خيارات البحث
النتائج 271 - 280 من 3,243
Relationship between trace metal concentrations in the terrestrial moss Pseudoscleropodium purum and in bulk deposition
2015
Boquete, M.T. | Fernández, J.A. | Carballeira, A. | Aboal, J.R.
The relationship between trace metal concentrations in Pseudoscleropodium purum (Hedw.) M. Fleish. and bulk deposition (BD) was examined at 21 sites (SS) to ascertain whether the lack of correlations reported in previous studies are due to limitations in the experimental design. Thus, we implemented some improvements to it and examined the correlations in depth. We could conclude that this relationship is determined by other variables rather than by the pollutant inputs themselves (BD). Thus, whether or not moss concentrations and bulk deposition are significantly correlated will depend on the combination of the above referred factors in a given area at a given time. Therefore, P. purum in particular, and most likely native terrestrial mosses in general, are less than ideal biomonitors for yielding absolute values of atmospheric trace metal deposition. We recommend their use as qualitative indicators and the use of classical methods to obtain absolute values.
اظهر المزيد [+] اقل [-]Evaluating the efficacy of playground washing to reduce environmental metal exposures
2015
Taylor, Mark Patrick | Zahran, Sammy | Kristensen, Louise | Rouillon, Marek
Washing and wet mopping is often advocated as a remedial treatment to limit exposure to lead dust. Here, surface and pre- and post-play wipes were measured to ascertain dust metal exposures (arsenic, cadmium, copper, lead and zinc) following play routines at four playgrounds in the smelter city of Port Pirie, South Australia, which are washed regularly. Although post-play hand wipe metals were 55.9% (95% CI: −0.78, −0.34) lower on wash days, loadings increased ∼5.1% (95% CI: 1.2, 11.7) per hour after washing. Despite washing, post-play hand lead exceeded a conservative value of 800 μg/m2 within 24 h or sooner, with loadings increasing in proximity to the smelter. Post-play lead loadings were always >1000 μg/m2 at the playground closest to smelter. Playground washing results in short-lived exposure reduction and effective treatment requires elimination of smelter emissions.
اظهر المزيد [+] اقل [-]Present knowledge and perspectives on the role of copper in brake materials and related environmental issues: A critical assessment
2015
Straffelini, Giovanni | Ciudin, Rodica | Ciotti, Alessandro | Gialanella, Stefano
This critical review presents several aspects related to the use of copper as a main component in brake pads in road vehicles. The compositions of these materials are attracting increasing interest and concern due to the relative contribution of wear products to particulate matter emissions in the environment as a result of braking action even though there has been a reduction in exhaust products from internal combustion engines. We review the data on the main wear mechanisms in brake systems and highlight the positive role of copper. However, similar to other heavy metal emissions, even the release of copper into the atmosphere may have important environmental and health effects. Thus, several replacement strategies are being pursued, and the positive and negative features will be critically reviewed. Additionally, the future perspectives in materials development will be discussed.
اظهر المزيد [+] اقل [-]Concentration and distribution of contaminants in lake trout and walleye from the Laurentian Great Lakes (2008–2012)
2015
McGoldrick, Daryl J. | Murphy, Elizabeth W.
Biomonitoring programs for persistent, bioaccumulative, and/or toxic chemicals of concern in fish tissues have been operated by the governments of Canada and the United States in the Great Lakes since the 1970's. The objectives of these programs are to assess concentrations of harmful chemicals in whole body top predator fish as an indicator of ecosystem health and to infer potential harm to fish and fish consuming wildlife in the Great Lakes Basin. Chemicals of interest are selected based upon national and binational commitments, risk assessment, and regulation, and include a wide range of compounds. This review summarizes all available data generated by Environment Canada and the United States Environmental Protection Agency for chemicals measured in whole body homogenates of Lake Trout (Salvelinus namaycush) and Walleye (Sander vitreus) for the time period spanning 2008 to 2012 from each of the five Great Lakes. The summary shows that concentrations of legacy compounds, such as, POPs listed in the Stockholm Convention and mercury continue to dominate the chemical burden of Great Lakes fish. This assessment, and others like it, can guide the creation of environmental quality targets where they are lacking, optimize chemical lists for monitoring, and prioritize chemicals of concern under agreements such as the Great Lakes Water Quality Agreement and the Stockholm Convention.
