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301.
302.
Sensitive diffusive samplers for concentration measurements in ambient airhave been used successfully in Sweden for several years. The samplers have theadvantage of being stable at room temperature before, as well as after,sampling, easy to handle, and cost-efficient. Furthermore, they do not requireelectricity or field calibration. In order to test their use in tropical andsubtropical environments and to obtain a preliminary set of data to validateatmospheric chemistry transport models in this part of the world, duplicatesamples were collected at 11 sites every second month during one year. Eightof the sites were background sites in Asia. It was not possible within theproject to compare the measured concentrations with other measurementtechniques. However, the reproducibility of the duplicates was satisfactoryover the whole measuring range (almost three orders of magnitude of theconcentration for SO2) and reasonable agreement with modelcalculations was obtained at least for SO2 andNH3. Further testing of the measuring technique in tropicalareas is, however, warranted. 相似文献
303.
Wet deposition of ammonium in Europe 总被引:2,自引:0,他引:2
Ammonium concentration data in precipitation have been compiled to derive a concentration and deposition field for ammonium in Europe. Measurements referring to a total number of 218 measuring sites have been considered. Because of changes in the ammonium concentrations due to the use of improper sampling procedures, a correction procedure is proposed. This makes allowance for the type of sampler used, the length of the sampling period, and whether or not light-protected sample bottles are used. Dependent on the specific sampling procedure used correction factors range from 0.75 to 1.20. According to our calculations, the total wet deposition flux of ammonium in Europe in the early 1980s amounts to 2.4 Mt NH4
+y-1. However, for some parts of Europe the flux cannot be estimated very reliably because of the low number or even the absence of measuring sites. Compared to earlier estimates for around 1960, the ammonium wet deposition flux has increased by approximately 25% during the period 1960–1980. 相似文献
304.
Thirty-six aerosol filter samples collected in tropospheric Arctic haze layers, in the stratosphere, and in the marine boundary layer during the 1983 Arctic Gas and Aerosol Sampling Program were analyzed for trace elements using instrumental neutron activation analysis. Average crustal dust concentrations were 540 ng/m3 and 330 ng/m3 for samples collected in Arctic haze over the North American and Norwegian Arctic, respectively. An average marine salt concentration of 120 ng/m3 was obtained for haze samples collected above the marine boundary layer on both sides of the Arctic.Meteorological and wind trajectory information were used to identify specific haze transport pathways, which brought relatively unmixed aerosol from the central Soviet Union into the AGASP sampling areas. Results from individual filters collected within these transport zones are discussed, with emphasis on certain trace metal ratos which have been proposed by other researchers as discriminators of aerosols from different source regions. Our aircraft-collected data are compared with previously-collected ground-based measurements, and show reasonably good agreement for most tracer elements and ratios. Specifically, we have determined the As/Sb ratio tracer, named by other researchers as the most effective elemental discriminator of aerosol from the central Soviet Union, to be approximately 5–6. This relatively high tracer value is consistent with previous ground-based findings. A significantly lower V/Sb ratio was observed throughout this study, possibly indicating a change in the source signature. 相似文献
305.
Peter Haase Susanne Lohse Steffen Pauls Karin Schindehütte Andrea Sundermann Peter Rolauffs Daniel Hering 《Limnologica》2004,34(4):349-365
In the past, no single standardised method for sampling and sorting benthic macroinvertebrates has been implemented in Germany. Therefore, we tested the suitability of two common sorting protocols, RIVPACS and AQEM/STAR, by taking samples with each protocol at 44 sampling sites. Our results reveal that different methods deliver slightly different assessment results. Moreover these two methods differ in costs. Although the AQEM/STAR protocol takes longer than the RIVPACS protocol, we favoured the AQEM/STAR protocol because of its higher level of standardisation. In order to limit costs to an acceptable level, a modification of the AQEM/STAR protocol (MAS method) is developed. This method is highly standardised, gives stable assessment results and is relatively inexpensive (€ 224.00 for processing of an average sample). A detailed protocol of the newly developed method is given. 相似文献
306.
报道了以NH4H2PO4为基体改进剂,采用悬浮体制样石墨炉原子吸收光谱法直接测定琥珀中微量铅的方法。试验了影响测定的主要因素。在优化实验条件下。方法的检出限为0.038μg/g,Pb的质量浓度为0~80μg/L时,工作曲线线性关系良好。对于ω(Pb)=5.71μg/g样品的测定,相对标准偏差(RSD,n=5)为6.83%。 相似文献
307.
The introduced collecting method is based on a common entomologist exhauster, which is specified for the fieldwork in aquatic systems with a sieve-inset and a bottom-lid. The living organisms are collected visually from the sampled debris and no further extraction is needed. The apparatus is designed for qualitative sampling of microcrustaceans (e.g. Cladocera, Copepoda, Ostracoda) and minimises disturbance at the sampling site. 相似文献
308.
关于岩土样本统计分析的几点讨论 总被引:1,自引:0,他引:1
结合岩土单元体的天然成因及人为设定的基本特性,阐述了岩土样本离散的必然性及其离散程度与岩土单元体分划范围的相关性,通过对变异系数的适用性及岩土样本概况性的分析,提出采用均同指数评价样本分布的离散程度和按相对容量标准控制岩土样本数量等观点,建议切实针对岩土母体的分布形态推断标准值,同时对小样本条件下标准值的确定方式进行了分析和建议。 相似文献
309.
310.
随着GIS用户对地理信息可视化性能要求的不断提高,虚拟地理场景的景物实体建模方法成为VRGIS领域的热点问题之一。本文探讨了一种基于立体视觉的影像多视点建模方法,包括景物实体表面影像纹理的采集和重建。影像纹理采集方面,提出了根据景物实体形状和景物实体表面纹理分布特点分配采集点的纹理采集方法。影像纹理重建方面,根据多幅影像对应特征点创建采样点模型,最后与几何模型进行空间配准,创建景物实体模型。以一实例进行实验论证,实验结果表明,该建模方法能够有效的提高虚拟地理环境中模型的真实感。 相似文献