• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 180
  • 83
  • 36
  • 10
  • 8
  • 8
  • 7
  • 7
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 403
  • 80
  • 75
  • 65
  • 63
  • 62
  • 46
  • 45
  • 36
  • 36
  • 35
  • 31
  • 31
  • 29
  • 29
  • 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.
241

Mobilité des métaux dans les systèmes sol-plante-biochar / Mobility of metals in soil-plant-biochar systems

Rees, Frédéric 10 December 2014 (has links)
Les biochars sont au cœur de la lutte contre les changements globaux. Ils constituent aussi un enjeu pour la gestion durable des sols contaminés. Ces travaux ont été conduits afin de mieux comprendre les effets du biochar sur la mobilité des métaux dans les sols et leur transfert vers les plantes. Une série d’expériences de complexité croissante ont été conduites, impliquant un biochar obtenu par pyrolyse de bois à 450 °C, et deux sols, l’un acide et l’autre alcalin, contaminés par Cd, Pb et Zn suite à l'activité d'une fonderie. Une gamme d’espèces végétales aux réponses contrastées vis-à-vis des métaux a été testée. Des essais de sorption en batch et de lixiviation en colonnes couplés à une caractérisation microscopique et spectroscopique du biochar ont été réalisés, ainsi que des expériences de croissance végétale en vases de végétation, en rhizotrons et en lysimètres. Les résultats démontrent que les phases minérales carbonatées du biochar jouent un rôle prépondérant dans l'immobilisation des métaux. Elles interviennent dans la sorption directe des métaux à la surface du biochar par co-précipitation. Leur dissolution contribue également à l'augmentation du pH du sol, conduisant à une rétention accrue des métaux à la surface des particules du sol. Le biochar modifie le transfert des métaux vers la plante en diminuant la disponibilité des métaux, mais également en diminuant la mobilité de cations majeurs et en modifiant la surface racinaire développée par la plante. Une diminution du transfert du métal vers les parties aériennes de la plante a généralement été observée avec Lolium perenne ou Zea mays, alors qu'une augmentation du prélèvement de Cd et Zn par l'hyperaccumulateur Noccaea caerulescens a été mise en évidence. En conclusion, le biochar contrôle la mobilité des métaux dans les systèmes sol-plante grâce à une série de mécanismes différents. Au plan pratique, le biochar favorise les stratégies de phytostabilisation et de phytoextraction des métaux dans les sols contaminés / Biochars play a central part in the mitigation of global changes. They also represent a challenge for the sustainable management of contaminated soils. This work was conducted in order to better understand the effects of biochar on the mobility of metals in soils and their uptake by plants. A range of experiments was set up following a gradual increase of complexity, with a wood-derived biochar obtained by pyrolysis at 450 °C and two soils, acidic or alkaline, contaminated by Cd, Pb and Zn from smelter activity. Various plant species with contrasting response to metals were tested. Batch sorption and column leaching experiments coupled to microscopic and spectroscopic characterization of biochars were conducted, together with plant growth experiment in pots, rhizoboxes and lysimeters. Results demonstrate that biochar's carbonated mineral phases play a dominant role in the immobilization of metals. They lead to metals direct sorption on the surface of biochar by co-precipitation. Their dissolution also contributes to the increase of soil pH, leading to an increased retention of metals on soil particles. Biochar alters the transfer of metals to the plants by decreasing the availability of metals, but also by decreasing the mobility of major cations and by modifying root surface. A decrease of metal transfer to the shoots was generally observed with Lolium perenne or Zea mays, while an increase of the uptake of Cd and Zn by the hyperaccumulator Noccaea caerulescens was evidenced. In conclusion, biochar controls the mobility of metals in soil-plant systems through a range of different mechanisms. From a practical point of view, biochar promotes both strategies of phytostabilization and phytoextraction of metals in contaminated soils
242

Effet de la végétation sur la mobilité de l’arsenic dans la rhizosphère. / The effect of vegetation on Arsenic mobilization in the rhizosphere.

