Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems

Zeolitic materials have been prepared from coal fly ash as well as from a SiO₂–Al₂O₃ system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin–Kaganer–Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.     

Long-Term Effects of Changing Land Use Practices on Surface Water Quality in a Coastal River and Lagoonal Estuary

The watershed of the Neuse River, a major tributary of the largest lagoonal estuary on the U.S. mainland, has sustained rapid growth of human and swine populations. This study integrated a decade of available land cover and water quality data to examine relationships between land use changes and surface water quality. Geographic Information Systems (GIS) analysis was used to characterize 26 subbasins throughout the watershed for changes in land use during 1992–2001, considering urban, agricultural (cropland, animal as pasture, and densities of confined animal feed operations [CAFOs]), forested, grassland, and wetland categories and numbers of wastewater treatment plants (WWTPs). GIS was also used together with longitudinal regression analysis to identify specific land use characteristics that influenced surface water quality. Total phosphorus concentrations were significantly higher during summer in subbasins with high densities of WWTPs and CAFOs. Nitrate was significantly higher during winter in subbasins with high numbers of WWTPs, and organic nitrogen was higher in subbasins with higher agricultural coverage, especially with high coverage of pastures fertilized with animal manure. Ammonium concentrations were elevated after high precipitation. Overall, wastewater discharges in the upper, increasingly urbanized Neuse basin and intensive swine agriculture in the lower basin have been the highest contributors of nitrogen and phosphorus to receiving surface waters. Although nonpoint sources have been emphasized in the eutrophication of rivers and estuaries such as the Neuse, point sources continue to be major nutrient contributors in watersheds sustaining increasing human population growth. The described correlation and regression analyses represent a rapid, reliable method to relate land use patterns to water quality, and they can be adapted to watersheds in any region.     

Requisite Simplicities to Help Negotiate Complex Problems

Decision makers responsible for natural resource management often complain that science delivers fragmented information that is not useful at the scale of implementation. We offer a way of negotiating complex problems by putting forward a requisite simplicity. A requisite simplicity attempts to discard some detail, while retaining conceptual clarity and scientific rigor, and helps us move to a new position where we can benefit from new knowledge. We illustrate the above using three case studies: elephant densities and vegetation change in a national park, the use of rules of thumb to support decision making in agriculture, and the management of salt in irrigation. We identify potential requisite simplicities that can allow us to generate new understanding, lead to action and provide opportunities for structured learning.     

What-You-Look-For-Is-What-You-Find – The consequences of underlying accident models in eight accident investigation manuals

Accident investigation manuals are influential documents on various levels in a safety management system, and it is therefore important to appraise them in the light of what we currently know – or assume – about the nature of accidents. Investigation manuals necessarily embody or represent an accident model, i.e., a set of assumptions about how accidents happen and what the important factors are. In this paper we examine three aspects of accident investigation as described in a number of investigation manuals. Firstly, we focus on accident models and in particular the assumptions about how different factors interact to cause – or prevent – accidents, i.e., the accident “mechanisms”. Secondly, we focus on the scope in the sense of the factors (or factor domains) that are considered in the models – for instance (hu)man, technology, and organization (MTO). Thirdly, we focus on the system of investigation or the activities that together constitute an accident investigation project/process. We found that the manuals all used complex linear models. The factors considered were in general (hu)man, technology, organization, and information. The causes found during an investigation reflect the assumptions of the accident model, following the ‘What-You-Look-For-Is-What-You-Find’ or WYLFIWYF principle. The identified causes typically became specific problems to be fixed during an implementation of solutions. This follows what can be called ‘What-You-Find-Is-What-You-Fix’ or WYFIWYF principle.     

事故调查分析方法与技术述评

根据事故的原因结果模型、过程模型、能量模型、逻辑树模型、SHE管理模型将事故调查分析技术方法归纳为5大类,介绍了广泛使用的事故调查分析技术方法的特点,并按一定的标准进行分析和比较。分析表明:每种方法都有其不同的应用领域和优缺点,应针对不同领域问题选用合适的分析方法,多种调查技术组合分析适用于复杂事故的调查;考虑事件次序及其影响因素的调查方法,便于提出预防事故再次发生和减少风险的建议,图表阐述有利于鉴别信息缺陷,并使调查组之间的沟通有力;笔者在调查过程中注重于非正常分析方法得出的结果,宜采用更为先进的事故分析技术方法以保证事故调查的客观性。     

Removal of carbon disulfide via coupled reactions on a bi-functional catalyst: experimental and modeling results

A mathematical model describing the rate of carbon disulfide (CS₂) removal due to coupled reactions has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and a range of temperatures (85–125 °C). The effects of flow rate, CS₂ inlet concentration, temperature and relative humidity were analyzed. A kinetic model based on axial dispersion, external and internal mass-transfer resistances, as well as effects of S deposition on the inner-face of the catalyst was in agreement with the CS₂ experimental breakthrough curves. The mathematical model can be used for process design and scale up of similar systems.     

养分(磷)吸收机理模型的应用研究──Ⅱ.模型参数的敏感性分析

采用Claassen的养分吸收机理模型探讨了玉米与大豆幼苗磷吸收过程中的参数敏感性,结果表明：在一般土壤与施肥条件下,玉米与大豆幼苗吸收磷的高度敏感性参数或重要限制因素为根系伸长速率与根半径;在相同土壤供磷条件下,供试大豆幼苗根系的磷摄取能力远低于玉米幼苗根系的磷摄取能力,其原因归结于两者在根系最大养分流Imax与根系伸长速率K两个敏感性参数上的差异;玉米与大豆幼苗磷吸收过程中三种根毛参数的敏感性均较低,这主要与土壤供磷水平较高有关;土壤含水量在玉米幼苗磷吸收过程中表现了极高的敏感性,当土壤含水量降低时,土壤养分供应参数对玉米幼苗磷吸收的敏感性与限制作用均增大。     

Regression Analysis Model Applied to Biomonitoring Studies

A regression model is proposed for studying the relationship between trace metals concentrations and weights of individuals of Monodonta turbinata (Born), a gastropod mollusc used as a trace metal biomonitor of marine coastal areas. The model herein presented was developed including sites as reference factors and showed very good correlations. The prevision model of contamination gave good results for this kind of pollutants, and it can be used as a tool for monitoring programmes.     

基于遥感和Markov模型的新疆生产建设兵团土地利用变化

通过对兵团土地利用空间格局变化分析,选择合适的土地利用政策保护生态环境。运用RS和GIS技术对兵团近10年土地利用/覆被变化及景观格局空间变化进行分析,并在此基础上运用Markov模型对未来30年土地利用变化进行预测。2000—2010年,新疆生产建设兵团景观多样性升高,连通性增强,形状愈来愈简单,景观格局整体变化不大;草地、灌丛、湿地、荒漠和冰川/永久积雪面积减少,耕地和城镇面积增加,森林保持稳定;人为干扰对土地利用结构的变化具有重要作用,土地利用强度受人为活动影响的同时受土地利用政策影响;在未来30年间耕地和城镇面积继续增加,除森林基本保持不变外其他土地利用类型均减小。兵团城镇用地与草地和耕地之间的矛盾逐渐显现,势必引起兵团生态格局的变化。因此,必须实行合适的土地利用政策保护环境。     

Modeling Waste Incineration for Life-Cycle Inventory Analysis in Switzerland

This paper proposes a mathematical model for life-cycle inventory analysis (LCI) of waste incineration in Switzerland. In order to model conventional and new incineration technologies adequately, fundamental aspects of the different technologies relevant for the LCI are discussed. The environmental impact of these technologies strongly depends on the assessment of the long-term emissions of the solid incineration residues and is therefore related to value based decisions about the time horizon considered. The article illustrates that the choice of the landfill model has a significant influence on the results of life-cycle assessment of waste incineration.