Measuring Aeolian Saltation: A Comparison of Sensors

SHERMAN, D.J.; LI, B.; FERRELL E.J.; ELLIS, J.T.; COX, W.D.; MAIA, L.P., and SOUSA, P.H.G.O., 2011. Measuring Aeolian Saltation: A Comparison of Sensors. In: Roberts, T.M., Rosati, J.D., and Wang, P. (eds.), Proceedings, Symposium to Honor Dr. Nicholas C. Kraus, Journal of Coastal Research, Special Issue, No. 59, pp. 280-290. West Palm Beach (Florida), ISSN 0749-0208. We report the results of field experiments designed to compare four types of aeolian saltation sensors: the Safire; the Wenglor (R) Particle Counter; the Miniphone; and the Buzzer Disc. Sets of sensors were deployed in tight spatial arrays and sampled at rates as fast as 20 kHz. In two of the three trials, the data from the sensors are compared to data obtained from sand traps. The Miniphone and the Buzzer Disc, based on microphone and piezoelectric technologies, respectively, produced grain impact counts comparable to those derived from the trap data. The Satire and the Wenglor (R) Particle Counter produce count rates that were an order of magnitude too slow. Satires undercount because of their large momentum threshold and because its signal is saturated at relatively slow transport rates. We conclude that the Miniphone and the Buzzer Disc are appropriate for deployment as grain counters because their small size allows them to be installed in closely-spaced sets.

Sediment-transport (wind) experiments in zero gravity

The carousel wind tunnel (CWT) can be a significant tool for the determination of the nature and magnitude of interparticlar forces at threshold of motion. By altering particle and drum surface electrical properties and/or by applying electric potential difference across the inner and outer drums, it should be possible to separate electrostatic effects from other forces of cohesion. Besides particle trajectory and bedform analyses, suggestions for research include particle aggregation in zero and sub-gravity environments, effect of suspension-saltation ratio on soil abrasion, and the effects of shear and shear free turbulence on particle aggregation as applied to evolution of solar nebula.

Modification to the Hardisty equation, regarding the relationship between sediment transport rate and particle size

Bagnold-type bed-load equations are widely used for the determination of sediment transport rate in marine environments. The accuracy of these equations depends upon the definition of the coefficient k(1) in the equations, which is a function of particle size. Hardisty (1983) has attempted to establish the relationship between k(1) and particle size, but there is an error in his analytical result. Our reanalysis of the original flume data results in new formulae for the coefficient. Furthermore, we found that the k(1) values should be derived using u(1) and u(1cr) data; the use of the vertical mean velocity in flumes to replace u(1) will lead to considerably higher k(1) values and overestimation of sediment transport rates.

The Aeolian Flux of Calcium, Chloride and Nitrate to the McMurdo Dry Valleys Landscape: Evidence from Snow Pit Analysis

We have determined the flux of calcium, chloride and nitrate to the McMurdo Dry Valleys region by analysing snow pits for their chemical composition and their snow accumulation using multiple records spanning up to 48 years. The fluxes demonstrate patterns related to elevation and proximity to the ocean. In general, there is a strong relationship between the nitrate flux and snow accumulation, indicating that precipitation rates may have a great influence over the nitrogen concentrations in the soils of the valleys. Aeolian dust transport plays an important role in the deposition of some elements (e.g. C(2+)) into the McMurdo Dry Valleys' soils. Because of the antiquity of some of the soil surfaces in the McMurdo Dry Valleys regions, the accumulated atmospheric flux of salts to the soils has important ecological consequences. Although precipitation may be an important mechanism of salt deposition to the McMurdo Dry Valley surfaces, it is poorly understood because of difficulties in measurement and high losses from sublimation.