Obeidy, Carole 13 May 2011 (has links)
La pollution des sols par l’Arsenic (As) est une préoccupation environnementale grandissante dans plusieurs pays du monde : États-Unis, Canada, Mexique, Chine, Vietnam et France. L’émergence des techniques écologiques dites « phytoremédiation » constitue à l’heure actuelle une des solutions aux problématiques de décontamination des sols pollués par l’As. Aussi, elle permet de rallier le respect de l’état écologique des sites d’une part et le coût financier de traitement d’autre part. Pour cela, l’appréhension des interactions entre le végétal et l’As à l’interface racine-sol est nécessaire afin d’accélerer la mise en place de la phytoremédiation et de tester son efficacité. D’où l’objectif général de ce travail est d’étudier l’effet de quatres espèces végétales Holcus lanatus, Dittrichia viscosa, Lotus corniculatus et Plantago lanceolata sur la mobilité de l’As dans un sol à contamination géochimique en As (2000 mg kg-1). Notre étude a permis au départ de comparer et de caractériser la tolérance et la capacité accumulatrice des espèces séléctionnées à l’égard de l’As en milieu de culture et en sol contaminé chimiquement par l’As. Ensuite, l’étude de la mobilisation de l’As dans la rhizosphère a été réalisée par deux approches d’étude complémentaires : l’approche « rhizopot-rhizons » et l’approche « tapis racinaire ». L’approche « rhizopot-rhizons » nous a permis d’identifier d’intéressantes corrélations entre l’As et les paramètres suivis (NO3-, SO42- , Ca, Mg, P, pH, COD) tout au long de la période de croissance. Nous avons identifié et caractérisé plusieurs processus ifluençant la mobilisation de l’As dans la rhizosphère (alcalinisation/acidification, compétition anionique…). L’avantage de l’approche « rhizopot-rhizons » réside dans le fait que les plantes se sont développées sans prétraitement du substrat de croissance (contamination artificielle, ajout de solutions nutritives…). Par ailleurs, l’approche « tapis racinaire » a permis d’identifier quelques anions organiques dans les racines de P. lanceolata et de mettre en évidence le rôle du Phosphore dans la mobilisation de l’As dans la rhizosphère. Elle permet d’amplifier l’effet du système racinaire sur la mobilité de l’As dans le sol d’une part, et de récupérer entièrement le système racinaire tout en limitant les artefacts liés à la contamination des racines par le sol d’autre part. / The pollution of soils with Arsenic (As) is an increasing environmental concerns in several countries in the world: USA, Canada, Mexico, China, Vietnam and France. Recently, the emergence of green technologies sush as “phytoremediation” is considered an attractive soil remediation strategy due to its low cost and soil preservation. For this reason, the understanding of interactions between plants and As at the soil-root interface is necessary in order to accelerate phytoremediation implementation and to test its effectiveness. Hence the aim of this work was to study the effect of four plant species Holcus lanatus, Dittrichia viscosa, Plantago lanceolata and Lotus corniculatus on As mobility in a natural As contaminated soil (up to 2000 mg kg-1). First, we compared and characterized the tolerance behaviour of the four selected species to As and their accumulation capacity in hydroponic and in natural soil conditions. Then, the study of As mobilization in the rhizosphere was conducted by using two approaches "rhizopot-rhizons” and "root mat”. We identified by the “rhizopot-rhizons” approach, some interesting correlations between As and the monitored parameters (NO3-, SO42-, Ca, Mg, P, pH, COD) over the vegetative growing period. We observed several processes affecting As mobilization in the rhizosphere (alkalization / acidification, anionic competition ...). The advantage of this approach is that the plants have grown normally without growth substrate pretreatment (artificial contamination, addition of nutrient solutions ...).Whereas, the "root mat" approach allowed the identification of some organic anions in the root system of P. lanceolata and highlighted the role of phosphorus on As mobilization due mainly toto the easy roots collection at the end of experiment.
243

