خيارات البحث
النتائج 3891 - 3900 من 4,309
Characteristics and source apportionment of black carbon aerosols over an urban site النص الكامل
2017
Rajesh, T. A. | Ramachandran, S.
Aethalometer based source apportionment model using the measured aerosol absorption coefficients at different wavelengths is used to apportion the contribution of fossil fuel and wood burning sources to the total black carbon (BC) mass concentration. Temporal and seasonal variabilities in BC mass concentrations, equivalent BC from fossil fuel (BC f f), and wood burning (BC w b) are investigated over an urban location in western India during January 2014 to December 2015. BC, BC f f , and BC w b mass concentrations exhibit strong diurnal variation and are mainly influenced by atmospheric dynamics. BC f f was higher by a factor of 2–4 than BC w b and contributes maximum to BC mass throughout the day, confirming consistent anthropogenic activities. Diurnal contribution of BC f f and BC w b exhibits opposite variation due to differences in emission sources over Ahmedabad. Night time BC values are about a factor of 1.4 higher than day time BC values. The annual mean percentage contributions of day time and night time are 42 and 58 %, respectively. BC, BC f f , and BC w b mass concentrations exhibit large and significant variations during morning, afternoon, evening, and night time. During afternoon, mass concentration values are minimum throughout the year because of the fully evolved boundary layer and reduced anthropogenic activities. BC exhibits a strong seasonal variability with postmonsoon high (8.3 μg m ⁻³) and monsoon low (1.9 μg m ⁻³). Annual mean BC f f and BC w b contributions are 80 and 20 %, respectively, to total BC, which suggests that major contribution of BC in Ahmedabad comes from fossil fuel emissions. The results show that the study location is dominated by fossil fuel combustion as compared to the emissions from wood burning. The results obtained represent a regional value over an urban regime which can be used as inputs on source apportionment to model BC emissions in regional and global climate models.
اظهر المزيد [+] اقل [-]Alteration of membrane integrity and respiratory function of brain mitochondria in the rats chronically exposed to a low dose of acetamiprid النص الكامل
2017
Gasmi, Salim | Kebieche, Mohammed | Rouabhi, Rachid | Touahria, Chouaib | Lahouel, Asma | Lakroun, Zohra | Henine, Sara | Soulimani, Rachid
The pesticides are used in several fields of agriculture and farms to protect crops against harmful insects and herbs. The increased and uncontrolled use of these pollutants is very hazardous for the population health. Consumption of contaminated food matrices with these pesticides could impair the cell integrity and its molecular function. The main aim of this present study was to evaluate the alteration of the integrity of mitochondrial membranes and respiratory chain potential in the brain of rats exposed during 90 days to acetamiprid (AC), organochlorine of the new generation. After oral administration of AC in rats with 3.14 mg/kg of body weight, the results of this current study showed enhance in mitochondrial oxidative stress status by significant decrease of glutathione (GSH) level, glutathione pyroxidase (GPx), and catalase (CAT) activities. On the other hand, there is an increase in the enzymatic activity of the glutathione s-transferase (GST) and superoxide dismutase (SOD); at the same time, the MDA level was also highly increased. Furthermore, evaluation results of brain mitochondrial integrity revealed a significant increase in membrane permeability and mitochondrial swelling in rats exposed chronically to AC. Instead, other results of this present work showed a significant decrease in mitochondrial respiration potent (O₂ consumption) in acetamiprid-treated rats. In conclusion, the long duration exposition of the animals to AC has led to respiratory chain dysfunction, disturbance of matrix oxidative status, and a loss of mitochondrial membranes integrity.