(Table 2) Properties of relict ice and sand wedges from six sites near Rio Gallegos, southern Patagonia

Relict sand wedges are ubiquitous in southern Patagonia. At six sites we conducted detailed investigations of stratigraphy, soils, and wedge frequency and characteristics. Some sections contain four or more buried horizons with casts. The cryogenic features are dominantly relict sand wedges with an average depth, maximum apparent width, minimum apparent width, and H/W of 78, 39, 3.8, and 2.9 cm, respectively. The host materials are fine-textured (silt loam, silty clay loam, clay loam) till and the infillings are aeolian sand. The soils are primarily Calciargidic Argixerolls that bear a legacy of climate change. Whereas the sand wedges formed during very cold (-4 to -8 °C or colder) and dry (ca. <=100 mm precipitation/yr) glacial periods, petrocalcic horizons from calcium carbonate contributed by dustfall formed during warmer (7 °C or warmer) and moister (>= 250 mm/yr) interglacial periods. The paleo-argillic (Bt) horizons reflect unusually moist interglacial events where the mean annual precipitation may have been 400 mm/yr. Permafrost was nearly continuous in southern Patagonia during the Illinoian glacial stage (ca. 200 ka), the early to mid-Pleistocene (ca. 800-500 ka), and on two occasions during the early Pleistocene (ca. 1.0-1.1 Ma).

毛乌素沙地土地利用/土地覆被变化研究

毛乌素沙地是我国十二大沙漠之一，地处北方干旱半干旱区向亚湿润区过渡地带，长期以来，不合理的人类土地利用，结合当地脆弱的环境生态特征，引起了严重的现代荒漠化过程，是我国北方荒漠化研究的重点地区。本文着重从自然和人文学科密切合作的角度，对毛乌素沙地土地利用／土地覆被变化的内在作用机制进行了研究，得到以下主要结论： 1. 利用多年实地观测数据资料，考察了毛乌素沙地四种主要草地类型代表性植物群落地上生物量响应气候因子波动的变化规律，建立了植物地上生物量对气候因子的逐月回归模型，揭示出如下规律：①各种气候因子对不同类型草地以及同一类型不同生长阶段草地都产生不同的影响作用;②同一气候因子在植物不同生长阶段上，对生物量形成的重要性程度存在差异：③在植物生长期内，每个生长阶段的生物量都对后一时期的生物量产生显著影响，说明植物生长的连续性对于生物量的形成和积累是重要的;④在植物的凋枯期，各种气候因子基本上都不对生物量产生显著影响;⑤水分因子对毛乌素沙地几乎各种类型草地的生物量，都是重要的影响因子，毛乌素沙地降水状况在不同年份的显著波动对草地植物地上生物量的影响，不仅直接构成了土地覆被变化的重要组成部分，而且还影响到土地利用的方式、方法和后果。 2. 在考察毛乌素沙地草地地上生物量对气候因子变化的响应规律中，利用逐月动态回归建模方法改进了传统的累积气候因子回归建模方法。逐月回归模型与累积回归模型的比较显示，逐月动态回归模型的优势表现在三个方面：①可以提供累积回归模型无法揭示的作用规律;②模拟更加精确;③可以预测不同气候条件下群落地上生物量的变化范围。 3. 利用风速、降水和潜在蒸发等气象记录资料，建立了毛乌素沙地气候因子影响沙尘暴频率的作用模型，定量地考察了沙地各处气候因子对沙尘暴频率的影响作用。研究表明，气候因素是导致毛乌素沙地沙尘暴发生的主导原因，在沙地各处，气候因子可以解释沙尘暴频率分布格局总信息的比率分别为：乌审召83.6%，乌审旗77.5%，河南82.4%，鄂托克旗79.8%，新街73.1%，伊金霍洛旗82%。 4. 在定量考察气候因素对沙尘暴频率影响作用的基础上，对影响沙尘暴频率格局的自然和人为因素进行了定量分离，研究表明：人为影响因素对对沙尘暴发生起次要作用，解释沙尘暴频率分布格局信息的比率分别为：乌审召16.4%，乌审旗22.5%，河南17.6%，鄂托克旗20.2%，新街26.9%，伊金霍洛旗18%。 自然和人为因素影响作用的定量分离研究表明，毛乌素沙地人为因素的影响作用表现出空间上的差异性：①从方位上说，呈现自东向中、西部递减的梯度：②从地点上说，城镇附近人为影响作用远高于农村地区;③从土地利用方式上说，农垦种植业区域高于畜牧业区域。 5. 在实地观测基础上，建立了裸露沙面和植被覆盖沙面风蚀输沙率模型，定量考察了植被覆盖率与风蚀输沙率之间的关系。研究表明：当植被覆盖率达到60%以上，可以保护地表土壤使风蚀在大多数条件下不致发生;当覆盖率达到40%，可以使风蚀输沙大为减少;而当植被覆盖率低于10%，植被覆盖基本不能对地表土壤起到有效的防护作用。 6. 应用植被覆盖地表风蚀输沙率模型，考察了沙地不同风速条件下植被有效覆盖率。根据当地气象台站的多年气象记录，沙地最大风速在20m/s左右，这样的风速条件下，保证风蚀不致发生的植被有效覆盖率为65%左右;在沙地常见的大风风速14-16m/s下，植被有效覆盖率大致为50-55%;对于沙地一般的中等风速l0-12m/s．植被有效覆盖率为40%。植被覆盖对风蚀的影响作用也可以理解为，植被覆盖使沙粒起动风速发生了增大效应，研究表明：与裸露沙面沙粒起动风速4.5m/s对照，70%植被覆盖率使起动风速改变为15.4m/s;60%植被覆盖率使起动风速改变为12.1m/s;40%植被覆盖率使起动风速改变为8.Om/s;而在10%植被覆盖条件下，起动风速为5.Om/s，改变量很小，说明植被覆盖的保护作用极其有限。 7. 基于野外实地观测，比较了沙地五种常见植物种和二种人工防护材料防风效应上的差异。研究表明，防风效应由高到低的次序是，沙蒿>芨芨草>杨柴和牛心朴子>沙障>栅栏>旱柳;就乔、灌、草和人工材料而言，防风效应的次序是，灌木植被>草本植被>人工材料>乔木植被。植物和人工防护材料降低风速的比率与风速呈现二次函数关系，不同植物种或人工材料，降低风速比率都表现出不同的规律，在一般情况下，降低风速效应随着风速的增大而降低。 8. 通过不同植物种防风效应的比较研究，对毛乌素沙地植被生态建设的实践有一定的指导意义。毛乌素沙地的植被建设中对植被类型和植物种类的选择，应该遵循如下原则：①选取防风固沙效应好的植物种类;②应该考虑植物水分供给与需求的平衡状况，实行适地适树;③植物防护效应应该与当地风蚀气候在时间上较好地匹配，在春季等风蚀严重季节，植被覆盖应该具有较好的防风效应。 9. 在现实中，各种影响风蚀的因素是同时发挥作用的。将风蚀影响因素分解为风速、湿润度和植被覆盖率（以及植被类型）三个方面，在此基础上，建立了风蚀影响因素的综合作用的概念模型和沙丘活动性指数定量模型。湿润程度低、风速高、植被覆盖率低的地区，是风蚀最为严重的地区;在湿润程度高、风速低、植被覆盖率高的地区，是风蚀最弱的地区;在其他地区，风蚀状况根据三个方面因素的综合状况来决定。 10. 利用风蚀影响因子综合作用的沙丘活动性指数模型，从空间、时间、植被类型变化角度，考察了毛乌素沙地的风蚀变化状况。得到如下结论：①随着空间变化，风速、降水等气候因素也随之存在差异，导致沙丘活动性指数的变化规律是，西北部鄂托克旗沙丘活动性最高，乌审旗次之，其他几个站差别不太显著，这是由各地降水、气温、沙粒粒径等因素共同决定;②随着时间的变化，气候、植被生长等方面的状况随之发生改变，导致沙丘活动性发生变化，春季最高，冬季次之，夏秋季最低：③随着沙丘植被覆盖类型的变化，沙丘活动性也发生显著变化，在一般情况下，乔木覆盖沙丘活动性>草本植物覆盖沙丘>灌木覆盖沙丘。 11. 在实地调查土地利用现实状况及其社会、经济和政策影响因素的基础上，建立了我国北方干旱半干旱区土地利用决策机制的概念模型，分析了与土地利用密切相关的农牧民一政府一环境科学家这三个社会群体对土地利用的立场和影响作用力上的差异，分析了毛乌素沙地土地利用的现状及其影响因素，探讨了现实中不可持续土地利用行为发生的社会、经济和政策原因。 12. 在实地调查基础上，分别利用产出一费用分析法和过程影响因素分析法，建立了毛乌素沙地土地利用经济收益的定量模型。产出一分析研究表明，无论是农垦种植业，还是草地畜牧业，农牧民从这两种土地利用方式都只能获得较低下的经济收益。造成这种状况的原因，主要在于两个方面：一是低下且不断处于波动之中的农牧业产品物价，二是沉重的农牧业税收。 13. 将影响农牧业产出的因素，划分为四个方面：土地面积（牲畜头数）、环境状况、管理水平和利用强度，在此基础上建立了定量的影响作用模型。研究表明：环境状况指数每增加0.1，农牧业经济收益增加26%;管理水平因子每提高0.1，农牧业经济收益增加12.7%;农牧业经济收益最优的土地利用强度在0.4左右，在此之前，随着利用强度的增加，经济收益随之增大，而在此之后，随着利用强度的增大，经济收益逐渐降低，当土地利用强度达到0.9左右时，呈现负的经济收益。 14. 毛乌素沙地实施土地资源可持续利用，必须从技术的革新和社会经济政策等因素的调整两条途径同时入手，二者缺一不可。通过改进和应用节水灌溉、风能光能利用、生物增产技术，尽可能地提高各种资源的利用效率;通过应用免耕或浅耕技术，尽量减轻土地利用对资源和环境的破坏;通过栽培、速生技术，提高植被建设的成效和速度。而通过税收、物价政策的调整，尽可能地提高农牧民经济收益增长的速度，减轻土地利用压力;通过政府与人民之间对话和合作机制的建立，让广大农牧民参与到土地利用的决策和管理的过程中去;通过土地利用管理政策、措施的调整和完善，调动农牧民保护资源的积极性和自觉性;通过激励机制的建立，引导农牧民土地利用向着可持续的方向发展。 15. 实现毛乌素沙地土地资源可持续利用的有效途径，在于这样几个方面：①建立和完善政府及其管理部门与人民之间有效的对话和合作机制，让广大农牧民参与到土地利用决策和管理的过程中去：②实行产业结构调整，转变片面追求经济增长的做法，制订适应当地自然条件和生态特征的发展模式;③降低农牧业税收、稳定并提高农牧业产品的物价，增加农牧民经济收入，减轻土地利用压力;④进一步改进和完善土地利用管理政策和法规;⑤建立有效激励机制，引导农牧民土地利用向着可持续的方向发展：⑥努力改进节水灌溉技术、生物增产技术，提高土地利用的科技水平：⑦改进环境保护和植被建设决策的科学性，提高植被建设的成效。

