Methodologie de la dissertation

The methods recommended for ash collection depend on the purpose intended for the ash. For evaluation of health hazard, the grain-size distribution and composition of the ash may be assessed and the leachates may be analysed. If chemical analyses are carried out, ash should be dried at < 40 o C, but for compositional or grain-size analysis, the temperature is not crucial. If research is to be carried out on the leachates and surface reactivity of samples (. for toxicological analysis) it will be important to know the exact post-eruptive history of the ash in terms of rainfall and exposure. The quantity of ash needed should be assessed before collection. For example, grain-size analysis or compositional analysis may need small quantities (< 10 g) of ash whereas several kg may be required for toxicological analysis, particularly if a sample is to be shared between different laboratories. The following procedures should be adapted for the particular hazard assessment or research to be carried out but ensure that the ash samples can be used for grain-size analysis, characterization of composition and leachates, and assessment of volume of erupted material / total accumulated tephra (formation of isopach maps) etc.

Methodologie de la dissertation

methodologie de la dissertation

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