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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.
11

Reactive milling of organic compounds

Li, Ying Yu Unknown Date (has links)
Persistent organic pollutants are a well-known threat to the environment. Substances such as polycyclic aromatic hydrocarbons and chlorinated organic compounds in contaminated soil and groundwater can have severe and long-lasting effects on health in animals and humans. There is an urgent need for the development of safe technologies for their effective removal. Originally developed for mineral processing, mechanical treatment by ball milling is an extremely versatile technique for the degradation of toxic compounds. Reactive milling can rapidly destroy organic compounds without producing hazardous wastes. Complete breakdown of the organic molecules is achieved after relatively short milling times. Successful tests were conducted on polychlorobiphenyls (PCBs), DDT, DDD, DDE, Dieldrin and hexachlorobenzene with a conversion yield in the of greater than 99% (Hall et al., 1996; Monagheddu et al., 2000; Zhang et al., 2001; Zhang et al., 2002; Tanaka and Zhang, 2003; Pizzigallo et al., 2004; Nomura et al., 2005; Bellingham, 2006).In this study reactive ball milling was used to investigate the destruction of two classes of persistent organic pollutants environmental contaminants. The compounds studied are either known environmental pollutants or simple analogues. These were chosen as being representative of pollutants to investigate the pathway using ball milling destruction and in most cases were relatively small molecules so that the intermediates could be more easily identified. The first class of compounds was polycyclic aromatic compounds. Some smaller members of this class such as naphthalene, anthracene were investigated. The second class of compounds were some analogues of environmentally hazardous hydroxylated and halogenated compounds such as chloronaphthalene, bromonaphthalene, 1- naphthol, 2-naphthol and pentachlorophenol under reactive milling using GCMS analysis of the degradation pathway. Destruction efficiencies greater than 99% have been achieved for a number of organic compounds. Several different intermediates have been identified during the milling degradation. There was also some evidence from this study that halogens could be transferred between compounds during milling. The final products of the milling destruction of these compounds are an amorphous carbon residue and inorganic chloride or bromides. It was proposed that large amounts of halogens could be found however the results showed that small amounts detected. At early stages of milling a number of intermediate breakdown products were detected which were destroyed on extended milling. The core objective of this research was to clarify the reaction mechanisms pathways used of more complex polycyclic aromatic hydrocarbons and aromatic organ halogen compounds. This study is a part of a long-term research project on the destruction of toxic organic compounds by reactive milling.
12

GIS model for assessment of land use and urban development effects on stormwater runoff: Puhinui Catchment case study

Krpo, Ana Unknown Date (has links)
As local authorities are becoming more interested in the assessment of pollutant loads, this study offers a Geographic Information System (GIS) model for assessing nonpoint source of pollution for two scenarios: the current and ultimate stage of urbanization. The Puhinui Catchment, Manukau City, has been used as a case study in developing and testing this model. This catchment has all the attributes of a "typical" urban area and gives a good representation of the effects of land use on the receiving waters of Puhinui Stream and its estuary. Annual mass contaminant loadings were calculated by firstly assessing the physical characteristics of the Puhinui catchment (case study catchment) and secondly describing the nature of storm water quality and calculating the annual mass contaminant loadings.GIS is used to multiply the annual runoff volume by a mean pollutant concentration to acquire an average annual pollutant load. The annual runoff volume is calculated from the drainage area, runoff coefficient and annual rainfall. To calculate the total mean pollutant load, the pollutant loads for all land use types within the catchment are summed and the process is applied for each pollutant. This GIS model determines the connection of typical pollutant concentrations with land uses in the catchment and offers a characterisation of nonpoint source pollution in that catchment. This model can be used for, identifying catchment areas that contribute considerably to the pollution of waterways, determining the appropriate treatment of the storm water runoff for particular sub catchment, storm water quality improvement prioritization and cost-benefit analysis, selecting locations for water-quality monitoring stations, improvement in maintenance practices, assessment of proposed development environmental effects.
13

Description, dueting, seasonal variations, and individual identification of the vocalisations of the brown kiwi (Apteryx mantelli)

Corfield, Jeremy Unknown Date (has links)
Vocalisations of the endangered Brown Kiwi (Apteryx mantelli) are currently used in a nationwide monitoring program to assess the health of a number of small remnant populations. Only an estimate of population health can be obtained from these surveys. This has to form the basis for a number of critical management decisions. The ability to identify kiwi individually during monitoring would greatly improve the accuracy and quality of information obtained and provide a wider base of knowledge when management decisions are made. This study produces a detailed description of the male and female kiwi call, including duetting and seasonal variations. It then explores whether kiwi demonstrate individually distinctive vocalisations, which could be used in conservation management of kiwi.Calls from seven male and four female kiwi were recorded from Rarewarewa, Whangarei between the 5th of May 2003 to the 31st of April 2004. Two call variables (call duration, number of syllables), two temporal syllable variables (syllable duration, syllable gap duration) and five syllable spectral variables (frequency with the most amplitude, high frequency, low frequency, start frequency, end frequency) were measured from 48 male and 14 female calls. Variables from each call were used to describe and classify calls using one way repeated measures ANOVAs and Discriminant Function Analysis. Males contained on average 24 syllables and females containing on average 22 syllables, with calls from both sexes lasting on average 28 seconds. Male and female kiwi calls differed in multiple spectral, temporal and structural features. Dueting rates and behaviour differed between pairs. Some pairs almost always called in duets, whereas others never dueted. Dueting behaviour also changed seasonally with fewer duets occurring in the non-breeding season and with females initiating more duets in the breeding season. Call structure did not differ between the breeding and non-breeding season. Although the sample size was not sufficient to test for this.Statistically significant differences occurred among nearly all variables between individual male and female kiwi calls, despite statistically significant difference occurring between syllables within calls. Frequency variables were the most important variables in discriminating between individuals, but multiple spectral and temporal variables were needed to separate all individuals. Discriminant Function Analysis was able to correctly classify 87.5% of male and 85.7% of female calls correctly when using the means of the seven syllable variables and the two call variables and 68.2% of male and 66.8% when using the values from each syllable. The latter was improved to 85.9% of male calls correctly classified when only 3 syllables from the middle of the calls were used in DFA, reflecting the variation found at the beginning and end of calls.Brown kiwi show strong signs of individually distinctive vocalisations, which remained consistent over a one year period. The conservation implications of individually distinctive vocalisations and how this feature could be incorporated into the current monitoring of kiwi are discussed.
14