A study of the constraints affecting ornamental fish production in Sri Lanka

Although Sri Lanka is endowed with favourable climatic conditions and resources for breeding and rearing ornamental fish for export, a considerable number of ornamental fish producers as well as exporters have given up the industry within a relatively short period of time. This study was conducted to understand the present status of the industry and to identify the problems that have caused these failures. The study was conducted from March to December in the year 2007 and covered Colombo, Kaluthara, Polonnaruwa, Negombo, Wattala, Rathnapura, Avissawella, Kandy, Kegalle, Padukka, and Gampaha areas, where ornamental fish culture is known to be popular. The survey was carried out by interviewing ornamental fish farmers using a structured questionnaire survey that was designed to elicit the required information. Most (75%) of those surveyed were identified as small scale farmers. A majority (56%) of them used only cement tanks for their culture activities. Only 47% of farmers had proper technical knowledge or training on fish culture while 42% directly supplied their fish products to the expo1iers. The most important constraints identified by the study were as follows: (1) the sale price offish not changing in keeping with the increase in the material costs of production - Feed, cement, sand, transport and labour - in recent years. (2) Difficulty to find export markets for newcomers to enter the export market. (3) Lack of quality brooders and information on the most suitable fish varieties for the different climatic and water conditions in different areas in the country (3) Feed availability and cost. (4) Lack of adequate knowledge and technical support with regard to disease control and water quality management. (5) Difficulty to survive in the off season. (6) Difficulty in obtaining credit for expansion and the lack of sufficient involvement of responsible authorities in overcoming all these identified constraints.

