Fate and ecotoxicological impact of new generation herbicides from the triketone family: An overview to assess the environmental risks.

Triketones, derived chemically from a natural phytotoxin (leptospermone), are a good example of allelochemicals as lead molecules for the development of new herbicides. Targeting a new and key enzyme involved in carotenoid biosynthesis, these latest-generation herbicides (sulcotrione, mesotrione and tembotrione) were designed to be eco-friendly and commercialized fifteen-twenty years ago. The mechanisms controlling their fate in different ecological niches as well as their toxicity and impact on different organisms or ecosystems are still under investigation. This review combines an overview of the results published in the literature on ß-triketones and more specifically, on the commercially-available herbicides and includes new results obtained in our interdisciplinary study aiming to understand all the processes involved (i) in their transfer from the soil to the connected aquatic compartments, (ii) in their transformation by photochemical and biological mechanisms but also to evaluate (iii) the impacts of the parent molecules and their transformation products on various target and non-target organisms (aquatic microorganisms, plants, soil microbial communities). Analysis of all the data on the fate and impact of these molecules, used pure, as formulation or in cocktails, give an overall guide for the assessment of their environmental risks.

A new route for local probing of inner interactions within a layered double hydroxide/benzene derivative hybrid material.

This paper presents the preparation and characterization of hybrid hydrotalcite-type layered double hydroxides (Zn1-xAlx(OH)2HBSx.nH2O, with x=0.33) where HBS is the 4-phenol sulfonate, with a detailed analysis of the grafting process of this organic entity onto the host lattice. As a set of the usual techniques (XRD, TG-DT/MS, FTIR and 27Al MAS NMR) was used to characterize the hybrid materials, this work focuses on a joint study by X-ray photoelectron spectroscopy and some quantum-calculation modeling in order to highlight the nature of the interactions between the organic and the mineral sub-systems. For the as-prepared hybrid material, the main results lead to a quasi-vertical orientation of the organic molecules within the mineral sheets via H-bond stabilization. By heating the hybrid material up to 200 degrees C, the structure shrinks with the condensation of the organics; the different theoretical modeling done gives an energy-stable situation when a direct attachment of the HBS sulfonate group sets up with the mineral layers, in agreement with the recorded XPS experimental data.

Differentiation of mobile and immobile pesticides on anionic clays by 1H HR MAS NMR spectroscopy.

Adsorbed vs. intercalated MCPA (4-chloro-2-methylphenoxyacetic acid) in highly hydrated clays taken as a soil model were clearly distinguished by 1H HR MAS NMR; adsorbed herbicide gave sharp signals indicating high mobility while intercalated herbicide gave very wide unresolved spectra due to its strong interaction with the solid matrix.

Syntheses and Thermal and Chemical Behaviors of Tartrate and Succinate Intercalated Zn(3)Al and Zn(2)Cr Layered Double Hydroxides.

Tartrate and succinate anions have been intercalated in Zn(3)Al and Zn(2)Cr LDHs. The preparations using either coprecipitation, anion exchange, or reconstruction methods are described. In the case of tartrate-containing LDH, coprecipitation and reconstruction methods have proved to be very limited to lead to pure materials due to the particular reactivity of tartrate anions. Intercalation of both anions under room-temperature conditions gives rise to expanded LDH with similar basal spacing. Moderate thermal treatments lead in all cases to a reorientation of the anions in the interlayer domains associated with an interlayer contraction occurring around 80 degrees C. The structural characterization, the thermal evolution, and the chemical stability of all the phases are studied by PXRD, FTIR, TGA, and DTA.