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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Incidencia económica de la degradación del suelo por erosión eólica : el caso de los sistemas productivos de la estepa pampeana semiárida

Lorda, Héctor 14 May 2009 (has links)
El suelo es uno de los componentes principales de los agro-ecosistemas (capital natural), que junto a las demás formas de capital, brindan servicios ecológicos (SE) destinados a las necesidades y bienestar humanos. La Región Semiárida Pampeana (RCP), en la Provincia de La Pampa, posee suelos poco desarrollados, recibe escasas lluvias y vientos de moderados a fuertes. Estas condiciones son propicias para el proceso de erosión eólica potencial, es decir la pérdida de suelo por acción del viento. Esta pérdida implica la reducción de la fertilidad física y química, con la consecuente reducción en el flujo de los SE. Las condiciones de manejo del suelo, definen la erosión eólica actual, la cual puede cuantificarse experimentalmente. Adicionalmente, se puede determinar la composición química de estos residuos. El avance de la agricultura, la intensificación de los sistemas productivos y prácticas de laboreo tradicionales inapropiados, hacen de este fenómeno un proceso irreversible, cuando se supera valores umbrales considerados moderados. Se expresa en toneladas por hectárea (t/ha). El productor no considera entre sus costos de producción, los SE del suelo que esta utilizando, los que toma de un stock inicial y sobre los que tampoco existe un precio de mercado de referencia. Una de las hipótesis de trabajo fue que las pérdidas por erosión actual, en rotaciones y en el ciclo de los cultivos agrícolas, pueden alcanzar niveles moderados a severos. La incorporación en los costos directos de cultivos agrícolas, del nitrógeno (N) y fósforo (P) involucrados en el material erosionado, por su magnitud puede causar niveles de quebranto en el margen bruto (MB) final. El costo de reemplazo de estos nutrientes se lo denominó Indicador Ambiental (IA) y se estimó, monetariamente, a través de su equivalente en nutrientes de fertilizantes. Otra hipótesis planteada, sugiere que es posible plantear actividades tecnológicamente superadoras, que reduzcan los niveles de erosión, mejoren el balance de algunos nutrientes esenciales y que se integren en un sistema productivo ambiental y económicamente sustentable. Para estimar la tasa de erosión eólica, se utilizó el modelo empírico identificado en castellano con las siglas EWEQ (Wind Erosion Equation), el cual fue cargado con secuencias de cultivos reales (rotaciones), con longitud de tiempo variables y para 6 sitios de la estepa pampeana: 3 sitios de la denominada Subzona Castex (Castex Norte, Castex Sur-Santa Rosa y Castex Sur-Anguil); 2 sitios de la Subzona Pico (Pico Norte y Pico Sur) y 1 sitio de la Subzona Guatrache. El modelo devuelve la tasa de erosión promedio anual de toda la rotación, como también la tasa de erosión del ciclo de cada cultivo agrícola (t/ha ciclo), aprovechando el detalle en las fecha precisas entre operaciones. Con estos registros, se estimaron los costos directos de todos los ciclos disponibles de trigo, girasol, soja y maíz. Utilizando los precios de insumos y productos de Febrero de 2008, se calculó la incidencia del IA, en los costos directos y sus efectos en el MB final. El plan de optimización se realizó para las condiciones agroclimáticas, dimensiones y caracterización de sistemas productivos del Sitio Castex Norte (Subzona Castex), a través de una matriz de programación lineal (PL). Se diseñaron previamente los planteos técnicos basados en tecnologías disponibles, los resultados económicos (MB) y el balance de N, P y carbono orgánico (CO) de cada actividad. La tasa de erosión eólica estimada para cultivos en siembra convencional (SC) en la primera parte, fue un insumo directo de la matriz, utilizada como restricción ambiental. Las pérdidas de N y P involucradas por esta vía, formaron parte de los egresos, dentro del balance de nutrientes. Fue necesario simular en el EWEQ, aquellas alternativas tecnológicamente mejoradas, no disponibles entre los registros reales y donde predominó la siembra directa (SD) y estrategias de fertilización. También se estimaron los índices para algunos de los recursos forrajeros de la actividad ganadera (invernada). Se puso énfasis en las restricciones ambientales, mientras que desde lo técnico-agronómico no hubo limitaciones en las restricciones de capital de trabajo ni diferenciación en el tipo de suelo. Para esta segunda etapa, se utilizaron precios de insumos de 2006 y las cotizaciones del disponible 2007 para los productos. Se detectaron menores tasas de erosión eólica en SD que en SC. En el Sitio Guatraché se redujo de 10,0 t/ha en una rotaciones en SC a 5,6 t/ha en SD (44% menos). También se redujo en más de un 50% entre ciclos de cultivos, dentro de una misma rotación, al utilizar SD. En todos los casos, significó un pasaje del grado de erosión de moderado/severo a erosión ligera. El costo de reemplazo del IA, fue variable entre cultivos, entre sistema de siembra (SD vs SC) e influenciado por el nivel de costos directos totales. En los cultivos conducidos en SC, con tasas de erosión eólica cercanas y levemente superiores a 8 t/ha ciclo, la participación del IA fue de 20 a 40 % en trigo; 15 a 25% en maíz; 20 a 35% en girasol y de 20 a 30% en soja. Con tasas de erosión 4 a 6 t/ha ciclo en SD, el IA tuvo una participación del 8% en maíz; del 8 a 16 % en trigo y del 8 a 21% en girasol. Respecto al efecto sobre el MB inicial, solo se produjeron quebrantos cuando los rendimientos de trigo fueron inferiores a 1t/ha y un caso de maíz, con una producción de 1,4 t/ha. Las actividades propuestas en la matriz de PL permitieron detectar déficits generalizados en el balance de nutrientes, en aquellos cultivos conducidos con esquemas tradicionales de manejo tecnológico y/o de escaso nivel de fertilización. Por el contrario, la actividad ganadera mostró todos los índices positivos. Sobre una explotación de 506 ha, la mejor solución de la matriz de PL quedo integrada por 143 ha de trigo en SC con aplicación de fertilizante apuntando a máximo rendimiento (TrSCDMR); 170 ha de maíz en SD y de alta producción (MaSDAP) y 193 ha de girasol en SD con fertilización de máxima respuesta (GiSDFER). Este sistema agrícola alcanzó el máximo margen bruto total (MBT) con una erosión eólica promedio anual de 4,9 t/ha. Los beneficios ambientales de la ganadería no se aprovecharon frente a un precio promedio de 2,70 $/kg de carne. Sin embargo, los costos de sustitución indicaban que la invernada podía participar con un precio de 3,46 $/kg de carne (+28%). Siendo un valor esperable dentro de la volatilidad de precios de la serie 2007/2008, se simuló un escenario mixto, donde la invernada participó con 245 ha, la misma alternativa de girasol en SD con 153 ha, y