共查询到20条相似文献,搜索用时 62 毫秒
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梳理了国内外河岸缓冲带划定文献,系统探讨了河岸缓冲带划定的重要影响因素。结果表明:(1)河岸缓冲带划定方法主要有经验值法、简单数学模型法、复杂机理模型法、基于地理信息系统的数学模型法等,不同划定方法适宜的流域自然地理条件、精准性各异,有各自的优缺点和适用范围。(2)河岸缓冲带净化河流水质、固岸防洪、调节流域微气候、保护生物多样性、为河流生态系统提供养分和能量等生态水文功能是河岸缓冲带划定的重要参考依据。(3)流域空间尺度越大,所需的河岸缓冲带越宽;流域空间尺度不同,其河岸缓冲带划定的适宜方法往往也不同。 相似文献
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3种草皮缓冲带对农田径流污染物的净化效果及其最佳宽度研究 总被引:15,自引:0,他引:15
通过对照试验,研究了百慕大、白花三叶草和高羊茅3种草皮缓冲带对农田径流污染物的净化效果.结果表明,空白对照带对径流水SS几乎没有去除效果,百慕大草皮缓冲带对径流水SS的去除率最高,达84%.其次为白花三叶草和高羊茅草皮缓冲带,对径流水SS的去除率分别为81%、73%;进水TN质量浓度在10 mg/L以内时,3种草皮缓冲带出水TN质量浓度都低于2mg/L,均达到<地表水环境质量标准>(GB 3838-2002)V类标准;进水TP质量浓度为0.54~1.50 mg/L时,3种草皮缓冲带出水TP质量浓度均为0.08~0.34 mg/L,也均低于GB 3838-2002V类标准规定的限值;3种草皮缓冲带径流水SS去除率和沿程距离具有显著的相关性,在径流水SS去除率为80%时.通过计算可知3种草皮缓冲带的最佳宽度为16.1~20.4 m.其中百慕大草皮缓冲带最低,为16.1 m. 相似文献
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不同草皮构建的湖泊缓冲带对污染物的净化效果研究 总被引:2,自引:0,他引:2
选择宜兴地区常见的3种草皮百慕大(Cynodon dactylon)、白花三叶草(Trifolium repens)、高羊茅(Festuca arundinacea),利用自行设计的实验装置模拟构建草皮缓冲带,并模拟宜兴地区降雨时产生的汇流过程和雨量进行太湖缓冲带对陆域面源污染物的净化效果研究.结果表明,草皮缓冲带能有效地截留径流中的SS,3种草皮缓冲带的径流对SS的去除率为百慕大缓冲带>三叶草缓冲带>高羊茅缓冲带>空白对照(不种植草皮的空白土壤),且沿程去除效果增强;草皮缓冲带的渗流对TN、NH3-N、TP净化效果均显著(p<0.05)高于径流;3种草皮缓冲带在试验槽前0.9m处的污染物去除效果最为明显,湖泊缓冲带的宽度与其污染物截留效果呈正比;总体来说,草皮生物量与其构建的湖泊缓冲带的污染物去除率呈正相关,三叶草和百慕大有较大的地上生物量,其构建的缓冲带表现出较高的污染物去除率,而高羊茅的地上生物量相对较小,其构建的缓冲带污染物去除率也相对较低. 相似文献
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将富营养水体治理与硬质河岸改造相结合,能够提高水体与河岸的交互能力,恢复河流生态系统的自净能力.以位于四川省天府新区眉山片区中心城区的柴桑河河段(长度1.5km,宽度80~100m,水深约1.85m)为例,通过铺设护岸专用基料、设置滴灌系统和播撒花草种子对硬质河岸进行生态重建,通过向水体中施用除磷剂、微生物菌剂及采用生态浮床、水车增氧等措施,降低了水体中的氮磷含量,利用太阳能为整个处理系统供能,实现了硬质河岸和富营养水体的综合治理.项目实施后,通过半年的监测和观察,结果表明:柴桑河水体中总磷(TP)、氨氮(NH3-N)、高锰酸盐指数(CODMn)和总氮(TN)含量明显降低,TP和NH3-N由劣V类提升至地表水Ⅲ类,CODMn由劣V类提升至地表水Ⅳ类,TN由劣V类提升至地表水V类;河道内鱼类、藻类、水草的多样性增加,硬质河岸完全被植被覆盖,植物种类达数十种,自然景观恢复,河流生态自净功能显著增强,有利于使水体保持健康稳定. 相似文献
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Alfred Eisner Jacob Tadmor 《Journal of the Air & Waste Management Association (1995)》2013,63(4):400-401
A number of key projects in the Environmental Protection Agency (EPA) particulate R&;D program having applicability to industry are presented. For electrostatic precipitators (ESP) there is presented the result of work on large diameter discharge electrodes which provide a decrease in penetration of up to a factor of 4 when compared to conventional small diameter electrodes. Also discussed is the multistage ESP which provides a collection efficiency that would require a collecting plate area 4 or 5 times larger with conventional ESP technology. The E-SOX technology makes use of the multistage concept to free up space in the ESP for SO2 removals of up to 90%. Electrostatically augmented fabric filtration provides a reduction in pressure drop of about 5 0% as compared to conventional fabric filtration. Wind tunnel modeling of windbreaks for material storage piles indicates a potential for providing engineering design data that would allow significant emission reduction caused by wind erosion 相似文献
