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41.
42.
GIS in the K-12 Curriculum: A Cautionary Note   总被引:7,自引:0,他引:7  
Two qualitative case studies, one focusing on K-12 teachers and the other on middle school students, explore key factors associated with using Geographic Information Systems in the classroom. In both studies, access to appropriate hardware is a critical barrier. Time is another critical barrier—time to learn the GIS software and time in the curriculum to incorporate GIS as a learning experience. In both case studies, learning the technology at the expense of learning spatial analysis was a danger, suggesting the need for conscious focus on the goal of using GIS to learn how to “do geography.”  相似文献   
43.
This study evaluates the possibility of determining bed material transport using the virtual rate of travel of individual particles, dimensions of the active layer of the streambed, and porosity and density of streambed material. Magnetically tagged stones and scour indicators were employed in Carnation Creek, British Columbia, to quantify transport rates. Observations cover flows up to 36 m3 s−1 (τ* = 0·081). Transport rates, ranging from 0·090 to 9·7 kg s−1 (0·12–13·2 m3 h−1), display a relatively sensitive trend with maximum stream power, as expected. Error analysis indicates that uncertainty in virtual velocity covers the majority of sample variance. An evaluation of the two measurement techniques used to delineate active layer dimensions, magnetically tagged stones and scour indicators, indicates that they yield comparable depths, widths and transport rates over the range of flows observed. Issues for further study are discussed. © 1998 John Wiley & Sons, Ltd.  相似文献   
44.
Rhenium–osmium geochronometry for samples with low Re and complex matrices requires improved Re extraction methods. Here, we investigate plausible controls on efficiency and efficacy of Re extraction during our anion resin bead purification. Four different protocols are compared, each isolating a single variable to test. Rhenium concentrations for solutions at each step of each protocol document differences in chemical recovery/yield. The negative‐thermal ionisation mass spectrometry (N‐TIMS) signal intensity serves as a proxy for Re yield and purity. These data document correlations between the N‐TIMS signal intensity and (a) the duration of anion resin bead conditioning prior to loading with Re‐bearing solution, and (b) both duration and strength of nitric acid used during rinsing of the Re‐loaded anion resin bead. The optimal protocol improved Re signal intensity around fourteen times compared with our current Re extraction protocol, an aggregate of 2.4 times improvement in chemical recovery (yield) and 5.8 times improvement in emission efficiency (purity). Repeated N‐TIMS isotopic measurements on our in‐house Re standard solution (1407) verify that our optimal protocol‐3 does not fractionate Re isotopes. The improved anion resin bead method considerably lowers the Re detection limit and allows Re‐Os isotopic analysis of picogram‐level Re hosted in geological samples with complex matrices.  相似文献   
45.
The vast majority of microorganisms in aquifers live as biofilms on sediment surfaces, which presents significant challenges for sampling as only the suspended microbes will be sampled through normal pumping. The use of a down-well low frequency sonicator has been suggested as a method of detaching microbes from the biofilm and allowing rapid sampling of this community. We developed a portable, easy to use, low-frequency electric sonicator and evaluated its performance for a range of well depths (tested up to 42 m below ground level) and casing types. Three sonicators were characterized in laboratory experiments using a 1 m long tank filled with pea gravel. These included a commercially available pneumatic sonicator, a rotating flexible shaft sonicator, and the prototype electric sonicator. The electric sonicator detached between 56 and 74% of microbes grown on gravel-containing biobags at distances ranging between 2 and 50 cm from the sonicator. The field testing comprises of a total of 55 sampling events from 48 wells located in 4 regions throughout New Zealand. Pre- and post-sonication samples showed an average 33 times increase in bacterial counts. Microbial sequence data showed that the same classes are present in pre- and post-sonicated samples and only slight differences were seen in the proportions present. The sampling process was rapid and the significant increases in bacterial counts mean that microbial samples can be quickly obtained from wells, which permits more detailed analysis than previously possible.  相似文献   
46.
