خيارات البحث
النتائج 1031 - 1040 من 3,991
Insights into bioassessment of marine pollution using body-size distinctness of planktonic ciliates based on a modified trait hierarchy
2016
Based on a modified trait hierarchy of body-size units, the feasibility for bioassessment of water pollution using body-size distinctness of planktonic ciliates was studied in a semi-enclosed bay, northern China. An annual dataset was collected at five sampling stations within a gradient of heavy metal contaminants. Results showed that: (1) in terms of probability density, the body-size spectra of the ciliates represented significant differences among the five stations; (2) bootstrap average analysis demonstrated a spatial variation in body-size rank patterns in response to pollution stress due to heavy metals; and (3) the average body-size distinctness (Δz+) and variation in body-size distinctness (Λz+), based on the modified trait hierarchy, revealed a clear departure pattern from the expected body-size spectra in areas with pollutants. These results suggest that the body-size diversity measures based on the modified trait hierarchy of the ciliates may be used as a potential indicator of marine pollution.
اظهر المزيد [+] اقل [-]Geographical and temporal variation of E. coli and norovirus in mussels
2016
Bivalve shellfish may accumulate contaminants of public health concern including pathogenic bacteria and viruses. Microbiological monitoring of production areas is based on faecal coliforms in water in the USA and Escherichia coli in bivalve molluscs in the European Union. E. coli is known to reflect contamination with Salmonella enterica but not necessarily with other human pathogens such as enteric viruses. A structured field study was undertaken at three locations in order to investigate the geographical and temporal variability of E. coli and norovirus (NoV). Total norovirus concentration differed significantly by both sampling site and sampling date. A significant correlation was found between total NoV concentration and E. coli concentration by sample, but not with E. coli in seawater. The results have implications for the establishment of sampling plans for NoV in harvesting areas and potentially also for the approach taken to classification based on faecal indicator bacteria.
اظهر المزيد [+] اقل [-]Influence of petrochemical installations upon PAH concentrations at sites in Western Saudi Arabia
2016
Harrison, Roy M. | Alam, Mohammed S. | Dang, Juan | Basahi, J. | Alghamdi, Mansour A. | Ismail, I.M. | Khoder, M. | Hassan, I.A.
Measurements of 16 polycyclic aromatic hydrocarbon (PAH) congeners (particles and vapour) have been made at three sites over a distance of 230 km on the Red Sea coast of Saudi Arabia. The data have been pooled with an earlier dataset from three sites in the city of Jeddah, with one urban site common to both studies. The concentrations and congener profiles are broadly similar for the two measurement campaigns at the common site. Coefficients of Divergence have been calculated and show more substantial differences between the sites within the city of Jeddah than are found between the sites to the north of the city which emphasises the strong concentration gradients within Jeddah in comparison to those found in the atmosphere of the coastal sites to the north of the city. A sub-set of data corresponding to days on which the air mass travelled from the northwest parallel with the Red Sea coast, hence linking the three sites, showed a progressive reduction in concentrations as the air mass travelled towards the southeast, which is attributed to emissions from a large source area to the northwest of the sampling sites and either atmospheric dilution or chemical reaction accounting for a progressive reduction in concentrations with advection of the air mass. The congener profile is very similar to that identified in earlier work relating to oil refinery emissions and is consistent with the major petrochemical installation at Yanbu contributing substantial emissions to the atmosphere which are advected to downwind sites.
اظهر المزيد [+] اقل [-]Environmental availability of potentially toxic elements in estuarine sediments of the Cananéia–Iguape coastal system, Southeastern Brazil
2016
Tramonte, Keila Modesto | Figueira, Rubens Cesar Lopes | de Lima Ferreira, Paulo Alves | Ribeiro, Andreza Portella | Batista, Miriam Fernanda | Mahiques, Michel Michaelovitch de
The Cananéia–Iguape system is located in a Southeastern Brazilian coastal region, acknowledged by UNESCO as Biosphere Reserve of the Atlantic Rainforest. This system underwent important environmental changes due to the opening of the artificial channel of Valo Grande and by past intensive Pb ore mining activities. In view of this scenario, this study evaluated Cu, Pb and Zn availability in sediments from Cananéia–Iguape system, based on the content associated with the main components of the sediments. Moreover, in order to assess local contamination, the metals' contents were compared to Canadian quality guidelines, the past levels of metals preceding the mining activities and background sediment values. Concerning Cu and Zn in a state of chemical remobilization, both elements would possibly present no harm to the local communities. However, Pb available content exceeded the comparison values in various sampling sites, suggesting the need of monitoring regarding its bioavailability.
اظهر المزيد [+] اقل [-]Reynolds number scaling to predict droplet size distribution in dispersed and undispersed subsurface oil releases
2016
Li, Pu | Weng, Linlu | Niu, Haibo | Robinson, Brian | King, Thomas | Conmy, Robyn | Lee, Kenneth | Liu, Lei
This study was aimed at testing the applicability of modified Weber number scaling with Alaska North Slope (ANS) crude oil, and developing a Reynolds number scaling approach for oil droplet size prediction for high viscosity oils. Dispersant to oil ratio and empirical coefficients were also quantified. Finally, a two-step Rosin-Rammler scheme was introduced for the determination of droplet size distribution. This new approach appeared more advantageous in avoiding the inconsistency in interfacial tension measurements, and consequently delivered concise droplet size prediction. Calculated and observed data correlated well based on Reynolds number scaling. The relation indicated that chemical dispersant played an important role in reducing the droplet size of ANS under different seasonal conditions. The proposed Reynolds number scaling and two-step Rosin-Rammler approaches provide a concise, reliable way to predict droplet size distribution, supporting decision making in chemical dispersant application during an offshore oil spill.
اظهر المزيد [+] اقل [-]Distribution and characteristics of methylmercury in surface sediment in Minamata Bay
2016
Matsuyama, Akito | Yano, Shinichiro | Hisano, Akihiro | Kindaichi, Michiaki | Sonoda, Ikuko | Tada, Akihide | Akagi, Hirokatsu
This study was carried out to evaluate the present-day chemical properties of methylmercury in surface sediment in Minamata Bay where a dredging project was completed 28years ago. Present-day sediment from Minamata Bay consists of sandy silt, and the average loss-on-ignition in surface sediment was 7.0±2.3%. The average methylmercury concentrations in the upper sediment layers were significantly higher than those in the lower sediment layers. Currently, the concentrations in sediments in Minamata Bay do not exceed the Japanese regulatory standard value for mercury. The average concentration of methylmercury in Minamata Bay surface sediment was 1.74±1.0ng/g on a dry weight basis (n=107). The methylmercury concentration in Minamata Bay surface sediment was almost 16 times higher than that in surface sediment from Isahaya Bay surface sediment, which was 0.11±0.045ng/g on a dry weight basis (n=5).
اظهر المزيد [+] اقل [-]Master Plan Jakarta, Indonesia: The Giant Seawall and the need for structural treatment of municipal waste water
2016
van der Wulp, Simon A. | Dsikowitzky, Larissa | Hesse, Karl Jürgen | Schwarzbauer, Jan
In order to take actions against the annual flooding in Jakarta, the construction of a Giant Seawall has been proposed in the Master Plan for National Capital Integrated Coastal Development. The seawall provides a combination of technical solutions against flooding, but these will heavily modify the mass transports in the near-coastal area of Jakarta Bay. This study presents numerical simulations of river flux of total nitrogen and N,N-diethyl-m-toluamide, a molecular tracer for municipal waste water for similar scenarios as described in the Master Plan. Model results demonstrate a strong accumulation of municipal wastes and nutrients in the planned reservoirs to extremely high levels which will result in drastic adverse eutrophication effects if the treatment of municipal waste water is not dealt with in the same priority as the construction of the Giant Seawall.
اظهر المزيد [+] اقل [-]Extreme storm wave influence on sandy beach macrofauna with distinct human pressures
2016
Machado, Phillipe M. | Costa, Leonardo L. | Suciu, Marjorie C. | Tavares, Davi C. | Zalmon, Ilana R.
We evaluated the influence of storm waves on the intertidal community structure of urbanized and non-urbanized areas of a sandy beach on the northern coast of Rio de Janeiro, Brazil. The macrofauna was sampled before (PREV) and after two storm wave events (POEV I; POEV II) in 2013 and 2014. Significant differences in community structure between PREV and POEV I in the urbanized sector demonstrate higher macrofauna vulnerability, and the community recovery within 41days on this scenario of less frequent events in 2013. On the other hand, significant differences in the macrofauna only in the urbanized sector between PREV and POEV II also highlight macrofauna vulnerability and community recovery failure within 42days on this scenario of more frequent storm in 2014. Urbanization and wave height were the variables that most influenced species, indicating that high storm wave events and increasing urbanization synergism are a threat to the macrofauna.
اظهر المزيد [+] اقل [-]Assessing change of environmental dynamics by legislation in Japan, using red tide occurrence in Ise Bay as an indicator
2016
Suzuki, Chika
Tokyo Bay, Ise Bay, and the Seto Inland Sea are the total pollutant load control target areas in Japan. A significant correlation between the incidence of red tides and water quality has been observed in the Seto Inland Sea (Honjo, 1991). However, while red tides also occur in Ise Bay and Tokyo Bay, similar correlations have not been observed. Hence, it is necessary to understand what factors cause red tides to effectively manage these semi-closed systems. This study aims to investigate the relationship between the dynamics of the Red Tide Index and nitrogen regulation as well as phosphorus regulation, even in Ise Bay where, unlike Tokyo Bay, there are few observation items, by selecting a suitable objective variable. The introduction of a new technique that uses the Red Tide Index has revealed a possibility that the total pollution load control has influenced the dynamics of red tide blooms in Ise Bay.
اظهر المزيد [+] اقل [-]Potential ecological risk of heavy metal contamination in sediments and macrobenthos in coastal wetlands induced by freshwater releases: A case study in the Yellow River Delta, China
2016
Li, Ming | Yang, Wei | Sun, Tao | Jin, Yuwan
We investigated the nine heavy metal contents in the sediments and macrobenthos of the Yellow River Delta Wetlands using three experimental areas that received freshwater releases and one reference area that did not. Heavy metal contents, the single-factor contamination index (SFCI), the metal contamination index (MCI), and the biota-sediment accumulation factor (BSAF) were used to evaluate the potential ecological risk and bioaccumulation. We found that As exceeded the national standard value by more than 50%, and that the ranges of SFCI for each metal were generally larger in autumn than in spring. MCI showed no clear pattern, but the BSAF results suggest that Cd bioaccumulates from sediments to macrobenthos. Pollution-resistant species such as Corophium sinense, Chironomus sp., and Einfeldia sp. became dominant in the areas receiving freshwater releases, and provide direct evidence of ecological risk in the wetlands. Our results provide preliminary information to guide managers for ecological risk assessments.
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