The effectiveness of steel foundry by-product in the treatment of stormwater

Ren, Jiyang Unknown Date (has links)
The capacity and efficiency of melter slag (provided by New Zealand Steel) to remove heavy metals and suspended solids from stormwater samples are studied in this thesis. A series of batch tests were carried out to investigate the adsorption-desorption mechanism of the slag to remove heavy metals (Cd2+, Zn2+ and Cu2+) from working solutions. The results showed that all the tested metallic ions could be removed by mixing the melter slag with the working solutions. Adsorption and ion exchange are the dominant mechanisms in this process. The adsorption capacity follows the descending order of Cu2+ > Zn2+ = Cd2+. Varied binding energy of different metallic ions to the slag resulted in competitive adsorption between ions.A variety of substances: inorganic salts (KCl, NaCl, KNO3 and sea water), organic acids (citric and tartaric) and inorganic acids (nitric and carbonic), were tested as desorbing agents to recover the used slag. Citric acid in sea water was found to be the best in terms of desorption efficiency and cost-effectiveness.The column tests were carried out to simulate the filtration bed in laboratory conditions. Stormwater samples were collected from residential and commercial areas in Auckland. The synthetic stormwater samples were prepared from clay and metallic ion solution. Both samples were used as feeding solutions in the tests. The removal efficiencies of suspended solids and metallic ions (Zn2+, Cd2+ and Cu2+) vary depending on different operation conditions. They are in inverse proportion to the grain size of the melter slag and the influent flow rate. The higher removal efficiency of Zn2+ than that of suspended solids infers that metallic ions are removed by both precipitation and adsorption.
15

GIS model for assessment of land use and urban development effects on stormwater runoff: Puhinui Catchment case study

Krpo, Ana Unknown Date (has links)
As local authorities are becoming more interested in the assessment of pollutant loads, this study offers a Geographic Information System (GIS) model for assessing nonpoint source of pollution for two scenarios: the current and ultimate stage of urbanization. The Puhinui Catchment, Manukau City, has been used as a case study in developing and testing this model. This catchment has all the attributes of a "typical" urban area and gives a good representation of the effects of land use on the receiving waters of Puhinui Stream and its estuary. Annual mass contaminant loadings were calculated by firstly assessing the physical characteristics of the Puhinui catchment (case study catchment) and secondly describing the nature of storm water quality and calculating the annual mass contaminant loadings.GIS is used to multiply the annual runoff volume by a mean pollutant concentration to acquire an average annual pollutant load. The annual runoff volume is calculated from the drainage area, runoff coefficient and annual rainfall. To calculate the total mean pollutant load, the pollutant loads for all land use types within the catchment are summed and the process is applied for each pollutant. This GIS model determines the connection of typical pollutant concentrations with land uses in the catchment and offers a characterisation of nonpoint source pollution in that catchment. This model can be used for, identifying catchment areas that contribute considerably to the pollution of waterways, determining the appropriate treatment of the storm water runoff for particular sub catchment, storm water quality improvement prioritization and cost-benefit analysis, selecting locations for water-quality monitoring stations, improvement in maintenance practices, assessment of proposed development environmental effects.
16

The effectiveness of steel foundry by-product in the treatment of stormwater

Ren, Jiyang Unknown Date (has links)
The capacity and efficiency of melter slag (provided by New Zealand Steel) to remove heavy metals and suspended solids from stormwater samples are studied in this thesis. A series of batch tests were carried out to investigate the adsorption-desorption mechanism of the slag to remove heavy metals (Cd2+, Zn2+ and Cu2+) from working solutions. The results showed that all the tested metallic ions could be removed by mixing the melter slag with the working solutions. Adsorption and ion exchange are the dominant mechanisms in this process. The adsorption capacity follows the descending order of Cu2+ > Zn2+ = Cd2+. Varied binding energy of different metallic ions to the slag resulted in competitive adsorption between ions.A variety of substances: inorganic salts (KCl, NaCl, KNO3 and sea water), organic acids (citric and tartaric) and inorganic acids (nitric and carbonic), were tested as desorbing agents to recover the used slag. Citric acid in sea water was found to be the best in terms of desorption efficiency and cost-effectiveness.The column tests were carried out to simulate the filtration bed in laboratory conditions. Stormwater samples were collected from residential and commercial areas in Auckland. The synthetic stormwater samples were prepared from clay and metallic ion solution. Both samples were used as feeding solutions in the tests. The removal efficiencies of suspended solids and metallic ions (Zn2+, Cd2+ and Cu2+) vary depending on different operation conditions. They are in inverse proportion to the grain size of the melter slag and the influent flow rate. The higher removal efficiency of Zn2+ than that of suspended solids infers that metallic ions are removed by both precipitation and adsorption.

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