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Результаты 701-710 из 2,500
Seaweeds and plastic debris can influence the survival of faecal indicator organisms in beach environments
2014
Quilliam, Richard S. | Jamieson, Julie | Oliver, David M.
The revised Bathing Water Directive (rBWD) introduces more stringent standards for microbial water quality and promotes more pro-active management of the beach environment through the production of a bathing water profile (BWP). The aim of this study was to determine whether living seaweeds in the littoral zone are colonised by faecal indicator organisms (FIOs), and to quantify the survival dynamics of waterborne Escherichia coli in microcosms containing senescing seaweeds. Living seaweed (Fucus spiralis) was not associated with FIO colonisation, although could be providing a protected environment in the underlying sand. Senescing seaweeds enhanced waterborne E. coli survival compared to plastic debris, with the brown seaweed Laminaria saccharina facilitating greater E. coli persistence than either Chondrus crispus or Ulva lactuca. This has important implications for FIO survival on bathing beaches as the majority of beach-cast biomass is composed of brown seaweeds, which could support significant levels of FIOs.
Показать больше [+] Меньше [-]Diffusion of microcystins (cyanobacteria hepatotoxins) from the reservoir of Isahaya Bay, Japan, into the marine and surrounding ecosystems as a result of large-scale drainage
2014
Takahashi, Tohru | Umehara, Akira | Tsutsumi, Hiroaki
In the artificial reservoir of the Isahaya reclaimed land, Nagasaki, Japan, algal blooms have become an annual event, dominated primarily by the microcystin (MC) producing cyanobacteria Microcystis aeruginosa. Although the majority of MCs are either degraded by bacteria or washed out to sea, some remain in the sediment of the reservoir and bay throughout the year. As a result, they also accumulate in aquatic organisms (mullet, oyster, etc.) that inhabit the reservoir and surrounding areas, as well as midge flies that spend their larval period in the bottom of the reservoir. Accordingly, MCs also accumulate in the predators of these organisms, allowing the toxin to spread from the hydrosphere to terrestrial ecosystems. The most effective method for resolving this potentially dangerous condition is to introduce seawater into the reservoir by opening the drainage gates at high tide.
Показать больше [+] Меньше [-]Organic matter and pyritization relationship in recent sediments from a tropical and eutrophic bay
2014
Sabadini-Santos, Elisamara | Senez, Thaise M. | Silva, Tabatta S. | Moreira, Manuel R. | Mendonça-Filho, João Graciano | Santelli, Ricardo E. | Crapez, Mirian A.C.
The degree of pyritization (DOP) and the extension of metals incorporation into pyrite was investigated at Guanabara Bay sediments. Maximum concentrations of total organic carbon (TOC), total sulfur, biopolymers and viable bacteria cells were observed in silted stations close to discharge points of sewage and minimum concentrations at sandy stations at the entrance of the bay. Pyrite iron concentrations (Fepy) was always lower than the reactive iron and Fepy were below the detection limit at sandy stations. The same trend was found to metals, which its degree of pyritization was Mn=Cu>As=Co>Ni>Cd>Zn≫Pb>Cr. The bay gathers all required factors to sulfate reduction and pyrite formation, once the C:S ratio express the reduced tendency conditions, almost half of the TOC present in its sediments is labile and both reactive sulfur and iron are available. However the degree of trace metals pyritization did not exceed 20%, consistent with the median DOP (29%).
Показать больше [+] Меньше [-]Impact of multispecies diatom bloom on plankton community structure in Sundarban mangrove wetland, India
2014
Biswas, Sejuti Naha | Rakshit, Dibyendu | Sarkar, Santosh Kumar | Sarangi, Ranjit Kumar | Satpathy, Kamala Kanta
A multispecies bloom caused by the centric diatoms, viz. Coscinodiscus radiatus, Chaetoceros lorenzianus and the pennate diatom Thalassiothrix frauenfeldii was investigated in the context of its impact on phytoplankton and microzooplankton (the loricate ciliate tintinnids) in the coastal regions of Sagar Island, the western part of Sundarban mangrove wetland, India. Both number (15–18 species) and cell densities (12.3×103cellsl−1 to 11.4×105cellsl−1) of phytoplankton species increased during peak bloom phase, exhibiting moderately high species diversity (H′=2.86), richness (R′=6.38) and evenness (E′=0.80). The diatom bloom, which existed for a week, had a negative impact on the tintinnid community in terms of drastic changes in species diversity index (1.09–0.004) and population density (582.5×103 to 50×103indm−3). The bloom is suggested to have been driven by the aquaculture activities and river effluents resulting high nutrient concentrations in this region. An attempt has been made to correlate the satellite remote sensing-derived information to the bloom conditions. MODIS-Aqua derived chlorophyll maps have been interpreted.