el mismo maíz de alta producción con 143 ha. Entre el sistema agrícola y el mixto, el MBT se redujo solo el 1% ($ 390.660 vs. $386.795 respectivamente). Palabras clave: erosión eólica, servicios ecológicos, programación lineal, balance de nutrientes, nitrógeno, fósforo. / Soil is one of the main components of agro-ecosystems (natural capital). Together with other forms of capital, provides ecological services (ES) for human needs and welfare. The Semi-Arid Pampas Region (SPR) has poorly developed soils, receives little rain and moderate to strong winds. These conditions are favourable for the process known as potential wind erosion, namely the loss of soil by wind action. This loss implies a reduction of both physical and chemical fertility, with consequent reduction in the flow of those ES, mentioned above. The conditions of soil management, define the current wind erosion, which can be quantified experimentally. Additionally, chemical composition of these residues can be determined. It is expressed in tons per hectare (t/ha).The advancement of agriculture, the intensification of production systems and traditional inappropriate tillage practices, generates an irreversible phenomenon, when it exceeds threshold values, considered moderate. Farmers do not consider among their production costs, the ES they are using, which they take from an initial stock. In addition, there is no price market reference. One of the working hypothesis was that losses caused by current wind erosion, in both rotations and crops cycle, can achieve moderate to severe levels. The incorporation into crops direct costs of nitrogen (N) and phosphorus (P) involved in the eroded material might produce actual gross margin (GM) losses. The replacement cost of these nutrients was named in this research as Environmental Index (EI) and it was considered, in money terms, through its equivalent in nutrients from fertilizer. Another hypothesis suggests that it is possible to raise productive activities technologically enhanced that reduces the levels of erosion, improve the balance of some essential nutrients and can be integrated into a production system, environmentally and economically sustainable. The empirical model Wind Erosion Equation (EWEQ) was used to estimate wind erosion rate. Its inputs were farmers real data, including crops seasonal sequences (rotations). Records varied in lengths of time and came from six places in the Pampas Steppe: three places in the so-called Sub-Zone "Castex" (North Castex site, South-Castex- Santa Rosa site and South Castex-Anguil site), two in the Sub-Zone "Pico" (North Pico site and South Pico site) and one site of Sub-Zone "Guatraché". The model returns the average annual erosion rate of the entire rotation, and the cycle crop erosion rate (t/ha cycle). This last rate takes advantage of the detail in the precise date information between machinery operations, within the model. These records, also allowed estimating direct costs of all the available crops cycles of: wheat, sunflower, soybeans and corn. Using inputs and commodities prices of February 2008, the incidence of EI in direct costs and its impact on the final GM, was calculated. The optimization plan was carried out for agro-climatic conditions, farm size and production systems patterns of North Castex Site (Sub-Zone "Castex"), through a matrix of linear programming (LP). Previously, technical set up approaches were designed, based on available technology, also the economic performance (GM) and the balance of N, P and organic carbon (OC) of each activity. The estimated wind erosion rate estimated for crops in the first part of the study and involving conventional tillage (CT) sowing system was a direct input for the matrix, used as environmental constraints. The concentration of N and P involved in this losses, were part of discharges within the balance of nutrients. It was necessary to use the EWEQ, to simulate those alternatives technologically enhanced, witch no records were available, and where no-tillage (NT) and fertilization strategies have been used. It was also estimated rates for some of the forage resources of livestock activity (fattening steers). Emphasis was placed on the environmental constraints, while no limitations were set from those technical-agronomic constraints such as working capital or differentiation in the type of soil. For this second stage is used pricing of inputs, 2006 and 2007 current prices of commodities. Wind erosion rates resulted lower in NT than in CT. In Site Guatraché the index varied from 10.0 t/ha year-1 in a CT rotation, to 5.6 t/ha year-1 in NT rotation (44% less). It also declined by over 50% between cycles of crops, within a single rotation, by using NT. In all cases, it was an overtaking from a moderate/severe degree of erosion to light erosion rate. The replacement cost of EI, varied between crops, between sowing system (NT vs CT) and highly influenced by the level of total direct costs. Those crops conducted in CT, with wind erosion rates nearby and slightly higher than 8 t/ha cycle-1, the EI share in costs was 20 to 40% in wheat, 15 to 25% in corn, 20 to 35% in sunflower and 20 to 30% in soybeans. With erosion rates of 4 to 6 t/ha cycle-1, in NT cycle, the EI had an 8% share of corn costs, from 8 to 16% in wheat and from 8 to 21% in sunflower. Concerning to the effect on initial GM, economic losses occurred only when the yields of wheat were lower than 1t/ha and in the case of corn, one case was found when production reached 1,4 t/ha. The proposed activities in the matrix of LP helped to detect widespread deficits in the balance of nutrients in crops those conducted with traditional patterns of technological management and/or low levels of fertilization. By contrast, livestock activity showed all positive indexes. On a farm of 506 hectares, the best solution of the matrix of LP resulted in 143 ha of CT wheat with fertilizer application aimed at maximum performance (TrSCDMR); 170 ha of NT corn and high production (MaSDAP) and 193 ha of NT sunflower with the highest expected fertilization response (GiSDFER). This "grain cropping system reached a maximum total gross margin (TGM) with an average annual wind erosion rate of 4.9 t/ha year-1. The environmental benefits of livestock are not exploited, facing an average price of 2,70 $/kg of live weight. However, the "shadow price" indicated that livestock activity might take part of the solution with a price of 3,46 $/ kg of live weight (+28%). Since this was an expected value along 2007/2008 meat market prices series, it was simulated a "crop and beefs mixed system where livestock participated with 245 ha, along with 153 ha of former NT sunflower alternative, and 143 ha of the same high production corn. When comparing the "grain cropping and "crop and beefs mixed systems, TGM decreased only 1% ($ 390,660 vs. $ 386,795, respectively).
32