Bioacumulação e translocação de manganês em Sinapis alba e Brassica juncea sob doses crescentes deste metal no solo: uma alternativa de fitorremediação

Gervasio Mariano Rufino 18 September 2006 (has links)
O objetivo do presente estudo foi avaliar a capacidade das espécies de mostarda Sinapis alba e Brassica juncea quanto à capacidade de bioacumulação e translocação de manganês, visando conhecer seu potencial de utilização para fitorremediação de solos. O experimento foi realizado em casa de vegetação na Universidade de Taubaté (UNITAU), no campus das Ciências Agrárias, utilizando Latossolo Vermelho Amarelo de classe textural franco argiloso, nas dosagens de 0, 50, 100, 200, 300, 450, 600 e 800 mg kg-1 de Mn, ajustados através de solução de MnSO4.4H2O. Após 50 dias da semeadura foi feita a colheita, lavagem, secagem e moagem da biomassa, e determinação de Mn na parte aérea e raiz. A produção de biomassa mostrou uma correlação negativa com os teores de Mn no solo, tendo a partir da dose de 200 mg kg-1 o crescimento severamente afetado tornando visíveis os sintomas de toxicidade como: manchas amarronzadas de necrose, encarquilhamento das bordas das folhas e perda da cor verde (clorose). A massa seca da parte aérea apresentou diferença significativa entre os tratamentos e na interação tratamento-espécie, sendo a Brassica juncea superior nas doses de 200 e 300 mg kg-1. A produção de massa seca de raiz também mostrou correlação negativa com os teores de Mn no solo, diferença significativa entre os tratamentos e entre as espécies sendo a Brassica juncea superior a Sinapis alba. A bioacumulação de Mn na parte aérea mostrou correlação positiva com o teor de Mn no solo e diferença estatística significativa somente entre os tratamentos. As duas espécies tiveram o mesmo nível de bioacumulação de Mn na parte aérea. Nas raízes houve diferença estatística significativa para os tratamentos nas duas espécies, e correlação positiva com o teor de Mn do solo. Apesar da Sinapis alba apresentar índice médio de translocação maior, a Brassica juncea mostrou maior conteúdo de Mn por planta, com rendimento máximo nas doses de 200 mg kg-1 e 300 mg kg-1 de Mn no solo. As duas espécies mostraram potencial para uso em fitorremediação de solos devido à alta bioacumulação de Mn (hiperacumuladoras) e translocação. A Brassica juncea mostrou-se mais promissora que a Sinapis alba, por apresentar maior tolerância a altas dosagens de Mn no solo. / The aim of this work was to evaluate the manganese uptake and translocation capacity of two species of mustard, Sinapis alba and Brassica juncea, in order to know their potential for use in the phytoremediation process. The experiment was conducted in greenhouse conditions, at the Agricultural Sciences Department of Taubaté University (UNITAU), using samples of Red Yellow Latosol, argillaceous franc textural class soil. The tested soil manganese doses were 0, 50, 100, 200, 350, 450, 600 and 800 mg kg-1, using manganese sulfate in water solution. The sample soil was taken from 60 cm depth, it was bolted, made homogeneous, chemically analyzed, and nutrients adjustments were made. The harvest took place 50 days after sowing; the biomass was washed, dried until constant weight was reached, ground in type Wiley mill the manganese concentration was determined. The biomass production showed negative correlation with soil manganese concentration, having its growth rate strongly affected from 300 mg kg-1 soil manganese dosage on. Also from this soil manganese level on, toxicity symptoms were visible, such as brown speckles that started on the tips of the older leaves and spread down the leaf until the entire blade was covered; chlorosis and necrosis that effectively reduced the photosynthetic capacity of the plants. The tissue dried biomass showed statistical difference among dosages and in dosage-specie interaction, with Brassica juncea showing greater difference than Sinapis alba in 200 and 300 mg kg-1 soil Mn doses. The tissue manganese bioaccumulation showed positive correlation with soil manganese level and significant difference among treatments. Both species had the same tissue bioaccumulation level. The manganese root concentration also had positive correlation with soil manganese, and statistical difference for treatments was present in both species. Although Sinapis alba translocation index was better, Brassica juncea had greater manganese content level, with best results in 200 and 300 mg kg-1 manganese soil dose. Both species showed good potential for use in soil phytoremediation processes, due to high manganese bioaccumulation and translocation level.
244

