خيارات البحث
النتائج 1531 - 1540 من 4,241
Adaption of Ulva pertusa to multiple-contamination of heavy metals and nutrients: Biological mechanism of outbreak of Ulva sp. green tide
2017
Ge, Changzi | Yu, Xiru | Kan, Manman | Qu, Chunfeng
The multiple-contamination of heavy metals and nutrients worsens increasingly and Ulva sp. green tide occurs almost simultaneously. To reveal the biological mechanism for outbreak of the green tide, Ulva pertusa was exposed to seven-day-multiple-contamination. The relation between pH variation (VpH), Chl a content, ratio of (Chl a content)/(Chl b content) (Rchla/chlb), SOD activity of U. pertusa (ASOD) and contamination concentration is VpH=1.72±0.38+1.68±0.72×10−4×Cammonia2 (p<0.05), Cchla=0.88±0.09−0.01±0.00×CCd (p<0.05), Rchla/chlb=0.72±0.04−0.35±0.08×10−4×CCd2 (p<0.05), and ASOD=25.64±2.35−0.41±0.09×10−2×CZn2+0.54±0.10×CZn (p<0.05), respectively. Cammonia, CCd and CZn is concentration of ammonia, Cd2+ and Zn2+, respectively. Comparing the contamination concentrations of seawaters where Ulva sp. green tide occurred and the contamination concentrations set in the present work, U. pertusa can adapt to multiple-contaminations in these waters. Thus, the adaption to multiple-contamination may be one biological mechanism for the outbreak of Ulva sp. green tide.
اظهر المزيد [+] اقل [-]Homing pigeons as a biomonitor for atmospheric PAHs and PCBs in Guangzhou, a megacity in South China
2017
Pei, Yuanyuan | Halbrook, Richard S. | Li, Huizhen | Yau, Ching
The occurrence of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl (PCBs) in urban atmosphere in Guangzhou, China were assessed using homing pigeons as a biomonitor. Contaminant concentrations in lung were significantly higher than those in liver and fat, indicating chemical uptake was mainly through respiratory route. Tricyclic PAHs and low chlorinated PCBs dominated composition of PAHs and PCBs in homing pigeons, similar as their composition in local atmosphere. Different age-dependent bioaccumulation patterns were noted for PAHs and PCBs. For 1-year old homing pigeons, higher levels of PAHs and PCBs in lung and liver tissues were probably ascribed to more intense flying than 5- and 10-year groups. Fat concentrations of PCBs were greater in aged pigeons than 1-year old pigeons, but PAH concentrations in fat slightly decreased in aged pigeons because of relatively fast biotransformation. Overall, homing pigeons could serve as a suitable biomonitor for urban atmospheric contaminants in coastal cities.Homing pigeons could serve as a good biomonitor for PAHs and PCBs in urban atmosphere, yet different biotransformation potential of the chemicals caused different bioaccumulation patterns in pigeon fat.
اظهر المزيد [+] اقل [-]A novel hybrid-Garch model based on Arima and SVM for PM2.5 concentrations forecasting
2017
Wang, Ping | Zhang, Hong | Qin, Zuodong | Zhang, Guisheng
Air-quality forecasting is difficult because air quality time series are heterogeneous, consisting of one-dimension series data and multi-dimension panel data. Therefore, a hybrid forecasting model with both linear and nonlinear models may be appropriate to represent the complex behavior of a heterogeneous time series data set. In this paper, a new hybrid-Garch (Generalized Autoregressive Conditional Heteroskedasticity) methodology is proposed in order to integrate the individual forecasting models of the ARIMA (Autoregressive Integrated Moving Average) and SVM(Support Vector Machine). The hybrid-Garch approach for time series prediction is tested by 10-day hourly PM2.5 concentrations data including linear and non-linear, in Shenzhen, China. Empirical results from six station data sets indicate that: 1) the PM2.5 concentrations of Shenzhen experiences a regular fluctuation during the 24 h of the whole day with the peak value in working hours due to factory and vehicle emissions. 2) Spatial difference of PM2.5 concentrations is not noticeable because of the geographical and meteorological conditions. 3) The proposed hybrid model generates a more reliable and accurate forecast capability. 4) The proposed hybrid model analyses the time series data with possibly conditional heteroscedasticity characteristics and estimates the variance for the volatility of the PM2.5 concentrations.
