PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Biodegradation, Environmental”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2005

Modulation of the genotoxicity of pesticides reacted with redox-modified smectite clay.

Pesticides are toxic agents intentionally released into the environment; their use raises public health and environmental concerns. In recent years there has been much attention to the biotic degradation of pesticides. Abiotic mechanisms in the soil can contribute to pesticide degradation yet the toxicological impact of such degradation is unclear. This study combines for the first time an investigation into abiotic mechanisms of degradation coupled with toxicological endpoints in mammalian cells. The genotoxicity of three commonly used agricultural pesticides was assessed before and after exposure to redox-modified clay minerals. The objectives of the study were to determine the genotoxicity of 2,4-dichlorophenoxy acetic acid (2,4-D), dicamba, and oxamyl, using single cell gel electrophoresis with Chinese hamster ovary (CHO) cells, and to determine the effect of the iron oxidation state in clay minerals (ferruginous smectite SWa-1) on the genotoxic potency of the pesticides. 2,4-D alone or following reaction with redox-modified clays did not induce DNA damage in CHO cells. Oxamyl alone induced a concentration-dependent increase in genomic DNA damage; however, its genotoxicity declined after reaction with reduced clay minerals. Dicamba was not genotoxic when directly analyzed. When dicamba was reacted with reduced clay, a concentration-dependent increase in genomic DNA damage was observed. This is the first reported case of a pesticide being converted into a genotoxin after exposure to redox-modified smectites. These data introduce a new paradigm on the interaction between redox-modified clays and pesticide-related environmental genotoxicity.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Environmental effects of the usage of avermectins in livestock.

Abamectin (avermectin B1) and ivermectin (22,23-dihydroavermectin B1) are high molecular weight hydrophobic compounds, active against a variety of animal parasites and insects. Numerous environmental fate and effects studies have been carried out in the development of these two compounds as antiparasitic agents and for abamectin as a crop protection chemical. They were found to be immobile in soil (Koc > or = 4000), rapidly photodegraded in water (degradation half-life (t1/2) in the summer 0.5 days or less) and as thin films on surfaces (t1/2 < 1 day), and aerobically degraded in soil (ivermectin in soil/feces mixtures (t1/2) = 7-14 days; avermectin B1a in soils, t1/2 = 2-8 weeks) to less bioactive compounds. Abamectin is not taken up from the soil by plants, nor is it bioconcentrated by fish (calculated steady-state bioconcentration factor of 52, with rapid depuration). Daphnia magna is the fresh water species found to be most sensitive to ivermectin and abamectin (LC50 values of 0.025 and 0.34 ppb respectively); fish (e.g. rainbow trout) are much less sensitive to these compounds (LC50 values of 3.0 ppb and 3.2 ppb, respectively). In the presence of sediment, toxicity toward Daphnia is significantly reduced. The metabolism and degradation of ivermectin and abamectin result in reduced toxicity to Daphnia. Abamectin and ivermectin possess no significant antibacterial and antifungal activity. They display little toxicity to earthworms (LC50 values of 315 ppm and 28 ppm in soil for ivermectin and abamectin, respectively) or avians (abamectin dietary LC50 values for bobwhite quail and mallard duck of 3102 ppm and 383 ppm, respectively), and no phytotoxicity. Residues of the avermectins in feces of livestock affect some dung-associated insects, especially their larval forms. This does not delay degradation of naturally formed cattle pats under field conditions; however, in some cases, delays have been observed with artificially formed pats. Based on usage patterns, the availability of residue-free dung and insect mobility, overall effects on dung-associated insects will be limited. As abamectin and ivermectin undergo rapid degradation in light and soil, and bind tightly to soil and sediment, they will not accumulate and will not undergo translocation in the environment, minimizing any environmental impact on non-target organisms resulting from their use.

Animals↗
PubMed2004

Potential remediation of waters contaminated with Cr(III), Cu, and Zn by sorption on the organic polymeric fraction of olive mill wastewater (polymerin) and its derivatives.

