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61.
Matthaios P. Kavvalakis Manolis N. Tzatzarakis Eleftheria P. Theodoropoulou Emmanouil G. Barbounis Andreas K. Tsakalof Aristidis M. Tsatsakis 《Chemosphere》2013
Imidacloprid (IMI) is a relatively new neuro-active neonicotinoid insecticide and nowadays one of the largest selling insecticides worldwide. In the present study a LC–APCI–MS based method was developed and validated for the quantification of imidacloprid and its main metabolite 6-chloronicotinic acid (6-CINA) in urine and hair specimens. The method was tested in biomonitoring of intentionally exposed animals and subsequently applied for biomonitoring of Cretan urban and rural population. 相似文献
62.
Detecting Temporal Change in Watershed Nutrient Yields 总被引:2,自引:1,他引:1
Meta-analyses reveal that nutrient yields tend to be higher for watersheds dominated by anthropogenic uses (e.g., urban, agriculture) and lower for watersheds dominated by natural vegetation. One implication of this pattern is that loss of natural vegetation will produce increases in watershed nutrient yields. Yet, the same meta-analyses also reveal that, absent land-cover change, watershed nutrient yields vary from one year to the next due to many exogenous factors. The interacting effects of land cover and exogenous factors suggest nutrient yields should be treated as distributions, and the effect of land-cover change should be examined by looking for significant changes in the distributions. We compiled nutrient yield distributions from published data. The published data included watersheds with homogeneous land cover that typically reported two or more years of annual nutrient yields for the same watershed. These data were used to construct statistical models, and the models were used to estimate changes in the nutrient yield distributions as a result of land-cover change. Land-cover changes were derived from the National Land Cover Database (NLCD). Total nitrogen (TN) yield distributions increased significantly for 35 of 1550 watersheds and decreased significantly for 51. Total phosphorus (TP) yield distributions increased significantly for 142 watersheds and decreased significantly for 17. The amount of land-cover change required to produce significant shifts in nutrient yield distributions was not constant. Small land-cover changes led to significant shifts in nutrient yield distributions when watersheds were dominated by natural vegetation, whereas much larger land-cover changes were needed to produce significant shifts when watersheds were dominated by urban or agriculture. We discuss our results in the context of the Clean Water Act. 相似文献
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65.
从仪器精密度、方法检出限、准确度等角度对吹扫捕集浓缩仪Stratum PTC与Eclipse 4660的性能进行比较。结果表明,大部分分析物用Stratum PTC的方法检出限略高于Eclipse 4660,但精密度比Eclipse 4660稍差;Eclipse 4660用于分析极性的、水溶性物质的效果比Stratum PTC好,回收率更高。两种吹扫捕集仪的测试结果均满足《土壤和沉积物挥发性有机物的测定吹扫捕集/气相色谱-质谱法》(HJ 605-2011)标准方法的指标要求。 相似文献
66.
基于PSO-SVM算法的环境监测数据异常检测和缺失补全 总被引:3,自引:0,他引:3
针对环境监测数据异常和数据缺失问题,提出了基于支持向量机的粒子群优化数据异常检测和缺失补全算法。利用粒子群优化算法选取较优的支持向量机训练参数组合,以此建立非线性的支持向量机模型,并利用结果模型对测得的真实数据拟合预测。以宁夏回族自治区某污水处理厂的污染物测量数据作为实验数据,结果表明,利用该算法预测数据的准确率可达97.977%,检测异常数据准确度高,缺失数据补全正确。 相似文献
67.
Malcolm J. R. Clark Paul H. Whitfield 《Journal of the American Water Resources Association》1994,30(6):1063-1079
ABSTRACT: Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left-censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left-censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives. 相似文献
68.
James P. Hughes Steven P. Millard 《Journal of the American Water Resources Association》1988,24(3):521-531
ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied. 相似文献
69.
大空间室内火灾早期自动探测与定位研究 总被引:10,自引:0,他引:10
本文在深入研究早期火灾一般燃烧火焰在彩色影像上所呈现的光谱及运动特性基础上,首次提出利用彩色影像实时探测室内火灾的新方法,通过物方坐标与像方坐标的直接线性变换,实现了早期火灾的自动探测与空间定位,实验证明了该方法的有效性与稳健性,且具有巨大的应用前景。 相似文献
70.
Summary. Detection of heterospecific predators and prey
via chemical cues is well known, but only a few studies have
examined the potential for such discrimination in cannibalistic
systems. In newts, Notophthalmus viridescens, adults are
opportunistic predators of conspecific larvae. I used a laboratory
bioassay to determine whether larvae and adults distinguish
between chemical stimuli from members of the
different age classes. Larvae distinguished between chemical
stimuli from larvae and adults by decreasing their activity
only following exposure to stimuli from adults. Decreased
activity is consistent with an antipredator response in many
prey species, including larval newts. In contrast, adults
increased their activity and increased time spent in open
areas in response to stimuli from larvae, but not to stimuli
from adults. Increased activity is consistent with a feeding
response; adults also showed increased activity and
increased time in open areas in response to chemical stimuli
from familiar heterospecific prey (brine shrimp). The proximate
cue that allowed the newts to distinguish between the
different age classes is not associated with short-term
dietary differences because all stimulus animals were fed the
same prey. Stimulus strength was controlled by diluting the
stimulus solutions according to the volume of the stimulus
animal. Therefore, there appear to be intrinsic differences in
the chemical signatures of larval and adult newts. 相似文献