用氮气和戊基黄药浮选时黄铁矿的低电位疏水状态

为了解释和查明N2TEC浮选法的基本原理，本文报道了在用戊基钾黄药(PAX)作捕收剂时，黄铁矿的低电位疏水状态的研究成果。新制定的N2TEC浮选法的目的是提高难处理含金硫化矿金回收率。在典型的N2TEC浮选法中，用氮气代替空气作为浮选气体，戊基钾黄药作为评选含金黄铁矿颗粒的捕收剂。l997年3月，第一个N2TEC浮选工艺在内华达州Lone Tree矿山浮选厂投产，一直操作至今。根据电化学校制接触角测量结果，研究了黄铁矿的低电位、低pH疏水状态与浮选变量(pH、气相组成、捕收剂浓度和黄铁矿电位)之间的关系。     

Minimierung der Umbauzeiten bei Stahlwerksmodernisierungen am Beispiel eines Stranggießanlagen-Umbaues

In November 2000 the Belgian stainless steel producer UGINE & ALZ Belgium nv, a company of the Arcelor Group, awarded VAI a contract for the upgrading and expansion of their steelmaking plant. The overall project included the revamping and supply of new equipment and systems for the steelmaking, continuous casting and environmental protection facilities. An essential part of this ambitious modernization program was the upgrading and expansion of the existing single-strand slab caster, with an output of 600 000 t/a, to a combined single- or twin-strand slab caster with a nominal production capacity of 1.2 million tons — the world’s largest stainless steel slab caster. All upgrading and installation activities had to be carried out within an extremely tight caster shut-down period of 21 days only in order to minimize production losses. This paper discusses the innovative project management solutions implemented in combination with extensive preassembly activities and workshop testing to assure the successful outcome of this project.     

The Effects of Isolation and Acid Mine Drainage on Fish and Macroinvertebrate Communities of Monday Creek, Ohio, USA

Isolated headwater streams in mined watersheds may have good water quality and fish habitat, yet be disconnected from immigration sources by stream segments impaired by acid mine drainage (AMD). Studies of fish and macroinvertebrate communities, habitat, and a number of hydrochemical parameters in Monday Creek, Ohio, show that AMD eliminates fish communities and severely limits macroinvertebrate communities in directly affected tributaries. Isolated headwaters in the heavily mined Monday Creek watershed have relatively good water quality and habitat, but poor fish communities. Comparison of isolated Monday Creek headwaters with non-isolated reaches in unmined watersheds indicates that differences in fish communities are attributable to isolation. Fish communities in isolated headwaters have lower Indices of Biotic Integrity (IBI) than comparable non-isolated communities, reduced species numbers, and lower numbers of individuals, despite suitable habitat as measured by the Qualitative Habitat Evaluation Index (QHEI). Comparison of macroinvertebrate communities shows higher Invertebrate Community Indices (ICI), and no apparent species loss, which can be attributed to the obligate flight stage in the life cycle of many macroinvertebrates, which enables them to overcome aquatic barriers. The implication of this research is that there is an opportunity for recovery of depleted fish communities in large AMD-isolated areas with good water quality, suitable habitat, and intact macroinvertebrate communities, by downstream treatment or source control of AMD to create aquatic corridors for fish immigration.     

'EUROPART'. Airborne particles in the indoor environment. A European interdisciplinary review of scientific evidence on associations between exposure to particles in buildings and health effects

The relevance of particle mass, surface area or number concentration as risk indicators for health effects in non-industrial buildings has been assessed by a European interdisciplinary group of researchers (called EUROPART) by reviewing papers identified in Medline, Toxline, and OSH. Studies dealing with dermal effects or cancer or specifically addressing environmental tobacco smoke, house dust-mite, cockroach or animal allergens, microorganisms and pesticides were excluded. A total of 70 papers were reviewed, and eight were identified for the final review: Five experimental studies involving mainly healthy subjects, two cross-sectional office studies and one longitudinal study among elderly on cardiovascular effects. From most studies, no definite conclusions could be drawn. Overall, the group concluded that there is inadequate scientific evidence that airborne, indoor particulate mass or number concentrations can be used as generally applicable risk indicators of health effects in non-industrial buildings and consequently that there is inadequate scientific evidence for establishing limit values or guidelines for particulate mass or number concentrations.     

