خيارات البحث
النتائج 1611 - 1620 من 4,309
Macrobenthic communities in Hong Kong waters: Comparison between 2001 and 2012 and potential link to pollution control النص الكامل
2017
Wang, Zhi | Leung, Kenneth M.Y. | Li, Xinzheng | Zhang, Tong | Qiu, Jian-Wen
Macrobenthic communities in 2001 and 2012 were compared across the marine environment of Hong Kong based on sediment grab samples collected from 28 stations. CLUSTER analysis showed in both surveys that the stations could be divided into four groups at 20% faunal similarity. However, there were notable changes in the macrobenthic community structure between 2001 and 2012 in three focal areas of pollution control (i.e., Victoria Harbour, Deep Bay and Tolo Harbour). The potential link between macrobenthos and pollution abatement measures, and the contributions of environmental conditions to the differential responsiveness of macrobenthos were explored. Notably, a reduction in nutrient input to the eastern part of Victoria Harbour might have led to recovery of benthic communities therein.
اظهر المزيد [+] اقل [-]A review of brominated flame retardants in the environment with emphasis on atmospheric levels, knowledge and information gaps in the African continent النص الكامل
2017
Katima, Zainab | Okonkwo, Jonathan O. | Daso, Adegbenro P.
Brominated flame retardants (BFRs) are chemicals that are now omnipresent in the environment and have been detected in different matrices from different parts of the world.They are semivolatile organic compounds (SVOCs), hence they partition between air, water, soil and sediment. Atmospheric long range transport (LRT) is commonly considered the swiftest route for SVOCs to reach remote environments. As a results, the Stockholm Convention on Persistent Organic Pollutants (POPs) advocates air monitoring as a key measure to assess the effectiveness of global control initiatives. There is little information of atmospheric BFR levels in the African continent, which makes it impossible to understand the regional as well as global perspective of these pollutants in the atmosphere. The aim of this review is therefore to establish scientific reasons to explain why it is necessary to have atmospheric research in Africa, and provide research gaps that need to be considered in further studies in order to better understand these pollutants in the atmosphere.To date there are about 57 published studies on BFRs in different matrices in various countries of the African continent, out of which, only three have concentrated on the atmosphere. The amounts are not as high as detected in other regions but are likely to increase due to the fact that the continent is developing at a fast rate thus an anticipated increase in BFRs use. The review therefore provides different recommendations which all clearly develop a foundation of the necessity of air monitoring of BFRs in the African continent.
اظهر المزيد [+] اقل [-]Polycyclic aromatic hydrocarbons (PAHs) in wild marine organisms from South China Sea: Occurrence, sources, and human health implications النص الكامل
2017
Ke, Chang-Liang | Gu, Yang-Guang | Liu, Qi | Li, Liu-Dong | Huang, Hong-Hui | Cai, Nan | Sun, Zhi-Wei
Concentrations of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) were measured in 15 marine wild organism species from South China Sea. The concentration (dry weight) of 16 PAHs ranged from 94.88 to 557.87ng/g, with a mean of 289.86ng/g. The concentrations of BaP in marine species were no detectable. The composition of PAHs was characterized by the 2- and 3-ring PAHs in marine species, and NA, PHE and FA were the dominant constituents. PAHs isomeric ratios indicated PAHs mainly originated from grass, wood and coal combustion, and petroleum. The human health risk assessment based on the excess cancer risk (ECR) suggested the probability of PAHs posing carcinogenic risk to human beings with consumption of marine organisms were negligible (probability<1×10−6).
