Rozprawy doktorskie na temat „Soil chemistry”
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Sørensen, Rasmus. "Topographical influence on soil chemistry /". Uppsala : Department of Environmental Assessment, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/10113030.pdf.
Pełny tekst źródłaGolchin, Ahmad. "Spatial distribution, chemistry and turnover of organic matter in soils". Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phg617.pdf.
Pełny tekst źródłaKhoee, Bahman. "Soil solution and exchange complex chemistry in a forested watershed". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61821.
Pełny tekst źródłaFotovat, Amir. "Chemistry of indigenous Zn and Cu in the soil-water system : alkaline sodic and acidic soils". Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phf761.pdf.
Pełny tekst źródłaDzenitis, John M. "Soil chemistry effects and flow prediction in remediation of soils by electric fields". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10973.
Pełny tekst źródłaKamari, Azlan. "Chitosans as soil amendments for the remediation of metal contaminated soil". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2595/.
Pełny tekst źródłaSika, Makhosazana Princess. "Effect of biochar on chemistry, nutrient uptake and fertilizer mobility in sandy soil". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20272.
Pełny tekst źródłaENGLISH ABSTRACT: Biochar is a carbon-rich solid material produced during pyrolysis, which is the thermal degradation of biomass under oxygen limited conditions. Biochar can be used as a soil amendment to increase the agronomic productivity of low potential soils. The aim of this study was to investigate the effect of applying locally-produced biochar on the fertility of low-nutrient holding, sandy soil from the Western Cape, and to determine the optimum biochar application level. Furthermore, this study investigates the effect of biochar on the leaching of an inorganic nitrogen fertilizer and a multi-element fertilizer from the sandy soil. The biochar used in this study was produced from pinewood sawmill waste using slow pyrolysis (450 °C). The soil used was a leached, acidic, sandy soil from Brackenfell, Western Cape. In the first study, the sandy soil mixed with five different levels of biochar (0, 0.05, 0.5, 0.5 and 10.0 % w/w) was chemically characterised. Total carbon and nitrogen, pH, CEC and plant-available nutrients and toxins were determined. The application of biochar resulted in a significant increase in soil pH, exchangeable basic cations, phosphorus and water holding capacity. A wheat pot trial using the biochar-amended soil was carried out for 12 weeks and to maturity (reached at 22 weeks). The trial was conducted with and without the addition of a water-soluble broad spectrum fertilizer. Results showed that biochar improved wheat biomass production when added at low levels. The optimum biochar application level in the wheat pot trial was 0.5 % (approximately 10 t ha-1 to a depth of 15 cm) for the fertilized treatments (21 % biomass increase), and 2.5 % (approximately 50 t ha-1 to a depth of 15 cm) for unfertilized treatments (29 % biomass increase). Since most biochars are alkaline and have a high C:N ratio, caution should be taken when applying it on poorly buffered sandy soil or without the addition of sufficient nitrogen to prevent nutrient deficiencies. In the second study, leaching columns packed with sandy soil and biochar (0, 0.5, 2.5 and 10.0 % w/w) were set up to determine the effect of biochar on inorganic nitrogen fertilizer leaching over a period of 6 weeks. It was found that biochar (0.5, 2.5, and 10.0 % w/w) significantly reduced the leaching of ammonium (12, 50 and 86 % respectively) and nitrate (26, 42 and 95 % respectively) fertilizer from the sandy soil. Moreover, biochar (0.5 %) significantly reduced the leaching of basic cations, phosphorus and certain micronutrients. This study demonstrated the potential of biochar as an amendment of acidic, sandy soils. Our findings suggest that an application rate of 10 t ha-1 should not be exceeded when applying biochar on these soils. Furthermore, biochar application can significantly reduce nutrient leaching in sandy agricultural soils.
