خيارات البحث
النتائج 101 - 110 من 2,513
Long-term behaviour of 137Cs in spruce bark in coniferous forests in the Czech Republic النص الكامل
2014
Rulík, Petr | Pilátová, Helena | Suchara, Ivan | Sucharová, Julie
Activity concentrations of 137Cs were detected in more than 400 outer spruce bark samples collected at sites variably affected by Chernobyl fallout across the Czech Republic in 1995 and 2010. The temporal changes in the 137Cs activities were found. The mean effective half-life (TEF) for 137Cs in spruce bark was 9.6 years, and the mean environmental half-life (TE) was 14 years. The effective half-lives were significantly higher in areas with higher long-term annual precipitation sums. Coefficient a in linear regression y = ax + b of half-lives on precipitation sums was 0.015 y mm−1 for TEF and 0.036 y mm−1 for TE. The aggregated transfer factor of 137Cs from soil to bark was determined and the pre-Chernobyl bark contamination related to year 2010 was estimated.
اظهر المزيد [+] اقل [-]Effects of biochar and activated carbon amendment on maize growth and the uptake and measured availability of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) النص الكامل
2014
Brennan, Aoife | Moreno Jiménez, Eduardo | Alburquerque, José A. | Knapp, Charles W. | Switzer, Christine
With the aim of investigating the effects of carbonaceous sorbent amendment on plant health and end point contaminant bioavailability, plant experiments were set up to grow maize (Zea mays) in soil contaminated with polycyclic aromatic hydrocarbons (PAHs) and metals. Maize and pine derived biochars, as well as a commercial grade activated carbon, were used as amendments. Plant growth characteristics, such as chlorophyll content and shoot to root biomass, improved with sorbent amendment to varying extents and contaminant uptake to shoots was consistently reduced in amended soils. By further defining the conditions in which sorbent amended soils successfully reduce contaminant bioavailability and improve plant growth, this work will inform field scale remediation efforts.
اظهر المزيد [+] اقل [-]Spatial and temporal distribution of chiral pesticides in Calanus spp. from three Arctic fjords النص الكامل
2014
Carlsson, Pernilla | Warner, Nicholas A. | Hallanger, Ingeborg G. | Herzke, Dorte | Kallenborn, Roland
Concentration and enantiomeric fractions (EFs) of chiral chlorinated pesticides (α-hexachlorocyclohexane (α-HCH), trans-, cis- and oxychlordane) were determined in Arctic zooplankton, mainly Calanus spp. collected in the period 2007–11 from Svalbard fjords and open pack-ice. The temporal and spatial enantiomer distribution varied considerably for all species and chiral pesticides investigated. An overall enantiomeric excess of (+)-oxychlordane (EF 0.53–0.86) were observed. Cis-chlordane was close to racemic (EF 0.46–0.55), while EF for trans-chlordane varied between 0.29 and 0.55, and between 0.38 and 0.59 for α-HCH. The biodegradation potential for trans-chlordane was higher compared to cis-chlordane. The comprehensive statistical evaluation of the data set revealed that the EF distribution of α-HCH was affected by ice cover to a higher extent compared to cis-chlordane. Potential impact from benthic processes on EFs in zooplankton is an interesting feature and should be further investigated. Enantiomeric selective analyses may be a suitable tool for investigations of climate change related influences on Arctic ecosystems.
اظهر المزيد [+] اقل [-]Uptake and elimination kinetics of metals in soil invertebrates: A review النص الكامل
2014
Ardestani, Masoud M. | Straalen, N. M. van | van Gestel, Cornelis A.M.
Uptake and elimination kinetics of metals in soil invertebrates are a function of both soil and organism properties. This study critically reviewed metal toxicokinetics in soil invertebrates and its potential use for assessing bioavailability. Uptake and elimination rate constants of different metals are summarized. Invertebrates have different strategies for essential and non-essential metals. As a consequence, different types of models must be applied to describe metal uptake and elimination kinetics. We discuss model parameters for each metal separately and show how they are influenced by exposure concentrations and by physiological properties of the organisms. Soil pH, cation exchange capacity, clay and organic matter content significantly affect uptake rates of non-essential metals in soil invertebrates. For essential metals, kinetics is hardly influenced by soil properties, but rather prone to physiological regulation mechanisms of the organisms. Our analysis illustrates that toxicokinetics can be a valuable measurement to assess bioavailability of soil-bound metals.
اظهر المزيد [+] اقل [-]Metals in European roadside soils and soil solution – A review النص الكامل
2014
Werkenthin, Moritz | Kluge, Björn | Wessolek, Gerd
This review provides a summary of studies analysing metal concentrations in soils and soil solution at European roadsides. The data collected during 27 studies covering a total of 64 sites across a number of European countries were summarised. Highest median values of Cr, Cu, Ni, Pb, and Zn were determined in the top soil layer at the first 5 m beside the road. Generally, the influence of traffic on soil contamination decreased with increasing soil depth and distance to the road. The concentration patterns of metals in soil solution were independent from concentrations in the soil matrix. At 10-m distance, elevated soil metal concentrations, low pH, and low percolation rates led to high solute concentrations. Directly beside the road, high percolation rates lead to high annual loadings although solute concentrations are comparatively low. These loadings might be problematic, especially in regions with acidic sandy soils and a high groundwater table.
