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排序方式: 共有337条查询结果,搜索用时 15 毫秒
181.
介绍了自制的标准呼吸性粉尘发生装置制备含石英呼吸性粉尘滤膜样品的实验方法。经测试表明:该方法操作简便,制备的呼吸性粉尘样品石英含量均匀,样品质量可控制,粉尘粒度分布和现场样品一致,适用于实验室间或不同方法之间的石英含量比较性研究和质量控制。 相似文献
182.
Time-series studies published since 1993 on the association between short-term changes in air quality and use of hospital services, including both inpatient and emergency room use, are reviewed. The use of nonparametric analysis, often incorporating generalized additive models (GAMs), has increased greatly since the early 1990s. There have also been three major multi-city studies, which together analyzed data from well over 100 cities in Europe and North America. Various air pollutants, especially ozone (O(3)), particulate matter (PM), nitrogen dioxide (NO(2)) and sulfur dioxide (SO(2)), were generally found to be significantly associated with increased use of hospital services. Ozone tends to have stronger effects in the summer during periods of higher concentrations. Several studies revealed synergistic effects between pollutants such as PM and SO(2). Overall, short-term exposure to air pollutants is found to be an important predictor of increased hospital and emergency room use around the world. 相似文献
183.
184.
我国大气颗粒物来源及特征分析 总被引:23,自引:0,他引:23
我国大气颗粒物来源复杂,呈现大气复合型污染特征,对主要污染源进行识别和定量,是制定城市空气质量改善措施的基础。本研究总结了2000年以来我国近30个城市大气可吸入颗粒物PM10源解析研究,结果表明我国大气颗粒物PM10主要来自六类源:扬尘(土壤尘、道路尘、建筑尘);燃煤;工业排放;机动车排放;生物质燃烧;SO2、NOx、VOCs氧化产生的二次颗粒物。研究还表明,不同地区不同季节大气颗粒物主要来源和相对贡献存在差异。近年来随着大气颗粒物控制措施的实施,城市PM10污染状况已明显改善,大气细颗粒物PM2.5越来越受关注,在制定空气质量达标方案时,各类燃烧源和二次颗粒物的重要性将进一步上升。 相似文献
185.
Particulate matter diameter ≤ 2.5 μm (PM2.5) causes direct harm to human health. Finding forms of urban forest systems that with the ability to reduce the amount of particulate matter in air effectively is the aim of this study. Five commonly cultivated kinds of urban forest types were studied in Beijing city at three stages of leaf growth. Results show that the urban forest system is capable of storing and capturing dust from the air. The types of shrubs and broadleaf trees that have the ability to capture PM2.5 from the air are most effective when leaves have fully developed. In the leafless season, the conifer and mixed tree types are the most effective in removing dust from the air. For all kinds of forest types and stages of leaf growth, the PM2.5 concentration is highest in the morning but lower in the afternoon and evening. Grassland cannot control particles suspended in the air, but can reduce dust pollution caused by dust from the ground blown by the wind back into the air. 相似文献
186.
Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%–83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level. 相似文献
187.
To increase the knowledge on the particulate matter of a wetland in Beijing, an experimental study on the concentration and composition of PM10 and PM2.5 was implemented in Beijing Olympic Forest Park from 2013 to 2014. This study analyzed the meteorological factors and deposition fluxes at different heights and in different periods in the wetlands. The results showed that the mean mass concentrations of PM10 and PM2.5 were the highest at 06:00–09:00 and the lowest at 15:00–18:00. And the annual concentration of PM10 and PM2.5 in the wetland followed the order of dry period (winter) > normal water period (spring and autumn) > wet period (summer), with the concentration in the dry period significantly higher than that in the normal water and wet periods. The chemical composition of PM2.5 in the wetlands included NH4+, K+, Na+, Mg2 +, SO42 −, NO3−, and Cl−, which respectively accounted for 12.7%, 1.0%, 0.8%, 0.7%, 46.6%, 33.2%, and 5.1% of the average annual composition. The concentration of PM10 and PM2.5 in the wetlands had a significant positive correlation with relative humidity, a negative correlation with wind speed, and an insignificant negative correlation with temperature and radiation. The daily average dry deposition amount of PM10 in the different periods followed the order of dry period > normal water period > wet period, and the daily average dry deposition amount of PM2.5 in the different periods was dry period > wet period > normal water period. 相似文献
188.
将振荡天平技术与国内污染源废气监测方法标准相结合,建立了废气中颗粒物现场测定方法--便携式振荡天平法。新建方法以重量法为原理,检出限为0.2 mg/m 3,全程伴热以消除湿度干扰,测试前后以标准滤膜量值验证的方式对称量结果进行质量保证,实现了固定污染源废气中颗粒物的快速、准确的测量。方法建立后与国标法《固定污染源废气低浓度颗粒物的测定重量法》(HJ 836—2017)进行实际样品测定比对,结果表明,2种方法无显著性差异。新建方法提高了工作效率,减少了过程误差。 相似文献
189.
卡尔曼滤波器是现代控制理论中的一种最优理论,其目的是从大量偶然干扰中筛取主导因素,以对事物变化规律作出正确的估计。介绍了卡尔曼滤波器的基本思路及原理,以及在安全工程中使用卡尔曼滤波器时应注意的问题。 相似文献
190.
气体生物滴滤池载体性能比较实验研究 总被引:16,自引:2,他引:14
通过动态条件挂膜和静态降解曲线比较对丝网、ACOF、聚乙烯多面小球、炉渣等介质作为气体生物滴滤池生物载体材料的性能进行了研究.实验结果表明,4种材料都可用作生物载体材料,各材料的挂膜量比为:丝网vACOFv多面小球v炉渣= 7.14v9.52v2.05v1,半降解时间比大致为:丝网vACOFv多面小球v炉渣= 0.43v0.5v0.7v1,网状结构的丝网和ACOF挂膜量大、降解效果好,比表面积大的多面小球次之,炉渣最差.实验还表明:4种挂膜载体在闲置一段时间后,具一定吸附性能的ACOF的降解性能缓冲、恢复效果最佳,短时间的闲置(如24h)对挂膜载体降解性能损害不明显 相似文献