اظهر المزيد [+] اقل [-]Investigating the fate and transport of fecal coliform contamination in a tidal estuarine system using a three-dimensional model النص الكامل
2017
Chen, Wei-Bo | Liu, Wenzheng
A three-dimensional fecal coliform transport model was developed and incorporated into a hydrodynamic and suspended sediment transport model to better understand the microbiological water quality in the tidal Tamsui River estuarine system of northern Taiwan, which includes three main tributaries: Dahan River, Xindian River, and Keelung River. The model was calibrated using the water level, salinity, suspended sediment concentration, and fecal coliform data measured in 2010. The predictive skill, a statistical approach, is used to evaluate the model performance. There was quantitatively good agreement between the simulation and measurement results. Further, the calibrated model underwent model sensitivity analysis by varying the model parameters which include the settling velocity, darkness decay rate, partition coefficient, and fecal coliform concentration in the sediment bed. The results indicated that the settling velocity played the most important role in affecting fecal coliform concentrations followed by partition coefficient, darkness decay rate, and fecal coliform concentration in the sediment bed. The model was also used to investigate the effects of salinity and suspended sediment on fecal coliform contamination. The salinity module was excluded in the simulations, resulting in an increase of fecal coliform concentration. However the effect of salinity on fecal coliform concentration is minor. If the suspended sediment transport was excluded in the simulations, the predicted results of fecal coliform concentration decrease to be underestimated the measured data. The modeling results revealed that the inclusion of the suspended sediment transport model in the simulations was of crucial importance because the fecal coliform concentrations were significantly influenced by the suspended sediment concentration in the estuarine system.
اظهر المزيد [+] اقل [-]Stormwater runoff plumes in the Southern California Bight: A comparison study with SAR and MODIS imagery النص الكامل
2017
Holt, Benjamin | Trinh, Rebecca | Gierach, Michelle M.
Stormwater runoff is the largest source of pollution in the Southern California Bight (SCB), resulting from untreated runoff and pollutants from urban watersheds entering the coastal waters after rainstorms. We make use of both satellite SAR and MODIS-Aqua ocean color imagery to examine two different components of runoff plumes, the surface slick and the sediment discharge. We expand on earlier satellite SAR studies by examining an extensive collection of multi-platform SAR imagery, spanning from 1992 to 2014, that provides a more comprehensive view of the plume surface slick characteristics, illustrated with distribution maps of the extent and flow direction of the plumes. The SAR-detected surface plumes are compared with coincident rain and runoff measurements, and with available measured shoreline fecal bacteria loads. We illustrate differences in the detection of SAR surface plumes with the sediment-related discharge plumes derived from MODIS imagery. A conceptual satellite stormwater runoff monitoring approach is presented.
اظهر المزيد [+] اقل [-]Assessment of microplastic-sorbed contaminant bioavailability through analysis of biomarker gene expression in larval zebrafish النص الكامل
2017
Sleight, Victoria A. | Bakir, Adil | Thompson, Richard C. | Henry, Theodore B.
Microplastics (MPs) are prevalent in marine ecosystems. Because toxicants (termed here “co-contaminants”) can sorb to MPs, there is potential for MPs to alter co-contaminant bioavailability. Our objective was to demonstrate sorption of two co-contaminants with different physicochemistries [phenanthrene (Phe), log10Kow=4.57; and 17α-ethinylestradiol (EE2), log10Kow=3.67] to MPs; and assess whether co-contaminant bioavailability was increased after MP settlement. Bioavailability was indicated by gene expression in larval zebrafish. Both Phe and EE2 sorbed to MPs, which reduced bioavailability by a maximum of 33% and 48% respectively. Sorption occurred, but was not consistent with predictions based on co-contaminant physicochemistry (Phe having higher log10Kow was expected to have higher sorption). Contaminated MPs settled to the bottom of the exposures did not lead to increased bioavailability of Phe or EE2. Phe was 48% more bioavailable than predicted by a linear sorption model, organism-based measurements therefore contribute unique insight into MP co-contaminant bioavailability.
اظهر المزيد [+] اقل [-]Plankton resting stages in recent sediments of Haifa port, Israel (Eastern Mediterranean) - Distribution, viability and potential environmental consequences النص الكامل
2017
Rubino, Fernando | Belmonte, Manuela | Galil, Bella S.
Resting stages of plankton were sampled in the surficial sediments in the port of Haifa, Israel, on the eve of a major port enlargement project. We recorded the structure of the assemblages and examined their relationship with different environments within the port. Our findings reveal a remarkably high diversity coupled with low density and the highest number of oligotrich ciliate cyst types recorded from marine sediments. Near the eutrophic and highly polluted zone of the Kishon estuary ciliates were more abundant than elsewhere in the port, whereas dinoflagellates' abundance was reduced, and these trends held true both for full and empty cysts. Some harmful or potentially toxic species, such as Scrippsiella acuminata, were widespread in the port. The toxigenic species include Alexandrium minutum, Gymnodinium uncatenatum and Lingulodinium polyedrum. Active cells of the unarmoured, bloom-forming Akashiwo sanguinea were identified in the cultures obtained from the incubated sediments.
اظهر المزيد [+] اقل [-]Individual and population indicators of Zostera japonica respond quickly to experimental addition of sediment-nutrient and organic matter النص الكامل
2017
Han, Qiuying | Soissons, Laura M. | Liu, Dongyan | van Katwijk, Marieke M. | Bouma, Tjeerd J.
A manipulative field experiment was designed to investigate the effects of sediment-nutrients and sediment-organic matters on seagrasses, Zostera japonica, using individual and population indicators. The results showed that seagrasses quickly responded to sediment-nutrient and organic matter loading. That is, sediment-nutrients positively impacted on seagrasses by increasing N content of leaves and roots, leaf length and belowground biomass. Sediment-organic matter loading lowered N content of seagrass leaves and belowground biomass. Negative effects of organic matter loading were aggravated during nutrient loading, by decreasing N content of leaves, P content of roots, leaf width, shoot number in the middle period of the experiment, increasing C/N ratio of leaves, C/P and N/P ratio of roots and above to belowground biomass ratio of seagrasses. Consequently, Z. japonica could be considered as a fast indicator to monitor seagrass ecosystem status in the eutrophic areas and facilitate to interpreting the response of seagrasses to multiple stressors.
اظهر المزيد [+] اقل [-]Multiple-input–multiple-output general regression neural networks model for the simultaneous estimation of traffic-related air pollutant emissions النص الكامل
2017
Antanasijević, Davor | Pocajt, Viktor | Perić-Grujić, Aleksandra | Ristic, Mirjana
Traffic-related air pollutant emissions have become a global environmental problem, especially in urban areas. The estimation of pollutant emissions is based on complex models that require the use of detailed travel-activity data, which is often unavailable and in particular, in developing countries. In order to overcome this issue, an alternative multiple-input–multiple-output general regression neural network model, based on basic socioeconomic and transport related indicators, is proposed for the simultaneous prediction of sulphur oxides (SOx), nitrogen oxides (NOx), ammonia (NH3), non-methane volatile organic compounds (NMVOC) and particulate matter emissions at the national level. The best model, created using only six inputs, has MAPE (mean absolute percentage error) values on testing in the range of 12–15% for all studied pollutants, except NMVOC (MAPE = 21%). The obtained predictions for SOx, NH3 and PM10 emissions were in good agreement with the reported emissions (R2 ≥ 0.93), while the predictions for NOx and NMVOC are somewhat less accurate (R2 ≈ 0.85). It can be concluded that the presented ANN approach can offer a simple and relatively accurate alternative method for the estimation of traffic-related air pollutant emissions.
اظهر المزيد [+] اقل [-]OSPAR standard method and software for statistical analysis of beach litter data النص الكامل
2017
Schulz, Marcus | van Loon, Willem | Fleet, David M. | Baggelaar, Paul | van der Meulen, Eit
The aim of this study is to develop standard statistical methods and software for the analysis of beach litter data. The optimal ensemble of statistical methods comprises the Mann-Kendall trend test, the Theil-Sen slope estimation, the Wilcoxon step trend test and basic descriptive statistics. The application of Litter Analyst, a tailor-made software for analysing the results of beach litter surveys, to OSPAR beach litter data from seven beaches bordering on the south-eastern North Sea, revealed 23 significant trends in the abundances of beach litter types for the period 2009–2014. Litter Analyst revealed a large variation in the abundance of litter types between beaches. To reduce the effects of spatial variation, trend analysis of beach litter data can most effectively be performed at the beach or national level. Spatial aggregation of beach litter data within a region is possible, but resulted in a considerable reduction in the number of significant trends.
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