Origin, development and evolutionary model of shelf desertization environment in late stage of Upper Pleistocene

Based on the study of palaeo-environmental evolution in the shelves of the Eastern China Seas, the concept of ''shelf desertization'' in the late stage of Upper Pleistocene is defined; the environmental background and evolutionary process of shelf desertization are analysed. Study on the records of subbottom profiling and the data of core samples from shelf areas revealed that during low sea-level stages, the sedimentary environment in the exposed shelf plains was dominated by aeolian depositional process under cold and dry climatic conditions, i.e. under the action of strong winter-monsoon winds. Parts of the exposed marine strata were disintegrated, and aeolian sand dunes were formed on the disintegrated marine deposits, from which the finer sediment grains were blown away by wind and deposited in the downwind areas to form the derivative loess deposits. Thus a desertization environmental system was formed in the exposed shelf plains of the Eastern China Seas.

末次冰盛期以来中国东部沙地空间分布特征及环境记录

The latest two extreme scenarios of last glacial maximum and Holocene climatic optimum marked extreme situations in China. This paper aims to reconstruct the fossil extensions and paleoclimate of deserts in eastern China during this typical period. Aeolian sequence responds the climate change by virtue of alternation of aeolian sand layer and sandy soil layer, which correspond aridity and humidity, respectively. There is a set of contrastive deposits made up of loose sand layer and overlying dark sandy soil below land surface. This developed soil and underlying deep aeolian sand respond to H.O. and late last glacial, i.e. LGM. The typical bottom sand layers of about 50 profiles of Hulun Buir Desert, Horqin Desert and Otindag Desert were dated using OSL to confirm that they did deposid in LGM. Based on the locations of these LGM sand, distrution of gobi-desert-loess and landform control, the distribution in LGM of the three deserts were reconstructed. For the block of eastern mountain, the extreme eastern boundary of Hulun Buir Desert and Otindag Desert are not just functioned by climate background. The east of Horqin Desert is plain, hence eastern boundary of this desert is maily controlled by climate. It is considered that quite a lot of aeolian sand of LGM origined from fluvial deposit by observing regional distribution of river and SEM of sand grains. The environment alternation of of LGM-H.O. is featured by extensive expanse of active dune in LGM and grassland in H.O. Combined grain-size, susceptibility, TOC, colour and SEM measurement, the OSL chronology of relatively continued profiles since LGM of the three deserts are divided into four periods: eolian sand (15-10ka)- sandy soil (10-5ka)- alternation of black sand and yellow sand- reworking of LGM sand as destroy of soil.

Age and palaeoenvironmental significance of an inter-tidal peat bed at Ballywoolen, Bann estuary, Co. Londonderry.

A recently exposed inter-tidal peat bed at Ballywoolen, Bann estuary, Co. Londonderry, has yielded new information about mid-Holocene coastal environmental change in the northeast of Ireland. Pollen analytical data and wood detritus demonstrate that peat accumulation occurred in a terrestrial environment that was free from marine influence. Radiocarbon dates suggest that the peat accumulated rapidly during a period of low relative sea level subsequent to the maximum of Holocene relative sea-level rise along the north coast of Northern Ireland. The absence of marine/brackish indicator taxa at the site suggests that the tidal range was somewhat less than that at present and/or that the channel of the river was located some distance east of its present alignment. The dates indicate that the low stand lasted for at least ~0.2 ka and possibly for ~1.1 ka. Stable, woodland-dominated landscapes are indicated at both this site and neighbouring ones around ~6.4-5.3 cal ka BP. There is no evidence for large-scale aeolian sand movement or human impact on the landscape during the period of peat accumulation.

Holocene vegetation dynamics in the northeastern Rub' al-Khali desert, Arabian Peninsula: a phytolith, pollen and carbon isotope study

The Holocene vegetation history of the Arabian Peninsula is poorly understood, with few palaeobotanical studies to date. At Awafi, Ras al-Khaimah, UAE, a 3.3 m lake sediment sequence records the vegetation development for the period 8500 cal. yr BP to similar to3000 cal. yr BP. delta(13)C isotope, pollen and phytolith analyses indicate that C3 Pooid grassland with a strong woody element existed during the early Holocene (between 8500 and 6000 cal. yr BP) and became replaced by mixed C3 and C4 grasses with a strong C4 Panicoid tall grass element between 5900 and 5400 cal. yr BP. An intense, arid event Occurred at 4100 cal. yr BP when the lake desiccated and was infilled by Aeolian sand. From 4100 cal. yr BP the vegetation was dominated by C4 Chloridoid types and Cyperaceae, suggesting an incomplete vegetation cover and Aeolian dune reactivation owing to increased regional aridity. These data outline the ecosystem dynamics and carbon cycling in response to palaeomon-soon and north-westerly variability during the Holocene. Copyright (C) 2004 John Wiley Sons, Ltd.

