平坦沙质地表蚀积量计算模型研究

通过对平坦沙质地表蚀积动态的野外观测,结合同时期区域风况资料,分析了平坦沙质地表蚀积过程。在输沙势和最大可能输沙量计算公式基础上,调整参数提出了平坦沙质地表蚀积量的计算模型,弥补了两者不能直观准确表示区域风沙活动的缺点。通过对比野外实测值与输沙势、模型预测值和最大可能输沙量之间的变化趋势得出它们存在同期波动特征。进一步比较回归方程可知,模型预测值回归方程更加显著,预测值更加接近实测值,能够更好地表示区域风沙活动特征和强度,可为沙漠的扩张和收缩提供量化预测依据。     

海岸风沙地貌分类研究现状

地处水陆交界地带的海岸地区,自然地理环境复杂,人类活动频繁,影响海岸风沙活动的自然及人为因素复杂多样;同时由于海岸风沙地貌分布的广泛性、区域的差异性、研究区域的不同和分类角度的差异等原因,故而到目前为止,对于海岸风沙地貌的分类,仍然存在着多种多样的分类系统。在现有国内外海岸风沙地貌的分类研究的基础上,进行了简单回顾,并指出了现有的海岸风沙地貌分类的不足和发展趋势。     

花岗岩风化壳崩岗侵蚀剖面风化强度和粒度分布特征

结合粒度法和化学风化指标法分析了花岗岩风化壳崩岗侵蚀剖面,结果显示:（1）粒度组成以粉砂砾组分最多,平均值为52.52%,砂砾组分为38.38%,黏粒组分最少,平均值为9.09%。4~63 μm粉砂粒组分分别与<1 μm细黏粒组分、<4 μm黏粒组分正相关性较好;>63 μm的砂砾组分与中值砾径呈显著正相关性,与<1 μm细黏粒组分、<4 μm黏粒组分、4~63 μm粉砂粒组分呈显著的负相关性。剖面580~780 cm深度可能是崩岗侵蚀起源区域。（2）化学蚀变指数CIA、风化淋溶系数BA、残积系数Ki和退碱系数Bc一致表明,崩岗侵蚀剖面的化学风化程度高。风化强度从底部往上呈现先小幅度递减而后波动递增的变化趋势。（3）风化参数指标和粒度线性相关性分析得知,化学风化作用强度增强,<1 μm细黏粒组分、<4 μm黏粒组分、4~63 μm粉砂粒组分增加,>63 μm砂砾组分减少。化学风化作用减弱,<4 μm黏粒组分、4~63 μm粉砂粒组分减少,>63 μm砂砾组分增多。     

黄河水量明显减少对下游河流地貌的影响

分析了黄河下游河床和河口区侵蚀及淤积的变化与黄河水沙变化的关系，黄河水量减少，包括总水量和洪峰水量的减少，会引起下游河床淤积，河口地区淤积减弱，甚至侵蚀后退，也会影响河口以外海岸带泥沙的供给情况，造成黄河三角洲海岸的侵蚀后退。     

Holocene fluvial-coastal interactions on a mixed sand and sand and gravel beach system, North Canterbury, New Zealand

Fluvio-coastal interactions are examined on a progradational sand, and mixed sand and gravel beach sequence between the Ashley and Kowai rivers, Pegasus Bay, New Zealand. This coastal system presents an example of a wave-dominated environment energetic enough to deal with the sediment supply derived from the rivers, but where the coast is still prograding. Progradation occurs because of the inability of the marine system to evacuate wave-eroded sediment from the bay floor. This results in gradual nearshore aggradation until nearshore storage is filled and sediment is finally transported landward to form a new beach ridge. This type of coastal system can be identified by a diagnostic morphological assemblage comprising a ‘small river’ coastal morphology (sensu Zenkovich (1967, Processes of Coastal Development, Oliver and Boyd, Edinburgh) backed by a sequence of beach ridges. Sediment fractionation (shape and size sorting) is identified as the primary effect of erosional processes on a mixed sand and gravel beach. Fractionation is capable of converting sandy beaches with minor gravel components to graveldominated beaches. Gravel is concentrated by the evacuation of sand from the shoreface. This occurs dominantly through storm sifting but also occurs in response to normal swash processes. This process is very similar to the process of chenier production on mixed mud and sand beaches, and fractionation is highlighted as a dominant erosional process on mixed beaches, irrespective of grain size.     

The Dynamics of Suspended Sediment Transport in the Ribble Estuary

Velocity and turbidity were measured over a tidal cycle during both spring and neap tides in the Ribble estuary England. The data was analysed to determine the relative magnitudes of the various components of the residual circulation and sediment flux. The Lagrangian residual circulation was found to be dominated by the influence of freshwater input to the estuary the landward directed component of the circulation due to the Stokes drift being cancelled by the Eulerian flow induced by set-upThe dominant driving mechanism of the residual flux of suspended sediment was found to vary both spatially and over the spring-neap cycle. During the neap tide the flux in the mid estuary was negligable, however, during the spring tide landward transport of sediment by the mechanism of tidal pumping was found to be the dominant mechanism.     

Sedimentary characterization of Tagus estuarine beaches (Portugal)

Background, Aim and Scope  The distribution of sediments in estuarine beaches is controlled by the interactions between sediment supply, hydrodynamic processes and human intervention. The main purpose of this study is to characterize the sediments of Tagus estuarine beaches in order to understand their origin and to contribute to a better knowledge of the Tagus estuary sediment budget. Methods  Surface sediment samples were collected across beach profiles and sand grain size analysis was performed by dry sieving. Grain size statistics for the median (d₅₀) and standard deviation (SDM) were obtained using the Moment method. This study was complemented by a qualitative evaluation of the sediment composition. Cross-shore topographic surveys were conducted for selected sampling sites. Results  Tagus estuarine beach sediments are mainly composed of quartz sand particles which are fine-grained and well sorted near the mouth of the estuary and medium to coarse-grained and moderately sorted in the inner domain. Compositional results show evidence of active anthropogenic sediment sources, especially in the coarser fractions. Discussion  The analysis of the textural and compositional characteristics of beach sediments in the inner estuarine domain is compatible with local sedimentary sources, while a marine signature is present at the mouth and inlet channel sediments. In the inner domain, differences in the sedimentary processes are represented by the textural characteristics of the sediments, such as the sorting degree and the gravel content. Sediment characteristics also reflect human intervention in the system, with the introduction of anthropogenic and allochthonous particles and the mixture of sediments from different sources. Conclusions  The sediments of the inner Tagus estuarine beaches are derived from local Plio-Pleistocene outcrops while inlet and outer estuary beaches reveal a dominant marine source. Beach textural variability observed in the inner domain is not related to wave forcing gradients, but mainly to variations in the sedimentary processes along the estuarine margins and to human intervention. Results show that the Tagus estuarine beaches depended, almost exclusively, on sediment input from local sources until the last century. With increasing human occupation, sediment transfers became dominated by anthropogenically related activities mainly connected with the occupation of estuarine margins and dredging. Recommendations and Perspectives  Further studies should extend the present level of knowledge in what concerns sand transport patterns through additional compositional and geochemical analysis, and the development of new techniques in order to allow the quantitative evaluation of the impact of human activities on the sediment budget.     

塔里木盆地荒漠类型及其抗风蚀特征初探

塔里木盆地的荒漠面积达到 5 2 .1× 10 6 hm2 ,按物质组成、地表景观和形成 ,荒漠可划分为盐漠、泥漠、砾漠和沙漠 4种类型。从不同荒漠类型剖面结构特点看 ,盐漠表层有盐结皮或盐结壳 ,泥漠则板结而坚硬 ,砾漠在地表有砾幕 ,它们都有一定抗风蚀的能力。沙漠中的沙丘组成物质以细沙为主 ,无特殊抗风蚀层次。尽管塔里木盆地的一些荒漠类型有一定抗风蚀的结构特点 ,加强荒漠区域的生态保护仍是非常重要。     

Community structure and abundance of comammox Nitrospira in Chongming eastern intertidal sediments

Purpose

Complete ammonia oxidizers (comammox), which convert ammonia to nitrate through nitrite, are a newly discovered nitrifying group. In recent years, comammox Nitrospira have been discovered in various natural and engineered ecosystems. However, little is known about the distribution dynamics of comammox Nitrospira in estuary tidal flat sediments.

