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201.
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232名微机操作人员的慢性肌肉骨骼损伤表现为肩、颈、下背的酸痛和肩疲劳,与对照组比差异显著。手、腕及上肢的慢性损伤虽较对照组高,但无统计学意义。这与他们的击键次数相对较少(每日10000次左右),但需长期间保持低头及向前弯腰的坐位姿势及工作台面太高等因素有关 相似文献
203.
Summary Pesticide residues in soil, water, food, wildlife and other media have been analysed in several monitoring studies. The purpose was to establish the distribution of these residues across a defined area, ascertain their trend over a specific period and use the results to assess environmental compliance and safety. In the present review the availability of information on pesticide residues in various Canadian environmental components was sought. With the possible exception of localized pesticide contamination of some private water supply wells, ground and surface water, most analyses revealed concentrations below guideline limits. Only a few cases were reported of mishandling, misuse and poisoning from pesticides. Continuing surveillance programmes and in-depth and well-organized monitoring studies, with special focus on areas that are vulnerable to contamination, by both provincial and federal governments, are largely responsible for the encouraging results. This experience in the control of pesticide use and monitoring of residues in the environment should be of particular interest in developing countries.Dr A.Y. Sangodoyin is a senior lecturer in the Department of Agricultural Engineering at the University of Ibadan. He was recently involved in a study visit to the University of Alberta, Edmonton, Alberta, Canada T6G 2G7, where his co-author Dr D.W. Smith is a member of staff in the Department of Civil-Engineering. 相似文献
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Jonn A. Foulk Wayne Y. Chao Danny E. Akin Roy B. Dodd Patricia A. Layton 《Journal of Polymers and the Environment》2004,12(3):165-171
Municipal solid wastes generated each year contain potentially useful and recyclable materials for composites. Simultaneously, interest is high for the use of natural fibers, such as flax (Linum usitatissimum L.), in composites thus providing cost and environmental benefits. To investigate the utility of these materials, composites containing flax fibers with recycled high density polyethylene (HDPE) were created and compared with similar products made with wood pulp, glass, and carbon fibers. Flax was either enzyme- or dew-retted to observe composite property differences between diverse levels of enzyme formulations and retting techniques. Coupling agents would strengthen binding between fibers and HDPE but in this study fibers were not modified in anyway to observe mechanical property differences between natural fiber composites. Composites with flax fibers from various retting methods, i.e., dew- vs. enzyme-retting, behaved differently; dew-retted fiber composites resulted in both lower strength and percent elongation. The lowest level of enzyme-retting and the most economical process produces composites that do not appear to differ from the highest level of enzyme-retting. Flax fibers improved the modulus of elasticity over wood pulp and HDPE alone and were less dense than glass or carbon fiber composites. Likely, differences in surface properties of the various flax fibers, while poorly defined and requiring further research, caused various interactions with the resin that influenced composite properties. 相似文献
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B. Y. Aminuddin M. H. Ghulam W. Y. Wan Abdullah M. Zulkefli R. B. Salama 《Water, Air, & Soil Pollution: Focus》2005,5(1-2):89-101
Cameron Highlands is a mountainous region with steep slopes. Gradients exceeding 20∘ are common. The climate is favourable to the cultivation of tea, sub-tropical vegetables and flowers (under rain-shelter).
Crop production is sustained by high fertiliser and manure applications. However, agriculture in this environment is characterised
by high levels of soil erosion and environmental pollution. A study on the sustainability of these agro-ecosystems was conducted.
Results indicated that soil loss was in the range of 24–42 ton/ha/yr under vegetables and 1.3 ton under rain-shelter. Sediment
load in the vegetable sub-catchment reached 3.5 g/L, 50 times higher than that associated with flowers under rain-shelter
and tea. The sediments contained high nutrient loads of up to 470 kg N/ha/yr. The N, P and K lost in runoff from cabbage farms
was 154 kg/season/ha, whereas in chrysanthemum farms it was 5 kg. In cabbage farms, the N, P, and K lost through leaching
was 193 kg/season/ha. The NO3–N concentration in the runoff from the cabbage farms reached 25 ppm but less than 10 ppm in runoff from rain-shelters. Inorganic
pollution in the rivers was within the acceptable limit of 10 ppm. The sustainability of the agro-ecosystems is in the order
of tea { > } rain–shelter ≫ vegetables. 相似文献
209.
Ian D. Leith Lucy J. Sheppard David Fowler J. Neil Cape Matt Jones Alan Crossley Ken J. Hargreaves Y. Sim Tang Mark Theobald Mark R. Sutton 《Water, Air, & Soil Pollution: Focus》2005,4(6):207-218
Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH3 inputs to moorland vegetation growing on a bog at a field scale, a field release NH3 fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH3 from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s?1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH3 concentration with distance from the source. In a complementary study, using a NH3 flux chamber system, the relationships between NH3 concentrations and cuticular resistances were quantified for a range of NH3 concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH3 concentration from 11 s m?1 at 3.0 μg m?3 to 30 s m?1 at 30 μg m?3. The NH3 concentration data and the concentration-dependent canopy resistance are used to calculate NH3 deposition taking into account leaf surface wetness. The implications of using an NH3 concentration-dependent cuticular resistance and the importance for refining critical loads are discussed. 相似文献
210.