اظهر المزيد [+] اقل [-]Effects of fine particulate matter and its constituents on emergency room visits for asthma in southern Taiwan during 2008–2010: a population-based study النص الكامل
2017
Hwang, Su-Lun | Lin, Yu-Ching | Lin, Chieh-Mo | Hsiao, Kuang-Yu
This population-based study evaluated the short-term association between fine particulate matter (PM₂.₅) concentrations and its constituents and hospital emergency room visits (ERVs) for asthma in southern Taiwan during the period 2008–2010. Data on hospital ERVs for asthma and ambient PM₂.₅ levels and its constituents were obtained from the National Health Insurance Research database and the Environmental Protection Administration, respectively. The quasi-Poisson generalized additive model was used to explore the associations between PM₂.₅ and hospital ERVs for asthma. During the study period, the average daily number of ERVs for asthma and mean 24-h average level of PM₂.₅ was 20.0 and 39.4 μg m⁻³, respectively. The estimated effects of PM₂.₅ on asthma ERVs fluctuated with increasing tendencies after adjusting for O₃ and attenuating tendencies after adjusting for NO₂, SO₂, and CO. Children were more susceptible than other age groups to the effects of PM₂.₅ exposure on asthma ERVs, with the relative risks (RRs) for every 10 μg m⁻³ increase in PM₂.₅ being 1.016 [95% confidence interval (CI) = 1.002–1.030] and 1.018 (95% CI = 1.002–1.034), respectively, at a lag 0 day (i.e., no lag days) and lag 0–1 days. The effect of PM₂.₅ concentrations on asthma ERVs was similar in male and female. Furthermore, asthma ERVs was significantly associated with concentrations of nitrate (NO₃⁻), with the RR for each 1 μg m⁻³ increase in NO₃⁻ concentrations being 1.004 (95% CI = 1.001–1.007) at lag 0 day. In conclusion, both PM₂.₅ concentrations and its chemical constituents are associated with ERVs for asthma; moreover, children were more susceptible to the effects of PM₂.₅ in southern Taiwan. PM₂.₅ constituent, nitrate, is more closely related to ERVs for asthma.
اظهر المزيد [+] اقل [-]Silicon and Rhizophagus irregularis: potential candidates for ameliorating negative impacts of arsenate and arsenite stress on growth, nutrient acquisition and productivity in Cajanus cajan (L.) Millsp. genotypes النص الكامل
2017
Garg, Neera | Kashyap, Lakita
Arsenic (As) gets accumulated in plants via phosphorous transporters and water channels and interferes with nutrient and water uptake, adversely affecting growth and productivity. Although, Si and AM have been reported to combat arsenic stress, their comparative and interactive roles in ameliorating As V and As III toxicities have not been reported. Study evaluated effects of Si and Rhizophagus irregularis on growth, As uptake and yield under arsenate and arsenite stress in two pigeonpea genotypes (metal tolerant—Pusa 2002 and metal sensitive—Pusa 991). Higher As accumulation and translocation was observed in As III treated roots of Pusa 991 than those of Pusa 2002 when compared with As V. Roots were more negatively affected than shoots which led to a significant decline in nutrient uptake, leaf chlorophylls, and yield, with As III inducing more negative effects. Pusa 2002 established more effective mycorrhizal symbiosis and had higher biomass than Pusa 991. Si was more effective in inducing shoot biomass while AM inoculation significantly improved root biomass. AM enhanced Si uptake in roots and leaves in a genotype dependent manner. Combined application of Si and AM were highly beneficial in improving leaf water status, chlorophyll pigments, biomass, and productivity. Complete amelioration of negative impacts of both concentrations of As V and lower concentration of As III were recorded under +Si +AM in Pusa 2002. Results highlighted great potential of Si in improving growth and productivity of pigeonpea through R. irregularis under As V and As III stresses.
اظهر المزيد [+] اقل [-]Polybrominated diphenyl ethers (PBDEs) in background air around the Aegean: implications for phase partitioning and size distribution النص الكامل
2017
Besis, Athanasios | Lammel, Gerhard | Kukučka, Petr | Samara, Constantini | Sofuoglu, Aysun | Dumanoglu, Yetkin | Eleftheriadis, Kostas | Kouvarakis, Giorgos | Sofuoglu, Sait C. | Vassilatou, Vassiliki | Voutsa, Dimitra
The occurrence and atmospheric behavior of tri- to deca-polybrominated diphenyl ethers (PBDEs) were investigated during a 2-week campaign concurrently conducted in July 2012 at four background sites around the Aegean Sea. The study focused on the gas/particle (G/P) partitioning at three sites (Ag. Paraskevi/central Greece/suburban, Finokalia/southern Greece/remote coastal, and Urla/Turkey/rural coastal) and on the size distribution at two sites (Neochorouda/northern Greece/rural inland and Finokalia/southern Greece/remote coastal). The lowest mean total (G + P) concentrations of ∑₇PBDE (BDE-28, BDE-47, BDE-66, BDE-99, BDE-100, BDE-153, BDE-154) and BDE-209 (0.81 and 0.95 pg m⁻³, respectively) were found at the remote site Finokalia. Partitioning coefficients, K P, were calculated, and their linear relationships with ambient temperature and the physicochemical properties of the analyzed PBDE congeners, i.e., the subcooled liquid pressure (P L°) and the octanol-air partition coefficient (K OA), were investigated. The equilibrium adsorption (P L°-based) and absorption (K OA-based) models, as well as a steady-state absorption model including an equilibrium and a non-equilibrium term, both being functions of log K OA, were used to predict the fraction Φ of PBDEs associated with the particle phase. The steady-state model proved to be superior to predict G/P partitioning of BDE-209. The distribution of particle-bound PBDEs across size fractions < 0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and > 7.2 μm indicated a positive correlation between the mass median aerodynamic diameter and log P L° for the less brominated congeners, whereas a negative correlation was observed for the high brominated congeners. The potential source regions of PBDEs were acknowledged as a combination of long-range transport with short-distance sources.
اظهر المزيد [+] اقل [-]Environmental investigation for the presence of Vibrio species following a case of severe gastroenteritis in a touristic island النص الكامل
2017
Economopoulou, Assimoula | Chochlakis, Dimosthenis | Almpan, Michael Angelos | Sandalakis, Vassilios | Maraki, Sofia | Tselentis, Yannis | Psaroulaki, Anna
Global changes have caused a worldwide increase in reports of Vibrio-associated diseases with ecosystem-wide impacts on humans and marine animals. In Europe, higher prevalence of human infections followed regional climatic trends with outbreaks occurring during episodes of unusually warm weather. Similar patterns were also observed in Vibrio-associated diseases affecting marine organisms such as fish, bivalves, and corals. Following a possible human case of infection due to V. cholerae in the island of Kos (eastern Aegean, Greece), environmental samples were collected and tested for the presence of Vibrio species. Using chromogenic agar and MALDI-TOF MS, V. parahaemolyticus, V. vulnificus V. furnisii, V. alginolyticus, and V. fluvialis were isolated and/or identified. The presence of V. cholerae was established by PCR-sequencing analysis only. Following the susceptibility testing of the Vibrio isolates, only one, V. furnisii, showed intermediate resistance to ciprofloxacin. The rest of the isolates were susceptible to all antibiotics tested. The presence of Vibrio species in aquatic samples reveals potential dangers due to exposure to contaminated seawaters.
اظهر المزيد [+] اقل [-]Reliable methods for determination of triazine herbicides and their degradation products in seawater and marine sediments using liquid chromatography-tandem mass spectrometry النص الكامل
2017
Rodríguez-González, N. | Uzal-Varela, R. | González-Castro, M.J. | Muniategui-Lorenzo, S. | Beceiro-González, E.
Triazines and their degradation products are transported to the aquatic environment, and once there, the probability to reach the marine environment is very high. In this paper, solid phase extraction (SPE) and extraction by matrix solid phase dispersion (MSPD) to analyse nine triazines (ametryn, atrazine, cyanazine, prometryn, propazine, simazine, simetryn, terbuthylazine and terbutryn) and eight degradation products (desethylatrazine, desethyldesisopropylatrazine, desethyl-2-hydroxyatrazine, desethylterbuthylazine, desisopropylatrazine, desisopropyl-2-hydroxyatrazine, 2-hydroxyatrazine and 2-hidroxyterbuthylazine) in seawater and marine sediments samples were used. The analysis was carried out using liquid chromatography with tandem mass spectrometry (LC-ESI-MS/MS). The methods were optimized and validated to achieve a selective and sensitive determination of the analytes from different sample, regardless of its complexity. Under the optimum conditions, the proposed methods provided adequate limits of quantification (0.05–0.45 μg L⁻¹ and 0.23–4.26 μg kg⁻¹ in seawater and marine sediments, respectively). Intra- and inter-day relative standard deviation were below 1.41% for all compounds. Recoveries were evaluated, and acceptable values that ranged from 87.5–99.4 and 60.9–99.7% for the seawater and sediment samples, respectively, were obtained. The proposed methods were applied to the analysis of the target compounds in seawater samples and marine sediments from a coastal area of Galicia (NW of Spain).
اظهر المزيد [+] اقل [-]Biosynthesis of metal nanoparticles using three marine plant species: anti-algal efficiencies against “Oscillatoria simplicissima” النص الكامل
2017
El-Kassas, Hala Y. | Ghobrial, Mary G.
