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1.
Sci Total Environ ; 746: 141134, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32768780

RESUMO

Pharmaceuticals may enter soils due to the application of treated wastewater or biosolids. Their leakage from soils towards the groundwater, and their uptake by plants is largely controlled by sorption and degradation of those compounds in soils. Standard laboratory batch degradation and sorption experiments were performed using soil samples obtained from the top horizons of seven different soil types and 6 pharmaceuticals (carbamazepine, irbesartan, fexofenadine, clindamycin and sulfamethoxazole), which were applied either as single-solute solutions or as mixtures (not for sorption). The highest dissipation half-lives were observed for citalopram (average DT50,S for a single compound of 152 ±â€¯53.5 days) followed by carbamazepine (106.0 ±â€¯17.5 days), irbesartan (24.4 ±â€¯3.5 days), fexofenadine (23.5 ±â€¯20.9 days), clindamycin (10.8 ±â€¯4.2 days) and sulfamethoxazole (9.6 ±â€¯2.0 days). The simultaneous application of all compounds increased the half-lives (DT50,M) of all compounds (particularly carbamazepine, citalopram, fexofenadine and irbesartan), which is likely explained by the negative impact of antibiotics (sulfamethoxazole and clindamycin) on soil microbial community. However, this trend was not consistent in all soils. In several cases, the DT50,S values were even higher than the DT50,M values. Principal component analyses showed that while knowledge of basic soil properties determines grouping of soils according sorption behavior, knowledge of the microbial community structure could be used to group soils according to the dissipation behavior of tested compounds in these soils. The derived multiple linear regression models for estimating dissipation half-lives (DT50,S) for citalopram, clindamycin, fexofenadine, irbesartan and sulfamethoxazole always included at least one microbial factor (either amount of phosphorus in microbial biomass or microbial biomarkers derived from phospholipid fatty acids) that deceased half-lives (i.e., enhanced dissipations). Equations for citalopram, clindamycin, fexofenadine and sulfamethoxazole included the Freundlich sorption coefficient, which likely increased half-lives (i.e., prolonged dissipations).


Assuntos
Microbiota , Poluentes do Solo/análise , Adsorção , Solo , Sulfametoxazol , Águas Residuárias/análise
2.
Sci Total Environ ; 569-570: 1457-1465, 2016 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-27432728

RESUMO

Phenoxy acid-contaminated subsoils are common as a result of irregular disposal of residues and production wastes in the past. For enhancing in situ biodegradation at reducing conditions, biostimulation may be an effective option. Some phenoxy acids were marketed in racemic mixtures, and biodegradation rates may differ between enantiomers. Therefore, enantio-preferred degradation of mecoprop (MCPP) in soil was measured to get in-depth information on whether amendment with glucose (BOD equivalents as substrate for microbial growth) and nitrate (redox equivalents for oxidation) can stimulate bioremediation. The degradation processes were studied in soil sampled at different depths (3, 4.5 and 6m) at a Danish urban site with a history of phenoxy acid contamination. We observed preferential degradation of the R-enantiomer only under aerobic conditions in the soil samples from 3- and 6-m depth at environmentally relevant (nM) MCPP concentrations: enantiomer fraction (EF)<0.5. On the other hand, we observed preferential degradation of the S-enantiomer in all samples and treatments at elevated (µM) MCPP concentrations: EF>0.5. Three different microbial communities were discriminated by enantioselective degradation of MCPP: 1) aerobic microorganisms with little enantioselectivity, 2) aerobic microorganisms with R-selectivity and 3) anaerobic denitrifying organisms with S-selectivity. Glucose-amendment did not enhance MCPP degradation, while nitrate amendment enhanced the degradation of high concentrations of the herbicide.


Assuntos
Ácido 2-Metil-4-clorofenoxiacético/análogos & derivados , Carbono/metabolismo , Recuperação e Remediação Ambiental/métodos , Herbicidas/metabolismo , Nitratos/metabolismo , Poluentes do Solo/metabolismo , Ácido 2-Metil-4-clorofenoxiacético/metabolismo , Anaerobiose , Biodegradação Ambiental , Oxirredução
3.
Appl Microbiol Biotechnol ; 98(5): 2335-44, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24562459

RESUMO

The Aminobacter sp. strain MSH1 has potential for pesticide bioremediation because it degrades the herbicide metabolite 2,6-dichlorobenzamide (BAM). Production of the BAM-degrading bacterium using aerobic bioreactor fermentation was investigated. A mineral salt medium limited for carbon and with an element composition similar to the strain was generated. The optimal pH and temperature for strain growth were determined using shaker flasks and verified in bioreactors. Glucose, fructose, and glycerol were suitable carbon sources for MSH1 (µ = 0.1 h(-1)); slower growth was observed on succinate and acetic acid (µ = 0.01 h(-1)). Standard conditions for growth of the MSH1 strain were defined at pH 7 and 25 °C, with glucose as the carbon source. In bioreactors (1 and 5 L), the specific growth rate of MSH1 increased from µ = 0.1 h(-1) on traditional mineral salt medium to µ = 0.18 h(-1) on the optimized mineral salt medium. The biomass yield under standard conditions was 0.47 g dry weight biomass/g glucose consumed. An investigation of the catabolic capacity of MSH1 cells harvested in exponential and stationary growth phases showed a degradation activity per cell of about 3 × 10(-9) µg BAM h(-1). Thus, fast, efficient, large-scale production of herbicide-degrading Aminobacter was possible, bringing the use of this bacterium in bioaugmentation field remediation closer to reality.


Assuntos
Reatores Biológicos/microbiologia , Phyllobacteriaceae/crescimento & desenvolvimento , Benzamidas/metabolismo , Biomassa , Biotransformação , Carbono/metabolismo , Meios de Cultura/química , Poluentes Ambientais/metabolismo , Herbicidas/metabolismo , Concentração de Íons de Hidrogênio , Phyllobacteriaceae/metabolismo , Temperatura
4.
Pest Manag Sci ; 70(8): 1291-8, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24302680

RESUMO

BACKGROUND: The herbicide dichlobenil was banned in the European Union after its metabolite 2,6-dichlorobenzamide (BAM) was encountered in groundwater. Owing to structural similarities, bromoxynil and ioxynil might be converted to persistent metabolites in a similar manner. To examine this, we used an indigenous soil bacterium Aminobacter sp. MSH1 which is capable of mineralizing dichlobenil via BAM and 2,6-dichlorobenzoic acid (2,6-DCBA). RESULTS: Strain MSH1 converted bromoxynil and ioxynil to the corresponding aromatic metabolites, 3,5-dibromo-4-hydroxybenzoic acid (BrAC) and 3,5-diiodo-4-hydroxybenzoic acid (IAC) following Michaelis-Menten kinetics (adjusted R(2) between 0.907 and 0.999). However, in contrast to 2,6-DCBA, degradation of these metabolites was not detected in the pure-culture studies, suggesting that they might pose an environmental risk if similar partial degradation occurred in soil. By contrast, experiments with natural soils indicated 20-30% mineralization of ioxynil and bromoxynil within the first week. CONCLUSION: The degradation pathway of the three benzonitriles is initially driven by similar enzymes, after which more specific enzymes are responsible for further degradation. Ioxynil and bromoxynil mineralization in soil is not dependent on previous benzonitrile exposure. The accumulation of dead-end metabolites, as seen for dichlobenil, is not a major problem.


Assuntos
Herbicidas/metabolismo , Nitrilos/metabolismo , Phyllobacteriaceae/metabolismo , Microbiologia do Solo , Biodegradação Ambiental , Iodobenzenos/metabolismo , Cinética
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