A study on the individual sorption of Cr(III), Cu, and Zn on polymerin, the humic-acid-like fraction of olive mill wastewater, and its derivatives, K-polymerin and an Fe(OH)x-polymerin complex, showed that these heavy metals were strongly sorbed on polymerin and K-polymerin in the order Cr(III) > Cu > Zn. The sorption on Fe(OH)x-polymerin was to a lower extent compared with that of the other two sorbents, but to a higher extent compared with ferrihydride [Fe(OH)x]. Combined atomic absorption spectrometry and diffuse reflectance infrared Fourier transform spectroscopy analyses showed that the selected heavy metals were individually sorbed on polymerin by means of a cation exchange mechanism, which was consistent with the replacement of Ca, Mg, K, and H bound to the carboxylate groups of the biosorbent and the concomitant chelation of the heavy metals by the OH groups of polymerin polysaccharide component. In binary combination and equimolar ratio, Cu was sorbed by polymerin more selectively than Zn. In ternary combination and equimolar ratio, Cr(III), Cu, and Zn were sorbed by polymerin in the order Cr(III) > Cu > Zn. The sorbing capacity of Zn and Cu was strongly influenced by Cr(III), whereas the sorbing capacity of Cr(III) was not affected bythe presence of the other two metals. The overall sorbing capacity of the binary and ternary mixtures of the three metals on polymerin proved to be considerable and much greater than that on Fe(OH)x-polymerin. Simulated wastewaters contaminated with Cu and Zn were purified after three sorption cycles by polymerin renewed at each cycle, whereas those containing a mixture of Cr(III), Cu, and Zn showed residues of Zn after five cycles. We briefly discuss environmental and industrial advantages for a possible exploitation of polymerin.

Adsorption↗
PubMed2005

Uptake and modeling of pesticides by roots and shoots of parrotfeather (Myriophyllum aquaticum).

INTENTION, GOAL, SCOPE, BACKGROUND: Aquatic plants have a great potential to function as in situ, on-site biosinks and biofilters of pollutants. They are used for phytoremediation and phytotoxicity studies. Pesticide uptake studies are very important to predict contaminant accumulation, translocation, and transformation. There are a lot of models which have been developed for emergent plants, but there are not any existing models for submerged aquatic plants for assessing pesticide uptake. OBJECTIVE: In this study, uptake of selected pesticides in parrotfeather (Myriophyllum aquaticum) were studied and the results were modeled with the aid of Log Kow and the concentration of pesticides. At the end, the developed model was compared to other existing models. METHODS: The test was conducted with parrotfeather as a model plant. The bioassay and cultivation of this plant were examined. Pesticide uptake by roots and shoots was determined using 14C-radiolabeled materials. RESULTS AND DISCUSSION: The results were fitted with an equation that showed a relationship between uptake and lipophilicity of pesticides. The model was compared with other pesticide uptake models developed for other plants. Atrazine and cycloxidim were taken up more by roots than by shoots in comparison to other pesticides used. The total uptake, both in shoots and roots, was lower than for terbutryn and trifluralin. The best appropriate model was developed from the results against the other models seen in the literature. The concentration factors (Root Concentration Factor (RCF) and Submerged Shoot Concentration Factor (SSCF)) increased with a higher Kow of the substances. The Submerged Shoot Concentration Factor (SSCF) revealed a better relationship of the chemicals than did the Root Concentration Factor (RCF). CONCLUSIONS: In this study, an uptake model was developed for rooted, submerged aquatic plants. Further studies are necessary to develop and compare models with different plants and pesticides. RECOMMENDATION AND OUTLOOK: Such studies as this one may be extended to other environmental pollutants in the aquatic ecosystem and may be employed to evaluate the possibility of using different plants in phytoremediation studies.

Atrazine↗
PubMed1998

Biotransformation of the major fungal metabolite 3,5-dichloro- p-anisyl alcohol under anaerobic conditions and its role in formation of Bis(3,5-dichloro-4-Hydroxyphenyl)methane.