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《国际环境与污染杂志》2011,10(2):304-314
This paper investigates some of the reflectivity characteristics that clouds (when modelled as solid bodies) must exhibit to be compatible with observations that the reflecting surface of a cloud (i) appears almost equally bright across its face, (ii) is brightest when the cloud is opposite to the Sun but decreases in brightness as the cloud moves to other positions and (iii) increases in brightness with increasing optical thickness of the cloud in the observer's line of sight. These observations, respectively, are shown to imply that the peak value of the bidirectional total reflectivity from a cloud surface (i) increases in inverse proportion to the cosine of the angle between the Sun and the normal to the cloud surface, as the incident angle increases, (ii) appears to be directed back in the direction of the incident radiation, and (iii) increases as optical thickness of the cloud in the observer's line of sight increases. The results could have application in many fields (e.g. modelling diffuse radiance distributions for cloudy skies). 相似文献
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Janusz A. Pudykiewicz Anna S. Koziol 《Atmospheric environment (Oxford, England : 1994)》1998,32(24):5541
The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing. 相似文献
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Árpád Ambrus 《Journal of environmental science and health. Part. B》2013,48(3):435-442
Abstract A computer model was used to take random samples from primary sample populations obtained from field trials to simulate the uncertainty of sampling for residue analysis of plant commodities and soil. The results indicate about 40%, 30% and 20% relative uncertainty when random samples of size 5, 10 and 25 are taken respectively, from a single lot. Therefore the sample size should be the same for establishing and enforcing legal limits. 相似文献
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结合扬中生态环境的基本情况和存在的不足,进行了具体分析,对扬中未来生态建设的发展方向提出了建议及实施措施。 相似文献
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在实施ISO/IEC17025:1999标准《检测和校准实验室能力的通用要求》过程中,通过实验室质量管理体系内部审核的实践与系统分析,识别出内部审核实施阶段的关键环节,提出召开首次会议、收集审核证据、确定审核发现和召开末次会议的技术方法,对提高内部审核的质量和有效性、获得可靠的审核结论具有重要意义。 相似文献
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介绍了电解法生产次氯酸钠的原理 ,并在原有生产工艺的基础上进行了重新设计和对设备的重新选择、改造 ,得出了各个工艺参数的最佳值 ,生产出高品质的次氯酸钠 相似文献
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考察了不同有机改性硅对微囊藻毒素LR(mLR)和LA(mLA)的等温吸附行为。结果表明,有机改性硅可有效吸附去除水体中<0.1×10-6(质量分数)的微囊藻毒素,并且吸附去除效果随表面改性官能团中碳原子数量的增加而增加;相同条件下,有机改性硅在微囊藻毒素异构体之间存在着一定的吸附选择性。 相似文献
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以松木木屑为原料,在自制的小型流化床上,开展了生物质热裂解温度、生物质粒径和进料速率对生物油产率的影响实验研究.结果表明,在热裂解温度分别为450、475、500、525和550℃条件下,当热裂解温度为500℃时,生物油产率最高,平均产率达到53.33%(质量百分比).反应温度越高,炭产量越低,不可冷凝气体产量越高,气体发热值越高;粒径<1 mm的生物质其粒径对生物油产率影响不大;生物质进料速率增加时,生物油产率增加.本研究为生物能的利用提供了新的途径. 相似文献