خيارات البحث
النتائج 2031 - 2040 من 4,044
Tributyltin (TBT) Tolerance of Indigenous and Non-indigenous Bacterial Species النص الكامل
2016
Abubakar, Abdussamad | Mustafa, Muskhazli B | Johari, Wan Lutfi Wan | Zulkifli, Syaizwan Zahmir | Yusuff, Ferdaus Binti Mohamat
Tributyltin (TBT) is a species of organotin compound (OTC), used as antifouling biocide in boat and ship paints to prevents the attachment of marine organism on their hull surfaces. Tributyltin was found to be very toxic to a variety of targeted and non-targeted organisms and has high persistence in sediments even after the total global ban by the International Maritime Organization (IMO) in 2008. Therefore, there is an urgent need to clean up TBT-polluted environments after the global banning due to the significant risks it poses to the human and aquatic organisms for its slow degradation rate. In selecting bioremediation agents, indigenous bacteria were documented to be of great potentials compared to non-indigenous. In this study, comparison was made between a bacterial isolate Klebsiella sp. FIRD 2, isolated from TBT-contaminated surface sediment and Pseudomonas specie isolated from non-TBT-contaminated soil. Previously, we isolated, screened, and identified Klebsiella sp. FIRD 2 as a TBT-resistant bacterium from TBT-contaminated surface sediment of Kong Kong Laut, Johor, Malaysia. The isolate was able to resist TBT up to 1500 μg/L without addition of carbon source in minimal salt medium (MSM). Pseudomonas sp., isolated from non-TBT-contaminated soil was tested in MSM treated with different concentration of TBT. The bacterium did not endure to survive in TBT-treated media without addition of carbon source; thus, the strain has no ability to utilize TBT as source carbon. Growth of Pseudomonas sp. was observed in MSM treated with TBT at concentration of 500 μg/L and 1000 μg/L along with addition of glucose as carbon source. No growth of Pseudomonas sp. was observed in MSM with higher TBT concentration even with additional of carbon source. This study equally endorses the potentials of indigenous bacteria in bioremediation of TBT contamination.
اظهر المزيد [+] اقل [-]Impact of Anions, Cations, and pH on Manganese Accumulation and Toxicity in the Green Alga Scenedesmus quadricauda النص الكامل
2016
Švec, Pavel | Kováčik, Jozef | Hedbavný, Josef | Babula, Petr | Rotková, Gabriela | Klejdus, Bořivoj
Accumulation of divalent manganese (Mn) and its toxicity in the green alga Scenedesmus quadricauda was studied at circumneutral pH (6.5). A comparison of two applied concentrations (10 or 100 μM) of MnCl₂, MnSO₄, and Mn(NO₃)₂ indicated that mainly sulfate evoked higher Mn accumulation. On the other hand, nitrate rather depleted antioxidative enzyme activities (APX, CAT, SOD), leading to an increase in ROS formation as proven by fluorescence microscopy. Subsequent experiments revealed that increase in pH (from 4.5 to 9.5) increased also Mn content but typically depleted amounts of reduced glutathione and phytochelatin 2. We also measured the size of particles formed from the manganese salts at pH 9.5. Competitive experiment between Ca/K salts (CaCl₂, CaSO₄, Ca(NO₃)₂, KCl, K₂SO₄, KNO₃) and Mn (as Mn sulfate) showed a negative relation between Ca and Mn amount but KNO₃ stimulated Mn accumulation. Microscopy revealed that mainly K salts elevated plasma membrane damage (Acridine orange staining). Data indicate that not only pH but also accompanying anion affects Mn accumulation and that Ca salts may affect Mn toxicity.
اظهر المزيد [+] اقل [-]Bacillus thuringiensis B1(2015b) is a Gram-Positive Bacteria Able to Degrade Naproxen and Ibuprofen النص الكامل
2016
Marchlewicz, Ariel | Domaradzka, Dorota | Guzik, Urszula | Wojcieszyńska, Danuta
A Gram-positive bacterium, designated as strain B1(2015b), was isolated from the soil of the chemical factory “Organika-Azot” in Jaworzno, Poland. On the basis of 16S rRNA gene sequence analysis, the isolated strain was classified as a Bacillus thuringiensis species. Strain B1(2015b) is able to degrade ibuprofen and naproxen, however, these compounds are not sufficient carbon sources for this strain. In the presence of glucose, Bacillus thuringiensis B1(2015b) degrades ibuprofen and naproxen with higher efficiency. Twenty milligrams per liter of ibuprofen was degraded within 6 days and 6 mg l⁻¹ of naproxen was removed within 35 days. Simultaneously, the growth of the bacterial culture was observed. The obtained results suggest that Bacillus thuringiensis B1(2015b) appears to be a powerful and useful tool in the bioremediation of non-steroidal anti-inflammatory drugs-contaminated environment.