DESEMPENHO DE PLANTAS AQUÁTICAS NA MINIMIZAÇÃO DA CARGA POLUENTE DE DEJETOS LÍQUIDOS DE SUINOCULTURA / PERFORMANCE OF AQUATIC PLANTS IN MINIMIZING THE POLLUTANT LOAD OF LIQUID SWINE MANURE

PINAFFI, Camila Dias 05 April 2017 (has links)
Submitted by Adriana Martinez (amartinez@unoeste.br) on 2017-07-06T19:28:28Z No. of bitstreams: 1 Camila Pinaffi.pdf: 3431594 bytes, checksum: e5d36d386908f87bb76dcd0ea731d043 (MD5) / Made available in DSpace on 2017-07-06T19:28:28Z (GMT). No. of bitstreams: 1 Camila Pinaffi.pdf: 3431594 bytes, checksum: e5d36d386908f87bb76dcd0ea731d043 (MD5) Previous issue date: 2017-04-05 / The expansion of swine activity has provided an increase in the volume of waste, and its disposal without a treatment leads to problems of contamination of soil and surface water and groundwater. Aquatic plants are one of the alternatives that can be used in the treatment of these effluents. The objective of this study was to evaluate the potential of aquatic plants (Eichhornia crassipes), water lettuce (Pistia stratiotes) and salvinia (Salvinia auriculata) in improving the chemical and physicochemical characteristics of liquid swine manure (DLS). The experiment was conducted in an open environment in Campus II/UNOESTE. For the composition of the treatments was used liquid swine manure (DLS) of the zootechnical center diluted in water, being distributed in 16 boxes (0,32 m³) of PVC and characterized as: T1 = Witness - only 50% DLS; T2 = 50% DLS + E. crassipes; T3 = 50% DLS + P. stratiotes; T4 = 50% DLS + S. auriculata. In each treatment small, visually similar plants were inserted. The experiment was structured in a randomized complete block design (DBC), with four treatments, in subdivided plots, with four replications. Effluent samplings were performed weekly in the months of Oct/Nov/Dec 2015 and Mar/Apr/May/Jun/Aug/Sep 2016, and a sample of each treatment and repetition was collected, totaling 16 samples per week. In the effluent, the parameters were: electrical conductivity (EC), pH, dissolved oxygen (OD), turbidity, chemical and biochemical oxygen demand (COD e BOD), ammonium (N-NH4+), nitrate (N-NO3-) and total phosphorus (P total). The N-NH3 volatilization rates of the system were also evaluated. To obtain the content of the elements in the plant tissue, the plants were collected monthly and submitted to chemical analysis of the elements: N-NH4+, N-NO3-, P total, as well as the determination of total biomass of dry matter (BMS) of plants. The results were submitted to analysis of variance and to the comparison test of Tukey averages at the 5% probability level. The results obtained indicate that the E. crassipes provided a higher reduction of EC, turbidity, COD, BOD, NH4+ and P total of the effluent, lower NH3 volatilization, as well as the higher total P content present in