Higher fungi have a widespread capacity for biosynthesis of organohalogens. Commonly occurring chloroaromatic fungal metabolites can end up in anaerobic microniches at the boundary of fungal colonies and wetland soils. The aim of this study was to investigate the environmental fate of a major fungal metabolite, 3, 5-dichloro-p-anisyl alcohol, under anaerobic conditions. This compound was incubated with methanogenic sludge to study its biotransformation reactions. Initially, 3,5-dichloro-p-anisyl alcohol was readily demethylated in stoichiometric quantities to 3, 5-dichloro-4-hydroxybenzyl alcohol. The demethylated product was converted further via two routes: a biotic route leading to the formation of 3,5-dichloro-4-hydroxybenzoate and 2,6-dichlorophenol, as well as an abiotic route leading to the formation of bis(3, 5-dichloro-4-hydroxyphenyl)methane. In the first route, the benzyl alcohol moiety on the aromatic ring was oxidized, giving 3, 5-dichloro-4-hydroxybenzoate as a transient or accumulating product, depending on the type of methanogenic sludge used. In sludge previously adapted to low-molecular-weight lignin from straw, a part of the 3,5-dichloro-4-hydroxybenzoate was decarboxylated, yielding detectable levels of 2,6-dichlorophenol. In the second route, 3, 5-dichloro-4-hydroxybenzyl alcohol dimerized, leading to the formation of a tetrachlorinated bisphenolic compound, which was identified as bis(3,5-dichloro-4-hydroxyphenyl)methane. Since formation of this dimer was also observed in incubations with autoclaved sludge spiked with 3,5-dichloro-4-hydroxybenzyl alcohol, it was concluded that its formation was due to an abiotic process. However, demethylation of the fungal metabolite by biological processes was a prerequisite for dimerization. The most probable reaction mechanism leading to the formation of the tetrachlorinated dimer in the absence of oxygen is presented, and the possible environmental implications of its natural occurrence are discussed.

Anaerobiosis↗
PubMed2003

Degradation of nonylphenol ethoxylates in estuarine sediment under aerobic and anaerobic conditions.

Nonylphenol ethoxylate (NPEO) surfactants and their metabolites are ubiquitous contaminants of the aquatic environment. Despite considerable interest in the environmental fate of these compounds due to concerns over toxicity and estrogenic activity, the pathways of NPEO degradation in sediments have not previously been reported, in spite of the fact that sediment appears to be an important sink for these compounds in the environment. In the present work, we have examined the rates and pathways of NPEO degradation in batch sediment slurry experiments using radiolabeled NPEO mixtures. Results suggest that NPEOs are more persistent in sediments under anaerobic conditions than in the presence of oxygen. In addition, it was illustrated that NPEO degradation proceeds via separate pathways in oxic and anoxic sediment. Discernible metabolites were identified and an overall mass balance for NPEO degradation in oxic and anoxic sediment was achieved. In contrast with previous studies, no evidence was observed for net production of nonylphenol from NPEOs during aerobic or anaerobic degradation. The observed relative rates at which NPEO ethoxymers disappeared in the sediment slurry experiments were consistent with previous reports for these compounds in sediment and other environmental media, although the absolute rates measured were somewhat faster than those reported for field sediments.

Aerobiosis↗
PubMed2004

Bacterial community profiles on feathers during composting as determined by terminal restriction fragment length polymorphism analysis of 16S rDNA genes.

Composting is one of the more economical and environmentally safe methods of recycling feather waste generated by the poultry industry, since 90% of the feather weight consists of crude keratin protein, and feathers contain 15% N. However, the keratin in waste feathers is resistant to biodegradation and may require the addition of bacterial inocula to enhance the degradation process during composting. Two keratin-degrading bacteria isolated from plumage of wild songbirds and identified as Bacillus licheneformis (OWU 1411T) and Streptomyces sp. (OWU 1441) were inoculated into poultry feather composts (1.13 x 10(8) cfu g(-1) feathers) and co-composted with poultry litter and straw in 200-l compost vessels. Composting temperatures, as well as CO(2) and NH(3) evolution, were measured in these vessels to determine the effects of inoculation on the rate and extent of poultry feather decomposition during composting. Terminal restriction fragment length polymorphisms of 16S rRNA genes were used to follow changes in microbial community structure during composting. The results indicated that extensive carbon conversion occurred in both treatments (55.5 and 56.1%). The addition of the bacterial inocula did not enhance the rate of waste feather composting. The microbial community structure over time was very similar in inoculated and uninoculated waste feather composts.

