Уточнить поиск
Результаты 1-10 из 35
Prevalence, antibiotic resistance patterns and molecular characterization of Escherichia coli from Austrian sandpits
2014
Badura, Alexandra | Luxner, Josefa | Feierl, Gebhard | Reinthaler, Franz F. | Zarfel, Gernot | Galler, Herbert | Pregartner, Gudrun | Riedl, Regina | Grisold, Andrea J.
The aim was to determine the prevalence of E. coli and coliform bacteria in playground sand of all public children's sandpits in Graz (n = 45), Austria, and to assess the frequency of antimicrobial resistance in E. coli. Molecular characterization included the discrimination of O-serotypes and H-antigens and the determination of virulence and resistance genes, using a microarray technology. E. coli isolates were tested for susceptibility to a set of antibiotics by VITEK2 system and disk diffusion method. In total, 22 (49%) and 44 (98%) sandpits were positive for E. coli and coliform bacteria. Median concentrations of E. coli and coliform bacteria in the sand samples were: 2.6 × 104 CFU/100 g and 3.0 × 105 CFU/100 g. Resistance rates were: ampicillin, 12.5%; piperacillin, 10.4%; amoxicillin/clavulanic acid, 9.4%; cotrimoxazole, 6.3%; tetracycline, 6.3%; piperacillin/tazobactam, 5.2%. No ESBL- or carbapenemase-producing isolates were found. The most prevalent serogroups were O15, O6 and O4. Isolates harbored 0 up to 16 different virulence genes.
Показать больше [+] Меньше [-]Comparison of three labeled silica nanoparticles used as tracers in transport experiments in porous media. Part II: Transport experiments and modeling
2014
Vitorge, Elsa | Szenknect, Stéphanie | Martins, Jean M.-F. | Barthès, Véronique | Gaudet, Jean-Paul
Three types of labeled silica nanoparticles were used in transport experiments in saturated sand. The goal of this study was to evaluate both the efficiency of labeling techniques (fluorescence (FITC), metal (Ag(0) core) and radioactivity (110mAg(0) core)) in realistic transport conditions and the reactive transport of silica nanocolloids of variable size and concentration in porous media. Experimental results obtained under contrasted experimental conditions revealed that deposition in sand is controlled by nanoparticles size and ionic strength of the solution. A mathematical model is proposed to quantitatively describe colloid transport. Fluorescent labeling is widely used to study fate of colloids in soils but was the less sensitive one. Ag(0) labeling with ICP-MS detection was found to be very sensitive to measure deposition profiles. Radiolabeled (110mAg(0)) nanoparticles permitted in situ detection. Results obtained with radiolabeled nanoparticles are wholly original and might be used for improving the modeling of deposition and release dynamics.
Показать больше [+] Меньше [-]Regional distribution of styrene analogues generated from polystyrene degradation along the coastlines of the North-East Pacific Ocean and Hawaii
2014
Kwon, Bum Gun | Saido, Katsuhiko | Koizumi, Koshiro | Sato, Hideto | Ogawa, Naoto | Chung, Seon -Yong | Kusui, Takashi | Kodera, Yoichi | Kogure, Kazuhio
Beach sand and seawater taken from the coastlines of the North-East Pacific Ocean and Hawaii State were investigated to determine the causes of global chemical contamination from polystyrene (PS). All samples were found to contain styrene monomer (SM), styrene dimers (SD), and styrene trimers (ST) with a concentration distribution of styrene analogues in the order of ST > SD > SM. The contamination by styrene analogues along the West Coast proved more severe than in Alaska and other regions. The Western Coastlines of the USA seem be affected by both land- and ocean-based pollution sources, which might result from it being a heavily populated area as the data suggest a possible proportional relationship between PS pollution and population. Our results suggest the presence of new global chemical contaminants derived from PS in the ocean, and along coasts.
Показать больше [+] Меньше [-]Deepwater marine litter densities and composition from submersible video-transects around the ABC-islands, Dutch Caribbean
2014
Debrot, A.O. | Vinke, E. | van der Wende, G. | Hylkema, A. | Reed, J.K.
Baseline data on anthropogenic seafloor debris contamination in the year 2000 is provided for 24 submersible video transects at depths of 80–900m, off the Dutch ABC-islands (Aruba, Bonaire, Curaçao), in the southeastern Caribbean Sea. In total, 202 objects were documented from a combined 21,184m of transect, ranging from sandy lower island-slope to rocky upper island-slope habitat. Debris densities differed significantly with depth. Highest debris accumulation (0.459 items 100m−2 or 4590 items per km2) occurred at depths of 300–600m on more shallow-sloping (20–30°) sand and silt bottoms. The overall average debris density was 0.27 objects per 100m2 (or 2700 items per km2), which is an order of magnitude higher than most other deepwater debris studies. What we describe may be representative for other small, populated, steep volcanic Caribbean islands. Food and beverage-related items were the single largest usage category identified (44% of objects; mostly glass beverage bottles).
Показать больше [+] Меньше [-]Diversity of bacterial community and detection of nirS- and nirK-encoding denitrifying bacteria in sandy intertidal sediments along Laizhou Bay of Bohai Sea, China
2014
Wang, Liping | Zheng, Binghui | Nan, Bingxu | Hu, Peilong
The microbial community and the nirS- and nirK-encoding denitrifiers in the intertidal sediments along Laizhou Bay in China were studied using pyrosequencing and real-time quantitative PCR (qPCR), respectively. There were three primary intertidal zones: Laizhou (La), Weifang Harbor (We), and Dongying (Do). Significant differences in composition and abundances at the different taxonomic levels were observed among the three bacterial communities. The qPCR results indicated that the nirS gene abundance varied from 8.67×105 to 5.68×106copies/gwet weight (ww), whereas the nirK gene abundance varied from 1.26×105 to 1.89×106copies/gww. The canonical correlation analysis (CCA) indicated that the sand percentage was the most important factor in shaping the bacterial community followed by silt percentage, NO2−, TOC, DO, pH, and clay percentage, whereas the clay percentage, pH, NO3−, DO, NO2−, TOC, silt percentage, and sand percentage were the most important factors associated with regulating the abundance of nirS- and nirK-encoding denitrifiers.
Показать больше [+] Меньше [-]Small-scale early aggregation of green tide macroalgae observed on the Subei Bank, Yellow Sea
2014
Hu, Song | Yang, Hong | Zhang, Jianheng | Chen, Changsheng | He, Peimin
Massive green algae blooms became an environmental disaster in the Yellow Sea from 2008 to 2013. Recent studies suggested that recurrences of early aggregates of macroalgae were found over the Subei Bank, a unique shallow radial sand ridge system off the Jiangsu coast, China. Yearly field surveys have been carried out over this bank during the past five years (2009–2013), with an aim at identifying and qualifying the physical–biological mechanism for the early aggregation of algae. Data synthesis showed that early aggregation of macroalgae usually occurred from April–May as small-scale patches either over the intertidal mudflat of the Subei Bank or along local isobaths in the northern coastal area north of the bank. Both hydrographic and current measurements were performed by tracking a narrow patchy area of floating macroalgae (nearly 4km in length and 5–10m in width) on April 26, 2013, and the results showed that the algae aggregation was mainly caused by tide-induced convergence. This convergence was produced by the local geometrically controlled interaction of tidal currents with mudflats, which is believed to be a key physical mechanism for the early development of algal blooms in addition to marine ecosystem responses and human aquaculture activities.