Показать больше [+] Меньше [-]Use of GIS for the evaluation of heavy metal contamination in the Cunha Canal watershed and west of the Guanabara Bay, Rio de Janeiro, RJ
2014
Borges, Renata Coura | Caldas, Vanessa Godoy | Filho, Francisco Fernando Lamego Simões | Ferreira, Marcos Manoel | Lapa, Celso Marcelo Franklin
The Cunha Canal watershed, which is located in the municipality of Rio de Janeiro, suffered severe environmental degradation in recent decades due to rapid urban population growth. However, this substantial growth did not result in social development; instead, it exacerbated existing environmental and social problems. This study aimed to evaluate the pollution of the Canal do Cunha and Guanabara Bay, using GIS for mapping based on the result of the heavy metal concentrations obtained by spectrometry (ICP-OES). The analyzed data were monitored at five collection points. Five heavy metals (Cd, Pb, Cu, Ni and Zn) were evaluated. The results showed that the waters of the Cunha Canal watershed and the west side of Guanabara Bay have been altered and degraded. The concentration of heavy metals in the water was lower than the concentration in the sediments. The behaviors of the studied metals differed during the rainy and dry periods.
Показать больше [+] Меньше [-]Uncharted sources of particle bound polycyclic aromatic hydrocarbons from South Asia: Religious/ritual burning practices
2014
Dewangan, Shippi | Pervez, Shamsh | Chakrabarty, Rajan | Zielinska, Barbara
This paper deals with the real–world emissions of particle bound polycyclic aromatic hydrocarbons (PAHs) emitted from different religious and ritual burning practices in India. The emission factors (EFs) of various PAHs were characterized over integrated stages of burning practices including pyrolysis, flaming and smoldering. Sampling was carried out in selected five different types of religious and ritual places: Hindu Temples (HT), Muslim Holy shrines (MG), Buddhist Temples (BT), Hindu Marriage Places (MP) and Cremation Centers (Hindu Funeral Pyre) (CC); where burning practices mostly include natural and synthetic biomaterials in different proportions. Seventy PAHs were analyzed and grouped in light PAHs (LPAHs=25) and heavy PAHs (HPAHs=45) according to number of benzene rings present and respective molecular weights. The average EF of total PAHs (TPAHs) from MP, MG, BT, HT and CC is estimated as 77.04±5.39, 99.09±6.02, 90.35±6.76, 22.78±1.57, and 77.15±6.16mg kg−1, respectively. Country level emission budget of particulate bound TPAHs from religious and ritual burning practices has also been evaluated to 0.47Gg yr−1; contributed ~23% of the 2.07Gg yr−1 – Indian emission budget of PAHs from unknown sources reported earlier.
Показать больше [+] Меньше [-]Effect of short–time variations of wind velocity on mass transfer rate between street canyons and the atmospheric boundary layer
2014
Murena, Fabio | Mele, Benedetto
2D URANS CFD simulations were conducted to study the effect of short–time variations of wind velocity on mass transfer rate between street canyons and the atmospheric boundary layer (ABL). A street canyon with a height–to– width ratio (aspect ratio) of three was considered as a case study. The study is of practical interest since it illustrates a skimming flow regime, the regime where pollutants are less effectively exchanged between the canyon and the above atmosphere, typically found in many urban areas in Mediterranean countries. Short–time variations of wind velocity magnitude were simulated assuming a sinusoidal function with average magnitude = 4m s−1; amplitude ±2m s−1 and period from 1 to 40 s, and subsequently with short–time averaged (0.1 s, 1 s and 10 s) real world data measured with an ultrasonic anemometer (50Hz). Mass transfer rate between the canyon and the ABL was evaluated as the rate of reduction of spatially averaged concentration of a passive pollutant, carbon monoxide (CO), in the street canyon. Results show that mass transfer rate increases with the frequency of short–time variations. In CFD studies pertaining to pollutant dispersion in street canyons, wind hourly average velocity is usually assumed as a reference value to simulate real world cases. Our results show that this input data must be completed with additional information about the extent of variation in wind intensity and its frequency in the hour.