Ammonia↗
PubMed2004

Unhairing effluents treated by an activated sludge system.

Leather tannery effluents are a source of severe environmental impacts. In particular, the unhairing stage, belonging to beamhouse processes, generates a significantly toxic, alkaline wastewater with high concentrations of organic matter, sulphides, suspended solids and salts. The objective of this work was to evaluate the biodegradability and toxicity of diluted unhairing wastewater after being treated by an activated sludge (AS) system. The biomass activity of the AS was also evaluated. The AS system was fed for 180 days with diluted unhairing effluent. The operation strategy increased the organic load rate (OLR) from 0.23 to 2.98 g COD/l per day while the HRT was variable until operation day 113, when the HRT was near 1.1 days. Results show that when the organic load rate was lower than 2 g COD/l per day, the biological oxygen demand (BOD5) efficiency was 99%, whereas the chemical oxygen demand (COD) was around 80%. The reactor operation was stable until 2 g COD/l per day. For higher values, the system was less efficient (COD and BOD5 removal rate lower than 40%) and the relation of food/micro-organisms (F/M) was higher than 0.15. Biomass evaluations through oxygen utilisation coefficients show that the specific oxygen uptake rate (SOUR) decreased from 1.11 to 0.083 g O2/g MLVSS per day, in the same way the endogenous oxygen coefficient decreased from 0.77 to 0.058 per day. The reduction of biomass activity (measured as oxygen respiration) could be attributable to the inorganic compound content (ammonia and chloride) in the unhairing effluent. Also, the bioassays with Daphnia magna and Daphnia pulex showed that with these compounds, only between 24 and 31% of the toxicity of the aerobic-treated effluent can be removed. On the other hand, ultrafiltration (UF) analysis indicated that a COD fraction is recalcitrant to the aerobic treatment, principally those above 10,000 Da (around 55% of total unhairing influent COD).

Biodegradation, Environmental↗
PubMed1994

Dehalogenation in environmental biotechnology.

During the past year, the field of dehalogenation has seen rapid progress in the identification of novel organisms, the sequencing of new genes, and the delineation of mechanisms for important enzymes. Newly identified anaerobic organisms are beginning to offer insights into a previously obscure, but important, group of bacteria involved in environmental dehalogenation. An important series of X-ray structure determinations have provided key knowledge for understanding and, ultimately, engineering biodehalogenation catalysis.

Biodegradation, Environmental↗
PubMed2004

Horizontal gene transfer and microbial adaptation to xenobiotics: new types of mobile genetic elements and lessons from ecological studies.

The characterization of bacteria that degrade organic xenobiotics has revealed that they can adapt to these compounds by expressing 'novel' catabolic pathways. At least some of them appear to have evolved by patchwork assembly of horizontally transmitted genes and subsequent mutations and gene rearrangements. Recent studies have revealed the existence of new types of xenobiotic catabolic mobile genetic elements, such as catabolic genomic islands, which integrate into the chromosome after transfer. The significance of horizontal gene transfer and patchwork assembly for bacterial adaptation to pollutants under real environmental conditions remains uncertain, but recent publications suggest that these processes do occur in a polluted environment.

Adaptation, Physiological↗
PubMed2002

Recovery from acidification in central Europe--observed and predicted changes of soil and streamwater chemistry in the Lysina catchment, Czech Republic.

