Affiner votre recherche
Résultats 811-820 de 1,956
Impacts of long-line aquaculture of Pacific oysters (Crassostrea gigas) on sulfate reduction and diffusive nutrient flux in the coastal sediments of Jinhae–Tongyeong, Korea Texte intégral
2013
Hyun, Jung-Ho | Kim, Sŭng-han | Mok, Jin-Sook | Lee, Jae-seong | An, Sung-Uk | Lee, Won-Chan | Jung, Rae-Hong
We investigated the environmental impacts of long-line aquaculture of Pacific oysters (Crassostrea gigas) on sediment geochemistry and carbon oxidation by sulfate reduction and diffusive benthic nutrient flux in a coastal ecosystem in Korea. Inventories of the NH4+ and HPO42- at the farm site were 7.7–11.5 and 1.8–8.0 times higher, respectively, than those at a reference site. Sulfate reduction rates (SRRs) at the oyster farm were 2.4–5.2 times higher than SRRs at the reference site. The SRRs at the farm site were responsible for 48–99% (average 70%) of the total C oxidation in the sediment. The diffusive benthic fluxes of NH4+ and HPO42- at the oyster farm were comparable to 30–164% and 19–58%, respectively, of the N and P demands for primary production, and were responsible for the enhanced benthic microalgal biomass on the surface sediment.
Afficher plus [+] Moins [-]Effects of anthropogenic metallic contamination on cholinesterases of Gambusia holbrooki Texte intégral
2013
Brandão, Fátima | Correia, Alberto Teodorico | Gonçalves, Fernando | Nunes, Bruno
Effects of anthropogenic metallic contamination on cholinesterases of Gambusia holbrooki Texte intégral
2013
Brandão, Fátima | Correia, Alberto Teodorico | Gonçalves, Fernando | Nunes, Bruno
Metal contamination causes multiple biological dysfunctions, including impairment of key physiological functions by targeting enzymes. This feature is a matter of concern, since it may imply significant disturbances in energy allocation, behaviour, reproduction, and survival. Inhibition of the cholinesterase (ChE) activity of aquatic organisms by metals has been described, and systematically used in biomonitoring studies as effect criterion of environmental exposure to these compounds. The present paper addresses the feasibility of using ChE inhibition to quantify the adverse acute and chronic effects of metals (copper, zinc, lead, and cadmium) on nervous tissue of Gambusia holbrooki. With the exception of acute exposure to copper, ChE activity was not significantly impaired. The meanings of the reported findings are further discussed, aiming at a more comprehensive use of this biomarker in environmental assessment. Based on the obtained results, the role of ChE inhibition in environmental metal contamination scenarios should be questioned or even discarded.
Afficher plus [+] Moins [-]Effects of anthropogenic metallic contamination on cholinesterases of Gambusia holbrooki Texte intégral
2013
Brandão, Fátima | Correia, Alberto Teodorico | Gonçalves, Fernando | Nunes, Bruno
Metal contamination causes multiple biological dysfunctions, including impairment of key physiological functions by targeting enzymes. This feature is a matter of concern, since it may imply significant disturbances in energy allocation, behaviour, reproduction, and survival. Inhibition of the cholinesterase (ChE) activity of aquatic organisms by metals has been described, and systematically used in biomonitoring studies as effect criterion of environmental exposure to these compounds. The present paper addresses the feasibility of using ChE inhibition to quantify the adverse acute and chronic effects of metals (copper, zinc, lead, and cadmium) on nervous tissue of Gambusia holbrooki. With the exception of acute exposure to copper, ChE activity was not significantly impaired. The meanings of the reported findings are further discussed, aiming at a more comprehensive use of this biomarker in environmental assessment. Based on the obtained results, the role of ChE inhibition in environmental metal contamination scenarios should be questioned or even discarded. | The present work was funded by Fundação para a Ciência e a Tecnologia: project “BiOtoMetal” (PTDC/AMB/70431/2006). We would like to acknowledge the contribution of Jonathan Wilson, for his decisive contribution to the final format of this article. | published
Afficher plus [+] Moins [-]Concentration and composition of polycyclic aromatic hydrocarbons (PAHs) in plastic pellets: Implications for small-scale diagnostic and environmental monitoring Texte intégral
2013
Fisner, Mara | Taniguchi, Satie | Majer, Alessandra P. | Bícego, Márcia C. | Turra, Alexander
Plastic pellets may serve as a carrier of toxic contaminants, including polycyclic aromatic hydrocarbons (PAHs). Considering that beach morphodynamics and pellet distribution varied along the shore, and that contaminant sources may vary on different scales, it is expected that this variability is reflected in the concentration and composition of contaminants. This hypothesis was tested through a sampling of plastic pellets at 30 sites along the shore in Santos Bay (Brazil). The total PAH concentrations and the priority PAHs showed high variability, with no clear pattern. Their composition differed among the sampling sites; some of the compounds represent a potential risk to organisms. The sources of contamination, as indicated by the isomer ratios, were also variable among sites. The high small-scale spatial variability found here has implications for estimating the plastic pellet contamination on beaches, since a sample from a single site is unlikely to be representative of an entire beach.
