Determination and analysis of sorption of 137Cs to soils in Hong Kong reservoir.

Soils from a local reservoir had been analyzed for their physical and chemical properties, distribution coefficients Kd and sorption rates for 137Cs. It was found that soils in Hong Kong were relatively low in organic matter and more acidic than those in some other countries. In sorption experiments, the rates of decrease in water activity concentration were initially very high, higher for larger mass of soils added, and then slowed down. The larger the mass, the shorter was the time for equilibrium. Three isotherms had been obtained by varying one of the three parameters (initial water activity concentration, slurry ratio and particle size) at a time. For constant initial water activity concentration and random sizes, percent sorption increased with slurry ratio. For soils of constant mass and random sizes. percent sorption decreased with increasing initial water activity concentration. For constant initial water activity concentration and slurry ratio, percent sorption increased with decreasing size of soil particles. A simple logistic model was developed to explain some of the findings.

Hair analysis of spastic children in Hong Kong.

Hair samples of 20 spastic children and 29 normal children were collected and measured, using neutron activation analysis and X-ray fluorescence techniques, for the concentrations of Al, Sb, As, Ca, Cu, I, Fe, Pb, Mg, Mn, Hg, K, Sr, S, V and Zn. Both groups of children were of ages between 5 and 13. The washing method of using detergent and powder was found to be comparable to that of using ether. Difference in the mean concentration of each element in the two groups was tested by the Student's t-test and the Wilcoxon rank-sums test. Hair concentrations of Al, Sb, Pb, Mn, K, Sr, and V in the 'spasm group' were found to be significantly (P < 0.05) higher than those in the 'normal group'. Attempt was made to interpret the effects of these elements on the nervous and muscular systems of the spastic children.

Radionuclide contents in building materials used in Hong Kong.

The radionuclide contents of conventional natural raw building materials, coal ash and slag, and finished building products have been determined using gamma-ray spectrometry. Results of brick measurements in their original geometry and in crushed form are compared. The radioactive concentrations in cement and sand, mostly imported from China, are among the lowest measured. However, due to the high radioactivity of aggregates, composed of granite mainly extracted locally, the mean Ra equivalent activity of concrete is high compared with that in some countries. The radioactivity levels of coal ash and slag in Hong Kong are about the average values in other countries. The incorporation of coal ash and slag in ordinary concrete does not alter the radioactivity significantly.

Modeling and measuring the indoor randon concentrations in high-rise buildings in Hong Kong.

A newly constructed, uninhabited high-rise building has been measured for its indoor and outdoor radon concentrations at similar locations on each of the 18 floor levels. Grab sampling technique has been used so that many locations can be measured within short period of time to minimize the variations due to temperature, pressure and humidity. Air exchange rates inside rooms were obtained by tracer gas method. Standard concrete samples were manufactured in laboratory to simulate the concrete used in the construction of the high-rise building. The concrete samples were measured for their radon exhalation rates by calculating the initial growth rates of radon inside an airtight container. The air exchange rates have been found to increase with floor levels, whilst the indoor and outdoor radon concentrations decreased with floor levels. Using a model utilizing a simple mass balance equation, the indoor radon concentration inside a room on each of the 18 floor levels has been calculated and the results agreed very well with measurements.

Uptake of 137Cs by fresh water fish.

The uptake and discharge rates of 137Cs by fresh water fish at different radionuclide concentrations have been studied. A dual compartment model was used to fit the experimental data. The discharge rates have been found to be negligible for the duration of the experiment of 10 d. The uptake rates were independent of radionuclide concentrations for a particular type of fresh water fish and were different for different types of fish. The uptake rates of carp, tilapia and snakehead were 1.58, 1.66 and 2.23, in unit of 10(-6) h-1, respectively. It was also estimated that the consumption of fresh water fish, even if the water were contaminated as much as that in the Chernobyl accident, leads to negligible latent cancer fatality to the Hong Kong population.