Erosion éolienne dans le Damagaram Est (Sud-Est du Niger) : paramétrisation, quantification et moyens de lutte/Wind erosion in the eastern Damagaram (South-East of Niger) : parametrization, quantification and control

Tidjani, Adamou Didier 22 April 2008 (has links)
Les cuvettes du Damagaram Est (Sud-Est du Niger), sources importantes de productions alimentaires et de revenus, sont sujettes à ensablement par des sédiments éoliens. L’amplification du phénomène de la désertification au Sahel a exacerbé ce processus. L’objectif de ce travail, effectué au Nord-Ouest de Gouré, est d’évaluer l’impact de l’occupation du sol sur l’activité éolienne et l’ensablement des cuvettes d’une part, et d’autre part de tester l’efficacité d’une technique de fixation de dunes en terme de réduction des flux éoliens et de restauration écologique. Pour atteindre ces objectifs, nous avons suivi pendant 3 ans les caractéristiques du vent et l’activité éolienne ainsi que mesuré les flux de sédiments éoliens en relation avec l’évolution de la biomasse végétale. Les résultats obtenus ont montré que l’érosion éolienne sur les pâturages suit une dynamique saisonnière marquée, principalement en relation avec la dynamique temporelle de la hauteur de rugosité aérodynamique (Z0). Cette dynamique est due à l’impact de la pluviométrie et des activités pastorales et anthropiques sur la végétation herbacée. Les pâturages sur sols sableux apparaissent comme des zones potentielles de déflation au cours de la deuxième moitié de la saison sèche et pourraient ainsi contribuer à l’ensablement des cuvettes. Les tempêtes observées dans la première moitié de la saison des pluies au Sahel sont responsables d’une mobilisation importante de sédiments éoliens. L’analyse physico-chimique de ces sédiments montre globalement que les proportions de limons et d’argiles augmentent au détriment de la proportion de sables quand la hauteur de collecte augmente. Ceci s’accompagne d’un enrichissement important en nutriments (N, P, K) et en carbone. Les bilans de masse au niveau parcellaire sont globalement positifs, indiquant un apport net de sédiments, de nutriments et de carbone. Cependant, les incertitudes liées à ces bilans de masse sont très élevées. Si ces résultats semblent donc indiquer l’existence de sources de sédiments extérieures à la parcelle dans le contexte de cette étude, ils ne peuvent être interprétés comme preuve de l’absence d’érosion sur les sols dunaires à vocation pastorale. L’emploi de palissades antiérosives à base de Leptadenia pyrotechnica s’est révélé être une technique très efficace de fixation mécanique de dunes vives en zone semi-aride, permettant de réduire de plus de 95% les flux dès la première année. Elle entraîne la reprise des herbacées, tant en quantité qu’en diversité des espèces. Cette végétation renforce progressivement l’action anti-érosive. Cette technique constitue de ce fait une méthode adéquate de restauration des dunes dégradées en condition de non pâture. / The “cuvettes” of Eastern Damagaram (South-Eastern Niger), which are an important source of food and revenue, are being silted up by aeolian sediment. The amplification of the desertification phenomenon in the Sahel is exacerbating this process. The objective of this research, carried out to the North-West of Gouré, was to evaluate the impact of land use on the aeolian activity and the silting up of the cuvettes on the one hand, and on the other hand to evaluate the effectiveness of a dune fixation technique in terms of flux reduction and ecological restoration. To achieve these objectives, the wind characteristics and the aeolian activity were monitored for three years and we measured the sediment fluxes in relation to the development of the herbaceaous cover. It was shown that sediment fluxes on pasture land follow clear seasonal dynamics related to the temporal dynamics of the aerodynamic roughness length (Z0). These dynamics are due to the impact of rainfall as well as pastoral and human activities on the herbaceous vegetation. Pasture land on sandy soils appears to be a potential source of sediment during the second half of the dry season and may therefore contribute to silting up of the cuvettes. The dust storms observed during the early part of the rainy season in the Sahel are responsible for an important mobilization of aeolian sediment. The physico-chemical analysis of the sediment indicates an increase in the clay and silt content relative to the sand content as the height increases above ground. This goes together with an enrichment in nutrients (N, P, K) and carbon. The mass balances at plot level are positive overall, thereby indicating a net addition of sediment, nutrients and carbon. However, the uncertainty associated with these mass balances is very high. Although the results seem to indicate the existence of external sources of sediment in the present study, they cannot be interpreted as a definite proof of the absence of erosion on grazed dune soils. The use of windbreaks made of Leptadenia pyrotechnica proved to be a very effective mechanical dune fixation technique, reducing sediment fluxes by more than 95% as off the first year. The windbreaks resulted in a progressive recovery of the herbaceous cover, both in quantity and species diversity. The herbaceous cover reinforced the anti-erosive effectiveness of the windbreak. This technique therefore constitutes an adequate method for the restoration of degraded dunes under zero grazing conditions.
33

Kvantifikacija procesa eolske erozije na Deliblatskoj peščari / Wind Erosion Quantification Process in DeliblatoSands