اظهر المزيد [+] اقل [-]Limited effect of urban tree vegetation on NO2 and O3 concentrations near a traffic route النص الكامل
2014
Grundström, Maria | Pleijel, Håkan
Concentrations of NO2 and O3 were measured inside and outside a dense broad-leaved forest canopy adjacent to a busy traffic route in the City of Gothenburg, Sweden, with duplicate passive diffusion samplers during six one-week periods starting well before leaf senescence and ending when leaves were largely senescent. Concentrations of NO2 were lower inside the forest canopy during all periods (representing a significant effect, p = 0.016), on average by 7% or 2.7 μg m−3. O3 showed a more variable response with an average non-significant effect of 2% lower in the forest stand. There was no systematic trend of the difference in concentrations inside and outside the forest stand of the pollutants with the progression of autumn leaf senescence. Our study indicates that the effect of urban vegetation on air pollution concentrations is small, although it seems to exist for NO2 in a traffic polluted environment.
اظهر المزيد [+] اقل [-]Temporal and spatial variation in residential soil metal concentrations: Implications for exposure assessments النص الكامل
2014
Aelion, C Marjorie | Davis, Harley T. | Lawson, Andrew B. | Cai, Bo | McDermott, Suzanne
Understanding temporal and spatial variation in soil chemicals is critical in exposure assessments. We measured eight metals in subsamples, duplicates (∼0.3 m), and repeat soil samples taken 1–6 years after initial sampling (∼5 m). We estimated variance components (VCs) of metal concentrations using nested analyses accounting for sampling area, land use and soil type, and calculated coefficients of variation (CVs) for repeat sample pairs. Total variance for all metals was similar, but VCs were proportioned differently by metal and sample type. Spatial variation explained the majority of variance in duplicate samples. CVs of metal concentrations were not significantly different over the long time interval, but repeat samples had larger VCs for unexplained error. Sampling area and land use were important for Ba and Mn, and Pb and Hg, respectively. Results suggest metals are stable over long times and suitable for exposure assessments, but that individual metal behavior should be considered.
اظهر المزيد [+] اقل [-]The effect of humic acids on biodegradation of polycyclic aromatic hydrocarbons depends on the exposure regime النص الكامل
2014
Tejeda-Agredano, Maria-Carmen | Mayer, Philipp | Ortega-Calvo, Jose Julio
The effect of humic acids on biodegradation of polycyclic aromatic hydrocarbons depends on the exposure regime النص الكامل
2014
Tejeda-Agredano, Maria-Carmen | Mayer, Philipp | Ortega-Calvo, Jose Julio
Binding of polycyclic aromatic hydrocarbons (PAHs) to dissolved organic matter (DOM) can reduce the freely dissolved concentration, increase apparent solubility or enhance diffusive mass transfer. To study the effects of DOM on biodegradation, we used phenanthrene and pyrene as model PAHs, soil humic acids as model DOM and a soil Mycobacterium strain as a representative degrader organism. Humic acids enhanced the biodegradation of pyrene when present as solid crystals but not when initially dissolved or provided by partitioning from a polymer. Synchronous fluorescence spectrophotometry, scintillation counting and a microscale diffusion technique were applied in order to determine the kinetics of dissolution and diffusive mass transfer of pyrene. We suggest that humic acids can enhance or inhibit biodegradation as a result of the balance of two opposite effects, namely, solubilization of the chemicals on the one hand and inhibition of cell adhesion to the pollutant source on the other.
اظهر المزيد [+] اقل [-]The effect of humic acids on biodegradation of polycyclic aromatic hydrocarbons depends on the exposure regime النص الكامل
2014
Tejeda Agredano, M. C. | Mayer, Philipp | Ortega Calvo, J. J.
Binding of polycyclic aromatic hydrocarbons (PAHs) to dissolved organic matter (DOM) can reduce the freely dissolved concentration, increase apparent solubility or enhance diffusive mass transfer. To study the effects of DOM on biodegradation, we used phenanthrene and pyrene as model PAHs, soil humic acids as model DOM and a soil Mycobacterium strain as a representative degrader organism. Humic acids enhanced the biodegradation of pyrene when present as solid crystals but not when initially dissolved or provided by partitioning from a polymer. Synchronous fluorescence spectrophotometry, scintillation counting and a microscale diffusion technique were applied in order to determine the kinetics of dissolution and diffusive mass transfer of pyrene. We suggest that humic acids can enhance or inhibit biodegradation as a result of the balance of two opposite effects, namely, solubilization of the chemicals on the one hand and inhibition of cell adhesion to the pollutant source on the other. | Support for this research was provided by the Spanish Ministry of Economy and Competitiveness (grants CGL2007-64199 and CGL2010-22068-C02-01), the FPI Program (M.C. Tejeda-Agredano), Junta de Andalucía (PAI RNM 312) and the European Commission (MODELPROBE, no. 213161). | Peer Reviewed
اظهر المزيد [+] اقل [-]Warfarin, a potential pollutant in aquatic environment acting through Pxr signaling pathway and γ-glutamyl carboxylation of vitamin K-dependent proteins النص الكامل
2014
Fernández, Ignacio | Santos, Adriana | Cancela, M Leonor | Laizé, Vincent | Gavaia, Paulo J.
