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361.
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363.
通过试验,讨论盐析效应、顶空的平衡温度和平衡时间、水样的p H值、色谱条件等对顶空-气相色谱法测定环境水体中吡啶准确度的影响。优化上述条件后,方法在0 mg/L~3.95 mg/L范围内线性良好,检出限可达0.016 mg/L,测定下限为0.064 mg/L。用该方法对地表水和生活污水做3个质量浓度水平的加标回收试验,测定6次结果的RSD为1.7%~5.7%,回收率为93.9%~113%。 相似文献
364.
利用简单、方便、不用电源的被动采样技术分别对川南地区6市区域范围内空气中SO2和NO2在雨季和旱季的空间分布特征进行研究。按16 km×16 km的均匀网格布设点位162个,并在雨季于6市各选1个空气自动站布设城区点位采集空气中SO2和NO2。获得的样品经0.3%的双氧水浸提后采用离子色谱法进行分析,经换算后获得空气中SO2和NO2的浓度,了解了其含量水平,绘制了SO2和NO2的空间分布图,掌握了其空间分布特征,并对可能的来源进行了浅析。将被动采样监测结果与自动站监测结果进行相关分析,两者高度线性相关,NO2和SO2线性相关系数分别为0.901 3和0.874 5,均大于r0.05(4)=0.811 4。 相似文献
365.
环境空气中VOCs的自动监测数据是研究重污染天气成因的一个重要依据。低温空管冷冻浓缩技术-GC-MSFID法,可用于环境空气中多组分VOCs复杂样品的自动监测,性能优于吸附管浓缩法。低温空管冷冻浓缩技术的采样流量、采样时间、冷冻温度等条件对环境空气中VOCs的测定有很大影响。实验结果表明:高采样流量低采样时间条件下,低沸点卤代烃捕集效率偏低;低采样流量长采样时间,-120℃捕集温度可满足各类VOCs的测试。降低采样流量增加采样时间,沸点较高的各类VOCs的捕集效率比较高。相同捕集温度下,降低采样体积,各类VOCs的响应同步降低,可用于高浓度C_5~C_(12)碳氢化合物、卤代烃和醛酮含氧化合物样品的测定。 相似文献
366.
For intersexual selection to occur, it is necessary that females choose between males. It is now well appreciated that constraints
exist, which preclude females sampling all the available males in a population. These constraints are likely to have caused
the evolution of sampling rules (such as the “best-of-n” rule) by which females sample males. Here we investigate the impact of female subsampling of the male population, not on
the evolution of sampling behaviour, but on the population-level correlation between a male trait and currencies such as reproductive
success. This study is important as it illustrates when population-level correlations can be safely used to infer the presence
and strength of sexual selection in the field. We find that the correlation between a male trait and a mate choice variable
rises steeply as the number of males sampled by each female increases, flattening above seven to ten males sampled. This shape
is found to be remarkably robust, and little affected by, for example, the mate choice variable used, by noise in assessment,
by sampling behaviour depending on female quality, or by population size. The only variable found to have a large impact is
male clumping according to their “quality”. If females are sampling about four males, the maximum correlation that can be
found at the population level is in the range 0.4–0.6, perhaps as little as 0.1 if males are strongly clumped. A recent review
of the literature suggests that four is the average number of males that females sample. Thus, the absence of a strong correlation
cannot by itself be used to infer that sexual selection is weak, as it may be due to females sampling few males.
Received: 18 May 1998 / Accepted after revision: 18 July 1998 相似文献
367.
The use of replicated plot,line and point sampling for estimating species abundance and ecological diversity 总被引:1,自引:0,他引:1
The paper deals with the problem of estimating diversity indexes for an ecological community. First the species abundances are unbiasedly and consistently estimated using designs based on n random and independent selections of plots, points or lines over the study area. The problem of sampling elusive populations is also considered. Finally, the diversity index estimates are obtained as functions of the abundance estimates. The resulting estimators turn out to be asymptotically (n large) unbiased, even if a considerable bias may occur for a small n. Accordingly, the method of jackknifing is made use of in order to reduce bias. 相似文献
368.
大气中痕量持久性有机污染物年均值的测定 总被引:7,自引:1,他引:6
采用以XAD-2树脂为吸附介质的大气被动采样器,在四川卧龙自然保护区设置6个采样点,进行了为期2年(2005年-2007年)的环境大气样品采集。用气相色谱-高分辨质谱方法对HCB,HCHs,DDTs和PCBs测定。结果表明,平行样品的重现性良好,平均相对偏差为9%。POPs检测下限的范围为1.0pg/m^3-5.9pg/m^3。2年的年均值数据表现出较好的一致性和规律性。以XAD-2树脂为吸附介质的大气被动采样器能够便利地采集进而测定半年或一年污染物的平均浓度,可以经济、有效地获得大气中痕量POPs的年均值。ρ(α—HCH)/ρ(γ-HCH)从成都到卧龙的上升的趋势反映的是传输过程中HCH的降解;而卧龙地区跨年度数据所反映出的ρ(α—HCH)/ρ(γ-HCH)下降趋势,可以归因于林丹的使用。 相似文献
369.
370.
Low-density polyethylene (LDPE) has been widely used as a sorbent for passive sampling of hydrophobic organic contaminants (HOCs) in aquatic environments. However, it has seen only limited application in passive sampling for measurement of freely dissolved concentrations of parent and substituted PAHs (SPAHs), which are known to be toxic, mutagenic and carcinogenic. Here, the 16 priority PAHs and some typical PAHs were selected as target compounds and were simultaneously determined by gas chromatography–mass spectrometer (GC–MS). Some batch experiments were conducted in the laboratory to explore the adsorption kinetics of the target compounds in LDPE membranes. The results showed that both PAHs and SPAHs could reach equilibrium status within 19–38?days in sorption kinetic experiments. The coefficients of partitioning between LDPE film (50?μm thickness) and water (KLDPE) for the 16 priority PAHs were in good agreement with previously reported values, and the values of KLDPE for the 9 SPAHs are reported in this study for the first time. Significant linear relationships were observed, i.e., log KLDPE?=?0.705?×?log KOW?+?1.534 for PAHs (R2?=?0.8361, p?<?0.001) and log KLDPE?=?0.458?×?log KOW?+?3.092 for SPAHs (R2?=?0.5609, p?=?0.0077). The selected LDPE film was also proven to meet the condition of “zero sink” for the selected target compounds. These results could provide basic support for the configuration and in situ application of passive samplers. 相似文献