High Degree Of Biodegradability Research Articles

Oil Seeps from the "Boulganack" Mud Volcano in the Kerch Peninsula (Ukraine - Crimea), Study of the Mud and the Gas: Inferences for the Petroleum Potential

Mud volcanoes act as prospecting indices in the exploration of oil and gas deposits with gases and muds excreted. A methodology and an analytical protocol have been developed in order to classify the petroleum provinces according to the geochemical information available from the mud volcanoes. Such a study allows us to evaluate the potential of the petroleum system beneath. The Crimean-Caucasus region is renowned for mud volcano activity with well-known areas from west to east: Kerch Peninsula, Kuban and Azerbaijan. A methodology concerning the geochemical sampling and analysis of the mud volcanoes located onshore was applied to the Kerch Peninsula. Three field trips were organised by IFP in 2000, 2001 and 2002 in order to collect geochemical data, in agreement with the Museum of National History in Kiev. During these geological and geochemical surveys particular attention was given to the Boulganack mud volcano, which is a favourable site for the study of mud and gas samples due to the variety of the types of the vents. Specific tools were built in order to take samples of mud, up to 20 m deep in the vents, and gas more than 25 m away from the bubbling point in safe conditions in the deep mud lakes. Moreover, monitoring of the sampling of the gas was undertaken on the Boulganack mud volcano for one year in order to study the variation in the composition of the gas in time and space in the various vents. The proportions of nitrogen, carbon dioxide and hydrocarbons (methane to ethane) were measured. The vents of the Boulganack mud volcano present about 90% of methane and 10% CO2 , with a few percent of heavier hydrocarbons in one particular vent: Andrusov. Pavlov expelled more CO2 (25% to 40%), with the greatest temporal variations. Only Obrudchev expels as much carbon dioxide as methane (50/50). Sometimes, nitrogen was also measured (Pavlov, Obrudchev and Central Lake). The high dryness of the gas implies a loss of heavy hydrocarbon compounds relative to a typical thermogenic gas. Chemical gas compounds are highly dependent from one vent to the other. The comparison of the quantity of hydrocarbon included in the mud released from the mud volcanoes of the Kerch Peninsula and those of Azerbaijan (used as a reference) shows very little hydrocarbon in the mud from the mud volcano in the Crimea, whereas accumulations of hydrocarbons exist in the fluids expelled from mud volcanoes in Azerbaijan. In fact, the ranking of the petroleum provinces is linked to the occurrence of the free hydrocarbons in the mud excreted by mud volcanoes. Analysis by chromatography of the saturated hydrocarbons presents a high degree of biodegradation when the samples are taken at the surface. When they are taken with the core barrel at greater depth in the vents, the hydrocarbons are preserved with a typical continental origin which can be compared with the organic matter of the Maykop formation. The modelling of the hydrocarbon window geohistory confirms that the hydrocarbons are mainly produced within the lower Maykop. The generation of gas is favoured, in agreement with the quality of the type III source rocks in this western part of the Caucasus.

Contribution to the Study of Fungal Attack on Some Plasticized Vinyl Formulations