اظهر المزيد [+] اقل [-]Mass Development of Diazotrophic Cyanobacteria (Nostocales) and Production of Neurotoxic Anatoxin-a in a Planktothrix (Oscillatoriales) Dominated Temperate Lake النص الكامل
2016
Toporowska, Magdalena | Pawlik-Skowrońska, Barbara | Kalinowska, Renata
In spite of extensive studies on multispecies toxigenic cyanobacterial blooms, they are still difficult to eliminate, and factors regulating their succession and toxin production remain still to discover. A 4-year study revealed periodical mass development of diazotrophic Nostocales such as Dolichospermum spp. (previously Anabaena), Aphanizomenon gracile and expansive Cuspidothrix (previously Aphanizomenon) issatschenkoi in a lake affected by perennial blooms of Planktothrix agardhii (Oscillatoriales). Compared to Oscillatoriales, Nostocales reached the highest total biomass (up to 16 mg L⁻¹) and contributed nearly 33–85 % to the total biomass of filamentous cyanobacteria at higher water temperatures (average values 17.5–22.6 °C) and higher ratio (11.8–14.1) of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN/DIP). Species structure of Nostocales changed considerably from year to year as indicated by the Jaccard similarity index (0.33–0.78). Concentrations of intracellular anatoxin-a (ANTX) ranged from 0.03 to 2.19 μg L⁻¹ of the lake water, whilst extracellular toxin reached up to 0.55 μg L⁻¹. The highest positive correlations were found between the intracellular ANTX and the biomass of Dolichospermum spp. (R ² = 0.73) and C. issatschenkoi (R ² = 0.43–0.65). Our study suggests that ANTX production by Dolichospermum depended mainly on water temperature, whereas that by C. issatschenkoi was related to water conductivity and DIN/DIP ratio. P-PO₄ concentrations also seemed to be important. The relatively short-term mass development of neurotoxic Nostocales is an additional threat to shallow, highly eutrophic water bodies continuously affected by Oscillatoriales blooms and may be controlled mainly by the DIN/DIP ratio. ANTX should be considered as a pollutant of freshwaters.
اظهر المزيد [+] اقل [-]Removal and Recovery of Cr(VI) from Industrial Plating Wastewater Using Fibrous Anion Exchanger النص الكامل
2016
Lee, Chang-Gu | Park, Jeong-Ann | Choi, Jae-Woo | Ko, Seok-Oh | Yi, Sang-hyŏp
The aim of this study was to investigate the removal and recovery of hexavalent chromium (Cr(VI)) from industrial plating wastewater using anion exchanger Kanecaron SA fibers in batch systems. The surface morphology and physicochemical properties of the fiber were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), and Fourier transform infrared spectroscopy (FT-IR). The removal efficiency was affected by the solution pH and showed a plateau formation decreasing on both sides of pH 4. The Cr(VI) uptake on Kanecaron SA fibers was rapidly increased in the first 10 min, and the kinetic data fit well to the Elovich model. Isotherm model analysis demonstrates that the Redlich-Peterson model suitably describes the equilibrium data, and the maximum adsorption capacity (Q ₘ) from the Langmuir model was 87.366 mg/g for Cr(VI) in distilled water, 117.977 mg/g for total Cr, and 57.101 mg/g for Cr(VI) in wastewater. Additionally, the Cr(III) contained in the plating wastewater was removed by the Kanecaron SA fibers, while the other heavy metals were not removed. Thermodynamic analysis indicates that Cr(VI) adsorption to Kanecaron SA fibers decreased with increasing temperature from 10 to 50 °C, indicating the spontaneous and exothermic nature of the sorption process. The removal efficiency was maintained above 80 % during four regeneration cycles.
اظهر المزيد [+] اقل [-]Respiratory Health Effects of Ultrafine Particles in Children: a Literature Review النص الكامل
2016
Heinzerling, Amy | Hsu, Joy | Yip, Fuyuen
By convention, airborne particles ≤0.1 μm (100 nm) are defined as ultrafine particles (UFPs). UFPs can comprise a large number of particles in particulate matter with aerodynamic diameters ≤2.5 μm (PM₂.₅). Despite the documented respiratory health effects of PM₂.₅ and concerns that UFPs might be more toxic than larger particular matter, the effects of UFPs on the respiratory system are not well-described. Even less is known about the respiratory health effects of UFPs among particularly vulnerable populations including children. We reviewed studies examining respiratory health effects of UFPs in children and identified 12 relevant articles. Most (8/12) studies measured UFP exposure using central ambient monitors, and we found substantial heterogeneity in UFP definitions and study designs. No long-term studies were identified. In single pollutant models, UFPs were associated with incident wheezing, current asthma, lower spirometric values, and asthma-related emergency department visits among children. Also, higher exhaled nitric oxide levels were positively correlated with UFP dose among children with asthma or allergy to house dust mites in one study. Multivariate models accounting for potential copollutant confounding yielded no statistically significant results. Although evidence for a relationship between UFPs and children’s respiratory is accumulating, the literature remains inconclusive. Interpretation of existing data is constrained by study heterogeneity, limited accounting for UFP spatial variation, and lack of significant findings from multipollutant models.
