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991.
对吸附管离线采样法及高锰酸钾溶液吸收法两种固定源大气汞排放监测方法进行了比较研究。结果表明:由于有更严谨周密的采样过程及质量保证/质量控制过程,吸附管离线采样法监测精度高于高锰酸钾溶液吸收法。吸附管离线采样法在含汞废气低浓度情况下其相对标准偏差为7.88%,而高浓度条件下监测精度明显下降。高锰酸钾溶液吸收法在采样方法上存在一些缺陷,未来该国标方法应重点在采样环节进行修订完善,并亟待建立适合于高浓度固定源含汞废气监测的高锰酸钾溶液吸收法。 相似文献
992.
利用网格采样法比较潮间带沉积物不同粒度区域重金属含量特征 总被引:5,自引:1,他引:4
采用网格采样法,在渤海湾潮间带泥质区、泥沙过渡区和粉沙区分别以10 m和1 m为间隔,采集了384个表层沉积物样品,对Al、Fe、Ti、Mn、Ba、Sr、Zn、Cr、Ni、Cu 10种重金属含量特征进行研究,对比了潮间带不同粒度沉积物中重金属的蓄积特征.结果表明,10种重金属在淤泥、泥沙混合、粉沙3种研究区的总含量分别为147.37、98.68和94.27 g·kg-1,粒度变化造成重金属含量的显著分异;除Ba、Sr倾向在富含长石的粗颗粒区富集外,多数重金属元素呈现细颗粒区富集倾向;Sr含量受粒度变化影响最大,而Cr、Ti含量受粒度变化影响相对较小. 相似文献
993.
使用多介质模型建模方法,构建了针对疏水性液体物质的顶空被动加标系统的动力学模型,以浮萍生长抑制试验系统和鱼类胚胎毒性试验系统为例,得出了3种不同性质的疏水性液体物质正壬烷、十甲基环五硅氧烷(D5)和邻苯二甲酸(2-乙基己基)酯(DEHP)在顶空被动加标系统中的浓度变化,并使用实测浓度对模型进行验证.结果表明,正壬烷和D5在两类系统中平衡24h后,水中浓度便已达到完全平衡时浓度的80%以上,而DEHP的平衡时间很长,不适合使用顶空被动加标系统开展试验,原因是DEHP的挥发性极低.实测浓度和模型预测结果偏差较小.敏感性分析表明,试验系统参数中容器直径对待测物质在水中浓度影响较大,因此可通过调整容器直径来缩短平衡时间,或提高平衡后化学物质在水中的浓度.使用所构建的模型可确定试验系统平衡时间、水中待测物质浓度和待测物质添加体积是否满足试验需求,并可通过敏感性分析来优化试验系统参数,提升试验效率和质量.以上结果完善了顶空被动加标系统应用的理论基础. 相似文献
994.
Kloot RW 《Journal of environmental management》2007,83(4):402-408
One of the problems associated with the use of ambient water quality standards in surface water regulation is the difficulty of identifying and regulating nonpoint source pollution, making such standards unenforceable, especially at the local level. We used the Escherichia coli indicator to locate the most contaminated reaches in rural South Carolina's Bush River watershed (297 km(2), 186 stream-km). We divided the watershed into 20 smaller reaches and sampled each reach multiple times, but restricted each sampling round to one day. We located four low order creek reaches, representing just nine stream-km, where we observed geometric mean E. coli densities of over 1250 E. coli/100 mL; in each case, the source of the contamination (riparian grazing of cattle) was easily identifiable. On the Bush River itself, we observed a step change in one reach where geometric means increased from 106 E. coli/100 mL to 565 E. coli/100 mL over the reach's 10 km length. In this case, the sources of contamination were not as obvious as in the lower order streams; in this case, more advanced Microbial Source Tracking techniques will be required to identify the sources. Nevertheless, this sampling protocol helped locate polluted reaches and provided decision-makers with reasonable justifications for concrete action in deciding where (or where not) to install conservation practices and where more sophisticated (and expensive) MST techniques were warranted. 相似文献
995.
Morville S Scheyer A Mirabel P Millet M 《Environmental science and pollution research international》2006,13(2):83-89
Goal, Scope and Background Atmospheric sampling (gas and particles) of 5 phenols (phenol, m-cresol, p-cresol, o-cresol, pentachlorophenol) and 15 nitrophenols
(3-methyl-2-nitrophenol, 3-nitrophenol, 4-methyl-2-nitrophenol, 5-methyl-2-nitrophenol, 2-methyl-3nitrophenol, 3-methyl-4-nitrophenol,
2,6-dinitrophenol, bromoxynil, 2,5-dinitrophenol, 2,6-dinitro-p-cresol, 2,4-dinitrophenol, ioxynil, DNOC, 3,4-dinitrophenol,
dinoseb) on XAD-2 resin (20 gr) and glass fibre filters, respectively, were performed in 2002 by using 'Digitel DA80' high
volume samplers. These measurements were undertaken in order to show spatial and geographical variations of concentrations
and the role of traffic in the emissions of these compounds to the atmosphere.
