خيارات البحث
النتائج 801 - 810 من 2,459
Marine debris in bottom trawl catches and their effects on the selectivity grids in the north eastern Mediterranean
2014
Eryaşar, Ahmet Raif | Özbilgin, Hüseyin | Gücü, Ali Cemal | Sakınan, Serdar
In this study composition of marine debris and their blocking potential on the selectivity grid systems deployed on demersal trawls were investigated in the north eastern Mediterranean. For this, a total of 132hauls were examined in two fishing season between 20 September 2010 and 19 February 2012. Results showed that plastic items were the most abundant debris (73% in terms of weight) and they were followed by metals (10%). Because of plastics and packing debris, it is highly probable that grids may have been blocked in 85% of trawl hauls. The bathymetric and geographical variability in the quantity of debris were evaluated, and concluded that particularly in some areas where direction of currents and bottom topography favor deposition, such devices may easily be rendered ineffective by the plastics and packing debris in particular. To solve this problem, several solution proposals are submitted.
اظهر المزيد [+] اقل [-]Chemical characterization of coarse particulate matter in the Desert Southwest – Pinal County Arizona, USA
2014
Clements, Andrea L. | Fraser, Matthew P. | Upadhyay, Nabin | Herckes, Pierre | Sundblom, Michael | Lantz, Jeffrey | Solomon, Paul A.
The Desert Southwest Coarse Particulate Matter Study was undertaken to further our understanding of ambient concentrations and the composition of fine and coarse particles in rural, arid environments. Sampling was conducted in Pinal County, Arizona between February 2009 and February 2010. The goals of this study were to: (1) chemically characterize the coarse and fine fraction of the ambient particulate matter in terms of mass, ions, elements, bulk organic and elemental carbon; (2) examine the temporal and spatial variability of particles within the area using a series of three sampling locations and use this information to determine the contribution of local vs. regional sources; (3) collect, re–suspend, and chemically characterize various crustal sources within the area to identify differences which may isolate them (crustal sources) as independent sources, and; (4) use a receptor based modeling approach to identify particle sources and the relative impact of each on ambient PM concentrations. This work reviews the study objectives, design, site descriptions, and measurement techniques relevant to this research effort and presents the general characteristics of PM during the study period. This unique dataset will support efforts to reduce PM10 and PM2.5 concentrations in the area to below the National Ambient Air Quality Standards (NAAQS) for these pollutants.Coarse particle concentrations are, on average, approximately 5 times fine particle mass concentrations within the region. Coarse particle concentrations in Pinal County are highest during spring and fall seasons, consistent with the tilling and harvesting seasons while fine particles concentrations are highest during fall. Crustal material is the dominant component of coarse particle composition, representing 50% of the mass on average followed closely by organic matter representing 15%. Fine particles still contain a significant crustal fraction (30%) but organic matter dominates at 37% of the particle mass.
اظهر المزيد [+] اقل [-]Relationship between sources and patterns of VOCs in indoor air
2014
Rösch, Carolin | Kohajda, Tibor | Röder, Stefan | Bergen, Martin von | Schlink, Uwe
People spend most of their daytime in indoor environments. Their activities influence the composition of the indoor air by emitting volatile organic compounds (VOCs). The increasing number of different VOCs became the focus of attention in recent years as the question arises from the relationship between exposure to air pollutants and diseases. The present study of flats in Leipzig (Germany) is based on measurements of 60 different VOCs and is unique in the field of indoor air quality due to its enormous size of samples (n=2 242) and questionnaire data. The main purpose of our analysis was to identify the sources and patterns that characterize airborne VOCs in occupied flats. We combined two methods, principal components analysis (PCA) and non–negative matrix factorization (NMF), to assign compounds to their origin and to understand the coinstantaneous existence of several VOCs. PCA clustering provided a source apportionment and yielded 10 principal components (PCs) with an explained variance of 72%. However, real indoor air quality is often affected by combined sources. NMF reveals characteristic compositions of VOCs in indoor environments and emphasizes that constantly recurring structures are not single sources, but rather fusions of them, so called patterns. Interpreting these sources, we realized that homes were strongly influenced by ventilation, human activities, furnishings, natural processes (such as solar radiation) or their combinations. The very large set of samples and the combination with questionnaires applied on this comprehensive assessment of VOCs allows generalizing the results to homes in middle–scale cities with minor industrial pollution. As a conclusion, single VOC–dose–response relationships are inopportune for situations when indoor sources occur in combination. Further studies are necessary to assess associated health risks.
اظهر المزيد [+] اقل [-]Impact of pond aquaculture effluents on seagrass performance in NE Hainan, tropical China
2014
Herbeck, Lucia S. | Sollich, Miriam | Unger, Daniela | Holmer, Marianne | Jennerjahn, Tim C.