The objective of this study was to develop new vinyl flooring formulations with increased resistance to fungi and microorganisms attack, by using plasticizers having a chemical composition different from that of common di-ethylhexyl phthalate (DOP). It is suspected that during the vinyl flooring life service, the attack of fungi and microorganisms leads to the degradation of DOP and the release of some volatile organic compounds (VOC). For this reason the new materials were formulated with plasticizers having chemical composition different of that of DOP i.e.: diethyleneglycol dibenzoate (2–45), tricresyl phosphate (Lindol) and phenol alkylsulphonic ester (Mesamoll). For the same reason in the new flooring formulations the vinyl polymer, vinyl chloride-vinyl acetate copolymer (VC-VAc), was partially replaced with lignin (L) a natural polymer and major component of wood and vascular plants. Besides its other functions in wood, L imparts resistance to the most microorganisms attack. An organosolv lignin Alcell lignin (AL) was utilized as partial replacement of VC-VAc copolymer. The influence of the new plasticizers, as well as the influence of the partial replacement of VC-VAc copolymer with L on the resistance of the new formulations to fungal attack was evaluated following a standard procedure given in ASTM G 21–2002 “Determining Resistance of Synthetic Polymeric Materials to Fungi”. The evaluation has been undertaken for controls (formulated without AL) and blends (formulated with 20 parts AL) specimens. Test specimens were inoculated with a mixture of five fungi. Following 28 days of incubation at 28°C and 95% relative humidity, the specimens were examinated visual and under the microscope and rated for fungal growth. Weight loss, changes in mechanical properties and changes in glass transition temperature due to the effect of biodeterioration were also determined. Although each plasticizer has a specific resistance to hydrolysis due to differences among ester groups, the visible effects of fungal attack, in formulations without AL, is similar for all plasticized controls, with the exception of formulations incorporating diethyleneglycol dibenzoate (2–45) in which a higher degree of biodegradation was always present. Based on the weight loss of specimens formulated without AL, their resistance to fungal attack can be rated as follows: $$\hbox{Lindol} > \hbox{Mesamoll} \ge \hbox{DOP}> 2-45$$ . The same rating is applicable for blend specimens. The results have demonstrated that each particular AL-plasticizer-additives formulation has its specific mechanism of biodegradation.

Environmental features of two commercial surfactants widely used in soil remediation

One of the main limitations for a wider application of surfactants in soil remediation is the lack of knowledge about environmental fate and toxicity of surfactant itself especially for in situ application. Sorption behaviour, biodegradability, toxicity of parent compound and its metabolites are important processes that affect environmental fate of surfactants in site remediation applications. Tween 80 (poly(oxyethylene)(20)-sorbitane monooleate) and Aerosol MA +80 (dihexyl sodium sulfosuccinate) are surfactants that have been tested in laboratory and field scale remediation of soil and groundwater. In this work, the sorption and biodegradability of these surfactants were assessed to provide conditions and limitations for their use. The soil used in this experimentation was analysed for organic carbon content, soil bacteria, and size fraction and resulted to be a good model because is characterised by mean values for almost all considered parameters. Tween 80 showed high degree of biodegradability but a high affinity for soil matrix. Results suggest that Tween 80 could find its best application in ex situ solid phase remediation like ex situ bioremediation; its high affinity to soil could limit in situ applications. Biodegradation tests for Aerosol MA +80 show low degree of biodegradability and mineralisation. Biodegradation experiments, coupled with analysis of toxicity, could support the hypothesis that degradation of Aerosol MA +80 is not complete and leads to an accumulation of intermediates with at least the same toxicity of the parental compound. Therefore, aquifer remediation application with Aerosol MA +80 has to be conducted with necessary precautions to avoid product loss and excess surfactant should be flushed from the soil.

Effects of periodate and chondroitin 4-sulfate on proteoglycan stabilization of ostrich pericardium. Inhibition of calcification in subcutaneous implants in rats

Chemical modification of biological materials used in the manufacture of cardiac valves tends to reduce the relatively high degree of biodegradation and calcification of the implanted bioprostheses. The most widely used treatment to reduce biodegradability of the valves is glutaraldehyde fixation. However, this treatment is potentially toxic and induces tissue calcification. In order to minimize these undesirable effects, we have analyzed the effect of a pre-fixation of endogenous proteoglycans and exogenous glycosaminoglycans, as well as the borohydride reduction influence on the different modified ostrich pericardium implants after subcutaneous implantation in rats. The presence of calcific deposits was detected in all implanted GA-fixed samples; however, calcification was highly reduced in both groups of periodate-prefixed materials, which showed also a very low Ca/P molar ratio. Borohydride post-treatment of these biomaterials resulted in a significant increase in calcium phosphate precipitation, with the appearance of calcium deposits mainly in an amorphous form even though X-ray diffraction allowed the detection of brushite- and apatite-like crystals. Regarding tissue stability, no significant differences were found among the borohydride-untreated implants but higher levels of matrix metalloproteinases were observed by gelatin zymography in the periodate pre-fixed materials. This increase was partially reduced by pre-fixation of exogenous chondroitin 4-sulfate. On the other hand, borohydride post-treatment not only increased calcification, but also reduced tissue stability and increased the presence of matrix-degrading activities.

