Non-biological Degradation Research Articles

Kinetics and mechanism insights into the photodegradation of tetracycline hydrochloride and ofloxacin mixed antibiotics with the flower-like BiOCl/TiO2 heterojunction

Antibiotic pollutants have been constantly detected in the water environment. Photocatalytic degradation of antibiotics is one of the important ways of non-biological degradation. Due to the diversity and complexity of antibiotics, it is of great significance to study the interaction and degradation pathways of mixed antibiotics. In this paper, particular emphasis was given to the kinetics and mechanism of mixed antibiotics (tetracycline hydrochloride and ofloxacin) at different pH values and concentration ratio by using the flowerlike BiOCl/TiO2 as photocatalyst. The results showed that there was a tendency of selective degradation in the degradation process of the mixed antibiotics: TC (tetracycline hydrochloride) was preferentially degraded under alkaline conditions. This may be the ionization degree of TC is stronger than that of OFLX (ofloxacin) under alkaline conditions, generating more ionic state of TC, which are easily oxidized by OH. And, because of the difference in ionization intensity, the initial concentration of OFLX in mixtures ranged from 0 to 0.2 improved the degradation rate of TC from 0.1208 min−1 to 0.2932 min−1. Moreover, the degradation intermediates of antibiotics were analyzed by HPLC-MS and the degradation mechanism was obtained. It indicated that the main pathways of degradation did not affect each other in mixed antibiotics system. And the intermediates facilitated the development of C. vulgaris. This paper provides a useful reference for the study and degradation of water environmental systems containing various organic pollution.

Fate of famoxadone in the environment

The fate of famoxadone [Famoxate®, 3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione] in the aquatic and soil environment was examined. It was found to be relatively stable at pH 5, but hydrolysed rapidly in pH 7 and 9 buffer solutions. Primary hydrolytic degradation reactions included the opening of the oxazolidinedione ring and the cleavage of the oxazolidinedione-aminophenyl linkage. The compound degraded rapidly in soil by both hydrolytic and microbial action. In addition to the generation of [ 14 C] carbon dioxide and unextractable bound residues, hydroxylation and hydrolysis reactions occurred to yield multiple degradation products. Nitration of famoxadone at the 2- or 4-phenylamino position was observed as a novel non-biological degradation reaction of famoxadone in soil. Degradation in aqueous solution (pH 5) and on soil surfaces was accelerated under simulated sunlight irradiation. Famoxadone exhibited negligible soil mobility potential, and its primary degradation products were also shown to dissipate rapidly in the environment.

The influence of processing induced differences in molecular structure on the biological and non-biological degradation of poly (3-hydroxybutyrate-co-3-hydroxyvalerate), P(3-HB-co-3-HV)

The influence of processing conditions on the degradation rate of melt-extruded poly(3-hydroxybutyrate-co-7%3-hydroxyvalerate) in pure fungal cultures ( Phanerochaete chrysosporium, Penicillium simplicissimum and Aspergillus fumigatus) and by chemical hydrolysis (pH 10.5, 60°C) was investigated. The degradation was monitored by gravimetry, size exclusion chromatography (SEC), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray scattering, infrared spectroscopy (FTIR) and tensile testing. The rate of erosion, measured as weight loss, was highest for the samples processed at high temperature, and lowest for the samples processed at the lowest temperature. The erosion rate during microbial degradation was not controlled by molecular weight or by the lamellar distribution. An increase in the degree of crystallinity reduced the rate of erosion. A correlation was found between the rate of erosion and the intensities of the sharp X-ray reflections (020) and (110). The rate of weight loss increased with increasing peak ratio I (020)/I (110) indicating that the positioning of the oxygen atoms affected the recognition capability of the extra-cellular enzymes. The reproducibility in weight loss of the samples between the different experiments was good. The erosion proceeded without any decrease in molecular weight. The molecular weight of the samples subjected to chemical hydrolysis exhibited a 50% drop within 40 days. Microtomed samples showed higher rates of chain scission in the center than at the surface. The degree of crystallinity increased by 35% as measured by DSC. The initial appearance of the melting endotherm, governed by the processing conditions, was maintained at 60°C until the molecular weight dropped below 50% of the initial value. The embrittlement of the samples measured as the elongation at break (ε b) was controlled by the decrease in molecular weight.

