硫化砷渣全湿法制备单质砷的研究

以硫化砷渣为原料,用氯化铜酸性溶液浸出砷渣的全湿法进行实验,着重研究氯化铜浸出砷的过程中氯化铜用量、溶液p H和浸出时间对砷浸出率的影响,探讨用氯化亚锡还原砷盐酸溶液从硫化砷渣得到单质砷的方法。     

Interplay between Senecio jacobaea and plant, soil, and aboveground insect community composition

To elucidate the factors that affect the performance of plants in their natural environment, it is essential to study interactions with other neighboring plants, as well as with above- and belowground higher trophic organisms. We used a long-term field experiment to study how local plant community diversity influenced colonization by the biennial composite Senecio jacobaea in its native range in The Netherlands in Europe. We tested the effect of sowing later-succession plant species (0, 4, or 15 species) on plant succession and S. jacobaea performance. Over a period of eight years, the percent cover of S. jacobaea was relatively low in communities sown with 15 or 4 later-succession plant species compared to plots that were not sown, but that were colonized naturally. However, after four years of high abundance, the density of S. jacobaea in unsown plots started to decline, and the size of the individual plants was smaller than in the plots sown with 15 or 4 plant species. In the unsown plots, densities of aboveground leaf-mining, flower-feeding, and stem-boring insects on S. jacobaea plants were lower than on plants in sown plots, and there was a strong positive relationship between plant size and levels of herbivory. In a greenhouse experiment, we grew S. jacobaea in sterilized soil inoculated with soil from the different sowing treatments of the field experiment. Biomass production was lower when S. jacobaea test plants were grown in soil from the unsown plots than in soil from the sown plots (4 or 15 species). Molecular analysis of the fungal and bacterial communities revealed that the composition of fungal communities in unsown plots differed significantly from those in sown plots, suggesting that soil fungi could have been involved in the relative growth reduction of S. jacobaea in the greenhouse bioassay. Our results show that, in its native habitat, the abundance of S. jacobaea depends on the initial composition of the plant community and that, on a scale of almost a decade, its interactions with plant and soil communities and aboveground invertebrates may influence the dynamics of this colonizing species.     

Removal of polycyclic aromatic hydrocarbons from aged-contaminated soil using cyclodextrins: experimental study

The removal of polycyclic aromatic hydrocarbons (PAHs) from soil using water as flushing agent is relatively ineffective due to their low aqueous solubility. However, addition of cyclodextrin (CD) in washing solutions has been shown to increase the removal efficiency several times. Herein are investigated the effectiveness of cyclodextrin to remove PAH occurring in industrially aged-contaminated soil. Beta-cyclodextrin (BCD), hydroxypropyl-beta-cyclodextrin (HPCD) and methyl-beta-cyclodextrin (MCD) solutions were used for soil flushing in column test to evaluate some influent parameters that can significantly increase the removal efficiency. The process parameters chosen were CD concentration, ratio of washing solution volume to soil weight, and temperature of washing solution. These parameters were found to have a significant and almost linear effect on PAH removal from the contaminated soil, except the temperature where no significant enhancement in PAH extraction was observed for temperature range from 5 to 35 degrees C. The PAHs extraction enhancement factor compared to water was about 200.     

Integrated Ecological and Regional Planning in a Rapid-Growth Setting

Toronto is among the fastest-growing urban regions in North America. Regional efforts to preserve rural landscapes and remnant habitat have had variable success. In the 1990s, significant conflict emerged over proposals to build large housing developments on portions of the Oak Ridges Moraine, a 160-km stretch of environmentally sensitive land along the city’s northern edge. After years of planning conflict, Ontario’s provincial government created the Oak Ridges Moraine Conservation Plan, an Act of the Ontario Legislature. The Plan represents a dramatic change in Ontario’s approach to conservation planning. We examine the development and implementation of the Conservation Plan as an example of environmental planning policy in a complex urban setting. Data from interviews with policy actors, planning agency documents, and geospatial sources are used to construct an analysis and discussion of the Plan and its implementation. From a policy research perspective, the evolution and implementation of the Plan require analysis and monitoring to better understand how such approaches can best be implemented. The Conservation Plan marks a change in policy in Ontario, and the implementation process highlights challenges in putting conservation plans into practice.