خيارات البحث
النتائج 751 - 760 من 3,243
Nearshore dynamics of artificial sand and oil agglomerates
2015
Dalyander, P Soupy | Plant, Nathaniel G. | Long, Joseph W. | McLaughlin, Molly
Weathered oil can mix with sediment to form heavier-than-water sand and oil agglomerates (SOAs) that can cause beach re-oiling for years after a spill. Few studies have focused on the physical dynamics of SOAs. In this study, artificial SOAs (aSOAs) were created and deployed in the nearshore, and shear stress-based mobility formulations were assessed to predict SOA response. Prediction sensitivity to uncertainty in hydrodynamic conditions and shear stress parameterizations were explored. Critical stress estimates accounting for large particle exposure in a mixed bed gave the best predictions of mobility under shoaling and breaking waves. In the surf zone, the 10-cm aSOA was immobile and began to bury in the seafloor while smaller size classes dispersed alongshore. aSOAs up to 5cm in diameter were frequently mobilized in the swash zone. The uncertainty in predicting aSOA dynamics reflects a broader uncertainty in applying mobility and transport formulations to cm-sized particles.
اظهر المزيد [+] اقل [-]Biological effects of long term fine limestone tailings discharge in a fjord ecosystem
2015
Brooks, Lucy | Melsom, Fredrik | Glette, Tormod
Benthic infaunal data collected from 1993 to 2010 were analysed to examine the effect of long term discharge of fine limestone tailings on macrofaunal species assemblages in a fjord. Relative distance from the outfall and proportion of fine tailings in the sediment were correlated with benthic community structure. Diversity decreased with increasing proportion of fine tailings. Biological Traits Analysis (BTA) was used to explore the temporal and spatial effects of the tailings gradient on macrofaunal functional attributes. BTA revealed that all stations along a pressure gradient of fine limestone tailings were dominated by free-living species. As the proportion of fine tailings in the sediment increased, there was an increase in fauna that were smaller, highly mobile, living on or nearer the surface sediment, with shorter lifespans. There was a decrease in permanent tube dwellers, those fauna with low or no mobility, that live deeper in the sediment and have longer lifespans (>5yrs).
اظهر المزيد [+] اقل [-]Heavy metal spatial variability and historical changes in the Yangtze River estuary and North Jiangsu tidal flat
2015
Liu, Zhiyong | Pan, Shaoming | Sun, Zhuyou | Ma, Renfeng | Chen, Lanhua | Wang, Yanlong | Wang, Shuao
This research focuses on the spatial and temporal patterns of heavy metals from the Yangtze River estuary and the tidal flat of north Jiangsu. Most heavy metals in the surficial sediments after normalization to Ti decreased seaward at the Yangtze River estuary. The core records showed that the heavy metal variations in the last 50years were primarily linked to natural weathering input of trace elements. However, significant heavy metal pollution (mainly Ni, Pb, Cd, Cu and As) were in the two study areas, with anthropogenic inventories accounting for 23–40% percent of the total pollution. Sequential extraction showed that Pb, Cu and Ni were present largely in the non-residual fraction, which indicated the potential bioavailability in the study areas. The SEM/EDS together with sequential extraction facilitated the easy tracing of the origin/sources of heavy metals in a simple way in the estuary and the tidal flat.
اظهر المزيد [+] اقل [-]Mercury concentrations in feathers of marine birds in Arctic Canada
2015
Mallory, Mark L. | Braune, Birgit M. | Provencher, Jennifer F. | Callaghan, D Benjamin | Gilchrist, H Grant | Edmonds, Samuel T. | Allard, Karel | O’Driscoll, Nelson J.
