sea of China were analyzed. Results showed that the total PAH concentrations ranged from 28.79 ng g^? 1 dw to 281.97 ng g^? 1 dw (mean: 115.92 ng g^? 1 dw) and the total EDC concentrations from 0.52 ng g^? 1 dw to 126.73 ng g^? 1 dw (mean: 37.49 ng g^? 1 dw). The distribution pattern for the PAHs was generally different from that of the EDCs possibly due to their distinct sources and n-octanol-/water partition coefficients (K_OW). Qualitative and quantitative analytical results showed that PAH sources were mainly from a mixture of pyrogenic and petrogenic contributions. The higher levels at the southeast of Geligang indicated that the EDC pollutants may have mainly originated from the plastic industry and other chemical plants located along the Liao River. Ecological risk assessment revealed that PAHs exhibited low ecotoxicological effects, whereas EDCs, especially 4-tert-octylphenol and bisphenol A, had high ecological hazard to the estuarine biota.  相似文献   

A pioneer in marine sediment risk assessment - a tribute to Ed Long (1942–2016)     

Michael Martin 《Marine pollution bulletin》2017,114(1):1-4

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Probabilistic analysis of soil‐structure interaction effects on the seismic performance of structures          下载免费PDF全文

Fariborz Mirzaie  Mojtaba Mahsuli  Mohammad Ali Ghannad 《地震工程与结构动力学》2017,46(4):641-660

This paper revisits the phenomenon of dynamic soil‐structure interaction (SSI) with a probabilistic approach. For this purpose, a twofold objective is pursued. First, the effect of SSI on inelastic response of the structure is studied considering the prevailing uncertainties. Second, the consequence of practicing SSI provisions of the current seismic design codes on the structural performance is investigated in a probabilistic framework. The soil‐structure system is modeled by the sub‐structure method. The uncertainty in the properties of the soil and the structure is described by random variables that are input to this model. Monte Carlo sampling analysis is employed to compute the probability distribution of the ductility demand of the structure, which is selected as the metrics for the structural performance. In each sample, a randomly generated soil‐structure system is subjected to a randomly selected and scaled ground motion. To comprehensively model the uncertainty in the ground motion, a suite of 3269 records is employed. An extensive parametric study is conducted to cover a wide range of soil‐structure systems. The results reveal the probability that SSI increases the ductility demand of structures designed based on the conventional fixed‐based assumption but built on flexible soil in reality. The results also show it is highly probable that practicing SSI provisions of modern seismic codes increase the ductility demand of the structure. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Wood and sediment storage and dynamics in river corridors          下载免费PDF全文

Ellen Wohl  Daniel N. Scott 《地球表面变化过程与地形》2017,42(1):5-23

Large wood along rivers influences entrainment, transport, and storage of mineral sediment and particulate organic matter. We review how wood alters sediment dynamics and explore patterns among volumes of in‐stream wood, sediment storage, and residual pools for dispersed pieces of wood, logjams, and beaver dams. We hypothesized that: volume of sediment per unit area of channel stored in association with wood is inversely proportional to drainage area; the form of sediment storage changes downstream; sediment storage correlates with wood load; the residual volume of pools created in association with wood correlates inversely with drainage area; and volume of sediment stored behind beaver dams correlates with pond area. Lack of data from larger drainage areas limits tests of these hypotheses, but the analyses suggest that sediment volume correlates positively with drainage area and wood volume. The form of sediment storage in relation to wood appears to change downstream, with wedges of sediment upstream from jammed steps most prevalent in small, steep channels and more dispersed sediment storage in lower gradient channels. Pool volume correlates positively with wood volume and negatively with channel gradient. Sediment volume correlates well with beaver pond area. More abundant in‐stream wood and beaver populations present historically equated to greater sediment storage within river corridors and greater residual pool volume. One implication of these changes is that protecting and re‐introducing wood and beavers can be used to restore rivers. This review of the existing literature on wood and sediment dynamics highlights the lack of studies on larger rivers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The concept of travelling bedload and its consequences for bedload computation in mountain streams          下载免费PDF全文

