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International audienceThe photodegradation of the organophosphorus fenamiphos was studied in various clay matrices: montmorillonite, kaolin and the mineral components of two soils collected from two different sites: Settat (S) and Berrechid (B). The degradation was shown to be mainly due to the direct excitation of fenamiphos and was similar for all the matrices with a two-step kinetics : a fast and a slower one. The first step rate obtained at the surface of montmorillonite was slightly lower than that determined at the surface of kaolin. The fenamiphos degradation process clearly depended on the amount of humic substances and iron(III). The latter component accelerated the disappearance of fenamiphos, while humic substances clearly inhibited the process. The degradation rate increased in the presence of water and was mainly due to the involvement of the photohydrolysis process leading to the scission of the P-O bond. The formation of the main by-products, sulfoxide, sulfone and phenol derivatives, were elucidated by HPLC/MS

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Thermoanalytical techniques, including differential thermal analysis (DTA) and thermogravimetric analysis (TGA), are considered as a way to determine the temperature history of concrete after fire exposure. TGA is essentially a means of observing the weight evolution of a sample as a function of temperature (dynamic heating) or time (isothermal heating). In its simplest form, the instrument used consists of a sensitive balance and a furnace arranged such that the sample holder sits inside the furnace. The system includes a thermocouple to monitor the sample temperature and a heating controller to maintain a constant temperature or change the temperature in a pre-determined fashion. DTA compares the temperature of a sample with that of a suitable reference material while both materials are heated at the same rate. Any difference in temperature between the two materials is detected by thermocouples whose signal is proportional to ∆T. To maintain the sample and reference material under similar conditions, both materials are embedded in a block of material with a large thermal mass. In theory, the temperature change in the sample should be proportional to the enthalpy change.