AFRIKAANSE OPSOMMING: Biochar is ʼn koolstof-ryke, soliede materiaal geproduseer gedurende pirolise, wat die termiese degradasie van biomassa onder suurstof-beperkte omstandighede behels. Biochar kan gebruik word as ʼn grondverbeterings middel om die agronomiese produktiwiteit van grond te verhoog. Die doel van hierdie studie was om die effek van plaaslike vervaardigde biochar op die vrugbaarheid van die sanderige grond van die Wes-Kaap te ondersoek, en om die optimale biochar toedieningsvlak te bepaal. Verder, het hierdie studie die effek van biochar op die loging van anorganiese stikstof kunsmis en ‘n multi-elementkunsmis op sanderige grond ondersoek. Die biochar wat in hierdie studie gebruik is, is van dennehout saagmeul afval vervaardig d.m.v. stadige pirolise (450 °C). Die grond wat in hierdie studie gebruik is, is ‘n geloogde, suur, sanderige grond van Brackenfell, Wes-Kaap. In die eerste studie, is ‘n chemiesie ondersoek van die sanderige grond wat vermeng met is met vyf verskillende vlakke van biochar (0, 0.05, 0.5 en 10.0 % w/w) uitgevoer. Totale koolstof en stikstof, pH, KUK, en plant-beskikbare voedingstowwe en toksiene is in die grondmengsels bepaal. Die toediening van biochar het ‘n veroorsaak dat die grond pH, uitruilbare basiese katione, fosfor en waterhouvermoë beduidend toegeneem het. ‘n Koringpotproef was uitgevoer vir 12 weke en ook tot volwassenheid (wat op 22 weke bereik was) om die effek van die biochar op die sanderige grond teen die vyf verskillende toedieningsvlakke te bepaal. Daar was behandelings met en sonder die bykomstige toediening van ‘n wateroplosbare breë-spektrumkunsmis. Resultate toon dat die toediening van biochar teen lae vlakke koringbiomassa produksie verbeter. Die optimale biochar toedieningsvlak in die koringpotproef is 0.5 % (omtrent 10 t ha-1 tot ‘n diepte van 15 cm) vir die bemeste behandeling (21 % biomassa toename), en 2.5 % (omtrent 50 t ha-1 na ‘n diepte van 15 cm) vir onbemeste behandelings (29 % biomassa toename). Aangesien die meeste biochars alkalies is en ‘n hoë C:N verhouding besit, moet sorg gedra word wanneer dit op swak-gebufferde of lae N-houdende sanderige gronde toegedien word. Die resultate het aangedui dat die biochar versigtig aangewend moet word om grond oorbekalking te voorkom. In die tweede studie, was kolomme gepak met 2.0 kg van die sanderige grond gemeng met biochar (0, 0.05, 0.5, 2.5 en 10.0 % w/w) om die effek van biochar op die loging die anorganiese stikstof kunsmis oor ‘n tydperk van 6 weke om vas te stel. Daar is gevind dat biochar (0.5, 2.5 en 10.0 % w/w) die loging van ammonium (12, 50 en 86 % onderskeidelik) en nitraat (26, 42 en 95 % onderskeidelik) op sanderige grond aansienliek verminder. Verder, het biochar (0.5 %) die loging van basiese katione, fosfor en mikrovoedingstowwe aansienlik verminder. Hierdie studie het die potensiaal van biochar as verbeteringmiddel van suur, sanderige grond gedemonstreer. Ons bevindinge dui daarop aan dat ‘n toepassing vlak van 10 t ha-1 moet nie oorskry word nie wanneer biochar op hierdie gronde toegedien word. Die toediening van biochar op sanderige grond kan die loging van voedingstowwe aansienlik verlaag.
Hoyle, Frances Carmen. "The effect of soluble organic carbon substrates, and environmental modulators on soil microbial function and diversity /". Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0050.
Pełny tekst źródłaJenkins, Anthony Blaine. "Organic carbon and fertility of forest soils on the Allegheny Plateau of West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2486.
Pełny tekst źródłaTitle from document title page. Document formatted into pages; contains x, 282 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
Chintala, Rajesh. "Lime induced changes in the surface and soil solution chemistry of variable charge soils". Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5552.
Pełny tekst źródłaTitle from document title page. Document formatted into pages; contains ix, 128 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
MacIver, Vicki. "Soil chemistry of heavy metals under contrasting vegetation covers". Thesis, University of Glasgow, 2000. http://theses.gla.ac.uk/5688/.