its plant tissue and The highest production of BMS. P. stratiotes followed by E. crassipes showed higher NH4+ content in their plant tissues. Therefore, among the macrophytes studied, E. crassipes stands out as the most profitable in the cleaning of liquid swine manure. / A expansão da atividade da suinocultura tem proporcionado aumento no volume de dejetos, sendo que seu descarte sem um tratamento acarreta em problemas de contaminação do solo e das águas superficiais e subterrâneas. As plantas aquáticas são uma das alternativas que podem ser utilizadas no tratamento destes efluentes. Desta maneira, o estudo tem como objetivo avaliar o potencial das plantas aquáticas aguapé (Eichhornia crassipes), alface d’água (Pistia stratiotes) e salvínia (Salvinia auriculata) na melhoria das características químicas e físico-químicas dos dejetos líquidos de suinocultura (DLS). O experimento foi conduzido em ambiente aberto no Campus II/UNOESTE. Para composição dos tratamentos foi utilizado o DLS do centro zootécnico diluído em água, sendo distribuídos em 16 caixas (0,32 m³) de PVC e caracterizados como: T1 = Testemunha - apenas 50% DLS; T2 = 50% DLS + E. crassipes; T3 = 50% DLS + P. stratiotes; T4 = 50% DLS + S. auriculata. Em cada tratamento foram inseridas plantas de pequeno porte, semelhantes visualmente. O experimento foi estruturado em delineamento em blocos casualizados (DBC), com quatro tratamentos, em parcelas subdivididas, com quatro repetições. As amostragens do efluente foram realizadas semanalmente, nos meses de Out/Nov/Dez de 2015 e Mar/Abr/Mai/Jun/Ago/Set de 2016, sendo coletada uma amostra de cada tratamento e repetição semanalmente. Foram analisados no efluente os parâmetros: condutividade elétrica (CE), pH, oxigênio dissolvido (OD), turbidez, demanda química e bioquímica de oxigênio (DQO e DBO), amônio (N-NH4+), nitrato (N-NO3-) e fósforo total (P total). Também foram avaliadas as taxas de volatilização de amônia (N-NH3) do sistema. Para obter o teor dos elementos no tecido vegetal, as plantas foram coletadas mensalmente e submetidas à análise química dos elementos: N-NH4+, N-NO3-, P total, bem como a determinação da biomassa de matéria seca (BMS) total das plantas. Os resultados foram submetidos à análise de variância e ao teste de comparação de médias Tukey ao nível de 5% de probabilidade. Os resultados obtidos indicam que a espécie E. crassipes proporcionou maior redução de CE, turbidez, DQO, DBO, NH4+ e P total do efluente, menor volatilização de NH3, assim como o maior teor de P total presente em seu tecido vegetal e a maior produção de BMS. A P. stratiotes seguida da E. crassipes apresentaram maior teor de NH4+ em seus tecidos vegetais. Sendo assim, dentre as macrófitas estudadas, destaca-se à E. crassipes como a mais profícua na limpeza dos dejetos líquidos de suínos.
245