Ring‐opening copolymerization of racemic β‐butyrolactone with ϵ‐caprolactone and δ‐valerolactone by distannoxane derivative catalysts: study of the enzymatic degradation in aerobic media of obtained copolymers

AbstractIn this study, we have prepared predominantly syndiotactic poly([R,S]‐β‐hydroxybutyrate) using different distannoxane catalyst systems (1‐hydroxy‐3‐chlorotetrabutyldistannoxane, 1‐ethoxy‐3‐chlorotetrabutyldistannoxane, 1,3‐dichlorotetrabutyldistannoxane, and dibutyltin oxide). Copolymers poly([R,S]‐β‐hydroxybutyrate‐co‐ϵ‐caprolactone), P(BL‐co‐CL), and poly([R,S]‐β‐hydroxybutyrate‐co‐δ‐valerolactone), P(BL‐co‐VL), have also been synthetized from the ring‐opening copolymerization of (R,S)‐β‐BL with ϵ‐caprolactone (CL) and δ‐valerolactone (VL) using hydroxy‐ and ethoxydistannoxanes catalysts. The enzymatic degradability of these polymers was studied in aerobic medium. The objective of this work was to determine the influence of the tacticity and crystallinity of the corresponding polymers on their degree of aerobic biodegradation and on their initial degradation rate. It was shown that the degradation rate value measured for bacterial PHB 100% (R) was the highest and the degree of aerobic biodegradation reached around 94% after 36 days. A percentage of final biodegradation of about 35% was obtained for predominantly syndiotactic PHB. This result is agreement with the calculated result obtained from triads sequences. The influence of crystallinity on the initial degradation rate was observed for the copolymers P(BL‐co‐CL) and P(BL‐co‐VL) of various feed ratios. All these, copolymers, synthetized from distannoxane catalysts, exhibit a high degree of biodegradation of around 75–88%.© 2002 Society of Chemical Industry

Gelatinases in soft tissue biomaterials. Analysis of different crosslinking agents

Chemical modification of pericardium-based cardiac valves tends to reduce the relatively high degree of biodegradation and calcification of the implanted bioprostheses. We analysed the tissue properties of pericardium from young calves and pigs after crosslinking with different agents (glutaraldehyde, diphenylphosphorylazide (DDPA), 1-ethyl-3,3-dimethyl-aminopropyl-carbodiimide (EDAC)) and when exposed to anticalcification treatments (chloroform/methanol or ethanol) prior to glutaraldehyde (GA) crosslinking. Protein extraction after tissue homogenisation in the presence of detergents showed that crosslinking using GA or DPPA was much more effective. The amounts of protein extracted from these two groups of chemically modified pericardium were significantly lower; the other modified tissues presented only a slight reduction when compared with untreated tissue. Matrix metalloproteinases- (MMP) 2 and 9 were detected in native pericardium from calf and pig by zymography. While the MMP-9/MMP-2 activity ratio was close to 1 in pig pericardium, it was 8.5-fold higher in bovine tissue. Crosslinking with GA and with DPPA almost completely abolished gelatinase activities, even when equal amounts of solubilised protein were loaded onto the zymograms. Anticalcification treatments followed by GA crosslinking or treatment with EDAC were not as effective in reducing gelatinase activities; but, interestingly, a relative reduction of MMP-9 versus MMP-2 was detected. The presence of these gelatinase activities in pericardium may contribute to the in vivo degradability of pericardium-based cardiac valves.

Monitoring the stereoselectivity of biodegradation of chiral polychlorinated biphenyls using electrokinetic chromatography

A study of the biodegradation of several chiral polychlorinated biphenyls (PCBs, IUPAC numbers 45, 88, 91, 95, 136, 144, 149, and 176) by a naturally occurring soil bacterium as well as the stereoselectivity of such process has been performed using Electrokinetic Chromatography with cyclodextrins (CD-EKC). In order to achieve the analysis of chiral PCBs, a CD-EKC system based on 50 mM 2-morpholinoethanesulfonic acid (MES) buffer (pH 6.5) containing 2 M urea, 20 mM carboxymethylated γ-cyclodextrin (CM-γ-CD), and 10 mM β-cyclodextrin (β-CD) was used. First, the percentage degradation of PCBs by the microorganism used in this work was measured for different incubation times (22, 46, 71, 93, 165, 213, and 262 hours). The results showed a high degree of biodegradation (from 61% to 94%) for the eight PCBs studied after 262 hours of incubation with the microorganism, degradation being favoured for the least chlorinated congeners. Secondly, measurement of the atropisomeric ratio of the PCB atropisomers during the biodegradation process revealed no significant variation of the atropisomeric ratios with the degradation time, indicating a non-stereoselective degradation of PCBs by the microorganism.

Biogenic methane generation in the degradation of eastern Australian Permian coals

Hydrocarbons extracted from one Sydney Basin coal have a distribution of aromatic and aliphatic hydrocarbons consistent with a high degree of biodegradation as previously demonstrated for Bowen Basin coals. On the same basis, hydrocarbons from two other coals from the Sydney Basin are less biodegraded and display an additional minor series of alkylaromatic degradation products. All these degradation reactions generate CO 2 which on biogenic reduction to CH 4 is reservoired in association with the Permian coal-seams of the Sydney and Bowen Basins, Australia. Variations in access to oxygenated waters, nutrients and micro-organisms are held to be largely responsible for the extent of biodegradation of coal hydrocarbons and for the reduction of CO 2.

Synthesis and degradation of polyesters

Copolymers of racemic β-butyrolactone (β-BL) with e-caprolactone (e-CL) P(BL-co-CL) and δ-valerolactone (δ-VL) P(BL-co-VL) were prepared by ring-opening polymerization using a commercial aluminoxane catalyst, tetraisobutyldialuminoxane (TIBAO). The yields, molecular weights, compositions and crystallinities have been determined for both copolymers by gel permeation chromatography (GPC), nuclear magnetic resonance ( 1 H NMR), and differential scanning calorimetry (DSC). The determination of monomer diad sequence distributions was carried out by 13 CNMR. These results and those of reactivity ratios indicate that the copolymers may consist of compatible blocks of BL units and VL units of variable size. Enzymatic degradability of these polymers has been studied in aerobic and anaerobic media. The crystallinity influences the initial degradation rate of copolymers P(BL-co-CL) and P(BL-co-VL) of various feed ratios. All the copolymers synthesized with TIBAO catalyst exhibit a high degree of biodegradation (around 85%) except for those containing a very high portion of unsubstituted CL or VL units. Anaerobic biodegradation of PHB and copolymers P(BL-co-CL) is much lower than aerobic biodegradation, even for bacterial P([R])-HB) and the initial rates follow the same trend.

Ring‐opening homopolymerization and copolymerization of lactones. Part 2. enzymatic degradability of poly(β‐hydroxybutyrate) stereoisomers and copolymers of β‐butyrolactone with ɛ‐caprolactone and δ‐valerolactone