اظهر المزيد [+] اقل [-]A Review Study on Past 40 Years of Research on Effects of Tropospheric O3 on Belowground Structure, Functioning, and Processes of Trees: a Linkage with Potential Ecological Implications النص الكامل
2016
Agathokleous, Eugenios | Saitanis, Costas J. | Wang, Xiaona | Watanabe, Makoto | Koike, Takayoshi
Woody plants constitute a great sink of carbon storage, mitigating thus the greenhouse effect phenomenon. They are considered key players in ecosystems, and among others, they help in decreasing soil erosion and in maintaining soil moisture. Over the last decades, researches have shown negative effects of the ambient ozone (O₃) on many woody species, not only on canopy but also on belowground part of trees. Negative effects of elevated O₃ (eO₃), which usually refers to any O₃ dosages above the current ambient levels, on belowground structure, function, and processes may have consequences to ecosystem sustainability. We reviewed reports of research published over the past 40 years and dealing with woodies belowground response to eO₃. eO₃ induces changes in C dynamics into plants and alterations in their metabolism accordingly, as a result of different strategies followed by the trees in order to compensate with eO₃ stress effects. In these strategies, phenolics seem to have a detrimental role in shoot/root allometry. Root and soil chemical composition can be also influenced, threatening thus the soil biodiversity, soil fertility, and nutrient cycling. Elevated O₃ impact is discussed with linkage to other potential ecological consequences.
اظهر المزيد [+] اقل [-]Assessment of Trace Element Accumulation by Earthworms in an Orchard Soil Remediation Study Using Soil Amendments النص الكامل
2016
Centofanti, Tiziana | Chaney, Rufus L. | Beyer, W Nelson | McConnell, Laura L. | Davis, Allen P. | Jackson, Leigh Dana
This study assessed potential bioaccumulation of various trace elements in grasses and earthworms as a consequence of soil incorporation of organic amendments for in situ remediation of an orchard field soil contaminated with organochlorine and Pb pesticide residues. In this experiment, four organic amendments of differing total organic carbon content and quality (two types of composted manure, composted biosolids, and biochar) were added to a contaminated orchard field soil, planted with two types of grasses, and tested for their ability to reduce bioaccumulation of organochlorine pesticides and metals in earthworms. The experiment was carried out in 4-L soil microcosms in a controlled environment for 90 days. After 45 days of orchardgrass or perennial ryegrass growth, Lumbricus terrestris L. were introduced to the microcosms and exposed to the experimental soils for 45 days before the experiment was ended. Total trace element concentrations in the added organic amendments were below recommended safe levels and their phytoavailablity and earthworm availability remained low during a 90-day bioremediation study. At the end of the experiment, total tissue concentrations of Cu, Cd, Mn, Pb, and Zn in earthworms and grasses were below recommended safe levels. Total concentrations of Pb in test soil were similar to maximum background levels of Pb recorded in soils in the Eastern USA (100 mg kg⁻¹ d.w.) because of previous application of orchard pesticides. Addition of aged dairy manure compost and presence of grasses was effective in reducing the accumulation of soil-derived Pb in earthworms, thus reducing the risk of soil Pb entry into wildlife food chains.
اظهر المزيد [+] اقل [-]Crop residue management and fertilization effects on soil organic matter and associated biological properties النص الكامل
2016
Zhao, Bingzi | Zhang, Jiabao | Yu, Yueyue | Karlen, D. L. (Douglas L.) | Hao, Xiying
Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3 N fertilizer rates) were used. The CRM treatments were (1) R0: 100 % of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83 % of the N using mineral and 17 % manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450 kg N ha⁻¹ year⁻¹. At the end of the experiment, soil NO₃-N was reduced by 33 % from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44 % increase in occluded particulate organic C and N, and 80 °C extracted dissolved organic N, 19 to 32 % increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17 % of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.
اظهر المزيد [+] اقل [-]Impact of a long-term fire retardant (Fire Trol 931) on the leaching of Ca, Mg, and K from a Mediterranean forest loamy soil النص الكامل
2016
Michalopoulos, Charalampos | Koufopoulou, Sofia | Tzamtzis, Nikolaos | Pappa, Athina
The present laboratory study was conducted in pot soil taken from forest. The leaching of calcium (Ca), magnesium (Mg), and potassium (K) (plant macronutrients) due to the application of a nitrogen phosphate-based long-term fire retardant (LTFR) (Fire Trol 931) was investigated. The concentrations of Ca²⁺, Mg²⁺, and K⁺ were measured in the resulting leachates from pots with forest soil and pine tree alone and in combination with fire. Magnesium is a minor component of Fire Trol 931. The leaching of Ca²⁺, Mg²⁺, and K⁺ from treated soils with the retardant pots was significantly greater than that from control pots. The leaching of Mg²⁺ was found to be of small percentage of the initially applied Mg quantities. Fire Trol 931 application resulted in the leaching of Ca²⁺, Mg²⁺, and K⁺ from a typical Mediterranean forest soil in pots, following the application of simulated annual precipitation probably due to ammonium (one of the major retardant components) soil deposition that mobilizes base cations from the soil. It seems that LTFR application may result in chemical leaching from the soil to the drainage water.
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