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Knowledge of the wood properties of tropi- cal tree species is still relatively limited, so timber extraction focuses on a few abun- dant, large-diameter species. Very little is known about small-diameter trees, although they could be used directly as roundwood for construction. The aim of this study was to determine the natural durability of 8 candi- date species for use as structural roundwood in French Guiana: Goupia glabra, Licania alba, Hymenopus heteromorphus, Lecythis per- sistens, Oxandra asbeckii, Pouteria bangii, Simarouba amara, Tachigali melinonii and Virola surinamensis. Samples of their wood were exposed to white rot (European and tro- pical), brown rot (European), and European subterranean termites (using non-choice and multi-choice tests) in laboratory conditions and subjected to screening tests adapted from European standards. Only two species were classified as durable against both fungi and termites: L. alba and P. bangii, which means they can be used without treatment as buil- ding material in tropical or temperate climates. The other species tested were classified (1) as durable but with notable differences observed in their resistance to fungi and termites res- pectively (G. glabra, L. persistens, O. asbeckii), (2) moderately durable (H. heteromorphus), (3) low durability to sensitive (T. melinonii, S. amara, V. surinamensis), meaning actual European standards would not let use these last species in outdoor structures without pro- tection, despite their use by local population in traditional building. However, they could be used for building purposes with appropriate protection systems (including wood protec- tion). The results we obtained for resistance to wood decay provide essential information to assess the potential of these eight tree species in French Guiana's construction sector.

The evolution of laws on the use of biocide products has led to important changes in the field of wood preservation leading to an increasing interest for non “biocidal treatments” like thermal or chemical modifications. While thermal modifications become more and more common on industrial scale,development of chemical modifications progresses slowly. One reason for the challenges encountered is probably the difficulty to use actual vacuum pressure plant to impregnate wood with solutions of reactive chemicals aimed to react with or within the wood. In this context, the presented research focuses on a new alternative called axial impregnation, derived from Boucherie process, for impregnation of treatable non durable hardwood species. This process consists of low-pressure impregnation of green wood logs through its lower extremity with treatment solution transiting via natural pathways of vessels. In order to evaluate the feasibility of the method, logs of different hardwood species were impregnated with a copper based preservative solution and the distribution of copper within the wood was determined. Results indicated that treatable wood species like beech, hornbeam and birch can be easily and homogeneously treated using axial impregnation method, while ash known for its weak impregnability remained untreated.

L'évolution des lois relatives à l'utilisation de produits biocides impose d'étudier des méthodes innovantes de traitement du bois. Dans ce contexte, les travaux de recherche présentés s'intéressent à une nouvelle alternative dite " non-biocide " impliquant la fabrication de composites bois massif / polymères obtenus par imprégnation de monomères et polymérisation in situ provoquée par chauffage. Le méthacrylate de méthyle, quatre acrylates organiques et trois acrylates hydrosolubles, ainsi que l'alcool furfurylique ont été testés. Les composites fabriqués ont été caractérisés : le polymère est bien présent dans le bois et il peut être résistant au lessivage à l'eau. Le bois a été densifié, les composites sont alors moins hydrophiles et plus stables dimensionnellement ; les propriétés mécaniques sont améliorées. Le traitement peut induire une durabilité conférée élevée. Parallèlement, une méthode d'imprégnation innovante a été testée : l'imprégnation axiale. Ce procédé consiste en l'imprégnation basse pression de billons de bois vert par une solution de traitement transitant via les voies naturelles de circulation de la sève. Des billons ont été imprégnés avec une solution de cuivre, dosé ultérieurement afin de s'assurer de la bonne répartition du produit dans le bois ; cela a permis la validation du procédé d'imprégnation axiale pour le hêtre, le charme et le bouleau. Enfin, des composites ont été fabriqués par imprégnation axiale de solutions aqueuses polymérisables à base d'alcool furfurylique ; ils sont résistants à la lixiviation à l'eau et moins hydrophiles que le bois naturel. Leur durabilité face aux champignons lignivores est améliorée, particulièrement dans le cas du traitement le plus concentré.

Mercury pollution has become an important current issue as a result of its environmental effects on a global scale. The Oak Ridge Reservation, established in 1942, was the designated site for the construction of the atomic bomb. During a 20-year period from 1944-1963 radioactive and toxic chemical pollutants, especially mercury compounds were released into the surrounding waterways.A germination study was conducted to investigate the ability of three tree species, American sycamore (Platanus occidentalis),shortleaf pine (Pinus echinata), and loblolly pine (Pinus taeda) seeds to germinate in mercuric nitrate (Hg(NO3)2 and methylmercury chloride (CH3HgCl) solutions. A subsequent greenhouse study was conducted to assess the phytotoxic effects of different mercuric solutions on Platanus occidentalis (American Sycamore), inoculated with soils from East Fork Poplar Creek.We also measured vegetation stress by Near Infrared (NIR) spectroscopy.The wavelengths examined were those thatare specific to chlorophyll and several carotenoids, which are involved in photosynthesis: 430 nm (Chl a), 448 nm (Chl b, carotenoids), 471 nm (carotenoids), 642 nm (Chl b), 662 & 680 nm (Chl a). Principal component analysis (PCA) was performed to identify patterns in sycamore leaf spectral data.Under in vitro conditions, as mercury concentration increased above 100 mg·kg-1, germination of all species decreased, with P. echinata being the least sensitive. Germination was inhibited more when seeds were exposed to methyl mercury chloride than to mercuric nitrate. Organic species of mercury proved to be more toxic than inorganic species of mercury in our greenhouse study. Significant changes occurred in levels of all pigments sampled (p430, p448, p471, p642, p662, and p680) over the course of the experiment. NIR spectroscopy was not sensitive enough to detect other chemical changes to foliage following mercury application.