Geochemical modeling and low-frequency geoelectrical methods to evaluate the impact of an open dump in arid and deltaic environments     

Francisco?Javier?Gómez-Puentes  Marco?Antonio?Pérez-Flores  Jaime?Alonso?Reyes-LópezEmail author  Dina?L.?Lopez  Fernando?Herrera-Barrientos  Rafael?Onofre?García-Cueto  Socorro?Romero-Hernández  Fernando?Amílcar?Solís-Domínguez  Miguel?Martín-Loeches Garrido 《Environmental Earth Sciences》2016,75(13):1062

In Mexico, open dumps that are maintained by the municipality but provide no covering of waste are not uncommon. Further, disposal at these sites is often performed by burning. The aim of this study was to determine the leachate plume from an open dump located in a depositional deltaic environment, with arid climate, low rainfall and where the water table is about 2 m below the surface. The methodology comprised analysis of groundwater monitoring wells and geophysical and geochemical prospecting techniques. The 3D geoelectric interpretation shows a typical area of these depositional environments with low resistive values (10–20 Ω-m) associated with the presence of sands and clays interbedded. However, there is a very low resistivity zone associated with the dump’s impact which reaches values below 5 Ω-m, and it is located where the disposal and burning of wastes occurred. Another zone with values above 16 Ω-m appears as a limit for the advance of the saline. This is interpreted as a sandy lenses area. These sandy lenses with higher porosity transport aquifer’s water. Thus the dump is in direct contact by this conduct with clean groundwater. Piper diagrams constructed with the chemical data analysis reveal that the groundwater in the area corresponds to the chlorinated and/or sulfated sodium type, showing the impact caused by the dump. The monitoring well (NP8, on-site) with the highest dissolved solids content behaves anomalously and belongs to the more conductive zone according to the geoelectric profiles. The subsoil geochemical behavior is influenced by the seasonal water table variations provoking the dissolution of burned and unburned wastes, but the effects of slow flows in the direction of the regional flow are not discarded. Although the most impacted area within the dump is characterized to a depth of 10 m, there is a slow flow in the direction of the regional flow that has been moving pollutants out of the dumpsite during its almost 20 years of operation. The results of this study provide valuable information for the authorities to carry out an appropriate restoration project.  相似文献   

Geoarchaeology and Construction of the La Chabola de la Hechicera Megalithic Tomb,Elvillar, Northern Spain     

Luis M. Martínez‐Torres  Javier Fernndez‐Eraso  Jos A. Mujika‐Alustiza  lvaro Rodríguez‐Miranda  Jos M. Valle‐Meln 《Geoarchaeology》2014,29(4):300-311

La Chabola de la Hechicera, a Neolithic collective tomb which was first used at ca. 3850 B.C., has been re‐excavated for interpretation and stabilization. Information about the sources, handling, and placement of building materials allowed determination of the methods used to construct the dolmen monument. All of the rocks used in the structure are local Miocene sandstones, and the slabs were probably taken directly from the base of natural slopes near the monument. The chamber slabs were not carved, but some passage slabs were retouched to level the cover slabs. Fragments for the tumulus were obtained by mechanical fracturing. All of the slabs are imbricated, making it possible to determine the order in which they were placed. Thus, the identification of building materials and their mode of placement allows for the reconstruction of each stage of the building of the monument, providing unusually rich data for understanding the geoarchaeology and building archaeology of a dolmenic structure.  相似文献   

Morphology and geology of the continental shelf and upper slope of southern Central Chile (33°S–43°S)     

David Völker  Jacob Geersen  Eduardo Contreras-Reyes  Javier Sellanes  Silvio Pantoja  Wolfgang Rabbel  Martin Thorwart  Christian Reichert  Martin Block  Wilhelm Reimer Weinrebe 《International Journal of Earth Sciences》2014,103(7):1765-1787

The continental shelf and slope of southern Central Chile have been subject to a number of international as well as Chilean research campaigns over the last 30 years. This work summarizes the geologic setting of the southern Central Chilean Continental shelf (33°S–43°S) using recently published geophysical, seismological, sedimentological and bio-geochemical data. Additionally, unpublished data such as reflection seismic profiles, swath bathymetry and observations on biota that allow further insights into the evolution of this continental platform are integrated. The outcome is an overview of the current knowledge about the geology of the southern Central Chilean shelf and upper slope. We observe both patches of reduced as well as high recent sedimentation on the shelf and upper slope, due to local redistribution of fluvial input, mainly governed by bottom currents and submarine canyons and highly productive upwelling zones. Shelf basins show highly variable thickness of Oligocene-Quaternary sedimentary units that are dissected by the marine continuations of upper plate faults known from land. Seismic velocity studies indicate that a paleo-accretionary complex that is sandwiched between the present, relatively small active accretionary prism and the continental crust forms the bulk of the continental margin of southern Central Chile.  相似文献   

Metal accumulation by plant species growing on a mine contaminated site in Mexico     

Ofelia Morton-Bermea  Juan Miguel Gómez-Bernal  María Aurora Armienta  Rufino Lozano  Elizabeth Hernández-Álvarez  Francisco Romero  Javier Castro-Larragoitia 《Environmental Earth Sciences》2014,71(12):5207-5213

