خيارات البحث
النتائج 2521 - 2530 من 3,208
Modern climate and vegetation variability recorded in organic compounds and carbon isotopic compositions in the Dianchi watershed النص الكامل
2015
Xu, Meina | Wang, Yanhua | Yang, Hao | Xie, Biao | Niu, Xiaoyin
The aliphatic hydrocarbons distribution and compound-specific characteristics of carbon isotopic compositions in the sediments from the small catchment (197 km²) of the Dianchi watershed were investigated for identification of modern climate and vegetation variations in the study area. Results show that a regular bimodal n-alkanes distribution ranged from nC₁₆ to nC₃₃, with strong dominance at nC₁₇ for short-chain n-alkanes and nC₃₁ for long-chain n-alkanes. Mass chromatogram of total fatty acids also indicates corresponding mixed contribution of algae, hydrophilous non-emergent (C₄ plants) and terrestrial plants (C₃ plants) to sedimentary organic matter (OM). At the depth of −24 to −25 cm (early 1970s), nC₃₁/nC₁₇ and terrestrial to aquatic ratio of hydrocarbons (TAR) values decrease, suggesting a shift of OM origins from C₃ terrestrial plants to algae-derived C₄ plants. The highest water stage in 1971 was found to be recorded in the particle size (<4 μm). For long-chain alkanes, the values of δ ¹³Cₒᵣg and δ ¹³C ₙ₋ₐₗₖₐₙₑₛ varied from −26.9 to −22.4 and −33.4 to −27.9 ‰, respectively. Population growth and economic development led to a demand for abundant habitable and cultivable land. Due to unreasonable land expansion, the primordial forest sporadically distributed. A mixture of C₃ and C₄ plants probably replaced C₃ plants as the sources of OM in the past 10 years. The changes of land-use types and severe drought resulted in the excessive OM inputs to the watershed.
اظهر المزيد [+] اقل [-]The effectiveness of various treatments in changing the nutrient status and bioavailability of risk elements in multi-element contaminated soil النص الكامل
2015
García Sánchez, Mercedes | García-Romera, Inmaculada | Száková, Jiřina | Kaplan, Lukáš | Tlustoš, Pavel
Potential changes in the mobility and bioavailability of risk and essential macro- and micro-elements achieved by adding various ameliorative materials were evaluated in a model pot experiment. Spring wheat (Triticum aestivum L.) was cultivated under controlled condition for 60 days in two soils, uncontaminated Chernozem and multi-element contaminated Fluvisol containing 4900 ± 200 mg/kg Zn, 35.4 ± 3.6 mg/kg Cd, and 3035 ± 26 mg/kg Pb. The treatments were all contained the same amount of sulfur and were as follows: (i) digestate from the anaerobic fermentation of biowaste, (ii) fly ash from wood chip combustion, and (iii) ammonium sulfate. Macro- and micro-nutrients Ca, Mg, K, Fe, Mn, Cu, P, and S, and risk elements Cd, Cr, Pb, and Zn were assayed in soil extracts with 0.11 mol/l solution of CH₃COOH and in roots, shoots, and grain of wheat after 30 and 60 days of cultivation. Both digestate and fly ash increased levels of macro- and micro-nutrients as well as risk elements (especially Cd and Zn; the mobility of Pb decreased after 30 days of cultivation). The changes in element mobility in ammonium sulfate-treated soils appear to be due to both changes in soil pH level and inter-element interactions. Ammonium sulfate tended to be the most effective measure for increasing nutrient uptake by plants in Chernozem but with opposite pattern in Fluvisol. Changes in plant yield and element uptake in treated plants may have been associated with the higher proline content of wheat shoots cultivated in both soils compared to control. None of the treatments decreased uptake of risk elements by wheat plants in the extremely contaminated Fluvisol, and their accumulation in wheat grains significantly exceeded maximum permissible levels; these treatments cannot be used to enable cereal and other crop production in such soils. However, the combination of increased plant growth alongside unchanged element content in plant biomass in pots treated with digestate and fly ash suggests that these treatments have a beneficial impact on yield and may be effective treatments in crops grown for phytoremediation.
اظهر المزيد [+] اقل [-]Effects of combined ozone and cadmium stresses on leaf traits in two poplar clones النص الكامل
2015
Castagna, Antonella | Di Baccio, Daniela | Ranieri, Anna Maria | Sebastiani, L. | Tognetti, R.