Warfarin, a potential pollutant in aquatic environment acting through Pxr signaling pathway and γ-glutamyl carboxylation of vitamin K-dependent proteins النص الكامل
2014
Fernández, Ignacio | Santos, Adriana | Cancela, M Leonor | Laizé, Vincent | Gavaia, Paulo J.
Warfarin-induced vitamin K (VK) recycling impairment is used worldwide as a rodenticide and human thromboembolic prophylactic. Since VK metabolism/signaling pathways have been conserved throughout vertebrate evolution, its release to the environment might impact on aquatic organisms. Present study assessed the toxic effect of warfarin (0, 5, 25 and 125 mg L−1) on zebrafish development and characterized underlying mechanisms of action through qPCR analysis of VK-related genes. Expression of pregnane X receptor (pxr), the nuclear receptor binding vitamin K, was ubiquitous in zebrafish and suggests that warfarin exposure may interfere with several biological processes. Indeed, warfarin exposure of zebrafish larvae caused hemorrhages in brain, skeletal deformities and triggered ectopic calcifications, which may be the consequence of an altered γ-carboxylation of VK-dependent proteins and/or pxr signaling. This study provides new insights into warfarin effects as a bone homeostasis disruptor and soft tissue calcification inductor, and its potential risk for aquatic environments.
اظهر المزيد [+] اقل [-]Warfarin, a potential pollutant in aquatic environment acting through Pxr signaling pathway and γ-glutamyl carboxylation of vitamin K-dependent proteins النص الكامل
2014
Fernández Monzón, Ignacio | Santos, Adriana | Cancela, M Leonor | Laizé, Vincent | Gavaia, Paulo J | Fundação para a Ciência e a Tecnologia (Portugal) | European Commission | Fernández Monzón, Ignacio [0000-0002-8088-7902}
10 páginas, 7 figuras, 1 tabla. | Warfarin-induced vitamin K (VK) recycling impairment is used worldwide as a rodenticide and human thromboembolic prophylactic. Since VK metabolism/signaling pathways have been conserved throughout vertebrate evolution, its release to the environment might impact on aquatic organisms. Present study assessed the toxic effect of warfarin (0, 5, 25 and 125 mg L(-1)) on zebrafish development and characterized underlying mechanisms of action through qPCR analysis of VK-related genes. Expression of pregnane X receptor (pxr), the nuclear receptor binding vitamin K, was ubiquitous in zebrafish and suggests that warfarin exposure may interfere with several biological processes. Indeed, warfarin exposure of zebrafish larvae caused hemorrhages in brain, skeletal deformities and triggered ectopic calcifications, which may be the consequence of an altered γ-carboxylation of VK-dependent proteins and/or pxr signaling. This study provides new insights into warfarin effects as a bone homeostasis disruptor and soft tissue calcification inductor, and its potential risk for aquatic environments. | The authors are gratefully to Patrícia Diogo for technical assistance during sampling procedures. IF acknowledges the financial support of the Portuguese Fundation for Science and Technology (FCT) through the post-doctoral grant SFRH/BDP/82049/2011. This work was partly funded by the FCT through SPECIAL K (PDTC/MAR/ 105152/2008) and AQUATOX (PTDC/MAR/112992/2009) projects and by the European Commission (ERDF-COMPETE) through PEstC/MAR/LA0015/2011 project. | Peer reviewed
اظهر المزيد [+] اقل [-]Factors influencing surface CO2 variations in LPRU, Thailand and IESM, Philippines النص الكامل
2014
Macatangay, Ronald | Sonkaew, Thiranan | Velazco, Voltaire | Gerbig, Christoph | Intarat, Nilubol | Nantajai, Nittaya | Bagtasa, Gerry
Surface carbon dioxide concentrations were measured using a non-dispersive infrared carbon dioxide sensor at Lampang Rajabhat University from April to May 2013 and at the University of the Philippines-Diliman campus starting September 2013. Factors influencing the variations in these measurements were determined using multiple linear regression and a Lagrangian transport model. Air temperature and sea level pressure were the dominant meteorological factors that affect the CO2 variations. However, these factors are not enough. Surface CO2 flux and transboundary transport needs to be considered as well.
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