The distribution and impacts of different nitrogen pollutants are inextricably linked. To understand the problem fully, the interactions between the different pollutants need to be taken into account. This is particularly important when it comes to abatement techniques, since measures to reduce emissions of one nitrogen pollutant can often lead to an increase in another. This project represents a step towards greater understanding of these issues by linking together new and existing nitrogen flux models into a larger framework. The modelling framework has been constructed and some of the nitrogen flows between fields, farms and the atmosphere have been modelled for a UK study area for typical farm management scenarios. 相似文献
A 50 ha known contaminated site in Bayonne, New Jersey, U.S.A. is permitted to receive up to 3 × 106 m3 of sediment dredged from navigation channels in the New York/New Jersey Harbor. Much of the sediment is expected to contain low to moderate concentrations of industrial and agricultural chemicals, including Polychlorinated Biphenyls (PCBs). The dredged material brought to the site is stabilized with cement and then placed as a capping and grading layer. The flux of PCBs from drying stabilized dredged material has been estimated from measurements of PCB air concentrations at two heights above the ground along with micrometeorological observations. A statistically significant gradient in PCB concentrations has been consistently measured in the first 3 m above the ground. Observed PCB fluxes were highest over freshly placed stabilized dredged sediment and decreased as it cured. The highest flux observed in this study was 7214 ng/m2/h, but during subsequent sampling intervals at the same site, the flux estimates decreased by an order of magnitude over a 5-day interval. 相似文献
In this investigation, all the techniques used in the chemical recycling of polyethylene terephthalate (PET) are critically reviewed according to the overall benefits together with the environmental surcharge that they cause. Those, which are consistent with the principles of sustainable development, are indicated. Experimental data are presented for the acid hydrolysis of PET and compared with previous results on the alkaline hydrolysis of PET with, or without, the use of a phase transfer catalyst. Overall material balances are carried out for the hydrolysis of PET. Finally, it can be postulated that recycling according to the scheme: is the only one within the framework of sustainable development. Therefore, the recycling of PET does not only serve as a partial solution to the solid waste problem but also contributes to the conservation of raw petrochemical products and energy. 相似文献
The assessment of collection systems for municipal wastes is becoming an issue of increasing importance among local authorities. This paper contributes to this task by addressing and discussing a set of parameters that are characterizing certain aspects of the efficiency and effectiveness of the waste collection process. Case-study area for testing this set is the Thessaloniki Urban Area in Northern Greece. Specifically, a set of four evaluation indicators is initially discussed and quantified for each of the 14 considered municipalities, while the multiple-criteria decision support method of Analytical Hierarchy Process is finally applied to globally rank the municipalities. As a result, a classification of all examined municipalities is derived and various conclusions are drawn on certain efficiency and effectiveness aspects of waste collection systems. 相似文献
Brazil produces approximately 242,000 t of waste per day, 76% of it being dumped outdoors and only 0.9% recycled, including composting, which is an alternative still little known in Brazil. In search of a better destination for residues produced by domestic activities, composting stands as a feasible alternative. Organic compost from waste may be used for various purposes, among which are soil recovery, commercial production, pastures, lawns and reforestry and agriculture. However, the quality of the compost determines the growth and the development of plants. The effect of compost made from urban waste on corn plant (Zea mays L.) growth was investigated. Two types of compost were used: the selected compost (SC), produced from organic waste selectively collected; and the non-selected compost (NSC), taken from a 15-year-old cell from the Canabrava land-fill, located in Salvador, Bahia, Brazil (altitude 51 m, 12°22′–13°08′S, 38°08′–38°47′W). Corn was seeded in polyethylene pots, with soil-compost mixing substrate in the proportion of 0, 15, 30, 45 and 60 t ha−1 equivalent doses. Chemical analyses of the compost and growth properties of the plant like chlorophyll content; height and stem diameter; aerial and radicular dry biomasses, were used to evaluate compost quality. Plants cultivated with SC presented a superior gain, being of 52.5% in stem diameter, 71.1 and 81.2% in root and stem biomasses, respectively. Chlorophyl content alterations were observed in plants from treatments using 30 t compost ha−1 dose onwards. Conventional and multivariate statistical methods were used to evaluate these results. The beneficial action of organic compost in plant growth was confirmed with this research. 相似文献
The Bhopal tragedy was a defining moment in the history of the chemical industry. On December 3, 1984, a runaway reaction within a methyl isocyanate storage tank at the Union Carbide India Limited pesticide plant released a toxic gas cloud that killed thousands and injured hundreds of thousands. After Bhopal, industrial chemical plants became a major public concern. Both the public and the chemical industry realized the necessity of improving chemical process safety.
Bhopal served as a wake-up call. To prevent the same event from occurring in the United States, many legislative and industrial changes were invoked—one of which was formation of the U.S. Chemical Safety and Hazard Investigation Board (CSB). The ultimate goal of CSB is to use the lessons learned and recommendations from its investigations to achieve positive change within the chemical industry—preventing incidents and saving lives.
Although it seems clear that the lessons learned at Bhopal have improved chemical plant safety, CSB investigations indicate that the systemic problems identified at Bhopal remain the underlying causes of many incidents. These include:
• Lack of awareness of reactive hazards.
• Lack of management of change.
• Inadequate plant design and maintenance.
• Ineffective employee training.
• Ineffective emergency preparedness and community notification.
• Lack of root cause incident investigations and communication of lessons learned.
The aim of this paper is to present common themes from recent cases investigated by CSB and to discuss how these issues might be best addressed in the future.
This paper has not been independently approved by the Board and is published for general informational purposes only. Any material in the paper that did not originate in a Board-approved report is solely the responsibility of the authors and does not represent an official finding, conclusion, or position of the Board. 相似文献
The results from three long-term field manipulation studies of the impacts of increased nitrogen deposition (0–120 kg N ha?1 yr?1) on lowland and upland heathlands in the UK were compared, to test if common responses are observed. Consistent increases in Calluna foliar N content and decreases in litter C:N ratios were found across all sites, while increases in N leaching were not observed at any site over the range 0–80 kg ha?1 yr?1. However, the response of Calluna biomass did vary between sites, possibly reflecting site differences in nutrient status and management histories. Five versions of a simulation model of heathland responses to N were developed, each reflecting different assumptions about the fate and turnover of soil N. Model outputs supported the deduction from mass balance calculations at two of the field sites that N additions have resulted in an increase in immobilisation; the latter was needed to prevent the model overestimating measured N leaching. However, this version of the model significantly underestimated Calluna biomass. Model versions, which included uptake of organic N by Callunaand re-mobilisation of N from the soil organic store provided some improvement in the fit between modelled and field biomass data, but re-mobilisation also led to an overestimation of N leaching. Quantification of these processes and their response to increased N deposition are therefore critical to interpreting experimental data and predicting the long-term impacts of atmospheric deposition on heathlands and moorlands. 相似文献