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291.
A number of methods has been proposed for dealing with single-factor or factorial experiments when the requirements for performing the normal theory analysis of variance procedure are not satisfied. This paper suggests the use of the likelihood ratio statistic for testing the main effects and the interaction between the factors in two-way layout of count data following negative binomial distributions with a common dispersion parameter. The likelihood ratio statistic for testing the equality of the dispersion parameters of several groups of count data is also derived. The methods is illustrated by an example concerning the study of spatial and temporal variation of bacterial counts. 相似文献
292.
Byron A. Bodo 《Environmental monitoring and assessment》1989,13(2-3):407-428
Graphical methods can play an important role in the reliable assessment of trends in typically ill behaved river quality data series both as diagnostic tools and as visual corroborative evidence when assumptions required for formal statistical tests are not met. Robust, graphically-oriented trend diagnosis procedures are presented for data series characterized by nonnormal populations, uneven time spacing, nonmonotonic trend and other factors which can create serious problems for standard parametric time series methods. Cleveland's robust locally weighted regression (RLWR) developed for investigating nonlinearity in x-y scatterplots is adapted as a robust/resistant smoothing filter for the analysis of irregular time series comprising quantitative observations. Low powered RLWR trend lines reveal temporally local phenomena, e.g. abrupt jumps (often associated with point source impacts) and periodicities, while higher powered RLWR yields smooth lines characterizing medium and longer term trends. Simple variants of Tukey smoothing concepts are developed for series with censored observations. Applications to Ontario river quality series reveal that graphical evidence is frequently sufficient to obviate the need for formal trend testing. The methods are generally applicable to most time series. 相似文献
293.
Rey C. Stendell David S. Gilmer Nancy A. Coon Douglas M. Swineford 《Environmental monitoring and assessment》1988,10(1):37-41
Residues of organochlorine pesticides, polychlorinated biphenyls (PCBs), and mercury were measured in eggs of Swainson's hawks (Buteo swainsoni) and ferruginous hawks (B. regalis) collected in North and South Dakota during 1974–79. DDE was the most common compound detected in the eggs, but residues were below levels known to have adverse effects on reproduction. Other organochlorine compounds and mercury were found at low levels. Eggs of ferruginous hawks tended to contain more compounds with higher residues than eggs of Swainson's hawks. 相似文献
294.
R. Harkov A. Greenberg F. Darack L. Mcgeorge C. Pietarinen 《Environmental monitoring and assessment》1987,9(1):83-92
Quality assurance (QA) assessments of air pollution data sets provide a basis for evaluating the significance of various substances in the atmosphere. For non-criteria pollutants, QA results are seldom reported in the technical literature and are often difficult to estimate. The present report provides a summary of QA results such as recovery, precision and accuracy data. Of the six trace elements and nine organic constituents compared in detail, recoveries, laboratory precision and laboratory accuracy values were 100%, ±3% to ±19% and-2 to-13% for the former group and 69% to 98%, ±7% to 23% and-15 to-34% for the later group. System precision varied from ±22% to ±47% for the trace elements and ±42% to ±83% for the organic constituents. Limitations in the interpretation of non-criteria particulate-phase pollutant data bases are discussed with some emphasis placed on receptor-modelling and risk assessment applications. Finally, the relevance of NBS certified materials for QA estimates in non-criteria air pollutant studies is also reviewed. 相似文献
295.
A. Leonard M. Duverger-Van Bogaert A. Bernard M. Lambotte-Vandepaer R. Lauwerys 《Environmental monitoring and assessment》1985,5(4):369-384
The short-term tests performed in vitro on different systems, from phage to human cells, or in vivo, on laboratory animals, allow only a qualitative estimate of the action of mutagenic agents, and the extrapolation of such experimental results to man may encounter many difficulties.Direct biomonitoring of populations exposed to chemicals could represent a more realistic approach for an evaluation of the hazards to man. Certain methods are still under development. Nevertheless, other ones can already by used routinely, e.g. the cytogenetic observations on peripheral blood lymphocytes and the Ames test for mutagenic substances in urine, and can provide useful suggestions how to set threshold limits for chemical substances encountered in the working environment. 相似文献
296.
In many situations, the effect of a toxic chemical on a biological system depends on both the intensity and the duration of exposure. The dependence on the time dimension can be the expression of a range of processes including the physical accumulation of toxic chemicals or their metabolites and the functional accumulation of damage. Measures and functions that have been used to describe this dependence are reviewed.Some of these functions are compared through a case study of the neurotoxicity of methylmercury. Use is made of data that indicates a dependency between the blood concentration at which monkeys were exposed and the length of time before damage was detected. Several exposure functions are fitted to these data and their appropriateness is compared. Using the most appropriate function, an exposure-response relationship is developed using probit analysis. An alternative data analysis procedure is also investigated. The apparent threshold after a 100 day exposure is estimated to be greater by a factor of 3–5 compared to the threshold for chronic exposure. Applying this factor to man, the blood concentration threshold for chronic exposure is estimated to be 40–170 ppb, a finding consistent with recent reports of neurological damage in humans exposed below the generally accepted threshold. 相似文献
297.
Strontium-90 (90SR) released to the ground near the N Reactor at the U.S. Department of Energy's Hanford Site enters the Columbia River through shoreline seeps. The 90Sr is then potentially available for uptake by plants and animals. The life history and foraging behavior of nesting Canada geese is such that female geese could ingest 90Sr while foraging on shoreline plants. Radichemical analyses showed that goose eggshells taken from an island, downstream from the N Reactor, contained more 90Sr than did eggshells collected from other downstream islands. Reed canary grass samples taken from shoreline areas immediately downstream from the N Reactor contained higher concentrations of 90Sr than samples from other downstream areas. All goose eggshells did not contain enhanced levels of 90Sr, and all reed canary grass samples did not contain enhanced levels of 90Sr, but a relationship exists between the releases of 90Sr to the Columbia River and the enhanced levels of 90Sr in some of the environmental samples analyzed.Pacific Northwest Laboratory is operated by Battelle Memorial Institute for the U.S. Department of Energy under contract DE-ACO6-76RLO 1830. 相似文献
298.
Sun HF Takata A Hata N Kasahara I Taguchi S 《Journal of environmental monitoring : JEM》2003,5(6):891-895
The degradation, sorption, transportation and material balance of cationic surfactants discharged from domestic waste into river water was studied. Ion-pair solid-phase extraction behavior showed that the sorption of cationic surfactants as an ion-pair with anionic surfactant onto river sediment was so strong that little cationic surfactant was found in the bulk water. Cationic surfactant was found in river sediment at more than 500 times higher concentration than that in the bulk water. The degradation of the cationic surfactant was very slow in river water and much slower in the sediment. A material balance of cationic surfactant was estimated for a river running through Toyama City by measuring the flow rate and the concentration of cationic surfactant in the water at several points. It was found that more than 30% of cationic surfactant introduced to the river was lost during the river running through ca. 3 km in 3 h. This reduction probably comes from a quick transfer of the cationic surfactant from river water to sediment and water weed by means of adsorption or precipitation with suspending solids. 相似文献
299.
Morgenstern P Versteegh AF de Korte GA Hoogerbrugge R Mooibroek D Bannink A Hogendoorn EA 《Journal of environmental monitoring : JEM》2003,5(6):885-890
An indicative survey has been carried out in The Netherlands investigating the presence of methyl tertiary butyl ether (MTBE) in drinking water and the corresponding sources. In total, 71 different sites used for the preparation of drinking water in The Netherlands were sampled in two successive seasons in 2001 involving the analysis of 156 samples. (ground water (n = 88), surface water (n = 17), bank filtrate water (n = 6) and drinking water (n = 45)). To combine high sample throughput with high selectivity and sensitivity, off-line purge and trap for sampling and gas chromatography mass spectrometry equipped with an automated thermal desorption sampler (TDS-GC-MS) was selected as the preferred analytical methodology. The developed procedure enabled the analysis of at least 40 samples per day and provided a limit of quantification of 2 ng l(-1). In the first period 63 samples of raw water were analyzed. Concentrations ranged between < 10 ng l(-1) and 420 ng l(-1) with a median concentration below 10 ng l(-1). The second period was focused at the re-sampling of positive locations (MTBE > 10 ng l(-1)) and a few additional drinking water utilities of which both the raw and drinking water of the utilities were analyzed. The median concentration of MTBE in the selected set of drinking water samples was 20 ng l(-1) (n = 45). At one location MTBE was found at a level of 2900 ng l(-1) caused by point source contamination of the ground water (11 900 ng l(-1)). Special attention has been paid to the quality of the results by analyzing all samples in duplicate and the analysis of control samples during each series of analyses. 相似文献
300.
Sandanger TM Brustad M Odland JO Doudarev AA Miretsky GI Chaschin V Burkow IC Lund E 《Journal of environmental monitoring : JEM》2003,5(4):689-696
Some of the people living in the Chukotka Peninsula of Russia depend heavily on marine mammals, but little is known of the exact dietary patterns and plasma levels of POPs among these populations. In this study, POPs levels in plasma from 50 participants from the isolated community of Uelen (Bering Strait) were determined and related to dietary information obtained through a food frequency questionnaire. The intake of marine mammals was high and the combined intake of blubber from walrus, seal and whale was a significant predictor (p < 0.01) of plasma concentrations of sum PCBs and borderline for sum CDs (p = 0.02) and sum DDTs (p = 0.04). There was a significant gender difference in the levels of POPs, and among women there was a significant increase with age. Extensive breastfeeding and lower blubber intake among women could be possible explanations for this gender difference. Despite the high intake of blubber the plasma levels of PCBs and DDTs were lower than some of those reported for the East Coast of Greenland. The geometric mean values for sum PCBs (17 congeners) and sum DDTs were 1316 ng g(-1) lipids and 563 ng g(-1) lipids, respectively. PCB 163, which partly co-eluted with PCB 138, was found in high concentrations (40% of PCB 138). This raises questions regarding the validity of using PCB 138 and PCB 153 to calculate the level of Arochlor 1260. The geometric mean of sum CDs was 518 ng g(-1) lipids. Concentrations of beta-HCH (geometric mean; 410 ng g(-1) lipids) were higher than observed for other native populations depending on marine mammals. Transportation of beta-HCH by ocean currents through the Bering Strait into the Arctic Ocean or regional point sources might explain these elevated levels. 相似文献