Guillaume Piton  Alain Recking 《地球表面变化过程与地形》2017,42(10):1505-1519

In bedload transport modelling, it is usually presumed that transported material is fed by the bed itself. This may not be true in some mountain streams where the bed can be very coarse and immobile for the majority of common floods, whereas a finer material, supplied by bed‐external sources, is efficiently transported during floods, with marginal morphological activities. This transport mode was introduced in an earlier paper as ‘travelling bedload’. It could be considered an extension of the washload concept of suspension, applied to bedload transport in high‐energy, heavily armoured streams. Since this fine material is poorly represented in the bed surface, standard surface‐based approaches are likely to strongly underestimate the true transport in such streams. This paper proposes a simple method to account for travelling bedload in bedload transport estimations. The method is tested on published datasets and on a typical Alpine stream, the Roize (Voreppe, France). The results, particularly on active streams that experience greater transport than expected from the grain sizes of their bed material, reinforce the necessity of accounting for the ‘travelling bedload concept’ in bedload computation. The method relevance is discussed regarding varying flood magnitudes, geomorphic responses and eventual anthropic origin of the ‘travelling bedload’ phenomena. To conclude, this paper considers how to compute bedload transport for a wide range of situations, ranging from sediment‐starved cases to the general mobile bed alluvial case, including the intermediate situation of external source supply on armoured bed. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

The effect of lithology on valley width,terrace distribution,and bedload provenance in a tectonically stable catchment with flat‐lying stratigraphy          下载免费PDF全文

Amanda Keen‐Zebert  Mark R. Hudson  Stephanie L. Shepherd  Evan A. Thaler 《地球表面变化过程与地形》2017,42(10):1573-1587

How rock resistance or erodibility affects fluvial landforms and processes is an outstanding question in geomorphology that has recently garnered attention owing to the recognition that the erosion rates of bedrock channels largely set the pace of landscape evolution. In this work, we evaluate valley width, terrace distribution, and bedload provenance in terms of reach scale variation in lithology in the study reach and discuss the implications for landscape evolution in a catchment with relatively flat‐lying stratigraphy and very little uplift. A reach of the Buffalo National River in Arkansas was partitioned into lithologic reaches and the mechanical and chemical resistance of the main lithologies making up the catchment was measured. Valley width and the spatial distribution of terraces were compared among the different lithologic reaches. The surface grain size and provenance of coarse (2–90 mm) sediment of both modern gravel bars and older terrace deposits that make up the former bedload were measured and defined. The results demonstrate a strong impact of lithology upon valley width, terrace distribution, and bedload provenance and therefore, upon landscape evolution processes. Channel down‐cutting through different lithologies creates variable patterns of resistance across catchments and continents. Particularly in post‐tectonic and non‐tectonic landscapes, the variation in resistance that arises from the exhumation of different rocks in channel longitudinal profiles can impact local base levels, initiating responses that can be propagated through channel networks. The rate at which that response is transmitted through channels is potentially amplified and/or mitigated by differences between the resistance of channel beds and bedload sediment loads. In the study reach, variation in lithologic resistance influences the prevalence of lateral and vertical processes, thus producing a spatial pattern of terraces that reflects rock type rather than climate, regional base level change, or hydrologic variability. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Predicting gravel bed river response to environmental change: the strengths and limitations of a regime‐based approach          下载免费PDF全文

Brett Eaton  Robert Millar 《地球表面变化过程与地形》2017,42(6):994-1008

Rivers respond to environmental changes such as climate shifts, land use changes and the construction of hydro‐power dams in a variety of ways. Often there are multiple potential responses to any given change. Traditionally, potential stream channel response has been assessed using simple, qualitative frameworks based largely on professional judgement and field experience, or using some form of regime theory. Regime theory represents an attempt to use a physically based approach to predict the configuration of stable channels that can transport the imposed sediment supply with the available discharge. We review the development of regime theory, and then present a specific regime model that we have created as a stand‐alone computer program, called the UBC Regime Model (UBCRM). UBCRM differs from other regime models in that it constrains its predictions using a bank stability criterion, as well as a pattern stability criterion; it predicts both the stable channel cross‐sectional dimensions as well as the number of anabranches that the stream must have in order to establish a stable channel pattern. UBCRM also differs from other models in that it can be used in a stochastic modelling mode that translates uncertainty in the input variables into uncertainty in the predicted channel characteristics. However, since regime models are fundamentally based on the concept of grade, there are circumstances in which the model does not perform well. We explore the strengths and weaknesses of the UBCRM in this paper, and we attempt to illustrate how the UBCRM can be used to augment the existing qualitative frameworks, and to help guide professionals in their assessments. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Effect of storms during drought on post‐wildfire recovery of channel sediment dynamics and habitat in the southern California chaparral,USA          下载免费PDF全文

