خيارات البحث
النتائج 201 - 210 من 1,506
One year intensive PM₂.₅ bound polycyclic aromatic hydrocarbons monitoring in the area of Tuscany, Italy. Concentrations, source understanding and implications
2012
Martellini, Tania | Giannoni, Martina | Lepri, Luciano | Katsoyiannis, Athanasios | Cincinelli, Alessandra
Polycyclic aromatic hydrocarbons (PAHs) associated to PM₂.₅ particles were monitored at three sites in the region of Tuscany, Italy, during the period March 2009–March 2010. PAH concentrations ranged between 0.92 ng m⁻³ and 13 ng m⁻³. The spatial and seasonal differences observed at the three sites are discussed and attributed to specific PAH sources. Benzo[a]Pyrene average annual values were below the EU limit value of 1.0 ng m⁻³. The results of this study suggest that emissions from commuting and work related traffic play an important role for the city of Florence, whereas for the city of Livorno, the harbor activities seem to impact the PAH burden substantially, as well. The PAH cancer risk (expressed as the “BaPE index”) has shown a 6-fold decline compared to early 1990's concentrations and 2- to 3-fold decline compared to the late 1990's.
اظهر المزيد [+] اقل [-]Occurrence and persistence of organic emerging contaminants and priority pollutants in five sewage treatment plants of Spain: Two years pilot survey monitoring
2012
Bueno, M.J Martínez | Gomez, M.J. | Herrera, S. | Hernando, M.D. | Agüera, A. | Fernández-Alba, A.R.
This work summarized all results obtained during almost two-years of a monitoring programme carried out in five municipal sewage treatment plants (STPs) located in the north, centre and south-east of Spain. The study evaluated the occurrence and persistence of a group of 100 organic compounds belonging to several chemical groups (pharmaceuticals, personal care products, pesticides and metabolites). The average removal efficiencies of the STPs studied varied from 20% (erythromycin) to 99% (acetaminophen). In analysed samples, we identified a large number of compounds at mean range concentrations between 7–59,495 ng/L and 5–32,720 ng/L for influent and effluent samples, respectively. This study also identified 20 of the mostly detected and persistent compounds in wastewater effluent, of which hydrochlorothiazide, atenolol, gemfibrozil, galaxolide and three metabolites (fenofibric acid, 4-AAA and 4-FAA), presented the highest average contribution percentages, in relation to the total load of contaminants for the different STPs effluent studied.
اظهر المزيد [+] اقل [-]A sensitive crude oil bioassay indicates that oil spills potentially induce a change of major nitrifying prokaryotes from the Archaea to the Bacteria
2012
Urakawa, Hidetoshi | Garcia, Juan C. | Barreto, Patricia D. | Molina, Gabriela A. | Barreto, Jose C.
The sensitivity of nitrifiers to crude oil released by the BP Deepwater Horizon oil spill in Gulf of Mexico was examined using characterized ammonia-oxidizing bacteria and archaea to develop a bioassay and to gain further insight into the ecological response of these two groups of microorganisms to marine oil spills. Inhibition of nitrite production was observed among all the tested ammonia-oxidizing organisms at 100ppb crude oil. Nitrosopumilus maritimus, a cultured representative of the abundant Marine Group I Archaea, showed 20% inhibition at 1 ppb, a much greater degree of sensitivity to petroleum than the tested ammonia-oxidizing and heterotrophic bacteria. The differing susceptibility may have ecological significance since a shift to bacterial dominance in response to an oil spill could potentially persist and alter trophic interactions influenced by availability of different nitrogen species.
اظهر المزيد [+] اقل [-]Calibration and field performance of triolein embedded acetate membranes for passive sampling persistent organic pollutants in water
2012
Tang, Jianfeng | Chen, Shan | Xu, Yiping | Zhong, Wenjue | Ma, Mei | Wang, Zijian
Triolein embedded cellulose acetate membrane (TECAM) passive samplers provide potentially powerful tool for monitoring time weighted average concentrations (CTWA) of trace hydrophobic organic contaminants in water. To study the field performance of TECAM, exchange kinetics of chemicals between water and TECAM were studied at different temperature and water flow rates. Results showed that the uptake rate constant (kᵤ) in TECAM was less sensitive to temperature variation than the SPMD and Chemcatcher. The kᵤ in TECAM was sensitive to even a slight change of the flow rate, which required the field calibration using performance reference compounds (PRCs). To estimate CTWA by TECAM, both empirical model and WBL model were compared in laboratory conditions, and only small differences were observed between the predicted and measured kᵤ. Field validation was conducted to test the sampler performance alongside spot sampling. A good agreement of water concentration was obtained by the two sampling techniques.
اظهر المزيد [+] اقل [-]Toxicity of copper nanoparticles and CuCl₂ salt to Enchytraeus albidus worms: Survival, reproduction and avoidance responses
2012
Amorim, Mónica João Barros | Scott-Fordsmand, Janeck James
Environmental effects of copper nanoparticles are little studied in terrestrial ecosystems. In the present article, the toxicity of copper nanoparticles (Cu-NP) on the enchytraeid Enchytraeus albidus is compared to the toxicity of a copper-salt (CuCl₂). The effect parameters studied were survival, reproductive output and avoidance behaviour. The results show that Cu-NP were more toxic to E. albidus than the same concentrations of the CuCl₂-salt. The physic-chemical analysis of the particles indicated that only a small fraction was released as ions. Hence, the results indicated a nanoparticle-specific effect – lower reproductive output and higher avoidance. This was observed as 2–8 fold (significant) lower ECx values for Cu-NP (EC₅₀₋ᵣₑₚᵣₒd = 95 mg Cu/kg; EC₅₀₋ₐᵥₒᵢd = 241 mg Cu/kg) exposed organisms compared to CuCl₂ (EC₅₀ ₋ ᵣₑₚᵣₒd = 251 mg Cu/kg; EC₅₀₋ₐᵥₒᵢd = 475 mg Cu/kg) exposed organisms. These results corroborate with a nanoparticle-specific effect.
اظهر المزيد [+] اقل [-]Spatio-temporal patterns of Cu contamination in mosses using geostatistical estimation
2012
Martins, Anabela | Figueira, Rui | Sousa, António Jorge | Sérgio, Cecília
Several recent studies have reported temporal trends in metal contamination in mosses, but such assessments did not evaluate uncertainty in temporal changes, therefore providing weak statistical support for time comparisons. Furthermore, levels of contaminants in the environment change in both space and time, requiring space-time modelling methods for map estimation. We propose an indicator of spatial and temporal variation based on space-time estimation by indicator kriging, where uncertainty at each location is estimated from the local distribution function, thereby calculating variability intervals for comparison between several biomonitoring dates. This approach was exemplified using copper concentrations in mosses from four Portuguese surveys (1992, 1997, 2002 and 2006). Using this approach, we identified a general decrease in copper contamination, but spatial patterns were not uniform, and from the uncertainty intervals, changes could not be considered significant in the majority of the study area.
اظهر المزيد [+] اقل [-]Updated stomatal flux and flux-effect models for wheat for quantifying effects of ozone on grain yield, grain mass and protein yield
2012
Grünhage, Ludger | Pleijel, Håkan | Mills, Gina | Bender, Jürgen | Danielsson, Helena | Lehmann, Yvonne | Castell, Jean-Francois | Bethenod, Olivier
Field measurements and open-top chamber experiments using nine current European winter wheat cultivars provided a data set that was used to revise and improve the parameterisation of a stomatal conductance model for wheat, including a revised value for maximum stomatal conductance and new functions for phenology and soil moisture. For the calculation of stomatal conductance for ozone a diffusivity ratio between O₃ and H₂O in air of 0.663 was applied, based on a critical review of the literature. By applying the improved parameterisation for stomatal conductance, new flux-effect relationships for grain yield, grain mass and protein yield were developed for use in ozone risk assessments including effects on food security. An example of application of the flux model at the local scale in Germany shows that negative effects of ozone on wheat grain yield were likely each year and on protein yield in most years since the mid 1980s.
اظهر المزيد [+] اقل [-]The adaptive response of lichens to mercury exposure involves changes in the photosynthetic machinery
2012
Nicolardi, Valentina | Cai, Giampiero | Parrotta, Luigi | Puglia, Michele | Bianchi, Laura | Bini, Luca | Gaggi, Carlo
Lichens are an excellent model to study the bioaccumulation of heavy metals but limited information is available on the molecular mechanisms occurring during bioaccumulation. We investigated the changes of the lichen proteome during exposure to constant concentrations of mercury. We found that most of changes involves proteins of the photosynthetic pathway, such as the chloroplastic photosystem I reaction center subunit II, the oxygen-evolving protein and the chloroplastic ATP synthase β-subunit. This suggests that photosynthesis is a target of the toxic effects of mercury. These findings are also supported by changes in the content of photosynthetic pigments (chlorophyll a and b, and β-carotene). Alterations to the photosynthetic machinery also reflect on the structure of thylakoid membranes of algal cells. Response of lichens to mercury also involves stress-related proteins (such as Hsp70) but not cytoskeletal proteins. Results suggest that lichens adapt to mercury exposure by changing the metabolic production of energy.
اظهر المزيد [+] اقل [-]Investigation of antibiotics in mollusks from coastal waters in the Bohai Sea of China
2012
Li, Wenhui | Shi, Yali | Gao, Lihong | Liu, Jiemin | Cai, Yaqi
This study focused on the presence and distribution of 22 antibiotics, including eight quinolones, nine sulfonamides and five macrolides in mollusks from the Bohai Sea of China. 190 samples of eleven species were collected in 2006, 2007 and 2009. Laboratory analyses revealed that antibiotics were widely distributed in the mollusks with quinolones as the major compounds with concentrations of 0.71∼1575.10 μg/kg, which were up to two orders of magnitude higher than those of sulfonamides (0∼76.75 μg/kg) and macrolides (0∼36.21 μg/kg). The contents of quinolones and macrolides did not show significant changes from 2006, 2007 to 2009, while sulfonamides decreased significantly from 2006 to 2009. Compared with other sites, the city of Dalian was more polluted with quinolones, while Beidaihe was more contaminated with erythromycin and sulfapyridine. In addition, Mactra veneriformis and Meretrix merehjgntrix Linnaeus contained higher concentrations of quinolones and sulfamonomethoxine, while Mytilus edulis had higher levels of erythromycin and sulfapyridine.
اظهر المزيد [+] اقل [-]Toxicity assessment of simulated urban runoff containing polycyclic musks and cadmium in Carassius auratus using oxidative stress biomarkers
2012
Chen, Fang | Gao, Jie | Zhou, Qixing
The objective of this study was to assess potential toxic effects of simulated urban runoff on Carassius auratus using oxidative stress biomarkers. The activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and the content of malondialdehyde (MDA) in the liver of C. auratus were analyzed after a 7-, 14- and 21-day exposure to simulated urban runoff containing galaxolide (HHCB) and cadmium (Cd). The results showed that the activity of antioxidant enzymes and the content of MDA increased significantly exposed to the simulated urban runoff containing HHCB alone or mixture of HHCB and Cd. The activity of the investigated enzymes and the content of MDA then returned to the blank level over a longer period of exposure. The oxidative stress could be obviously caused in the liver of C. auratus under the experimental conditions. This could provide useful information for toxic risk assessment of urban runoff.
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