اظهر المزيد [+] اقل [-]Modelling dispersal of radioactive contaminants in Arctic waters as a result of potential recovery operations on the dumped submarine K-27
2017
Karcher, M. | Hosseini, A. | Schnur, R. | Kauker, F. | Brown, J.E. | Dowdall, M. | Strand, P.
Of the wide variety of dumped objects containing radioactive materials in the Arctic seas, the submarine K-27 constitutes a major risk due to the large amount of highly enriched uranium onboard and its location in shallow waters. As the matter of potential operations involving raising of the submarine have entered the public arena, a priori assessment of the contamination in the Arctic marine environment that could result after a possible accident during such operations is a matter of some interest. The dispersion of contaminants within the Arctic has been assessed using a large scale hydrodynamic model for a series of plausible accident scenarios and locations under different oceanographic regimes. Results indicate that, depending primarily on the nature of a release (i.e. instantaneous or continuous), large areas of the Arctic marine environment will exhibit contamination to varying degrees.
اظهر المزيد [+] اقل [-]Fast assessment of bioaccessible metallic contamination in marine sediments
2017
Terán-Baamonde, J. | Carlosena, A. | Soto-Ferreiro, R.M. | Andrade, J.M. | Prada, D.
A fast (16min) procedure to assess the bioaccessible metallic fraction of Cd, Cr, Cu, Ni, Pb and Zn simultaneously extracted (SEM) from marine sediments plus an indirect approach to determine acid volatile sulfides (AVS) are presented. For the extraction process magnetic agitation was compared with ultrasonic stirring (using a bath and a probe), and several stirring times were assayed. The proposed SEM procedure uses an ultrasonic probe and 1mL of HCl. It dramatically minimizes the turnaround time and the residues. AVS were evaluated as the difference between the amounts of sulphur in the solid residue after the extraction and total sulphur in the original sample. These procedures are fast, easy to implement and cost-effective to assess the potential risk posed by metals in marine sediments. They were tested using several CRMs and applied to sediments from two Galician Rias (NW Spain); their SEM-AVS differences indicated no biological risk.
اظهر المزيد [+] اقل [-]Remote sensing and water quality indicators in the Korean West coast: Spatio-temporal structures of MODIS-derived chlorophyll-a and total suspended solids
2017
Kim, Hae-Cheol | Son, Seunghyun | Kim, Yong Hoon | Khim, Jong Seong | Nam, Jungho | Chang, Won Keun | Lee, Jung-Ho | Lee, Chang Hee | Ryu, Jongseong
The Yellow Sea is a shallow marginal sea with a large tidal range. In this study, ten areas located along the western coast of the Korean Peninsula are investigated with respect to remotely sensed water quality indicators derived from NASA MODIS aboard of the satellite Aqua. We found that there was a strong seasonal trend with spatial heterogeneity. In specific, a strong six-month phase-lag was found between chlorophyll-a and total suspended solid owing to their inversed seasonality, which could be explained by different dynamics and environmental settings. Chlorophyll-a concentration seemed to be dominantly influenced by temperature, while total suspended solid was largely governed by local tidal forcing and bottom topography. This study demonstrated the potential and applicability of satellite products in coastal management, and highlighted find that remote-sensing would be a promising tool in resolving orthogonality of large spatio-temporal scale variabilities when combining with proper time series analyses.
اظهر المزيد [+] اقل [-]Measurements of TSP, PM10, PM2.5, BC, and PM chemical composition from an urban residential location in Nepal
2017
Shakya, Kabindra M. | Peltier, Richard E. | Shrestha, Hasana | Byanju, Rejina M.