Methods Sampling were performed in Strasbourg (eastern France), in its vicinity (Schiltigheim) and in Erstein. Sites were chosen
to be representative of urban (Strasbourg), suburban (Schiltigheim) and rural (Erstein) conditions. Field campaigns were undertaken
simultaneously in urban and suburban sites during all the seasons during 4 hours at a flow rate of 60 m3.h-1, which gives
a total of 240 m3 of air per sample. Period of sampling varied between 06h00 to 10h00, 11h00 to 15h00 and 18h00 to 22h00 in
order to evaluate a variation of concentration during automobile traffic between urban, suburban and rural areas. Gas and
particle samples were separately Soxhlet extracted for 12 h with a mixture of CH2Cl2 / n-hexane (50:50 v/v), concentrated
to about 1 mL with a rotary evaporated and finally dried under nitrogen. Dry extracts were dissolved in 1 mL of CH3CN. Before
analysis, extracts were sylilated by using MTBSTFA. Analysis was performed by GC/MSD in the SIM mode.
Results and Discussion Partitioning of phenolic compounds between gas and particle phases seems to be mainly correlated with vapour pressure. Among
phenolic compounds analysed, phenol, p-cresol, pentachlorophenol and 2.4-dinitrophenol were detected in all samples and emissions
from traffic seems to be the major source for the presence of these compounds to the atmosphere. No increase of concentrations
in autumn tend to confirm this hypothesis since, with the use of domestic heating in colder months, increases of PAHs concentrations
were observed and these compounds are known to be emitted by all combustion processes.
Pentachlorophenol is a special case since this molecule is only used as wood preservative. Its presence in all atmospheric
samples, whatever the locations and the period of time is the consequence of its persistence.
Conclusions and Perspectives These measurements demonstrate that phenols and nitrophenols are emitted to the atmosphere and further measurements, in order
to confirm their sources, their behaviour and their potential impact to the air quality and to human health should be undertaken
especially since the literature collected is relatively old. Concentrations of pentachlorophenol measured are very low and,
due to its toxicity, further investigations should be undertaken.
- * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August
to 1 September 2004, Bordeaux, France. 相似文献
996.
In settings where measurements are costly and/or difficult to obtain but ranking of the potential sample data is relatively easy and reliable, the use of statistical methods based on a ranked-set sampling approach can lead to substantial improvement over analogous methods associated with simple random samples. Previous nonparametric work in this area has been concentrated almost exclusively on the one- and two-sample location problems. In this paper we develop ranked-set sample procedures for the m-sample location setting where the treatment effect parameters follow a restricted umbrella pattern. Distribution-free testing procedures are developed for both the case where the peak of the umbrella is known and for the case where it is unknown. Small sample and asymptotic null distribution properties are provided for the peak-known test statistic. 相似文献
997.
998.
一种基于Logistic回归的全损飞行事故分析与预测 总被引:3,自引:0,他引:3
运用Logistic回归方法分析全损飞行事故的影响因素,并构建预测模型,然后利用飞行事故案例进行了实证检验。通过对样本数据过离散、空单元、多元共线性和特异值、特殊影响案例的诊断,以及对模型的拟合程度和预测效果的检验,表明所构建的模型比较符合现实情况,而且具有较好的拟合程度和预测效果。模型指出航班类型和机龄因素具有统计学意义,国内航班比国际航班的全损概率要高;机龄越老,全损概率越高。 相似文献
999.
Stream macroinvertebrate communities vary naturally among types of habitats where they are sampled, which affects the results of environmental assessment. We analyzed macroinvertebrates collected from riffle and snag habitats to evaluate influences of habitat-specific sampling on taxon occurrence, assemblage measures, and biotic indices. We found considerably more macroinvertebrate taxa unique to snags (143 taxa) than to riffles (75 taxa), and the numbers of taxa found in both riffles and snags (149 taxa) were similar to that found in snags. About 64% of the 47 macroinvertebrate measures we tested differed significantly between riffles and snags. Eighty percent intercepts of regressions between biotic indices and urban or agricultural land uses differed significantly between riffles and snags. The Hilsenhoff biotic index calculated from snag samples explained 69% of the variance of riffle samples and classified 66% of the sites into the same stream health group as the riffle samples. However, four multimetric indices for snag samples explained less than 50% of the variance of riffle samples and classified less than 50% of the sites into the same health group as the riffle samples. We concluded that macroinvertebrate indices developed for riffle/run habitat should not be used for snag samples to assess stream impairment. We recommend developing an index of biotic integrity specifically for snags and using snags as an alternate sampling substrate for streams that naturally lack riffles. 相似文献
1000.
Patchy Distribution Fields: Sampling Distance Unit of an Interleaved Survey and Reconstruction Adequacy 总被引:1,自引:1,他引:0
Kalikhman I 《Environmental monitoring and assessment》2006,118(1-3):147-163
A mathematical model was used to examine the effects of choosing various units of sampling distance of an interleaved (two-pass)
acoustic survey on the adequacy of reconstructing patchy distribution fields. The model simulates fish or plankton patches
(or gaps) of different shapes and spatial orientations, and an interleaved survey by parallel or zigzag transects, along which
a unit of sampling distance is set. The efficiency of a survey is determined by the adequacy of a reconstructed field to that
originally generated, which is evaluated by calculating their correlations (r). Regarding immovable fields, the experiments conducted indicate that a patchy field can be reconstructed properly (r
2 > 0.70) if the distance between transects D < (1.5–2.0)R and the unit of sampling distance d < (1.5– 2.0)R
p. As, for regular surveys d < (1.0–1.5)R
p, it may be concluded that interleaved surveys are more efficient than regular ones because of the factor studied. In regard
to movable fields, a comparison of the results of interleaved surveys with those of regular surveys directly indicates that
the former may ensure a more adequate field reconstruction than the latter do. This fact confirms the previous conclusion
that an interleaved survey is expedient in cases where there is no preference regarding the position of a vessel for further
work. 相似文献