Joan L. Florsheim  Anne Chin  Alicia M. Kinoshita  Samira Nourbakhshbeidokhti 《地球表面变化过程与地形》2017,42(10):1482-1492

Current global warming projections suggest a possible increase in wildfire and drought, augmenting the need to understand how drought following wildfire affects the recovery of stream channels in relation to sediment dynamics. We investigated post‐wildfire geomorphic responses caused by storms during a prolonged drought following the 2013 Springs Fire in southern California (USA), using multi‐temporal terrestrial laser scanning and detailed field measurements. After the fire, a dry‐season dry‐ravel sediment pulse contributed sand and small gravel to hillslope‐channel margins in Big Sycamore Creek and its tributaries. A small storm in WY 2014 generated sufficient flow to mobilize a portion of the sediment derived from the dry‐ravel pulse and deposited the fine sediment in the channel, totaling ~0.60 m³/m of volume per unit length of channel. The sediment deposit buried step‐pool habitat structure and reduced roughness by over 90%. These changes altered sediment transport characteristics of the bed material present before and after the storm; the ratio of available to critical shear stress (τ_o/τ_c) increased by five times. Storms during WY 2015 contributed additional fine sediment from tributaries and lower hillslopes and hyperconcentrated flow transported and deposited additional sediment in the channel. Together these sources delivered sediment on the order of six times that in 2014, further increasing τ_o/τ_c. These storms during multi‐year drought following wildfire transformed channel dynamics. The increased sediment transport capacity persisted during the drought period characterized by the longer residence time of relatively fine‐grained post‐fire channel sedimentation. This contrasts with wetter years, when post‐fire sediment is transported from the fluvial system during the same season as the post‐fire sediment pulse. Results of this short‐term study highlight the complex and substantial effects of multi‐year drought on geomorphic responses following wildfire. These responses influence pool habitat that is critical to longer‐term post‐wildfire riparian ecosystem recovery. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

水牛蹄型深海集矿机履齿设计及牵引性能研究     

丁聪  陈旭光  刘学麟  刘茜茜  李宗晏 《海洋工程》2024,(2):26-41

作为深海采矿系统的重要组成部分,深海集矿机的技术研究和开发一直是许多国家的难题。为了提高深海集矿机在稀软沉积物上的牵引性能,基于水牛蹄的曲面结构特征和特殊几何结构,设计了一款仿水牛蹄蹄型履齿。以该款履齿的结构参数为研究对象,通过对朗肯被动土压力理论的优化,得到了仿水牛蹄蹄型履齿的牵引力解析解,建立了对应的履齿仿生参数对履齿牵引力的影响公式。结合正交试验方法进行了不同形式履齿在沉积物上运动的单、多履齿剪切试验,将仿水牛蹄蹄型履齿与直型履齿、仿水牛蹄轮廓履齿（另一种仿生履齿）进行对比试验,并通过模型车试验验证了该款履齿的可行性。结果表明：3种履齿中,仿水牛蹄蹄型履齿提供的最大牵引力最高。研究可为进一步优化仿水牛蹄蹄型履齿结构参数和提高深海稀软底质机械的牵引性能提供参考依据。  相似文献   

山东半岛东北部海域悬浮体季节分布及控制因素   总被引：1，自引：0，他引：1  

朱颖涛  冯秀丽  朱龙海  胡日军  姜胜辉 《海洋地质与第四纪地质》2021,41(2):30-42

基于2018年山东半岛东北部海域冬、夏两季悬浮体浓度、浊度及水温和盐度调查资料,分析了研究区水体悬浮体浓度的季节性变化,探讨了其控制因素。结果表明:夏季浊度在0.2~37.8FTU之间变化,冬季浊度在1.5~100.1FTU之间变化,均表现为底高表低、东高西低的特征。夏季水温分层明显,表现为表层高、底层低的特征,盐度整体无明显变化;冬季温盐垂向上混合均匀,平面上表现为近岸低温低盐水体向远岸高温高盐水体的过渡。悬浮体浓度分布受潮流、波浪、温跃层和温盐锋面等因素影响。夏季,悬浮体垂向上受到温跃层影响,底层悬浮体难以向表层输运;平面上潮混合和波浪差异性作用阻碍了悬浮体的水平输运。冬季,强风浪促使悬浮体垂向混合剧烈,表层悬浮体浓度明显较夏季变高;平面上沿岸流和黄海暖流形成的温、盐锋面阻碍了水团间悬浮体的输运。  相似文献