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1.
V Sanfelix ET Gòmez MM Jordán T Sanfeliu S Pallarés AB Vicente 《Environmental Geology》2005,47(6):811-819
The objective of this work is to assess the concentrations of three factions of air particles (settable particles, TSP and PM10) and the levels of several toxic elements in a clay atomisation industry through aerosol sampling at several points inside an industrial plant. Mechanical activities, which produce diffuse emissions, are the main process of discharge of particles in both indoor and outdoor workplace environments in the atomisation plant. The levels of As, Cd, Pb, Zn, Ba and Ni increase in the zones with higher concentrations of particles and lower ventilation. The concentrations of As and F are not influenced by the recycling processes. The levels of Cd and Pb do not show great enrichment in air particles collected inside the atomisation plant although the content of both elements is associated with ceramic muck recycling. Finally, the content of B in waste water is mainly transferred in gaseous phase to the atmosphere during the process of drying by atomisation. 相似文献
2.
土地利用/土地覆被变化遥感监测研究 总被引：3，自引：0，他引：3
根据1990年和1999年两期TM/ETM 遥感数据,运用遥感分类中的监督分类方法,全面分析乌鲁木齐市的土地利用的数量变化特征和空间变化特征,阐明了区域土地利用变化的区域特点。 相似文献
3.
MM Cruickshank RW TomlinsonD BondPM DevineCJW Edwards 《Applied geography (Sevenoaks, England)》1995,15(4)
Northern Ireland has a tradition of peat cutting; 78 per cent by area of remaining lowland bogs and 46 per cent of blanket bogs have been cut in the past. Since the early 1980s, machine peat extraction for fuel and horticulture has increased, against a background of changing economic support for agriculture, high rural unemployment and agricultural underemployment. Cutting fuel peat can reduce household fuel costs and some peat fuel is sold to gain income. Horticultural peat is cut mainly for sale. Expansion of machine extraction, with possible environmental impacts, occurred as interest in peatland conservation increased. Potential conflict arises between local economic needs and conservation. Machine cutting for fuel is widespread, but affects only 2.6 per cent of the blanket peat area; horticultural extraction is more localized and is only one-fifth of the extent of fuel extraction. Altitude, distance from roads, land ownership and rights, turbary, religious affiliation, local economic needs and the role of government departments all contribute to explaining the distribution and extent of extraction. 相似文献
4.
General circulation models (GCMs), or stand‐alone models that are forced by the output from GCMs, are increasingly being used to simulate the interactions between snow cover, snowmelt, climate and water resources. The variation in snowpack extent, and hence albedo, through time in a cell is likely to be substantial, especially in mid‐latitude mountainous regions. As a consequence, the energy budget simulation by a GCM relies on a realistic representation of snowpack extent. Similarly, from a water resource perspective, the spatial extent of the pack is key in predicting meltwater discharges into rivers. In this paper a simple computationally efficient regional snow model has been developed, which is based on a degree‐day approach and simulates the fraction of the model domain covered by snow, the spatially averaged melt rate and the mean snowpack depth. Computational efficiency is achieved through a novel spatial averaging procedure, which relies on the assumptions that precipitation and temperature scale linearly with elevation and that the distribution of elevations in the domain can be modelled by a continuous function. The resulting spatially averaged model is compared with both observations of the duration of snow cover throughout Austria and with results from a distributed model based on the same underlying assumptions but applied at a fine spatial resolution. The new spatially averaged model successfully simulated the seasonal snow duration observations and reproduced the daily dynamics of snow cover extent, the spatially averaged melt rate and mean pack depth simulated by the distributed model. It, therefore, offers a computationally efficient and easily applied alternative to the current crop of regional snow models. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
5.
Estimating the Peak Indentation Force of the Edge Chipping of Rocks Using Single Point-Attack Pick 总被引：1，自引：0，他引：1
This article establishes a new model for estimating the peak indentation force of the edge chipping of rocks when using a
conical or a pyramidal point-attack pick. The investigation points out that the existing formulation in the literature is
based on an inappropriate stress assumption and equilibrium, and hence leads to incorrect cutting force estimations. The new
model developed in this study is based on an analysis of the penetration force and energy dissipation using fracture mechanics,
similarity of chip geometry, and edge chipping tests on four different rock materials. It is found that the peak indentation
force and the depth of cut follow a power law, that the new model can reasonably estimate the experimental measurements, and
that it provides useful information for the shape optimization of point-attack picks in mechanical excavation. 相似文献
6.
