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Land application of domestic and industrial wastewaters provides an effective means of recycling water and its components into the ecosystem. Successful treatment by soil requires that wastewater is applied in quantities that both maintain infiltrative capacity of the soil and do not exceed the capacity of the soil-plant system to assimilate biological and chemical contaminants. Application of N-rich wastewaters requires that consideration be given to both the ability of the soil to transmit the hydraulic load and remove sufficient N to maintain groundwater quality standards. A textile wastewater containing high concentrations of organic N was spray-irrigated to tall fescue (Festuca arunindinacea) to determine optimum N application levels. Nitrogen balances were determined at each N level and and the potential for predicting the leaching component of the excess N applied was investigated. Historically on-site wastewater disposal systems (OSWDS) for treating septic tank effluent (STE) have been designed on a hydraulic loading basis with N pollution potential essentially ignored. Many soils have been deemed unsuitable for application of STE because of textural, water table, or landscape restrictions. The relations between soil properties, hydraulic performance of OSWDS, and N distribution around OSWDS are evaluated. Wastewater from a nylon processing plant was applied to 'Ky 31' tall fescue at total Kjeldahl nitrogen (TKN) levels of approximately 250, 430, and 1900 kg ha⁻¹ during 1982 and 1983. Fescue yield and N removal was comparable to agricultural yields at similar N application levels. Nitrogen balances indicate that plant uptake efficiency decreased with increasing organic N levels above the 250 kg ha⁻¹ level and that maximum uptake occurred at the 450 kg ha⁻¹ level. Most of the N not recovered in plant tissue mineralized rapidly to the nitrate NO₃⁻ form and leaching was noted during the winter and spring. This data is evaluated with quasi-transient analytical solution of the convection-dispersion equation. The movement of the solute center of mass is predicted on the basis of assumptions of piston flow as well as alternative assumptions of mixing via plate layer theory. Prediction of the location of the center of solute mass (α) provides a moving lagrangian coordinate solution around which dispersion of solute is calculated. The assumptions made about the sequence of evaporation and infiltration events significantly influence the prediction of α and hence the agreement between predicted and measured solute distribution. Both approaches give results which are within experimental error and provide a rational basis for predicting leaching losses and carry-over NO₃⁻ available to future crops. Prototype OSWDS with low pressure distribution installed in three clayey limestone-derived soils were dosed with STE at flux densities ranging from 0.4 to 3.6 cm d⁻¹ on a trench bottom area basis. Ponding was noted in OSWDS at all sites dosed at the 3.6 cm d⁻¹ flux due to both underlying hydraulic restrictions and resultant anaerobic conditions. It is concluded that clayey B horizons low in swelling clays but moderately well structured can be dosed at flux densities up to 2 cm d⁻¹ if low pressure distribution of STE is used. Nitrification was found to be quite limited in soils where effluent was ponded above a restrictive layer but occurred readily within 30 cm below trenches which were freely drained or had matric potentials of at least 40 cm of water. Ratios of NO₃⁻ to Cl⁻ indicate that only limited denitrification can be expected and that substantial NO₃⁻ does leach from below OSWDS in the direction of water flow. / Ph. D.

Lam Lai-yee. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 124-140). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.vii / Table of contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter CHAPTER ONE --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Background and ecological impact of hill fires in Hong Kong --- p.2 / Chapter 1.3 --- Conceptual framework of study --- p.4 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER TWO --- The study area / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Geographical setting of Hong Kong --- p.14 / Chapter 2.2.1 --- Climate of Hong Kong --- p.14 / Chapter 2.2.2 --- Geology of Hong Kong --- p.15 / Chapter 2.2.3 --- Soils of Hong Kong --- p.16 / Chapter 2.2.4 --- Vegetation of Hong Kong --- p.17 / Chapter 2.3 --- Site selection --- p.18 / Chapter 2.4 --- Grassy Hill --- p.20 / Chapter CHAPTER THREE --- Heating effect on the properties of ash / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Experimental design and methodology / Chapter 3.2.1 --- Selection of simulation heating --- p.26 / Chapter 3.2.2 --- "Heating intensity at 200°-600°C for 1,5 and 15 minutes" --- p.27 / Chapter 3.2.3 --- Field work --- p.27 / Chapter 3.2.4 --- Heating method --- p.28 / Chapter 3.2.5 --- Chemical analysis --- p.28 / Chapter 3.2.6 --- Analysis of data --- p.32 / Chapter 3.3 --- Results and Discussion / Chapter 3.3.1 --- Heating effect on ash weight and pH --- p.33 / Chapter 3.3.2 --- "Heating effect on ash organic C, N and P" --- p.33 / Chapter 3.3.3 --- Heating effect on ash available cations --- p.40 / Chapter 3.4 --- Conclusion --- p.42 / Chapter CHAPTER FOUR --- The effect of heat and ash on soil / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Methodology / Chapter 4.2.1 --- Field work --- p.48 / Chapter 4.2.2 --- Soil heating methods --- p.48 / Chapter 4.2.3 --- Chemical analysis --- p.49 / Chapter 4.2.4 --- Statistical analysis --- p.52 / Chapter 4.3 --- Results and Discussion / Chapter 4.3.1 --- The effect of heat and ash on soil pH --- p.53 / Chapter 4.3.2 --- "The effect of heat and ash on soil organic matter, N and P" --- p.55 / Chapter 4.3.3 --- The effect of heat and ash on soil cations --- p.62 / Chapter 4.4 --- Conclusion --- p.65 / Chapter CHAPTER FIVE --- Nitrogen and phosphorus mineralization after heating / Chapter 5.1 --- Introduction --- p.67 / Chapter 5.2 --- Methodology / Chapter 5.2.1 --- Heating and incubation method --- p.70 / Chapter 5.2.2 --- Laboratory methods --- p.72 / Chapter 5.2.3 --- Statistical analysis --- p.72 / Chapter 5.3 --- Results and discussion / Chapter 5.3.1 --- Temporal changes of N mineralization in heated bare soils --- p.72 / Chapter 5.3.2 --- The effect of ash on N mineralization --- p.78 / Chapter 5.3.3 --- Comparison of N mineralization with other studies --- p.79 / Chapter 5.3.4 --- Temporal changes of P mineralization in the heated bare soils --- p.81 / Chapter 5.3.5 --- The effect of ash on P mineralization --- p.83 / Chapter 5.3.6 --- Comparison of P mineralization to other studies --- p.84 / Chapter 5.4 --- Conclusion --- p.85 / Chapter CHAPTER SIX --- Vertical movement of mineral N in ash-covered soil columns / Chapter 6.1 --- Introduction --- p.87 / Chapter 6.2 --- Methodology / Chapter 6.2.1 --- Package of soil columns --- p.89 / Chapter 6.2.2 --- Water addition and extraction of pore water --- p.90 / Chapter 6.2.3 --- Statistical analysis --- p.92 / Chapter 6.3 --- Results and Discussion / Chapter 6.3.1 --- Mineral N in the pore water --- p.92 / Chapter 6.3.2 --- The effect of ash on mineral N in pore water --- p.97 / Chapter 6.3.3 --- The leaching loss of mineral N --- p.98 / Chapter 6.3.4 --- Comparisons with other studies --- p.103 / Chapter 6.4 --- Conclusion --- p.105 / Chapter CHAPTER SEVEN --- Integrative discussion / Chapter 7.1 --- Summary of major findings --- p.107 / Chapter 7.2 --- Clarifying some misconceptions about the effect of fire --- p.110 / Chapter 7.3 --- Estimated losses of N and P from heating --- p.112 / Chapter 7.4 --- Nutrient supplying capacity of soils after heating --- p.115 / Chapter 7.5 --- Why are repeatedly burnt areas reduced to grassland? --- p.118 / Chapter 7.6 --- Implication on the restoration of fire-affected areas --- p.119 / Chapter 7.7 --- Limitations of the study --- p.121 / Chapter 7.8 --- Suggestions for future research --- p.122 / References --- p.124 / Appendices --- p.141

Liu Wing Ting. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 141-156). / Abstracts in English and Chinese. / Abstract (English) --- p.i / Abstract (Chinese) --- p.iii / Acknowledgments --- p.v / List of Tables --- p.vii / List of Figures --- p.ix / List of Plates --- p.x / List of Appendices --- p.xi / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Urban ecological environment and the urban parks in Hong Kong --- p.1 / Chapter 1.2 --- Conceptual framework of the study --- p.4 / Chapter 1.3 --- Objectives of the study --- p.9 / Chapter 1.4 --- Scope of the study --- p.10 / Chapter 1.5 --- Significance of the study --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER 2 --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- Urban parks and urban soils --- p.13 / Chapter 2.3 --- Urban soils: properties and problems --- p.14 / Chapter 2.3.1 --- Overseas studies about urban soils --- p.15 / Chapter 2.3.2 --- Urban soils in Hong Kong --- p.16 / Chapter 2.4 --- Nitrogen dynamics --- p.22 / Chapter 2.4.1 --- The internal N cycle and N transformations in soil --- p.22 / Chapter 2.4.2 --- Factors affecting nitrogen dynamics in soil --- p.24 / Chapter (i) --- "Soil moisture