In this study, we have prepared poly([R,S ]-β-hydroxybutyrate) (P([R,S ]-β-HB) or PHB) from [R ,S]-β-butyrolactone ([ R,S]-β-BL), using different aluminoxane catalyst systems (triethylaluminium/water, triisobutylaluminium/water, trioctylaluminium/water and tetraisobutyldialuminoxane/water). By varying the ratio of catalyst to water and using a method of fractionation of polymers, PHB with different isotactic diad fractions (i) (from 0.41 to 0.72) and crystallinities were obtained. Copolymers poly(butyrolactone-co-caprolactone) (P(BL-co-CL)) and poly(butyrolactone-co-valerolactone) (P(BL-co-VL)) have also been synthesized from the ring-opening copolymerization of [ R,S]-β-BL with either ε-caprolactone (CL) or δ-valerolactone (VL) using tetraisobutyldialuminoxane (TIBAO) catalyst. The enzymatic degradability of these polymers was studied in aerobic and anaerobic media. The objective of this work was to determine the influence of the tacticity and crystallinity of the polymers on their degree of biodegradation and on their initial degradation rate. It was shown that the degradation rate measured for bacterial PHB 100% [R] was the highest and the degree of aerobic biodegradation reached after 36 days was around 94%. A 40–50% biodegradation was obtained for synthetic PHB, highly isotactic and predominantly syndiotactic. The non-crystalline and atactic PHB synthesized from TIBAO catalyst had a very high degree of biodegradation of around 88%. This result may suggest that not only are the [R ]-BL units hydrolysed but also the [S ]-BL units. The influence of the crystallinity on the initial degradation rate was observed for the copolymers P(BL-co-CL) and P(BL-co -VL) of various feed ratios. All these copolymers synthesized from TIBAO catalyst, exhibit a high degree of biodegradation of around 85% except for copolymers containing a very high portion of unsubstituted units, CL or VL. The anaerobic biodegradation of PHB and copolymers P(BL-co -CL) is much lower than the aerobic biodegradation, as are the initial rates, even for bacterial P([R ]-HB). © 1999 Society of Chemical Industry

Ring-opening homopolymerization and copolymerization of lactones. Part 2. enzymatic degradability of poly(β-hydroxybutyrate) stereoisomers and copolymers of β-butyrolactone with ɛ-caprolactone and δ-valerolactone

In this study, we have prepared poly([R,S ]-β-hydroxybutyrate) (P([R,S ]-β-HB) or PHB) from [R ,S]-β-butyrolactone ([ R,S]-β-BL), using different aluminoxane catalyst systems (triethylaluminium/water, triisobutylaluminium/water, trioctylaluminium/water and tetraisobutyldialuminoxane/water). By varying the ratio of catalyst to water and using a method of fractionation of polymers, PHB with different isotactic diad fractions (i) (from 0.41 to 0.72) and crystallinities were obtained. Copolymers poly(butyrolactone-co-caprolactone) (P(BL-co-CL)) and poly(butyrolactone-co-valerolactone) (P(BL-co-VL)) have also been synthesized from the ring-opening copolymerization of [ R,S]-β-BL with either e-caprolactone (CL) or δ-valerolactone (VL) using tetraisobutyldialuminoxane (TIBAO) catalyst. The enzymatic degradability of these polymers was studied in aerobic and anaerobic media. The objective of this work was to determine the influence of the tacticity and crystallinity of the polymers on their degree of biodegradation and on their initial degradation rate. It was shown that the degradation rate measured for bacterial PHB 100% [R] was the highest and the degree of aerobic biodegradation reached after 36 days was around 94%. A 40–50% biodegradation was obtained for synthetic PHB, highly isotactic and predominantly syndiotactic. The non-crystalline and atactic PHB synthesized from TIBAO catalyst had a very high degree of biodegradation of around 88%. This result may suggest that not only are the [R ]-BL units hydrolysed but also the [S ]-BL units. The influence of the crystallinity on the initial degradation rate was observed for the copolymers P(BL-co-CL) and P(BL-co -VL) of various feed ratios. All these copolymers synthesized from TIBAO catalyst, exhibit a high degree of biodegradation of around 85% except for copolymers containing a very high portion of unsubstituted units, CL or VL. The anaerobic biodegradation of PHB and copolymers P(BL-co -CL) is much lower than the aerobic biodegradation, as are the initial rates, even for bacterial P([R ]-HB). © 1999 Society of Chemical Industry

Functional fluids and additives based on vegetable oils and natural products: A review of the potential

AbstractFunctional fluids and additives normally have an ‘R — P’ type of linear chemical structure, where ‘R’ is a linear or isoalkyl chain, and ‘P’ is a mild‐to‐strong polar group. For functional fluids ‘P’ is non‐polar to mildly polar, and for additive molecules it is mild to highly polar. The additive activity depends upon the degree of polarity.Some natural products also have predominantly linear structures in their constituents. Many of these are available in commercial quantities and some even occur as waste. These could be used for the synthesis of functional fluids and additives. This paper covers three groups of such natural products. These are non‐edible vegetable oils, terpenes, and cashew nut shell liquid. The synthesis and characteristics of functional fluids and a variety of possible additives are described. Besides being an alternative non‐petroleum resource, such products have a high degree of biodegradability, as they are derivatives of natural products.

