High-recycled-content hydraulic cements of alternative chemistry for concrete production

Sustainable hydraulic cements based on alkali aluminosilicate chemistry were developed with market-limited wastes acting as the primary aluminosilicate precursors. Two sets of formulations were developed with waste brick or impounded coal ash used at relatively large volume as aluminosilicate precursors. Supplementary materials were used to produce raw materials of viable chemistry. Blends of raw materials were transformed into hydraulic cements by input of mechanical energy without resorting to elevated temperatures. The resultant hydraulic cements exhibited viable strength development characteristics. FTIR, SEM, EDS and NMR analyses were conducted in order to gain insight into the structure of the hydraulic cements and their hydration products. The results pointed at the prevalence of calcium aluminosilicate hydrates among the products of hydration which thoroughly bound the non-hydrated cores of cement particles.     

Numerical studies on minimum ignition energies in methane/air and iso-octane/air mixtures

In this study, the dependence of minimum ignition energies (MIE) on ignition geometry, ignition source radius and mixture composition is investigated numerically for methane/air and iso-octane/air mixtures. Methane and iso-octane are both important hydrocarbon fuels, but differ strongly with respect to their Lewis numbers. Lean iso-octane air mixtures have particularly large Lewis numbers. The results show that within the flammability limits, the MIE for both mixtures stays almost constant, and increases rapidly at the limits. The MIEs for both fuels are also similar within the flammability limits. Furthermore, the MIEs of iso-octane/air mixtures with a small spherical ignition source increase rapidly for lean mixtures. Here the Lewis number is above unity, and thus, the flame may quench because of flame curvature effects. The observations show a distinct difference between ignition and flame propagation for iso-octane. The minimum energy required for initiating a successful flame propagation can be considerably higher than that required for initiating an ignition in the ignition volume. For iso-octane with a small spherical ignition source, this effect was observed at all equivalence ratios. For iso-octane with cylindrical ignition sources, the phenomenon appeared at lower equivalence ratios only, where the mixture's Lewis number is large. For methane fuel, the effect was negligible. The results highlight the significance of molecular transport properties on the decision whether or not an ignitable mixture can evolve into a propagating flame.     

我国冰川水资源状况及开发利用途径

我国是冰川水资源拥有大国之一。本文对我国冰川水资源特性、冰水化学特征及开发利用进行了综合分析论述。指出冰川水资源是以固体水库效应为基础的水资源体系,有必要重新认识冰川的水资源价值,并进一步开展冰川应用基础研究,为合理开发利用和保护冰川水资源提供依据。     

Man-made chemicals found in remote areas of the world: the experimental definition for POPs

Members of the United Nations Economic Commission for Europe (UN-ECE) signed a legally binding protocol on persistent organic pollutants (POPs) in February 1998 under the Convention on Long-Range Transboundary Air Pollution. A treaty that intends to control the production, import, export, disposal and use of toxic chemicals that persist for decades in the environment has been formally signed at a conference in May 2001 in Stockholm. The 2001 POP treaty, like the 1998 LRTAP POP protocol, contains a provision on adding further chemicals to the initial group of twelve or fifteen. The occurrence of a compound or a group of compounds in so called remote and pristine areas, e.g. in the Artic or in the Southern Hemisphere, proves its stability under the chemical and biological conditions of the environment. Compounds identified in this way, in samples taken primarily in very remote regions of the planet, are classified by their environmental fate and global distribution as persistent organic pollutants (POPs), regardless of any political assessments.     

Does improved waste treatment have demonstrable biological benefits?

Since 1972, 10 benthic surveys and 9 static fish bioassays have been conducted to assess the impact of AVTEX Fibers, Inc. effluent on the lower South Fork of the Shenandoah River. AVTEX (formerly FMC Corp.) is a rayon and polyester fibers plant located in Front Royal, Virginia. Benthic samples were taken at four stations, one above and three below the plant discharges. Single surveys in 1972 and 1973 indicated a severe impact on the benthic community along the right side of the river, below the plant, as a result of the channelized effluent. Diversity values (¯d) were low (0–2.42) and numbers of taxa and organisms were reduced. A fish bioassay in 1973 indicated the effluent to be acutely toxic at the 34.5% level (mixture of effluent and river water). In early 1974, FMC Corp. constructed an activated sludge treatment system to reduce BOD and supplement the neutralization and chemical precipitation (zinc hydroxide and liquid-solid separation) facilities that had been used to treat waste waters since 1948. After the new equipment was placed in operation, the previously stressed area became more stable. In 1975 and 1976 the stressed area exhibited greater ¯d values (1.19–3.39) and an increased number of taxa and organisms. Bioassays showed the effluent to be acutely toxic to fish only once since 1973. The major improvements in the effluent were a 70% reduction in BOD₅ and a 60% reduction in the amount of zinc entering the river. Community conditions in 1977 indicated a partial remission of improvement, probably due to drought conditions.The rehabilitation of damaged ecosystems is a process important to all biologists. An important factor in encouraging industry to participate in this activity is evidence that improved waste treatment will often have demonstrable biological benefits rather soon. As data accumulate on the recovery process it may be possible to predict the degree of rehabilitation and time required more precisely.     