The impact of pond aquaculture effluents on the distribution and performance of seagrasses was examined in NE Hainan, tropical China. Samples were taken along transects in three back-reef areas with different extent of aquaculture production in their hinterland. High δ15N in seagrass leaves and epiphytes (6–9‰) similar to values in pond effluents documented aquaculture as dominant nitrogen source in the back-reefs with decreasing impact with distance from shore. Seagrass species abundance, shoot density and biomass were lower and concentrations of nutrients, chlorophyll and suspended matter were higher at nearshore sites with high and moderate pond abundance than at the control site. High epiphyte loads and low δ34S in seagrass leaves suggest temporal shading and sulphide poisoning of the nearshore seagrasses. Observed gradients in environmental parameters and seagrass performance indicate that the distance from the pond outlets and size of the adjacent pond agglomeration are major determinants of seagrass degradation.
اظهر المزيد [+] اقل [-]Metals and metalloids in whole blood and tissues of Olive Ridley turtles (Lepidochelys olivacea) from La Escobilla Beach (Oaxaca, Mexico)
2014
Cortés-Gómez, Adriana A. | Fuentes-Mascorro, Gisela | Romero, Diego
Concentrations of eight metals and metalloids (Pb, Cd, Cu, Zn, Mn, Se, Ni and As) were evaluated from 41 nesting females (blood) and 13 dead (tissues) Olive Ridley turtles (Lepidochelys olivacea), a species classified as vulnerable and also listed in Appendix I of the Convention of International Trade in Endangered Species (CITES). The mean blood, liver and kidney lead concentration were 0.02±0.01, 0.11±0.08 and 0.06±0.03μgg−1 ww respectively, values lower than other turtle species and locations, which it could be due to the gradual disuse of leaded gasoline in Mexico and Central America since the 1990s. Mean concentration of cadmium was 0.17±0.08 (blood), 82.88±36.65 (liver) and 150.88±110.99μgg−1 (kidney). To our knowledge, the mean renal cadmium levels found is the highest ever reported worldwide for any sea turtle species, while other six elements showed a concentration similar to other studies in sea turtles.
اظهر المزيد [+] اقل [-]Evaluation of concentrations and source contribution of PM10 and SO2 emitted from industrial complexes in Ulsan, Korea: Interfacing of the WRF–CALPUFF modeling tools
2014
Lee, Hyung–Don | Yoo, Jung–Woo | Kang, Min–Kyoung | Kang, Ji–Soon | Jung, Jong–Hyun | Oh, Kwang–Joong
The Ulsan metropolitan city in Korea includes two national industrial complexes [Ulsan Petrochemical Industrial Complex (UPIC) and On–San Industrial Complex (OSIC)] that produce various industrial products. Air pollution from these industrial complexes may pose potential health risks to nearby residential areas. Therefore, WRF–CALPUFF (Weather Research and Forecasting–California PUFF) modeling systems were used to simulate concentration distributions of typical air pollutants (PM10 and SO2), and statistics are computed to determine the models' ability to simulate observations. Finally, we classified the type of business and districts in the region and evaluated their contribution to air pollutant concentrations. Five statistical metrics [Index of Agreement (IOA), Fractional Bias (FB), Normalized Mean Square Error (NMSE), and Pearson correlation coefficient (R)] indicated that the simulated values using CALMET was determined to have sufficient reliability to predict CALPUFF, and simulated concentration field using CALPUFF showed a good agreement [typical values: IOA (0.284 to 0.850 for PM10, 0.412 to 0.895 for SO2), and FB (0.043 to 0.821 for PM10, –0.393 to 0.638 for SO2)] with the observed concentrations. The maximum concentrations of PM10 and SO2 using CALPUFF were predicted to be located around OSIC and UPIC, respectively. We compared the simulated values with observed values at 14 monitoring stations, and the SO2 tended to display better agreement to observed SO2 values than modeled and observed PM10. The source contribution analysis found that PM10 and SO2 were mostly influenced by group B (35.1%) including steel, machinery, and electronic industry nearby OSIC and group A (40.6%) including chemical industry nearby UPIC, respectively. Finally, the correlations between simulated concentrations of PM10 and SO2 and corresponding emission quantities were 0.663 and 0.528, respectively. Overall, the results of this study could be useful for designing appropriate seasonal regulations to reduce ambient concentrations of air pollutants and assisting environmental administrators to control the sources that contribute the most to degradation of air quality.
اظهر المزيد [+] اقل [-]Analysis of total column ozone in Peninsular Malaysia retrieved from SCIAMACHY
2014
Tan, Kok Chooi | Lim, Hwee San | Mat Jafri, Mohd Zubir
Due to lack of observational studies on greenhouse gases in Malaysia, most studies in this field were carried out based on ground station data. These studies did not utilize satellite data from the equatorial area. Satellite remote sensing is one of the most effective approaches for greenhouse gas distribution monitoring on a global scale. As such, satellite remote sensing exhibits a very high spatial and temporal resolution. Variations of ozone concentrations in Peninsular Malaysia were observed and investigated by means of data retrieved from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). The aim of this study was to determine the monthly and seasonal ozone concentrations in Peninsular Malaysia from January 2003 to December 2009. We utilized total column ozone at level 2 of the WFMD version 1.0. A spatial resolution value of 1°×1.25° was used. Analysis indicated that the five selected sites exhibited strong seasonal atmospheric ozone concentration variations. These variations resulted from the significant differences between the northeast monsoon (NEM) and the southwest monsoon (SWM). As the NEM prevails, cold air breaks out from Siberia and spreads to the equatorial region in the form of northeasterly cold surge winds. These winds manifest in low–level anticyclones over Southeast Asia. Inversely, the air masses from the southwest contribute to long–range air pollution. During SWM, the transport of atmospheric ozone by wind is associated with biomass burning in Sumatra, Indonesia. HYSPLIT was also utilized to identify the air pollutant transport between NEM and SWM toward Peninsular Malaysia. Comparisons were made between the ozone data from five sites in 2009. Data were retrieved from SCIAMACHY and the Atmospheric Infrared Sounder (AIRS). The relative difference average of the ozone data measured by SCIAMACHY and AIRS was approximately 6%.
اظهر المزيد [+] اقل [-]Chemical characteristics of rainwater at a southeastern site of Brazil
2014
Facchini Cerqueira, Marcos Rodrigues | Pinto, Marcelo Fonseca | Derossi, Ingrid Nunes | Esteves, Wesley Tinoco | Rachid Santos, Mellina Damasceno | Costa Matos, Maria Auxiliadora | Lowinsohn, Denise | Matos, Renato Camargo
A total of 50 rainwater samples were analyzed in order to investigate trace elements in wet precipitation of Juiz de Fora City, during February, 2010 and February, 2011. Samples were analyzed for major cations (H3O+, Na+, NH4+, K+, Mg2+ and Ca2+) and anions (NO3−, SO42−, Cl− and HCO3−), hydrogen peroxide (H2O2), some trace metals (Cu2+, Zn2+, Cd2+ and Pb2+), as well as some other physicochemical aspects like pH, conductivity and redox potential. Rainwater pH mean was of 5.77 (±0.52). Cations and anions mean values ranged from 7.12μEq L−1 (K+) to 39.6μEq L−1 (Ca2+). Principal Component Analysis (PCA) with Varimax normalized rotation was performed, grouping the major analyzed cations and anions into different factors. Mg2+, K+, Ca2+ and HCO3− were assigned to soil contribution, Na+ and Cl− to sea–salt contribution and NO3−, SO42− and NH4+ to anthropogenic sources. Hydrogen peroxide average concentration was of 19.2±17.5μmol L−1 with higher values in summer and lower in spring and autumn, reverse case was observed for H3O+ levels. Zn2+ (7.31±2.74)μg L−1 and Cu2+ (4.07±0.74)μg L−1 were within the range of other studied areas, while Cd2+ and Pb2+ were below the detection limit.
اظهر المزيد [+] اقل [-]Assessing PAHs pollution in Qingdao coastal area (China) by the combination of chemical and biochemical responses in scallops, Chlamys farreri
2014
Jin, Qian | Pan, Luqing | Liu, Dong | Hu, Fengxiao | Xiu, Meng
The PAHs concentrations in seawater and tissues from the scallop Chlamys farreri were detected in three sites in Qingdao, China in 2011. The PAHs concentrations in seawater ranged from 25.32ng/L to 314.62ng/L. There were significant differences (p<0.05) between the residual levels among scallop tissues. The highest concentrations of PAHs in seawater and tissues were found in S2. The ethoxyresorufin-O-deethylase (EROD) activity of the digestive gland and the malondialdehyde (MDA) contents of the digestive gland and gill were sensitive to PAHs (p<0.05). This study integrated the PAHs concentrations in seawater, residual levels, the variation of biochemical response and the correlation coefficient analysis, and concluded that Qingdao is a medium PAH-contaminated area on a global scale. The highest PAHs were accumulated in the digestive gland followed by the gill, soft tissue and adductor muscle. The EROD activity of the digestive gland and the MDA contents of the digestive gland and gill could be applied to assess the PAHs pollution status in Qingdao, China.
اظهر المزيد [+] اقل [-]Trace elements distribution and ecological risk assessment of seawater and sediments from Dingzi Bay, Shandong Peninsula, North China
2014
Pan, Jingjin | Pan, Jin-Fen | Wang, Min
Selected trace elements (Hg, As, Pb, Cu, Cd, Cr and Zn) in seawater and sediments from Dingzi Bay, a semi-enclosed bay suffering from severe degradation located in the Shandong Peninsula, were investigated to evaluate the spatial distribution and potential ecological risk. Results indicated that higher concentrations occurred in the inner bay. Calculation of pollution load index (PLI) showed overall low values while the concentration factor (CF) indicated that Hg, As and Cd were at moderate risk levels in the region. Based on the effects-range classification, As was likely to pose environment risk. Principal component analysis (PCA) revealed that in addition to background contributions, the trace elements contamination could also be affected by anthropogenic pollution sources. The results of present study provide useful background information for further marine investigation and management in the region.
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