Degradation of a Fungicide, Mepanipyrim, in Soils

メパニピリムのピリミジン環4位またはベンゼン環を14Cで標識した化合物を用い, 土壌中での分解を室内試験で調べた. 2種類の土壌にメパニピリムを0.4ppmの割合で添加し畑条件で培養すると, その半減期は2週間から3ヵ月間であった. 主な分解経路はN-脱フェニル化であり, 他にプロピニル基やベンゼン環が水酸化をうけ, 生成した分解物はさらに14CO2まで分解したり bound 14Cを形成した. 湛水条件では, 畑条件に比べ分解が速く, また, bound 14Cも多かった. 湛水条件ではプロピニル基が種々の変換をうけることが主な分解経路であった. 滅菌土壌において、畑条件ではメパニピリムがほとんど分解しなかったことから分解には主に微生物の関与が, また、湛水条件では緩やかに分解したことから非生物的分解も関与することが示唆された.

A comparison of two radiometric methods to investigate the biodegradation of phenol by Candida nitrativorans

Traditional radiometric methods use internal CO 2 collectors to follow the degradation process of a radiolabeled compound by the release of 14CO 2 in an essentially closed system that is opened repeatedly for sampling. Our aim was to investigate the biodegradation of phenol by C. nitrativorans using radiolabeled phenol in internal and external collection systems. Using the internal system, the loss of activity from the control vessel was approximately 26% and in the experimental vessel, losses reached 57%. We attribute these losses to phenol volatilization (control) and volatile products from degradation (experimental vessel), during the sampling process. An external collector system using forced air flow, was devised that allowed the collection of the 14CO 2 produced in a series of three external collectors. The losses observed using this system were greatly reduced, 32% in the experimental vessel, with the uninoculated control accounting for 25%. Therefore, only 7% of the initial activity was lost or unaccounted for. It was also shown that the activity collected from the control vessel was not due to non-biological degradation of the phenol producing CO 2, but rather to the volatilization of the phenol. Comparing the two methods, it was noted that the external collection system recovered more of the total initial activity than did the internal system and less activity was detected in the control flask, indicating lower losses through volatilization of the phenol substrate. Extrapolating the data from the control in the external system after precipitation with BaCl 2, we would suggest that the activity in the internal collector system control was due to the capture of phenol and not to the capture of CO 2. Based on these data, we would recommend the use of the external collection system for radiorespirometric measurement of an aerobic degradation process, using a substrate which is sensitive to the disruption of the gas/liquid phase equilibrium.

Evidence for rapid, nonbiological degradation of tributyltin compounds in autoclaved and heat-treated fine-grained sediments

Sterilized sediments, high in silt and clay content, from various sites in the United States rapidly degraded added 14 C-labeled tributyltin (TBTX) or unlabeled TBTX to dibutyltin (DBTC 2 ), monobutyltin (MBTX 3 ), and inorganic tin. This degradation was primarily abiotic, as documented by similar degradation rates between sterilized and nonsterilized sediment. Degradation occurred in two phases, with a rapid degradation phase (23-94%) after 2 days, followed by slower degradation rates of the remaining TBTX during the next 5-7 days

Non-biological degradation of oxamide adsorbed on homoionic montmorillonite

Non-biological degradation of oxamide, adsorbed on Cu− 2+, Al− 3+ and Ca− 2+ homoionic montmorillonite was investigated by HPLC, IR spectrometry and chemical analyses. Self-supporting films of homoionic montmorillonites were subjected to a number of wetting and drying cycles. The oxamide recovered as well as its degradation products, such as oxalic acid, oxamic acid and NH 4 + were determined in the water extracts, after different number of cycles. The films were previously analyzed by FT-IR in order to find the functional groups involved in the adsorption mechanisms, and the degradation processes. Depending on the nature of the clay exchange cation, oxamide was found to be decomposed on all homoionic clay systems to a different extent and through different mechanisms. Cu− 2+ montmorillonite was very effective in degrading oxamide, mainly by the formation of complexes between the N-H groups and Copper. These complexes are easily hydrolizable in water solution and therefore undetected by HPLC. On Al− 3+ montmorillonite the CO functional group of adsorbed oxamide is protonated and the molecule is degraded to carbamic acid, stable on the dry clay surface, but decomposed to CO 2 and NH 3 at high moisture levels. Ca− 2+ montmorillonite was the less effective in degrading oxamide, and significant amounts of stable intermediate compounds, such as oxamic and oxalic acid were progressively formed during the wetting and drying cycles.