Materials and methods

Chongming eastern tidal flat, the largest tidal flat in the Yangtze River Estuary, was selected as the research area. Through a combination of molecular biology assays, phylogenetic analysis based on functional gene sequences and statistical correlation with physicochemical properties, we determined the distribution and diversity of comammox Nitrospira in Chongming eastern tidal flat and analyzed the potential influencing environmental factors.

Results and discussion

The results indicated comammox Nitrospira were widely distributed in Chongming eastern tidal flat, while with lower abundance than the ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Clade A1 comammox Nitrospira showed adaptation to relatively high salinity, and was more distributed in middle and low tidal flats, while clade A2 and clade A3 were mostly distributed in high tidal flats with low salinity. The abundance and community structure of comammox Nitrospira were mainly affected by salinity, ammonia concentration, and temperature.

Conclusion

This study showed the general existence of comammox Nitrospira in Chongming eastern intertidal sediments and indicated that the differences of tidal locations, which lead to a gradient in the physicochemical properties of the sediments, in turn affects the spatial distribution of comammox Nitrospira in estuary tidal flats.

     

辽东半岛海岸侵蚀分布规律及其发育特征

为了探明辽东半岛海岸侵蚀的分布规律和发育特征,结合海岸侵蚀的现场调查资料,对辽东半岛海岸蚀淤状况和侵蚀发育特征进行了研究。结果表明,辽东半岛海岸可划分为严重侵蚀、强侵蚀、侵蚀、微侵蚀、稳定共5种侵蚀等级。其中,沙质海岸侵蚀较重的区域主要分布在绥中和鲅鱼圈一带,基岩海岸侵蚀较重的区域主要分布在大连金石滩一带,粉沙淤泥质海岸侵蚀较重的区域分布在庄河一带。河流入海泥沙的减少是近年来辽东半岛海岸侵蚀的主要原因,气候变暖引起的海平面上升对辽东半岛海岸侵蚀起一定的控制作用。此外,人为采砂和不合理的海岸工程进一步加剧了局部海岸侵蚀的程度。     

沿海滩涂开发空间优化与管制研究——以江苏省大丰区为例

[目的]研究沿海滩涂开发空间优化方法与管制策略,为探寻滩涂资源保护与开发的高效路径提供依据。[方法]以江苏省盐城市大丰区为例,通过集成开发适宜性评估与部门规划协调方法,揭示该区沿海滩涂资源开发空间优化格局;引入空间管制理念,讨论该区滩涂资源开发的空间管制路径。[结果]实证分析认为,该区沿海滩涂地区的生态保护、农业生产以及港口—工业—城镇开发三类空间适宜开发的规模分别为401,323和444km2,分别占34.3%,27.7%和38.0%。[结论]生态空间的环境质量底线保护和港工城空间的高效集约利用是滩涂区域空间管制的核心准则;同时,滩涂区域开发规模和强度控制仍然需要深入跟踪与分析。     

海涂土地资源适宜性空间分析与优化开发模式研究

海涂是沿海地区重要的后备土地资源,适宜性评价与优化利用结构是科学开发海涂的前提.选取典型海涂围垦区,把GIS空间分析与数学规划模型结合起来,首先基于GIS空间分析技术,对海涂土地资源适宜性进行评价;然后针对研究区内的新围海涂,运用数学规划模型对其土地利用数量结构进行优化,优化结果中总土地开发利用系数为0.629,在开发投资效益最大化的基础上兼顾了海涂生态环境保护.结合海涂开发用地规划,提出土地利用结构的优化配置模式,实现海涂土地资源开发中定性分析、定位配置与定量优化的结合.     

