Abstram In June 1993 the National Health and Medical Research Council set a national goal for blood lead of below 10 pg/dl. There is a need to know if the lead contamination of the urban environment is so high as to put community health at risk. Decisions, including whether soil should be removed and replaced, will have to be made. During the second half of 1993, an environmental assessment of lead contamination of soil within the City of Newcastle was conducted. Samples, 108 from surface soil and 10 from subsurface soil, were taken from public parks and playgrounds in the city area and analysed for lead content. The proportion within and the proportion above the guidelines for soil contamination were reported. Lead concentrations ranged from 25 to 2400 parts per million (ppm); 21 per cent of samples had concentrations higher than the 300 ppm action level, and the geometric mean was 134 ppm. Both the range and the average lead levels were typically no more than, or were even less than, soi; lead levels documented for other cities in Australia, the United States and United Kingdom. Although each sampling site was noted, it was not our intention to focus in on individual sites. Indeed, to draw health-risk implications from any one result may be misleading and inaccurate. The results indicated moderate lead contamination of soil that could be conirolled by regular topdressing of soils, the use of bark chip on playground surfaces and by government initiatives aimed at lowering lead levels in petrol.

In this study, fly ash cenospheres were added to semisolid AZ91D Mg alloy to prepare fly ash cenosphere/AZ91D (FAC/AZ91D) composites by means of compo-casting. The high-temperature damping capacity of FAC/AZ91D composites was investigated as compared with AZ91D Mg alloy. The results show that the damping capacities of FAC/AZ91D composites and AZ91D Mg alloy strongly depend on the measuring temperature. The FAC/AZ91D composites show better damping capacity than AZ91D Mg alloy. The 10 wt.% FAC/AZ91D composites exhibit the best damping capacity from room temperature to 125°C, whereas the 2 wt.% FAC/AZ91D composites show the highest damping capacity at 125°C–320°C. The damping mechanism was analyzed by microstructure observation at elevated temperatures. The damping-temperature curves exhibit a damping peak at approximately 150°C, and the activation energy of the damping peak was calculated according to the Arrhenius equation. Furthermore, the peak temperature increases with increasing frequencies. The damping peak is related to the thermal activation relaxation process, and its mechanism is the dislocation-induced damping.