Velojić Miljan 28 September 2016 (has links)
<p>Erozija predstavlja vrlo složen fizički proces u kome pod dejstvom atmosferskih sila nastaju&nbsp;destruktivne promene na povr&scaron;inskom sloju zemlji&scaron;ta. Kada je osnovni agens pokretanja&nbsp;čestica zemlji&scaron;ta vetar, govori se o eroziji vetrom ili eolskoj eroziji. Eolska erozija je&nbsp;specifičan proces koji se odvija u izrazito složenim okolnostima uzajamnog delovanja&nbsp;brojnih prirodnih i antropogenih faktora uglavnom stohastičkog karaktera, zbog čega je&nbsp;njeno istraživanje kompleksan naučno-istraživački problem.</p><p>Osnovni cilj sprovedenih istraživanja je bio da se na izabranim lokalitetima Deliblatske&nbsp;pe&scaron;čare, najvećeg i najznačajnijeg područja takve vrste u Evropi, uspostavi praćenje stanja&nbsp;procesa eolske erozije, odnosno neposrednim, sistematskim merenjima u terenskim&nbsp;uslovima ustanove količine eolskog nanosa &ndash; pronos nanosa, odrede dominantni pravci&nbsp;njegovog kretanja, defini&scaron;e njegova unutargodi&scaron;nja raspodela i utvrdi efekat vegetacije na&nbsp;smanjenje intenziteta eolske erozije. U toku četvorogodi&scaron;njeg perioda su po prvi put na&nbsp;ovim prostorima, na istom lokalitetu, sprovedena uporedna istraživanja eolske erozije&nbsp;primenom mehaničkih hvatača nanosa i metoda zasnovanih na praćenju aktivnosti&nbsp;radionuklida ve&scaron;tačkog porekla 137Cs u zemlji&scaron;tu, čije količine služe da se posebnim&nbsp;teorijskim modelima pretvore u gubitke zemlji&scaron;ta.</p><p>Praćenje procesa eolske erozije je vr&scaron;eno od 2006. do 2009. godine na lokalitetu Cvjićev vis,&nbsp;koji je izabran kao karakterističan, jer je pored centralne pozicije na Deliblatskoj pe&scaron;čari,&nbsp;obrađivani povr&scaron;inski sloj zemlji&scaron;ta bio bez za&scaron;tite od vetra. Paralelno sa ovim merenjima,&nbsp;na lokalitetu Dragićev hat &ndash; rasadnik, praćenje procesa eolske erozije vr&scaron;eno je na dva&nbsp;merna mesta u periodu od maja 2006. godine do aprila 2007. godine u uslovima postojanja&nbsp;za&scaron;titne uloge vegetacionog pokrivača i/ili vegetacionog pojasa. Merenje intenziteta eolske&nbsp;erozije je realizovano statičnim hvatačima nanosa tipa deflametar (dimanzija ulaznog&nbsp;otvora 10 x 10 cm) orijentisanih prema određenim pravacima (N, NE, E, SE, S, SW, W, NW) da bi potpuno definisali procese eolske erozije u vektorskom smislu. Kvantifikacija eolskog nanosa statičnim hvatačima stalno usmerenim prema određenim pravcima duvanja vetrova, omogućila je da se posebno evidentiraju i razlikuju &bdquo;sumarna&rdquo; produkcija eolskog nanosa (aritmetički zbir zahvaćenih količina nanosa iz svih hvatača) i &bdquo;rezultujuća&rdquo; količina eolskog nanosa (vektorski zbir), jer te veličine određuju pored ukupno pokrenute količine eolskog nanosa (produkcija nanosa) i delove nanosa koji se transportuju van granica&nbsp;erozionog polja (gubitak zemlji&scaron;ta), generalni pravac i smer njegovog kretanja.</p><p>Merenja eolske erozije na lokalitetu Cvijićev vis za period 2006-2009. godine su ukazala na&nbsp;značajne procese eolske erozije koji su definisani srednjim godi&scaron;njim pronosom nanosa od&nbsp;4,48 kg m-1. Ustanovljeno je da su ukupno zahvaćene količine nanosa na 8 hvatača bile &Sigma; =&nbsp;25,94, 20,92, 52,98 i 43,47 kg m-1 god-1, a pronosi nanosa &Sigma;&#39; (&Sigma;/8) = 3,24, 2,61, 6,62 i 5,43 kg&nbsp;m-1 god-1 u 2006., 2007., 2008. i 2009. godini respektivno.</p><p>Pronosi nanosa za period od maja 2006. do aprila 2007. godine su pokazali da je na<br />lokalitetu Cvijićev vis koga karakteri&scaron;u neobraslost i otvorenost povr&scaron;ine zabeležen najveći&nbsp;intenzitet eolske erozije na godi&scaron;njem nivou koji je 4 puta veći u odnosu na lokalitet&nbsp;Dragićev hat &ndash; rasadnik I koga karakteri&scaron;u neobraslost i za&scaron;tićenost povr&scaron;ine i 30,2 puta veći&nbsp;u odnosu na Dragićev hat &ndash; rasadnik II koga karakteri&scaron;u obraslost i za&scaron;tićenost zemlji&scaron;ta. Na&nbsp;lokalitetu Dragićev hat &ndash; rasadnik I intenzitet eolske erozije na godi&scaron;njem nivou je 7,5 puta&nbsp;veći od onog na lokalitetu Dragićev hat &ndash; rasadnik II.</p><p>Gubici zemlji&scaron;ta izraženi preko rezultujućih mesečnih pronosa nanosa (vektorski zbir)<br />iznosili su 5,13, 2,04, 4,31 i 11,94 kg m-1 u 2006., 2007., 2008. i 2009. godini respektivno, a&nbsp;procentualni udeo godi&scaron;njih gubitaka zemlji&scaron;ta u odnosu na ukupnu produkciju nanosa&nbsp;(aritmetički zbir) se kretao od 8,1% do 27,5. Rezultujući pravac kretanja eolskog nanosa u&nbsp;toku perioda istraživanja bio je jugoistok - severozapad (SE-NW) pod uticajem dominantnog&nbsp;jugoistočng vetra &bdquo;Ko&scaron;ava&rdquo;.</p><p>Iako se najpouzdanije determinisanje eolske erozije i njenih efekata postiže na osnovu&nbsp;neposrednih sistematskih merenja u realnim terenskim uslovima, počev od kraja pro&scaron;log&nbsp;veka se sve vi&scaron;e primenuju i metode praćenja radionuklida iz radioaktivnih padavina,&nbsp;posebno 137Cs, u cilju procene gubitaka zemlji&scaron;ta i prostornog rasporeda eolskog nanosa.</p><p>Ukupan broj uzetih uzoraka za metodu praćenja količina 137Cs je iznosio 149, od kojih je bilo&nbsp;9 inicijalnih uzoraka (3 profila po 3 uzorka), 14 osnovnih uzoraka (2 profila po 7 uzoraka), 32&nbsp;ostala uzorka (8 profila po 4 uzorka), 36 referentnih uzoraka (9 profila po 4 uzorka) i 58&nbsp;uzoraka uzetih zrakasto po određenim pravcima (N, NE, E, SE, S, SW, W, NW).</p><p>Osnovni uzorak na neobrađenom zemlji&scaron;tu sa detektovanom količinom 137Cs od 10.603,57&nbsp;Bq m-2 predstavlja uporednu vrednost, tj. lokalni padavinski ulaz 137Cs za modele&nbsp;pretvaranja količina 137Cs u količine izgubljenog zemlji&scaron;ta. Ovaj uzorak odslikava sredinu na&nbsp;kojoj su sprovedena istraživanja i predstavlja uporednu vrednost koja može korektno da&nbsp;defini&scaron;e procese eolske erozije.</p><p>Za pretvaranje izmerenih količina 137Cs u količine izgubljenog zemlji&scaron;ta po modelima&nbsp;Walling-a kori&scaron;ćen je najjednostavniji proporcionalni model (PM) za obrađena zemlji&scaron;ta, a&nbsp;najprimenjeniji model profilne distribucije (PDM) za neobrađena zemlji&scaron;ta u okviru najnovije verzije PC-kompatibilnog softverskog paketa u Microsoft Excel Add-Ins varijanti. Modelom profilne distribucije (PDM) za sve uzorake uzete na eksperimentalnom području dobijeni su prosečni gubici zemlji&scaron;ta od 207,06 t ha-1 god-1 i 2,10 cm. Model Basher &amp; Webb je dao prosečne gubitke zemlji&scaron;ta od 212,18 t ha-1 god-1 i 2,09 cm. Gubici zemlji&scaron;ta dobijeni modelima pretvaranja količina 137Cs u količine izgubljenog zemlji&scaron;ta ukazuju na značajne procese eolske erozije definisane jakom i ekscesivnom eolskom erozijom.</p><p>Za 58 uzoraka zemlji&scaron;ta uzetih na tačkama raspoređenih zrakasto po određenim pravcima&nbsp;(N, NE, E, SE, S, SW, W, NW), pored koncentracija i količina 137Cs i 210Pbex, određene su&nbsp;prostorne koordinate X i Y i nadmorske visine uzetih uzoraka. Prostorne distribucije&nbsp;koncentracija 137Cs i 210Pbex izražene su izolinijama, a kreiranani su i 3D prikazi u procentima&nbsp;odstupanja 137Cs i 210Pbex od lokalnog padavinskog ulaza 137Cs i 210Pbex. U oba slučaja je&nbsp;primetan dominantan uticaj pravca jugoistok - severozapad (SE-NW), odnosno jugoistočnog&nbsp;vetra &bdquo;Ko&scaron;ava&rdquo;.</p><p>Komparativna analiza ovih metoda je ukazala na validnost u kvantifikaciji procesa eolske&nbsp;erozije i mogućnost njihove primene u budućnosti, a dobijeni rezultati produkcije eolskog&nbsp;nanosa i gubitaka zemlji&scaron;ta su dali doprinos oceni stanja degradacije zemlji&scaron;ta i ugroženosti Deliblatske pe&scaron;čare.