Repeated use of two Chlorella species, C. vulgaris and WW1 for cyclic nickel biosorption.

Two living Chlorella species were used to remove nickel from solution containing 30 micrograms Ni ml-1 in 10 successive cycles. The present study also examined the continued viability of these two algal species after repeated exposure to nickel. The two species of Chlorella were Chlorella vulgaris (commercially available) and WW1 (indigenous species isolated from domestic sewage and was tentatively identified as Chlorella miniata). The nickel removal percentage of WW1 cells was maintained at around 85% in the first five cycles, then declined slightly from the fifth cycle onwards, and finally achieved around 70% removal at the end of the 10th cycle. On the contrary, the removal efficiency of C. vulgaris declined from 50 to 30% during the 10 cycles of nickel bisorption. At the end of these 10 successive cycles, WW1 accumulated a substantial amount of Ni2+ (the cumulative cellular Ni concentration was 0.92% dry w.), while the value was only 0.17% in the case of C. vulgaris. These results suggest that the local isolate, WW1, had more consistent and satisfactory ability for removing Ni than the commercial C. vulgaris. Both algal species were still capable of dividing after each nickel treatment cycle, suggesting that the cells were not killed even when significant amounts of nickel were adsorbed/absorbed. However, Ni exposure adversely affected the physiological activity of algal cells as reflected by the decline in division rate and chlorophyll-a activity in both species. Such negative effects became more obvious as the number of cyclic treatments was increased. Nevertheless, WW1 cells appeared to recover from nickel treatment when re-cultivated in commercial medium for 2 weeks.     

The effectiveness of DustBubbles on dust control in the process of concrete drilling

Construction dust is one of the most concerned pollutants presenting risks to human health. Dust generated from concrete drilling, particularly true for silica dust, have an adverse effect on the health of workers. There is a long-term concern about the overexposure of construction workers to respirable crystalline silica. The high exposure to silica, even over a short period, can lead to silicosis. In order to control the dust generated during the process of concrete drilling, a local Hong Kong contractor has implemented DustBubble during the concrete drilling works. In order to evaluate the effectiveness of this new dust control measure, an experimental study has been designed and conducted. The respirable dust and silica dust concentrations of the following two situations were compared: workers drilling concrete with and without the use of DustBubble. Personal respirable samples were collected and analysed based on NIOSH 0600 and 7500 methods. The results revealed that DustBubble could significantly reduce the respirable dust exposure by 63%. However, there was no evidence that the use of DustBubble could reduce the respirable quartz exposure.     

Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions

A study on the modification of rice husk by various carboxylic acids showed that tartaric acid modified rice husk (TARH) had the highest binding capacities for Cu and Pb. The carboxyl groups on the surface of the modified rice husk were primarily responsible for the sorption of metal ions. A series of batch experiments using TARH as the sorbent for the removal of Cu and Pb showed that the sorption process was pH dependent, rapid and exothermic. The sorption process conformed to the Langmuir isotherm with maximum sorption capacities of 29 and 108 mg/g at 27 +/- 2 degrees C for Cu and Pb, respectively. The uptake increased with agitation rate. Decrease in sorbent particle size led to an increase in the sorption of metal ions and this could be explained by an increase in surface area and hence binding sites. Metal uptake was reduced in the presence of competitive cations and chelators. The affinity of TARH for Pb is greater than Cu.     

The environmental awareness of environmental protection bureaucrats in the People's Republic of China

Summary Over 180 environmental protection bureaucrats in the People's Republic of China were individually interviewed to determine their environmental awareness and their attitudes towards the environment. The study indicates that environmental protection bureaucrats in China have conflicting attitudes towards the relationship between man and nature, and between economic growth and environmental protection. However, they show a strong faith in science and technology's ability to solve environmental problems. The perception that too-harsh environmental protection regulations would reduce the growth potential of the economy is so predominant that it poses a serious threat to the environment of the three municipalities under investigation. It is argued that environmental management is a matter of managing human beings. To understand people, it is imperative to gain a thorough understanding of their worldview.Dr Koon-Kwai Wong is an Associate Professor in the Department of Geography and the Geography option co-ordinator on the China Studies course at Hong Kong Baptist University. Dr Hon S. Chan is an Associate Professor in the Department of Public and Social Administration at the City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong.