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النتائج 1071 - 1080 من 3,199
Human and riverine impacts on the dynamics of biogeochemical parameters in Kwangyang Bay, South Korea revealed by time-series data and multivariate statistics
2015
The successful management of sustainable coastal environments that are beneficial to both humans and marine ecosystems requires knowledge about factors that are harmful to such environments. Here, we investigated seawater nutrient and carbon parameters between 2010 and 2012 in Kwangyang Bay, Korea, a coastal environment that has been exposed to intensive anthropogenic activities. The data were analyzed using cluster and factor analysis. We found that the biogeochemical cycles of nutrients and carbon were determined by river discharge into the bay and biological activity. However, the impacts of these factors varied both spatially and seasonally. During the past 10years, nutrient loads from the river and industrial complexes to the bay have decreased. The impacts of this decrease are visible in the phosphate concentration, which has fallen to a third of its initial value. We also examined the potential role of atmospheric nitrogen deposition in nitrogen cycling in the study area.
اظهر المزيد [+] اقل [-]Determination of mercury and vanadium concentration in Johnius belangerii (C) fish in Musa estuary in Persian Gulf
2015
Fard, Neamat Jaafarzadeh Haghighi | Ravanbakhsh, Maryam | Ramezani, Zahra | Ahmadi, Mehdi | Angali, Kambiz Ahmadi | Javid, Ahmad Zare
The main aim of this study was to determine the concentrations of mercury and vanadium in Johnius belangerii (C) fish in the Musa estuary. A total of 67 fishes were caught from the Musa estuary during five intervals of 15days in the summer of 2013. After biometric measurements were conducted, the concentrations of mercury and vanadium were measured in the muscle tissue of fish using a direct method analyzer (DMA) and a graphite furnace atomic absorption spectrophotometer, respectively. The mean concentration of mercury and vanadium in the muscle tissue of fish was 3.154±1.981 and 2.921±0.873mg/kg w.w, respectively. The generalized linear model (GLM) analysis showed a significantly positive relationship among mercury concentration, length, and weight (P=0.000). In addition, there was a significantly negative relationship between vanadium concentration and fish length (P=0.000). A reverse association was found between concentrations of mercury and vanadium. Mercury concentration exceeded the allowable standards of the Environmental Protection Agency (EPA), the World Health Organization (WHO), and the Food and Drug Administration (FDA) in J. belangerii (C).
اظهر المزيد [+] اقل [-]Seasonal and interannual variations in whole-ecosystem isoprene and monoterpene emissions from a temperate mixed forest in Northern China
2015
Bai, Jianhui | Guenther, Alex | Turnipseed, Andrew | Duhl, Tiffany
Contributed Measurements of BVOC emissions, meteorological parameters, and solar radiation were carried out in a temperate forest, China during the summer seasons in 2010 and 2011. Terpenoid emissions were measured using the Relaxed Eddy Accumulation (REA) technique on an above-canopy tower. Isoprene contributed 79.1% and 82.0% of terpenoid emissions in 2010 and 2011 summer. The monoterpene emissions were dominated by α–pinene, contributing 6.3% and 12.2% of the total terpenoid emissions in 2010 and 2011 summer. Terpenoid emissions exhibited strong diurnal variations. Isoprene and monoterpene emissions maxima typically occurred a few hours after the noon PAR peak and coincided with the daily temperature maximum. During 2011 summer, the mean isoprene emission flux (mg m–2 h–1) was 0.889, mean total monoterpene emission flux was 0.143. Emission factors, representing the emission expected at a temperature of 30 °C, for this site were 0.32mg m–2 h–1 for total monoterpenes and 4.3mg m–2 h–1 for isoprene. The observations were used to evaluate the isoprene and monoterpene emission magnitude and variability predicted by the MEGANv2.1 model. Canopy scale isoprene and monoterpene emission factors based on these observations fall within the range of emission factors assigned to locations within 50km of the site by the MEGANv2.1 emission model. When using the site specific landcover data for the site, the measured emission factors are 12% for isoprene and 20% for monoterpenes lower than the MEGANv2.1 emission factors. MEGANv2.1 predicts that variations in light intensity should result in significant changes in isoprene emissions during the study but this was not evident in the observations. Observed diurnal, seasonal and interannual variations in isoprene and monoterpene emissions were strongly correlated with air temperature which was the dominant driving variable for MEGANv2.1 during the study period. The observed temperature response for isoprene and monoterpenes is similar to the temperature sensitivity of the MEGANv2.1 response functions.
