Estimation of plant sampling uncertainty: an example based on chemical analysis of moss samples

Estimates of the distribution, migration, and accumulation of trace elements using mosses as bioindicators have successfully been used in biomonitoring studies since at least the 1970s. Chemical analysis of moss samples is also an important tool for assessing concentrations of elements in analyzed material at a given time. To achieve satisfactory accuracy in environmental studies, the best sampling approach must be used. Methods for the estimation of uncertainty derived from analytical procedures are well recognized, but the errors generated as a result of sampling are very often overlooked. Sampling uncertainty can be managed by a judicious selection of the sampling method, the amount of samples collected, and by following appropriate type of sampling protocols. The sampling protocol generally contains information about location of sampling sites, time of sampling (e.g., season), the species collected, type of sample (single, sub-sample), and monitored parameters (e.g., climate, analyzed substances). Information about seasonal variability; topographic, climatic, edaphic, and hydrologic conditions (type and amount of precipitation, rosewind); age; and part of plant that was collected is often ignored. There is no precise information on how these factors affect the sampling step and overall uncertainty over what procedures must be followed to reduce errors derived from plant sampling. This information is necessary when long-range and comparative studies are conducted. In this paper, we review how individual factors, such as (i) type of sampling strategy, (ii) representative sampling, (iii) seasonal variability, and (iv) which part of the plant is collected, may influence the concentration of trace elements in moss tissues and the level of uncertainty associated with sampling. In addition, we also discuss plant sample preparation techniques and how this may cause an uncontrolled element loss.

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Aspects of microanalysis in a transmission electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109690 ◽

1978 ◽

Vol 36 (1) ◽

pp. 510-511

Author(s):

R. Sinclair ◽

B.E. Jacobson

Keyword(s):

Grain Size ◽

Electron Beam ◽

Electron Microscope ◽

Chemical Analysis ◽

Transmission Electron Microscope ◽

Vapor Deposition ◽

Critical Currents ◽

X Ray ◽

Fine Grain ◽

Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

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Integrated morphometrical and electron energy loss image analysis in cytochemistry

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153981 ◽

1989 ◽

Vol 47 ◽

pp. 402-403

Author(s):

W.C. de Bruijn ◽

A.A.W. de Jong ◽

C.W.J. Sorber

Keyword(s):

Image Analysis ◽

Acid Phosphatase ◽

Chemical Analysis ◽

Active Form ◽

List Type ◽

Type Number ◽

Enzyme Cytochemistry ◽

Related Data ◽

Endogenous Peroxidase ◽

Electron Energy Loss

One aspect of enzyme cytochemistry is, whether all macrophage lysosomal hydrolytical enzymes are present in an active form, or are activated upon stimulation. Integrated morphometrical and chemical analysis has been chosen as a tool to illucidate that cytochemical problem. Mouse peritoneal resident macrophages have been used as a model for this complicated integration of morphometrical and element-related data. Only aldehyde-fixed cells were treated with three cytochemical reactions to detect different enzyme activities within one cell (for details see [1,2]). The enzyme-related precipitates anticipated to be differentiated, were:(1).lysosomal barium and sulphur from aryl sulphatase activity,(2).lysosomal cerium and phosphate from acid phosphatase activity and(3).platinum/di-amino-benzidine( D A B) complex from endogenous peroxidase activity.

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Microdomains in BaFeO3-y (0.35 < y < 0.50)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177039 ◽

1990 ◽

Vol 48 (4) ◽

pp. 780-781

Author(s):

M. Vallet-Regí ◽

M. Parras ◽

J.M. González-Calbet ◽

J.C. Grenier

Keyword(s):

Electron Diffraction ◽

Chemical Analysis ◽

Monoclinic Phase ◽

Orthorhombic Phase ◽

Total Iron ◽

Zone Axis ◽

Electron Micrograph ◽

X Ray Diffraction ◽

X Ray ◽

Compositional Variations

BaFeO3-y compositions (0.35<y<0.50) have been investigated by means of electron diffraction and microscopy to resolve contradictory results from powder X-ray diffraction data.The samples were obtained by annealing BaFeO2.56 for 48 h. in the temperature range from 980°C to 1050°C . Total iron and barium in the samples were determined using chemical analysis and gravimetric methods, respectively.In the BaFeO3-y system, according to the electron diffraction and microscopy results, the nonstoichiometry is accommodated in different ways as a function of the composition (y):In the domain between BaFeO2.5+δBaFeO2.54, compositional variations are accommodated through the formation of microdomains. Fig. la shows the ED pattern of the BaFeO2.52 material along thezone axis. The corresponding electron micrograph is seen in Fig. 1b. Several domains corresponding to the monoclinic BaFeO2.50 phase, intergrow with domains of the orthorhombic phase. According to that, the ED pattern of Fig. 1a, can be interpreted as formed by the superposition of three types of diffraction maxima : Very strong spots corresponding to a cubic perovskite, a set of maxima due to the superposition of three domains of the monoclinic phase along [100]m and a series of maxima corresponding to three domains corresponding to the orthorhombic phase along the [100]o.

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