S. H. Ferguson D. Berteaux A. J. Gaston J. W. Higdon N. Lecomte N. Lunn M. L. Mallory J. Reist D. Russell N. G. Yoccoz X. Zhu 《Climatic change》2012,115(1):235-258
Long-term data are critically important to science, management, and policy formation. Here we describe a number of data collections from arctic Canada that monitor vertebrate population trends of freshwater and marine fish, marine birds, marine and terrestrial mammals. These time series data cover the last ca. 30?years and capture a period from the onset of global changes affecting the Arctic up to recent years with a rapid increase in temperature. While many of these data collections were initiated through a variety of government and university programs, they also include a surge in polar research launched with the recent International Polar Year (2007?C2008). We estimated the long-term vertebrate index from our data that summarizes various taxa abundance trends within a global context and observed a continuous decline of about 30?% in population abundance since the 1990s. Though most data collections are biased towards few taxa, we conduct time-series analyses to show that the potential value of long-term data emerges as individual monitoring sites can be spread across space and time scales. Despite covering a handful of populations, the different time series data covered a large spectrum of dynamics, cyclic to non-cyclic, including coherence with the North Atlantic Oscillation, lag effects, and density dependence. We describe a synthesis framework to integrate ecological time-series research and thereby derive additional benefits to management, science, and policy. Future requirements include: (1) continuation of current observation systems; (2) expansion of current monitoring sites to include additional trophic links and taxonomic indicators; (3) expansion beyond the existing program to include greater spatial coverage into less-sampled ecosystems and key representative locations; and (4) integration of circumpolar observations and comprehensive analyses. Development of a circumpolar observation system is necessary for innovative science, large-scale adaptive management, and policy revision essential to respond to rapid global change. 相似文献
7.
This study aimed to establish the effects of waterlogging, salinity and light on the early development of mangroves. Seedlings of Bruguiera gymnorrhiza (L.) Lamk. and Heritiera littoralis Dryand were exposed to 12 weeks of waterlogging, during which time growth and photosynthesis were measured every two weeks. The salinity of the water inundation ranged from fresh water to full-strength sea water (salinity 35). Seedlings were exposed to either full sunlight of 1 500 µmol photon m–2 s–1 (SD 397) at midday or shade conditions of 325 µmol photon m–2 s–1 (SD 40) of light at midday, to explore whether the plants would be differently affected by prolonged waterlogging in increased salinities and under different light conditions. Heritiera littoralis was more sensitive to waterlogging, salinity and light, displaying a least relative growth rate of 0.127 g g–1 week–1 (SE 0.032) under shade, and 0.025 g g–1 week–1 (SE 0.021) in full light; while under shade, photosynthesis continued only in fresh water, but photosynthetic yield decreased from 0.7 to 0.4 with increasing duration of waterlogging. By 12 weeks, all H. littoralis seedlings treated with any saltwater mixture had died. Bruguiera gymnorrhiza seedlings maintained a moderate rate of photosynthesis throughout inundation in both shade and full light, with yields of 0.7 and 0.3, respectively. Furthermore, B. gymnorrhiza survived waterlogging in up to 66% seawater, and maintained comparable relative growth rates of 0.164 g g–1 week–1 (SE 0.066) with 0.083 g g–1 week–1 (SE 0.065) and 0.074 g g–1 week–1 (SE 0.036) with 0.052 g g–1 week–1 (SE 0.037) under shade and in full light between fresh water and the highest salinity conditions, respectively. These results suggest that B. gymnorrhiza is broadly tolerant, making it a potential candidate species for restoring vulnerable mangrove forests. 相似文献
8.
塔里木二叠纪基性-中性-酸性岩浆岩的年代学及其地质意义 总被引：13，自引：9，他引：4
塔里木西部柯坪地区出露的早二叠纪玄武岩与盆地内其他地区广泛分布的玄武岩共同构成一个面积约0.25Mkm2的溢流玄武岩省。巴楚地区出露的早二叠纪辉绿岩、正长岩、石英正长岩与石英正长斑岩等多种岩浆岩构成了连续的基性-中性-酸性岩浆序列。野外露头观察表明,巴楚麻扎尔塔格地区的基性-中性-酸性岩浆岩为近同时侵位。柯坪塔格开派兹雷克组顶部层位玄武岩的锆石SHRIMP U-Pb年龄为279.0±4.5Ma, 该年龄值可限定该区二叠纪溢流玄武岩喷发的最晚时限。巴楚麻扎尔塔格石英正长斑岩脉的锆石SHRIMP U-Pb年龄为273.0±3.7Ma, 与前人测定的巴楚辉绿岩脉和正长岩的锆石年龄在误差范围内一致,表明巴楚地区的基性-中性-酸性岩浆岩为近同时侵位,时间在275Ma左右。综合已发表的塔里木二叠纪岩浆岩高精度年代数据,本文提出：整个塔里木大火成岩省岩浆作用的持续时间约为20Myrs; 291~287Ma喷发的巨量溢流玄武岩可能构成塔里木大火成岩省的主体,是地幔柱头部熔融的直接产物; 283~272Ma侵位的巴楚、一间房和塔北地区的其它类型岩浆岩体积较小,为塔里木大火成岩省晚期岩浆作用的产物。 相似文献
9.
Analytic solutions play an important role in the testing of models evaluated by numerical methods. This paper presents a straight forward method for determining analytic solutions to multiple species contaminant transport problems in porous media. The method uses Fourier sine transforms (as opposed to Laplace transforms) to obtain the solution of Cho (1970, Can. J. Soil. Sci., 51: 339–350) in a simpler way. It provides a flexible approach to the introduction of new boundary and initial conditions within the model. New solutions are presented for constant and exponential initial contaminant profiles. 相似文献
10.