The present work aims to assess the efficiency of heavy metal accumulation of native species growing in contaminated soils in the mining district of Taxco, Mexico. Soil and tailing sampling was conducted in three study sites: La Concha, El Fraile, and a control site. The study localities present diverse metal concentrations with significant differences in their proportion in the geochemical fractions. Results show that species Cupressus lindleyi and Juniperus deppeana accumulate Zn and Mn in anomalous concentrations at La Concha, where Zn is present in soluble fractions. Manganese, despite not being present mostly in the soluble fraction in soils and tailings, seems to have been increased in the soluble fraction after the plant growth. In contrast, samples of the same species taken at El Fraile and in the control site, where Zn and Mn are mainly contained in the residual fraction, do not show an anomalous enrichment. Other analyzed species growing under the same contamination conditions in La Concha (Jacaranda mimosifolia and Psidium guajava) do not show anomalous concentrations. These facts confirm the Zn and Mn accumulation capacity of C. lindleyi and Ju. deppeana, which depends on their accumulation ability and on the concentration of these elements in the soluble fraction.  相似文献   

Homogeneous reprocessing of GPS,GLONASS and SLR observations   总被引：3，自引：2，他引：1  

Mathias Fritsche  Krzysztof Sośnica  Carlos Javier Rodríguez-Solano  Peter Steigenberger  Kan Wang  Reinhard Dietrich  Rolf Dach  Urs Hugentobler  Markus Rothacher 《Journal of Geodesy》2014,88(7):625-642

The International GNSS Service (IGS) provides operational products for the GPS and GLONASS constellation. Homogeneously processed time series of parameters from the IGS are only available for GPS. Reprocessed GLONASS series are provided only by individual Analysis Centers (i. e. CODE and ESA), making it difficult to fully include the GLONASS system into a rigorous GNSS analysis. In view of the increasing number of active GLONASS satellites and a steadily growing number of GPS+GLONASS-tracking stations available over the past few years, Technische Universität Dresden, Technische Universität München, Universität Bern and Eidgenössische Technische Hochschule Zürich performed a combined reprocessing of GPS and GLONASS observations. Also, SLR observations to GPS and GLONASS are included in this reprocessing effort. Here, we show only SLR results from a GNSS orbit validation. In total, 18 years of data (1994–2011) have been processed from altogether 340 GNSS and 70 SLR stations. The use of GLONASS observations in addition to GPS has no impact on the estimated linear terrestrial reference frame parameters. However, daily station positions show an RMS reduction of 0.3 mm on average for the height component when additional GLONASS observations can be used for the time series determination. Analyzing satellite orbit overlaps, the rigorous combination of GPS and GLONASS neither improves nor degrades the GPS orbit precision. For GLONASS, however, the quality of the microwave-derived GLONASS orbits improves due to the combination. These findings are confirmed using independent SLR observations for a GNSS orbit validation. In comparison to previous studies, mean SLR biases for satellites GPS-35 and GPS-36 could be reduced in magnitude from \(-35\) and \(-38\)  mm to \(-12\) and \(-13\)  mm, respectively. Our results show that remaining SLR biases depend on the satellite type and the use of coated or uncoated retro-reflectors. For Earth rotation parameters, the increasing number of GLONASS satellites and tracking stations over the past few years leads to differences between GPS-only and GPS+GLONASS combined solutions which are most pronounced in the pole rate estimates with maximum 0.2 mas/day in magnitude. At the same time, the difference between GLONASS-only and combined solutions decreases. Derived GNSS orbits are used to estimate combined GPS+GLONASS satellite clocks, with first results presented in this paper. Phase observation residuals from a precise point positioning are at the level of 2 mm and particularly reveal poorly modeled yaw maneuver periods.  相似文献   

Enhancement of the benthic communities around an isolated island in the Antarctic Ocean     

Jos&#; I Saiz  Nuria Anad&#;n  Javier Cristobo  Oscar Garc&#;a-Alvarez  Gerardo Garc&#;a-Castrillo  Eduardo L&#;pez  Cruz Palac&#;n  Jes&#;s S Troncoso  Ana Ramos 《海洋学报(英文版)》2013,32(6):47-55

Insular marine biotas are often richer in faunal diversity than those from the open sea in the same geographical region. The existence of particular island effects were tested under polar conditions by comparing infaunal benthic assemblages on Peter I Island with those of similar latitudes in the open ocean at the Bellingshausen Sea and also from the coast of the Antarctic Peninsula. Sampling was carried out aboard the R/V Hespérides during the expedition named BENTART-2003 from 24 January to 3 March 2003. Benthic samples were collected at 18 stations ranging from 90 to 2 044 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 32 higher taxa of invertebrates were found. Univariate and multivariate analyses revealed various patterns in the data. First, significant differences in polychaete abundance were detected between the stations located in the open sea and the remaining sites (island plus mainland sites). Bivalve abundances were also distinct between island and mainland sampling sites. Sediment columns taken from the island seafloor exhibited the highest rate of bioturbation by the infauna. These findings confirm the model that islands develop distinct assemblages characterized by the enhancement of the benthic communities even in cold waters. Several abiotic factors were measured simultaneously at the seafloor and along the water column to investigate faunal distribution patterns. Significant correlations were found between the benthic assemblages and a combination of two environmental variables: "island effect" (measured as a categorical variable) and the redox state of sediments. Richer and more complex benthic assemblages were found in Peter I Island’s sea bottom, whereas the more depauperate bottoms remained in the open sea.  相似文献