Particulate matter (PM2.5, PM10, and TSP), black carbon (BC), and PM constituent components were measured at a location in an urban residential neighborhood of Kathmandu Valley, Nepal. PM2.5, TSP, and BC were measured during winter, and PM2.5, PM10, and their chemical composition was measured during the summer monsoon periods in 2014. Both indoor and outdoor measurements were collected during the winter season. There was a distinct seasonal profile of PM2.5 concentration, with the 24-hour mean larger during winter (76 ± 18 μg/m3) than monsoon (21 ± 8 μg/m3). This site was located approximately 15 m above the street, but was still influenced by roadway combustion sources indicated by large BC concentration (15 ± 3 μgC/m3 during winter) and large rush hour PM and BC peaks. Two rush hour peaks of PM and BC were observed during morning and evening. Indoor and outdoor PM2.5 and BC concentration measured during winter were similar suggesting the heavy influence of outdoor traffic activities on such indoor environments. Mean 24-hour TSP during winter and PM10 during monsoon was 109 μg/m3 and 34 μg/m3, respectively. PM2.5 accounted for 75% of TSP during winter and 61% of PM10 during monsoon indicating a high degree of influence by PM2.5 sources. Sulfate, ammonium, and calcium were the dominant components of water-soluble ions, and silica, iron, aluminum, and barium were the major elements in both PM10 and PM2.5 during monsoon indicating the most important emission sources as traffic emissions and road/soil/construction-related dust.
اظهر المزيد [+] اقل [-]Drilling discharges reduce sediment reworking of two benthic species
2017
Trannum, Hilde Cecilie
Effects of water-based drill cuttings on sediment reworking activity were studied on two important benthic bioturbators (the bivalve Abra segmentum and the brittle star Amphiura filiformis) using thin aquaria, fluorescent-dyed sediment particles (luminophores), time lapse photography and image analysis. In the present context, sediment reworking activity was measured as maximum mixing depth and total amount of luminophores transported below the sediment-water interface. There was a significant reduction in the amount of downward transported luminophores in drill cuttings treatments compared to controls with added natural sediments for both species, which also was true regarding maximum mixing depth for A. segmentum. Further, A. filiformis showed a clearly delayed burrowing of luminophores in the drill cuttings treatment compared to control. To conclude, the study showed that water-based drill cuttings have the potential to reduce sediment reworking. Further, it is evidenced that water-based drill cuttings not only cause burial effects.
اظهر المزيد [+] اقل [-]Modulation of Spartina densiflora plant growth and metal accumulation upon selective inoculation treatments: A comparison of gram negative and gram positive rhizobacteria
2017
Paredes-Páliz, Karina I. | Mateos-Naranjo, Enrique | Doukkali, Bouchra | Caviedes, Miguel A. | Redondo-Gómez, Susana | Rodríguez-Llorente, Ignacio D. | Pajuelo, Eloísa
Metal contamination of estuaries is a severe environmental problem, for which phytoremediation is gaining momentum. In particular, the associations between halophytes-autochthonous rhizobacteria have proven useful for metal phytostabilization in salt marshes. In this work, three bacterial strains (gram-negative and gram-positive) were used for Spartina densiflora inoculation. All three bacteria, particularly Pantoea strains, promoted plant growth and mitigated metal stress on polluted sediments, as revealed from functionality of the photosynthetic apparatus (PSII) and maintenance of nutrient balance. Pantoea strains did not significantly affect metal accumulation in plant roots, whereas the Bacillus strain enhanced it. Metal loading to shoots depended on particular elements, although in all cases it fell below the threshold for animal consumption. Our results confirm the possibility of modulating plant growth and metal accumulation upon selective inoculation, and the suitability of halophyte-rhizobacteria interactions as biotechnological tools for metal phytostabilization in salt marshes, preventing metal transfer to the food chain.
اظهر المزيد [+] اقل [-]Distribution and source of organic matter in surface sediment from the muddy deposit along the Zhejiang coast, East China Sea
2017
Xu, Gang | Liu, Jian | Hu, Gang | Jonell, Tara N. | Chen, Lilei
To constrain organic matter compositions and origins, elemental (TOC, TN, C/N) and stable carbon (δ13C) and nitrogen isotope (δ15N) compositions are measured for surface sediments collected from muddy deposit along the Zhejiang coast, East China Sea. The results showed that the TOC, TN, C/N, δ13C, and δ15N were 0.19–0.67%, 0.03–0.09%, 6.76–9.22, −23.43 to −20.26‰, and 3.93–5.27‰, respectively. The δ13C values showed that the mixing inputs of terrigenous and marine organic matter generally dominated sedimentary organic matter in the west part, and the sedimentary organic matters were mainly influenced by the marine organic matter in the east part of the study area. A stable carbon isotope two end member mixing model estimates ~38% terrestrial -derived and ~62% marine-derived inputs to sedimentary organic matter. Microbial mineralization strongly controls δ15N values, and therefore cannot be used to identify the provenance of organic matter for the Zhenjiang coast.
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