Pełny tekst źródłaDickinson, J. M. "The chemistry of fungal biocontrol agents". Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267277.
Pełny tekst źródłaFernandes, A. R. "Trace analysis and chemistry of polychlorinated biphenyls". Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384580.
Pełny tekst źródłaSanClements, Michael. "The Chemistry of Acidic Soils in Humid, Temperate Forested Watersheds with Emphasis on Phosphorus, Aluminum and Iron". Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/SanClementsM2009.pdf.
Pełny tekst źródłaCampbell, Duncan J. "The chemical composition of soil solutions extracted from top soils in the Oxford area : the magnitude and range of variability". Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:e70e0323-8383-45f2-91f5-9cb2c26b5008.
Pełny tekst źródłaHerselman, J. E. "The concentration of selected trace metals in South African soils /". Link to the online version, 2007. http://hdl.handle.net/10019.1/1390.
Pełny tekst źródłaSauvé, Sébastien. "Copper and aluminum free ion activity in soil solutions = L'activité inonique du cuivre et de l'aluminium dans des solutions de sols". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23295.
Pełny tekst źródłaThe second method is a simple determination of free Cu$ sp{2+}$ in soils using a cupric ion-selective electrode. Free copper has been demonstrated to be the toxicity controlling component in aquatic studies and this study was undertaken to measure free copper activity in soils. The possible interference due to ionic strength variations or the presence of aluminum in the soil solution was checked and found to be negligible. The free activity of copper (pCu$ sp{2+}$) measured in a variety of pristine and contaminated soils varied between 6.33 to 12.20 pCu$ sp{2+}$ units. Total soil copper content and acidity were shown to strongly increase copper solubility and free Cu$ sp{2+}$ activity in the soil solution extracts. (Abstract shortened by UMI.)
Beggy, Holly M., i Jeffrey S. Fehmi. "Effect of surface roughness and mulch on semi-arid revegetation success, soil chemistry and soil movement". ELSEVIER SCIENCE BV, 2016. http://hdl.handle.net/10150/616986.
Pełny tekst źródłaO'Brien, Christine. "Soil solution and streamwater chemistry in a small forested watershed". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68234.
Pełny tekst źródłaBakhsh, Ahmad. "Studies on the chemistry and behaviour of zinc in soil". Thesis, University of Glasgow, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303003.
Pełny tekst źródłaKurzman, Amanda Lord. "Changes in major solute chemistry as water infiltrates soils comparisons between managed agroecosystems and unmanaged vegetation /". Diss., Connect to online resource - MSU authorized users, 2006.
Znajdź pełny tekst źródłaWallace, Eileen P. "Soil classification and radionuclide migration in west Cumbrian soils". Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327266.
Pełny tekst źródłaSolomon-Wisdom, Grace Oyiza. "The effect of in situ spatial heterogeneity of lead in soil on plant uptake". Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/54284/.
Pełny tekst źródłaThomas, Jacqueline Yvette. "Quantification of in situ heterogeneity of contaminants in soil : a fundamental prerequisite to understanding factors controlling plant uptake". Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6961/.
Pełny tekst źródłaAhmad, Nor Ashikin. "Phosphorus Dynamics in Soils Amended with Recycled Organics". Thesis, Griffith University, 2017. http://hdl.handle.net/10072/365472.
Pełny tekst źródłaThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
Wei, Yang. "Effects of pure and impure carbon dioxide (CO2) on soil chemistry". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/10831/.
Pełny tekst źródłaUygur, Veli. "Zn sorption/desorption chemistry in calcareous soils from Turkey". Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388131.
Pełny tekst źródłaPunt, Monique M. "Microwave-enhanced extraction of organic contaminants from soil". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27393.
Pełny tekst źródłaThe dielectric properties of several mixtures of acetone and hexane over a temperature range from 25$ sp circ$C to 50$ sp circ$C were measured. The dielectric constants of these mixtures were found not to vary significantly with temperature.
A study of microwave absorption by heterogeneous mixtures showed that adding a solid material to a low dielectric constant solvent resulted in energy being preferentially absorbed by the solid.