Characterization of particulate emissions from occupant activities in offices

This paper characterizes the relationship between occupant activities and indoor air particulate levels in a non-smoking office building. Occupant activities were recorded on video. Particulate concentrations were monitored by three optical particle counters (OPCs) in five size ranges at three heights. Particulate mass concentrations were measured gravimetrically and bioaerosol concentrations were determined by impaction methods. Occupant activities and number concentrations were determined with 1-min resolution over a 1-week period. Occupant activities such as walking past or visiting the monitoring site explained 24-55% of the variation of 1- to 25-micron diameter particle number concentrations. Statistical models associating particulate concentrations with occupant activities depended on the size fraction and included an autocorrelative term. Occupant activities are estimated to contribute up to 10 micrograms m-3 in particulate concentrations per person. Number concentrations of particles smaller than 1 micron had little correlation with indoor activities other than cigarette smoking and were highly correlated with outdoor levels. The method can be used to characterize emissions from activities if rapid measurements can be made and if activities can be coded from the video record.     

Uptake of cadmium, zinc, copper, lead and chromium in the pacific oyster. Crassostrea gigas. Grown in the tamar river. Tasmania

Hundreds of oysters and mud samples from 15 sites along the Tamar River were analysed for cadmium, copper, zinc, lead and chromium. The widely accepted concept of enrichment factors of up to several hundred thousand, describing accumulation by oysters of cadmium, zinc and copper from seawater has been found to be grossly misleading. Concentrations found for these three metals in oysters were only 10–40 times the concentrations in inhabited muds. Concentrations of metals in muds may be used to indicate whether a potential oyster bed would produce oysters that were grossly contaminated. Approximately 1 ppm cadmium in mud could result in oysters containing at least 25 ppm, i.e. 4–5 ppm wet wt. Similarly. 100 ppm zinc in mud could produce oysters containing at least 4000 ppm. i.e. 800–1000 ppm wet wt. Three heavy metal accumulation processes were discernible. Copper and chromium appeared to be absorbed up to a maximum weight that was limited by the size of the oyster and was independent of the amount of metal in the mud. Lead was not absorbed through any physiological demand, but was randomly incorporated at sites containing high concentrations in the mud. Zinc and cadmium were accumulated by a process that depended primarily on the concentrations of these metals in the mud at each site. Mean dry wt concentrations of metals in oysters and mud samples ranged from: 4.2–134 ppm and 0·4 to 5·7 ppm cadmium; 200–1700 ppm and 3–224 ppm copper: 0 135 ppm and 4–1500 ppm lead: 1–37 ppm and 2–88 ppm chromium; 1700 14.000 ppm and 20–500 ppm zinc. respectively.     

Treatment of gas-phase methanol in conventional biofilters packed with lava rock

The performance of laboratory scale methanol-degrading biofilters packed with lava rock was checked during almost 1 yr under different conditions. The biomass concentration and biomass adaptation of the inoculum dramatically affected the start-up and the performance of the systems during the first stages of operation. A fast start-up was obtained when using concentrated and adapted inocula, while diluted or non-adapted inocula proved to be much less efficient. The performance of the reactor during long-term operation was significantly affected by the toxic load and moisture content of the gas. Critical loads between 120 and 280 g/m(3)h were reached during different phases of the study. The reactor had a high stability to EBRT changes when working at values between 48.0 and 91.1s, showing little or no negative effect when decreasing the EBRT. Hardly any difference was observed regarding performance when using either a downflow or upflow feed, although slightly better results were obtained when working in a downflow mode.