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Ho So Man. / Thesis submitted in: July 2005. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 135-148). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGEMENTS --- p.v / TABLE OF CONTENTS --- p.vii / LIST OF TABLES --- p.x / LIST OF FIGURES --- p.xii / LIST OF PLATES --- p.xiii / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- LANDFILLING --- p.1 / Chapter 1.1.1 --- Waste degradation and the by-products --- p.1 / Chapter 1.1.2 --- Restoration works on closed landfills --- p.5 / Chapter 1.1.3 --- Afteruses of closed landfills --- p.10 / Chapter 1.2 --- REVEGETATION ON CLOSED LANDFILLS - COMMON PROBLEMS ENCOUNTERED --- p.10 / Chapter 1.3 --- SOIL DEVELOPMENT ON DEGRADED LANDS --- p.12 / Chapter 1.4 --- NUTRIENT AVAILABILITY OF PLANTS ON CLOSED LANDFILLS --- p.14 / Chapter 1.5 --- ECOSYSTEM DEVELOPMENT ON CLOSED LANDFILLS --- p.16 / Chapter 1.6 --- STUDY SITES --- p.17 / Chapter 1.6.1 --- Climate and weather --- p.17 / Chapter 1.6.2 --- Site description --- p.19 / Chapter 1.6.3 --- Vegetation composition --- p.24 / Chapter 1.7 --- OBJECTIVES AND SIGNIFICANCES OF STUDY --- p.30 / Chapter CHAPTER 2 --- PROPERTIES OF COVER SOIL ON CLOSED LANDFILLS .… --- p.33 / Chapter 2.1 --- INTRODUCTION --- p.33 / Chapter 2.2 --- MATERIALS AND METHODS --- p.35 / Chapter 2.2.1 --- Field measurement and sample collection --- p.35 / Chapter 2.2.2 --- Soil analysis --- p.36 / Chapter 2.2.3 --- Statistical analysis --- p.37 / Chapter 2.3 --- RESULTS AND DISCUSSION --- p.38 / Chapter 2.3.1 --- Landfill gas --- p.38 / Chapter 2.3.2 --- Soil texture --- p.39 / Chapter 2.3.3 --- Bulk density --- p.41 / Chapter 2.3.4 --- pH --- p.42 / Chapter 2.3.5 --- Electrical conductivity --- p.43 / Chapter 2.3.6 --- Organic carbon --- p.44 / Chapter 2.3.7 --- Nitrogen --- p.46 / Chapter 2.3.8 --- Phosphorus --- p.48 / Chapter 2.3.9 --- "Potassium, calcium and magnesium" --- p.50 / Chapter 2.3.10 --- Soil development on degraded land --- p.52 / Chapter 2.4 --- CONCLUSION --- p.54 / Chapter CHAPTER 3 --- LITTERFALL AND THROUGHFALL ON CLOSED LANDFILLS / Chapter 3.1 --- INTRODUCTION --- p.55 / Chapter 3.2 --- MATERIALS AND METHODS --- p.57 / Chapter 3.2.1 --- Collection of throughfall and bulk precipitation --- p.57 / Chapter 3.2.2 --- Collection of litterfall --- p.58 / Chapter 3.2.3 --- Chemical analysis --- p.58 / Chapter 3.2.3.1 --- Bulk precipitation and throughfall --- p.58 / Chapter 3.2.3.2 --- Litter --- p.59 / Chapter 3.2.4 --- Statistical analysis --- p.59 / Chapter 3.3 --- RESULTS AND DISCUSSION --- p.60 / Chapter 3.3.1 --- Bulk precipitation and throughfall --- p.60 / Chapter 3.3.1.1 --- Temporal variation of nutrient deposition --- p.60 / Chapter 3.3.1.2 --- Between site differences in nutrient