ISSN:0190-4167    

DOI:10.1080/01904168109362812

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904168109362813

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Plant responses to trace elements are dose dependent, therefore, comparisons with and interactions among trace elements can only be fully understood when considered in relation to the entire dose response curve. The entire curve as expressed by essential elements is composed of three continuous phases, deficiency, tolerance and toxicity. For nonessential elements only the last two phases are expressed.

ISSN:0190-4167    

DOI:10.1080/01904168109362814

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A systematic and realistic Research and Development strategy is described which will supply needed data to users of data to help choose technologies and processes which will be environmentally acceptable in the development of energy.

ISSN:0190-4167    

DOI:10.1080/01904168109362815

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The study of trace metal chemistry in soils which support crop plants is made complicated by the large number of reactions possible between trace metals and soil constituents and by the web of interrelations among trace metals and the macrocomponents of soil solutions which is created by these reactions. In a typical soil solution, there may be 10–20 different metal cations present (including trace metals) which can react with as many different inorganic and organic ligands to form 300–400 soluble complexes and up to 80 solid phases. In addition, redox, ion exchange, and specific adsorption reactions occur. GEOCHEM is a multipurpose computer program that calculates the chemical equilibrium in a soil solution where all of the reactions mentioned above can take place. The chemical principles and computational scheme on which this program is based are described. One important application of the program is to calculate the speciation of trace metals in the aqueous solution phase of an agricultural soil. This application is illustrated by a computer analysis of saturation extracts of representative soils which have received Cd either in sewage sludge or as Cd(NO3)2. The results of speciation calculations for Cd in the saturation extracts are presented and a discussion of the correlations possible between the principal soluble Cd species and the Cd taken up by a crop plant is given.

ISSN:0190-4167    

DOI:10.1080/01904168109362816

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904168109362817

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Energy dispersive X‐ray fluorescence (EDXRF) has been shown to be an effective technique for multielement analyses of plant tissues. Elements can be assayed above the atomic number of Na (11) including S, Cl, Br, and trace elements, except B. Once parameters and programs critical for quantitative analyses have been developed, analysis is relatively simple. Overall optimal pellet weights of 500 mg (32 mm diameter) and 100 mg (13 diameter) were chosen. It was found that weights could vary ± 25% without significant change in intensities. Samples ground to 1 mm, 20‐mesh, and 80‐mesh did not show significant intensity differences. When 1 g of boric acid was used to back pellets, intensities for light elements (Mg, Al, Si, P, S) were increased, but for higher atomic number elements intensities decreased from 60% to less than 20% those of non‐backed pellets.

ISSN:0190-4167    

DOI:10.1080/01904168109362818

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Recent developments in the analytical procedures for trace element assay in plant tissue ash have been toward automated procedures utilizing highly sophisticated instrumentation such as activation analysis, flameless atomic absorption spectroscopy, emission spectroscopy with plasma excitation, x‐ray fluorescence spectroscopy and voltometry. These techniques provide the analyst the ability to determine the concentration of trace elements well into the subparts per million range. Although the instrumentation procedures have their limitations and require special skills on the part of the analyst, the problem of sample preparation is still a major concern limiting the assay for a number of important elements. Trace level determination for elements, As, B, Cd, Co, Hg, Mo, Pb and Se is difficult. Acceptable reference standards are still needed as the current U.S. National Bureau of Standard Reference materials are not completely adequate. There is considerable evidence that there is significant element to analytical technique correlation which means the assay technique is a factor in the concentration found. This paper discusses procedures for sample preparation and analysis by various analytical procedures and reviews current and future analytical needs.

ISSN:0190-4167    

DOI:10.1080/01904168109362819

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A pyroantimonate precipitation reaction was utilized for localization of calcium, magnesium, manganese, potassium, and zinc ions inCucurbita pepoL. infected bySclerotinia sclerotiorum(Lib.) de Bary. Precipitation sites were easily observed in the cytoplasm adjacent to the cell walls, in the vacuoles, and to a lesser extent, in chloroplasts. The precipitate was analyzed for antimony content using energy dispersive X‐ray microanalysis. Counts of 5 channels of the La antimony peaks were analyzed. Electron dense precipitation sites in vacuoles had counts which averaged an order of magnitude greater than counts of cell walls and chloroplasts. Calcium deficient plants had the least amount of precipitation in cell walls and chloroplasts. Observed electron density in sections was not necessarily correlated with counts.

ISSN:0190-4167    

DOI:10.1080/01904168109362820

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

NBS issues six Standard Reference Materials that are useful for the determination of nutrient and contaminant trace elements in plant tissues and agricultural food products. They are: SRM 1571 Orchard Leaves, SRM 1573 Tomato Leaves, SRM 1575 Pine Needles, SRM 1570 Spinach, SRM 1567 Wheat Flour, and SRM 1568 Rice Flour. These SRM's are used to calibrate instrumentation, to determine the accuracy of existing analytical methods, and to develop more accurate methods. The Certificate of Analysis for each SRM contains such information as the homogeneity of the powdered material, the minimum sample size to be used, the certified values for the elements with their uncertainties, and the non‐certified values. A certified value is based either on concordant results by independent analytical methods or on results by a definitive method, i.e., an accurate method having negligible, systematic errors. These certified values can serve as cannon reference points for comparison of data acquired over a long period by various investigators using a variety of methods. Information on the preparation, methodology for certification, and use of these SRM's will be described. The development of a citrus leaves SRM will also be discussed.

ISSN:0190-4167    

DOI:10.1080/01904168109362821

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor