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991.
David A Dagnino S Pichot Y Munaron D Escande A Casellas C Fenet H Gomez E 《Marine environmental research》2008,66(1):105-107
In vitro bioassays would facilitate monitoring of estrogen-like compounds in mussels (Mytilus galloprovincialis) since they tend to accumulate lipophilic compounds in their fat and muscle tissue. However, estradiol (E2) steroid (already identified in mussels) could induce false positive responses. This study focuses on temporal variability in estrogenic responses of mussel extracts and the possible relation of this response with E2 levels. The reproductive cycle and growth were thus monitored for six months in sexed mussels. E2 levels were similar between genders and these levels varied with reproductive stages. human estrogen receptor (hER) activities were similar at all stages except in February. E2 present in male and female extracts accounted for part of the hER activation observed, but no correlation was found between E2 levels and hER activities. 相似文献
992.
Concentrations of Cd, Cu, Cr, Co, Ni, Zn, Fe, Mn, Pb, As, and Sb were determined in sediment trap and bottom sediment samples collected seasonally from a station on the eastern Turkish coast of the Black Sea. Cd, Pb and Mn concentrations were highest in the sediment trap samples except during the summer period, whereas Co, Ni, Zn and Fe levels were much lower than corresponding levels found in the surface sediments. Cu, Cr, As and Sb levels showed no definite trend with sediment type. In general, with the exception of Cr, relatively lower metal concentrations in the sediment trap material were determined in the summer period. The highest mass flux, 56.5 g m−2 day−1, was measured during autumn. The highest flux of heavy metals also occurred during autumn and was strongly dependent on particle mass flux. Based on these results, we suggest that the downward vertical transport of particulate heavy metals in this region is related to the high degree of land erosion and the resultant particulate flux dynamics, which occur here. It was noteworthy that the highest concentrations of Cd, Cu, Co, Zn, Fe and Sb in particles were measured during winter a finding which suggests that enhanced fossil fuel combustion, which occurs during this period in adjacent urban and industrial areas plays an important role in the metal composition of sinking particles in nearshore waters. 相似文献
993.
Emissions of Polycyclic aromatic hydrocarbons by savanna fires 总被引:2,自引:0,他引:2
Pierre Masclet Hélène Cachier Catherine Liousse Henri Wortham 《Journal of Atmospheric Chemistry》1995,22(1-2):41-54
Although Polycyclic aromatic hydrocarbons (PAH) are known as anthropogenic compounds arising from the combustion or the pyrolysis of fossil fuels, they may be also emitted by the combustion of vegetation. A field study was carried out in January 1991 at Lamto (Ivory Coast) as part of the FOS DECAFE experiment (Fire Of Savanna). Some ground samplings were devoted to the qualitative and quantitative characterization of atmospheric emissions by savanna fires during prescribed burns and under background conditions. Specific collections for gaseous and particulate PAHs have shown that the African practice of burning the savanna biomass during the winter months is an important source of PAHs. These compounds are emitted mainly in gaseous form but a significant fraction, essentially heavy PAHs, is associated with fine carbonaceous particles and can therefore represent a hazard for human health, since some of these compounds are mutagenic and carcinogenic. Twelve compounds were identified during the fire episodes and in the atmospheric background. The total concentration in the fires is of the order of 10 ng m–3 for the gas phase and from 0.1 to 1 ng m–3 in the aerosols. In the atmospheric background the mean concentrations are regular, 0.15 ng m–3 and 2 pg m–3, respectively. These concentrations are comparable with what is observed in European rural zones. The particulate emissions of PAHs by the savanna fires are distinguished by the abundance of some compounds which can be considered as tracers, although they are also slightly emitted by fossil fuel sources. These compounds are essentially pyrene, chrysene and coronene. In the gas phase, although no individual PAH may be considered as specific of the biomass combustion emissions, the relative abundances of the main PAHs are characteristic of the biomass burning. The concentrations of pyrene and fluorene are always predominant; these compounds could be considered as characteristic emission products of smoldering and flaming episodes, respectively. In the background the PAH composition shows that in a tropical region the air consists of a mixture coming from the various sources, but the biomass combustion is by far the most important source.The fluxes of total PAH emitted by savanna biomass burning in Africa were estimated to be of the order of 17 and 600 ton yr–1, respectively, for the particulate PAHs and the gaseous PAHs, respectively. 相似文献
994.
Ismael S. Ismael Ahmed Melegy Tomas Kratochvíl 《Geotechnical and Geological Engineering》2012,30(1):253-262
Hazardous metal cations enter water through the natural geochemical route or from the industrial wastes. Their separation
and removal can be achieved by adsorptive accumulation of the cations on a suitable adsorbent. In the present work, toxic
Pb(II) ions are removed from water by accumulating it on the surface of natural zeolite in three different forms; one untreated
and two treated samples, one sample treated with 2 M HCI solution and other is treated with 3 M NaOH solution. Natural zeolite
is mainly composed of clinoptilolite, and mordenite, with amount of non-zeolite phase (smectite and illite) and C and CT opal.
