Preference ratios for mercury and other chemical elements in the Madeira River, Brazil     

Daniel Marcos Bonotto  Ene Glria da Silveira 《Journal of South American Earth Sciences》2003,15(8):911-923

Samples of water, suspended solids, and bottom sediments from the Madeira River, Rondônia state, Brazil, were physically and chemically analyzed to investigate the actual Hg mobilization in the aquatic environment and compare it with that of other heavy metals and elements in the area. Two dimensionless Hg preference ratios were defined, expressing (1) the ratio of Hg and other elements in the liquid phase divided by the ratio of Hg and other elements in bottom sediments (P_l.phase) and (2) the ratio of Hg and other elements in the particulate matter divided by the ratio of Hg and other elements in bottom sediments (P_s.solids). These preference ratios are useful for comparing Hg transport in three different phases (liquid, particulate matter, and bottom sediments). They also were applicable to any analyzed element in the area studied, because they generated an almost constant value when the maximum calculated was divided by the minimum (P_l.phase=2931; P_s.solids=84) and because of their sensitivity to the dominance of sorption processes by Fe oxides and hydroxides. Mercury could be transported preferentially to other analyzed elements in the particulate phase only if its concentration reached values at least 10⁴-fold higher than those expected or quantified in the area.  相似文献   

Temporary exposures of the Eocene London Clay Formation at Highgate, north London: rediscovery of a fossiliferous horizon ‘lost’ since the nineteenth century     

Steve TraceyStephen K. Donovan  Diana ClementsJohn Cooper  Phil RyeCaroline Hensley 《Proceedings of the Geologists' Association. Geologists' Association》2002,113(4):319-331

  相似文献   

The UK Climate Change Programme and communication with local authorities     

David Demeritt  Diana Langdon 《Global Environmental Change》2004,14(4):271

Drawing on results of a 2003 survey of environmental officers in every Local Authority (LA) in England and Wales, this paper assesses the reception and response of local government to the information being provided through the UK Climate Change Programme. Over three quarters of respondents (n=184) felt they did not have access to the best information about the impacts of climate change on their areas. Although up-to-date information is freely available from a number of official Government sources, those official sources are not consulted as consistently as the media or as intensively as the internet, despite being consistently regarded as much more accurate, credible, and appropriate to LA needs. We interpret this apparent contradiction between LA officer confidence in official sources and their relatively infrequent use as a consequence, first, of technical–cognitive and practical–temporal difficulties accessing and understanding official sources of climate change information and, second, of concerns about the practical relevance of that information for the administrative functions of local government and thus for any meaningful response by LAs to climate change. Our survey recorded considerable levels of stress, cynicism, and futility among LA officials that not only complicate communication efforts but also call into question the central assumption of the UK Climate Change Programme that simply making more locally specific information about climate change impacts available will motivate appropriate action.  相似文献   

Indigenous knowledge and the desertification debate: problematising expert knowledge in North Africa     

Diana K. Davis 《Geoforum》2005,36(4):509-524

In Morocco the crisis narrative of desertification has been invoked for decades to facilitate and justify policy and legal changes that have systematically disadvantaged pastoralists and damaged the environment. The existing data from southern Morocco, however, do not support the claims of widespread desertification due to overgrazing or other pastoral activities. Furthermore, many anti-desertification and range improvement projects in southern Morocco have not succeeded. In an effort to rethink desertification and range ecology in Morocco, this paper presents an overview of the indigenous knowledge of range ecology among the Aarib, a group of camel pastoralists in southern Morocco, and compares it to the “expert” knowledge of Moroccan range managers. It suggests that this expert knowledge is based on questionable evidence and that it has been privileged over local knowledge primarily for political, economic and administrative reasons. The discrepancies between expert and indigenous knowledges of range ecology presented here underscore the need to reconsider range ecology in Morocco, taking indigenous ecological knowledge into account. Doing so may point the way to more successful development and conservation projects which are more environmentally appropriate and socially just. Not doing so will likely exacerbate environmental degradation in the region.  相似文献   

Radium isotopes in river sediments of Czech Republic     

Eduard Hanslík  Eva Kalinov  Martina Brtvov  Diana Ivanovov  Barbora Sedl&#x;ov  Jitka Svobodov  Vra Jedinkov-K&#x;íov  Mark Rieder  Ji&#x;í Medek  Karel Forejt  Ladislav Vondrk  Karel Jahn  Ji&#x;í Jusko 《Limnologica》2005,35(3):177-184

In the Czech Republic, river bottom sediments have been systematically monitored since 1999. In the paper, their radioactive contamination due to uranium mining and milling is assessed. The sediments samples were analyzed by gamma spectrometry. Especially the radium-226 and radium-228 activities were further evaluated.The highest values of the radium-226 activities were found at river profiles where the uranium industry impact was obvious. It turned out that the radium-226 and radium-228 activities ratio is more convenient to assess the level of radium-226 contamination than only the radium-226 activity itself. Based on this hypothesis, the sediment classification scheme for uranium industry contamination was suggested. The natural background activities of radium-226 and radium-228 in the Czech Republic were also evaluated. The case of radium-226 contamination due to the uranium industry was studied in details at the Ploučnice River.  相似文献   

Rock magnetic properties of recent soils from northeastern Bulgaria   总被引：1，自引：0，他引：1  

Diana Jordanova  Eduard Petrovsky  Neli Jordanova  Jordan Evlogiev  Vesselina Butchvarova 《Geophysical Journal International》1997,128(2):474-488

