Thesis (M. Phil.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 62-72).

Thesis (Ph. D.)--University of Wisconsin, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The proliferation of nanotechnology has prompted discussions over the safety of these materials to human health and the environment as their environmental fate and impact is widely unknown. This is partly due to the lack of suitable analytical techniques to detect and characterise engineered nanoparticles in the environment. This thesis aims to provide a better understanding of the environmental fate of engineered nanoparticles by developing analytical methods suitable for nanoparticle analysis in aquatic systems and employing these to laboratory-based environmental fate studies.

The development of waste management legislation in the 1990's has placed great importance on the sustainability of waste disposal/treatment options. Landfill of wastes is increasingly seen as a last resort and reduction, re-use and recovery of wastes is encouraged. The wastes investigated in this study (caustic tar and sewage sludges) are often disposed of by non-sustainable methods. In addition production of sewage sludge will have doubled by 2005 and disposal options are increasingly limited. Alternative treatment options are required for both these waste types that offer re-use potential. In this study the carbonisation and activation of these wastes has been demonstrated to be an effective means of treatment that also produces adsorbents that can be safely and usefully applied to treatment of aqueous waste streams. Previous studies have examined the production of clay-carbon adsorbents from spent bleaching earth and limited studies have been conducted on producing adsorbents from sewage sludges. However, the majority of these have limited investigations to production of oils from sludge and no previous studies of caustic tar carbonisation have been conducted. Treatment of caustic tar involved neutralisation with HCl and absorption of the organic content of the waste by Fullers or Acid Activated Earth. The clay-waste mix was subsequently carbonised (375°C for 2 hours) and activated using an optimised ZnClj activation procedure (600°C for 1 hour). Activated carbons were produced from sewage sludges using carbonisation (500°C for 2 hours), CO^ activation (700°C for I hour) and ZnCl^ activation (450°C for 2 hours and 600°C for 1 hour). The adsorbents produced had well developed porosity and large surface areas (up to 225mVg for caustic tar derived carbons and up to 995mVg for sewage sludge based carbons) and were adsorptive of a range of organic pollutants common in effluents. ZnC^ activated, un-digested sewage sludges proved to be the most effective adsorbents. COj activated sewage sludges and caustic tar derived carbons had similar adsorption capacities for the organic pollutants studied. Leaching tests demonstrated that metals present in the adsorbents other than the ZnClj activated carbons were not readily leachable and would not prevent re-use of the carbons in the treatment of aqueous effluents.

Some trace elements and various PCB congeners were determined in superficial sediments from Liverpool Bay. Some sediment parameters were also determined for a better understanding of the distribution of these contaminants. Lower amounts of fine particles were found in sediments from the southern area of the sampling grid where the hydrodynamic conditions inhibit the deposition and favour the resuspension of particles with small diameter. The distribution of muddy deposits was patchy throughout the bay although the mud deposits near the Burbo Bight seem to be a permanent feature. The concentrations of trace elements and carbon were determined in two grain size fractions. Carbon in the fine fraction increased in sediment samples with lower proportions of fine sediments probably as a result of an increase in the available surface area since these samples apparently had higher proportions of clays. This relationship was scattered suggesting that the inputs of carbon from different sources, i. e., waste disposal, riverine inputs and autochthonous production, overshadow any clear trends between carbon and grain size in sediments. This observation is consistent with the distribution of S13C values. The concentration of organic matter in coarse sediments seemed to be determined by the amount of surrounding fine particles, particularly in samples with fine fraction concentrations higher than 5%. The concentrations of all of the trace elements, except arsenic, in the coarse fraction were correlated with the organic matter content suggesting that the organic phase is an important carrier of metals in the coarse particles. In the fine fraction, however, there was a large variability in the correlations, suggesting different geochemical behaviour between trace elements. For example a contrasting behaviour was observed between mercury and arsenic since the former seemed to be associated with land derived organic matter with no correlations with the content of iron and manganese, whereas arsenic showed a strong correlation with these two elements reflecting its preference for hydrous oxides of iron and manganese. The geochemical behaviour of each particular trace element seems to play an important role in the observed distributions of the elements in Liverpool Bay sediments. PCBs were determined in total sediments. A high correlation between PCB concentrations and the fine fraction content was observed as a result of the preferential association of these contaminants in fine particles. The distribution of normalized PCB concentrations indicated that inputs from the Mersey may be an important source of PCBs. Different patterns were observed in the PCB congener composition of the samples which reflected the different sources and degree of alteration of the "original" pattern found at the source. The changes in the composition were related to the degree of chlorination and substitution pattern since these factors control the physicochemical properties of PCB congeners. The sediments were classified based on their elemental content and on their PCB contents by means of multivariate statistical methods. The sediments were classified in similar groups from their organic and inorganic contents, which suggested that the sources of organic and inorganic contaminants in Liverpool Bay are similar.

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Turf growers have been farming the Ladner soil in the Boundary Bay area for the last decade. At each harvest, approximately a 2cm layer from the A horizon is taken out with grass. Consequently, the cultivation layer is becoming thinner year after year and the growers are already cultivating the B horizon. The possible improvement of the B horizon structure through sewage sludge application will benefit the fanners in the area. A greenhouse experiment was conducted using a Ladner subsoil. Treatments included application rates of 0, 33, and 100 t/ha of composted sewage sludge. The effect of sludge application on the soil structural stability in relation to the destructive action of water was evaluated. Soil columns were subjected to periodic 24-hour simulated ponding events. Adding sewage sludge increased the ponding tolerance of the soil. This was reflected by statistically significant differences in satiated hydraulic conductivity ('Ks') between the sludge-amended columns and the control columns. The significant decrease of 'Ks' of the control treatment as a result of ponding was responsible for widening the gap between 'Ks' of the control columns and 'Ks' of the sludge-treated columns. The incorporation of sewage sludge slowed down the decrease of 'Ks' but could not stop it. The most plausible explanation is that the addition of sewage sludge was effective in increasing the resistance of aggregates to breakdown when subjected to ponding. Fifty days after the last ponding event, the percent stable aggregates averaged 13.7, 26.9, and 48.1% for the 0, 33, and 100 t/ha treatments respectively. In no case was a significant difference in bulk density observed between the treatments. The soil structure deterioration as a result of ponding was not reflected by the bulk density measurements. Thus, it was concluded that hydraulic conductivity and aggregate stability are better idices of soil structural deterioration than bulk density. A side investigation was carried out to illustrate trends of essential nutrient and heavy metal uptake by bermuda grass. Sludge incorporation at 33 t/ha did not seem to increase nutrient and metal uptake by bermuda grass. However N, Cd, and Zn uptake appeared to increase at 100 t/ha. / Land and Food Systems, Faculty of / Graduate

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Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 69-74).