The adsorption experiments are carried out using a batch process in environments of different pH, initial Pb(II) concentration,
interaction time and amount of zeolites. Treated zeolite samples show high exchange capacity for Pb(II) compared to untreated
sample, however, acid-treated sample shows an exceedingly good exchange capacity. Equilibrium data fitted well with the Langmuir
isotherm model with maximum adsorption capacity of 115, 126, and 132 mg g−1 of untreated natural zeolites, alkali-treated zeolites and acid-treated zeolites respectively. The rates of adsorption were
found to confirm to pseudo-first order kinetic with good correlation and the overall rate of lead ions uptake. 相似文献
995.
Kálmán Török Bianka Németh Friedrich Koller Júlia Dégi Eszter Badenszki Csaba Szabó Aberra Mogessie 《Mineralogy and Petrology》2014,108(1):33-47
Felsic to mafic granulite xenoliths from late Neogene basalt pyroclastics in four localities of the western Pannonian Basin (Beistein, Kapfenstein, Szigliget and Káptalantóti (Sabar-hegy) were studied to find out their metamorphic and fluid history. The characteristic mineral assemblage of the granulites consists of Pl + Opx + Qtz ± Cpx ± Bt ± Grt ± Kfs. Based on abundant magmatic relic microstructural domains occurring in these rocks, the potential precursors might have been predominantly felsic igneous or high to ultrahigh temperature rocks. Ternary feldspar thermometry provides a rough estimate of temperatures of about 920–1070 °C. The first fluid invasion event, which is linked with this early high to ultrahigh temperature stage is characterised by primary pure CO2 inclusions in apatite and zircon. The densest primary CO2 inclusions indicate 0.52–0.64 GPa pressure at the estimated temperature range of crystallization. According to mineral equilibria and geothermobarometry, the high to ultrahigh temperature rock cooled and crystallized to granulite of predominantly felsic composition at about 750–870 °C and 0.50–0.75 GPa in the middle crust, between 20 and 29 km depths. The second fluid invasion event is recorded by primary CO2-rich fluid inclusions hosted in the granulitic mineral assemblage (plagioclase, quartz and orthopyroxene). In addition to CO2, Raman spectroscopy revealed the presence of minor N2, H2S, CO and H2O in these inclusions. Partial melting of biotite-bearing assemblages could be connected to the next fluid invasion shown by secondary CO2-rich fluids recorded along with healed fractures in plagioclase, clinopyroxene and orthopyroxene. This event could have happened at depths similar to the previous ones. The final step in the granulite evolution was the sampling in the middle crust and transportation to the surface in form of xenoliths by mafic melt. This event generated temperature increase and pressure decrease and thus, limited melting of the xenoliths. The youngest fluid inclusion generation, observed mostly in healed fractures of felsic minerals, could be associated with this event. 相似文献
996.
Sensitivity study and validation of a land surface parameterization using the HAPEX-MOBILHY data set 总被引:6,自引:0,他引:6
A simple parameterization of land surface processes, amenable to the structure of a two-layer soil model, including a representation of the vegetation, has been designed for use in meteorological models. Prior to implementation in a mesoscale model, it is necessary to check the components and to verify the good working order of the parameterization as a whole. The aims of this paper then are: (i) evaluation and a sensitivity study of the various components of the model, specifying the needed accuracy for the parameters; (ii) micrometeorological validation of the model against the HAPEX-MOBILHY data set.First, we present the basic scheme. The focus is on the parameterization of surface resistance, and especially on its relationship with soil moisture.A sensitivity study is then performed through a set of one-dimensional simulations which allow a full interaction between the ground and the atmosphere. Above bare ground, it is shown that both soil texture and initial moisture greatly influence the outcome of the simulation. Latent heat flux ranges from that associated with potential evaporation through a switch-like behavior to that of dry soil. Next, the effects of transpiring vegetation canopies on the physical processes involved and the surface energy balance are examined. The sensitivity of the latent heat flux to changes in the soil and canopy parameters is emphazised; the major influence of the initial mean soil moisture and of the vegetation cover is pointed out. Finally, the evolution of the boundary layer in response to various surface conditions is studied.A validation of the land surface scheme is conducted through daily cycles during cloudless days. Simulated turbulent fluxes are successfully compared to micrometeorological measurements over a maize field at different growth stages. Over a pine forest, the correct simulation of the turbulent fluxes is obtained with an adequate parameterization of the surface resistance accounting for the atmospheric moisture deficit. 相似文献
997.
