膨润土颗粒吸附剂的制备及废水中铅离子的处理研究

通过振荡吸附实验,研究了膨润土颗粒吸附材料的制备方法及颗粒吸附材料在含铅离子废水中的吸附特性.结果表明,颗粒化的最佳条件为:膨润土颗粒粒径2mm,焙烧温度550℃,焙烧时间1h.在温度25℃、pH值为6、Pb2+初始浓度为50mg/L、吸附剂用量为8g/L、吸附时间为60min时,吸附剂对废水中Pb2+的吸附去除率达90%以上,吸附剂对Pb2+ 的吸附符合Langmuir吸附方程.     

粉煤灰—膨润土颗粒吸附材料的制备及其处理含铅离子废水的研究

通过振荡吸附实验,研究了粉煤灰-膨润土颗粒吸附材料的制备方法及颗粒吸附材料在含铅离子废水中的吸附特性.结果表明,制备颗粒吸附剂的优化条件为:粉煤灰∶膨润土=5∶5(质量比),在600℃下焙烧2h.在温度25℃、pH值为5、Pb2+初始浓度为40mg/L、吸附剂用量为2g/L、吸附时间为1h条件下,吸附剂对废水中Pb2+的去除率可达95.27%.     

TiO2改性柱撑膨润土吸附副品红的性能研究

以钠基膨润土为原料，制备了4种二氧化钛（TiO2）改性柱撑膨润土，并探讨了膨润土的改性方法、投土量、吸附时间、温度及pH值等因素对吸附副品红性能的影响。结果表明：4种TiO2改性柱撑膨润土对副品红的吸附效果明显好于原土；未经煅烧的TiO2改性柱撑膨润土的吸附效果要明显优于经高温煅烧过的柱撑膨润土；掺杂钇的TiO2改性柱撑膨润土的吸附性能略好于未经掺杂的柱撑膨润土；膨润土投土量、吸附时间、温度和pH值均会对柱撑膨润土的吸附效果产生影响；20℃时，4种柱撑膨润土对溶液中副品红的吸附等温线均符合Langrnuir吸附等温方程。     

改性钛管基复合吸附剂及其在油田伴生气中CO_2脱除的应用

通过湿式浸渍法制备了胺改性复合吸附剂用于油田伴生气中的CO_2捕集回收。采用物理吸附仪(BET-BJH)、热重分析仪(TG)考察了复合吸附剂的微观结构和热稳定性;通过等温吸附曲线研究了胺改性钛管对CO_2的吸附特性和对CH4/CO_2的吸附选择性。实验结果表明,胺改性复合吸附剂适用于150℃下的操作环境,在75℃时对CO_2的吸附容量可高达110mg/g;其对CO_2的吸附符合准二级动力学模型。40PEI/HTO对CO_2亲和性强,是分离CO_2/CH4的优异吸附剂。     

城市剩余污泥制备吸附剂的研究及其应用

以城市污水处理厂的剩余污泥为原料,采用化学活化法制备活性碳污泥吸附剂.通过对比不同活化剂活化效果,并对影响活化产物吸附性能的因素进行了研究.结果表明以3mol/L的ZnCl2为活化剂,活化温度为550℃,固液比为1:2.5,热解时间2h,制备的活性碳吸附剂吸附碘值为317.4mg/g,活性炭吸附剂比表面积为232.526m2/g.采用制备的活性碳吸附剂处理模拟废水COD去除效果较好.     

典型天然吸附剂对重金属的吸附性能研究

天然吸附剂由于其本身结构的特殊性,对重金属离子有一定的吸附效果,但是原始的吸附剂在工程处理应用中有一定的局限性,如耐酸碱性不高、吸附量不大等,因此在实际应用中采用较多的典型吸附剂多为改性材料,改性后的吸附剂提高了对环境的耐受性和对金属离子的吸附量,对于去除和回收水体中重金属有很大的优势和发展前景。     

壳聚糖处理印染废水的研究

在不同的壳聚糖浓度、pH和温度条件下，采用分光光度法测得吸附后染料的浓度，得到了壳聚糖对染料的最佳吸附条件，结果为：壳聚糖的投入量在红3B为2％，兰2BG和黄3GE为3％时，pH8．4在碱性范围内，温度为50℃效果最佳。其结果将为壳聚糖在印染废水处理提供一定的理论基础。     

LDO处理垃圾渗滤液中氮的实验研究

研究了复合金属氧化物（LDO）用于处理垃圾渗滤液中氮的可行性,并与传统吸附剂粉末活性炭（PAC）进行了比较,考察了投加量、振荡速度、吸附时间、吸附温度、pH等因素对处理效果的影响。结果表明,当垃圾渗滤液中总氮浓度为561mg/L、LDO投加量为6g/L、振荡速度为170r/min、吸附时间为60min、温度为25℃、pH值为11时,LDO对总氮的吸附量最高,达到41mg/g。在相同条件下,LDO对总氮的吸附量是PAC的2.5—3.5倍。     

氨基改性MCM-41对阴离子染料酸性品红的吸附研究

采用3-氨丙基三甲氧基硅烷对MCM-41进行氨基功能化修饰,并以此作为吸附剂(NH2-MCM-41)来去除阴离子染料废水酸性品红(AF)。应用平衡吸附法,重点考察了溶液的p H值、吸附剂的投加量、吸附时间以及染料的初始浓度对吸附效果的影响,并采用吸附等温线和动力学模型进行吸附机理分析。实验得出:溶液的p H值对吸附效果影响较大,染料的去除率随着吸附剂质量、反应时间的增加而上升,随染料初始浓度的增加而下降。Langmuir模型对染料的等温吸附行为拟合效果最好,吸附动力学符合准二级动力学模型。解吸附研究得出NH2-MCM-41有较好的解吸附效果和重复使用率。氨基改性后的MCM-41对AF有良好的吸附效果,可以作为一种新型高效的吸附剂进一步用于阴离子染料废水治理。     

不同分子量壳聚糖锌配合物对尿素的吸附行为研究

研究了壳聚糖-Zn配合物对尿素的吸附行为和壳聚糖分子量对尿素吸附性能的影响.正交试验结果表明,壳聚糖-Zn对尿素的吸附最佳组合为A<,5>B<,4>C<,3>D<,4>,即尿素溶液的初始浓度为3.5mg/mL,反应温度为55℃,pH值为4.5,反应时间为7h时,壳聚糖-Zn对尿素的吸附量达到最大值260.414mg/g.在同一条件下,壳聚糖分子量对壳聚糖-Zn吸附尿素能力影响的大小顺序为50kDa＞10kDa＞5kDa.     

Provincial development plans in Zimbabwe: an analysis of their content,structure and methodology

Zimbabwean provincial plans were instituted to help in the achievement of the national goal of the creation of an egalitarian, socialist and integrated society. The national goal itself was adopted as an antithesis to the dualist society characterised by spatial, economic, social, politican and technological inequalities that Zimbabwe inherited from colonialism. This meant that provincial plans had to play both a functional (or growth allocating/distribution) and a territorial (or redistribution) role.

This paper reviews their role in achieving the national goal by examining their functions, content, structure and methodology. The paper concludes that because of their nature, provincial plans are not suitable tools for the achievement of the national goal.     

BIOLOGICAL INDICATORS AND BIOLOGICAL EFFECTS OF ESTUARINE/COASTAL POLLUTION1

ABSTRACT: Sustained interest in and concern about the health status of the aquatic environment has resulted in extensive research focused on (1) effects of pollution on survival, growth, and reproduction of resource species at all life stages; (2) diseases of fish and shellfish, as they may be related to pollution and as they may serve as indicators of environmental stress; and (3) contaminant body burdens in fish and shellfish - their effects on the aquatic animals and their potential effects on humans. Effects, lethal and sublethal, of pollutants on life history stages of fish and shellfish have been documented, as have impacts on local stocks in badly degraded habitats, but as yet there has been no adequate quantitative demonstration of effects on entire aquatic species - probably because of the difficulty in sorting out relative effects of the many environmental factors that influence abundance. Sublethal effects, especially those that result in disease, have been examined intensively, and some diseases and disease syndromes have been associated statistically with pollution. Other pollution indicators (biochemical, physiological, genetic, behavioral, and ecological) have also received some attention, as have body burdens of contaminants in aquatic species. Research, especially that conducted during the past decade, has done much to clarify the many pathways and toxic effects of contaminants on aquatic animals, and has also helped to identify mechanisms for survival of fish and shellfish in the presence of environmental changes caused by human activities.     

Definition Procedures Have Little Effect on Performance of Environmental Classifications of Streams and Rivers

Mapped environmental classifications are defined using various procedures, but there has been little evaluation of the differences in their ability to discriminate variation in independent ecological characteristics. We tested the performance of environmental classifications of the streams and rivers of France that had been defined from the same environmental data using geographic regionalization and numerical classification of individual river valley segments. Test data comprised invertebrate assemblages, water chemistry, and hydrological indexes obtained from sites throughout France. Classification performance was measured by analysis of similarity (ANOSIM). Geometric regions defined by a regular grid and without regard to environmental variables and a posteriori classifications based on clustering the test datasets defined lower and upper bounds of performance for a given number of classes. Differences in classification performances were generally small. The ANOSIM statistics for the a posteriori classifications were around twice that of all environmental classifications, including geometrically defined regions. The hydro-ecoregions performed slightly better for the invertebrate data and the network classification performed slightly better for the chemistry and hydrological data. Our results indicate that environmental classifications that are defined using different procedures can be comparable in terms of their ability to discriminate variation of ecological characteristics and that alleged differences in performance arising from different classification procedures can be small relative to unexplained variation. We conclude that definition procedures might have little effect on the performance of large-scale environmental classifications and decisions over which procedures to use should be based primarily on pragmatic considerations.     

Journalists' views of advertiser pressures on agricultural news

All major journalism ethical codes explicitly state that journalists should protect editorial copy from undue influence by outside sources. However, much of the previous research on agricultural information has concentrated on what information various media communicate (gatekeeping studies) or communication's role in increasing innovation adoption (diffusion studies). Few studies have concentrated specifically on organizational and structural constraints that might adversely affect agricultural journalists' ethical standards; those that have, focus largely on farm magazines. A study of newspaper reporters who cover agricultural news found that the most pressing ethical concern is the effect of advertiser (agri-business) pressure on editorial copy, and that their concerns in general parallel those of farm magazine writers and editors. The majority reported being in situations in which they might be exposed to advertiser pressure, including pressures to change or withhold editorial copy. Large minorities suggested that advertising pressures affect the overall environment in which agricultural journalists work, and more than one in ten said they allow advertiser pressures to influence editorial decisions. The newspaper reporters who cover agricultural beats showed slightly more resistance to advertiser pressure than did farm magazine editors in a parallel study.     

National minerals policies and stakeholder participation for broad-based development in the southern African development community (SADC)

This paper explains how the well-accepted concept of improved stakeholder participation during mineral policy development leads to a national mineral policy that accommodates the diverging views and interests that allows wide acceptance of decisions, enhancing the success of implementation and, ultimately, national benefits. This process is based on lessons learnt during the South African experience and has been successfully applied in the development of the Namibian and Malawian national minerals policies. An effective policy in the SADC will engineer the delicate balance between poverty reduction and an internationally competitive minerals sector. This balance enhances the possibility of long-term economic growth and development in the SADC region. The overriding advantage of this strategy is that it generates ‘home-grown’ policy instruments and implementation of mineral law with which stakeholders can identify. This process presents a new challenge to traditional policy formulation strategies in emerging economies and the bottom-up approach, linked to wide political support, allows the potential realisation of national objectives.     

Effect of Light on Biodegradation of Estrone, 17β‐Estradiol,and 17α‐Ethinylestradiol in Stream Sediment

Biodegradation of [A‐ring ¹⁴C] Estrone (E1), 17β‐estradiol (E2), and 17α‐ethinylestradiol (EE2) to ¹⁴CO₂ was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A‐ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for ¹⁴C‐E2. Net mineralization of ¹⁴C‐E1 and ¹⁴C‐EE2 was enhanced in light treatments. Extents of ¹⁴CO₂ accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light‐limited environments. The extent of ¹⁴CO₂ accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, ¹⁴CO₂ accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation.     