اظهر المزيد [+] اقل [-]The composition of PM1 and PM2.5 samples, metals and their water soluble fractions in the Bologna area (Italy)
2015
Sarti, Elena | Pasti, Luisa | Rossi, Mauro | Ascanelli, Monica | Pagnoni, Antonella | Trombini, Monica | Remelli, Maurizio
In this study the metal composition of PM1 and PM2.5 samples collected in the surroundings of a municipal incinerator located in a suburban–farming area, less than 10 km away from Northeast of Bologna (Italy) was investigated. Seven out of eight monitoring stations were installed in a domain of 8x9 km2 around the incinerator plant; the eighth station was placed inside the urban area of Bologna. The coordinates of four monitoring stations were selected on the basis of a preliminary study by using a dispersion model. Eleven metals (Al, Sb, As, Cd, Fe, Mn, Ni, Pb, Cu, V, Zn) were quantified in both the filter acid–digests and in the water extracts. The PM2.5 collected in all the sites of the domain were highly correlated with exception of the urban site. The daily average metal concentrations in summer were 1.84% and 1.14% for PM2.5 and PM1 respectively, indicating that fine particles are less enriched in metals. Fe, Al and Zn were the most abundant elements, and they represented about the 80% of the total amount of the analyzed ones. The average water soluble metal compositions were 0.71% and 0.41% for PM2.5 and PM1 respectively. In the sites of the suburban–farming studied area the Principal Component Analysis (PCA) and Cluster Analysis revealed differences between water soluble metal compositions in PM1 and PM2.5. The urban sites were characterized by lower total and soluble metals contents than the other PM2.5 stations installed around the incinerator plant. However, no noticeable difference in the concentrations of metals in the particulate matter between the sites chosen as maxima of incinerator emissions and the control sites was observed.
اظهر المزيد [+] اقل [-]Benthic foraminifera as indicators of habitat change in anthropogenically impacted coastal wetlands of the Ebro Delta (NE Iberian Peninsula)
2015
Benito, Xavier | Trobajo, Rosa | Ibàñez, Carles | Cearreta, Alejandro | Brunet, Manola
Present-day habitats of the Ebro Delta, NE Iberian Peninsula, have been ecologically altered as a consequence of intensive human impacts in the last two centuries (especially rice farming). Benthic foraminiferal palaeoassemblages and sediment characteristics of five short cores were used to reconstruct past wetland habitats, through application of multivariate DCA and CONISS techniques, and dissimilarity coefficients (SCD). The timing of environmental changes was compared to known natural and anthropogenic events in order to identify their possible relationships. In deltaic wetlands under altered hydrological conditions, we found a decrease in species diversity and calcareous-dominated assemblages, and a significant positive correlation between microfaunal changes and organic matter content. Modern analogues supported palaeoenvironmental interpretation of the recent evolution of the Delta wetlands. This research provides the first recent reconstruction of change in the Ebro Delta wetlands, and also illustrates the importance of benthic foraminifera for biomonitoring present and future conditions in Mediterranean deltas.
اظهر المزيد [+] اقل [-]Assessing water quality by ratio of the number of dominant bacterium species between surface/subsurface sediments in Haihe River Basin
2015
Ke, Xin | Wang, Chunyong | Jing, Debing | Zhang, Yun | Zhang, Haijun
Sedimentary microorganisms can be used as a sensitive indicator of integrated aquatic environment quality assessment and indicate long-term water quality or toxicity. According to the Chinese National Standards of GB 3838-2002 and GB 18918-2002, the comprehensive water quality in Haihe River Basin has been described. Results showed that the comprehensive water quality in 6 sites, 4 sites, and 20 sites were good, bad, and medium. Furthermore, 162 dominant bacterial species were identified in surface and subsurface sediments in the 30 sampling sites. As revealed by two initial models constructed by logistic regression, the comprehensive water quality exhibited a pattern from good to bad as the ratio of the number of dominant bacterial species in surface sediments to that in subsurface sediments increased from 1 to 2.1. This finding possibly bridged a traditional gap between aquatic microbe indicators and water quality assessment or monitoring techniques.
اظهر المزيد [+] اقل [-]Concentrations of trace elements in a rare and threatened coastal shark from the Arabian Gulf (smoothtooth blacktip Carcharhinus leiodon)
2015
Moore, Alec B.M. | Bolam, Thi | Lyons, Brett P. | Ellis, Jim
Kuwait’s waters are one of only two locations where the smoothtooth blacktip shark Carcharhinus leiodon is known to occur. Concentrations of 11 trace elements were analysed in five juvenile and two adult specimens of this coastal predator. Concentrations of lead in muscle increased with length, whilst manganese concentration decreased. Arsenic concentrations in muscle were among the highest reported in elasmobranchs, and the concentration in the liver increased significantly in relation to length. In comparison to published literature, concentrations of manganese (liver), lead (muscle) and iron (muscle and liver) were high. Mercury concentrations in the muscle exceeded European Food Safety Authority limits and were among the highest reported in any elasmobranch. Concentrations of selenium, which may inhibit mercury toxicity, were also high. These results and previous studies indicate that potentially hazardous levels of mercury and other contaminants may occur in sharks in this region, adding further stressors to these vulnerable populations.
اظهر المزيد [+] اقل [-]Merits of partial shielding in dumping sediment spoils
2015
Jensen, Jacob Hjelmager | Saremi, Sina | Jimenez, Carlos | Hadjioannou, Louis
The commonly adopted method of dumping dredge spoil at sea using split-hull barges leads to considerable sediment loss to the water column and a subsequent dispersion of fine material that can pose a risk to sensitive “downstream” habitats such as coral reefs. Containing sediment loads using stitched closed geotextile bags is practiced for minimizing loss of contaminated sediment, but is expensive in terms of operational efficiency. Following promising observations from initial laboratory trials, the plunging of partially shielded sediment loads, released on open sea, was studied. The partial shielding was achieved with rigid, open containers as well as flexible, open bags. The loss of sediment from these modes of shielding was measured, and it was observed that even limited and unstitched shielding can be effective in debilitating the entrainment of water into the descending load. In particular, long-sleeved flexible bags practically self-eliminated the exposure of the load and thus losses.
اظهر المزيد [+] اقل [-]Fringing reefs exposed to different levels of eutrophication and sedimentation can support similar benthic communities
2015
Rouzé, H. | Lecellier, G. | Langlade, M.J. | Planes, S. | Berteaux-Lecellier, V.
Benthic communities are sensitive to anthropogenic disturbances which can result in changes in species assemblages. A spatio-temporal survey of environmental parameters was conducted over an 18-month period on four different fringing reefs of Moorea, French Polynesia, with unusual vs. frequent human pressures. This survey included assessment of biological, chemical, and physical parameters. First, the results showed a surprising lack of a seasonal trend, which was likely obscured by short-term variability in lagoons. More frequent sampling periods would likely improve the evaluation of a seasonal effect on biological and ecological processes. Second, the three reef habitats studied that were dominated by corals were highly stable, despite displaying antagonistic environmental conditions through eutrophication and sedimentation gradients, whereas the reef dominated by macroalgae was relatively unstable. Altogether, our data challenge the paradigm of labelling environmental parameters such as turbidity, sedimentation, and nutrient-richness as stress indicators.
اظهر المزيد [+] اقل [-]Micro–scale simulation of atmospheric emissions from power–plant stacks in the Po Valley
2015
Ghermandi, Grazia | Fabbi, Sara | Zaccanti, Marco | Bigi, Alessandro | Teggi, Sergio
The atmospheric dispersion of the NOX plume that will be emitted from a new power–plant, at present under installation, was simulated at micro–scale with Micro–Swift–Spray (MSS) Model. The plant will be constructed in a residential urban area in the town of Modena (Po Valley, Northern Italy), where low wind speeds and thermal inversions are quite frequent. Simulation results point out a different behavior of urban canopy in influencing the 3D dispersion patterns among urban obstacles, according to atmospheric mixing conditions: in case of moderate wind events, urban canyon phenomena may occur with a consequent increasing of NOX concentration gradients among buildings, while with low winds the near–field influence of the buildings emphasizes pollutant accumulation. The MSS simulated NOX concentrations result always much lower than the regulatory limits for air quality. The comparison of simulation results with measured concentration data for NOX shows the importance of micro–scale dispersion modeling to perform an accurate and reliable assessment of meteorological condition effects on pollutant distribution, and the ability of MSS in providing reliable simulations of atmospheric dispersion.
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