Hydraulic conductivity characterization of a karst recharge area using water injection tests and electrical resistivity logging     

Bárbara Angulo  Tomás Morales  Jesús A. Uriarte  Iñaki Antigüedad 《Engineering Geology》2011,117(1-2):90-96

Water injection tests and electrical logging are particularly useful techniques in the characterization of geological media in engineering works. In this paper these techniques in conjunction with cracks measurements obtained from drilling cores, were used in the characterization of a singular location in a karst massif. The aim of our work is to determine the hydraulic characteristics of the investigated site, as well as to establish the relationship between the data obtained by the different techniques used. Thus, electrical resistivity records and fracture data were obtained from two boreholes of 100 and 120 m depth. Hydraulic conductivity was calculated from 25 low-pressure water injection tests (LPT) carried out at different depths in both boreholes. The relationship between hydraulic conductivity and fracture frequency was not very statististically significant (R²: 0.062–0.672; σ_est: 0.61–1.575). Conversely, electrical resistivity and hydraulic conductivity had a great relationship (R²: 0.725–0.935; σ_est: 0.159–0.738), so the electrical resistivity may be related to the functionality of the fractures. Finally, the LPT is shown as a very practical tool for determining the degree of the hydraulically interconnection with the surroundings, for establishing the hydraulic conductivity profile and for obtaining a measure of soil erosionability according to the significance of the fracture washing out processes recorded.  相似文献   

Plastic ingestion in Franciscana dolphins, Pontoporia blainvillei (Gervais and d'Orbigny, 1844), from Argentina     

Denuncio P  Bastida R  Dassis M  Giardino G  Gerpe M  Rodríguez D 《Marine pollution bulletin》2011,62(8):1836-1841

Plastic debris (PD) ingestion was examined in 106 Franciscana dolphins (Pontoporia blainvillei) incidentally captured in artisanal fisheries of the northern coast of Argentina. Twenty-eight percent of the dolphins presented PD in their stomach, but no ulcerations or obstructions were recorded in the digestive tracts. PD ingestion was more frequent in estuarine (34.6%) than in marine (19.2%) environments, but the type of debris was similar. Packaging debris (cellophane, bags, and bands) was found in 64.3% of the dolphins, with a lesser proportion (35.7%) ingesting fishery gear fragments (monofilament lines, ropes, and nets) or of unknown sources (25.0%). PD ingestion correlated with ontogenetic changes in feeding regimes, reaching maximum values in recently weaned dolphins. Because a simultaneous increase in gillnet entanglement and the bioaccumulation of heavy metals take place at this stage, the first months after trophic independence should be considered as a key phase for the conservation of Franciscana dolphin stocks in northern Argentina.  相似文献   

Seasonal and diel patterns of total gaseous mercury concentration in the atmosphere of the Central Valley of Costa Rica     

Aylin CastilloJuan Valdes  Jose SibajaIlena Vega  Rosa AlfaroJosé Morales  Germain EsquivelElisa Barrantes  Paleah BlackDavid Lean 《Applied Geochemistry》2011,26(2):242-248

Monitoring of Hg in the atmosphere near volcanoes is limited with no previous data for Costa Rica. Seasonal and daily patterns of total gaseous mercury (TGM) were observed at the main sampling location at the Universidad Nacional, Heredia, Costa Rica. The area (lat. 10.000230 long. −84.109499) is located in the Central Valley of Costa Rica and is 27 km SE of the Poas volcano (lat. 10.199486 long. −84.231388). Measurements were made from May 2008 to May 2009 at this location with some additional values obtained at other sites near the Poas volcano including San Luis and Grecia as well as near, Turrialba and Irazu volcanoes. Total gaseous Hg was determined in samples collected at a height of 2 m using the Tekran 2537A (Tekran Inc.) gas-phase Hg vapor analyzer. Meteorological data (temperature, relative humidity, wind speed, wind direction, radiation and precipitation) were obtained from the airport weather station located at Alajuela. Monthly precipitation is typically 85 mm during the dry season (December to April) with winds from the west. The wet season begins in late April and continues to December with monthly rainfall of 328 mm and winds from the NE. The annual mean temperature is 20 °C. With the onset of the wet season TGM increased from typical values near 10 to 905 ng m⁻³. Measurements made within 5 km of the Poas volcano were higher than at Heredia at that time. Diel values measured at the university site increased until midday along with temperature and radiation. Relative humidity showed a reciprocal pattern. It was found that high values of TGM were not related to wind velocity or direction. The strong diel pattern increased with sunrise, peaked at midday and was lowest during the night time. It would seem that Hg⁰ from the volcano is oxidized and is deposited to the soils during the dry season when winds are blowing from the volcano. With the onset of heavy rains in April, Hg in the soil is reduced and re-volatilized resulting in the high levels in the atmosphere. Values at other volcano sites were provided. The role of atmospheric pollutants such as H₂O₂ and O₃ should be included in future studies as they may result in oxidation of reduced Hg. The instability in the air masses may also be a factor and local pollution sources may result in high levels that is emitted from the volcanoes of Hg being circulated to ground level as radiation intensity increases.  相似文献   

Dolomitic slates from Uruguay: petrophysical and petromechanical characterization and deposit evaluation     

Manuela Morales Demarco  Pedro Oyhantçabal  Karl-Jochen Stein  Siegfried Siegesmund 《Environmental Earth Sciences》2013,69(4):1361-1395

Slates are internationally known as roof and façade-cladding material since prehistoric times. The methods required to mine and manufacture these dimensional stones are relatively simple in comparison to those utilized in granitic dimensional stones. This has led to a worldwide rentable commercialization of slate in the last centuries and also to the development of characteristic cultural landscapes. In Uruguay several slates are mined and used in architecture, especially as façade cladding and floor slabs. The most important slates regarding their production and utilization are the dolomitic slates. These dolomitic slates are associated with the Neoproterozoic thrust and fold belt of the Dom Feliciano belt. Representative samples have been geochemically and petrographically characterized, as well as petrophysically and petromechanically analyzed. The petrophysical and petromechanical properties were investigated in a very systematic way with respect to the new European standards, showing values comparable to those registered for internationally known slates. Detailed structural and deposit analysis were carried out in Uruguay in order to evaluate the dolomitic slate deposits. The slates are linked to calc-silicate strata in a greenschist facies volcano-sedimentary sequence and the deposits are located in the limb of a regional fold, where bedding and cleavage are parallel. The main lithotype is a layered and fine-grained dolomitic slate with a quite diverse palette of colors: light and dark green, gray, dark gray, reddish and black. The mined slate is split into slabs 0.5–2 cm thick. In the past, the average production in Uruguay was around 4,000 tons/year and a historical maximum of 13,000 tons was reached in 1993 (Oyhantçabal et al. in Z dt Ges Geowiss 158(3):417–428, 2007). The oscillations in the regional demand were the cause of several flourishing and decay cycles in the activity, but our investigation shows a considerable volume of indicated resources and therefore a very good potential.  相似文献   

Uptake and Accumulation of Arsenic in Different Organs of Carrot Irrigated with As‐Rich Water     

Paloma Mayorga  Amelia Moyano  Hossain M. Anawar  Antonio Garcia‐Sanchez 《洁净——土壤、空气、水》2013,41(6):587-592

Irrigation with arsenic (As)‐rich water in agricultural soil may increase high levels of As in crops and cause food chain contamination. In this study, a greenhouse experiment was established using Spanish agricultural soil (Valladolid and Segovia provinces), that are extensively cultivated for carrot plant, to investigate the process of As uptake, bioaccumulation, and translocation of As from root to shoot and leaves in carrot plant. Arsenic concentrations in different organs of carrot plant, rhizosphere soil, and soil solutions were determined by hydride generation atomic absorption spectrometry (AAS). High concentrations of As in irrigation water, and the alkaline and sandy character of this soil enhanced As uptake in carrot plants indicating the potential health risk from consumption of carrots cultivated in these areas. Bioaccumulation of As into the leaves and roots increased with increase of As concentration in irrigation water. Both roots and leaves demonstrated a higher accumulation rate of As at an As concentration of 41 than 131 µg L^?1 in the soil solution. The ratios of As_root/As_leaves showed no statistically significant differences for the different irrigation treatments, and had an average value of 0.36 indicating the high magnitude of As translocation from roots to leaves in carrot plants. The leaves of carrots had a higher affinity for As than roots did. The correlation between As uptake by leaves or roots of carrots and the soluble As in rhizosphere soil did not demonstrate a linear or a plateau curve, indicating a slow but continuous constant As absorption which could be prolonged over time with high potential environmental risks.  相似文献   

Reconnaissance environmental magnetic study of urban soils, dust and leaves from Bogotá, Colombia     

Bertha Aguilar Reyes  Victoria Mejía  Avto Goguitchaichvili  Jaime Escobar  Germán Bayona  Francisco Bautista  Juan C. Morales  Thomas J. Ihl 《Studia Geophysica et Geodaetica》2013,57(4):741-754

Rock-magnetic investigations of environmental samples, such as soils, dust and leaves, can provide useful information on environmental stress. Aim of this paper is to report on the first magnetic survey carried out on environmental samples from Bogotá, Colombia, which is the fifth most populated city of Latin America. We studied three kinds of samples in order to evaluate their potential as pollution markers: soils, urban dust and leaves of the Sauco (Sambucus nigra) tree. Standard magnetic methods were used to analyze the three groups of samples, with special emphasis on leaves investigated here for the first time for environmental purposes. Samples were collected along two perpendicular transects in an area of the city presumably unpolluted, with two different systems of public transportation. Thermomagnetic curves obtained from soils and atmospheric dust show clearly defined ferrimagnetic phase (probably magnetite) as the main magnetic carrier. Curves of acquisition of isothermal remanent magnetization confirm the ferrimagnetic character of magnetic particles. Frequency-dependent magnetic susceptibility was found between 0 and 10%, suggesting less-important contribution of ultrafine super-paramagnetic magnetite. The apparent contradictory results between soils and the rest of samples may reflect different accumulation period for magnetic particles, being shorter for leaves and urban dust than for soils.  相似文献   