Petroleum biodegradation in the Tertiary reservoirs of the North Sea

A suite of 17 oil samples from the Tertiary reservoirs (Palaeocene-Eocene) of the North Sea was subjected to routine geochemical analytical techniques in order to evaluate the degree of biodegradation. The methods included latroscan TLC-FID, gas chromatography of the saturated and aromatic hydrocarbon fractions, gas chromatography-mass spectrometry of the saturated hydrocarbon fraction and stable carbon and hydrogen isotope analyses. In addition, API gravities and weight percentages of asphaltene were also determined. Based on these data it was found that oils in the suite were derived from the Jurassic aged Kimmeridge Clay Formation originating from source rock horizons at similar maturity levels. The oils in the suite were taken from reservoirs with present day temperatures 49–114°C. Differences in the chemical composition of the oils (e.g. reduced relative amounts of saturated hydrocarbons, increased polar amounts and reduced relative concentrations of n-alkanes), were attributed to secondary alteration processes of which the most likely process to occur at temperatures less than 80°C and consistent with the observed chemical characteristics of the oils is biodegradation. The differences in chemical composition are thus attributed to different degrees of biodegradation. The oils were ranked and classified in terms of the degree of biodegradation using a range of restricting parameters based on the gas chromatographic concentrations of different alkane species. Based on these parameters, oils were divided into four classes. These classes are (a) non to slightly biodegraded; (b) mildly biodegraded; (c) moderately biodegraded; and (d) severely biodegraded. In cases where the degree of biodegradation was found to have reached levels where unambiguous identification of alkanes was not possible, unresolved complex mixture (UCM) parameters were utilised to assess the extent of biodegradation. The degree of biodegradation was subsequently compared to the type of reservoir sandstone facies from which oils in this study were taken. It was found that at similar temperatures, oils in the Balder Formation (Upper Late Palaeocene) were biodegraded to a higher degree compared to oils from either The Forties (Lower Late Palaeocene) or Sele (Middle Late Palaeocene) Formation. The higher degree of biodegradation in Balder reservoirs is attributed to relatively greater openness to meteoric water invasion in these reservoirs.

97/00141 Method and apparatus to improve secondary froth quality within oil and oil extraction process

A suite of 17 oil samples from the Tertiary reservoirs (Palaeocene-Eocene) of the North Sea was subjected to routine geochemical analytical techniques in order to evaluate the degree of biodegradation. The methods included latroscan TLC-FID, gas chromatography of the saturated and aromatic hydrocarbon fractions, gas chromatography-mass spectrometry of the saturated hydrocarbon fraction and stable carbon and hydrogen isotope analyses. In addition, API gravities and weight percentages of asphaltene were also determined.Based on these data it was found that oils in the suite were derived from the Jurassic aged Kimmeridge Clay Formation originating from source rock horizons at similar maturity levels.The oils in the suite were taken from reservoirs with present day temperatures 49–114°C. Differences in the chemical composition of the oils (e.g. reduced relative amounts of saturated hydrocarbons, increased polar amounts and reduced relative concentrations of n-alkanes), were attributed to secondary alteration processes of which the most likely process to occur at temperatures less than 80°C and consistent with the observed chemical characteristics of the oils is biodegradation. The differences in chemical composition are thus attributed to different degrees of biodegradation.The oils were ranked and classified in terms of the degree of biodegradation using a range of restricting parameters based on the gas chromatographic concentrations of different alkane species. Based on these parameters, oils were divided into four classes. These classes are (a) non to slightly biodegraded; (b) mildly biodegraded; (c) moderately biodegraded; and (d) severely biodegraded. In cases where the degree of biodegradation was found to have reached levels where unambiguous identification of alkanes was not possible, unresolved complex mixture (UCM) parameters were utilised to assess the extent of biodegradation. The degree of biodegradation was subsequently compared to the type of reservoir sandstone facies from which oils in this study were taken. It was found that at similar temperatures, oils in the Balder Formation (Upper Late Palaeocene) were biodegraded to a higher degree compared to oils from either The Forties (Lower Late Palaeocene) or Sele (Middle Late Palaeocene) Formation. The higher degree of biodegradation in Balder reservoirs is attributed to relatively greater openness to meteoric water invasion in these reservoirs.

