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近20年来,对气挟微生物的研究,无论在环境保护以及劳动卫生方面均已引起人们的广泛重视。在研究方法上,经典的自然落下法已多不采用;液体冲击法虽较科学但操作繁琐;而固体撞击法与滤膜法则较简便,唯前者需特殊采样器,后者仅需气泵及微孔滤膜即可,故简易可行。滤膜法已列为水中大肠菌类监测的 相似文献
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586.
一把套筒扳子从高空坠落,会产生怎样的后果?你想象得到吗?报刊上曾经刊载过下面一个故事。 1980年9月18日傍晚7点多钟,离美国阿肯色州马斯克斯镇6公里远的小山上的一个导弹发射井里,维修人员正在对一枚大力神Ⅱ式洲际导弹进行保养作业。这枚导弹的头部装着一颗威力为1,000万吨梯恩梯当量的氢弹头。这时,从距离发射井底21.3米高的工作平台上传来了一声惊叫,原来有个技师不小心将一把1.35公斤重的套筒扳子掉了下去。他紧张地盯着这只扳子,只见它在发射井底部反弹起来,猛地撞击在导弹第一级燃料贮箱的铝合金外壳上。外壳裂开了,液体燃料散发出… 相似文献
587.
Particulate emissions from construction activities 总被引:1,自引:0,他引:1
Muleski GE Cowherd C Kinsey JS 《Journal of the Air & Waste Management Association (1995)》2005,55(6):772-783
Although it has long been recognized that road and building construction activity constitutes an important source of particulate matter (PM) emissions throughout the United States, until recently only limited research has been directed to its characterization. This paper presents the results of PM10 and PM2.5 (particles < or = 10 microm and < or = 2.5 microm in aerodynamic diameter, respectively) emission factor development from the onsite testing of component operations at actual construction sites during the period 1998-2001. Much of the testing effort was directed at earthmoving operations with scrapers, because earthmoving is the most important contributor of PM emissions across the construction industry. Other sources tested were truck loading and dumping of crushed rock and mud and dirt carryout from construction site access points onto adjacent public paved roads. Also tested were the effects of watering for control of scraper travel routes and the use of paved and graveled aprons at construction site access points for reducing mud and dirt carryout. The PM10 emissions from earthmoving were found to be up to an order of magnitude greater than predicted by AP-42 emission factors drawn from other industries. As expected, the observed PM2.5:PM10 emission factor ratios reflected the relative importance of the vehicle exhaust and the resuspended dust components of each type of construction activity. An unexpected finding was that PM2.5 emissions from mud and dirt carryout were much less than anticipated. Finally, the control efficiency of watering of scraper travel routes was found to closely follow a bilinear moisture model. 相似文献
588.
In order to estimate the fluxes of Ra isotopes, we measured 224Ra, 226Ra, and 228Ra activities in the Ulsan Bay mixing zone. The convex upwards curvature of the plot of Ra isotope activities versus salinity for the mixing zone suggests that Ra isotopes are supplied from particles entering the mixing zone from both the river and bottom sediments. This addition increases the estuarine flux of 226Ra and 228Ra to the outer sea by factors of 15 and 95 over the flux attributable to Ra dissolved in the riverine water alone. In order to estimate the residence time of the water in Ulsan Bay, we applied a mass balance model to the distribution of 224Ra and 226Ra activities in the Ulsan Bay mixing zone with the inflow from the Taehwa River. The obtained residence times of the waters in the Ulsan Bay were estimated to be 6.8-11.4 d. The waters in the upper part of the estuary have long residence times whereas those in the lower part, in contact with the open sea, have shorter residence times. The mean residence time of the water in the Ulsan Bay was estimated to be 9.1 d. 相似文献
589.
Utilization of magnetic and electrostatic separation in the recycling of printed circuit boards scrap 总被引:13,自引:0,他引:13
Veit HM Diehl TR Salami AP Rodrigues JS Bernardes AM Tenório JA 《Waste management (New York, N.Y.)》2005,25(1):67-74
The progress of the technology is directly related to the growth of production and consumption of electrical/electronics equipment, especially of personal computers. This type of equipment has a relatively short average lifetime, 2-3 years. The amount of defective or obsolete equipment has been increasing substantially; consequently its disposition and/or recycling should be studied. In this work, printed circuit boards, which are used in personal computers, were studied in order to recover the metals in the circuit boards through mechanical processing, such as crushing, screening, as well as magnetic and electrostatic separation. The results obtained demonstrate the feasibility of using these processes to separate metal fractions from polymers and ceramics, and that it is possible to obtain a fraction concentrated in metals containing more than 50% on average of copper, 24% of tin and 8% of lead. 相似文献
590.
张溱芳 《环境与可持续发展》1986,(5)
从六十年代末期开始,各国烟气脱硫方面的开发工作集中在为新建厂寻找高脱除率(70~90%)的工艺上,新选择的技术有烟气洗涤法以及后来发展的喷雾干燥法等.然 相似文献