The results of laboratory extraction tests showed that the ability of the MAP technique to extract contaminants was affected by the organic matter content of soil, particularly in the presence of water.
Use of a closed-vessel system yielded a 60% to 175% increase in the extraction of PAHs from a low organic-content soil relative to that achieved in an open-vessel system. (Abstract shortened by UMI.)
Baize, John. "Forensic Soil Analysis: Characterization of the Sand Fraction". TopSCHOLAR®, 1997. http://digitalcommons.wku.edu/theses/767.
Pełny tekst źródłaHardie, Ailsa Ghillaine. "Decontamination of soils by activation with acids and bases". Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49901.
Pełny tekst źródłaENGLISH ABSTRACT: New, more receptive surfaces can be generated in soils by a partial dissolution of existing, crystalline solids followed by re-precipitation as poorly crystalline colloids with a larger capacity to adsorb ionic and molecular contaminants. This priming process can be carried out by treating the soil with strong acid or base and then neutral ising it again. The aim of this study was to investigate the effectiveness of acid and base treatments in reducing inorganic contaminant availability in different soil types. The first study involved investigating the change in cation (cadmium[II], copper[II]) and anion (phosphate) sorption of four different soils before and after priming. Hydrochloric acid and KOH were used to adjust the pH of soils to below pH 2 or above pH 12 in the dissolution stage of the priming treatment. After neutralisation it was found that base priming resulted in an increase in metal cation adsorption in all the soils, most notably in the sesquioxidic (increase from 19.5 to 73.5 mmol Cd.kg-1 soil) and kaolinitic soils (from 16.9 to 38.3 mmol Cd.kg-1 soil), whereas acid priming decreased it or had little effect on cation sorption. However, acid priming increased anion sorption in all soil types, to a greater extent than base priming, most notably in the organic soil (from 6.3 to 14.7 mmol P04.kg-1 soil). This can be attributed to the differences in the nature of the precipitate (more aluminous or alumino-siliceous) depending on whether the dissolution was carried out in acid or basic conditions, and the final pH of the soil solution, as the hydroxyaluminium and hydroxyaluminosilicate precipitates which form are known to enhance pH-dependent sorption of metals. In the second study, the soil was suspended in Cd or Cu solutions and then the pH was adjusted to below 2 or above 12 using HCI or KOH. After 5 days of shaking the pH was adjusted to a neutral pH again. The availability of the Cd and Cu was determined at each of the stages in the treatment, and it was found that both the acid and base treatments were effective in removing Cu from solution, whereas only the base treatment was effective in removing Cd. Determinations were also carried out using H2S04 and Ca(OH)2 and it was found that they were equally effective. It can be proposed that this acid-base pair would be of most practical importance as the salt generated is gypsum which is generally considered benign, and can actually help to improve the soil structure. Activation of soils by acid or base conditioning could have some useful applications in decontaminating soils or decreasing the mobility of inorganic contaminants in soils. Primed soils could also be used as cheap absorbents for decontaminating water.
