Summary. HPLC analysis of secondary metabolites represents an efficient tool for the studying of plant chemical diversity under different
aspects: chemotaxonomy, metabolomics, adaptative responses to ecological factors, etc. Statistical analyses of HPLC databases,
e.g. correlation analysis between HPLC peaks, can reliably provide information on the similarity/dissimilarity degrees between
the chemical compounds. The similarities, corresponding to positive correlations, can be interpreted in terms of analogies
between chemical structures, synchronic metabolisms or co-evolution of two compounds under certain environment conditions,
etc. . In terms of metabolism, positive correlations can translate precursor-product relationships between compounds; negative
correlations can be indicative of competitive processes between two compounds for a common precursor(s), enzyme(s) or substrate(s).
Furthermore, the correlation analysis under a metabolic aspect can help to understand the biochemical origins of an observed
polymorphism in a plant species. With the aim of showing this, we present a new approach based on a simplex mixture design,
Scheffé matrix, which provides a correlation network making it possible to graphically visualise and to numerically model
the metabolic trends between HPLC peaks. The principle of the approach consisted in mixing individual HPLC profiles representative
of different phenotypes, then from a complete mixture set, a series of average profiles were calculated to provide a new database
with a small variability. Several iterations of the mixture design provided a smoothed final database from which the relationships
between the secondary metabolites were graphically and numerically analysed. These relationships were scale-dependent, namely
either deterministic or systematic: the first consisted of a monotonic global trend covering the whole variation field of
each metabolites’ pair; the second consisted of repetitive monotonic variations which gradually attenuated or intensified
along a global trend. This new metabolomic approach was illustrated from 404 individual plants of Astragalus caprinus (Leguminoseae), belonging to four chemical phenotypes (chemotypes) on the basis of flavonoids analysed in their leaves. After
smoothing, the relationships between flavonoids were numerically fitted using linear or polynomial models; therefore the co-response
coefficients were easily interpreted in terms of metabolic affinities or competitions between flavonoids which would be responsible
of the observed chemical polymorphism (the four chemotypes). The statistical validation of the approach was carried out by
comparing Pearson correlations to Spearman correlations calculated from the smoothed and the crude HPLC database, respectively.
Moreover, the signs of the smoothed relationships were finely supported by analogies and differences between the chemical
structures of flavonoids, leading to fluent interpretation in relation to the pathway architecture. 相似文献
We quantified the stability of nine stream fish assemblages by calculating coefficients of variation of population size for
assemblage members. Coefficients of variation were high and averaged over 96%; indicating that most assemblages were quite
variable. Coefficient of variation (CV) estimates were not significantly affected by: (1) years of study, (2) mean abundance,
(3) familial classification, or (4) mean interval between collections. We also detected minor regional differences in CVs.
The high variability exhibited by many stream fish assemblages suggests that it may be difficult to detect the effects of
anthropogenic disturbances using population data alone. Consequently, we urge managers to exercise caution in the evaluation
of the effects of these disturbances. More long-term studies of the ecological characteristics of undisturbed stream fish
assemblages are needed to provide a benchmark against which disturbed systems can be compared.
We suggest that CVs are a better estimator of population/assemblage stability, than either Kendall's W or the standard deviation
of the logarithms of numerical censuses. This conclusion is based on the following reasons. First, CVs scale population variation
by the mean and, hence, more accurately measure population variability. Second, this scaling permits the comparison of populations
with different mean abundances. Finally, the interpretation of CV values is less ambiguous than either of the aforementioned
metrics. 相似文献
The Clean Air Act, Public Law 88-206, was signed into law on December 17, 1963. Among the new provisions was the authorization given to the Secretary of the Department of Health, Education, and Welfare to award grants for the support of State and local air pollution control programs. The Chief, Division of Air Pollution, then requested the Surgeon General’s Air Pollution Training Committee to make recommendations for the most effective way to train the required numbers of people. The Committee called a special three-day meeting at Airlie House with about 30 consultants. Recommendations for training stemming from the meeting included: (1) University-based programs combined with practical experience in control program. (2) Criteria for the selection of trainees. (3) The outline of a model program. These recommendations were submitted to the Chief, Division of Air Pollution and are currently reflected in the activation of one program and a request to the Congress for funds to initiate two more such programs during Fiscal Year 1966. 相似文献
