Equilibrium sorption studies of anionic species of arsenite, As(III) ions and arsenate As(V) ions onto two biosorbents, namely, chitosan and nanochitosan, have been investigated and compared. The results and trends in the sorption behavior are novel, and we have observed during the sorption process of the As(III) and As(V) on chitosan, a slow process of desorption occurred after an initial maximum adsorption capacity was achieved, before reaching a final but lower equilibrium adsorption capacity. The same desorption trend, however, is not observed on nanochitosan. The gradual desorption of As(III) and As(V) in the equilibrium sorption on chitosan is attributed to the different fractions of the dissociated forms of arsenic on the adsorbent surface and in solution and the extent of protonation of chitosan with the changing of solution pH during sorption. The change of solution pH during the sorption of arsenite ions on chitosan was also influenced by the interaction between the buffering effect of the arsenite species in the aqueous medium and the physical properties of chitosan. The final equilibrium adsorption capacity of chitosan for As(III) and As(V) was found to be around 500 and 8000 μg/g, respectively, whereas the capacities on nanochitosan are 6100 and 13,000 μg/g, respectively.
An integrated exposure model was developed that estimates nitrogen dioxide (NO(2)) concentration at residences using geographic information systems (GIS) and variables derived within residential buffers representing traffic volume and landscape characteristics including land use, population density and elevation. Multiple measurements of NO(2) taken outside of 985 residences in Connecticut were used to develop the model. A second set of 120 outdoor NO(2) measurements as well as cross-validation were used to validate the model. The model suggests that approximately 67% of the variation in NO(2) levels can be explained by: traffic and land use primarily within 2 km of a residence; population density; elevation; and time of year. Potential benefits of this model for health effects research include improved spatial estimations of traffic-related pollutant exposure and reduced need for extensive pollutant measurements. The model, which could be calibrated and applied in areas other than Connecticut, has importance as a tool for exposure estimation in epidemiological studies of traffic-related air pollution. 相似文献
Environmental Science and Pollution Research - Landfilling is one of the most prevalent waste management strategies on a global scale. However, one major drawback of landfills is the production of... 相似文献
The impact of flood hazard information on public acceptance of a selected flood mitigation strategy was assessed by an analysis of the content of newspaper reports of community reaction and letters to the editor. The impact of personal delivery of a flood hazard map on individual perception of risk and attitude to such information was assessed using personal interviews. The results indicated that media coverage of the flood hazard information reduced public criticism of the works. This result must be partially attributable to the dramatic style of media coverage and the fact that the media only emphasized the positive value of the works. The interview demonstrated that personal delivery of the information raised perception of risk, improved comprehension of flood risk, had no impact on acceptability of risk but discouraged some respondents from seeking such information in the future. Factors to explain the last negative change were identified to be the format of the map sheet and low salience of flood hazard. On the basis of all results, methods to improve community response to hazard information are provided. 相似文献
Summary If males assess potential opponents by comparing their odour with that of scent marks in the vicinity (the so called scent matching hypothesis) they should be more reluctant to fight when these odours are the same. Under these circumstances the potential opponent is thus identified as a resource holder (a male monopolising a territory or group of females) that would escalate encounters to defend its resources. We tested this prediction by comparing the fighting behaviour of male house mice, Mus domesticus, when on a scent-marked substrate that matched the odour of an opponent with their behaviour on a substrate that did not match. As predicted, the delay before the first fight was longer and the rate of subsequent fighting lower when the scents matched. This result is consistent with the interpretation that resource holders scent mark to provide opponents with a means of competitor assessment and that they thus reduce the costs of resource defence.
Offprint requests to: L.M. Gosling 相似文献
Models for the analysis of capture-recapture data based on Erlangian distributions reflecting assumptions about the times at which individuals enter and leave the population are described. A procedure for fitting such models by the method of maximum likelihood is illustrated. 相似文献