Bioremediation of Soils by Plant–Microbe Systems

Abstract

Sustainable ecosystems can be designed to eliminate environmental toxins and reduce pathogen loads through the direct and indirect consequences of plant and microbial activities. We present an approach to the bioremediation of disturbed environments, focusing on petroleum hydrocarbon (PHC) contaminants. Treatment consists of incorporating a plant-based amendment to enhance ecosystem productivity and physiochemical degradation followed by the establishment of plants to serve as oxidizers and foundations for microbial communities. Promising amendments for widespread use are entire plants of the water fern Azolla and seed meal of Brassica napus (rapeseed). An inexpensive byproduct from the manufacture of biodiesel and lubricants, rapeseed meal is high in nitrogen (6% wt/wt), stimulates >100-fold increases in populations of resident Streptomyces species, and suppresses fungal infection of roots subsequently cultivated in the amended soil. Synergistic enzymatic and chemical activities of plant and microbial metabolism in root zones transform and degrade soil contaminants. Emphasis is given to mechanisms that enable PHC functionalization via reactive molecular species.     

A DISTRIBUTED DYNAMIC WATERSHED MODEL1

ABSTRACT: A distributed watershed model was developed to mathematically simulate overland and channel flow for a single-event storm. The modeled watersheds in the study were subdivided into rectangular grid elements. All hydrologically significant parameters, such as land slope, rainfall and precipitation excess, were assumed to be uniform within each element. The Green-Ampt method was adopted to generate precipitation excess for each element during the simulation period. A two-dimensional diffusion wave model was used for overland flow routing and an iterative Alternative Direction Implicit scheme was used to solve the simultaneous overland flow equations. Once the overland flow became inflow to the channel, a one-dimensional dynamic wave flood routing technique, based on a four-point, implicit, non-linear finite difference solution of the St. Venant equation of unsteady flow, was applied. A limited number of comparisons were made between simulated and observed hydrographs for areas of about one square mile. Given the appropriate parameters, the model was able to accurately simulate runoff for single-event storms. This paper describes a distributed watershed model developed to simulate overland and channel flow. Comparisons were made between simulated and observed hydrographs for three watersheds. The model was able to accurately simulate the runoff for single-event storms using 61-m by 61-m (200 ft by 200 ft) watershed grid elements.     

Energetics and environmental costs of agriculture in a dry tropical region of India

The present article, based on a study of five village ecosystems, assesses the energy efficiency of rain-fed agriculture in a dry tropical environment and the impact of agricultural activity on the surrounding natural ecosystems. Agronomic yield is insufficient to meet the food requirement of the human population, hence 11.5%–49.7% of the required amount of food grains are imported from the market. Energy requirements of five studied agroecosystems are subsidized considerably by the surrounding forest in the form of fodder and firewood. Natural ecosystems supply about 80%–95% of fodder needs and 81%–100% of fuelwood needs. The output-input ratio of agriculture indicated that, on average, 4.1 units of energy are expended to obtain one unit of agronomic energy. Of this, 3.9 units are supplied by the natural ecosystem. In addition, 38% of the extracted firewood is marketed. The illegal felling and lopping of trees result in ever-increasing concentric circles of forest destruction around the villages and together with excessive grazing results in savannization. The forests can be conserved by encouraging fuelwood plantations (0.7 ha/ha cultivated land) and developing village pastures (1.6 ha/ha cultivated land) and reducing the livestock numbers. Agricultural production in the region can be stabilized by introducing improved dry farming techniques such as intercropping, planned rainwater management, and adequate use of fertilizers.     

INTEGRATED WATER RESOURCES MANAGEMENT WHO SHOULD LEAD,WHO SHOULD PAY?1

ABSTRACT: Improving water management to meet future global needs will certainly require technical advances, but the main challenge is to integrate the viewpoints of diverse societal interests into decisions about allocation of water resources. The integration cannot be done solely by the market because it requires a balancing among interests which do not respond well to market forces, nor by the state alone because of institutional problems. The concept of “integrated water resources management” has been developed to provide the framework for the required balancing of interests, and, like similar concepts in industries other than water, it has a dual purpose - to link stakeholders and apply best practices to management actions. To clarify the process of integrated water management, the paper focuses on two questions: who should lead integrated water resources management and who should pay for it? Several examples are given to illustrate a range of situations. The paper concludes with a call to improve paradigms of integrated water management, a proposition that water organizations should accept and budget for their external responsibilities as well as their direct missions, affirmation of the need for state and federal agencies to be involved with local interests, a call for better scientific and public information, and identification of the need for continued work to improve the process of integrated water management.