Mercury (Hg) concentrations are a concern in the Canadian Arctic, because they are relatively high compared to background levels and to similar species farther south, and are increasing in many wildlife species. Among marine birds breeding in the Canadian Arctic, Hg concentrations have been monitored regularly in eggs and intermittently in livers, but feathers have generally not been used as an indicator of Hg exposure or burden. We examined Hg concentrations in six marine bird species in the Canadian Arctic. Ivory gull Pagophila eburnea, feather Hg was exceptionally high, while glaucous gull Larus hyperboreus feather Hg was unexpectedly low, and ratios of feather THg to egg THg varied across species. The proportion of total Hg that was comprised of methyl Hg in ivory gull feathers was lower than in other species, and may be related to photo-demethylation or keratin breakdown in semi-opaque feather tissue.
اظهر المزيد [+] اقل [-]Characterizing the parent and oxygenated polycyclic aromatic hydrocarbons in mangrove sediments of Hong Kong
2015
Wang, Xiaowei | Yuan, Ke | Yang, Lihua | Lin, Li | Tam, Nora F.Y. | Chen, Baowei | Luan, Tiangang
Parent and oxygenated polycyclic aromatic hydrocarbons (PAHs) were investigated in mangrove sediments of Hong Kong. Most of the analytes were detected, and the dominant carbonylic and hydroxylated PAHs in mangrove sediments were 9-fluorenone and 2-hydroxy fluorene, respectively. The concentration of 9-fluorenone and 9,10-anthraquinone was higher than their parent PAHs. Moreover, the concentration of total organic matter (TOM) related with those of the parent PAHs and carbonylic PAHs, except for hydroxylated PAHs, which indicated that TOM was not the only factor regulating the distribution of oxygenated PAHs. Nevertheless, the parent PAHs in mangrove sediments was correlated positively with carbonylic PAHs which demostrated not only the similar source but also the fate of these two compound class. However, hydroxylated PAHs had different source by comparing with parent PAHs and carbonylic PAHs, they were probably originated from biodegradation and accumulated in mangrove sediments.
اظهر المزيد [+] اقل [-]Applying sediment quality guidelines on soft sediments of the Gulf of Finland, Baltic Sea
2015
Vallius, Henry
The Gulf of Finland is known to have been rather largely contaminated by heavy metals during the last half of the 20th century, but indications of recovery have been reported. In order to investigate the recent levels of heavy metals and arsenic in the uppermost soft sediments of the off-shore Gulf of Finland coring of altogether 23 sites were performed. The subsamples of the cores are 605 in total and thus give a good picture of heavy metal levels in the surface sediments during the first decade of this century. In order to evaluate methods and predict sediment toxicity the sediment concentrations are compared to American SQG:s. Majority of the subsamples exceeded the threshold levels of both used SQG:s, but some exceeded also the midrange effects quality guidelines. As, Cd, Hg, and Zn concentrations still occur at unacceptably high levels in sediments of the off-shore Gulf of Finland.
اظهر المزيد [+] اقل [-]Seasonal variation of fine particulate matter in residential micro–environments of Lahore, Pakistan
2015
Sidra, Safdar | Ali, Zulfiqar | Ahmad Nasir, Zaheer | Colbeck, I. (Ian)
Shifting seasons greatly influence the use and management practices in residential built environments which subsequently affect the level of exposure to various pollutants indoors. The levels of fine particulate matter (PM2.5) were monitored in fifteen households of Lahore, Pakistan during different seasons. DustTrak aerosol monitors (model 8520, TSI Inc.) were run simultaneously in the kitchens and living rooms of the selected sites for seventy two hours each. To aid analysis, houses were categorized in three groups according to floor area. For non–smoking houses there was little variation between 24h average PM2.5 concentrations in kitchens (270 to 295μg/m3) although there was an increase in concentrations in living rooms as floor area increased. Across all houses the average PM2.5 concentration was observed to vary during the seasons. In the kitchens the average PM levels were 326μg/m3 during the spring falling to 133μg/m3 in summer, 180μg/m3 in monsoon, 395μg/m3 in autumn and 448μg/m3 during the winter. Similarly, in the living rooms, the mean PM levels observed were 190μg/m3 in spring, 101μg/m3 in summer, 158μg/m3 in monsoon, 458μg/m3 in autumn and 590μg/m3 in winter. Factors contributing towards these levels were cooking (involving frequent frying), floor sweeping, and also movement of the occupants. Smoking at two sites and use of gas heaters during the winter were also identified as contributing sources. Apart from these sources, ventilation was identified to be the most singular attributing factor to the above mentioned variations in PM levels. Ventilation during the warm season ranged from 3.51 air changes per hour (ACH) to 7.68 ACH. On the contrary, ventilation decreased during the autumn and winter season (2.5 to 5.64 ACH) and this resulted in an accumulation of PM indoors. The levels of fine particulate matter were observed to be 3 to 23 times higher than the WHO established standard of 25μg/m3.
