Kin-Che Lam

Home sweet home? A case study of household dust contamination in Hong Kong

It is well recognized that many heavy metals have chronic effects on humans and as such, they are potential environmental health hazards, particularly to young children (see, for example, Body P, Inglis G, Dolan P, Mulcahy D. Environmental lead: a review. Crit Rev Environ Control 1991;20:299-310). Considerable attention has been paid to the study of metal pollution in city air, roadside dusts and soils. However, there is a lack of concern of the presence of trace metals in house dust in the populous city of Hong Kong, where it has traditionally been assumed that such pollutants are rapidly dispersed by ocean breezes. This research aims at quantifying the concentrations of heavy metals within the home environment in Hong Kong and their relationships with environmental factors. The results of this study seem to suggest that traffic and the age of the building and neighborhood are more important factors than the types of industry and socioeconomic status in affecting household dust contamination. The metal burdens in Kwung Tong, an old area with heavy traffic, are significantly higher than other districts. When a Kruskal-Wallis one-way analysis of variance was performed on the ranked metal concentrations in different housing districts, the Chi-square values are all significant at a probability level of < 0.001. This might be attributable to the fact that there is no highly contaminating industries (such as metal smelters, battery plants and petrochemicals) in Hong Kong. The dust metals may travel from the roads, through the windows and balconies, into the houses, as those homes that do not have their windows opened often had a lower level of contaminants in their house dust (median Cd= 3.6 microg/g; median Cu = 313.2 microg/g; median Pb = 144.6 microg/g; median Mn = 211.6 microg/g; and median Zn = 1,333.7 microg/g). Moreover, those occupants who sweep their floors or dust their furniture on daily bases, or use vacuum cleaners, had a lower level of metals inside their houses. Another finding of interest is that the color of the wall paint used in the house may be another factor influencing the contamination levels.

A GIS based road traffic noise prediction model

Abstract A road traffic noise prediction model has been developed suitable for use in China. This model is based on local environmental standards, vehicle types and traffic conditions. The model was accurate to 0.8 dBA at locations near the road carriage way and 2.1 dBA within the housing estate, which is comparable to the FHWA model. An integrated noise-GIS system was developed to provide general functions for noise modeling and an additional tool for noise design, where a new interaction mode in “WHAT IF Question/Explanation” format was used. Application of this system offered improvements in the efficiency and accuracy of traffic noise assessment and noise design.

Urban noise surveys

Abstract Despite the large number of urban noise surveys which have been conducted to date, there are considerable weaknesses in the large body of data that such surveys have collected. For example, there are little data available which allow comparison of the acoustic environment of one city, or the noise exposure of its residents, with those of another. This is symptomatic of past approaches to urban noise surveys in which there has been misunderstanding of the nature of the urban acoustic environment to be measured and confusion resulting from multiple survey objectives. The major problem is that most survey results have been reported mainly as site-specific data. A review of 20 past survey procedures shows that the surveys can be categorized into four types: random sampling, sampling by land-use category, receptor-oriented sampling and source-oriented sampling. Various weaknesses in the different types are examined and it is suggested that several survey types and various survey objectives are incompatible. Receptor-oriented surveys would appear to offer the best opportunity for gathering noise level data which can be generalized from site-specific information to the exposure of a population. Disaggregation of noise by source type during a measurement programme could make the collection of noise data in urban noise surveys more efficient.

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.

Phosphorus retention and release by sediments in the eutrophic Mai Po Marshes, Hong Kong.

This study examined the phosphorus retention and release characteristics of sediments in the eutrophic Mai Po Marshes in Hong Kong. Results of chemical fractionation show that the sum of inorganic P pools exceeded 50% of the total sediment P content, with the redox-sensitive iron-bound P (Fe(OOH) approximately P) being the dominant P fraction. Given the considerable average Fe(OOH) approximately P concentration of 912 microg g(-1), Mai Po sediments demonstrated a great potential to release bioavailable P under low sediment redox potentials. This was further supported by the high mean anaerobic P flux of 31.8 mg m(-2)d(-1) recorded in Mai Po sediment cores, indicating the role of bottom sediments as a net P source. Although sediments in Mai Po had appreciable Langmuir adsorption maxima (1642-3582 mg kg(-1)), the high zero equilibrium P concentrations (0.02-0.51 mg L(-1)) obtained suggest that sediment sorption processes would contribute to sustaining the eutrophic conditions in overlying water column even with a further reduction in external P load. Concerted efforts should be made to reduce internal loading of P, especially under reducing conditions, to complement the implementation of zero discharge policy for Deep Bay for effective eutrophication abatement and long-term water quality improvement in the Mai Po Marshes.