Javier Sánchez España Enrique López Pamo Esther Santofimia Pastor Jesús Reyes Andrés Juan Antonio Martín Rubí 《Environmental Geology》2005,49(2):253-266
The geochemical evolution of two acid mine effluents in Tharsis and La Zarza-Perrunal mines (Iberian Pyrite Belt, Huelva, Spain) has been investigated. In origin, these waters present a low pH (2.2 and 3.1) and high concentrations of dissolved sulphate and metals (Fe, Al, Mn, Cu, Zn, As, Cd, Co, Cr, Ni). However, the natural evolution of these acidic waters (which includes the bacterial oxidation of Fe(II) and the subsequent precipitation of Fe(III) minerals) represents an efficient mechanism of attenuation. This self-mitigating process is evidenced by the formation of schwertmannite, which retains most of the iron load and, by sorption, toxic trace elements like As. The later mixing with pristine waters rises the pH and favours the total precipitation of Fe(III) at pH 3.5 and, subsequently, Al compounds at pH 4.5, along with the sorption of trace metals (Mn, Zn, Cu, Cd, Co, Ni) until chemical equilibrium at circumneutral conditions is achieved. 相似文献
998.
The continuous ranked probability score (CRPS) is a much used measure of performance for probabilistic forecasts of a scalar observation. It is a quadratic measure of the difference between the forecast cumulative distribution function (CDF) and the empirical CDF of the observation. Analytic formulations of the CRPS can be derived for most classical parametric distributions, and be used to assess the efficiency of different CRPS estimators. When the true forecast CDF is not fully known, but represented as an ensemble of values, the CRPS is estimated with some error. Thus, using the CRPS to compare parametric probabilistic forecasts with ensemble forecasts may be misleading due to the unknown error of the estimated CRPS for the ensemble. With simulated data, the impact of the type of the verified ensemble (a random sample or a set of quantiles) on the CRPS estimation is studied. Based on these simulations, recommendations are issued to choose the most accurate CRPS estimator according to the type of ensemble. The interest of these recommendations is illustrated with real ensemble weather forecasts. Also, relationships between several estimators of the CRPS are demonstrated and used to explain the differences of accuracy between the estimators. 相似文献
999.
Cement-bentonite interactions will occur in deep geological repositories for high level radioactive waste. We performed laboratory experiments in order to constrain some previous geochemical and mineralogical uncertainties in the formation of secondary minerals in the high pH reaction of FEBEX bentonite at moderate temperatures.The reactivity of a Mg-homoionic FEBEX bentonite was studied at 25, 60 and 90 °C in batch reactors using two solutions representative of short and long time evolution stages of cement degradation. These solutions were periodically renewed in order to maintain a constant pH regime for a period of almost 2 years.Chabazite and merlinoite were observed to be the main zeolites that formed at 60 °C, while merlinoite was the dominant zeolite formed at 90 °C with the hyperalkaline (K-Na-OH) solution. The alkaline experiments (Ca-OH solution) showed minor reactivity and negligible mineralogical alteration, but the overall results suggest that the reaction tends to equilibrium conditions between C-S-H and montmorillonite at high temperature and metastable conditions at low temperature. The montmorillonite dissolution rates were calculated for all experiments, showing good agreement with previous calculations. 相似文献
1000.
Surface and groundwater pollution by organochlorine compounds in a typical soybean system from the south Pampa,Argentina 总被引:3,自引:0,他引:3
Mariana Gonzalez Karina S. B. Miglioranza Valeria M. Shimabukuro Orlando M. Quiroz Londoño Daniel E. Martinez Julia E. Aizpún Víctor J. Moreno 《Environmental Earth Sciences》2012,65(2):481-491
Organochlorine pesticides (OCPs) use has been restricted or forbidden in Argentina since 1998 and technical endosulfan is
the last currently used OCPs on the soybean-wheat production. As they persist in soil for several years after application,
OCPs constitute a source of environmental pollution. This work aims to assess OCPs contamination of groundwater (Gw) and streamwater
(Sw) in the Quequén Grande River watershed from south Argentinean Pampas in relation to the hydrogeological characteristics.
OCPs were analyzed in Sw, Gw, surface bottom sediments, soils and borehole cutting sediments (Cs) by gas chromatograph-electron
capture detector. Pesticide distribution in Cs was dependent on the characteristic of the non-saturated zone. Leached pesticides
over 3 m in Cs showed the pattern: HCHs = endosulfan > chlordanes > DDTs, and from 3 to 6 m heptachlor was the main group
as a consequence of the past use of this compound in the area, mainly on potato crops. Endosulfan reaches Gw during application
season as well as during flooding events while a retard effect was observed for Sw. Levels of α- and β-isomers were in certain
cases above national (7 ng L−1) and international (3 ng L−1) limits for aquatic biota protection. As the endosulfan sulfate metabolite was present in Gw and Sw and due to its high toxicity,
it should be considered in the establishment of water quality criteria for human and environmental protection. 相似文献