Hydrolysis and Free Radial Mediated Degradation of Phosphonates

AbstractWhile studying the biodegradation and environmental fate of phosphonates, two almost undocumented nonbiological degradation processes acting on the stable C‐P bond were observed. Under test conditions comparable to the environmental situation, phosphonates in solution are prone to a slow light‐independent hydrolytic cleavage of the C‐P bond(s). The process requires divalent cations, aerobic conditions, and is particularly active on N‐containing phosphonates. Highest hydrolysis rates, up to 1% phosphonate‐P converted to inorganic phosphate per day, were measured with the polyphosphonates. Second, C‐P bonds in all phosphonates can efficiently be cleaved, also with release of orthophosphate, by means of physicochemically generated free radicals. The riboflavin/light and Cu2+/H2O2 systems were more efficient than the Fenton reagent (Fe2+/H2O2) in this respect. Both processes are likely to contribute to the removal of xenobiotic phosphonates in the environment, particularly in the absence of photo‐ and biodegradation.

Ultrastructural characterization of wood from Tertiary fossil forests in the Canadian Arctic

Micromorphological and ultrastructural characterization of fossil gymnosperm wood from Comwallis Island, Axel Heiberg Island, and Ellesmere Island in the Canadian High Arctic showed the changes that have occurred in cell walls of wood during 20–60 million years of burial. No evidence of permineralization was observed. Wood with rounded cells, thick secondary walls, and intercellular spaces was common in all samples. Secondary walls were eroded and swollen. A transition from an organized secondary wall, with altered but visible microfibrillar structure, to an electron-dense, amorphous material was evident in cell walls. The amorphous material appeared to form primarily in the secondary walls near cell lumina and along cracks that extended into the walls. The middle lamellae were often expanded in size and had convoluted shapes. Hemicellulose degradation appeared to precede cellulose degradation. Samples exhibiting cell walls with increased amorphous material had the greatest lignin and lowest cellulose concentrations. Hemicellulose concentration was extremely low in all Eocene and Paleocene samples. The lignin content of Miocene wood was 47.9%, whereas the Eocene and Paleocene samples ranged from 66 to 84%. Tracheids from extensively degraded samples were distorted and collapsed, and in some cases the cells appeared compressed together. Although the residual amorphous middle lamellae and secondary walls were fused together, the outlines of original cells were visible. Chemical analyses and ultrastructural data indicated that a nonbiological degradation was responsible for the deterioration of the arctic fossil wood samples. Key words: wood deterioration, lignin, hemicelluloses, cellulose, wood ultrastructure, coal formation, fossil wood.

Microbial and non-biological decomposition of chlorophenols and phenol in soil

The aerobic and anaerobic degradation of phenol and selected chlorophenols was examined in a clay loam soil containing no added nutrients. A simple, efficient procedure based on the high solubility of these compounds in 95% ethanol was developed for extracting phenol and chlorophenol residues from soil. Analysis of soil extracts with UV spectrophotometry showed that phenol,o-chlorophenol,p-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol were rapidly degraded, whilem-chlorophenol, 3,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol were degraded very slowly by microorganisms in aerobically-incubated soil at 23°C. Both 3,4,5-trichlorophenol and 2,3,4,5-tetra chlorophenol appeared to be more resistant to degradation by aerobic soil microorganisms at 23°C. None of the compounds examined were degraded by microorganisms in anaerobically-incubated soil at 23°C. Direct microscopic observation revealed that phenol and selected chlorophenols stimulated aerobic and to a lesser extent, anaerobic microbial growth in soil, and aerobic soil bacteria were responsible for the degradation of 2,4-dichlorophenol in aerobically-incubated soil at 23°C. Phenol,o-chlorophenol,m-chlorophenol,p-chlorophenol and 2,4-dichlorophenol underwent rapid non-biological degradation in sterile silica sand. Non-biological decomposition contributed, perhaps substantially, to the removal of some chlorophenols from sterile aerobically-incubated soil and both sterile and non-sterile anaerobically-incubated soil.