The geochemical model MAGIC was applied to estimate streamwater and soil chemistry between 1851 and 2030 at the Lysina catchment, an acid-sensitive granitic catchment covered by planted Norway spruce monoculture in the western Czech Republic. The total deposition of sulfur to the catchment was 164 meq m(-2) in 1991, but had declined to 52 meq m(-2) by 2000. Although SO2 emissions in the region declined by 90% compared to the 1980s, acidification recovery was small within the period 1990-2000. Stream pH increased only slightly (from 3.92 to 4.07), although SO4 concentration declined sharply from 568 microeq l(-1) (1990) to 232 microeq l(-1) (2000). Organic acids played an important role in streamwater buffering. According to the MAGIC prediction using deposition measured in 1999-2000, streamwater pH will increase to 4.3 and soil base saturation will increase to 6.2% by 2030 (from 5.7% in 2002). Pre-industrial pH was estimated to be 5.5 and soil base saturation 24.7%. The loss of base cations (Ca, Mg, Na, K) was caused predominantly by atmospheric acidity, but intensive forestry was responsible for approximately one third of the net base cation loss via accumulation in harvested biomass. Severely damaged sites, under continued pressure from forestry, will not return to a good environmental status in the near future (if ever) when the acid deposition input is only partially reduced.

Acid Rain↗
PubMed2000

Anaerobic utilization of essential oils by denitrifying bacteria.

Plant volatile organic compounds are a major carbon source in nature. We studied the degradability of these substances by anaerobic microorganisms in enrichment cultures with representative essential oils as organic substrates and nitrate as electron acceptor. Lemon and pine needle oil supported microbial growth in the presence of pure oil, whereas parsley seed, camphor, sage, fennel, and mint oil supported growth only when the essential oils were dissolved in an overlying phase of 2,2,4,4,6,8,8-heptamethylnonane. Thyme oil did not support denitrification. Analyses of the microbially degraded oils revealed the disappearance of monoterpenes, of several monoterpenoids, and of methoxy-propenyl-benzenes, including apiole and myristicin. Most-probable-number determinations for denitrifying communities in sewage sludge and forest soil yielded 10(6) to 10(7) monoterpene-utilizing cells ml(-1), representing 0.7 to 100% of the total cultivable nitrate-reducing microorganisms. The utilization of essential oils together with the common occurrence of this metabolic trait are indications for an environmentally important, but currently unexplored anaerobic turnover of plant volatile organic compounds in soil.

Alcaligenes↗
PubMed1997

Designing recombinant Pseudomonas strains to enhance biodesulfurization.

The dsz biodesulfurization cluster from Rhodococcus erythropolis IGTS8 has been engineered under the control of heterologous broad-host-range regulatory signals to alleviate the mechanism of sulfur repression, and it was stably inserted into the chromosomes of different Pseudomonas strains. The recombinant bacteria were able to desulfurize dibenzothiophene more efficiently than the native host. Furthermore, these new biocatalysts combine relevant industrial and environmental traits, such as production of biosurfactants, with the enhanced biodesulfurization phenotype.

Biodegradation, Environmental↗
PubMed2003

Assessment of the environmental impact of management measures for the biodegradable fraction of municipal solid waste in São Paulo City.

There is increasing concern about landfilling of biodegradable wastes. Therefore, biological treatment processes such as composting and biogasification have been considered as alternative strategies for managing those wastes. In this work, life cycle assessment was employed to compare the environmental impacts of landfilling, composting, and biological treatment of municipal solid waste in São Paulo City, Brazil. Energy consumption, recovered resources, and emissions to air and water were quantified and analyzed in terms of their potential contribution to global warming, acidification, and nutrient enrichment impact. The results demonstrated that processes that require high levels of energy consumption, such as wastewater treatment, play an important role in the outcome of environmental impact potentials. It was found that the landfilling of all waste is generally the worst strategy from an environmental point of view. However, significant reductions in the resulting impacts can be accomplished through biogasification and composting of the biodegradable fraction. Regarding composting, the application of a biofilter for gas treatment reduced significantly the gaseous emissions.

Biodegradation, Environmental↗