اظهر المزيد [+] اقل [-]Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada
2015
English, Matthew D. | Robertson, Gregory J. | Avery-Gomm, Stephanie | Pirie-Hay, Donald | Roul, Sheena | Ryan, Pierre C. | Wilhelm, Sabina I. | Mallory, Mark L.
Relatively little attention has been paid to the occurrence of anthropogenic debris found in coastal species, especially waterfowl. We examined the incidence of ingested plastic and metal in three waterfowl species wintering in Atlantic Canada: American black ducks (Anas rubripes) and mallards (A. platyrhynchos), two species that use marine and freshwater coastal habitats for foraging in the winter, and common eider (Somateria mollissima), a coastal marine species that feeds on intertidal and subtidal benthic organisms. Plastic was found in the stomachs of 46.1% (6/13) of mallards and 6.9% (6/87) of black ducks, the first report of ingested anthropogenic debris in these species, while 2.1% (1/48) of eider stomachs contained plastic. Metal was found in the stomachs of 30.8% (4/13) of mallards, 2.3% (2/87) of black ducks, and in 2.1% (1/48) of eiders. Our results indicate that species using coastal marine and freshwater environments are exposed to and ingest anthropogenic debris.
اظهر المزيد [+] اقل [-]Environmental radionuclides in a coastal wetland of the Southern Laizhou Bay, China
2015
Wang, Qidong | Song, Jinming | Li, Xuegang | Yuan, Huamao | Li, Ning | Cao, Lei
The radioactivity concentration of 238U, 232Th, 226Ra, 40K, and 137Cs in soil samples collected in a coastal wetland of the Southern Laizhou Bay, China were measured. Mean activity concentrations were 54.4±11.7, 57.9±9.7, 28.6±4.3, 542±21, and 10.2±2.9Bqkg−1 dry weight for 238U, 232Th, 226Ra, 40K and 137Cs, respectively. Statistical analyses suggested significant correlations between clay content and 40K as well as 137Cs. The radium equivalent activity, the absorbed dose rate in the air at 1m above the ground surface, and the external hazard index were calculated. The result showed that the radioactivity level in the wetland was in normal range. But sites along the river tended to have higher radiological hazard indexes. The vertical distributions of radionuclides in profiles illustrated some phenomena, such as vertical transport of 238U, disequilibrium between 238U and 226Ra, and change in material sources.
اظهر المزيد [+] اقل [-]Mercury speciation in the Adriatic Sea
2015
Kotnik, Jože | Horvat, Milena | Ogrinc, Nives | Fajon, Vesna | Žagar, Dušan | Cossa, Daniel | Sprovieri, Francesca | Pirrone, Nicola
Mercury and its speciation were studied in surface and deep waters of the Adriatic Sea. Several mercury species (i.e. DGM – dissolved gaseous Hg, RHg – reactive Hg, THg – total Hg, MeHg – monomethyl Hg and DMeHg – dimethylmercury) together with other water parameters were measured in coastal and open sea deep water profiles. THg concentrations in the water column, as well as in sediments and pore waters, were the highest in the northern, most polluted part of the Adriatic Sea as the consequence of Hg mining in Idrija and the heavy industry of northern Italy. Certain profiles in the South Adriatic Pit exhibit an increase of DGM just over the bottom due to its diffusion from sediment as a consequence of microbial and/or tectonic activity. Furthermore, a Hg mass balance for the Adriatic Sea was calculated based on measurements and literature data.
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