IMPACT OF COAL SURFACE MINING AND RECLAMATION ON SURFACE WATER CHEMICAL CONCENTRATIONS AND LOAD RATES IN THREE OHIO WATERSHEDS1

ABSTRACT: Information is lacking on the watershed scale effects of mining and reclaiming originally undisturbed watersheds for coal on surface water chemical concentrations and load rates for a variety of constituents. These effects were evaluated on three small, geologically dissimilar watersheds subjected to surface mining in Ohio. Comparisons were made between phases of land disturbances using ratios of average concentrations and load rates: Phase 1 (natural), subphases of Phase 2 (mining and reclamation), and subphases of Phase 3 (partial reclamation and final condition) using 4,485 laboratory analyses of 34 constituents. Average concentration and load rate ratios were categorized into three classes—minor, moderate, and substantial. Mining and reclamation (M/R) affected flow duration curves in different ways‐baseflow changes were variable, but high flows generally increased. The average concentration ratios for all sites were classified as 15 percent “minor,” 36 percent “moderate,” and 49 percent “substantial” (average ratio of 2.4.) Generally load rate ratios increased due to mining and reclamation activities (average ratio of 3.3). Minor, moderate, and substantial impacts were found on average for 7 percent, 23 percent, and 70 percent, respectively, of load rate ratios. The impact of M/R on average load rates was not necessarily the same as on average concentrations due to changed hydrology and can be opposite in effect. The evaluation of the impacts of M/R requires knowledge of changing hydrologic conditions and changing supplies and rates of release of chemicals into streams. Median sediment concentration ratio is an indicator of average constituent load rate ratio of a wide variety of chemical constituents and is useful for development of best management practices to reduce chemical loads. The site at which diversion ditches were not removed during final reclamation sustained large chemical load rates, and removal of diversions at the other mined site reduced load rates. Revegetation of poorly reclaimed areas decreased chemical load rates. Chemical load rates were sensitive to geology, mining, and reclamation methods, diversions, and changing hydrology, concentration flow rate regressions, and watershed areas.     

The Sensitivity of Headwater Streams in the Hindu Kush Himalayas to Acidification

Water, Air, &; Soil Pollution: Focus - The mountain ecosystems of the Hindu Kush Himalayas are generally considered to be pristine despite little available data to confirm it. Is there any...     

Restoration of a Small High Mountain Lake after Recent Tourist Impact: The Importance of Limnological Monitoring and Palaeolimnology

The natural Park of Peñalara consists of a small mountainousarea near Madrid and includes a series of water bodies (fromsmall mountain lakes to temporary ponds and peat bogs), the mostknown of them being the so-called `Laguna Grande dePeñalara'. Due to growing numbers of visitors theenvironmental conditions of this lake started to decline in theearly 1970s because of: (1) the start of severe soil erosionprocesses; (2) the increase of nutrient load; and (3) theintroduction of a non-native fish species. Since the area wasprotected in 1990, several conservation and restoration projectsincluded in an integrated management plan have been developed. Here we summarise some of the results of these efforts: (1) controlled access of livestock and visitors to the area; (2) palaeolimnology studies aimed at inferring recent changes in thewatershed; and (3) monitoring of the limnological features of thesystem. Restoration of this lake and its watershed is intendedto serve as a model for the management of other severely alteredhigh mountain lakes.     

瓦屋山附着凌冰的化学成分研究

为研究附着凌冰的化学成分及其与大气环境污染的关系。2001年12月，在位于瓦屋山2600米处的山顶采集了树枝上的附着凌冰，并对其所含阴离子的组成进行了测定。分析结果表明：凌冰中各阴离子含量都很低，pH为3．5属强酸性未被中和。酸性物质的起源与燃煤以外的因素有关。