&nbsp;</p><p>&nbsp;</p> / <p>Erosion is a very complex physical process which, under the impact of atmospheric forces,&nbsp;creates destructive changes on the soil surface layer. In case the primary agent of particle&nbsp;movement is wind, we talk about wind or aeolian erosion. Aeolian erosion is a specific&nbsp;process which occurs in extremely complex situations of mutual interaction of numerous&nbsp;natural and anthropogenic factors of mainly stochastic properties making its research a&nbsp;complex scientific-research problem.</p><p>The main goal of conducted research was to monitor the process of aeolian erosion at the&nbsp;chosen localities of Deliblato Sands, the largest and the most important area of the kind in&nbsp;Europe. In other words, the goal is to determine the quantities of aeolian sediment &ndash;&nbsp;sediment transport by direct systematic measurements in field conditions, determine&nbsp;dominant direction of sediment transport, define its annual distribution and determine the&nbsp;effect of vegetation on reducing the intensity of aeolian erosion. During a four-year period,&nbsp;for the first time in this area, i.e. at the same locality, a comparative research of aeolian&nbsp;erosion have been conducted using the mechanical sediment trap and activities based on&nbsp;137Cs radioisotope tracing technique for estimating soil losses using special theoretical&nbsp;models.</p><p>The monitoring of aeolian erosion processes was conducted during the period 2006 &ndash; 2009&nbsp;at Cvijićev vis which was chosen as a typical locality since it was, apart from the central&nbsp;position on Deliblato Sands, a cultivated surface without any wind protection. Alongside&nbsp;with these measurements, at Dragićev hat &ndash; nursery garden, the monitoring of aeolian&nbsp;erosion was conducted on two measurement points during the period May 2006 &ndash; April&nbsp;2007 in areas with the protective vegetative covers and/or vegetative belts. Aeolian erosion&nbsp;intensity measurement was performed by static sediment traps of the type &ldquo;deflametre&rdquo;&nbsp;(dimension of entry opening 10 x 10 cm) oriented on certain directions (N, NE, E, SE, S, SW,&nbsp;W, NW) in order to define the aeolian erosion processes in vector terms. The quantification&nbsp;of aeolian sediment using static traps constantly facing certain wind blowing directions enabled to log and differentiate &ldquo;summary&rdquo; yield of aeolian sediment (arithmetic sum of all sediment quantities from all traps) and &ldquo;resulting&rdquo; quantity of aeolian sediment (vector sum), since those quantities determine not only the entire amount of transported aeolian sediment (sediment yield) but also the sediment transported outside the areas of erosion field (soil loss), bur also the general direction of its transport.</p><p>Aeolian erosion measurement on Cvijićev vis for the period 2006 &ndash; 2009 indicated the<br />significant aeolian erosion processes which were defined by medium annual ediment<br />transport of 4.48 kg m-1. It has been determined that the total quantities of moved<br />sediment were 25.94, 20.92, 52.98 and 43.47 kg m-1 year-1, and sediment transport 3.24,&nbsp;2.61, 6.62 and 5.43 kg m-1 year-1 in 2006, 2007, 2008 and 2009 respectively.</p><p>Sediment transport for the period May 2006 &ndash; April 2007 showed that on Cvijićev vis which&nbsp;is characterized by bareness and openness there was the biggest aeolian erosion &ndash; four&nbsp;times bigger compared to Dragićev hat &ndash; nursery garden I characterized by bareness and&nbsp;protectiveness and 30.2 times bigger compared to Dragićev hat &ndash; nursery garden II&nbsp;characterized by overgrown condition and protectiveness of erosive field. At the locality&nbsp;Dragićev hat &ndash; nursery garden I the aeolian erosion was recorded 7.5 times bigger&nbsp;compared to the one recorded on Dragićev hat &ndash; nursery garden II.</p><p>Soil loses expressed through the resulting monthly sediment transport (vector sum)<br />equalled 5.13, 2.04, 4.31 and 11.94 kg m-1 in 2006, 2007, 2008 and 2009 respectively, and&nbsp;the percentage share of annual soil losses compared to total sediment yield (arithmetical&nbsp;sum) varied between 8.1% and 27.5%. The resulting aeolian sediment movement direction&nbsp;was SE-NW under the influence of the dominant southeast wind &ldquo;Koshava&rdquo;.</p><p>Even though the most reliable determination of aeolian erosion and its effects is based on&nbsp;direct systematic measurements in real time conditions in the field, starting from the end&nbsp;of the last century the methods of tracking radionuclide from radioactive precipitation,&nbsp;especially 137Cs, for the purposes of estimating the soil loss and spatial distribution of&nbsp;aeolian sediment, have been used increasingly.</p><p>The total number of samples taken for the method of monitoring the quantity of 137Cs was&nbsp;149, 9 of which were initial samples (3 profiles with 3 samples each), 14 main samples (2&nbsp;profiles with 7 samples each), 32 remaining samples (8 profiles with 4 samples each), 36&nbsp;reference samples (9 profiles with 4 samples each) and 58 samples taken radially on certain&nbsp;directions (N, NE, E, SE, S, SW, W, NW).</p><p>The main sample taken from the uncultivated land with the detected quantity of 137Cs of&nbsp;10,603.57 Bq m-2 represents the comparative value, i.e. local precipitation input of 137Cs for&nbsp;the models of 137Cs quantities conversion into the quantities of lost soil. This sample depicts&nbsp;the area where the research was conducted and represents the comparative value which&nbsp;can properly define the aeolian erosion processes.</p><p>For converting the measured quantities of 137Cs into the quantities of lost soil using Walling&nbsp;model the simplest proportional model (PM) for cultivated land was used and the most&nbsp;appropriate profile distribution model (PDM) for uncultivated soil with the newest version&nbsp;of PC compatible software package in Microsoft Excel Add-Ins. Using the profile distribution model (PDM) on all samples taken from the experimental area the quantities of average soil loss obtained were 207.06 t ha-1 year-1 and 2.10 cm. Basher &amp; Webb model gave the average soil loss of 212.18 t ha-1 year-1 and 2.09 cm. Soil loss calculated using the conversion of 137Cs quantities into the soil loss quantities indicate the significant aeolian processes defined by strong and excessive aeolian erosion.</p><p>For 58 soil samples taken from areas radially distributed on certain directions (N, NE, E, SE,&nbsp;S, SW, W, NW), apart from 137Cs and 210Pbex concentrations and quantities, spatial&nbsp;coordinates X and Y were determined as well as the altitude of taken samples. Spatial&nbsp;distribution of 137Cs and 210Pbex quantities are represented by isolines, and also 3D&nbsp;demonstrations were created showing the percentage of deviation of 137Cs and 210Pbex from&nbsp;the local precipitation input of 137Cs and 210Pbex. In both cases, the dominant direction SENW&nbsp;was noticeable, i.e. the southeast wind &ldquo;Koshava&rdquo;.</p><p>The comparative analysis of these methods indicated the validity in the quantification of&nbsp;aeolian erosion process and the possibility of its application in the future and the obtained&nbsp;results of aeolian sediment yield and soil loss contributed to determining the state of soil&nbsp;degradation and vulnerability of Deliblato Sands.</p>
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Erosion éolienne de tas de stockage de matières granulaires sur sites industriels : amélioration des méthodes de quantification des émissions