Hurricane Sandy was an extraordinarily large storm that affected most of the eastern coast of the USA in October 2012. To assess this storm’s impact, the benthic invertebrate community structure and sediment properties were compared in samples collected 3.5 months prior to (July 2012) and 8 months after (July 2013) the hurricane at 97 locations in Barnegat Bay, New Jersey, USA. Barnegat Bay is a shallow back-barrier estuary just north of where Sandy made landfall. For all locations taken together, sediment total nitrogen concentration was lower afterwards, while total organic carbon and total phosphorus concentrations were similar. Sediment median particle size was the same before and after, but the sediment was better sorted after the storm. There were no differences in total abundance of invertebrates, species richness, species diversity, or the abundance of polychaetes, bivalves, or gastropods. Malacostracan crustaceans were more abundant after Sandy (average 82 (0.04 m2)?1) than they were before (average 64), due almost entirely to increased abundance of ampeliscid amphipods, which showed a shift toward smaller sizes in 2013. Annelids in the order Clitellata were on average less abundant after the hurricane (17) than before (53). The apparent minimal effect of Sandy on the benthic community in Barnegat Bay was probably because the passage of the hurricane had no detectable effects on salinity or dissolved oxygen concentrations throughout the bay.  相似文献   
47.
This paper describes the in situ response of groundwater biofilms in an alluvial gravel aquifer system on the Canterbury Plains, New Zealand. Biofilms were developed on aquifer gravel, encased in fine mesh bags and suspended in protective columns in monitoring wells for at least 20 weeks. Four sites were selected in the same groundwater system where previous analyses indicated a gradient of increasing nitrate down the hydraulic gradient from Sites 1 to 4. Measurements during the current study classified the groundwater as oligotrophic. Biofilm responses to the nutrient gradients were assessed using bioassays, with biomass determined using protein and cellular and nucleic acid staining and biofilm activity using enzyme assays for lipid, carbohydrate, phosphate metabolism, and cell viability. In general, biofilm activity decreased as nitrate levels increased from Sites 1 to 4, with the opposite relationship for carbon and phosphorus concentrations. These results showed that the groundwater system supported biofilm growth and that the upper catchment supported efficient and productive biofilms (high ratio of activity per unit biomass).  相似文献   
48.
In order to study the pollution gradient in the vicinity of a large aluminium production facility in Patagonia (Argentina), a passive biomonitoring was performed employing foliage from three tree species. Primary scope was to identify pollution gradients and to select suitable tree species which can be used as biomonitor plants in the study area. Therefore, leaves of Eucalyptus rostrata, Populus hybridus and different needle ages of Pinus radiata were collected at different distances from the industry and the fluoride concentration was analysed in washed and unwashed samples in order to determine the amount of external fluoride. Washing reduced the F‐concentrations by 24, 39 and 51% on average in E. rostrata, P. hybridus and P. radiata, respectively, indicating that species‐specific characteristics determine the accumulation and wash‐off of dust‐associated fluorine. F‐concentrations varied from 6 to 3652 ppm F in unwashed samples indicating a steep pollution gradient in the study area. The influence of F‐emissions was discernible in all samples up to a distance of 3500 m from the smelter. E. rostrata accumulated more fluorine than the other species at equal distance from the emission source. The present study confirms that aluminium smelting results in high F deposition in the study area. Establishing a biomonitor network around large emitters is suitable and feasible to evaluate the efficiency of air control measures.  相似文献   
49.
This article aims to generate insights into both private governance and partnerships within the shipping industry, but also tries to improve understanding of the complex process of institutionalisation.This is achieved through a case study of the Clean Shipping Project, a public/private partnership that aims to promote sustainability in the shipping industry. A set of enabling and constraining factors are examined that shape the institutionalisation process and determine to what extent the Clean Shipping Project can establish and expand authority as an industry norm.Overall, the Clean Shipping Project cannot yet be considered a full-fledged private governance institution, because of an insufficient level of collaborative advantage mainly due to weak system robustness and unfavourable market characteristics and conditions. However, institutionalisation is an ongoing process and the future outlook for the Clean Shipping Project remains promising. The Clean Shipping Project is certainly a relevant supplement to existing regulations and there is a basic level of commitment and cohesion within the partnership, so it is not unlikely that in the future this initiative may help to uncouple growth in shipping activities from environmental harm.  相似文献   
50.
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