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51.
52.
Isabel Egea-González Javier Ruiz Carlos Fernández Jean-Pierre Williams Álvaro Márquez Luisa M. Lara 《Planetary and Space Science》2012,60(1):193-198
Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittle–ductile transition (BDT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for which Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury.The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m?2 for the Kuiper region, and between 22 and 43 mW m?2 for Discovery Rupes. Both BDT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation. 相似文献
53.
Maria Fernanda Alvarez Margarita Luisa Osterrieth Julio Luis del Río 《Environmental Earth Sciences》2012,65(2):505-515
Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological
properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies
of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as
possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredón, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a)
cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA),
and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in
SOC (7.2–8.6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates
(5.6–10% and 6.9–13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical
aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3–0.5%). Fulvic
acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial
decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the
aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for
more than 50 years. 相似文献
54.
Ana Carolina Ruiz-Fernández Mario Sprovieri Mauro Frignani Joan Albert Sanchez-Cabeza Maria Luisa Feo Luca Giorgio Bellucci Libia Hascibe Pérez-Bernal Michel Preda María Luisa Machain-Castillo 《Environmental Earth Sciences》2012,67(3):727-742
The Isthmus of Tehuantepec corresponds to the shortest distance (~200?km) between the Gulf of Mexico and the Pacific Ocean in Southern Mexico, and the main economical activity of this region is oil extraction and refining. Polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) were determined in a 210Pb dated sediment core collected from the continental shelf of Tehuantepec Gulf, in the vicinity of the oil refinery of Salina Cruz, Oaxaca, the main oil refining facility of the country. The sediments were mostly of coarse nature and hence PAHs and TPHs concentrations throughout the core (61?C404???g?g?1 and 29?C154?mg?kg?1, respectively) were below international quality benchmarks. Depth profiles of both PAHs and TPHs concentrations showed increasing trends since the early 1900s but the higher values were found from the 1950s to present. PAH congener ratios showed that these contaminants had both petrogenic and pyrolitic sources, although the former has been predominant since the 1970s. The Salina Cruz refinery started operations in 1978 but the oil industry activities in the Tehuantepec Isthmus go back to the beginning of the twentieth century with the operation of Minatitlan refinery in the Gulf of Mexico, and the Gulf of Tehuantepec being the main conduit for oil distribution in the Pacific coast. The observed changes in contaminant distributions described well the oil industry development in the area. 相似文献
55.
Luisa?Frati Giorgio?Brunialti Stefano?LoppiEmail author 《Journal of Atmospheric Chemistry》2005,52(3):221-230
The results of a transplant experiment with the fruticose lichen Evernia prunastri aimed at monitoring the trends of trace elements deposition in a repeated biomonitoring study are reported. Data comparability
between the two surveys and interpretation of the results were addressed in this study. The ratio between the concentration
of each element after the exposure and in control samples prior to exposure (exposed-to-control ratio, EC ratio), as well
as an appropriate interpretative scale, were adopted as a means of determining the temporal trends of element accumulation
by lichen transplants. The results showed that the method adopted is indeed a reliable tool, pinpointing a Zn smelting plant
and an oil refinery as principal pollution sources in the area, which indicate that elements associated with the former were
similarly accumulated in both 2002 and 2003, while elements associated with the latter tended to decrease in 2003. 相似文献
56.
Response of antioxidant systems to copper in the gills of the clam Ruditapes decussatus 总被引:1,自引:0,他引:1
Copper (Cu) is an essential element for biological systems, however, when present in excess, is toxic. Metallothioneins can play an important role in Cu homeostasis and detoxification. Moreover, Cu can catalyse the production of toxic hydroxyl radicals that cause lipid peroxidation but defence systems in the cells can limit the oxidative damage. The present study was performed to investigate the effect of three Cu concentrations (0.5, 2.5 and 25 microg l(-1)) on the response of antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathion peroxidase and total glutathion peroxidase), total proteins, metallothioneins (MT), malondialdehyde (MDA) concentrations in the gills of the clam, Ruditapes decussatus. The activity of antioxidant enzymes and total proteins, MT and MDA concentrations were measured in the gills of the clams after 1, 3, 7, 14, 21 and 28 days of Cu exposure. Results indicate that Cu only induces an imbalance in the oxygen metabolism during the first week of Cu exposure due to a decrease in mitochondrial SOD and CAT, selenium-dependent and total glutathion peroxidase activities. Cu also causes lipid peroxidation, measured by the MDA formation, that was Cu dependent. In the gills of clams exposed to 25 microg Cu/l, the excess of Cu triggers the induction of MT synthesis after 3 days of exposure. 相似文献
57.
