Sai Leung Ng

Behavioral response of Indo-Pacific humpback dolphin (Sousa chinensis) to vessel traffic

A series of land-based surveys were conducted at two vantage points of known dolphin abundance in Hong Kong. The purpose of this study was to determine the behavioral response of Indo-Pacific humpback dolphin (Sousa chinensis) to vessel traffic. Results indicated that dolphins dove for a longer duration in areas of heavy vessel traffic or when there was the presence of an oncoming vessel. Dependent upon the type of vessel and the relative distance, dolphins might flee, continue their ongoing activity, perform a new activity, or approach the vessel. Whilst slow-moving vessels appeared not to cause immediate stress on the dolphin community, fast-moving vessels often cause disruption of behavior and social life. In order to ensure a better environment for the animals, we suggest that proactive conservation measures such as the creation of a marine park, rules and regulations for dolphin watching activities, and regional control of vessel speed should be implemented.

Magnetic properties and heavy-metal contents of contaminated seabed sediments of Penny's Bay, Hong Kong

Magnetic properties and heavy-metal concentrations of vibrocore samples were found to be potential indicators of shipping contamination in seabed sediments in Hong Kong Harbour. Geochemical results of 74 vibrocores located off Pennys Bay on Lantau Island revealed an enrichment of heavy metals in the upper 1-2 m of the cores within the eastern part of the study site. Whole-core magnetic susceptibility measurements also showed a greater concentration of magnetic particles in the surficial layer of these cores. A significant correlation exists between the magnetic susceptibility and the concentrations of Pb, Zn and Cu, as well as the Tomlinson pollution load index (PLI). The proximity of these cores to a major navigation fairway and an anchorage site suggests probable contamination of the surficial seabed sediments by shipping-related wastes. A study of the magnetic properties of one of the cores, VT60, revealed a difference in the magnetic properties between the contaminated and the uncontaminated sediments. Samples from the contaminated zone exhibited relatively stronger magnetic remanence and susceptibility. The two groups of samples also formed distinct trends on the hysteresis ratios plot. A level of unusually high magnetic susceptibility within the contaminated zone was attributable to the presence of strongly magnetized granules, which were probably refuse from shipping-related activities. Geochemical and magnetic results were also conducted on samples of different size-fractions from this core. The < 63 microns fraction was found to contain a relatively higher magnetic susceptibility and greater heavy-metal content.

HEAVY METAL CONTENTS AND MAGNETIC PROPERTIES OF PLAYGROUND DUST IN HONG KONG

This study examined the levels of seven heavy metals (namelyzinc, copper, cadmium, chromium, lead, manganese and iron) andtheir associations with magnetic properties in playground dustof Hong Kong. Results showed that the playground dust containedhigh concentrations of Zn (mean = 1883 μg g-1), Cu(mean = 143 μg g-1) and Cr (mean = 263 μg g-1).Qualitative examination of dust samples under microscope indicated local traffic as one of the important pollutant sources. Magnetic measurements indicated that these anthropogenicpollutants mainly consisted of coarse-grained multidomain (MD) ferrimagnetic minerals. Superparamagnetic (SP), stable single domain (SSD) ferrimagnetic grains and non-ferrimagnetic mineralswere present in relatively small amounts. Significant correlations between heavy metals and various magnetic parametersindicated a strong affinity of heavy metals to magnetic minerals hence pointed out the potential of magnetic properties for simpleand rapid proxy indications of heavy metal pollution in playground dust.

A diatom model for inferring sea level change in the coastal waters of Hong Kong

Diatoms were identified and enumerated from surface sediments of 25 sites in Double Haven, Hong Kong. The relationship between diatom species distribution and 14 environmental variables was examined using Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA). Water depth was identified as the most important environmental variable influencing the distribution of diatoms in Double Haven. Subsequently a Weighted Average (WA) calibration model was developed to infer water depth. The reliability of the model was evaluated by the error of prediction (RMSEboot= 3.479) and the correlation (r2= 0.7342) between observed and diatom-inferred values. This predictive calibration model has the potential to infer past sea level change in Hong Kong and the adjacent coastal areas.

Development of a diatom-based specific conductivity model for the glacio-isostatic lakes of Truelove Lowland: implications for paleoconductivity and paleoenvironmental reconstructions in Devon Island lakes, N.W.T., Canada

Diatoms are identified and enumerated from the surface sediments of 100 lakes of Truelove Lowland, Devon Island, N.W.T., Canada. These lakes range from large oligotrophic lakes, to small tundra ponds, to coastal marine lagoons which are diverse in terms of ionic concentration and composition. The relationship between diatoms and 15 limnological variables is examined using Canonical Correspondence Analysis (CCA). Specific conductivity is identified as the most important variable influencing the distribution of diatoms in the Truelove lakes. A Weighted Averaging (WA) calibration model is developed to predict diatom-inferred specific conductivity. The reliability of the model is tested by evaluating the correlation between observed and diatom-inferred values and determining the error of prediction by bootstrapping. The applicability of the predictive conductivity equation is demonstrated by reconstructing the paleoconductivity history of Fish Lake.

Estimation of Effective Roughness for Water-Worked Gravel Surfaces

AbstractThere is no accepted standard equation for predicting flow resistance in gravel rivers. This is mainly because of the lack of an effective approach for describing the roughness of the gravel surface. This paper aims at describing the roughness of gravel surfaces based on characteristics of the elevation field rather than conventionally used grain size distribution. A new parameter—the coarseness parameter—in addition to the steepness parameter and standard deviation of the elevation field is proposed for characterizing the roughness of gravel surfaces. Two groups of rough surfaces (A and B) were generated using unconditional Gaussian simulation to study the influence of the coarseness and steepness parameters on effective roughness. The effective roughness of groups A and B was calculated by a two-equation turbulence model, and a quantitative relationship between the effective roughness and proposed parameters was derived. The resulting relationship derived from groups A and B was validated using ...

Scaling Behavior of Gravel Surfaces

Roughness of successively developed gravel surfaces in flume experiments is investigated using laser scanned elevation fields. Scaling behavior of these surfaces is studied using structure functions. The results show that all surfaces exhibit good scaling behavior for two scaling regions. Multifractal analysis based on singular measures is then conducted for the two scaling regions, respectively. The relatively smaller scaling region characterizing subgrain scale roughness exhibits evident nonstationarity and intermittency. In contrary, the measures for the larger scaling region characterizing the spatial distribution of grains are more stationary and less intermittent than the measures for the subgrain scaling region.

Multifractal characterization of water-worked gravel surfaces

This study investigates the roughness of water-worked gravel surfaces using stable gravel-beds armoured in flume and field experiments. As an alternative to traditional approaches, multifractal analysis is employed to investigate the roughness of these surfaces. Power spectra analysis is used to study scale-invariant regimes, defined by the ranges of scales where the spectra follow power laws. Then, multifractal spectra are calculated and analysed. The strength of multifractality reflecting heterogeneity of elevations is related to the development of a stable armour layer. The development of armouring processes of the gravel surfaces formed in the flume experiments is investigated using the effective grain size approach based on Gesslers model. For surfaces in the field, the two-dimensional second-order structure function is used to study the static armour surfaces due to the absence of historical hydrological data. The results of these analyses confirm the results of multifractal analyses.

Living environment and quality of life in Hong Kong

ABSTRACT Population growth and urbanization have resulted in the emergence of mega cities in recent decades. While compact urban fabrics and high residential density imply intensive interactions between man and environment, the living environment may be one of the most important factors affecting quality of life (QOL) of city dwellers. With this in mind, this paper seeks to understand the manners in which the residents relate themselves to the places they live and how they derive neighborhood and QOL, in such way that the relationship between living environment and QOL can be understood. A random telephone survey (N = 1,114) was conducted in Hong Kong. Results showed that different levels of neighborhood satisfaction varied in residents of different housing types and living environment was a significant predictor of resident’s QOL. Other than the architecture of housing, this paper highlights the importance of services and facilities for the development of social relations and community building. This paper may supplement to the Western QOL studies and provide reference for urban planning initiatives for Asian cities.

Hong Kong Geopark: a paradigm of urban sustainable tourism

Geotourism is a form of sustainable tourism that specifically focuses on geology and landscape. Geotourism has five essential characteristics, namely, being geologically based, environmentally sustainable, informative, beneficial and tourist-satisfactory. In the recent decade, many countries have set up geoparks as a means to promote geotourism and nature conservation. A geopark is a designated area where outstanding and rare geological landforms are protected and where a sustainable economic development strategy is in place. Hong Kong Geopark was open in 2009 as an urban geopark established in the setting of a densely populated metropolis. Because of proximity, Hong Kong Geopark integrates with the city to form a geopark-city tourism system in such a way that the park and the city play separate but complementary roles in the development of geotourism. The major aim of this paper is to examine the relationship between Hong Kong Geopark and geotourism and explain how the park achieves sustainable tourism.