flux --- p.69 / Chapter 3.3.2 --- Litter production --- p.77 / Chapter 3.3.3 --- Nutrient flux in woodland --- p.84 / Chapter 3.4 --- CONCLUSION --- p.88 / Chapter CHAPTER 4 --- LITTER DECOMPOSITION STUDY ON CLOSED LANDFILL --- p.89 / Chapter 4.1 --- INTRODUCTION --- p.89 / Chapter 4.2 --- MATERIALS AND METHODS --- p.90 / Chapter 4.2.1 --- Collection of litter --- p.90 / Chapter 4.2.2 --- Preparation of litterbag --- p.91 / Chapter 4.2.3 --- Chemical analysis --- p.91 / Chapter 4.2.4 --- Statistical analysis --- p.92 / Chapter 4.3 --- RESULTS AND DISCUSSION --- p.92 / Chapter 4.3.1 --- Initial litter quality --- p.92 / Chapter 4.3.2 --- Litter dry weight loss --- p.95 / Chapter 4.3.3 --- Changes in litter composition --- p.99 / Chapter 4.3.4 --- Nutrient dynamic of decomposing litter --- p.105 / Chapter 4.3.5 --- Litterfall and litter decomposition --- p.108 / Chapter 4.4 --- CONCLUSION --- p.110 / Chapter CHAPTER 5 --- NITROGEN MINERALIZATION ON CLOSED --- p.111 / Chapter 5.1 --- INTRODUCTION --- p.111 / Chapter 5.2 --- MATERIALS AND METHODS --- p.113 / Chapter 5.2.1 --- Soil sampling and incubation --- p.113 / Chapter 5.2.2 --- Chemical analysis --- p.114 / Chapter 5.2.3 --- "Calculation for nitrogen mineralization, plant uptake and leaching loss" --- p.114 / Chapter 5.2.4 --- Statistical analysis --- p.115 / Chapter 5.3 --- RESULTS AND DISCUSSION --- p.116 / Chapter 5.3.1 --- "Net ammonification, nitrification and nitrogen mineralization." --- p.116 / Chapter 5.3.2 --- Leaching loss of mineral nitrogen --- p.126 / Chapter 5.3.3 --- Plant uptake of mineral nitrogen --- p.128 / Chapter 5.4 --- CONCLUSION --- p.129 / Chapter CHAPTER 6 --- GENERAL CONCLUSIONS --- p.131 / REFERENCES --- p.135

Given the prominent role of nitrogen in the eutrophication of aquatic systems, recent increases in nitrogen loading to freshwaters are of concern. A comparison of nitrogen retention in freshwaters in North America and Europe shows that wetlands retain the greatest proportion of their nitrogen load, followed by lakes and then rivers. A comparison of the relative importance of nitrogen retention mechanisms found denitrification to be responsible for the greatest proportion followed by nitrogen sedimentation and then uptake by aquatic plants. A more in-depth examination of denitrification in the littoral sediments of Lake Memphremagog in Quebec, using the N2 flux technique, found an average denitrification rate of 111 mumol N m-2 h-1. Denitrification rates were positively related to the % organic matter of the sediment, temperature and macrophyte biomass density and negatively related to depth. These results, in combination with a review of the literature indicate that denitrification rates are higher in littoral than profundal sediments.

The presence of mosses in black spruce forests is known to have an important impact on the availability and abundance of nutrients in this ecosystem. Mosses contribute to long-term accumulation of organic matter and storage of nutrients as well as to short-term nutrient release. In the boreal forest of northwestern Quebec, the effect of mosses on nutrient cycling was examined within the framework of a chronosequence ranging from 25 to 300 years of age. Laboratory and buried bag incubations, total nutrient digests, respirometric and root abundance measurements as well as moisture and temperature measurements were done to characterize the nutritional status of the organic matter profiles. In general, no change in moss accumulation, or nutrient storage or availability across the chronosequence could be detected. There were, however, differences between feather mosses and Sphagnum mosses, the latter having significantly lower levels of nutrients than the former in terms of mineralizable nitrogen and total carbon, nitrogen, phosphorus, magnesium and potassium content. The nutritional profile of moss cores showed different horizons, reflecting differences in organic matter quality down the organic layer. More specifically, nitrogen availability on a concentration basis as well as root abundance decreased with depth. Forest floor temperature seemed to confine the most biologically active horizon, referred to as the active layer, to a shallow depth, however neither temperature nor moisture seemed to explain the nutritional differences between feather mosses and Sphagnum mosses. These results may lead to practical consequences in that they show a clear distinction between the effects of feather mosses and Sphagnum mosses in nutrient cycling, suggesting that moss cover, might be useful as an indicator of site nutritional status. The results also show that accumulation of nutrients in organic surface horizons, as has been observed elsewhere, does not appear to occur in blac

The release of nutrients (nitrogen and phosphorus) via land clearing, application of fertilisers, discharge of human waste and combustion of fossil fuels, is one of the most harmful effects of anthropogenic stresses on aquatic environments. This study investigated the use of reeds as indicators of nutrient input to estuaries. Small estuaries such as the oligotrophic East Kleinemonde where the research was mostly conducted are sensitive to nutrient enrichment from septic tanks, stormwater runoff and fertiliser application to lawns in close proximity to the estuary. Nutrient concentrations were sampled at different positions, in the groundwater, at the water’s edge, in the reed bed and in the main estuary channel at five sites in the East Kleinemonde Estuary. The NH4+ and SRP concentrations showed a definite trend as concentrations decreased from the groundwater or water’s edge into the main estuary channel. Groundwater introduced nutrients to the estuary which were then taken up by the fringing reeds (Phragmites australis (Cavinelles) Trinius ex Steudel). The water column nutrients were either below detectable limits or in very low concentrations. Low TOxN concentrations were consistently found at the different sites and probably resulted from P. australis assimilating N-TOxN for growth more efficiently than N- NH4+. The roots, rhizomes, stems and leaves of the reeds were measured for δ15N as an indicator of nutrient enrichment as nitrogen stable isotope analysis of plant tissue is an effective method for assessing and monitoring septic tank and other anthropogenic inputs. All plant parts for the three sampling sessions at Site 1 (mouth region) in the East Kleinemonde Estuary had significantly higher δ15N signatures (~20 percent) than the leaves at Site 5 (upper reaches). These differences were related to the surrounding land-use of the East Kleinemonde catchment, where the lower part of the estuary has moderate to low residential development and the upper reaches are utilized mainly for livestock farming. The high δ15N signatures at Site 1 were attributed to septic tank wastewater and stormwater run-off entering the estuary. Nutrient enrichment also influenced the morphology of the reeds. Reed biomass, height and stem density was significantly higher at Site 1 compared to Site 5. Similar studies were conducted in August 2008 in the Sundays Estuary and October 2008 in the nearby Mtati and Mpekweni estuaries to see if the results were similar. iii The same patterns were found where the groundwater NH4+ and SRP concentrations were higher than the estuary channel in the Mtati and Mpekweni estuaries. In the Mpekweni and Sundays estuaries Phragmites australis leaves had high δ15N signatures (10 and 11 percent) similar to that of Site 1 in the East Kleinemonde Estuary. Lower signatures (-2 to +4 percent) were found in the Mtati Estuary. This sampling site was sheltered by a bridge with a steep slope and the concentrations were similar to Site 3 and 5 in the East Kleinemonde Estuary where the derived nutrient was the result of stormwater runoff or fertilisers. Density and biomass of reeds in the Sundays and East Kleinemonde (Site 1) estuaries were similar and this could be related to different nutrient sources, agricultural return flow and septic tank input respectively. Reeds in the Sundays Estuary were significantly taller than in the other estuaries which showed that factors such as shelter and salinity also influence reed growth and therefore morphology alone would not be a good indicator of nutrient enrichment. Indicators of nutrient enrichment are important as the status of temporarily open / closed estuaries in South Africa is threatened by deteriorating water quality. Measurements of the water column may provide an inaccurate assessment of water quality whereas macrophytes are outstanding potential indicators of nutrient enrichment as they are widely distributed, abundant and long-lived. The findings from this study indicate that δ15N concentrations in reeds can be used to indicate nutrient loading.