Information on plant responses to combined stresses such as ozone (O₃) and cadmium (Cd) is scarce in tree species. On the other hand, high O₃ concentrations in the atmosphere and heavy metal contaminations in water and soil simultaneously affect forest ecosystems. Toxic metals may exacerbate the consequences of air pollutants. In this research, two poplar clones, differently sensitive to O₃ (“I-214” O₃-tolerant and “Eridano” O₃-sensitive), were grown for 5 weeks in pots supplied with 0 and 150 mg Cd kg⁻¹ soil and then exposed to a 15-day O₃ fumigation (60 nl l⁻¹, 5 h a day) or supplied with charcoal-filtered air under the same conditions (referred to as control samples). The effects of the two stressors, alone or in combination, on Cd accumulation, photosynthetic capacity, ethylene emission and oxidative state were investigated in fully expanded leaves. Cadmium accumulation in leaves caused a reduction, but not complete failure, of photosynthesis in Eridano and I-214 poplar clones. The reduction in assimilation rate was more important following O₃ fumigation. Stomatal aperture after O₃ treatment, instead, increased in I-214 and decreased in Eridano. Overall, Cd treatment was effective in decreasing ethylene emission, whereas O₃ fumigation increased it in both clones, although interacting with the metal treatment. Again, O₃ fumigation induced a significant increase in ascorbate (ASA) + dehydroascorbate (DHA) content, which was strongly oxidised by O₃, thus decreasing the redox state. On the other hand, Cd treatment had a positive effect on ASA content and redox state in I-214, but not in Eridano. Although Cd and O₃ are known to share some common toxicity pathways, the combined effects induced distinct clone-specific responses, underlying the complexity of plant reactions to multiple stresses.
اظهر المزيد [+] اقل [-]Toxicity assessment of the water used for human consumption from the Cameron/Tuba City abandoned uranium mining area prior/after the combined electrochemical treatment/advanced oxidation النص الكامل
2015
Gajski, Goran | Oreščanin, Višnja | Gerić, Marko | Kollar, Robert | Lovrenčić Mikelić, Ivanka | Garaj-Vrhovac, Vera
The purpose of this work was detailed physicochemical, radiological, and toxicological characterization of the composite sample of water intended for human consumption in the Cameron/Tuba City abandoned uranium mining area before and after a combined electrochemical/advanced oxidation treatment. Toxicological characterization was conducted on human lymphocytes using a battery of bioassays. On the bases of the tested parameters, it could be concluded that water used for drinking from the tested water sources must be strictly forbidden for human and/or animal consumption since it is extremely cytogenotoxic, with high oxidative stress potential. A combined electrochemical treatment and posttreatment with ozone and UV light decreased the level of all physicochemical and radiological parameters below the regulated values. Consequently, the purified sample was neither cytotoxic nor genotoxic, indicating that the presented method could be used for the improvement of water quality from the sites highly contaminated with the mixture of heavy metals and radionuclides.
اظهر المزيد [+] اقل [-]Life cycle analysis of management options for organic waste collected in an urban area النص الكامل
2015
Di Maria, Francesco | Micale, Caterina
Different options for managing the organic fraction (OF) of municipal solid waste generated in a given urban area were analyzed by life cycle assessment (LCA) for different source segregation (SS) intensities ranging from 0 to 52 %. The best management option for processing the OF remaining in the residual organic fraction (ROF) for the different SS intensities was by incineration. Landfilling and mechanical biological treatment (MBT) of ROF gave higher impacts. Aerobic treatment alone or combined with anaerobic digestion (AD) for processing the source-segregated organic fraction (SSOF) led to relevant environmental impact reduction even if the difference between the two options was quite negligible. The weighted impact showed that scenarios using incineration always gave environmental gains, whereas there was a higher environmental burden with the scenarios using MBT.
اظهر المزيد [+] اقل [-]Environmental fate and exposure; neonicotinoids and fipronil النص الكامل
2015
Bonmatin, J.-M. | Giorio, C. | Girolami, V. | Goulson, D. | Kreutzweiser, D. P. | Krupke, C. | Liess, M. | Long, E. | Marzaro, M. | Mitchell, E. A. D. | Noome, D. A. | Simon-Delso, N. | Tapparo, A.