AFRIKAANSE OPSOMMING: DEKONT AMINERING VAN GROND DEUR AKTIVlERING MET SURE EN BASISE Nuwe, meer ontvanklike oppervlakke kan in gronde gegenereer word deur middel van gedeeltelike oplossing van bestaande, kristallyne vaste stowwe gevolg deur herpresipitasie as swak kristallyne kolloïede met 'n groter kapasiteit om ioniese en molekulêre kontaminante te adsorbeer. Hierdie behandelingsproses kan uitgevoer word deur die grond met sterk suur of basis te behandel en dit daarna te neutraliseer. Die doel van hierdie studie was om die effektiwiteit van suur- of basisbehandelings om anorganiese kontaminante te verminder, in verskillende grond tipes te ondersoek. Die eerste studie het die ondersoek na die verandering in katioon- (kadmium[II], koper[lI]) en anioon- sorpsie (fosfaat) van vier verskillende gronde voor en na suur of basis voorbehandeling behels. Soutsuur en KOH was gebruik om die pH van die gronde tot onder pH 2 of bo pH 12 aan te pas gedurende die oplosstadium van die behandelingsproses. Na neutralisasie is dit gevind dat basis voorbehandeling tot 'n toename in metaal katioonadsorpsie in al die gronde gelei het, en dit was veral waarneembaar in die seskwioksied (toename van 19.5 tot 73.5 mmol Cd.kg" grond) en kaolinitiese (van 16.9 tot 38.3 mmol Cd.kg-1 grond) gronde, terwyl suur voorbehandeling dit verlaag het of 'n klein effek op katioonsorpsie gehad het. Suur voorbehandeling, egter, het anioonsorpsie in al die gronde verhoog, tot 'n groter mate as basis voorbehandeling, veral in die organiese grond (van 6.3 tot 14.7 mmol fosfaat.kg' grond). Dit kan toegeskryf word aan die verskille in die aard van die neerslag wat meer alurninium- of alurniniumsilika-ryk kan wees afhangede of die oplossing uitgevoer was in suur of basis kondisies, en ook die finale pH van die grondoplossing omdat die hidroksi-aluminium en hidroksi-aluminiumsilikaat presipitate wat vorm bekend daarvoor is om pH-afhanklike sorpsie van metale te bevorder. In die tweede studie, was die grond in Cd- of Cu-oplossings gesuspendeer en die pH was aangepas tot onder 2 of bo 12 met HCI of KOH. Na vyf dae van skud was die pH weer aangepas tot by neutraal. Die beskikbaarheid van Cd en Cu was bepaal by elke stadium in die behandeling, en dit is gevind dat beide suur- en basisbehandeling meer effektief was in die verwydering van Cu uit oplossing, terwyl slegs die basisbehandeling effektief was in die verwydering van Cd. Bepalings was ook uitgevoer met die gebruik van H2S04 en Ca(OH)2 en dit is gevind dat dit net so doeltreffend was soos HCI en KOH. Dit kan voorgestel word dat hierdie suur-basis paar in die praktyk belangriker sal wees omdat die sout wat gegenereer word, nl. gips, as 'n gunstige sout beskou word. Aktivering van grond deur suur- of basis-kondisionering kan sekere bruikbare toepassings in die dekontaminering van gronde hê of dit kan gebruik word om die mobiliteit van anorganiese kontaminante te verlaag. Suur of basis voorbehandelde gronde kan ook gebruik word as goedkoop absorbante vir die dekontaminering van water.
Kaisheva, Maria V. "The effect of metals and soil pH on the growth of Rhododendron and other alpine plants in limestone soil". Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2606.
Pełny tekst źródłaHabermann, Birgit. "Ways of knowing of farmers and scientists : tree and soil management in the Ethiopian Highlands". Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/49648/.
Pełny tekst źródłaOsei, Benjamin Appiah. "Mineralogy, potassium status, and colloidal chemistry of some Ghanaian soils". Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363900.
Pełny tekst źródłaCabrera, Julio Cesar. "Mercury characterization in soil collected nearby the Department of Energy Oak Ridge reservation". FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/1956.
Pełny tekst źródłaKirk, G. J. D. "The dissolution of mineral phosphate in soil". Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:ccb93b85-1d74-4d8f-8c86-0529bc29a27e.
Pełny tekst źródłaBack, Michael Patrick. "Working Backwards: Enhancing Forest Restoration by Reversing Effects of Surface Mine Reclamation on Soil Bulk Density and Soil Chemistry". Kent State University Honors College / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors162014875138985.
Pełny tekst źródłaMarsden, Rachel Louise. "Rock, soil and soil water chemistry in the Loch Dee catchment, S.W. Scotland : implications for the release of Al". Thesis, University of Stirling, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386536.
Pełny tekst źródłaMacpherson, Stuart Alexander. "Interactions between lead and phosphate : soil chemistry, plant uptake and ecological implications". Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294125.
Pełny tekst źródłaMacPhee, Kirsty Potts. "Hydrochemistry, soil chemistry and critical loads of selected upland moorland catchments, Scotland". Thesis, University of Aberdeen, 1997. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU094086.