Formation and mobilization pathways of dissolved organic matter: evidence from chemical structural studies of organic matter fractions in acid forest floor solutions

Dissolved organic matter (DOM) is well recognized to influence the geochemistry of ecosystems. This study was conducted to determine the pathways of DOC mobilization in the forest floor of coniferous forests. DOM from the forest floor of two acid forest soils in the Fichtelgebirge (Germany) was fractionated into hydrophobic acids and neutrals, and hydrophilic acids and neutrals. Carbon distribution at both sites was similar: 53 and 52% hydrophobic acids, 23 and 22% hydrophilic acids, 10 and 11% hydrophobic neutrals, and 7 and 8% hydrophilic neutrals, respectively. Structural composition of the DOM fractions was determined using chemical degradation, FT-IR and 13C NMR spectroscopy, as well as pyrolysis-field ionization mass spectrometry. Results indicate different chemical composition of the DOM fractions within each site. Hydrophobic acids show high concentrations of carboxyl and hydroxyl groups, and a high ratio of vanillic acid to vanillin ( ca 1.0), both indicating a high degree of biodegradation of plant-derived compounds. Carbohydrates are covalently bound to apolar moieties and from carbohydrate composition a lignocellulose nature of the hydrophobic acid fraction is suggested. Hydrophilic acids can be differentiated from the hydrophobic acids by their higher degree of oxidative biodegradation. The hydrophilic acid fraction also exhibits a higher ratio of microbially released polysaccharides versus plant-derived polysaccharides. Hydrophobic neutrals show the closest relationships to the refractory soil humin, with less degraded dimeric ‘condensed’ lignin subunits and relatively high contents of non-carbohydrate aliphatics. Hydrophilic neutrals are enriched in carbohydrates mobilized by enzymatic cellulose and hemicellulose breakdown, as well as from microbial origin. We conclude that DOM release into forest floor solution is related to microbial activity by oxidative degradation of plant-derived organic matter (e.g. water-soluble lignin and lignocellulose fragments) and by production of microbial metabolites (e.g. polysaccharides). Overall evidence suggests that hydrophobic acids (i) represent intermediates in organic matter decomposition, which can be further degraded to hydrophilic acids and CO 2, and (ii) are precursors of humic substances in illuvial horizons after precipitation/adsorption.

The biological performance of calcium phosphate ceramics in an infected implantation site: II. Biological evaluation of hydroxyapatite during short-term infection.

Macroporous hydroxyapatite was implanted submucosally in the rat middle ear and studied after intratympanic injection of a Staphylococcus aureus suspension. The middle ear infection was induced 1 week after the implantation, and the effects of infection on the middle ear and the implant material were evaluated after 1, 3, 7, and 14 days by light and electron microscopy. The findings in the infected middle ear with an implant corresponded well with those described for the infected middle ear cavity without an implant. The reactions of the tissue over the implant were similar to those of the original mucosa of the middle ear. Bone was deposited on the implant and in its pores in relatively large quantities. Biodegradation, due at least partially to phagocytic activity of macrophages and multinucleated cells, was more prominent than previously found. This higher degree of biodegradation may be attributed to the use of the mucosal implantation technique, because this was the only point of divergence with respect to material or methods from earlier work reported by our group. The present results, together with those published earlier, suggest that this material has promising features for use as a bone substitute in reconstructive middle ear surgery. Definitive conclusions on biological performance and biofunctionality will, however, have to await long term clinical trials.