Furieri, Bruno 01 October 2012 (has links)
L’érosion éolienne des matières granulaires (minerais, charbons,. . . ) est un des facteurs influençant grandement la qualité de l’air dans l’environnement proche de nombreux sites industriels. L’objectif principal de ce travail est l’amélioration des méthodologies de quantification des émissions des sources diffuses, notamment à partir d’une meilleure prise en compte de l’exposition éolienne des sources que sont les tas de stockage et des répartitions granulométriques des matières présentes sur les sites de stockage. Les observations sur sites industriels montrent que les régions proches des tas de stockage de matières granulaires sont chargées de particules de granulométries plutôt fines. Celles-ci sont susceptibles d’être remises en suspension par les structures tourbillonnaires générées par le vent incident. Ainsi, ces zones d’envol potentiel ont fait l’objet d’analyses afin de quantifier leur contribution aux émissions globales. Une technique de visualisation d’écoulement pariétal, associée à des simulations numériques tridimensionnelles, ont été mises en oeuvre pour mieux comprendre ces structures de l’écoulement. Les matières granulaires sont un mélange de particules érodibles et non-érodibles. Le caractère érodible étant lié aux propriétés des particules (principalement granulométrie et masse volumique), ainsi qu’à la vitesse du vent incident. Dans ce cadre, deux types d’études ont été menées: des essais expérimentaux d’envol de particules dans une soufflerie et des simulations numériques tridimensionnelles avec un logiciel open-source de mécanique des fluides (Code_Saturne). Une technique originale a ainsi été développée pour quantifier, par une pesée en continue, l’influence des particules non-érodibles sur le flux massique envolé. En parallèle, le comportement des particules sur la surface est analysé à l’aide de clichés photographiques. L’analyse de l’effet des particules non-érodibles au niveau local est réalisée grâce à des simulations numériques pour des configurations polydispersées. Les résultats présentés dans ce mémoire constituent de premiers éléments pouvant possiblement contribuer à l’amélioration des modèles actuels de quantification des émissions de particules par une meilleure intégration et pris en compte de la présence de particules non-érodibles pour les matières présentant de larges spectres granulométriques. / Wind erosion of granular materials (ores, coal, ...) is one of the factors that greatly influence the quality of the air in the immediate vicinity of many industrial sites. The main objective of this work is the improvement of methodologies for quantifying emissions from diffuse sources. It may be carried out by a better consideration of wind exposure on the sources (storage piles) and larger size distributions of granular materials present at the storage sites. Observations show that areas near storage piles of granular materials on industrial sites are loaded with silt particles. These particles may be re-emitted by vortex structures. Thus, these areas of potential particles take-off were analyzed to quantify their contribution to global emissions. A wall flow visualization technique associated with three-dimensional numerical simulations have been implemented. Granular material is a mixture of erodible and non-erodible particle. The erodible character may be associated to particle properties (mainly size and density), as well as the ambient wind speed. In this context, two types of studies were conducted: experimental tests of particles take-off in a wind-tunnel and numerical simulations with a three-dimensional open-source fluid dynamics code (Code_Saturne). An original technique has been developed to quantify, by a continuous weighing, the influence of non-erodible particles of the mass flow. In parallel, the behaviour of particles on the surface is analyzed using photographs. The analysis of the effect of nonerodible particles at local level is achieved through numerical simulations for poly-dispersed configurations. The results presented in this thesis are the first elements that can potentially contribute to the improvement of current models of quantification of particulate emissions through a better integration of the presence of non-erodible particles for materials with large particle size spectra.
35