and temperature, seasonality and spatial variation" --- p.24 / Chapter (ii) --- Soil pH and texture --- p.26 / Chapter (iii) --- Litter quality and C:N ratio --- p.26 / Chapter (iv) --- Disturbance --- p.27 / Chapter (v) --- Fertilizer input and management intensity --- p.27 / Chapter 2.4.3 --- N dynamics in urban areas --- p.28 / Chapter 2.4.4 --- Research of N dynamics in Hong Kong --- p.29 / Chapter 2.5 --- Phosphorus dynamics --- p.30 / Chapter 2.5.1 --- Gains and losses of P from soil system --- p.30 / Chapter 2.5.2 --- Forms and transformations of phosphorus in soil --- p.31 / Chapter 2.5.3 --- Factors affecting P dynamics in soil --- p.34 / Chapter (i) --- Fluctuations of soil moisture --- p.34 / Chapter (ii) --- Liming and pH adjustment --- p.34 / Chapter (iii) --- Cultivation and management intensity --- p.35 / Chapter (iv) --- Vegetation cover and disturbances --- p.35 / Chapter 2.5.4 --- P dynamics in urban areas --- p.36 / Chapter CHAPTER 3 --- STUDY AREA / Chapter 3.1 --- General situation of Hong Kong and the study locations --- p.37 / Chapter 3.2 --- Background of the two parks: Kowloon Park and Tin Shui Wai Park --- p.40 / Chapter 3.3 --- Climate --- p.43 / Chapter 3.4 --- Park vegetation --- p.45 / Chapter 3.5 --- Park soils --- p.47 / Chapter 3.6 --- Park management and horticultural routines --- p.47 / Chapter CHAPTER 4 --- BASELINE STUDY OF URBAN PARK SOIL PROPERTIES / Chapter 4.1 --- Introduction --- p.52 / Chapter 4.2 --- Methodology --- p.54 / Chapter 4.2.1 --- Sampling --- p.54 / Chapter 4.2.2 --- Soil texture --- p.55 / Chapter 4.2.3 --- Soil reaction --- p.55 / Chapter 4.2.4 --- Total Kjeldahl nitrogen (TKN) --- p.55 / Chapter 4.2.5 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.55 / Chapter 4.2.6 --- Total phosphorus --- p.56 / Chapter 4.2.7 --- Available phosphorus --- p.56 / Chapter 4.2.8 --- Organic carbon --- p.56 / Chapter 4.2.9 --- "Exchangeable cations (K, Na, Ca, Mg)" --- p.57 / Chapter 4.2.10 --- Carbon: nitrogen ratio and carbon: phosphorus ratio --- p.57 / Chapter 4.3 --- Statistical analysis --- p.57 / Chapter 4.4 --- Results --- p.58 / Chapter 4.4.1 --- Texture --- p.58 / Chapter 4.4.2 --- Soil pH --- p.58 / Chapter 4.4.3 --- Organic matter --- p.59 / Chapter 4.4.4 --- Total Kjeldahl nitrogen and C:N ratio --- p.60 / Chapter 4.4.5 --- Ammonium nitrogen and nitrate nitrogen --- p.61 / Chapter 4.4.6 --- Total phosphorus and C:P ratio --- p.62 / Chapter 4.4.7 --- Available phosphorus --- p.64 / Chapter 4.4.8 --- Exchangeable cations --- p.65 / Chapter 4.5 --- Discussion --- p.66 / Chapter 4.5.1 --- Park soils under different vegetation covers --- p.67 / Chapter 4.5.2 --- Duration of park management and influence of land use outside the parks --- p.72 / Chapter 4.5.3 --- Quality of substrates in Kowloon Park and Tin Shui Wai Park --- p.76 / Chapter 4.5.4 --- C:N ratio and C:P ratio --- p.83 / Chapter 4.6 --- Conclusion --- p.84 / Chapter CHAPTER 5 --- NITROGEN DYNAMICS OF URBAN PARK SOILS / Chapter 5.1 --- Introduction --- p.87 / Chapter 5.2 --- Methodology --- p.89 / Chapter 5.2.1 --- In situ incubation --- p.89 / Chapter 5.2.2 --- "Determination of N mineralization, leaching and uptake" --- p.91 / Chapter 5.3 --- Results --- p.94 / Chapter 5.3.1 --- "Net ammonification, NH4-N leaching and uptake" --- p.94 / Chapter 5.3.2 --- "Net nitrification, NO3-N leaching and uptake" --- p.95 / Chapter 5.3.3 --- "Net N mineralization, N leaching and uptake" --- p.96 / Chapter 5.4 --- Discussion --- p.97 / Chapter 5.4.1 --- Nitrogen mineralization and immobilization --- p.98 / Chapter 5.4.2 --- Comparison with other studies --- p.100 / Chapter 5.4.3 --- Nitrogen leaching and uptake --- p.103 / Chapter 5.5 --- Conclusion --- p.108 / Chapter CHAPTER 6 --- PHOSPHORUS DYNAMICS OF URBAN PARK SOILS / Chapter 6.1 --- Introduction --- p.110 / Chapter 6.2 --- Methodology --- p.112 / Chapter 6.3 --- Results --- p.113 / Chapter 6.4 --- Discussion --- p.115 / Chapter 6.4.1 --- Phosphorus mineralization and immobilization --- p.115 / Chapter 6.4.2 --- Phosphorus leaching and uptake --- p.118 / Chapter 6.4.3 --- Comparison with other studies --- p.120 / Chapter 6.5 --- Conclusion --- p.122 / Chapter CHAPTER 7 --- CONCLUSION / Chapter 7.1 --- Summary of findings --- p.124 / Chapter 7.2 --- Implications of the study --- p.128 / Chapter 7.2.1 --- Chemical characteristics of urban park soils and their relationship to management --- p.128 / Chapter 7.2.2 --- Management practices for different vegetation types and species --- p.133 / Chapter 7.3 --- Limitations of the study --- p.136 / Chapter 7.4 --- Suggestions for future study --- p.139 / REFERENCES --- p.141 / APPENDICES --- p.157