Показать больше [+] Меньше [-]Vertical distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) in southwest of the Caspian Sea: Most petrogenic events during the late Little Ice Age
2014
Varnosfaderany, Mohammad Nemati | Bakhtiari, Alireza Riyahi | Gu, Zhaoyan | Chu, Guoqiang
In this study, 75 samples of two 210Pb-dated cores from the southwest of the Caspian Sea were analysed for 30 compounds of polycyclic aromatic hydrocarbons (PAHs). The TPAH29 flux of the last six centuries ranged from 16.3 to 177.3 and 22.3 to 426.2ngcm−2y−1 in the Rezvanshahr and Anzali core sediments, respectively. Prior to 1840, four distinct maxima in PAH fluxes (61–426.2ngcm−2y−1) with a low weathered petrogenic pattern were found in each of the core sediments. Simultaneity of distinct peaks of PAH fluxes before 1840 and Caspian Sea level high-stands during the Little Ice Age (LIA), revealed the high importance of this phenomenon in washing and transport of land-based oil pollution into the Caspian Sea. An overall increase in some diagnostic ratios (Flu/202, IP/276 and BaA/228), especially after 1940, indicated increase of pyrogenic PAHs as a result of industrial development in the catchment area.
Показать больше [+] Меньше [-]Adsorption and desorption behaviors of selected endocrine disrupting chemicals in simulated gastrointestinal fluids
2014
Fei, Ying-heng | Leung, Kenneth M.Y. | Li, Xiao-yan
An in vitro technique using simulated gastrointestinal (GI) fluids was applied to investigate the desorption of selected endocrine disrupting chemicals (EDCs), i.e. bisphenol A (BPA) and 17 α-ethinylestradiol (EE2), from the marine sediment in the digestive environment. The results show that the GI fluids suppressed chemical adsorption and greatly increased the desorption of BPA and EE2 from the sediment. Pepsin in the gastric fluid would compete for the adsorption sites with the adsorbates, and bile salts in the intestinal fluid had a solubilization effect on the chemicals. The amount of chemical release from the sediment in different fluids followed intestinal (fed)>intestinal (fasted)>gastric>saline water. During the dynamic desorption tests, 62% and 21% of sediment-bound BPA and EE2, respectively, could be released into the simulated GI fluids. The enhanced desorption of EDCs from sediment in the digestive system would make the pollutants more bioavailable in the ecosystem.
Показать больше [+] Меньше [-]Shifting environmental baselines in the Red Sea
2014
Price, A.R.G. | Ghazi, S.J. | Tkaczynski, P.J. | Venkatachalam, A.J. | Santillan, A. | Pancho, T. | Metcalfe, R. | Saunders, J.
The Red Sea is among the world’s top marine biodiversity hotspots. We re-examined coastal ecosystems at sites surveyed during the 1980s using the same methodology. Coral cover increased significantly towards the north, mirroring the reverse pattern for mangroves and other sedimentary ecosystems. Latitudinal patterns are broadly consistent across both surveys and with results from independent studies. Coral cover showed greatest change, declining significantly from a median score of 4 (1000–9999m2) to 2 (10–99m2) per quadrat in 2010/11. This may partly reflect impact from coastal construction, which was evident at 40% of sites and has significantly increased in magnitude over 30years. Beach oil has significantly declined, but shore debris has increased significantly. Although substantial, levels are lower than at some remote ocean atolls. While earlier reports have suggested that the Red Sea is generally healthy, shifting environmental baselines are evident from the current study.
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