Afficher plus [+] Moins [-]A modelling approach for estimating background pollutant concentrations in urban areas Texte intégral
2013
Torras Ortíz, Sandra | Friedrich, Rainer
Air pollution control strategies have helped to improve the air quality over Europe over the last twenty years. Despite this success, the improvements have been insufficient to protect health of those who spend most of their time within urban areas and particularly near major roads. Given the inherent complexity of urban environments and the incomplete understanding of the physical and chemical processes involved in pollutant dispersion, it is a challenging task to estimate urban air quality. In order to address this issue, a new regression model for estimating the urban increment for all cities of a region up to Europe as a whole is developed. The model is able to capture the higher pollutant concentrations commonly found within urban areas for assessing the localized effects associated to urban emissions. This approach is used for estimating annual concentrations of PM10 and NO2 for all urban areas with more than 50 000 inhabitants in Germany for the reference year 2005. The results showed that there are differences on air quality levels across urban areas in Germany. This information is relevant when evaluating the impact of emission reduction policies on air quality, which should take into account the cost–benefit of each measure. Furthermore, as the modelling approach allows for flexibility changing initial conditions and building scenarios, the added values of this approach are the large spatial domain covered, the high spatial resolution, and its inherent flexibility to address other environmental issues, such as analysis of emission reduction scenarios, the human exposure to certain pollutants and their associated human health impacts.
Afficher plus [+] Moins [-]Chemical characterization and source apportionment of PM10 and PM2.5 in the metropolitan area of Costa Rica, Central America Texte intégral
2013
Murillo, Jorge Herrera | Roman, Susana Rodriguez | Rojas Marin, Jose Felix | Ramos, Arturo Campos | Jimenez, Salvador Blanco | Cárdenas González, Beatriz | Baumgardner, Darrel Gibson
PM10 and PM2.5 levels, concentrations of major ionic components, trace elements, and organic and elemental carbon were evaluated from samples collected in 4 sites (industrial, commercial and residential zones) located in the metropolitan area of Costa Rica. The annual mean PM levels were higher in high traffic–commercial (HE–01) and industrial (BE–02) sites, 55 μg m–3 and 52 μg m–3 for PM10 and 37 μg m–3 and 36 μg m–3 for PM2 5, respectively. The major components of PM25 were organic matter (OM) and elemental carbon (EC) (44.5–69.9%), and secondary ions (16.1–27.2%), whereas the major components of PM10 were OM+EC (32.7–59.4%), crustal material (23.5–35.6%) and secondary ions (11.4–26.9%). For the most of the sampling sites, PM10 and PM2.5 concentrations were lower during the dry season and increased gradually in the rainy season due to wind patterns. PMF model identified 8 principle sources for PM10 and PM2.5 in the industrial site (crustal, secondary sulfate, secondary nitrate, secondary organic, traffic, sea–salt aerosols, industrial and oil combustion), 6 and 5 sources in commercial and residential sites, respectively. The source contributions showed a clear seasonal pattern for all the sites.
Afficher plus [+] Moins [-]Estimating the near-surface daily fine aerosol load using hourly Radon-222 observations Texte intégral
2013
Crawford, Jagoda | Zahorowski, Wlodek | Cohen, David D. | Chambers, Scott | Stelcer, Eduard | Werczynski, Sylvester
We investigate the extent to which hourly radon observations can be used to estimate daily PM2.5 loading near the ground. We formulate, test and apply a model that expresses the mean daily PM2.5 load as a linear combination of observed radon concentrations and differences on a given day. The model was developed using two consecutive years of observations (2007–2008) at four sites near Sydney, Australia, instrumented with aerosol samplers and radon detectors. Model performance was subsequently evaluated against observations in 2009. After successfully reproducing mean daily radon concentrations (r2≥0.98), we used the model to estimate daily PM2.5 mass, as well as that of selected elements (Si, K, Fe, Zn, H, S and Black Carbon). When parameterizing the model for elemental mass estimates the highest r2 values were generally obtained for H, BC, K and Si. Separating results by season, the r2 values for K and BC were higher in winter for all sites, a period of time where higher concentrations of these elements are seen and a rapid estimation tool would be of particular benefit. The best overall results were obtained in winter for H and BC [r2 = 0.50, 0.68, 0.70, 0.63 (H) and 0.57, 0.57, 0.78, 0.44 (BC)], respectively for Warrawong, Lucas Heights, Richmond and Muswellbrook. Evaluation of model PM2.5 estimates was most successful for days with typical aerosol loads; loads were usually underestimated for, the less frequent, high–to–extreme pollution days. The best elemental results were obtained for BC at Richmond in winter (r2 = 0.68). However, for Warrawong and Lucas Heights r2 values increased from 0.26 to 0.60, and from 0.33 to 0.73, respectively, when several particularly high concentration events were excluded from the analysis. The model performed best at Richmond, an inland site with relatively flat terrain. However, model parameters need to be evaluated for each site.
Afficher plus [+] Moins [-]Microscopic observation of symbiotic and aposymbiotic juvenile corals in nutrient-enriched seawater Texte intégral
2013
Tanaka, Yasuaki | Iguchi, Akira | Inoue, Mayuri | Mori, Chiharu | Sakai, Keinan | Suzuki, Atsushi | Kawahata, Hodaka | Nakamura, Takashi
Symbiotic and aposymbiotic juvenile corals, which were grown in the laboratory from the gametes of the scleractinian coral Acropora digitifera and had settled down onto plastic culture plates, were observed with a microscope under different nutrient conditions. The symbiotic corals successfully removed the surrounding benthic microalgae (BMA), whereas the aposymbiotic corals were in close physical contact with BMA. The areal growth rate of the symbiotic corals was significantly higher than that of the aposymbiotic corals. The addition of nutrients to the culture seawater increased the chlorophyll a content in the symbiotic coral polyps and enhanced the growth of some of the symbiotic corals, however the average growth rate was not significantly affected, most likely because of the competition with BMA. The comparison between the symbiotic and aposymbiotic juvenile corals showed that the establishment of a symbiotic association could be imperative for post-settlement juvenile corals to survive in high-nutrient seawater.
Afficher plus [+] Moins [-]Water concentrations of PAH, PCB and OCP by using semipermeable membrane devices and sediments Texte intégral
2013
Karacık, B. | Okay, O.S. | Henkelmann, B. | Pfister, G. | Schramm, K.-W.
Water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were estimated from semipermeable membrane devices (SPMDs) and from sediment pollutant concentrations. SPMDs were deployed in the Istanbul Strait and Marmara Sea and retrieved after 7 and 21days. Performance reference compounds (PRCs) were used to determine the site-specific sampling rates of the compounds. Water concentrations (Cw) of the analyzed compounds estimated by using two different calculation methods for SPMDs were found similar. Cw of total PAHs estimated from SPMDs (Cw-spmd) were found between 13 and 79ngL−1 and between 7.0 and 68ngL−1 for 7 and 21days of deployments respectively. Water concentrations of PCBs using sediment data was found as between 0.001 and 11.0ngL−1. The highest value of Cw-spmd for two deployments were 2.8ngL−1 for OCPs. Cw estimated from sediment concentrations were generally higher than those estimated from SPMDs.
Afficher plus [+] Moins [-]Indicators of microbial beach water quality: Preliminary findings from Teluk Kemang beach, Port Dickson (Malaysia) Texte intégral
2013
Praveena, Sarva Mangala | Chen, Kwan Soo | Ismail, Sharifah Norkhadijah Syed
This study aims to determine the concentrations of total coliforms and Escherichia coli (E. coli) in beach water, Teluk Kemang beach. This study was also aimed to determine relationship between total coliforms, E. coli and physicochemical parameters. As perceived health symptoms among beach visitors are rarely incorporated in beach water studies, this element was also assessed in this study. A total of eight water sampling points were selected randomly along Teluk Kemang beach. Total coliforms concentrations were found between 20 and 1940cfu/100ml. E. coli concentrations were between 0 and 90cfu/100ml. Significant correlations were found between total coliforms and E. coli with pH, temperature and oxidation reduction potential. Skin and eyes symptoms were the highest reported though in small numbers. Microbiological water quality in Teluk Kemang public beach was generally safe for recreational activities except sampling location near with sewage outfall.
Afficher plus [+] Moins [-]Baseline of the butyltin distribution in surface sediments (0–20cm) of the Elbe estuary (Germany, 2011) Texte intégral
2013
Wetzel, Markus A. | Winterscheid, Axel | Wahrendorf, Dierk-Steffen
The concentrations of the butyltin (BT) species tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were measured in the surface sediments (0–20cm) at 29 sites of the Elbe estuary in 2011. TBT values ranged from ‘undetectable’ to 41ngSng−1 dry weight (d.w.) with the two highest values measured in the inner section of the estuary near the port of Hamburg (32 and 41ngSng−1 d.w.). TBT, DBT, and MBT showed significant decreases towards the estuarine mouth (Spearman’s rho −0.660, −0.685, and −0.583, respectively, p<0.001). The degradation of TBT, assessed by the BT degradation index (BDI), showed a rising trend from the port of Hamburg towards the mouth of the estuary, though not a significant one (Spearman’s correlation, p=0.066). Annual sedimentation rates did not show any significant correlations (Spearman’s correlation) to BT pollution or to the butyltin degradation index (BDI).
Afficher plus [+] Moins [-]