Field-based aeolian sediment transport threshold measurement : sensors, calculation methods, and standards as a strategy for improving inter-study comparison

Barchyn, Thomas Edward, University of Lethbridge. Faculty of Arts and Science January 2010 (has links)
Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration. / xi, 108 leaves : ill. ; 29 cm
36

Développement d'un indice de vulnérabilité à l'érosion éolienne à partir d'images satellitales, dans le Bassin arachidier du Sénégal : cas de la région de Thiès.

Cissokho, Robert 07 1900 (has links)
L’érosion éolienne est un problème environnemental parmi les plus sévères dans les régions arides, semi-arides et les régions sèches sub-humides de la planète. L’érosion des sols accélérée par le vent provoque des dommages à la fois localement et régionalement. Sur le plan local, elle cause la baisse des nutriments par la mobilisation des particules les plus fines et de la matière organique. Cette mobilisation est une des causes de perte de fertilité des sols avec comme conséquence, une chute de la productivité agricole et une réduction de la profondeur de la partie arable. Sur le plan régional, les tempêtes de poussières soulevées par le vent ont un impact non négligeable sur la santé des populations, et la déposition des particules affecte les équipements hydrauliques tels que les canaux à ciel ouvert ainsi que les infrastructures notamment de transport. Dans les régions où les sols sont fréquemment soumis à l’érosion éolienne, les besoins pour des études qui visent à caractériser spatialement les sols selon leur degré de vulnérabilité sont grands. On n’a qu’à penser aux autorités administratives qui doivent décider des mesures à prendre pour préserver et conserver les potentialités agropédologiques des sols, souvent avec des ressources financières modestes mises à leur disposition. Or, dans certaines de ces régions, comme notre territoire d’étude, la région de Thiès au Sénégal, ces études font défaut. En effet, les quelques études effectuées dans cette région ou dans des contextes géographiques similaires ont un caractère plutôt local et les approches suivies (modèles de pertes des sols) nécessitent un nombre substantiel de données pour saisir la variabilité spatiale de la dynamique des facteurs qui interviennent dans le processus de l’érosion éolienne. La disponibilité de ces données est particulièrement problématique dans les pays en voie de développement, à cause de la pauvreté en infrastructures et des problèmes de ressources pour le monitoring continu des variables environnementales. L’approche mise de l’avant dans cette recherche vise à combler cette lacune en recourant principalement à l’imagerie satellitale, et plus particulièrement celle provenant des satellites Landsat-5 et Landsat-7. Les images Landsat couvrent la presque totalité de la zone optique du spectre exploitable par télédétection (visible, proche infrarouge, infrarouge moyen et thermique) à des résolutions relativement fines (quelques dizaines de mètres). Elles permettant ainsi d’étudier la distribution spatiale des niveaux de vulnérabilité des sols avec un niveau de détails beaucoup plus fin que celui obtenu avec des images souvent utilisées dans des études environnementales telles que AVHRR de la série de satellites NOAA (résolution kilométrique). De plus, l’archive complet des images Landsat-5 et Landsat-7 couvrant une période de plus de 20 ans est aujourd’hui facilement accessible. Parmi les paramètres utilisés dans les modèles d’érosion éolienne, nous avons identifiés ceux qui sont estimables par l’imagerie satellitale soit directement (exemple, fraction du couvert végétal) soit indirectement (exemple, caractérisation des sols par leur niveau d’érodabilité). En exploitant aussi le peu de données disponibles dans la région (données climatiques, carte morphopédologique) nous avons élaboré une base de données décrivant l’état des lieux dans la période de 1988 à 2002 et ce, selon les deux saisons caractéristiques de la région : la saison des pluies et la saison sèche. Ces données par date d’acquisition des images Landsat utilisées ont été considérées comme des intrants (critères) dans un modèle empirique que nous avons élaboré en modulant l’impact de chacun des critères (poids et scores). À l’aide de ce modèle, nous avons créé des cartes montrant les degrés de vulnérabilité dans la région à l’étude, et ce par date d’acquisition des images Landsat. Suite à une série de tests pour valider la cohérence interne du modèle, nous avons analysé nos cartes afin de conclure sur la dynamique du processus pendant la période d’étude. Nos principales conclusions sont les suivantes : 1) le modèle élaboré montre une bonne cohérence interne et est sensible aux variations spatiotemporelles des facteurs pris en considération 2); tel qu’attendu, parmi les facteurs utilisés pour expliquer la vulnérabilité des sols, la végétation vivante et l’érodabilité sont les plus importants ; 3) ces deux facteurs présentent une variation importante intra et inter-saisonnière de sorte qu’il est difficile de dégager des tendances à long terme bien que certaines parties du territoire (Nord et Est) aient des indices de vulnérabilité forts, peu importe la saison ; 4) l’analyse diachronique des cartes des indices de vulnérabilité confirme le caractère saisonnier des niveaux de vulnérabilité dans la mesure où les superficies occupées par les faibles niveaux de vulnérabilité augmentent en saison des pluies, donc lorsque l’humidité surfacique et la végétation active notamment sont importantes, et décroissent en saison sèche ; 5) la susceptibilité, c’est-à-dire l’impact du vent sur la vulnérabilité est d’autant plus forte que la vitesse du vent est élevée et que la vulnérabilité est forte. Sur les zones où la vulnérabilité est faible, les vitesses de vent élevées ont moins d’impact. Dans notre étude, nous avons aussi inclus une analyse comparative entre les facteurs extraits des images Landsat et celles des images hyperspectrales du satellite expérimental HYPERION. Bien que la résolution spatiale de ces images soit similaire à celle de Landsat, les résultats obtenus à partir des images HYPERION révèlent un niveau de détail supérieur grâce à la résolution spectrale de ce capteur permettant de mieux choisir les bandes spectrales qui réagissent le plus avec le facteur étudié. Cette étude comparative démontre que dans un futur rapproché, l’amélioration de l’accessibilité à ce type d’images permettra de raffiner davantage le calcul de l’indice de vulnérabilité par notre modèle. En attendant cette possibilité, on peut de contenter de l’imagerie Landsat qui offre un support d’informations permettant tout de même d’évaluer le niveau de fragilisation des sols par l’action du vent et par la dynamique des caractéristiques des facteurs telles que la couverture végétale aussi bien vivante que sénescente. / Wind erosion is an environmental issue among the most critical one in arid, semi-arid and dry sub-humid regions of the planet. Soil erosion accelerated by the wind action causes damages both locally and regionally. Locally, wind erosion decreases the soil nutrients by the mobilization of finer particles and organic matter. This mobilization is one of the causes of lost of soil fertility with lead to the drop in agricultural productivity and to the reduction of the topsoil depth. Regionally, dust storms raised by the wind have a significant impact on population health and infrastructure because of particles deposition. In areas where soils are frequently submitted to wind aggressions, studies are urgently required in order to spatially characterize the soils according to their degree of vulnerability. Such characterization is important for many reasons, especially for administrative authorities who must decide what action to undertake in order to preserve and conserve the agricultural potentialities of soils, often with limited financial resources available. However, in some regions, as in our study area, the region of Thiès in Senegal, such studies are lacking. In fact, in regions where soil erosion is active, the studies undertaken are much localized because of their approaches (soil erosion models) which require a substantial amount of data for short intervals of time to "capture" the spatial variability of the dynamics of the factors involved in the process of wind erosion. The availability of these data at a regional level is particularly problematic in developing countries because infrastructures and resources to support continuous monitoring of environmental variables are not always available. The approach in this research aims to fill this gap, mainly through satellite imagery and more particularly those provided by Landsat-5 and Landsat-7. Landsat images cover almost the entire optical spectrum (visible, near/mid/thermal infrared) at resolutions which allow to characterize spatially the soils, according to their vulnerability at a finer level (decametric resolution) than what is possible with satellite imagery often used in environmental studies (AVHRR images from the NOAA satellite series) with a kilometric resolution. In addition, the full archive of Landsat-5 and -7 covering more than 20 years is now easily accessible. This is an undeniable asset in order to study the dynamics of the process affecting soils vulnerability to wind erosion. Taking into account the parameters used in wind erosion models (climate, soil, vegetation), we have identified those we can estimate from satellite imagery either directly (e.g. fractional vegetation cover) or indirectly (e.g. characterization of soils by their degree of degradation). Using Landsat images acquired during to the two seasons of the region (rainy and dry season) as well as climatic data and the existing low scale soil map of the region, we developed a database describing the environmental conditions from 1988 to 2002. These data were then considered as inputs (criteria) in an empirical model we made, by modulating the impact of each criterion (weight and score). By this model, we created maps showing the degree of vulnerability (vulnerability index) of the region by date according to Landsat image acquisition date. Several tests are done to validate the internal consistency of the model. To evaluate the dynamic of the erosion process for the period we studied, we have compared our maps. Our principal conclusions are as follows: 1) the proposed model has a good internal consistency and is sensitive to spatial and temporal variation of the factors taken into consideration; 2) as expected, among the factors used to explain soil vulnerability, erodibility and fractional green vegetation cover are the most important; 3) these two factors present a high intra and inter-season variation so that it is difficult to bring out long term trends even if some parts of the territory (North and East) have high vulnerability indices regardless of season; 4) the diachronic analysis of vulnerability index maps shows seasonal trend because areas with low vulnerability indices are increasing in rainy season, when the surface moisture is higher and vegetation is particularly active, and significantly decrease in dry season; 5) as expected, susceptibility, or the impact of wind on vulnerability, is stronger when the wind speed is high and vulnerability is high. In areas where vulnerability is low, an increase in wind speed has less impact. In our study we have also included a comparative analysis of some factors derived from Landsat images and from the hyperspectral sensor of the experimental satellite HYPERION. Even if spatial resolution of the images provided by both sensors is similar, the accuracy of factors extracted from the hyperspectral images is definitely higher. This is due to the spectral resolution of the sensor which permits the selection of appropriate bands with the highest level of interaction with the factor of interest. This comparative study shows that in the near future, the accessibility to this type of images will improve the calculation of the index of vulnerability by our model. For now, Landsat imagery provides very interesting information to monitor the process of soil erosion by wind.
37