اظهر المزيد [+] اقل [-]The characteristic of Pb isotopic compositions in different chemical fractions in sediments from Three Gorges Reservoir, China
2015
Han, Lanfang | Gao, Bo | Wei, Xin | Gao, Li | Xu, Dongyu | Sun, Ke
To explore the distribution and sources of Pb within the Three Gorges Reservoir (TGR), Pb concentrations and isotope ratios were measured in sediment cores collected from one mainstream and three tributaries. The results showed that sediments contained an average of 43.54 mg kg−1 of Pb, roughly 1.6 times higher than the geochemical background concentration. Mainstream sediments showed higher average Pb concentrations but slightly less 206Pb/207Pb and more radiogenic 207Pb/208Pb ratios than all tributaries. Most Pb occurred in reducible phases, with much less in exchangeable and oxidizable fractions; thus, Fe–Mn oxides may be the major sink of anthropogenic Pb. Bi-plots of 206Pb/207Pb versus Pb content, and of 206Pb/207Pb versus 207Pb/208Pb, indicated that coal combustion was the predominant anthropogenic Pb source for exchangeable, reducible, and oxidizable fractions, while residual Pb mainly occurred naturally. The average percentage of coal consumption contribution was 61.1% for the Pb contamination in sediments in the lower reaches in the TGR region.
اظهر المزيد [+] اقل [-]Organochlorine pesticides and polychlorinated biphenyls in air, grass and yak butter from Namco in the central Tibetan Plateau
2015
Wang, Chuanfei | Wang, Xiaoping | Yuan, Xiaohua | Ren, Jiao | Gong, Ping
Limited studies on bioaccumulation of persistent organic pollutants (POPs) along terrestrial food chains were conducted. The food chain air–grass–yak (butter) in the pasture region of Namco in the central Tibetan Plateau (TP) was chosen for study. The air, grass and butter POPs in the TP were at the lower end of the concentrations generally found around the globe. HCB was the main pollutant in air and butter. Besides HCB, β-HCH and p,p′-DDE were the other major compounds in butter. Along the food chain, DDTs and high molecular weight PCB-138, 153 and 180 had higher Biological Concentration Factor values. The air–butter transfer factors of POPs were derived and demonstrated the practical advantage in predicting the atmospheric OCPs and PCBs to the TP. This study sheds light on the transfer and accumulation of POPs along the terrestrial food chain of the TP.
اظهر المزيد [+] اقل [-]Dual partitioning and attachment effects of rhamnolipid on pyrene biodegradation under bioavailability restrictions
2015
Congiu, Eleonora | Parsons, John R. | Ortega-Calvo, Jose Julio
We investigated the effects of different bioavailability scenarios on the rhamnolipid-enhanced biodegradation of pyrene by the representative polycyclic aromatic hydrocarbon degrader Mycobacterium gilvum VM552. This biosurfactant enhanced biodegradation when pyrene was provided in the form of solid crystals; no effect was observed when the same amount of the chemical was preloaded on polydimethylsiloxane (PDMS). An enhanced effect was observed when pyrene was sorbed into soil but not with the dissolved compound. Synchronous fluorescence spectrophotometry and liquid scintillation were used to determine the phase exchange of pyrene. We also investigated the phase distribution of bacteria. Our results suggest that the rhamnolipid can enhance the biodegradation of pyrene by micellar solubilization and increase diffusive uptake. These mechanisms increase substrate acquisition by bacterial cells at exposure concentrations well above the half-saturation constant for active uptake. The moderate solubilization of pyrene from PDMS by the rhamnolipid and the prevention of cell attachment may explain the lack of enhancement for pyrene-preloaded PDMS.
اظهر المزيد [+] اقل [-]Tracing mercury pathways in Augusta Bay (southern Italy) by total concentration and isotope determination
2015
Bonsignore, M. | Tamburrino, S. | Oliveri, E. | Marchetti, A. | Durante, C. | Berni, A. | Quinci, E. | Sprovieri, M.
The mercury (Hg) pollution of sediments is the main carrier of Hg for the biota and, subsequently, for the local fish consumers in Augusta Bay area (SE Sicily, Italy), a coastal marine system affected by relevant sewage from an important chlor-alkali factory. This relationship was revealed by the determination of Mass Dependent (MDF) and Mass Independent Fractionation (MIF) of Hg isotopes in sediment, fish and human hair samples. Sediments showed MDF but no MIF, while fish showed MIF, possibly due to photochemical reduction in the water column and depending on the feeding habitat of the species. Benthic and demersal fish exhibited MDF similar to that of sediments in which anthropogenic Hg was deposited, while pelagic organisms evidenced higher MDF and MIF due to photoreduction. Human hair showed high values of δ202Hg (offset of +2.2‰ with respect to the consumed fish) and Δ199Hg, both associated to fish consumption.
اظهر المزيد [+] اقل [-]An exploratory analysis of the relationship between ambient ozone and particulate matter concentrations during early pregnancy and selected birth defects in Texas
2015
Vinikoor-Imler, Lisa C. | Stewart, Thomas G. | Luben, Thomas J. | Davis, J Allen | Langlois, Peter H.
We performed an exploratory analysis of ozone (O3) and fine particulate matter (PM2.5) concentrations during early pregnancy and multiple types of birth defects. Data on births were obtained from the Texas Birth Defects Registry (TBDR) and the National Birth Defects Prevention Study (NBDPS) in Texas. Air pollution concentrations were previously determined by combining modeled air pollution concentrations with air monitoring data. The analysis generated hypotheses for future, confirmatory studies; although many of the observed associations were null. The hypotheses are provided by an observed association between O3 and craniosynostosis and inverse associations between PM2.5 and septal and obstructive heart defects in the TBDR. Associations with PM2.5 for septal heart defects and ventricular outflow tract obstructions were null using the NBDPS. Both the TBDR and the NBPDS had inverse associations between O3 and septal heart defects. Further research to confirm the observed associations is warranted.
اظهر المزيد [+] اقل [-]Coupling spectroscopic and chromatographic techniques for evaluation of the depositional history of hydrocarbons in a subtropical estuary
2015
Martins, César C. | Doumer, Marta E. | Gallice, Wellington C. | Dauner, Ana Lúcia L. | Cabral, Ana Caroline | Cardoso, Fernanda D. | Dolci, Natiely N. | Camargo, Luana M. | Ferreira, Paulo A.L. | Figueira, Rubens C.L. | Mangrich, Antonio S.
Spectroscopic and chromatographic techniques can be used together to evaluate hydrocarbon inputs to coastal environments such as the Paranaguá estuarine system (PES), located in the SW Atlantic, Brazil. Historical inputs of aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analyzed using two sediment cores from the PES. The AHs were related to the presence of biogenic organic matter and degraded oil residues. The PAHs were associated with mixed sources. The highest hydrocarbon concentrations were related to oil spills, while relatively low levels could be attributed to the decrease in oil usage during the global oil crisis. The results of electron paramagnetic resonance were in agreement with the absolute AHs and PAHs concentrations measured by chromatographic techniques, while near-infrared spectroscopy results were consistent with unresolved complex mixture (UCM)/total n-alkanes ratios. These findings suggest that the use of a combination of techniques can increase the accuracy of assessment of contamination in sediments.
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