An ecological reserve study by the Department of Water Affairs on the Great Brak Estuary stated that there was a need to determine how much nitrogen and phosphorus was flowing through the estuary as well as how effective the macroalgae were at removing N and P. The objective of this study was to investigate the physico-chemical characteristics in the estuary and the influence of these on the submerged macrophytes and macroalgae. A nutrient budget for the estuary was developed in order to quantify the contribution of the submerged macrophytes and macroalgae relative to other contributing sources. The Wolwedans Dam located 3 km upstream from the estuary has reduced the amount of freshwater flow to the estuary by as much as 56 percent. The estuary has been allocated 2 x 106 m3 per annum of freshwater (ecological reserve) that is used to breach the mouth once or twice a year in spring or summer. Even though this water has been made available it is not sufficient to flush the estuary. Reduced flushing has led to an accumulation of organic matter and degradation in the water quality. Physico-chemical measurements between September 2010 and July 2012 showed that dissolved oxygen values were generally below 6 mg l-1. The average NH4+ concentration in the estuary was 7 μM and increased with depth to 12 μM at 2 m depths. Concentrations >45 μM were found in February and April 2011 at the 5 m deep hole at 3.4 km upstream. Negative correlations between dissolved oxygen and NH4+ during November 2010, February 2011, April 2011 and July 2011 (r = -0.68; -0.67; -0.63; -0.96) indicated that remineralisation of organic matter had occurred. Soluble reactive phosphorus (SRP) followed a similar trend to the NH4+ and was generally below 1 μM in the water column for most months, and had peaks at 1.0 km and 3.4 km in the bottom water. The abundance of submerged macrophytes and macroalgae below the N2 bridge were mostly influenced by mouth state and river inflow. During the closed phase the dominant macroalga Cladophora glomerata had an area cover ranging from 3000 to 6000 m2 while Zostera capensis and Ruppia cirrhosa covered an area of 2000 to 3500 m2 and 1500 to 2900 m2, respectively. After an artificial breach in February 2011, water drained out of the estuary leaving the alga stranded on the marshes and as the flood tide entered the macroalga was once again redistributed in the lower reaches. The alga utilised the available nutrients in the water column and expanded its area cover from 35000 m2 in February 2011 to 64000 m2 in March 2011. However, after the floods in June 2011, Cladophora glomerata had been washed out of the system while the submerged macrophytes responded positively extending their area cover. By comparing the artificial breach with the natural breach, and the effect on the estuary, an important observation was highlighted. Increasing the current allocated ecological reserve, and using a larger volume of water to breach the mouth artificially, would result in better scouring of sediment and associated organic matter out of the estuary. This would enable better oxygenation of the water column, reduce remineralisation and minimise algal blooms.

Thesis (M.S.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2001. / Includes bibliographical references (leaves 144-149). / A bi-weekly seasonal study was conducted in Ashumet Pond (Cape Cod, Massachusetts). The Redfield Ratio (106C:16N:1P) and alkaline phosphatase activity (APA) were utilized in tandem as nutrient deficiency indicators (NDIs) for phytoplankton. The study objective was to evaluate the limiting nutrient status of the pond throughout the growing season. The development of a high throughput method for fluorometrically measuring APA allowed for a large quantity of pond-water samples to be analyzed. The new method utilized a cytofluor, a fluorescence multi-well plate reader, which increased sample throughput by 75% compared to a standard filter fluorometer method. The detection limit, capability to measure APA at different time intervals, and performance at sea were tested. APA measurements made using the cytofluor were comparable to those made using a standard filter fluorometer, thus indicating that the cytofluor is a suitable and preferred replacement to the fluorometer for APA measurements. The presence of alkaline phosphatase, an inducible phospho-hydrolytic enzyme, is commonly used as an NDI diagnostic for phosphate limitation. A nutrient enrichment incubation re-affirmed the use of APA as a robust indicator of phosphate limitation in phytoplankton. APA data indicate that the system experienced episodic periods of phosphate-deficiency, implying that the limiting nutrient regime was not static, but was changeable throughout the growing season. Seasonal trends in dissolved N:P and particulate C:P ratios often contradict the APA results, however, suggesting that the Redfield Ratio is an unreliable indicator of the overall nutrient limitation regime of the pond. The observed discrepancies between C:N:P and APA can be reconciled by taking into account seasonal changes in species composition, which played an important role in driving seasonal APA trends. / by Christie Lynn Haupert. / M.S.

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