Développement d'un indice de vulnérabilité à l'érosion éolienne à partir d'images satellitales, dans le Bassin arachidier du Sénégal : cas de la région de Thiès

Cissokho, Robert 07 1900 (has links)
No description available.
38

Analýza ochranných funkcí lesních porostů tvořených rychle rostoucími dřevinami. / Analyse of protective functions of forest crops totalled by the fast-growing timber species

HOMOLKA, Lukáš January 2009 (has links)
The goal of thesis is an analyse of protective functions of fast-growing timber species and a set of theirs part in the total non-energic meaning. The meaning of these timber species is very wide. The analyse is focused on first of all ameliorative function, and on sinking of wind erosion impact, then on insulating function, containing appreciation of impact on sinking of noisiness and catch of dustiness in an environment, and sanitation function which is represented by the production of oxygen.
39

Wind erosion modelling system parameters to determine a practical approach for wind erosion assessments

Liebenberg-Enslin, Hanlie 15 July 2014 (has links)
Ph.D. (Geography) / The focus of Aeolian research has mainly been on wind-blown dust from desert and arid areas. Numerous dust emission schemes have been developed over the years aimed at accurately estimating dust emission rates from various soil types and land use surfaces. Limited research has been done on wind-blown dust from smaller area sources – such as mine tailings and ash storage facilities. Lately, the concern about the environmental and health impacts, caused by dust from mine tailings storage facilities and ash disposal sites, has become more prominent, calling for better methods in determining dust emissions and their related impacts. This thesis established a practical approach for wind-blown dust emissions estimation and dispersion modelling from mine waste and ash storage facilities for the purpose of legal compliance assessment. Extensive research on the physics of wind erosion has been done over the past decade, compelling the re-evaluation of previously applied techniques. The latest and most widely applied dust emission schemes are evaluated to determine, through systematic testing of parameterisation and validation, using empirical mine waste and coal ash data, a best-practice prescription for quantifying wind-blown dust emissions and determining effects on a local scale using commercially available dispersion models. The applicability of two dust-flux schemes, (one developed by Marticorena and Bergametti (1995) and the simplified Shao 2004 scheme, as reported in 2011) for the quantification of wind-blown dust emissions, were tested using site specific particle size distribution data, bulk density and moisture content from six gold- and one platinum- tailings storage facilities and from two ash storage facilities. The availability of the required input parameters and the uncertainty associated with these parameters, were tested. The dependency of the Shao et al. (2011) model on plastic pressure (P) and the coefficient cy, both of which are not easily determined, added to the uncertainty of the emission rates. In this study, P and cy were both interpolated using the range limits provided by Shao (2004) for natural soils. By calculating P, using the salt and calcium carbonate content, similar values were obtained. The minimally disturbed dust fraction, as required by the Shao et al. (2011) scheme were derived from particle size distribution analysis but found to be more representative of the fully disturbed particle size faction (𝜂fi) and therefore needed to be corrected to represent the minimally disturbed particle size faction (𝜂mi) through the application of a correction factor, CF𝜂mi. Specific attention was given to the quantification of the threshold friction velocity (u*t) and the threshold velocities (u*), and how these two parameters relate to each under variable wind speed and time durations. This was tested using sub-hourly averaged meteorological data, one set reflected 5-minute intervals and the other 10-minute intervals. Dependent on the frequency and strength of the sub-hourly wind gusts, the resulting dust-flux rates were found to vary significantly when based on hourly averaged wind data in comparison with 5- and 10-minute wind data. Dispersion models are useful tools in air quality management. Whereas ambient monitoring provides actual ambient concentrations for specific pollutants at set locations, atmospheric dispersion models can be used to simulate any number of pollutants and determine the impacts at any location within the modelling domain. These dust-flux schemes of Marticorena and Bergametti (1995) and Shao et al. (2011) have been coupled with the US EPA regulatory Gaussian plume AERMOD dispersion model for the simulation of ground level concentrations resulting from wind-blown dust from mine tailings facilities. For this study, two Case Studies were evaluated; one included two of the gold mine tailings and the second focused on the platinum tailings. Simulated ambient near surface concentrations were validated with ambient monitored data for the same period as used in the model. For the Marticorena and Bergametti (1995) dust-flux scheme, only z0 had to be adjusted to provide a good fit with measured data – whereas the Shao et al. (2011) scheme resulted in significantly higher concentrations, resulting in an over-prediction of the measured data. By applying the correction factor, CF𝜂mi, to the minimally disturbed dust fraction, the predicted concentrations improved considerably. The coupling of the dust-flux schemes with a regulatory Gaussian plume model provided simulated ground level PM10 concentrations in good agreement with measured data. The best correlation was found under conditions of high wind speeds when the prevailing wind was from the direction of the tailings storage facility. This thesis demonstrates that simulated impacts from complex source groups can be performed, within an acceptable range of certainty, using widely applied dust-flux schemes. These dust-flux schemes, developed primarily for large-scale desert and arid areas, have been demonstrated to be applicable also to small-scale sources, of the order of 1 km2, and can be coupled to regularly available dispersion models for impact evaluations of wind-blown dust. The value of this improved approach to the mining and mineral processing industries are substantial, allowing for more accurate health risks and adverse environmental assessments from wind-blown dust from large material storage piles, a source category that has hitherto been difficult to quantify.
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Characterising and mapping of wind transported sediment associated with opencast gypsum mining

Van Jaarsveld, Francis 03 1900 (has links)
Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008. / This study aims to provide a practical tool for the prediction and management of dust generated by the activities of an opencast mining operation. The study was conducted on opencast gypsum mines in the semi-arid environment of the Bushmanland, 90 km north of Loeriesfontein in the Northern Cape Province from April 2000 to October 2007. The vertical and horizontal components of wind transported sediment were sampled and a dust settling model was designed to predict the settling pattern of dust generated by opencast mining operations. The model was applied to soil samples collected from an area surrounding a mine. The influence sphere of the mining operation was predicted by the application of the model and then mapped. Once the influence sphere is mapped, the dust influence can be managed with the aid of an onsite weather station. By further applying the predictions based on climatic data, the influence sphere can be modelled. The model is not only applicable to the planning phase of an opencast mine to plan the position of dust sensitive areas like the living quarters, office buildings and workshops etc., but also to indicate the historical impact that a mining operation had once a quarry on an active mine is worked out and rehabilitated or a mine is closed. The model application can also aid with the explanation and visual or graphic representation of the predicted impact of planned mining operations on communities or neighbouring activities to them and thus avoid later penalties.

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