Показать больше [+] Меньше [-]Enrichment, distribution and sources of heavy metals in the sediments of Deception Bay, Queensland, Australia
2014
Brady, James P. | Ayoko, G. A. (Godwin A.) | Martens, Wayde N. | Goonetilleke, Ashantha
Sediment samples from 13 sampling sites in Deception Bay, Australia were analysed for the presence of heavy metals. Enrichment factors, modified contamination indices and Nemerow pollution indices were calculated for each sampling site to determine sediment quality. The results indicate significant pollution of most sites by lead (average enrichment factor (EF) of 13), but there is also enrichment of arsenic (average EF 2.3), zinc (average EF 2.7) and other heavy metals. The modified degree of contamination indices (average 1.0) suggests that there is little contamination. By contrast, the Nemerow pollution index (average 5.8) suggests that Deception Bay is heavily contaminated. Cluster analysis was undertaken to identify groups of elements. Strong correlation between some elements and two distinct clusters of sampling sites based on sediment type was evident. These results have implications for pollution in complex marine environments where there is significant influx of sand and sediment into an estuarine environment.
Показать больше [+] Меньше [-]Mercury speciation in coastal sediments from the central east coast of India by modified BCR method
2014
Chakraborty, Parthasarathi | Raghunadh Babu, P.V. | Vudamala, Krushna | Ramteke, Darwin | Chennuri, Kartheek
This is the first study to describe distribution and speciation of Hg in coastal sediments from the central east coast of India. The concentrations of Hg in the studied sediments were found to be much lower than the Hg concentration recommended in coastal sediments by the United State Environmental Protection Agency and the Canadian Council of Ministers of the Environment for the protection of aquatic life. This study suggests that the interactions between Hg and coastal sediments are influenced by particle size (sand, silt and clay) of the sediments and the total organic carbon (TOC) content in the sediments. It was found that the coastal sediments from the central east coast of India could act as a sink for Hg. The availability of strong uncomplexed-Hg binding sites in the coastal sediments was observed.
Показать больше [+] Меньше [-]BIOB: A mathematical model for the biodegradation of low solubility hydrocarbons
2014
Geng, Xiaolong | Boufadel, Michel C. | Personna, Yves R. | Lee, Ken | Tsao, David | Demicco, Erik D.
Modeling oil biodegradation is an important step in predicting the long term fate of oil on beaches. Unfortunately, existing models do not account mechanistically for environmental factors, such as pore water nutrient concentration, affecting oil biodegradation, rather in an empirical way. We present herein a numerical model, BIOB, to simulate the biodegradation of insoluble attached hydrocarbon. The model was used to simulate an experimental oil spill on a sand beach. The biodegradation kinetic parameters were estimated by fitting the model to the experimental data of alkanes and aromatics. It was found that parameter values are comparable to their counterparts for the biodegradation of dissolved organic matter. The biodegradation of aromatics was highly affected by the decay of aromatic biomass, probably due to its low growth rate. Numerical simulations revealed that the biodegradation rate increases by 3–4 folds when the nutrient concentration is increased from 0.2 to 2.0mgN/L.
Показать больше [+] Меньше [-]Physiological energetics of the fourth instar of Chinese horseshoe crabs (Tachypleus tridentatus) in response to hypoxic stress and re-oxygenation
2014
Shin, Paul K.S. | Chan, Cathy S.K. | Cheung, S.G.
Hypoxia associated with eutrophication is a potential threat to the Chinese horseshoe crab Tachypleus tridentatus which inhabits intertidal sand flats in Asia. This study investigated the effect of dissolved oxygen level (DO) (6, 4 and 2mg O2 l−1) on the physiological energetics in the juvenile T. tridentatus. They were exposed to various oxygen levels for three days and then transferred to normoxia for three days to examine the recovery from low oxygen stress. Feeding rate, respiration rate and scope for growth were reduced at lower DO levels while absorption efficiency and excretion rate were independent of DO levels. Although full recovery of the physiological responses and scope for growth from hypoxis stress was observed when normoxia resumed, their long term survival in suboptimal habitats with frequent occurrence of hypoxia deserves a close monitoring as hypoxia may be even more common in future in a warming world.
Показать больше [+] Меньше [-]