Crescimento, tolerância e potencial fitorremediador de leucaena leucocephala em solo contaminado por cobre e ferro /

Bomfim, Nayane Cristina Pires. January 2020 (has links)
Orientador: Liliane Santos de Camargos / Resumo: As intensas atividades antropogênicas têm aumentado as concentrações de metais pesados no solo, por meio do uso excessivo de produtos químicos e do descarte inadequado e acúmulo de resíduos sólidos e líquidos, por exemplo, surgindo assim riscos de poluição do solo e corpos d’água. O desenvolvimento de tecnologias sustentáveis, efetivas e de baixo custo para recuperação de áreas contaminadas por metais pesados é de extrema necessidade. A fitorremediação é uma técnica, de baixo custo, que utiliza plantas na recuperação de solos contaminados por metais pesados. Espécies de leguminosas apresentam características favoráveis para crescerem rapidamente em solos degradados, o que é uma característica importante quando considera-se o potencial para fitorremediação destes contaminantes. Objetivou-se caracterizar a resposta fisiológica, determinar a tolerância e o potencial fitorremediador de Leucaena leucocephala aos metais cobre e ferro. O experimento foi conduzido em casa de vegetação, em delineamento inteiramente casualizado para ambos os metais. O solo foi tratado com cinco doses, além do controle (0, 100, 200, 300, 400 e 500 mg/dm3 solo), em sacos de mudas com capacidade para 2 dm3 de solo. Sementes de L. leucocephala foram semeadas diretamente no solo contaminado e cultivadas por 120 dias. Os parâmetros fotossintéticos, foram analisados; o material vegetal foi coletado e os tecidos foram separados, medidos e pesados para avaliação de crescimento. Teores de clorofila e carotenoide... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The intense anthropogenic activities have increased the concentrations of heavy metals in the soil, through the excessive use of chemicals and the improper disposal and accumulation of solid and liquid residues, for example, thus resulting in risks of pollution of the soil and water bodies. The development of sustainable, effective and low-cost technologies for the recovery of areas contaminated by heavy metals is extremely necessary. Phytoremediation is a technique that uses plants to recover soils contaminated by heavy metals. Legume species have favorable characteristics to grow quickly in degraded soils, which is an important characteristic when considering the potential for phytoremediation of these contaminants. The objective was to characterize the physiological response, to determine the tolerance and phytoremediation potential of Leucaena leucocephala to copper and iron metals. The experiment was carried out in a greenhouse, in a completely randomized design for both metals. The soil was treated with five doses, in addition to the control (100, 200, 300, 400 and 500 mg/dm3 soil), in seedling bags with a capacity of 2 dm3 soil. Leucaena leucocephala seeds were sown and cultivated for 120 days. The photosynthetic parameters were analyzed; the plant material was collected and the tissues were separated, measured and weighed for growth evaluation. Chlorophyll and carotenoid contents were quantified in the leaves. Nutrient contents in plants and soil were determined. The ... (Complete abstract click electronic access below) / Mestre
246

Studium abiotického stresu u rostlin na úrovni proteomu / The proteomic study of abiotic stress of plants.

Barabášová, Kamila January 2011 (has links)
Keywords: Arabidopsis thaliana, phytoremediation, abiotic stress, ibuprofene, doxorubicin, two-dimensional electrophoresis Nowadays, develop of the pharmaceutical industry is very fast. Reason of this trend is ever-increasing number of diseases, lifestyle and still increasing demand for the drugs. With this trend growing interest in the analysis of the residues of pharmaceuticals in the environment which is result of incomplete wastewater treatment. This diploma thesis is studying effect of cytostatic drugs, specifically doxorubicin and one of the most widely used analgesics - ibuprofen, at the proteome level of the model plant Arabidopsis thaliana. Proteins isolated from plants exposed to the drugs were separated by two-dimensional electrophoresis. Comparing of protein maps by PDQest program (Bio-Rad, USA) was found several proteins whose expression was affected by the presence of drugs in the culture medium. Selected proteins were identified by LC - MS / MS.
247

Thorium jako environmentální stresový faktor pro růst rostlin v kontaminovaném prostředí / Thorium as an environment stressor for plant growth.

Hrdinová, Aneta January 2016 (has links)
Thorium is an element belonging to heavy metals, which is characterized by its radioactivity similarly to uranium and radon. Thorium is not commonly used in industry, but becouse of its radioactive properties it has a great potentional for future use in nuclear energetics. Thus, increasing release of Th into the soil, water and atmosphere can be expected in near future and through plant biomass it could become a part of food chains and webs and, thus, to represent a considerable health risks to humans. Studies devoted to research on thorium and its effects on plants has not been published much yet. The majority of these studies focus mainly only on plant abilities to accumulate thorium and/or monitoring distribution of thorium in plant body. But till now, a study is still missing, which would monitor the effect of thorium on the physiological characteristics of plants. Plants of Nicotiana glutinosa (L.) medium Thorium accumulatin were hydroponically cultivated Hoagland nutrient media differedin the presence of thorium, tartaric acid, putrescine and phosphates. In first part of the present study I monitored accumulation of thorium by tobacco plants under the influence of the above-mentioned modifications of media. In the second part, I studied the Th effect on the photosynthetic apparatus (contents...
248

Phytoremediation of Heavy Metal Polluted Soils Using Local Plants in the Msimbazi River Catchment, Tanzania. : A Minor Field Study. / Fytoremediering av tungmetall förorenade jordar genom användning av lokala växter i Msimbazi flodens avrinningsområde, Tanzania.