Atmospheric samples have been collected in Strasbourg between April 18 and May 29, 2007 and were analyzed for 71 current-use pesticides, of which 38 were detected. Average concentrations ranged from 0.09 ng m−3 for Fenarimol to 110.42 ng m−3 for Dimethachlor, which was slightly higher than the concentrations reported from other, comparable agricultural regions.Significant temporal variations were observed for 30 pesticides, and for most of them it could be shown that these were linked to time, temperature or atmospheric pressure. In several cases this helped to identify pesticide application just before or at the beginning of the sampling period, or ongoing treatment. Humidity, in contrast to previous reports, could not be linked to these variations. For the other 8 pesticides, only very little temporal variations were observed. Generally, these concentrations were low (less than 1 ng m−3), and it was assumed that they are not in use in Alsace at present. 相似文献
Various environmental factors are expected to affect the mobility of elements in chemically stabilized soils. The aim of this study was to evaluate the effects of pH, oxidizing-reducing potential (Eh), liquid-to-solid ratio (L/S), presence of organic matter (OM) and microbial activity (MA) on the mobility of chromium, copper, arsenic and zinc in zerovalent iron (Fe(0))-stabilized soil. A 2(5) full factorial design was applied to assess the leaching of the elements from the treated soil. The factor having the most impact on the mobility of Cr, Cu and Zn was pH; low pH (3) led to the release of these elements. Arsenic remobilization was controlled by L/S and MA, whilst Eh, though also significant, had less influence. In the identified worst-case scenarios, more than half of the total Zn and Cu and 14% of As can be expected to remobilize from the treated soil. The leaching procedure concerning sample agitation and type of filtration showed to substantially affect the results of As leaching, especially in OM rich soil. 相似文献
Investigations of polluted brownfield sites and sample analyses are expensive, and the resulting data are often of poor quality. Efforts are needed, therefore, to improve the methods used in investigations of brownfield sites to both reduce costs and improve the quality of the results. One approach that could be useful for both of these purposes is the triad strategy, developed by the US Environmental Protection Agency, in which managing uncertainty is a central feature. In the investigations reported here, a field study was conducted to identify possible ways in which uncertainties could be managed in practice. One example considered involves optimizing the uncertainty by adjusting the sizes of samples and the efforts expended in analytical work according to the specific aims of the project. In addition, the potential utility of several toxicity assessment methods for screening sites was evaluated. As well as presenting the results of these assessments, in this contribution we discuss ways in which a flexible work strategy and screening methods inspired of the triad philosophy could be incorporated into the Swedish approach to remediate brownfield sites. A tiered approach taking advantage of field and screening methods is proposed to assess brownfield sites focusing on the response and acceptable uncertainty that are required for the task. 相似文献
The continuous discharge of diverse chemical products in the environment is nowadays of great concern to the whole world as some of them persist in the environment leading to serious diseases. Several sampling techniques have been used for the characterization of this chemical pollution, although biomonitoring using natural samplers has recently become the technique of choice in this field due to its efficiency, specificity, and low cost. In fact, several living organisms known as biomonitors could accumulate the well-known persistent environmental pollutants allowing their monitoring in the environment. In this work, a review on environmental biomonitoring is presented. The main sampling techniques used for monitoring environmental pollutants are first reported, followed by an overview on well-known natural species used as passive samplers and known as biomonitors. These species include conifer needles, lichen, mosses, bees and their byproducts, and snails, and were widely used in recent research as reliable monitors for environmental pollution.
Polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxin and furan (PCDD/F) concentrations in the atmosphere were analysed using passive air samplers (PAS) close to the Rhine River between France and Germany. Collectors were placed in industrial, urban, rural and remote areas (Vosges Mountains) between March 2009 and August 2010, and the mean PCB concentrations (sum of 22 congeners) were 3.3, 3.9, 4.1 and 1.4 ng?PAS?1?day?1, respectively. Two events during the sampling period were observed in April 2009 and February–March 2010 with the highest PCB concentrations found in the industrial area (19.6 ng?PAS?1?day?1). PCDD/F level were measured during these periods, and the maximum concentration observed was from 37.5 fg?WHO?PAS?1?day?1相似文献
Environmental Science and Pollution Research - Environmental pollution is one of the major problems facing human health, ecosystems, and biodiversity. This is particularly the case for water... 相似文献
A coalition framework is proposed to address the contentious issues facing agriculture and the environment in urbanising areas, by bringing stakeholders together in homogeneous focus groups to identify areas of common interests, and then in heterogeneous groups to validate the results of the framework. Such a framework encourages greater understanding, consensus building, the resolution of conflicts, and the establishment of coalition efforts in areas of mutual interest and agreement by allowing stakeholder groups collectively to pursue agenda-building on issues of common interests. Based on the authors' observation of the process over an 18-month period, it is encouraging that the coalition framework is an appropriate strategy for building consensus among diverse audiences. 相似文献