Systemic insecticides are applied to plants using a wide variety of methods, ranging from foliar sprays to seed treatments and soil drenches. Neonicotinoids and fipronil are among the most widely used pesticides in the world. Their popularity is largely due to their high toxicity to invertebrates, the ease and flexibility with which they can be applied, their long persistence, and their systemic nature, which ensures that they spread to all parts of the target crop. However, these properties also increase the probability of environmental contamination and exposure of nontarget organisms. Environmental contamination occurs via a number of routes including dust generated during drilling of dressed seeds, contamination and accumulation in arable soils and soil water, runoff into waterways, and uptake of pesticides by nontarget plants via their roots or dust deposition on leaves. Persistence in soils, waterways, and nontarget plants is variable but can be prolonged; for example, the half-lives of neonicotinoids in soils can exceed 1,000 days, so they can accumulate when used repeatedly. Similarly, they can persist in woody plants for periods exceeding 1 year. Breakdown results in toxic metabolites, though concentrations of these in the environment are rarely measured. Overall, there is strong evidence that soils, waterways, and plants in agricultural environments and neighboring areas are contaminated with variable levels of neonicotinoids or fipronil mixtures and their metabolites (soil, parts per billion (ppb)-parts per million (ppm) range; water, parts per trillion (ppt)-ppb range; and plants, ppb-ppm range). This provides multiple routes for chronic (and acute in some cases) exposure of nontarget animals. For example, pollinators are exposed through direct contact with dust during drilling; consumption of pollen, nectar, or guttation drops from seed-treated crops, water, and consumption of contaminated pollen and nectar from wild flowers and trees growing near-treated crops. Studies of food stores in honeybee colonies from across the globe demonstrate that colonies are routinely and chronically exposed to neonicotinoids, fipronil, and their metabolites (generally in the 1–100 ppb range), mixed with other pesticides some of which are known to act synergistically with neonicotinoids. Other nontarget organisms, particularly those inhabiting soils, aquatic habitats, or herbivorous insects feeding on noncrop plants in farmland, will also inevitably receive exposure, although data are generally lacking for these groups. We summarize the current state of knowledge regarding the environmental fate of these compounds by outlining what is known about the chemical properties of these compounds, and placing these properties in the context of modern agricultural practices.
اظهر المزيد [+] اقل [-]Modeling for waste management associated with environmental-impact abatement under uncertainty النص الكامل
2015
Li, P. | Li, Y. P. | Huang, G. H. | Zhang, J. L.
Municipal solid waste (MSW) treatment can generate significant amounts of pollutants, and thus pose a risk on human health. Besides, in MSW management, various uncertainties exist in the related costs, impact factors, and objectives, which can affect the optimization processes and the decision schemes generated. In this study, a life cycle assessment-based interval-parameter programming (LCA-IPP) method is developed for MSW management associated with environmental-impact abatement under uncertainty. The LCA-IPP can effectively examine the environmental consequences based on a number of environmental impact categories (i.e., greenhouse gas equivalent, acid gas emissions, and respiratory inorganics), through analyzing each life cycle stage and/or major contributing process related to various MSW management activities. It can also tackle uncertainties existed in the related costs, impact factors, and objectives and expressed as interval numbers. Then, the LCA-IPP method is applied to MSW management for the City of Beijing, the capital of China, where energy consumptions and six environmental parameters [i.e., CO₂, CO, CH₄, NOX, SO₂, inhalable particle (PM₁₀)] are used as systematic tool to quantify environmental releases in entire life cycle stage of waste collection, transportation, treatment, and disposal of. Results associated with system cost, environmental impact, and the related policy implication are generated and analyzed. Results can help identify desired alternatives for managing MSW flows, which has advantages in providing compromised schemes under an integrated consideration of economic efficiency and environmental impact under uncertainty.
اظهر المزيد [+] اقل [-]An estimation of mercury concentrations in the local atmosphere of Almadén (Ciudad Real Province, South Central Spain) during the twentieth century النص الكامل
2015
Tejero, José | Higueras, Pablo L. | Garrido, Ignacio | Esbrí, José M. | Oyarzun, Roberto | Español, Santiago
We show the first estimations of long-term (100 years, 1900 to 2000) total gaseous mercury concentrations (TGM) in the urban area of Almadén. The estimation was carried out by comparing data on known metallic mercury production with measured TGM concentrations. The estimated diurnal background level ranges from 60 to 120 ng m⁻³and corresponds to periods when the metallurgical complex (cinnabar roasting plant) was shut down. The average TGM concentration during the period from 1900 to 2000 was about 600 ng m⁻³(with peaks above 1,200 ng m⁻³). Additionally, a 24-h-based TGM monitoring program has highlighted significant differences between the diurnal and nocturnal concentrations, particularly during the warmer months. In this regard, given that the average nocturnal to diurnal ratio is 2.12, we suggest that the average nocturnal concentrations must have exceeded 1,200 ng m⁻³, and peak nocturnal concentrations could have reached levels up to 2,400 ng m⁻³. Our estimations indicate that most parts of the town of Almadén were generally exposed to TGM concentrations in air that exceed the World Health Organization air quality guideline for Hg (1,000 ng m⁻³) for countryside and urban areas.