Österling, Eskil January 2011 (has links)
This master thesis is a study of the feasibility of in situ soil remediation techniques in Dar es Salaam, Tanzania. It first looks at the existing on site remediation techniques and assesses how feasible they appear in the conditions of Dar es Salaam. Two methods were interpreted as more feasible than others, namely reactive zone remediation and phytoremediation. The feasibility of phytoremediation was assessed by sampling locally occurring plants and comparing their content of Cu, Pb and Zn with the respective content of the soil they grew in. If the content in the plants were elevated as compared to the soil content, the plant was deemed interesting from a phytoremediation point of view.
249

Interactive Effects of Lead, Copper, Nickel and Zinc on Growth, Metal Uptake and Antioxidative Metabolism of Sesbania drummondii

Israr, Mohd, Jewell, Amy, Kumar, Dhirendra, Sahi, Shivendra V. 28 February 2011 (has links)
Sesbania drummondii seedlings were grown in a medium to which lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) were added singly and in combinations in order to assess the effects of metal interactions on seedling growth, metal accumulation and anti-oxidative system. S. drummondii growth was significantly inhibited with metal treatments. S. drummondii accumulated substantially higher concentrations of metals in the roots than shoots. The uptake of metals followed the order Pb > Cu > Zn > Ni in roots and Pb > Zn > Cu > Ni in shoots. In addition, uptake of a single metal by S. drummondii was affected by the presence of a second metal, suggesting an antagonistic effect or competition between metals at the plant uptake site. A significant increase in both enzymatic [superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR)] and non-enzymatic (glutathione) antioxidant was observed in the S. drummondii seedlings exposed to different metal treatments. The enhancement in enzyme activities followed the order of Cu > Ni > Pb > Zn. However, compared to the effect of individual metal, metals in combination increased the enzyme activities to varying degrees.
250

Measuring the Removal of Trichloroethylene from Phytoremediation Sites at Travis and Fairchild Air Force Bases

Klein, Heather A. 01 May 2011 (has links)
Past use of trichloroethylene (TCE) as a degreasing solvent for aircraft maintenance has resulted in widespread groundwater contamination at Air Force Bases around the world. Travis AFB in California and Fairchild AFB in Washington are evaluating phytoremediation as a treatment option, since trees have been reported to take up dissolved TCE from shallow groundwater and volatilize it to the atmosphere while enhancing the volatilization of TCE from surrounding soil. Previous studies generally focused on the identification of removal mechanisms. The emphasis of this research was to quantify total TCE removal from phytoremediation demonstration plots at Travis and Fairchild AFBs. Tree cores, collected using an increment borer and analyzed using headspace GC/MS, were used to determine the relative TCE concentrations within the plume beneath the trees and to estimate the mass of TCE in each tree. To estimate the volatilization of TCE from leaves, a small section of tree branch was placed inside a flow-through glass chamber. Continuous air flow through the chamber maintained normal transpiration and temperature. Air exiting the chamber was sampled for TCE using Tenax® tubes. Humidity probes placed at the chamber entry and exit were used to estimate transpiration. Volatilization of TCE from tree trunk and soil surfaces was measured by enclosing a section of trunk or ground surface within a small stainless steel chamber. Fans in the chamber mixed the air that was recirculated through Tenax® tubes to continuously remove TCE. After a measured time interval, the Tenax® tubes were analyzed for TCE by thermal desorption GC/MS. By using a Thiessen polygon method, the removal of TCE was estimated to be 839 g/yr at Travis and 18 g/yr at Fairchild with the majority from leaf and soil volatilization. Soil surface volatilization of TCE was greater inside the planted areas than outside the planted areas, indicating that the trees enhance this removal by this mechanism. Based on these estimates phytoremediation removed 5 and 50% of the mass of TCE in the groundwater at Fairchild and Travis Air Force sites, respectively.

Page generated in 0.4812 seconds