Shoreline stabilization approaches in response to sea level rise: U.S. experience and implications for Pacific Island and Asian nations

Coastal erosion is a worldwide problem; it is estimated that over 70% of the world's beaches are currently experiencing erosion (Bird, 1985), and this number may approach 90% in the United States. Almost every conceivable form of shore protection has been attempted in the United States, including construction of seawalls, groins, and jetties as well as beach nourishment. The principal approach to protecting coastal property and maintaining recreational beaches in the United States today is beach nourishment. Engineering structures such as groins and seawalls have often been shown to have detrimental effects on adjacent beaches. Also, their construction and maintenance costs are quite high. Therefore, coastal communities have come to rely on a “soft” engineering solution — beach nourishment —because it is environmentally sound, aesthetically pleasing, and, so far, economically feasible. However, global warming and accelerated sea level rise will cause more rapid rates of beach loss and could make even this alternative too costly for many resort areas along the U.S. shoreline. The cost to nourish all the major recreational oceanic beaches in the United States was estimated based on various sea level rise scenarios. The beach nourishment approach involves placing enough sand on the beach to maintain stable (nonretreating) conditions in response to rising sea level. The quantity of sand required to “hold the line” is evaluated under various sea level rise scenarios from the baseline scenario to the 1-m estimate of the Intergovernmental Panel on Climate Change. Beach nourishment is not a practical alternative for most Pacific island nations because sand is a scarce resource. In fact, beaches are often mined for sand for construction, contributing to beach erosion. For mainland countries, beach fill projects are more practical. Singapore was one of the first countries to use this technology in combination with building offshore breakwaters to form artificial headlands. As Western style sunbathing and the overall popularity of beaches for recreation continue to grow, beach nourishment can be expected to become a more common way to deal with sea level rise induced coastal erosion for highly developed beach resort areas.     

Long‐term Human Impacts on the Coast of La Graciosa,Canary Islands

Global change is affecting coastal areas and leading them to degradation. This is severe in sand dunes and sand plains, because they are very fragile ecosystems. The objective of this paper is to characterize the relationship between the historical land uses and the aeolian sedimentary dynamics in an arid coastal system, the island of La Graciosa (Canary Islands) since the second half of the 18th century. The methodology is based on the interpretation of historical documents, aerial photographs and oral testimonies to characterize the changes in the island, in terms of both land use and aeolian geomorphology. The results suggest the existence of six stages during which the intensity of human pressure on the environment changed. Copyright © 2015 John Wiley & Sons, Ltd.     

沙质草原槽形风蚀坑表面沉积物粒度特征

通过对呼伦贝尔沙质草原槽形风蚀坑表面沉积物粒度的观测分析,发现活跃发展时期的槽形风蚀坑沙物质总体结构以中沙为主,其次是细砂,粗砂和粉沙含量很少,且不含砾石。由于沙源沉积物粒度组成比较均一,风蚀坑各部位粒径频率曲线均呈单峰对称（或近对称）。响应于风力侵蚀和堆积,在粒度诸参数中,粗沙和细沙含量,频率曲线众数粒径,以及平均粒径等发生了明显的变化。该研究结果作为表面气流的响应,支持了先前提出的槽形风蚀坑动力学过程。     

不同高度阻沙栅栏蚀积过程及防沙效益研究

通过对不同高度阻沙栅栏蚀积过程的野外观测,结合同时期区域风况资料,分析了阻沙栅栏前后地表蚀积形态、蚀积量以及蚀积强度的时空变化特征。结果表明,在沙源充足条件下,不同高度阻沙栅栏上风向表现为风沙堆积,下风向风蚀与堆积共存,且程度与栅栏高度有关,栅栏总体蚀积量和蚀积强度的变化趋势与下风向变化趋势相近。其中,60和70cm高度阻沙栅栏风沙堆积量最大,防沙效果最佳,但二者积沙方向存在差别。70cm高度阻沙栅栏上风向积沙较多;60cm高度阻沙栅栏下风向积沙较多。在实际应用中,应依据防护对象合理配置阻沙栅栏并适时加高,避免阻沙栅栏过低或过高,进而影响防沙效果。此外,依据断面形态、蚀积量和蚀积强度的变化,将栅栏前后分为风沙堆积区、风蚀区和蚀积平衡区。     