اظهر المزيد [+] اقل [-]Physiological and biochemical response of soil-grown barley (Hordeum vulgare L.) to cerium oxide nanoparticles النص الكامل
2015
Rico, Cyren M. | Barrios, Ana C. | Tan, Wenjuan | Rubenecia, Rosnah | Lee, Sang-Chul | Varela-Ramirez, Armando | Peralta-Videa, Jose R. | Gardea-Torresdey, Jorge L.
A soil microcosm study was performed to examine the impacts of cerium oxide nanoparticles (nCeO₂) on the physiology, productivity, and macromolecular composition of barley (Hordeum vulgare L.). The plants were cultivated in soil treated with nCeO₂ at 0, 125, 250, and 500 mg kg⁻¹ (control, nCeO₂-L, nCeO₂-M, and nCeO₂-H, respectively). Accumulation of Ce in leaves/grains and its effects on plant stress and nutrient loading were analyzed. The data revealed that nCeO₂-H promoted plant development resulting in 331 % increase in shoot biomass compared with the control. nCeO₂ treatment modified the stress levels in leaves without apparent signs of toxicity. However, plants exposed to nCeO₂-H treatment did not form grains. Compared with control, nCeO₂-M enhanced grain Ce accumulation by as much as 294 % which was accompanied by remarkable increases in P, K, Ca, Mg, S, Fe, Zn, Cu, and Al. Likewise, nCeO₂-M enhanced the methionine, aspartic acid, threonine, tyrosine, arginine, and linolenic acid contents in the grains by up to 617, 31, 58, 141, 378, and 2.47 % respectively, compared with the rest of the treatments. The findings illustrate the beneficial and harmful effects of nanoceria in barley.
اظهر المزيد [+] اقل [-]Occurrence of selected pharmaceuticals in water and sediment of Umgeni River, KwaZulu-Natal, South Africa النص الكامل
2015
Matongo, Solomon | Birungi, Grace | Moodley, Brenda | Ndungu, Patrick
Selected pharmaceuticals including antibiotics, antipyretics, a stimulant, an antiepileptic and an antipsychotic drug were determined in wastewater, surface water and sediment along the Umgeni River which is the main source of water to Durban City in KwaZulu-Natal, South Africa. Samples were analysed using high-performance liquid chromatography coupled to a mass spectrometer (HPLC-MS/MS) after clean up and pre-concentration by solid phase extraction (SPE). At the wastewater treatment plant outlet, the antipyretic ibuprofen was detected in concentrations up to 12.94 μg/L and 15.96 ng/g in wastewater and bio-solids, respectively. The antipsychotic clozapine was detected in concentrations up to 14.43 μg/L and 18.75 ng/g in wastewater and bio-solids, respectively. Other pharmaceuticals namely sulfamethazine, sulfamethoxazole, erythromycin, metronidazole, trimethoprim, acetaminophen, caffeine and carbamazepine were also detected but in lower concentration compared to clozapine and ibuprofen (<10 μg/L or 10 ng/g). Clozapine and ibuprofen were detected at high concentrations in the surface water and sediment of Umgeni River. The highest concentration of clozapine (78.33 μg/L) was detected at the business park, while that for ibuprofen (62.0 μg/L) was detected at the point where a tributary, Msunduzi, joins Umgeni. Metronidazole was only detected in sediment, and caffeine (2243.52 ng/g) was detected at the highest concentration in the sediment at the blue lagoon sampling site. The antibiotic sulfamethoxazole was also detected in appreciable amounts up to 507.34 ng/g in the sediment at the Msunduzi tributary sampling site. The data collected implies that while insufficiently treated wastewater contributes to surface water contamination, human activities also contribute appreciably to the pharmaceutical loading of River Umgeni.
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