In this paper, basic rock magnetic studies of Holocene loess-soil samples from northeastern Bulgaria are reported. The sites are related to the Danube river and located at different distances southwards, thus representing various pedogenic conditions. The study is primarily aimed at determining the main magnetic carrier(s) and their physical characteristics (grain-size distribution, magnetic enhancement, etc.). Oxyhydroxides, maghemite and titanomagnetites of various oxidation degrees are assumed to be the main ferromagnetic minerals present. Our results suggest that the uppermost part of recent soil profiles is rich in stable, near-single-domain (SD) particles, while the illuvial horizons are characterized by a gradual decrease in grain sizes, from highly viscous to a true superparamagnetic (SP) domain state. The properties of samples from carbonate-rich horizons of recent soils are basically controlled by detrital minerals, while those from sites with more intensive pedogenesis and especially grey forest soils are influenced by strongly magnetic minerals formed ' in situ '.  相似文献   

In situ experimental study of the evolution and recolonization of polluted sediments     

A. Arnoux  G. Stora  C. Diana 《Marine pollution bulletin》1985,16(8):313-318

When perturbing conditions influencing a benthic ecosystem improve, an extremely polluted sediment may very rapidly be colonized by a structured assemblage. This study was made after the implantation of modules containing chemically very contaminated sediment from a polluted biotope, in a lesser contaminated site. The colonization and dynamic processes of the studied mollusc populations do not depend on the concentrations of the solid phase pollutants but are related to the release of these pollutants in the interstitial water of sediments, which in turn is induced by ambiant condition variations and particularly by salinity.  相似文献   

Characteristics of the secular variation of the geomagnetic field between 1964–1981 in Romania     

C. Demetrescu  M. Andreescu  M. Ene  T. Neştianu 《Physics of the Earth and Planetary Interiors》1985,37(1):46-51

The variation of the H, Z, and T components of the geomagnetic field at repeat stations on Romanian territory between 1964 and 1981 is discussed in terms of internal secular and solar cycle related variations. Their geographical distribution is accounted for by the magnetic and electric structure of the interior of the Earth. The effects of magnetic and electromagnetic induction caused by the solar cycle related variation were evaluated.  相似文献   

P–T–t conditions of high-grade metamorphic rocks of the Garzon Massif, Andean basement, SE Colombia     

Diana María Jimnez Mejía  Caetano Juliani  Umberto G. Cordani 《Journal of South American Earth Sciences》2006,21(4):322

The metamorphic evolution of the Garzón Massif, Colombia, is established on the basis of the textural, goethermobarometric, and geochronological relationships of the metamorphic minerals. The geothermobarometric data define a clockwise, nearly isothermal decompression path (ITD) for rocks from Las Margaritas migmatites, constrained by four P–T areas: 780–826 °C and 6.3–8.0 kbar, 760–820 °C and 8.0–8.8 kbar, 680–755 °C and 6.6–9.0 kbar, and 630 °C and 4 kbar. For the a garnet-bearing charnockitic gneiss from the Vergel granulites, the path is counterclockwise, constrained by geothermobarometric data of 5.3–6.2 kbar and 700–780 °C and 6.2–7.2 kbar and 685–740 °C. The clockwise ITD path represents a loop followed by the orogen during the transitional granulite–amphibolite metamorphic conditions, probably associated with a subduction process followed by a collisional tectonic event. This subduction framework produced continental crust thickening between 1148 and 1034 Ma and later collision with another continental block approximately 1000 Ma ago. The orogenic exhumation occurred with moderate uplift rate. The counterclockwise trajectory and two metamorphic events suggest a vertical displacement between the Vergel granulites and Las Margaritas migmatites units, because there is no isotopic difference that indicates the existence of different terranes. The data confirm that the metamorphic evolution for this domain was more dynamic than previously believed and includes: (1) metamorphic processes with the generation of new crust with a possible mixture of old material and (2) metamorphic recycling of continental crust. These geological processes characterize a complex Mesoproterozoic orogenic event that shares certain features with the Grenvillian basement rocks participating in the formation of Rodinia.  相似文献   

Amplitude and frequency characteristics of the 2001 Southern Peru, M w = 8.4 earthquake records     

Rubén L. Boroschek  Diana Y. Comte 《Journal of Seismology》2006,10(3):353-369

The Departments of Civil Engineering and Geophysics of the University of Chile, together with international institutions, deployed strong-motion stations in the northern Chile seismic gap. These instruments recorded the June 23, 2001 M _w = 8.4 earthquake that occurred in Southern Peru. This earthquake exhibited at stiff deep soil sites in northern Chile, relatively large maximum accelerations although the recording stations are located more than 400 km away from the epicentral region and 200 km from the southern edge of the rupture. Typical accelerations at these distances are in the order of 0.30 g, consIDerably larger than those expected from recently presented attenuation formulae. Frequency and Wavelet Decomposition of the signals are presented from which the evolution of the amplitude, as a function of selected frequency bands, is analyzed. Typical Central Frequency varies from 3 to 4.8 Hz for horizontal records and 4.5 to 9.5 Hz for vertical records. Ninety five percent of the record energy is concentrated below 11 Hz. Evolution of energy for bands higher than the average record frequency is relatively smooth, and for low frequency, the energy shows abrupt changes as a function of time. The sudden changes are associated to dominant large amplitude motions observed in most of the records. The high frequency content of the motion observed for this earthquake is correlated with the heterogeneities of the interplate contact. To statically characterize the energy evolution with time a smooth three-parameter envelope adjusted for each frequency band is used, therefore, comparison is possible and results could be applied for synthesis studies.  相似文献