International Biodeterioration最新文献

A degradation of PE foils occurs in mouse-liver homogenates under an origination of carbonyl groups. The growth of ketonic (1715 cm⁻¹) above all and, then, of ester (1745 cm⁻¹) and aldehyde (1730 cm⁻¹) absorption bands has been proved by the method of infrared spectroscopy. Unsaturated structures are also evident besides oxygenous groups. The ascertained PE chemical changes are discussed with analogical findings of implanted plastics in a human organism.

Archaeological wood and wood of historic value from different environments were examined to determine the type of degradation present, extent of deterioration and to characterize the current condition of the wood. Micromorphological and ultrastructural investigation showed diverse forms of biological as well as non-biological deterioration. Wood from a cabinet in the Thomas A. Edison Laboratory Museum, Fort Myers, Florida (40–60 years old) appeared soft and shredded. The unusual deterioration resulted from a chemical spill of caustic substance(s) that gradually delignified the wood. Middle lamellae were removed from the woody cell walls leaving detached secondary wall layers. Samples of furniture and tomb structure from Tumulus MM, Gordion, Turkey (700 BC), considered to be the tomb of King Midas, had extensive soft rot. Extensive cavity formation was observed throughout the S₂ layers of secondary walls. Egyptian samples (3000-1000 BC) were attacked primarily by brown rot fungi. Localized areas of severely degraded wood contained cells that appeared porous and lacked structural intergrity. The lignified residue that remained fragmented into dust-like particles. An unusual form of soft rot with cavities within the S₁ layer of the secondary wall also was found in one Egyptian object. Ancient buried, waterlogged wood (10 000–4000 BC) was degraded by tunneling and erosion forms of bacteria. Minute cavities and a diffuse attack of the cell wall occurred. These ultrastructural results provide information concerning the current condition of the wood and also a chronology of past degradative processes that are essential to ascertain the most appropriate methods of conservation.

The colonization and deterioration of building materials from three Spanish cathedrals by lichens and bryophytes was investigated. The materials included sandstones, limestones, granites, tiles, flagstones and mortars. The colonization of the different types of materials by lichens was induced, to a great extent, by the input of bird excrements, giving rise to a characteristic ornithocoprophilous flora. Communities of mosses grew preferentially on mortars with pronounced disintegrating effects due to penetration of rhizoids. Both lichens and bryophytes lead to mechanical and chemical damage to stonework. This represents a stage in the succession which gives rise to the later invasion by vascular plants, whose roots cause important deterioration in the structure of the buildings, mainly roofings, tiles, guttering, etc.

The heterotrophic bacteria population occurring on decaying sandstone from ancient monuments has been examined. Quantitative and qualitative observations are presented for seasonal variation over a period of 1 year. The diversity of heterotrophs occurring on sandstone was assessed on a monthly basis using a range of isolation media. An increase in numbers of bacteria was seen during the winter months: with both Gram-negative and Gram-positive types present. Gram-positive bacteria, especially spore-formers of the genus Bacillus, were found exclusively in the dry summer months. Decay activity, reflecting the potential of natural mixed populations present on the stone, also showed seasonal variation and this was related to the pattern of change for the bacterial species observed.

Three strains of Pseudomonas bacteria were isolated from copper water pipes showing pitting corrosion. The effects of temperature and copper concentration on growth and exopolymer production were investigated. Various differences were noted between the organisms when grown as pure cultures and as a mixed culture; from the pure culture work some of the contributions made by each organism to the mixed culture can be deduced.

It would appear that the production of extracellular products varies with temperature and that polymer production and growth are enhanced in a mixed culture. All three strains grown as pure cultures showed a decrease in growth at lower temperatures as the copper concentration was increased. This effect was altered when the organisms were grown as a mixed culture. It was noted that copper tolerance was conferred on one of the organisms (a yellow strain of Ps. paucimobilis) by the presence of the other two. These results can be used to explain some of the observations made on the colonisation of copper by bacteria associated with pipe corrosion.

The effect of bacterial growth products on seven industrial biocides used in metalworking fluids was evaluated. Prior bacterial growth in two typical metalworking fluids resulted in a substrate that uniformly reduced the effectiveness of all biocides when compared to the same unused metalworking fluids. Two selective results of growth in metalworking fluid, lowering of pH and production of sulfide, only affected two of the biocides.