Luisa Stellato Emma Petrella Filippo Terrasi Paolo Belloni Maria Belli Umberto Sansone Fulvio Celico 《Hydrogeology Journal》2008,16(4):701-712
222Rn was used to assess river–groundwater interactions within Castel di Sangro alluvial aquifer (Italy). The effectiveness of results obtained through this indicator was verified by also analyzing δ18O, major ions and temperature in both surface and groundwater, and carrying out piezometric head monitoring and discharge measurements. Hydrogeological investigations suggested that the river infiltrates into the aquifer in the south-eastern aquifer portion, while groundwater discharges into the river in the north-eastern portion. The latter phenomenon is supported by 222Rn data. Nevertheless, flow-through conditions cause the modelled discharge along this river reach, estimated by 222Rn data in a degassing-corrected two-component mixing model, to be greater than the measured discharge. Concerning river infiltration into the aquifer, δ18O, major ions and temperature data show that the river contribution is negligible in terms of aquifer recharge. Thus, the observed increase in 222Rn concentration in that portion of the aquifer is due to the enrichment process caused by infiltration of rainwater (222Rn free) which flows from the local divide area. Hence, in the study site, the use of only 222Rn to predict river–groundwater interactions causes some estimation inaccuracies and it must be coupled with other hydrochemical and hydrogeological parameters to gain a thorough understanding of such interactions. 相似文献
58.
Sebastian Vicuña Jorge Gironás Francisco Javier Meza María Luisa Cruzat Mark Jelinek Eduardo Bustos 《水文科学杂志》2013,58(8):1598-1619
AbstractMotivated by recent extreme flow events in the Mataquito River located in the Mediterranean region of Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow, precipitation and temperature within the basin. For the period 1976–2008, positive trends in temperature were observed, especially during spring and summer months. At the same time, we found negative trends in the frequency and intensity of precipitation, especially during spring months. We observed an increasing difference between average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is caused by larger flows during autumn months, although no positive precipitation trends are observed for these months. Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration of high-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen during autumn months, and are associated with high precipitation and high minimum temperatures. Based on a simple assessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem not to be as relevant to the detected flow trends. All these results are in accord with future climate change scenarios that show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation. Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifying also a fate that may be shared by other similar basins in Chile and in other regions of the world.Editor Z.W. KundzewiczCitation Vicuña, S., Gironás, J., Meza, F.J., Cruzat, M.L., Jelinek, M., Bustos, E., Poblete, D., and Bambach, N., 2013. Exploring possible connections between hydrological extreme events and climate change in central south Chile. Hydrological Sciences Journal, 58 (8), 1598–1619. 相似文献
59.
Eduardo M. García-Roger M. del Mar Sánchez-Montoya Rosa Gómez M. Luisa Suárez M. Rosario Vidal-Abarca Jérôme Latron Maria Rieradevall Narcís Prat 《Aquatic Sciences - Research Across Boundaries》2011,73(4):567-579
In this study we examined the importance of seasonal changes in habitat features and aquatic macroinvertebrate responses in
temporary and perennial streams from two different catchments in the Western Mediterranean region in Spain. Macroinvertebrate
sampling was spatially intensive to account for the relative frequency of meso- (i.e., riffles and pools) and micro-habitats
(i.e., different mineral and organic-based substrata) at each site. Samples were collected at two distinctly different phases
of the hydrograph: (1) during the flowing period, when pool-riffle sequences were well-established, and (2) during the dry
phase, when only isolated pools were expected to occur in the temporary streams. During the dry season, both a reduction in
the available total habitat and in microhabitat diversity in all sites studied was observed. As a result, taxon richness decreased
in all streams, but more dramatically at temporary stream sites and particularly so in the infrequently remaining discontinuous
riffles. Macroinvertebrate assemblages differed among catchments (i.e., geographical identity) and sites (perennial vs. temporary).
Invertebrate differences were also strong within and among meso- and micro-habitats, particularly mineral and organic microhabitat
patches, and differences were due to both loss of taxa from some habitats and some taxa exhibiting certain habitat affinities. 相似文献
60.
Gomiero A Da Ros L Nasci C Meneghetti F Spagnolo A Fabi G 《Marine pollution bulletin》2011,62(11):2483-2495
Despite a large number of gas platforms existing in the Adriatic Sea, which is a semi-enclosed basin characterized by a slow turnover rate and increasing industrial as well as other anthropogenic activities, the effects of these structures on the aquatic ecosystem require further investigation. Since 1998, multidisciplinary studies have been performed by CNR-ISMAR to comply with legislation and to support the development of protocols for the monitoring of offshore activities in the Adriatic Sea. The present study was developed to implement a biomonitoring plan to assess the ecotoxicological effects of the extraction activities of an off-shore gas platform. Biomarkers were evaluated in mussels collected from the platform in relation to physiological stress, DNA damage, cellular damage, oxidative stress and exposure effects. Organic contaminants and trace element bioaccumulation were also assessed in the soft body of the mussels to correlate bioaccumulation of pollutants with biomarker responses. The results indicate an absence of platform-related environmental stress. 相似文献