Pełny tekst źródłaCantrell, Kirk Jason. "Role of soil organic and carbonic acids in the acidification of forest streams and soils". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/25888.
Pełny tekst źródłaWimaladasa, G. D. "Some aspects of the chemistry and mineralogy of soil potassium in Sri Lankan acid tea soils and Scottish soils under a range of crops". Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020940.
Pełny tekst źródłaChorom, Mostafa. "Behaviour of alkaline sodic soils and clays as influenced by pH and particle change". Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phc551.pdf.
Pełny tekst źródłaDowding, Catherine Elaine. "Morphology, mineralogy and surface chemistry of manganiferous oxisols near Graskop, Mpumalanga Province, South Africa". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16312.
Pełny tekst źródłaENGLISH ABSTRACT: In the humid Graskop region of Mpumalanga Province, South Africa, there is an anomalous body of highly weathered black, manganiferous oxisols derived from dolomite. With Mn contents as high as 17%, potential large-scale Mn release is an environmental concern under current, acid generating, forestry practices. This study aims at establishing the factors which may affect the stability of the manganiferous oxisols of Graskop and in the process, investigating some of the morphological, mineralogical and chemical properties of these unique soils. Typically, the soils show a reddish, nodule-rich horizon, containing 3-4% Mn, grading through a red and black mottled zone into a black (5YR 2.5/1) apedal subsoil with >7% Mn. The Mn gradient down the profile as well as the abundant nodule content of the upper subsoil horizons implies that Mn mobilization and redistribution are active pedogenic processes. The exceptional Mn content of these soils is complemented with Fe and Al concentrations of up to 10 and 8%, respectively, and anomalously high trace element levels in particular Ni and Zn (as high as 541 and 237 mg kg-1, respectively) which are at the upper limit of cited world natural maxima for soils. The Mn mineral lithiophorite [(Al,Li)MnO2(OH)2], dominates the mineralogy of the soils with accessory amounts of birnessite, gibbsite, goethite, hematite, maghemite, kaolinite, aluminous chlorite and mica - a mineral suite reflecting that of well weathered soils. With the pH of the soil being at or close to the point of zero charge (4.5-5.5) the soils show isoelectric equilibrium. The very low buffer capacity results in metal dissolution commencing with the first increment of titrated acidity. Manganese dissolution is relatively minor considering the large potential for release and is highly overshadowed by Al release. The apparent resilience of the Mn phase to added acidity may relate to the overwhelming poise of the soils which maintains robust, oxic conditions despite the usual instability of Mn oxides at low pH. Manganese release and soil redox properties are substantially affected by drying especially in the organic rich topsoils. Using various redox analyses, evidence is shown for involvement of Mn(III)-organic complexes in the drying reactions. Using this and information gained in a real time, attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopic study, a mechanism is suggested which may account for the observed Mn release and the loss of Cr oxidising capacity commonly observed in dried soils. The information provided by the ATR-FTIR study showed the decrease in surface pH of a clay film, from 5 to below 2, as well as the shift in coordination nature of sorbed oxalate from a more outer-sphere association to a more inner-sphere association concomitant with the removal of free water from the clay surface. This spectroscopic evidence for these chemical changes which accompany surface drying not only provides further insight into the reactions involving Mn oxides in soils but also highlights the suitability of ATR-FTIR for real time, in situ investigation into the chemistry of the drying water interface. From these results it is concluded that Mn release from the manganiferous oxisols, under acid generation of the kind known to occur in pine plantations, is less that anticipated. On the other hand, desiccation of the topsoil results in substantial Mn release with a suggested mechanism which involves a Mn(III) intermediate.