Einfluß der Fließstreckenlänge auf die Bodenumlagerung innerhalb einer erosionsgeschützten Kleinparzelle

Dependence of erosion from flow length within an erosion-protected plot On an Udalf derived from loess different micro-reliefs were formed to reduce erosion. Their effects on the spatial distribution of sand contents on bare soil after one vegetation period are described. At first erosion caused residuals of sand on unflooded areas and corresponding accumulation of finest material on flooded ones. Beds without flow barriers showed reduced clay and silt contents in the upper layer of about 2 mm. On beds with small dams there were no soil losses from the catchment areas between these flow barriers visible. Secondly the enriched sand was moved, too. This occured widely on flat beds. Within catchment areas there were only very small deposits of removed sand in front of the dams. In conclusion: Within the limits of a chosen risk, artificial microreliefs reduce completely erosion damages.     

黄河流域的土壤风力侵蚀

黄河流域土壤风蚀面积约10.3万km~2,占流域总面积的13.7％。主要发生在阴山山脉以南和长城以北地区。本文根据遥感制图和面积测算,介绍了风蚀区地貌、气候、植被概况,论述了土壤风蚀的基本因素及向沙漠化、砾漠化、岩漠化方向发展的三种途径,最后对土壤风蚀进行了分级,探讨了风蚀对河流产沙的影响。     

水土流失与地貌侵蚀

物质的侵蚀-搬运-堆积是地貌发育的主要过程。水土流失目前主要是指第一阶段即地貌发育的侵蚀过程。地貌的侵蚀一般被分为两类:自然侵蚀和人为侵蚀,而人为侵蚀被认为是水土流失的主要原因。笔者认为,人类活动固然加剧了侵蚀过程的发生,但它是在自然侵蚀的基础上进行的,它是符合自然侵蚀规律的。在目前的社会条件下,水土流失的治理不仅仅是减少人类活动的影响,而应该是使人类活动在地貌演化过程中扮演因势利导的角色,使其向着人类有利的方向发展。     

围垦对崇明东滩湿地全程氨氧化微生物的影响

全程氨氧化微生物（comammox）的发现根本改变了学术界对硝化过程的认识，但其地理分异规律及对氮转化过程的贡献仍不清楚。本研究选择长江口崇明东滩不同围垦年限（0、27、51、86年）稻田表层耕作土壤，采用好氧培养试验测定土壤硝化潜力；通过标靶功能基因amoA实时荧光定量硝化微生物的数量变异特征，包括全程氨氧化细菌（comammox）、氨氧化细菌（AOB）和古菌（AOA）。结果表明，与围垦0年的自然滩涂湿地相比，围垦27、51、86年的水稻土净硝化速率从2.24mg N /(kg·d)分别增加至19.3、11.6和11.4mg N /(kg·d)，增幅高达5.1-8.7倍。土壤氨氧化古菌AOA的丰度与围垦年限显著正相关。自然滩涂湿地中氨氧化古菌AOA和AOB的数量分别为0.34×107 copies/g和1.14×107 copies/g，围垦86年后增幅最高可达27.9倍。自然滩涂湿地中comammox Clade A和Clade B amoA基因拷贝数高于围垦稻田土壤，且Clade A随着围垦年限增加其丰度显著增加。统计分析发现，氨氧化细菌AOB与土壤硝化速率显著正相关，可能在围垦水稻土氨氧化过程中发挥了重要作用；而全程硝化细菌comammox Clade A和Clade B与土壤总有机碳（TOC）、铵含量（NH4+）呈显著负相关关系，可能更适应于营养贫瘠的滩涂自然湿地土壤。