Determining the role of human substances in the fate of pesticides in the environment.

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV-radiation, are described. Finally, the photochemical stability to UV-radiation of certain pesticides in aqueous fulvic acid solution is discussed.

Nonbiological degradation of the herbicide metribuzin in Manitoba soils.

Degradative loss of herbicides in soil can take place by chemical or biological means. HYZAK and ZIMDAHL (1972) bave suggested that non-biological degradation of metribuzin in soil may be the most important mode of breakdown following application to San Luis sandy loam. Later work by HYZAK and ZIMDAHL (1974) suggests that degradatlon of metribuzin in soil is an approximately first order phenomenon at 5 ~ 20 ~ and 35~ yielding a linear plot of log (residual metribuzin) vs time. Their results show no induction period following application of metribuzin. Several variables have been suggested to influence metribuzin persistence in Canadian prairie soils; e.g., temperature, organic matter content, and adsorption properties of soils. HYZAK and ZIMDAHL (1974) show that degradation of metribuzin in soil increases with temperature, and increased degradation in the field in Almasippi very fine sandy loam has been shown by WEBSTER and REIMER (1976a) to correspond to temperature increases in the soil. The latter two variables, however, are characteristics of specific soil types, and attention was turned in this study to an evaluation of the ~fluence of four Manitoba soils on non-biological degradation of metribuzin.

Formation of 3,3',4,4'-tetrachloroazobenzene from 3,4-dichloroaniline in Ontario soils.

The formation of 3,3′,4,4′-tetrachloroazobenzene (TCAB) from 3,4-dichloroaniline (3,4-DCA) was studied using four Ontario soils. The disappearance of 3,4-DCA from Guelph loam was primarily due to chemical mechanisms under anaerobic and water-saturated conditions, while under aerobic and water-unsaturated conditions about 25% of the loss could be attributed to microbial activity. Only a small percentage of the disappearance of measurable 3,4-DCA was associated with TCAB formation. TCAB was formed in varying amounts in the limited number of soils examined. None was formed in a Peel clay. The optimum soil temperature for formation of TCAB was 25 °C, and the optimum concentration of 3,4-DCA required was found to be 500 μg/g of soil. Maximum conversion of 3,4-DCA to TCAB was 4.8% at optimal conditions. In soil shown to have an Eh of about −300 mV, TCAB formation was strikingly reduced. TCAB formed in low concentrations in Guelph loam disappeared with continued incubation, and evidence is presented for non-biological degradation of this condensed molecule.

Behavior of Pyrazon in Soil

The disappearance of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) from soil was studied using Brassica species for bioassay and the spectrophotometer and chromogenic reagents for chemical determination. Loss of pyrazon from soil appeared to be an exponential function of time characteristic of the activity of soil microorganisms. On the other hand, non-biological degradation appeared negligible. Leaching of pyrazon appeared to be insignificant or minor. The greater part of the herbicide remained in the top 3 inches of soil.

Persistence of diazinon and zinophos in soil: effects of autoclaving, temperature, moisture, and acidity.

The persistence of diazinon and Zinophos® ( O, O -diethyl O -2-pyrazinyl phosphorothioate) was determined in autoclaved and nonautoclaved Sultan silt loam at 3 temperatures (15, 25, and 35°C), 4 soil-moisture levels (2, 10,20, and 30%), and 4 p H levels (4.3, 5.5, 7.0, and 8.0). Insecticide residues were extracted with a 2:1 mixture of hexane and acetone and measured by gas chromatography. Degradation rates for diazinon were similar in autoclaved and nonautoclaved soil, while Zinophos degraded faster in nonautoclaved soil than in autoclaved soil. Higher temperatures and soil moisture levels accelerated decomposition of both insecticides. Increasing soil acidity accelerated the nonbiological degradation of diazinon. Zinophos was most persistent at p H 5.5 and least persistent in neutral and alkaline soils. Soil p H had no effect upon the nonbiological decomposition of Zinophos but neutral and alkaline soils apparently provided a suitable environment for microorganisms which metabolized the insecticide. Acidophilic microorganisms may have contributed to the degradation of Zinophos at p H 4.3.