Are nursery schools and kindergartens safe for our kids? The Hong Kong study

Pediatric heavy metal (particularly lead) poisoning is a widespread, yet preventable problem in many parts of the world. Interior floor dust is found to be one of the major pathways of childhood exposure. However, school and health authorities in most countries do not have any stipulations nor guidelines in regulating heavy metal contamination in floor dusts in schools. This study attempts to examine the level of heavy metal contamination in 53 nursery schools and kindergartens in Hong Kong and study its relationship with the environmental factors. The results of this study reveal that the arithmetic mean level of lead in exterior dust is 280.01 mg/kg, with a minimum level of 48.80 mg/kg and a maximum of 2108.31 mg/kg, which is somewhat lower than other studies, such as those reported by Chan et al. (Biomed. Environ. Sci. 1989;2:131-140) and Akhter and Madany (Water Air Soil Pollut. 1993;66:111-119), but those of the manganese (mean = 532.16 mg/kg, range = 102.51-1736.25 mg/kg) and zinc levels (mean = 2694.23 mg/kg, range = 898.33-9899.85 mg/kg) are much higher. Out of the 10 districts examined, Kwun Tong and North Point are found to be the most polluted. They are older districts with polluting industries and heavy traffic. The results of the analysis of variance suggest that the heavy metal particulate may originate from the exterior. Auto-vehicles are a likely source. The toxins are blown inside through the opened windows. Other factors that may affect the content of metal in floor dusts are the time since the school was last painted, the age of the housing complex, the condition of the school and the use of vacuum cleaners.

Synoptic typing and its application to the assessment of climatic impact on concentrations of sulfur dioxide and nitrogen oxides in Hong Kong

Abstract Principal components analysis and average linkage clustering procedure are used to automatically classify seasonal distinctive synoptic categories based on 6-hourly surface meteorological data for Hong Kong. This procedure is able to identify the specific categories exhibiting particularly high mean pollution concentrations and producing high frequency of severe pollution events. It is found that high SO2 and NOx concentrations are usually associated with the certain spring and summer air masses with moderate to strong southwesterly or westerly winds as well as related to the autumn and winter synoptic categories with light northerly or easterly winds. This procedure has a potential to forecast air pollution concentrations, which could be achieved through predicting the arrival of the most polluted synoptic categories.

A synoptic climatological approach to forecast concentrations of sulfur dioxide and nitrogen oxides in Hong Kong.

The objective of this study is to develop an automated synoptic climatological procedure to forecast high air pollution concentrations in the most polluted synoptic categories. The procedure is able to identify air masses historically associated with high air pollution concentrations. The arrival of air mass can be predicted 24 or 48 h in advance with the use of the weather forecast data. The development and statistical basis of the procedure are discussed, and an analysis of the procedures ability to forecast weather conditions associated with high air pollution concentrations is presented. In addition, the dataset of 24 weather variables from 1993 to 1995 is used to validate the procedure. The procedure predicts that 70.3 and 83.3% of total high and severe SO2 concentration days fall into the identified most polluted categories, and the corresponding figures for NOx are 47.8 and 73.7%. The agreement between observed and predicted values is generally good. The prediction models can explain about 58 and 45% of total variance for NOx and SO2 with RMSEs of 42.5 and 16.5 microg m(-3), respectively. They are smaller than 1 SD of the observations.

Human Preference for Countryside Soundscapes

Human evaluation of soundscapes has been postulated to depend on whether sounds are wanted or unwanted in a particular context, rather than on simple metrics of sound level. A study was undertaken in the countryside of Hong Kong to determine how visitors evaluate soundscapes and what factors influence their preferences. A questionnaire survey was undertaken at 44 locations in different parts of the countryside of Hong Kong representing all major soundscape types. The results indicate that human preference is not statistically related to common acoustical and psychoacoustical metrics. Higher correlations are found between human preference scores and the absence or presence of wanted and unwanted sounds. This finding contributes to our understanding of human evaluation of countryside soundscapes, enhancing our ability to plan and manage the outdoor acoustic environment.

STRATEGIC ENVIRONMENTAL ASSESSMENT IN CHINA: OPPORTUNITIES, ISSUES AND CHALLENGES

Based on literature reviews, case studies and other information available on the web, this paper examines the evolution and status of strategic environmental assessment in China by reviewing the progress that has been made; discussing the issues and problems encountered and exploring the best way forward. It is suggested that the Chinese EIA system has evolved over the years to cope with the rapidity and scale of development in China and the current emphasis on Plan EIA is probably the most appropriate form of SEA given the political reality and complicated institution setup. Given Chinas environmental and resource problems, the paper affirms the potential role of SEA in fostering a sustainable and harmonious society and the need to mainstream sustainability considerations in the formulation of national plans and strategies. To circumvent political resistance from line agencies, the paper suggests that SEA can be applied, in various names and forms, to national and provincial socio-economic plans.