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71.
72.
MARTIN A. STAPANIAN STEVEN P. CLINE DAVID L. CASSELL 《Environmental monitoring and assessment》1997,45(3):237-257
We evaluate a field method for determining species richness andcanopy cover of vascular plants for the Forest Health MonitoringProgram (FHM), an ecological survey of U.S. forests. Measurementsare taken within 12 1-m2 quadrats on 1/15 ha plots in FHM.Species richness and cover are determined for four height classes(strata) within each quadrat and aggregated by stratum over the entireplot. We estimated (1) the agreement between experienced trainers andinexperienced technicians who collected the data on this survey(accuracy) and (2) the agreement among the technicians (precision) forresults on species richness and cover from 3 test plots at 3 timeintervals. The methods appear to be highly precise, although somediscrepancies with the values obtained by the trainers were found.Trainers found significantly more species in the ground stratum (0–0.6 m) and measured significantly more cover in the uppermost stratum(>4.9 m). The proportion of variation due to measurement error andtemporal variability was less than 13% for species richness (all strata)and cover (all but one stratum). This indicates that the method issuitable for monitoring changes in species richness and canopy coverfor a large-scale synoptic monitoring project such as FHM. 相似文献
73.
Luis A. Gil-Alana 《Environmental Modeling and Assessment》2006,11(1):19-29
In this article we examine the stochastic behaviour of several daily datasets describing sun (total irradiance at the top
of the atmosphere and sunspot numbers) and various climatological anomaly series by looking at their orders of integration.
We use a testing procedure that permits us to consider fractional degrees of integration. The tests are valid under general
forms of serial correlation and deterministic trends and do not require estimation of the fractional differencing parameter.
Results show that the series are all nonstationary, with increments that might be stationary for those variables affecting
sun, and anti-persistent for those affecting air temperatures. 相似文献
74.
Despite the numerous benefits of hydropower production, this renewable energy source can have serious negative consequences on the environment. For example, dams act as barriers for the longitudinal migration of organisms and transport of particulate matter. Accelerated siltation processes in the receiving river reduce the vertical connectivity between river and groundwater. Hydropeaks, caused by short-term changes in hydropower operation, result in a negative impact on both habitat and organisms, especially during winter months when natural discharge is low and almost constant. In this study, we report the current deficits present in the River Rhone from two different scientific perspectives – fish ecology and hydrology. Potential rehabilitation solutions in synergy with flood protection measures are discussed. We focus on the effects of hydropeaking in relation to longitudinal and vertical dimensions and discuss local river widening as a potential rehabilitation tool. The fish fauna in the Rhone is characterized by a highly unnatural structure (low diversity, impaired age distribution). A high correlation between fish biomass and monotonous morphology (poor cover availability) was established. Tracer hydrology provided further details about the reduced permeability of the riverbank, revealing a high degree of siltation with K values of about 4.7 × 10?6 m s?1. Improving the hydrologic situation is therefore essential for the successful rehabilitation of the Rhone River. To this end, hydropeaks in the river reaches must be attenuated. This can be realized by a combination of different hard technical and soft operational measures such as retention reservoirs or slower up and down ramping of turbines. 相似文献
75.
Brito JA McNeill FE Chettle DR Webber CE Vaillancourt C 《Journal of environmental monitoring : JEM》2000,2(3):271-276
The study aims were to: (i) investigate long term human lead metabolism by measuring the change of lead concentration in the tibia and calcaneus; and (ii) assess whether improved industrial hygiene was resulting in a slow accumulation of lead in an exposed workforce. 109Cd excited K X-ray fluorescence was used to measure tibia lead and calcaneus lead concentrations in 101 workers in a secondary lead smelter. 51 subjects had had similar bone lead measurements 5 years previously. Most of the other subjects had been hired since the first survey. Measurements of whole blood lead were available for the large majority of subjects. Tibia lead concentrations fell significantly (p<0.001) in the 51 subjects with repeated bone lead measurements, from a mean of 39 microg Pb (g bone mineral)(-1) to 33 microg Pb (g bone mineral)(-1). The change correlated negatively with the initial tibia lead concentration, producing an estimate for an overall half-life of 15 years, with a 95% confidence interval of 9 to 55 years. Adding continuing lead exposure and recirculation of bone lead stores to the regression models produced half-life estimates of 12 and 9 years, respectively, for release of lead from the tibia. The repeat subjects showed no net change in calcaneus lead (64 microg Pb (g bone mineral)(-1) initially, 65 microg Pb (g bone mineral)(-1) 5 years later). Subjects not measured previously had average lead concentrations of 15 microg Pb (g bone mincral)(-1) in the tibia and 13 microg Pb (g bone mineral)(-1) in the calcaneus. The rate of clearance of lead from the tibia (9 to 15 years) is towards the more rapid end of previous estimates. The lack of a significant fall in the calcaneus lead was surprising. Attempts should be made to repeat this observation. If confirmed, it would have implications for models of lead metabolism. The relatively low lead concentrations in the non-repeat subjects are reassuring. However, observation after a longer period of employment would be desirable. 相似文献
76.
77.
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
78.
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
79.
Eolian (wind blown) sand constitutes a very serious problem to development in sandy desert lands and causes equally serious problems in lands that are undergoing desertification. In this paper, eolian sand movement due to bulk movement such as sand dune and ripple movement, sand drift by saltation, and sand storms by strong winds are discussed. Associated problems such as eolian sand encroachment on highways, farms, communities and industrial complexes are also discussed and workable solutions are offered. Solutions include chemical stabilization of the surface grains, fences to trap the blown sand and vegetation to prevent soil deflation. Vegetation is emphasized and recommended as the ultimate viable solution to combat desertification and eolian sand problems. 相似文献
80.
CO concentrations were measured in five kindergartens, one children's hospital and two homes for aged, practically without indoor sources, all situated in the city centre, for ten random days in winter and ten in summer. The indoor CO concentrations were the result of the distance from and the traffic density in the nearest street, of general pollution level, seasonal differences, day-to-day variations and daily cycle of air pollution, the vicinity of traffic having a dominant influence. Therefore location of institutions for sensitive population groups in old city centres within a block of houses seems to be a suitable solution as far as exposure to CO is concerned.Revised version of a paper presented as poster at the VIth World Congress on Air Quality, Paris 1983. 相似文献