This study aims at controlling of the cyanobacteria Oscillatoria simplicissima, those that produce neurotoxins and have negative impacts on the aquatic organisms, using biosynthesized metal nanoparticles (NPs). Silver-NPs (Ag-NPs) have been successfully biosynthesized using Nannochloropsis oculata and Tetraselmis tetrathele cultures. Also, Ag-NPs and iron oxide-NPs (Fe₃O₄-NPs) were synthesized by Halophila stipulacea aqueous extract. The structural composition of the different biosynthesized NPs was studied. The algae cultures and the extract were used as reductants of AgNO₃, and brown colors due to Ag-NP biosynthesis were observed. Silver signals were recorded in their corresponding EDX spectra. FTIR analyses showed that proteins in N. oculata and T. tetrathele cultures reduced AgNO₃, and aromatic compounds stabilized the biogenic Ag-NPs. H. stipulacea extract contains proteins and polyphenols that could be in charge for the reduction of silver and iron ions into nanoparticles and polysaccharides which stabilized the biosynthesized Ag-NPs and Fe₃O₄-NPs. The Ag-NPs biosynthesized by T. tetrathele cultures and H. stipulacea aqueous extract exerted outstanding negative impacts on O. simplicissima (optical density and total chlorophyll) and the Ag-NPs biosynthesized using N. oculata culture exerted the moderate performance. The study results suggest that the bioactive compounds present in the FTIR profiles of the Ag-NPs and or ionic silver may be the main contributors in their anti-algal effects. A trial to use the biosynthesized Fe₃O₄-NPs using H. stipulacea aqueous extract to separate Ag-NPs was successfully carried out. Since the synthesis and applications of nanomaterials is a hot subject of research, the study outcomes not only provide a green approach for the synthesis of metal-NPs but also open the way for more nanoparticle applications.
اظهر المزيد [+] اقل [-]Effects of land disturbance on runoff and sediment yield after natural rainfall events in southwestern China النص الكامل
2017
Guo, Xiaomeng | Li, Tianyang | He, Binghui | He, Xiaorong | Yao, Yun
Severe soil erosion occurs in southwestern China owing to the large expanses of urbanization and sloping land. This field monitoring study was conducted to record the rainfall events, runoff, and sediment yield in 20-, 40-, and 60-m plots under conditions of artificial disturbance or natural restoration in the purple soil area of southwestern China. The study took place during the rainy season, and the plots were situated on a 15° slope. The results showed that rainstorms and heavy rainstorms generated runoff and sediment yield. Rainfall intensity had a significantly positive power relationship with runoff rate and sediment yield rate in artificially disturbed plots but not in naturally restored plots. Plot length had a significant effect on runoff rate under artificial disturbance but not natural restoration. Within the same land disturbance category, there was no significant effect of plot length on sediment yield rate but there was a significant effect on sediment concentration. Overall, runoff rate, sediment yield rate, and sediment concentration showed remarkable effects of land disturbance across all plot lengths: naturally restored plots had 62.8–77.5% less runoff, 95.1–96.3% less sediment yield, and 63.1–73.5% lower sediment concentration than artificially disturbed plots. The relationship between runoff rate and sediment rate under the different land disturbances could be described by an exponential function. The results not only demonstrate the effectiveness of natural restoration for controlling runoff and sediment yield but also provide useful information for the design of field studies, taking into consideration the complexity of terrestrial systems.
اظهر المزيد [+] اقل [-]Comparison of bioaccumulation and elimination of Escherichia coli and male-specific bacteriophages by ascidians and bivalves النص الكامل
2017
Kim, Ji Hoe | Shim, Kil Bo | Shin, Soon Beum | Park, Kunbawui | Oh, Eun Gyoung | Son, Kwang Tae | Yu, Hongsik | Lee, Hee Jung | Mok, Jong Soo
Levels of Escherichia coli and male-specific bacteriophages (MSBs) were determined in the filter feeders obtained from retail markets, commercial farms, and wild beds in Korea. The accumulation and elimination of E. coli and MSBs were compared between ascidians and bivalves (oysters and mussels) during relaying and depuration. E. coli concentrations in ascidians from retail markets ranged between < 20 and 460 most probable number/100 g while MSBs were not detected. E. coli levels in bivalves from commercial farms and wild beds were not significantly different but bacterial levels in ascidians were consistently lower. Ascidians exhibited much lower ability than bivalves to accumulate E. coli and MSBs during relaying in a polluted coastal area. This study also shows that an equilibrium was developed between levels of microbes in water and ascidians and shellfish during relaying. E. coli and MSBs in ascidians decreased quickly during depuration in a clean seawater tank. However, after 1 day, E. coli in bivalves decreased by only 1.1–1.6 logs, and the elimination of MSBs was negligible. Therefore, depuration is an effective means to reduce the health risk of contaminated ascidians.
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