Distinção entre areias eolicas e praiais pele analise discriminante

Beach deposits occur in high energy environments with continual sorting by swash and backswash. The fines are removed by the backswash, which is not competent to remove the coarser material. Hence negative asymmetry (skewness) results. The wind transports only the finer fraction to the dunes, resulting in a tendency towards a positively skewed distribution. In the case studied the aeolian sand has a mean asymmetry of 0.13, the beach sand -0.11. Equivalent values for mean grain size and standard deviation are 2.51 and 0.24 (aeolian) and 2.41 and 0.37 (beach). Beach sands are therefore coarser and less well sorted than aeolian sands. -V.Gardiner

Araçatuba formation: palustrine deposits from the initial sedimentation phase of the Bauru Basin

A Bacia Bauru (Cretáceo Superior), acumulou uma seqüência sedimentar continental essencialmente arenosa. Numa fase inicial desértica, o seu substrato basáltico foi soterrado por extensa e monótona cobertura de areias eólicas com intercalações subordinadas de depósitos de loesse. O relevo original do substrato favoreceu a formação de uma drenagem regional endorrêica, sob clima semi-árido, propiciando assim condições de formação do Paleopantanal Araçatuba. Os depósitos paludiais (Formação Araçatuba) constituem estratos tabulares de siltitos e arenitos de cor cinza claro esverdeado típica, eventualmente cimentados por carbonato de cálcio. Moldes e pseudomorfos de cristais de gipsita e dolomita foram identificados na unidade. Aparentemente, estão associados com gretas de ressecação, marcas de raízes e intervalos com laminação tipo climbing ripple, que indicam ambiente de águas salinas rasas e relativamente calmas, submetidas a fases de exposição subaérea e ressecação. Nos limites da área de ocorrência da Formação Araçatuba, as unidades arenosas podem exibir feições sigmóides e estratificação contorcida, comuns em depósitos deltaicos marginais. A Formação Araçatuba é contornada e posteriormente encoberta por depósitos eólicos da Formação Vale do Rio do Peixe.

Empobrecimento e podzolização de solos lateríticos da bacia do Rio Negro e gênese dos podzóis na alta Bacia da Amazônia

Pós-graduação em Geografia - IGCE

Morphology and surface sedimentation on the upper and middle continental slope off Uruguay

This paper presents for the first time a morphological and surface sediment characterization of the Uruguayan outer continental shelf and slope. The study is based on a high-resolution coverage using hydrographical, geomorphological and sedimentological sampling and several textural and productivity proxies. Along slope terraces and an important canyon system characterizes continental slope morphology, indicating that across- and down-slope sedimentary processes control large-scale sedimentation. Terraces represent the prolongation of the Argentinean Contouritic Depositional System that vanishes in the study area, presumably as a result of the dynamic of the Brazil-Malvinas confluence. Canyons incised in the upper slope are likely related to low-stand sea level conditions. At the outer shelf and shallow upper slope (170-250 m depth), off-shelf sand transport is inferred from the distribution of relict sand and reworked biogenic gravel. In the upper continental slope, the northern region is characterized by an erosive environment controlled by a steep slope and the southward flowing Brazil current. In the south, a depositional environment is enhanced by the presence of a gentler slope and seaward incised canyons and is mainly controlled by hemipelagic processes associated with nutrient-rich Sub-Antarctic Waters (SAW), by its confluence with South Atlantic Central Waters (SACW) and by the Rio de la Plata’s (RdlP) influence. Additionally, within the upper slope, the occurrence of igneous-metamorphic cobbles and pebbles in canyon and mound lag deposits suggests the influence of glacial fluvial discharge and/or iceberg transport processes. In the middle slope, sedimentation is controlled by thermohaline-induced deep-water bottom currents. The decreasing influence of the erosive Antarctic Intermediate Water (AAIW) is evident in a northward diminution in grain size. The variety of transport and sedimentary processes identified reflect the control of the Brazil-Malvinas confluence zone and the Rio de la Plata’s discharge.