Role of shellfish hatchery as a reservoir of antimicrobial resistant bacteria     

Claudio D. Miranda  Rodrigo Rojas  Marcela Garrido  Julieta Geisse  Gerardo González 《Marine pollution bulletin》2013

The main aim of this study was to determine the occurrence of resistant bacteria in florfenicol-treated and untreated scallop larval cultures from a commercial hatchery and to characterize some selected florfenicol-resistant strains. Larval cultures from untreated and treated rearing tanks exhibited percentages of copiotrophic bacteria resistant to florfenicol ranging from 0.03% to 10.67% and 0.49–18.34%, respectively, whereas florfenicol resistance among oligotrophic bacteria varied from 1.44% to 35.50% and 3.62–95.71%, from untreated and treated larvae, respectively. Florfenicol resistant microbiota from reared scallop larvae mainly belonged to the Pseudomonas and Pseudoalteromonas genus and were mainly resistant to florfenicol, chloramphenicol, streptomycin and co-trimoxazole. This is the first study reporting antimicrobial resistant bacteria associated to a shellfish hatchery and the results suggest that a continuous surveillance of antimicrobial resistance even in absence of antibacterial therapy is urgently required to evaluate potential undesirable consequences on the surrounding environments.  相似文献   

10Be surface exposure dating reveals unexpected high deformation rates in the central Andean wedge interior     

Ezequiel García Morabito  Carla M. Terrizzano  Roland Zech  Marcela Yamin  Lorenz Wüthrich  Marcus Christl  Víctor A. Ramos  Negar Haghipour  Jos M. Corts 《地学学报》2021,33(1):30-45

Understanding deformation associated with active thrust wedges is essential to evaluate seismic hazards. In this study, we investigate the spatial distribution, timing, and rates of deformation across the central Andean backarc of Argentina, where deformation and shortening have been assumed to occur within a narrow wedge‐front zone. The combined results of our geomorphic mapping, topographic surveying, and ¹⁰Be exposure dating demonstrate that fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone but also occurs in the Andean wedge interior. There, internal structures with deformation rates of ca. 1.3 mm/year have been active during the last ~140 ka. Widely distributed deformation implies that seismic hazards may have been underestimated in the internal part of the Andean orogen.  相似文献   

Tracer hydrology of the data-scarce and heterogeneous Central American Isthmus     

Ricardo Sánchez-Murillo  Germain Esquivel-Hernández  José L. Corrales-Salazar  Laura Castro-Chacón  Ana M. Durán-Quesada  Manuel Guerrero-Hernández  Valeria Delgado  Javier Barberena  Katia Montenegro-Rayo  Heyddy Calderón  Carlos Chevez  Tania Peña-Paz  Saúl García-Santos  Pedro Ortiz-Roque  Yaneth Alvarado-Callejas  Laura Benegas  Antonio Hernández-Antonio  Marcela Matamoros-Ortega  Lucia Ortega  Stefan Terzer-Wassmuth 《水文研究》2020,34(11):2660-2675

Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial–temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water–groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the mid-summer drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by (a) depleted recharge in highland areas (72.3%), (b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m a.s.l. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.  相似文献   

Monte Carlo method applied to modeling copper transport in river sediments   总被引：2，自引：2，他引：0  

Marcela Z. Corazza  Taufik Abr?o  Fábio Grandis Lepri  Sonia M. N. Gimenez  Elisabeth Oliveira  Maria Josefa Santos 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(8):1063-1079

Monte Carlo simulation (MCS) methodology has been applied to explain the variability of parameters for pollutant transport and fate modeling. In this study, the MCS method was used to evaluate the transport and fate of copper in the sediment of the Tibagi River sub-basin tributaries, Southern Brazil. The statistical distribution of the variables was described by a dataset obtained for copper concentration using sequential extraction, organic matter (OM) amount, and pH. The proposed stochastic spatial model for the copper transport in the river sediment was discussed and implemented by the MCS technique using the MatLab 7.3? mathematical software tool. In order to test some hypotheses, the sediment and the water column in the river ecosystem were considered as compartments. The proposed stochastic spatial model makes it possible to predict copper mobility and associated risks as a function of the organic matter input into aquatic systems. The metal mobility can increase with the OM posing a rising environmental risk.  相似文献