AFRIKAANSE OPSOMMING: ‘n Onreelmatige grondliggaam van hoogs verweerde, swart, mangaanhoudende oxisols wat uit dolomiet ontwikkel het, word in die humiede Graskop streek van die Mpumalanga Provinsie van Suid-Afrika aangetref. Die hoë Mn-inhoud (tot 17%) van hierdie oxisols is van groot omgewings-belang weens die potensiële grootskaalse Mn-vrystelling onder huidige, suur-genererende bosbou praktyke. Hierdie studie beoog om die faktore wat die stabiliteit van die mangaanhoudende oxisols van Graskop affekteer, vas te stel. Tesame hiermee word die morfologiese, mineralogiese en chemiese eienskappe van hierdie unieke gronde ondersoek. Kenmerkend van hierdie gronde is ‘n rooi, nodule-ryke horison met 3-4% Mn aan die oppervlakte. Bogenoemde horison verander met toename in diepte in ‘n rooi en swart gevlekte sone wat weer in ‘n swart (5YR 2.5/1) apedale ondergrond met >7% Mn oorgaan. Die Mn gradiënt in die profiel sowel as die hoë nodule-inhoud van die boonste grondhorison dui daarop dat Mn-mobilisasie en -herverspreiding huidige aktiewe pedogenetiese prosesse in die profiele is. Fe en Al, met konsentrasies van 10% en 8% onderskeidelik, word saam met die onreelmatig hoë Mn inhoud aangetref. Baie hoë vlakke van Ni en Zn (so hoog as 541 en 237 mg.kg-1 onderskeidelik) wat hoër is as aangehaalde wêreld natuurlike maksimum waardes, word ook aangetref. Die mineralogie van die gronde word deur die Mn mineraal litioforiet [(Al,Li)MnO2(OH)2] gedomineer. Bykomstige hoeveelhede van birnessiet, gibbsiet, goethiet, hematiet, maghemiet, kaoliniet, aluminiumryke chloried en mika word ook aangetref. Hierdie minerale samestelling is kenmerkend van hoogs verweerde gronde. Met die pH van die grond in die omgewing van die punt van geen lading (4.5 – 5.5), word ‘n iso-elektriese ekwilibrium by die gronde aangetref. Die baie lae bufferkapasiteit het metaal-oplossing aangehelp wat met die eerste inkrement van titreerbare suurheid ‘n aanvang geneem het. Mangaan-oplossing is baie klein indien die groot potensiaal vir vrystelling asook die groot mate van Al-vrystelling in ag geneem word. Die skynbare teenwerking van die Mn fase tot toegevoegde suurheid, mag toegeskryf word aan diesterk ewewig van die gronde om sterk, oksiese kondisies, ten spyte van die normale onstabiliteit van Mn oksiedes by lae pH, te onderhou. Mangaan vrystelling en grond redoks eienskappe word beduidend deur uitdroging beïnvloed en veral in die organies-ryke bogronde. Deur van verskeie redoks analises gebruik te maak is daar bewyse van die betrokkenheid van Mn(III)-organiese komplekse in die uitdroging-reaksies gevind. Dit. en data ingesamel in ‘n “real time, attenuated total reflectance Fourier transform infrared (ATR-FTIR)” spektroskopiese studie, is gebruik om ‘n meganisme voor te stel wat die waargenome Mn vrystelling en die verlies aan Cr oksidasie kapasiteit (algemeen waargeneem in droë gronde) te kan verklaar. Die data verkry met die ATR-FTIR studie het ‘n afname in oppervlak pH van 5 na 2 van ‘n klei film asook die verskuiwing in koördinasie toestand van die gesorbeerde oksalaat van ‘n meer buite-sfeer assosiasie tot ‘n meer binne-sfeer assosiasie, gepaardgaande met die verwydering van vry water van die klei oppervlaktes, uitgewys. Die spektroskopiese bewyse vir die chemiese veranderinge wat die oppervlak uitdroging vergesel, gee nie net meer insig in die reaksies rakende Mn oksiedes in gronde nie maar onderstreep ook die toepasbaarheid van die ATR-FTIR vir intydse (“real time”), in situ ondersoeke na die chemie van die uitdrogende water kontakvlak. Vanuit hierdie resultate kan afgelei word dat Mn vrystelling vanuit mangaanhoudende oxisols onder suur genererende denne plantasies laer is as wat verwag is. Aan die ander kant sal uitdroging van die bogrond tot aansienlike Mn vrystelling, met ‘n verwagte meganisme wat Mn (III) as intermediêre toestand insluit, lei.
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